COCENSYS INC
10-Q, 1997-08-06
PHARMACEUTICAL PREPARATIONS
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                                 UNITED STATES
                      SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, DC  20549
                                       
                                   FORM 10-Q

(Mark One)

[X]  QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15 (d) OF THE SECURITIES
     EXCHANGE ACT OF 1934
     For the quarterly period ended June 30, 1997

                                      OR
                                       
[ ]  TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE  SECURITIES
     EXCHANGE ACT OF 1934
     For the transition period from ________ to ________

                        Commission File Number 0-20954


                                COCENSYS, INC.
          (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)
                                       
                                       
                DELAWARE                        33-0538836
(STATE OR OTHER JURISDICTION OF    (I.R.S. EMPLOYER IDENTIFICATION NO.)
INCORPORATION OR ORGANIZATION)


                  213 TECHNOLOGY DRIVE, IRVINE, CA  92718
        (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES, INCLUDING ZIP CODE)
                                       
                               (714) 753-6100
            (REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE)
                                       
                                       
Indicate by check mark whether the registrant (1) has filed all reports 
required to be filed by Section 13 or 15 (d) of the Securities Exchange Act 
of 1934 during the preceding 12 months (or for such shorter period that the 
registrant was required to file such reports), and (2) has been subject to 
such filing requirements for the past 90 days.

                   Yes    X       No
                       -------       --------

Indicate the number of shares outstanding of each of the issuer's classes of 
common stock, as of the latest practicable date.

             $.001 PAR VALUE                     22,661,489
          (CLASS OF COMMON STOCK)       (OUTSTANDING AT JULY 31, 1997)


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<PAGE>


                                COCENSYS, INC.
                         (A development stage company)
                                       
                               TABLE OF CONTENTS
                                       
                                                                   PAGE NUMBER
                                                                   -----------
PART I.  FINANCIAL INFORMATION
     
         ITEM 1. FINANCIAL STATEMENTS.
     
                 Condensed Balance Sheets as of June 30, 1997
                 and December 31, 1996                                    3
    
                 Condensed Statements of Operations for the 
                 three-month and six-month periods ended 
                 June 30, 1997 and 1996 and the period from 
                 inception (February 15, 1989) through June 30, 1997      4
    
                 Condensed Statements of Cash Flows for the 
                 three-month and six-month periods ended 
                 June 30, 1997 and 1996 and the period from 
                 inception (February 15, 1989) through June 30, 1997      5
    
                 Notes to Condensed Financial Statements                  6
    
    
         ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
                 CONDITION AND RESULTS OF OPERATIONS.                    10
    
    
PART II. OTHER INFORMATION

         ITEM 2. CHANGES IN SECURITIES.                                  14

         ITEM 4. SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS.    14
    
         ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K.                       14


SIGNATURES                                                               16


                                       2
<PAGE>

                                COCENSYS, INC.
                         (A development stage company)
                                       
                           CONDENSED BALANCE SHEETS
              (In thousands, except share and par value amounts)
                                       
<TABLE>
<CAPTION>
                                                         JUNE 30,      DECEMBER 31,
                                                           1997           1996
                                                       -----------     ------------
                                                       (Unaudited)
<S>                                                    <C>             <C>
ASSETS
Current assets:
 Cash and cash equivalents                               $  2,192       $  1,050
 Short-term investments                                    15,180         16,949
 Receivables from corporate partners                          657            659
 Other current assets                                         810            556
                                                         --------       --------
TOTAL CURRENT ASSETS                                       18,839         19,214

Property and equipment, net                                 2,494          2,685
Notes receivable from officers                                279            126
Other assets, net                                              26             26
                                                         --------       --------
                                                         $ 21,638       $ 22,051
                                                         --------       --------
                                                         --------       --------

LIABILITIES & STOCKHOLDERS' EQUITY
Current liabilities:
 Accounts payable                                          $  764       $  1,437
 Other accrued liabilities                                  2,828          2,556
 Advances from corporate partners                             151            446
 Capital lease obligation - current portion                   559            341
                                                         --------       --------
TOTAL CURRENT LIABILITIES                                   4,302          4,780

Capital lease obligation, less current portion                227            284
Other liabilities                                              38             40

Commitments and contingencies

Stockholders' equity:
 Preferred stock - $.001 par value,
  5,000,000 shares authorized; 100,000 shares of
  Series B convertible issued and outstanding
  at June 30, 1997 and December 31, 1996; 100,000 shares 
  of Series C convertible issued and outstanding at
  June 30, 1997                                            12,000          7,000
 Common stock - $.001 par value,
  75,000,000 shares authorized; 22,661,489 shares
  issued and outstanding at June 30, 1997 and
  22,083,346 at December 31, 1996                          96,076         93,986
 Deficit accumulated during the development stage         (90,468)       (83,162)
 Deferred compensation                                       (562)          (905)
 Unrealized gain (loss) on investments                         25             28
                                                         --------       --------
TOTAL STOCKHOLDERS' EQUITY                                 17,071         16,947
                                                         --------       --------
                                                         $ 21,638       $ 22,051
                                                         --------       --------
                                                         --------       --------
</TABLE>

                           See accompanying notes.

                                      3
<PAGE>

                                COCENSYS, INC.
                         (A development stage company)
                                       
                      CONDENSED STATEMENTS OF OPERATIONS
                   (In thousands, except per share amounts)
                                  (Unaudited)
<TABLE>
<CAPTION>
                                                                                                                   
                                                                                                                   PERIOD FROM
                                                                                                                    INCEPTION
                                                             THREE MONTHS ENDED            SIX MONTHS ENDED        (FEBRUARY 15,
                                                                   JUNE 30,                     JUNE 30,             1989) TO
                                                         -----------------------       -----------------------       JUNE 30,
                                                            1997           1996           1997           1996          1997
REVENUES                                                 --------       --------       --------       --------     ------------
<S>                                                      <C>            <C>            <C>            <C>          <C>
  Co-promotion revenues from corporate partners          $  1,185       $  3,213       $  2,308       $  4,011      $  29,209
  Co-development revenues from corporate partners           6,247          3,716          6,949          4,549         14,992
                                                         --------       --------       --------       --------      ---------
Total revenues                                              7,432          6,929          9,257          8,560         44,201

OPERATING EXPENSES
  Research and development                                  5,984          4,961         11,416          9,784         79,588
  Marketing, general and administrative                     2,825          2,926          5,504          5,589         43,134
  Acquired research and development                             -              -              -              -         14,879
                                                         --------       --------       --------       --------      ---------
Total operating expenses                                    8,809          7,887         16,920         15,373        137,601
                                                         --------       --------       --------       --------      ---------
OPERATING LOSS                                             (1,377)          (958)        (7,663)        (6,813)       (93,400)

Interest income                                               189            357            408            629          3,503
Interest expense                                              (37)           (28)           (51)           (58)          (571)
                                                         --------       --------       --------       --------      ---------

NET LOSS                                                 $ (1,225)      $   (629)      $ (7,306)      $ (6,242)     $ (90,468)
                                                         --------       --------       --------       --------      ---------
                                                         --------       --------       --------       --------      ---------

Net loss per share                                       $  (0.05)      $  (0.03)      $  (0.33)      $  (0.29)
                                                         --------       --------       --------       --------     
                                                         --------       --------       --------       --------     

Shares used in computing net loss per share                22,519         21,917         22,391         21,555
                                                         --------       --------       --------       --------     
                                                         --------       --------       --------       --------     
</TABLE>


                             See accompanying notes.

                                        4

<PAGE>
                                  COCENSYS, INC.
                           (A development stage company)
                                                                 
                         CONDENSED STATEMENTS OF CASH FLOWS
                                  (In thousands)
                                    (Unaudited)
<TABLE>
<CAPTION>
                                                                                     PERIOD FROM
                                                                                      INCEPTION
                                                           SIX MONTHS ENDED          (FEBRUARY 15,
                                                                JUNE 30,               1989) TO
                                                        -------------------------      JUNE 30,
                                                           1997           1996          1997
                                                        ----------     ----------    ------------
<S>                                                     <C>            <C>           <C>
OPERATING ACTIVITIES
Net loss                                                $  (7,306)     $  (6,242)    $  (90,468)

Adjustments to reconcile net loss to net cash used 
  in operating activities:
  Depreciation and amortization                               530          1,025          6,419
  Amortization of deferred compensation                       142            374          3,480
  Issuance of stock and warrants for services                   -              -          1,917
  Loss on sale of fixed assets                                 12              -             38
  Acquired research and development                             -              -         12,279
  Increase in other current assets                           (254)          (196)          (882)
  Decrease (increase) in receivable from corporate 
    partner                                                     2              -           (657)
  Increase (decrease) in advances from corporate 
    partners                                                 (295)           997            151
  Increase (decrease) in accounts payable and other
    accrued liabilities                                      (403)           (89)         3,354
                                                        ---------      ---------     ----------
NET CASH USED IN OPERATING ACTIVITIES                      (7,572)        (4,131)       (64,369)
                                                        ---------      ---------     ----------

INVESTING ACTIVITIES
Decrease (increase) in short-term investments               1,766         (8,560)       (15,156)
Purchase of property and equipment                           (351)          (475)        (5,976)
Increase in other assets and notes receivable from 
  officers                                                   (153)           (89)          (461)
Cash received on sale of fixed assets                           -              -             19
Increase in deferred sales organization costs                   -              -         (1,571)
Increase in deferred patent costs                               -              -           (904)
Acquisition of Acea Pharmaceuticals, net of cash 
  acquired                                                      -              -            (62)
                                                        ---------      ---------     ----------
NET CASH PROVIDED BY (USED IN) INVESTING ACTIVITIES         1,262         (9,124)       (24,111)
                                                        ---------      ---------     ----------

FINANCING ACTIVITIES
Net cash proceeds from issuance of common stock             2,291         14,840         61,076
Net cash proceeds from issuance of preferred stock          5,000          7,000         28,381
Proceeds from sale/leaseback of fixed assets and notes
 payable                                                      529            535          4,762
Payments on capital lease obligations and notes payable     (368)          (553)         (3,547)
                                                        ---------      ---------     ----------
NET CASH PROVIDED BY FINANCING ACTIVITIES                   7,452         21,822         90,672
                                                        ---------      ---------     ----------

NET INCREASE IN CASH AND CASH EQUIVALENTS                   1,142          8,657          2,192
CASH AND CASH EQUIVALENTS AT BEGINNING OF PERIOD            1,050          6,895              -
                                                        ---------      ---------     ----------
CASH AND CASH EQUIVALENTS AT END OF PERIOD               $  2,192      $  15,462       $  2,192
                                                        ---------      ---------     ----------
                                                        ---------      ---------     ----------

SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION
Cash paid for interest                                      $  39          $  58         $  793
                                                        ---------      ---------     ----------
                                                        ---------      ---------     ----------
</TABLE>
                                                                 
                          See accompanying notes.

                                     5

<PAGE>

                                COCENSYS, INC.
                         (A development stage company)
                                       
                    NOTES TO CONDENSED FINANCIAL STATEMENTS
                                       
                                 JUNE 30, 1997
                                  (UNAUDITED)
                                       
                                       
1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES

   BASIS OF PRESENTATION

   The interim financial information for the three and six-month periods 
   ended June 30, 1997 and 1996 is unaudited but includes all adjustments 
   (consisting only of normal recurring entries) which the Company's 
   management believes to be necessary for the fair presentation of the 
   financial position, results of operations and cash flows for the periods 
   presented.  The accompanying interim financial statements should be read 
   in conjunction with the financial statements and related notes included in 
   the Company's 1996 Annual Report on Form 10-K for the year ended December 
   31, 1996.  Certain information and footnote disclosures normally included 
   in financial statements prepared in accordance with generally accepted 
   accounting principles have been condensed or omitted pursuant to 
   Securities and Exchange Commission rules and regulations.  Interim results 
   of operations for the three-month and six-month periods ended June 30, 
   1997, are not necessarily indicative of operating results to be expected 
   for the full year.

   REVENUE AND EXPENSE RECOGNITION

   See Notes 2 through 6 for revenue recognition policies related to 
   co-promotion and co-development revenues from corporate partners. The 
   initial costs incurred in establishing the sales and marketing 
   organization were deferred until initiation of the Company's sales efforts 
   on August 1, 1994. Such costs were amortized over the contract term 
   (through December 31, 1996) of the Company's Promotion Agreement with 
   Novartis (formerly Ciba-Geigy Corporation).

   NET LOSS PER SHARE

   Net loss per share is computed using the weighted average number of shares 
   of common stock outstanding during the periods.  Common stock equivalents 
   from stock options and warrants are excluded from the calculation as their 
   effect would be antidilutive.

   RECLASSIFICATIONS

   Certain reclassifications have been made to the 1996 financial statements 
   to conform to the 1997 presentation.

                                      6
<PAGE>
                                COCENSYS, INC.
                         (A development stage company)
                                       
                    NOTES TO CONDENSED FINANCIAL STATEMENTS
                                       

2. MARKETING AND DEVELOPMENT COLLABORATION WITH WARNER-LAMBERT COMPANY

   In October 1995, the Company entered into a collaboration with 
   Warner-Lambert Company and its Parke-Davis division to develop and market 
   therapeutic drugs for the treatment of certain CNS disorders.  This 
   arrangement consists of the Research, Development and Marketing 
   Collaboration Agreement (the "Warner Collaboration Agreement"), for the 
   worldwide development and commercialization of a new class of neurological 
   and psychiatric drugs, termed subtype selective NMDA receptor antagonists 
   ("SSNRAs"), and the Parke-Davis Promotion Agreement, pursuant to which the 
   Company co-promoted Parke-Davis' CNS drug, Cognex-Registered Trademark-, 
   to United States neurologists for the treatment of Alzheimer's disease.

   Under the Warner Collaboration Agreement, both companies are sharing 
   technology and resources to develop SSNRA candidates.  The parties are 
   obligated to make specified contributions to development costs with 
   respect to any development candidates.  Promotion costs of, and profits 
   from any products developed under the agreement will be shared equally in 
   the United States and Japan.  Warner-Lambert will have the exclusive right 
   to develop and market any product, at its own cost, for markets outside 
   the United States and Japan, subject to a specified royalty payment to the 
   Company. Warner-Lambert is obligated to pay its specified portion of the 
   development costs and to make certain milestone payments, upon achievement 
   of certain clinical development and regulatory milestones, for each 
   development compound.  Payments received under the Warner Collaboration 
   Agreement will be recognized as co-development revenues by the Company.

   Pursuant to the Warner Collaboration Agreement, Warner-Lambert purchased 
   $2.0 million of CoCensys common stock in October 1995 and an additional 
   $2.0 million of CoCensys common stock in March 1997.

   The original Parke-Davis Promotion Agreement, entered into in October 
   1995, was terminated on December 31, 1996, when a revised promotion 
   agreement relating to Cognex took effect. Under the original Parke-Davis 
   Promotion Agreement for Cognex, the Company realized co-promotion revenues 
   from its share of sales of Cognex above certain baseline levels specified 
   in the contract.  Under the revised Parke-Davis Promotion Agreement for 
   Cognex, the Company realized co-promotion revenues based upon the number 
   of prescriptions for Cognex written by certain targeted neurologists and 
   other doctors during each quarter, with a specified minimum payment.  The 
   revised Cognex agreement was terminated in June 1997.

   In July 1997, the Company entered into a new Parke-Davis Promotion 
   Agreement, pursuant to which the Company will co-promote 
   Zarontin-Registered Trademark-, Parke-Davis' drug for pediatric epilepsy.  
   Under the terms of the Zarontin agreement, the Company will realize 
   co-promotion revenue on the basis of the number of prescriptions for 
   Zarontin written each quarter over a specified baseline.


                                      7
<PAGE>


                                COCENSYS, INC.
                         (A development stage company)
                                       
                    NOTES TO CONDENSED FINANCIAL STATEMENTS
                                       

3. PROMOTION AGREEMENT WITH SOMERSET PHARMACEUTICALS, INC.

   In January 1996, the Company and Somerset Pharmaceuticals, Inc. 
   ("Somerset") entered into the Somerset Promotion Agreement, pursuant to 
   which the Company promotes Somerset's drug Eldepryl-Registered Trademark- 
   to neurologists in the United States for the treatment of Parkinson's 
   disease.  Effective January 1, 1997, the initial agreement was superceded 
   by the 1997 Somerset Promotion Agreement which is subject to certain 
   provisions for early termination and renewal.  Under the 1997 Somerset 
   Promotion Agreement, CoCensys has the exclusive right to detail Eldepryl 
   to certain neurologists and other physicians in the United States.  Under 
   the 1997 Somerset Promotion Agreement, CoCensys is compensated based upon 
   the number of details undertaken and gross sales of Eldepryl.  
   Compensation paid to CoCensys is subject to adjustment in the event of 
   governmental or other third-party actions that may materially affect it.  
   To finance a portion of its sales force to promote Eldepryl, CoCensys 
   receives quarterly advances from Somerset, which are subject to repayment 
   on a pro rata basis if specified numbers of details are not undertaken by 
   the Company on behalf of Somerset.

4. DEVELOPMENT AND COMMERCIALIZATION AGREEMENT WITH G.D. SEARLE & CO.

   In May 1996, the Company entered into an agreement with G.D. Searle & Co. 
   ("Searle") to co-develop and co-promote the Company's lead compound for 
   the treatment of insomnia along with its back-up compounds.  Pursuant to 
   the agreement, Searle paid a $3.0 million license fee and purchased 
   100,000 shares of the Company's Series B Convertible Preferred Stock for 
   $7.0 million.  The license fee was recognized as co-development revenue in 
   1996. The preferred stock is convertible to common stock on May 17, 1998, 
   or earlier at the Company's discretion.  The number of shares issuable 
   upon conversion shall be equal to $7.0 million divided by the then current 
   common stock price (subject to certain minimum and maximum limits).

   Under the agreement, both companies are obligated to pay a portion of the 
   development costs of the compound and its back-up compounds.  In addition, 
   the Company will receive nonrefundable milestone payments upon the 
   occurrence of certain events in the development of the compound.  The 
   parties will co-promote any products derived from the collaboration in the 
   United States, while Searle will have the right to develop, register and 
   market the products in the rest of the world, subject to specified royalty 
   payments.

5. MARKETING AND DEVELOPMENT COLLABORATION WITH NOVARTIS PHARMA, A.G.

   In May 1994, the Company entered into a marketing and development 
   collaboration with Novartis Novartis Pharma, A.G. (formerly Ciba-Geigy 
   Limited) for the co-promotion by the Company of certain Novartis products 
   and the development and commercialization of ACEA 1021, a compound being 
   developed by the Company.  This collaboration consisted of the Novartis 
   Promotion Agreement and the Novartis Research and Development Agreement.

   Pursuant to the Novartis Promotion Agreement, CoCensys established a sales 
   force to co-promote and market certain Novartis products in the United 
   States initially to psychiatrists.  The agreement 

                                      8
<PAGE>
                                COCENSYS, INC.
                         (A development stage company)
                                       
                    NOTES TO CONDENSED FINANCIAL STATEMENTS
                                       

   provided for the advance of funds to the Company to cover a portion of the 
   expenses incurred by the CoCensys sales force in promoting the Novartis 
   products.  CoCensys realized co-promotion revenues from its share of sales 
   of Novartis products above certain baseline levels specified in the 
   contract.  The Novartis Promotion Agreement terminated at the end of 1996.

   In connection with the Novartis Research and Development Agreement, 
   Novartis purchased $7.0 million of CoCensys common stock and agreed to 
   make certain nonrefundable milestone payments in connection with specified 
   events in the course of the development of ACEA 1021.  Novartis has 
   advised the Company that it will not continue the development of ACEA 
   1021.  The agreement will terminate in October 1997.  While the Company is 
   actively looking for a new partner to develop ACEA 1021, there can be no 
   assurance that the Company will be able to secure another partner to 
   continue the development of this compound.

6. DEVELOPMENT AND COMMERCIALIZATION AGREEMENT WITH WYETH-AYERST LABORATORIES

   In May 1997, the Company entered into a development and commercialization 
   agreement for Co 2-6749, its lead anxiolytic compound, with Wyeth-Ayerst 
   Laboratories, the pharmaceutical division of American Home Products 
   Corporation ("AHP"). Under the terms of the agreement, Wyeth-Ayerst made 
   upfront payments to CoCensys of $5.0 million in licensing fees and AHP 
   paid $5.0 million to purchase convertible preferred stock.  Additionally, 
   CoCensys will receive specified milestone payments dependent upon the 
   achievement of key development events and $3.0 million per year for up to 
   three years to identify back-up compounds.  Payments due to CoCensys for 
   work performed identifying back-up compounds are due quarterly, beginning 
   in May 1997. Wyeth-Ayerst will be responsible for the development of Co 
   2-6749.  The Company and Wyeth-Ayerst will co-promote any resulting 
   product in certain market segments in the United States, while 
   Wyeth-Ayerst will have rights to develop, register and market any drugs 
   derived from the collaboration in the rest of the world, subject to 
   royalty payments.  The preferred stock is convertible into common stock 
   after May 12, 1999, into a number of shares of common stock equal to $5.0 
   million divided by the conversion price, which will be determined pursuant 
   to a formula based on the market price of the common stock at the time of 
   conversion (subject to certain minimum and maximum limits).
  


                                      9
<PAGE>

ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL
        CONDITION AND RESULTS OF OPERATIONS

  EXCEPT FOR THE HISTORICAL INFORMATION CONTAINED HEREIN, THE FOLLOWING
  DISCUSSION CONTAINS FORWARD-LOOKING STATEMENTS THAT INVOLVE RISKS AND
  UNCERTAINTIES.  THE COMPANY'S ACTUAL RESULTS COULD DIFFER MATERIALLY.
  FACTORS THAT COULD CAUSE OR CONTRIBUTE TO SUCH DIFFERENCES INCLUDE, BUT ARE
  NOT LIMITED TO, THOSE DISCUSSED BELOW AND IN THE COMPANY'S 1996 ANNUAL REPORT
  ON FORM 10-K.

  OVERVIEW
     
  CoCensys, Inc. is a biopharmaceutical company dedicated to the discovery,
  development, marketing and sales of small molecule drugs to treat
  neurological and psychiatric disorders.  The Company's product discovery and
  development programs are focused on the exploration of novel receptors and
  enzymes and their ligands and inhibitors through three technology platforms:
  GABA receptor enhancers or Epalons; glutamate antagonists; and ICE-like
  protease inhibitors.

  The Company's lead Epalon compound, CCD 1042 (ganaxolone), an anticonvulsant
  and anti-migraine compound, is in separate Phase II clinical trials for
  pediatric epilepsy, adult epilepsy and migraine. The Company anticipates that
  CCD 3693, its lead compound for the treatment of insomnia, will enter Phase I
  trials in the third quarter of 1997.

  Since its inception in February 1989, the Company has devoted substantially
  all of its resources to the discovery and development of neuropharmaceutical
  products for the treatment of disorders affecting the central nervous system.
  The Company has incurred losses since inception and expects losses to
  continue for the foreseeable future, primarily due to the expansion of
  programs for research and development.  Operating results are expected to
  fluctuate as a result of uncertainty in the timing and amount of revenues to
  be earned from product co-promotion and co-development activities and from
  achievement of research and development milestones, and uncertainty in the
  timing and amount of expenses for product development, including clinical
  trials.  As of June 30, 1997, the Company's accumulated deficit was
  approximately $90.5 million.

  RESULTS OF OPERATIONS

  The Company recognized $1.2 and $2.3 million in co-promotion revenues for the
  three and six-month periods ended June 30, 1997, respectively, compared to
  $3.2 and $4.0 million during the same periods in 1996.  The decreases in both
  the three and six-month periods compared to the same periods a year earlier
  is due primarily to a nonrecurring adjustment of $2.3 million, relating to
  settlement of co-promotion activities with Novartis Pharma A.G. ("Novartis"),
  that was recorded in the second quarter of fiscal 1996.

  The Company recognized $6.2 and $6.9 million in co-development revenues for
  the three and six-month periods ended June 30, 1997, respectively, compared
  to $3.7 and $4.5 million for the comparable periods of 1996.  The increases
  in both the three and six-month periods of the current year are primarily due
  to recognition of $5.7 of co-development revenue under the Wyeth-Ayerst


                                      10
<PAGE>

  development and commercialization agreement that was signed in May of 1997.
  In the second quarter of fiscal 1996, the Company recognized $3.0 million of
  co-development revenue related to the G.D. Searle agreement.

  Research and development ("R&D") expenses increased to $6.0 and $11.4 million
  for the three and six-month periods ended June 30, 1997, respectively, from
  $4.9 and $9.8 million in the comparable periods of the prior year.  These
  increases resulted primarily from higher product development costs incurred
  to support Phase II clinical trials of CCD 1042 in both migraine and epilepsy
  and pre-clinical development of CCD 3693, partially offset by lower product
  development costs associated with the ACEA 1021 program.  Clinical
  development of ACEA 1021 was suspended in April 1997 following the decision
  of Novartis, the Company's development partner, not to continue participation
  in the development of ACEA 1021.  The Company does not intend to resume
  clinical development of ACEA 1021 until it secures another partner.  There
  can be no assurance that the Company will be able to secure another partner
  to continue the clinical development of ACEA 1021.

  Marketing, general and administrative expense decreased to $2.8 and $5.5
  million for the three and six-month periods ended June 30, 1997,
  respectively, from $2.9 and $5.6 million in the same periods of the prior
  year.  The decreases in the three and six-month periods of the current year
  in comparison to the same periods in the prior year are primarily
  attributable to reductions in certain promotional marketing expenses,
  partially offset by increases in salaries and other general corporate
  expenses.

  Interest income decreased to $.2 and $.4 million for the three and six-month
  periods ended June 30, 1997, respectively, from $.4 and $.6 million in the
  same periods of the prior year.  The decrease was due to lower average levels
  of cash and short-term investment balances in the current year.

  LIQUIDITY AND CAPITAL RESOURCES

  From its inception in February 1989 through June 30, 1997, the Company has
  financed its operations primarily through private and public offerings of
  its equity securities, raising net proceeds of approximately $89.5 million
  through sales of these securities.  As of June 30, 1997, the Company's
  balance of cash, cash equivalents and short-term investments totaled $17.4
  million, compared to $18.0 million at December 31, 1996.

  As of June 30, 1997, the Company had invested $6.0 million in leasehold
  improvements, laboratory and computer equipment and office furnishings and
  equipment since inception.  The Company has financed $3.3 million of these
  capital additions through capital lease lines.  In addition, the Company
  leases its laboratory and office facilities under operating leases.
  Additional equipment will be needed as the Company increases its research and
  development activities.  The Company has no material commitments for the
  acquisition of property and equipment.

  Pursuant to the Parke-Davis Promotion Agreement, the Company promoted Parke-
  Davis' CNS drug, Cognex-Registered Trademark-, to neurologists in the 
  United States.  Funds were prepaid to the Company quarterly to cover the 
  training and operating expenses incurred by the Company's sales force in 
  promoting Cognex.  This agreement was terminated in June 1997.  In July 
  1997, the Company entered into a 


                                      11
<PAGE>

  new agreement with Parke-Davis to co-promote Zarontin-Registered Trademark-,
  Parke-Davis' drug for pediatric epilepsy.  Under the terms of this agreement,
  the Company will be compensated based on the number of prescriptions written
  over a specified baseline.
  
  Pursuant to the Warner Collaboration Agreement, Warner-Lambert is obligated
  to make certain milestone payments for each compound selected for
  development, as well as pay for its share of development costs.  Also
  pursuant to this contract, Warner-Lambert purchased $2.0 million of CoCensys
  common stock in October 1995 and an additional $2.0 million of CoCensys
  common stock in March 1997.

  Pursuant to the 1997 Somerset Promotion Agreement, the Company promotes
  Somerset's drug Eldepryl-Registered Trademark- to certain neurologists 
  and other physicians in the United States.  Funds are advanced to the 
  Company quarterly to cover a portion of the training and operating 
  expenses incurred by the Company's sales force in promoting Eldepryl.

  Pursuant to the 1997 Wyeth-Ayerst Development and Commercialization
  Agreement, Wyeth-Ayerst is obligated pay all development costs related to Co
  2-6749, as well as make milestone payments upon the occurrence of certain
  agreed upon events.  Furthermore, Wyeth-Ayerst is required to pay the Company
  $3.0 million per year for up to three years to identify back-up compounds.
  
  CoCensys' operations to date have consumed substantial amounts of cash.  The
  negative cash flow from operations is expected to continue and will likely
  increase over the foreseeable future, subject to the Company's ability to
  mitigate such negative cash flows with revenues, if any, derived from the
  sale of products from current and potential future marketing collaborations.
  The Company anticipates that its existing capital resources, including
  funding expected to be available through current partner collaborations
  (including milestone payments and co-promotion revenues), will be adequate to
  satisfy its capital needs for at least the next 12 months.  There can be no
  assurance that milestone-based payments or co-promotion revenues will be
  sufficient to meet the Company's capital requirements.  The Company will need
  to obtain substantial additional funds to conduct the costly and
  time-consuming research, preclinical development and clinical trials
  necessary to bring its products to market.  The Company intends to seek
  additional funding through additional research and development collaborations
  with suitable corporate partners, through additional marketing collaborations
  to increase revenues generated from sales of products and/or through public
  or private financing.  There can be no assurance that additional financings
  or suitable collaborations will be available on favorable terms, if at all.
  Insufficient funds may require the Company to delay, scale back or eliminate
  some or all of its research and product development programs or to license
  third parties to commercialize products or technologies that the Company
  would otherwise seek to develop itself.

  The Company's future capital requirements will depend on many factors,
  including the progress of the Company's research and development programs,
  the level of co-promotion revenues, the scope and results of preclinical
  testing and clinical trials, the time and costs involved in obtaining
  regulatory approvals, the rate of technological advances, determinations as
  to the commercial potential of the Company's products under development, the
  status of competitive products, the expansion of sales and marketing
  capabilities, the establishment of third-party manufacturing arrangements and
  the establishment of additional collaborative relationships.
  


                                      12
<PAGE>
  
  ADDITIONAL RISKS
  
  In addition to those discussed above, the Company is subject to the following
  risks:
  
  The Company's products are in an early stage of development and face a high
  degree of technological, regulatory and competitive risks.  Drug discovery
  and development are capital intensive activities, and there can be no
  assurance the Company will be able to raise the additional capital necessary
  to develop and commercialize products.  The Company's strategy for the
  development, clinical testing and commercialization of its products includes
  entering into various collaborations with corporate partners, licensors,
  licensees and others.  There can be no assurance that the Company will be
  able to negotiate further collaborative arrangements on acceptable terms, if
  at all, or that the current collaborative efforts will be successful.  Human
  clinical trials require considerable time and funding, and results from any
  stage of testing may not predict results of later stages.  In addition, if
  results of any clinical trial fail to meet the Company's requirements, the
  study plan for such compound may be adjusted or another compound may be
  substituted, either of which may result in delays in future clinical studies.
  Unfavorable clinical trials could result in cancellation of future clinical
  studies.  Inherent in the fact that CoCensys is an early stage
  biopharmaceutical company are a range of  additional risks, including those
  associated with obtaining and enforcing patents and protecting proprietary
  technology and the risk of regulatory change, among others.
  
  The securities markets have from time to time experienced significant price
  and volume fluctuations that may be unrelated to the operating performance of
  particular companies.  The market prices of the common stock of many publicly
  traded biopharmaceutical companies have in the past been, and can in the
  future be expected to be, especially volatile due to various external
  factors, including but not limited to, announcements of technological
  innovations or new products by the Company or its competitors, developments
  or disputes concerning patents or proprietary rights, publicity regarding
  actual or potential results relating to products under development,
  regulatory developments in both the United States and foreign countries and
  public concern as to the safety of biotechnology products.
  


                                      13
<PAGE>

                                       
PART II.  OTHER INFORMATION

  ITEM 2.   CHANGES IN SECURITIES

  On May 12, 1997, the Company sold 100,000 unregistered shares of Series C
  Convertible Preferred Stock (the "Preferred Stock") to American Home Products
  Corporation for an aggregate purchase price of $5,000,000.  The Preferred
  Stock is convertible at the option of the holder at any time after May 11,
  1999 at a Conversion Price determined pursuant to a formula based on the
  market price of the Common Stock at the time of conversion, subject to a
  minimum price of $4.37 and a maximum price of $7.76.  The transaction was
  exempt from registration under the Securities Act of 1933, as amended,
  pursuant to Section 4(2) thereof, as a transaction not involving any public
  offering.

  ITEM 4.   SUBMISSION OF MATTERS TO A VOTE OF SECURITY HOLDERS

  The Company held an Annual Meeting of Stockholders on June 25, 1997.
  
  The stockholders elected the Board's nominees as Class II directors by the
  votes indicated:
  
       Nominee                   Votes in Favor    Votes Withheld
       -------                   --------------    --------------
       F. Richard Nichol, Ph.D.    17,079,020         796,242
       Timothy J. Rink, M.D.       17,092,626         782,636
  
  The amendment to the Company's 1992 Non-Employee Directors' Stock Option Plan
  was ratified with 16,961,900 votes in favor, 836,422 against and 76,940
  abstentions.
  
  The Company's 1996 Equity Incentive Plan was approved by a vote of 10,530,958
  in favor, 2,474,023 against, 86,195 abstentions and 4,784,086 broker non-
  votes.
  
  The selection of Ernst & Young, LLP as the Company's independent auditors was
  ratified with 17,810,357 votes in favor, 28,550 against and 36,355
  abstentions.

  ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K

     (a)  Exhibits

          3(i).1   Amended and Restated Certificate of  Incorporation of 
                   the Company.
          3(i).2   Certificate of Designation of Series A Junior Participating
                   Preferred Stock of the Company.
          3(i).3   Certificate of Powers, Designation, Preferences, Rights 
                   and Limitations of Series B Convertible Preferred Stock 
                   of the Company.
          3(i).4   Certificate of Amendment of Amended and Restated 
                   Certificate of Incorporation of the Company.
          3(i).5   Certificate of Powers, Designation, Preferences, Rights 
                   and Limitations of 


                                      14
<PAGE>

                   Series C Convertible Preferred Stock of the Company.
            10.1*  1997 Promotion Agreement, effective April 7, 1997, between 
                   Somerset Pharmaceuticals, Inc. and the Company.
            10.2*  Development and Commercialization Agreement (No.1), dated 
                   May 12, 1997, between Wyeth-Ayerst Laboratories and the 
                   Company ("Wyeth-Ayerst Agreement No.1").
            10.3*  Development and Commercialization Agreement (No.2), 
                   dated May 12, 1997, between Wyeth-Ayerst Laboratories and 
                   the Company.
            10.4   Preferred Stock Purchase Agreement, dated May 12, 1997, 
                   between American Home Products, Inc. and the Company 
                   (included as Exhibit F to Wyeth-Ayerst Agreement No. 1)
            27.1   Financial Data Schedule

            * Confidential treatment requested.

      (b)   Reports on Form 8-K

            (i)   The Company filed a Form 8-K on June 17, 1997, reporting 
                  under Item 5 that the Company and the Parke-Davis Division 
                  of Warner-Lambert Company have agreed to terminate the 
                  Cognex Promotion Agreement.

            (ii)  The Company filed a Form 8-K on May 2, 1997, reporting 
                  under Item 5 that Novartis Pharma A.G. has decided not to 
                  participate further in the development of ACEA 1021, 
                  CoCensys' compound for the treatment of stroke and 
                  traumatic brain injury.

                                      15
<PAGE>

                                  SIGNATURES
                                       
                                       
                                       

Pursuant to the requirements of the Securities and Exchange Act of 1934, the
registrant has duly caused this report to be signed in its behalf by the
undersigned thereunto duly authorized.





                              CoCensys, Inc.






Date:  August 5, 1997             By:         /s/ Peter E. Jansen
                                      -------------------------------------
                                                 Peter E. Jansen
                                             Chief Financial Officer
                                        (PRINCIPAL FINANCIAL AND ACCOUNTING
                                                  OFFICER)



                                      16

<PAGE>

                                                           Exhibit 3(i).1

                  AMENDED AND RESTATED CERTIFICATE OF INCORPORATION
                                          OF
                                    COCENSYS, INC.
                                           
                                      I.

                                           
    The name of this corporation is CoCensys, Inc.

                                      II.

    The address of the registered office of the corporation in the State of
Delaware is 32 Loockerman Square, Suite L-100, City of Dover, County of Kent,
and the name of the registered agent of the corporation in the State of Delaware
at such address is the Prentice Hall Corporation System.  

                                      III.

    The purpose of this corporation is to engage in any lawful act or activity
for which a corporation may be organized under the General Corporation Law of
the State of Delaware.

                                      IV.

    A.   This corporation is authorized to issue two classes of stock to be
designated, respectively, "Common Stock" and "Preferred Stock."  The total
number of shares which the corporation is authorized to issue is thirty-five
million (35,000,000) shares.  Thirty million (30,000,000) shares shall be Common
Stock, each having a par value of one-tenth of One Cent ($.001).  Five million
(5,000,000) shares shall be Preferred Stock, each having a par value of
one-tenth of One Cent ($.001).

    B.   The Preferred Stock may be issued from time to time in one or more
series.  The Board of Directors is hereby authorized, by filing a certificate
pursuant to the Delaware General Corporation Law, to fix or alter from time to
time the designation, powers, preferences and rights of the shares of each such
series and the qualifications, limitations or restrictions thereof, including
without limitation the dividend rights, dividend rate, conversion rights, voting
rights, rights and terms of redemption (including sinking fund provisions),
redemption price or prices, and the liquidation preferences of any wholly
unissued series of Preferred Stock, and to establish from time to time the
number of shares constituting any such series and the designation thereof, or
any of them (a "Preferred Stock Designation"); and to increase or decrease the
number of shares of any series subsequent to the issuance of shares of that
series, but not below the number of shares of such series then outstanding.  In
case the number of shares of any series shall be decreased in accordance with
the foregoing sentence, the shares constituting such decrease shall resume the
status that they had prior to the adoption of the resolution originally fixing
the number of shares of such series.

                                          1.


<PAGE>

    C.   No share or shares of any series of Preferred Stock acquired by the
Corporation by reason of redemption, purchase, conversion or otherwise shall be
reissued as part of such series, and the Board of Directors is authorized,
pursuant to Section 243 of the Delaware General Corporation law, to retire any
such share or shares.  The retirement of any such share or shares shall not
reduce the total authorized number of shares of Preferred Stock.

                                          V.

    For the management of the business and for the conduct of the affairs of
the corporation, and in further definition, limitation and regulation of the
powers of the corporation, of its directors and of its stockholders or any class
thereof, as the case may be, it is further provided that:

    A.   The management of the business and the conduct of the affairs of the
corporation shall be vested in its Board of Directors.  The number of directors
which shall constitute the whole Board of Directors shall be fixed exclusively
by one or more resolutions adopted by the Board of Directors.

    Following the closing of the initial public offering pursuant to an
effective registration statement under the Securities Act of 1933, as amended
(the "1933 Act"), covering the offer and sale of Common Stock to the public (the
"Initial Public Offering"), the directors shall be divided into three (3)
classes designated as Class I, Class II and Class III, respectively.  Directors
shall be assigned to each class in accordance with a resolution or resolutions
adopted by the Board of Directors.  At the first annual meeting of stockholders
following the closing of the Initial Public Offering, the term of office of the
Class I directors shall expire and Class I directors shall be elected for a full
term of three (3) years.  At the second annual meeting of stockholders following
the closing of the Initial Public Offering, the term of office of the Class II
directors shall expire and Class II directors shall be elected for a full term
of three (3) years.  At the third annual meeting of stockholders following the
closing of the Initial Public Offering, the term of office of the Class III
directors shall expire and Class III directors shall be elected for a full term
of three years.  At each succeeding annual meeting of stockholders, directors
shall be elected for a full term of three (3) years to succeed the directors of
the class whose terms expire at such annual meeting.

    Notwithstanding the foregoing provisions of this Article, each director
shall serve until his successor is duly elected and qualified or until his
death, resignation or removal.  No decrease in the number of directors
constituting the Board of Directors shall shorten the term of any incumbent
director.

    Any vacancies on the Board of Directors resulting from death, resignation,
disqualification, removal or other causes shall be filled by either (i) the
affirmative vote of the holders of a majority of the voting power of the
then-outstanding shares of voting stock of the corporation entitled to vote
generally in the election of directors (the "Voting Stock") voting together as a
single class; or (ii) by the affirmative vote of a majority of the remaining
directors then in office, even though less than a quorum of the Board of
Directors.  Newly created directorships resulting from any increase in the
number of directors shall, unless the Board of 

                                          2.


<PAGE>

Directors determines by resolution that any such newly created directorship
shall be filled by the stockholders, be filled only by the affirmative vote of
the directors then in office, even though less than a quorum of the Board of
Directors.  Any director elected in accordance with the preceding sentence shall
hold office for the remainder of the full term of the class of directors in
which the new directorship was created or the vacancy occurred and until such
director's successor shall have been elected and qualified.

    B.   The Bylaws may be altered or amended or new Bylaws adopted by the
affirmative vote of at least sixty-six and two-thirds percent (66-2/3%) of the
voting power of all of the then-outstanding shares of the Voting Stock.  In
furtherance and not in limitation of the power conferred by statute, the Board
of Directors is expressly authorized to adopt, amend, supplement or repeal the
Bylaws.

    C.   The directors of the corporation need not be elected by written ballot
unless the Bylaws so provide.

    D.   Following the closing of the Initial Public Offering, no action shall
be taken by the stockholders of the corporation except at an annual or special
meeting of stockholders called in accordance with the Bylaws and no action shall
be taken by the stockholders by written consent.

    E.   Advance notice of stockholder nominations for the election of
directors and of business to be brought by stockholders before any meeting of
the stockholders of the corporation shall be given in the manner provided in the
Bylaws of the corporation.

    F.   Any director, or the entire Board of Directors, may be removed from
office at any time (i) with cause by the affirmative vote of the holders of at
least a majority of the voting power of all of the then-outstanding shares of
the Voting Stock, voting together as a single class; or (ii) without cause by
the affirmative vote of the holders of at least sixty-six and two-thirds percent
(66-2/3%) of the voting power of all of the then-outstanding shares of the
Voting Stock.

                                 VI.

    (1)  A director of the corporation shall not be personally liable to the
corporation or its stockholders for monetary damages for breach of fiduciary
duty as a director, except for liability (i) for any breach of the director's
duty of loyalty to the corporation or its stockholders, (ii) for acts or
omissions not in good faith or which involve intentional misconduct or a knowing
violation of law, (iii) under Section 174 of the Delaware General Corporation
Law, or (iv) for any transaction from which the director derived any improper
personal benefit.  If the Delaware General Corporation Law is amended after
approval by the stockholders of this article to authorize corporate action
further eliminating or limiting the personal liability of directors, then the
liability of a director of the corporation shall be eliminated or limited to the
fullest extent permitted by the Delaware General Corporation Law, as so amended.

    (2)  The corporation is authorized to provide indemnification of agents (as
defined in Section 145 of the Delaware General Corporation Law) for breach of
duty to the corporation and its stockholders through bylaw provisions, through
agreements with the agents, and/or through 


                                          3.


<PAGE>

stockholder resolutions, or otherwise, in excess of the indemnification
otherwise permitted by Section 145 of the Delaware General Corporation Law,
subject to the limitations on such excess indemnification set forth in Section
102 of the Delaware General Corporation Law.

    (3)  Any repeal or modification of this Article VI by the stockholders of
the corporation shall not adversely affect any right or protection of a director
of the corporation existing at the time of such repeal or modification.

                                VII.

    Notwithstanding any other provisions of this Amended and Restated
Certificate of Incorporation or any provision of law which might otherwise
permit a lesser vote or no vote, but in addition to any affirmative vote of the
holders of any particular class or series of the Voting Stock required by law,
this Amended and Restated Certificate of Incorporation or any Preferred Stock
Designation, the affirmative vote of the holders of at least sixty-six and
two-thirds percent (66-2/3%) of the voting power of all of the then-outstanding
shares of the Voting Stock, voting together as a single class, shall be required
to alter, amend or repeal Article V or Article IX.

                                VIII.

    The corporation is to have perpetual existence.

                                IX.

    The corporation reserves the right to amend, alter, change or repeal any
provision contained in this Amended and Restated Certificate of Incorporation,
in the manner now or hereafter prescribed by statute, except as provided in
Article VII of this Certificate, and all rights conferred upon the stockholders
herein are granted subject to this right. 


                                          4.

<PAGE>

                                                                 Exhibit 3(i).2

                              CERTIFICATE OF DESIGNATION
                                          OF
                    SERIES A JUNIOR PARTICIPATING PREFERRED STOCK
                                          OF
                                    COCENSYS, INC.
                           (Pursuant to Section 151 of the
                          Delaware General Corporation Law)
                                           

    COCENSYS, INC., a corporation organized and existing under the General
Corporation Law of the State of Delaware (hereinafter called the "Corporation"),
hereby certifies that the following resolution was adopted by the Board of
Directors of the Corporation as required by Section 151 of the General
Corporation Law at a meeting duly called and held on April 25, 1995:

              RESOLVED, that pursuant to the authority granted to and vested in
         the Board of Directors of the Corporation in accordance with the
         provisions of its Amended and Restated Certificate of Incorporation,
         the Board of Directors hereby creates a series of Preferred Stock, par
         value $.001 per share, of the Corporation and hereby states the
         designation and number of shares, and fixes the relative rights,
         preferences and limitations thereof (in addition to the provisions set
         forth in the Restated Certificate of Incorporation of the Corporation,
         which are applicable to the Preferred Stock of all classes and
         series), as follows:

         Series A Junior Participating Preferred Stock:

              SECTION 1.  DESIGNATION AND AMOUNT.  Three Hundred Fifty Thousand
         (350,000) shares of Preferred Stock, $.001 par value, are designated
         "Series A Junior Participating Preferred Stock" with the rights,
         preferences, privileges and restrictions 


                                          1.


<PAGE>

         specified herein (the "Junior Preferred Stock").  Such number of
         shares may be increased or decreased by resolution of the Board of
         Directors; PROVIDED, that no decrease shall reduce the number of
         shares of Junior Preferred Stock to a number less than the number of
         shares then outstanding plus the number of shares reserved for
         issuance upon the exercise of outstanding options, rights or warrants
         or upon the conversion of any outstanding securities issued by the
         Corporation convertible into Junior Preferred Stock.

              SECTION 2.  DIVIDENDS AND DISTRIBUTIONS.

              (A)  Subject to the rights of the holders of any shares of any
         series of Preferred Stock (or any similar stock) ranking prior and
         superior to the Junior Preferred Stock with respect to dividends, the
         holders of shares of Junior Preferred Stock, in preference to the
         holders of Common Stock, par value $.001 per share (the "Common
         Stock"), of the Corporation, and of any other junior stock, shall be
         entitled to receive, when, as and if declared by the Board of
         Directors out of funds legally available for the purpose, quarterly
         dividends payable in cash on the first day of March, June, September
         and December in each year (each such date being referred to herein as
         a "Quarterly Dividend Payment Date"), commencing on the first
         Quarterly Dividend Payment Date after the first issuance of a share or
         fraction of a share of Junior Preferred Stock, in an amount per share
         (rounded to the nearest cent) equal to the greater of (a) $l.00 or (b)
         subject to the provision for adjustment hereinafter set forth, 100
         times the aggregate per share amount of all cash dividends, and 100
         times the aggregate per share amount (payable in kind) of all non-cash
         dividends or other distributions, other than a dividend payable in
         shares of Common Stock or a subdivision of the outstanding shares of
         Common Stock (by reclassification or otherwise) declared on the Common
         Stock since the immediately preceding Quarterly Dividend Payment Date
         or, with respect to the first Quarterly Dividend Payment Date, since
         the first issuance of any share or fraction of a share of Junior
         Preferred Stock.  In the event the Corporation shall at any time
         declare or pay any dividend on the Common Stock payable in shares of
         Common Stock, or effect a subdivision or combination or consolidation
         of the outstanding shares of Common Stock (by reclassification or
         otherwise than by payment of a dividend in shares of Common Stock)
         into a greater or lesser number of shares of Common Stock, then in
         each such case the amount to which holders of shares of Junior
         Preferred 

                                          2.


<PAGE>

         Stock were entitled immediately prior to such event under clause (b)
         of the preceding sentence shall be adjusted by multiplying such amount
         by a fraction, the numerator of which is the number of shares of
         Common Stock outstanding immediately after such event and the
         denominator of which is the number of shares of Common Stock that were
         outstanding immediately prior to such event.

              (B)  The Corporation shall declare a dividend or distribution on
         the Junior Preferred Stock as provided in paragraph (A) of this
         Section immediately after it declares a dividend or distribution on
         the Common Stock (other than a dividend payable in shares of Common
         Stock); provided that, in the event no dividend or distribution shall
         have been declared on the Common Stock during the period between any
         Quarterly Dividend Payment Date and the next subsequent Quarterly
         Dividend Payment Date, a dividend of $1.00 per share on the Junior
         Preferred Stock shall nevertheless be payable on such subsequent
         Quarterly Dividend Payment Date.

              (C)  Dividends shall begin to accrue and be cumulative on
         outstanding shares of Junior Preferred Stock from the Quarterly
         Dividend Payment Date next preceding the date of issue of such shares,
         unless the date of issue of such shares is prior to the record date
         for the first Quarterly Dividend Payment Date, in which case dividends
         on such shares shall begin to accrue from the date of issue of such
         shares, or unless the date of issue is a Quarterly Dividend Payment
         Date or is a date after the record date for the determination of
         holders of shares of Junior Preferred Stock entitled to receive a
         quarterly dividend and before such Quarterly Dividend Payment Date, in
         either of which events such dividends shall begin to accrue and be
         cumulative from such Quarterly Dividend Payment Date.  Accrued but
         unpaid dividends shall not bear interest.  Dividends paid on the
         shares of Junior Preferred Stock in an amount less than the total
         amount of such dividends at the time accrued and payable on such
         shares shall be allocated pro rata on a share-by-share basis among all
         such shares at the time outstanding.  The Board of Directors may fix a
         record date for the determination of holders of shares of Junior
         Preferred Stock entitled to receive payment of a dividend or
         distribution declared thereon, which record date shall be not more
         than 60 days prior to the date fixed for the payment thereof.


                                          3.


<PAGE>

              SECTION 3.  VOTING RIGHTS.  The holders of shares of Junior
         Preferred Stock shall have the following voting rights:

              (A)  Subject to the provision for adjustment hereinafter set
         forth, each share of Junior Preferred Stock shall entitle the holder
         thereof to 100 votes on all matters submitted to a vote of the
         stockholders of the Corporation.  In the event the Corporation shall
         at any time declare or pay any dividend on the Common Stock payable in
         shares of Common Stock, or effect a subdivision or combination or
         consolidation of the outstanding shares of Common Stock (by
         reclassification or otherwise than by payment of a dividend in shares
         of Common Stock) into a greater or lesser number of shares of Common
         Stock, then in each such case the number of votes per share to which
         holders of shares of Junior Preferred Stock were entitled immediately
         prior to such event shall be adjusted by multiplying such number by a
         fraction, the numerator of which is the number of shares of Common
         Stock outstanding immediately after such event and the denominator of
         which is the number of shares of Common Stock that were outstanding
         immediately prior to such event.

              (B)  Except as otherwise provided herein, in any other
         Certificate of Determination of Preferences creating a series of
         Preferred Stock or any similar stock, or by law, the holders of shares
         of Junior Preferred Stock and the holders of shares of Common Stock
         and any other capital stock of the Corporation having general voting
         rights shall vote together as one class on all matters submitted to a
         vote of stockholders of the Corporation.

              (C)  Except as set forth herein, or as otherwise provided by law,
         holders of Junior Preferred Stock shall have no special voting rights
         and their consent shall not be required (except to the extent they are
         entitled to vote with holders of Common Stock as set forth herein) for
         taking any corporate action.

              SECTION 4.  CERTAIN RESTRICTIONS.

              (A)  Whenever quarterly dividends or other dividends or
         distributions payable on the Junior Preferred Stock as provided in
         Section 2 are in arrears, thereafter and until all accrued and unpaid
         dividends and distributions, whether or not declared, on shares of
         Junior Preferred Stock outstanding shall have been paid in full, the
         Corporation shall not:


                                          4.


<PAGE>

                     (I)     declare or pay dividends, or make any other
         distributions, on any shares of stock ranking junior (either as to
         dividends or upon liquidation, dissolution or winding up) to the
         Junior Preferred Stock;

                    (II)     declare or pay dividends, or make any other
         distributions, on any shares of stock ranking on a parity (either as
         to dividends or upon liquidation, dissolution or winding up) with the
         Junior Preferred Stock, except dividends paid ratably on the Junior
         Preferred Stock and all such parity stock on which dividends are
         payable or in arrears in proportion to the total amounts to which the
         holders of all such shares are then entitled;

                   (III)     redeem or purchase or otherwise acquire for
         consideration shares of any stock ranking junior (either as to
         dividends or upon liquidation, dissolution or winding up) to the
         Junior Preferred Stock, provided that the Corporation may at any time
         redeem, purchase or otherwise acquire shares of any such junior stock
         in exchange for shares of any stock of the Corporation ranking junior
         (either as to dividends or upon dissolution, liquidation or winding
         up) to the Junior Preferred Stock; or

                    (IV)     redeem or purchase or otherwise acquire for
         consideration any shares of Junior Preferred Stock, or any shares of
         stock ranking on a parity with the Junior Preferred Stock, except in
         accordance with a purchase offer made in writing or by publication (as
         determined by the Board of Directors) to all holders of such shares
         upon such terms as the Board of Directors, after consideration of the
         respective annual dividend rates and other relative rights and
         preferences of the respective series and classes, shall determine in
         good faith will result in fair and equitable treatment among the
         respective series or classes.

              (B)  The Corporation shall not permit any subsidiary of the
         Corporation to purchase or otherwise acquire for consideration any
         shares of stock of the Corporation unless the Corporation could, under
         paragraph (A) of this Section 4, purchase or otherwise acquire such
         shares at such time and in such manner.

              SECTION 5.  REACQUIRED SHARES.  Any shares of Junior Preferred
         Stock purchased or otherwise acquired by the Corporation in any manner
         whatsoever shall be retired and cancelled promptly after the
         acquisition thereof.  All such shares shall upon their 


                                          5.


<PAGE>

         cancellation become authorized but unissued shares of Preferred Stock
         and may be reissued as part of a new series of Preferred Stock subject
         to the conditions and restrictions on issuance set forth herein, in
         the Restated Certificate of Incorporation, or in any other Certificate
         of Determination of Preferences creating a series of Preferred Stock
         or any similar stock or as otherwise required by law.

              SECTION 6.  LIQUIDATION, DISSOLUTION OR WINDING UP.  Upon any
         liquidation, dissolution or winding up of the Corporation, no
         distribution shall be made (1) to the holders of shares of stock
         ranking junior (either as to dividends or upon liquidation,
         dissolution or winding up) to the Junior Preferred Stock unless, prior
         thereto, the holders of shares of Junior Preferred Stock shall have
         received $100 per share, plus an amount equal to accrued and unpaid
         dividends and distributions thereon, whether or not declared, to the
         date of such payment, provided that the holders of shares of Junior
         Preferred Stock shall be entitled to receive an aggregate amount per
         share, subject to the provision for adjustment hereinafter set forth,
         equal to 100 times the aggregate amount to be distributed per share to
         holders of shares of Common Stock, or (2) to the holders of shares of
         stock ranking on a parity (either as to dividends or upon liquidation,
         dissolution or winding up) with the Junior Preferred Stock, except
         distributions made ratably on the Junior Preferred Stock and all such
         parity stock in proportion to the total amounts to which the holders
         of all such shares are entitled upon such liquidation, dissolution or
         winding up.  In the event the Corporation shall at any time declare or
         pay any dividend on the Common Stock payable in shares of Common
         Stock, or effect a subdivision or combination or consolidation of the
         outstanding shares of Common Stock (by reclassification or otherwise
         than by payment of a dividend in shares of Common Stock) into a
         greater or lesser number of shares of Common Stock, then in each such
         case the aggregate amount to which holders of shares of Junior
         Preferred Stock were entitled immediately prior to such event under
         the proviso in clause (1) of the preceding sentence shall be adjusted
         by multiplying such amount by a fraction the numerator of which is the
         number of shares of Common Stock outstanding immediately after such
         event and the denominator of which is the number of shares of Common
         Stock that were outstanding immediately prior to such event.

              SECTION 7.  CONSOLIDATION, MERGER, ETC. In case the Corporation
         shall enter into any consolidation, merger, combination or other
         transaction in which the shares of Common Stock are exchanged for or
         changed into other stock or securities, cash and/or any other
         property, then in any such case each share of Junior Preferred Stock
         shall at the same time be similarly exchanged or changed into an
         amount per share, subject to the provision for adjustment hereinafter
         set forth, equal to 100 times the aggregate amount of stock,
         securities, cash and/or 


                                          6.


<PAGE>

         any other property (payable in kind), as the case may be, into which
         or for which each share of Common Stock is changed or exchanged.  In
         the event the Corporation shall at any time declare or pay any
         dividend on the Common Stock payable in shares of Common Stock, or
         effect a subdivision or combination or consolidation of the
         outstanding shares of Common Stock (by reclassification or otherwise
         than by payment of a dividend in shares of Common Stock) into a
         greater or lesser number of shares of Common Stock, then in each such
         case the amount set forth in the preceding sentence with respect to
         the exchange or change of shares of Junior Preferred Stock shall be
         adjusted by multiplying such amount by a fraction, the numerator of
         which is the number of shares of Common Stock outstanding immediately
         after such event and the denominator of which is the number of shares
         of Common Stock that were outstanding immediately prior to such event.

              SECTION 8.  NO REDEMPTION.  The shares of Junior Preferred Stock
         shall not be redeemable.

              SECTION 9.  RANK.  The Junior Preferred Stock shall rank, with
         respect to the payment of dividends and the distribution of assets,
         junior to all series of any other class of the Corporation's Preferred
         Stock.

              SECTION 10.  AMENDMENT.  The Restated Certificate of
         Incorporation of the Corporation shall not be amended in any manner
         which would materially alter or change the powers, preferences or
         special rights of the Junior Preferred Stock so as to affect them
         adversely without the affirmative vote of the holders of at least
         two-thirds of the outstanding shares of Junior Preferred Stock, voting
         together as a single class.


                                          7.


<PAGE>

    IN WITNESS WHEREOF the undersigned have executed this certificate as of May
16, 1996.

                                  /s/ Daniel L. Korpolinski
                                  ______________________________________
                                  Daniel L. Korpolinski
                                  President and Chief Executive Officer


                                  /s/ Alan C. Mendelson
                                  _______________________________________
                                  Alan C. Mendelson
                                  Secretary


                                          8.


<PAGE>

                                                              Exhibit 3(i).3



                   CERTIFICATE OF POWERS, DESIGNATION, PREFERENCES,

                                RIGHTS AND LIMITATIONS

                                          OF

                         SERIES B CONVERTIBLE PREFERRED STOCK

                                          OF

                                    COCENSYS, INC.

                           (Pursuant to Section 151 of the
                          Delaware General Corporation Law)



    COCENSYS, INC., a corporation organized and existing under the General

Corporation Law of the State of Delaware (hereinafter called the "Corporation"),

hereby certifies that the following resolution was adopted by the Board of

Directors of the Corporation as required by Section 151 of the General

Corporation Law at meetings duly called and held on February 27 and May 16,

1996:

              RESOLVED, that pursuant to the authority granted to and vested in
         the Board of Directors of the Corporation in accordance with the
         provisions of its Amended and Restated Certificate of Incorporation,
         the Board of Directors hereby creates a series of Preferred Stock, par
         value $.001 per share, of the Corporation and hereby states the
         designation and number of shares, and fixes the relative rights,
         preferences and limitations thereof (in addition to the provisions set
         forth in the Restated Certificate of Incorporation of the Corporation,
         which are applicable to the Preferred Stock of all classes and
         series), as follows:

         Series B Convertible Preferred Stock:

              SECTION 3. DESIGNATION AND AMOUNT.  One Hundred Thousand 
         (100,000) shares of Preferred Stock, $.001 par value, are designated
         "Series B Convertible Preferred Stock" with the rights, preferences,
         privileges and restrictions specified herein


                                       1.

<PAGE>


         (the "Series B Preferred Stock"). Subject to Section 7 hereof, such
         number of shares may be increased or decreased by resolution of the
         Board of Directors.

            SECTION 2. DIVIDENDS AND DISTRIBUTIONS.  The holders of the Series
         B Preferred Stock shall be entitled to receive, when, as and if
         declared by the Board of Directors, out of funds legally available
         therefor, dividends at the rate per share equal to any dividend
         declared or paid per share to the Common Stock of the Corporation
         ("Common Stock").  The right to such dividends on the Series B
         Preferred Stock shall be non-cumulative.

            SECTION 3. VOTING RIGHTS.  Except as set forth herein, or as
         otherwise provided by law, holders of Series B Preferred Stock shall
         have no special voting rights and their consent shall not be required
         (except to the extent they are entitled to vote with holders of Common
         Stock as set forth herein) for taking any corporate action.

            SECTION 4. LIQUIDATION PREFERENCE. In the event of any liquidation,
         dissolution or winding up of the Corporation, either voluntary or
         involuntary (a "Liquidation Event"),  the holders of the Series B
         Preferred Stock shall be entitled to receive, prior and in preference
         to any distribution of any of the assets or surplus funds of the
         Corporation to the holders of the Common Stock or Junior Preferred
         Stock of the Corporation, an amount per share (as adjusted for any
         combinations, consolidations, stock distributions or stock dividends
         with respect to such shares) equal to the quotient of (a) $7,000,000
         divided by (b) the number of Series B Preferred Stock issued and
         outstanding as of the date of such Liquidation Event.  If upon the
         occurrence of such Liquidation Event, the assets and funds thus
         distributed among the holders of the Series B Preferred Stock shall be
         insufficient to permit the payment to such holders of the full
         aforesaid preferential amount, then the entire assets and funds of the
         Corporation legally available for distribution shall be distributed
         among the holders of the Series B Preferred Stock in proportion to the
         shares of Series B Preferred Stock then held by them.

           SECTION 5. CONVERSION.  Subject to the limitations set forth in
         Subsection (C) below, the Series B Preferred Stock shall convert only
         as follows:  

              (A)   AUTOMATIC CONVERSION.  The Series B Preferred Stock
         outstanding on May 17, 1998 (the "Automatic Conversion

                                       2.

<PAGE>

         Date") shall automatically convert on such date, in whole and not
         in part, into such number of fully paid and nonassessable shares of
         Common Stock equal to the quotient of $7,000,000 divided by the
         average closing price of the Corporation's Common Stock (as reported
         in THE WALL STREET JOURNAL, WESTERN ADDITION) for a period of thirty
         (30) trading days prior to the Automatic Conversion Date.

              (B)  CONVERSION AT CORPORATION'S OPTION.  At any time prior to
         the Automatic Conversion Date, the Corporation shall have the option,
         in its sole discretion, to convert the Series B Preferred Stock, in
         whole and not in part, into such number of fully paid and
         nonassessable shares of Common Stock equal to the quotient of
         $7,000,000 divided by the average closing price of the Corporation's
         Common Stock (as reported in THE WALL STREET JOURNAL, WESTERN
         ADDITION) for a period of thirty (30) trading days prior to date upon
         which the Corporation issues notice to the holders of Series B
         Preferred Stock of such optional conversion.

              (C)   LIMITATION ON CONVERTED SHARES.  The number of shares of
         Common Stock issuable upon conversion of the Series B Preferred Stock
         shall not be fewer than the quotient of $7,000,000 divided by two
         times the closing price of the Common Stock on May 17, 1996 (as
         reported in the WALL STREET JOURNAL, WESTERN EDITION) (the "Market
         Price"), nor greater than the quotient of $7,000,000 divided by
         one-half of the Market Price.

              (D)   ADJUSTMENTS FOR COMBINATIONS OR SUBDIVISIONS OF COMMON
         STOCK.  In the event the Corporation at any time or from time to time
         shall declare or pay any dividend on the Common Stock payable in
         Common Stock or in any right to acquire Common Stock, or shall effect
         a subdivision of the outstanding shares of Common Stock into a greater
         number of shares of Common Stock (by stock split, reclassification or
         otherwise), or in the event the outstanding shares of Common Stock
         shall be combined or consolidated, by reclassification or otherwise,
         into a lesser number of shares of Common Stock, then the maximum and
         minimum number of shares of Common Stock into which the Series B
         Preferred Stock may be converted, shall be proportionately decreased
         or increased, as appropriate.

              (E)   MECHANICS OF CONVERSION.  Before any holder of Series B
         Preferred Stock shall be entitled to receive shares of Common Stock,
         he shall surrender the certificate or certificates thereof, duly
         endorsed, at the office of the Corporation or of any transfer agent
         for such stock, and shall state therein the name or 

                                       3.

<PAGE>

         names in which he wishes the certificate or certificates for shares
         of Common Stock to be issued.  The Corporation shall, as soon as
         practicable thereafter, issue and deliver at such office to such
         holder of Series B Preferred Stock, a certificate or certificates
         for the number of shares of Common Stock to which he shall be
         entitled as aforesaid.  Such conversion shall be deemed to have been
         made immediately prior to the close of business on the Automatic
         Conversion Date or the Optional Conversion Date, as appropriate,
         and the person or persons entitled to receive the shares of Common
         Stock issuable upon such conversion shall be treated for all purposes
         as the record holder or holders of such shares of Common Stock on such
         date.

            (F)   RESERVATION OF STOCK ISSUABLE UPON CONVERSION.  The
         Corporation shall at all times reserve and keep available out of its
         authorized but unissued shares of Common Stock, solely for the purpose
         of effecting the conversion of the shares of the Series B Preferred
         Stock, such number of its shares of Common Stock as shall from time to
         time be sufficient to effect the conversion of all outstanding shares
         of the Series B Preferred Stock.

            (G)   FRACTIONAL SHARES.  No fractional share shall be issued upon
         the conversion of any share or shares of Series B Preferred Stock. 
         All shares of Common Stock (including fractions thereof) issuable upon
         conversion of Series B Preferred Stock shall be aggregated for
         purposes of determining whether the conversion would result in the
         issuance of any fractional share.  If, after the aforementioned
         aggregation, the conversion would result in the issuance of a fraction
         of a share of Common Stock, the Corporation shall, in lieu of issuing
         any fractional share, pay the holder otherwise entitled to such
         fraction a sum in cash equal to the closing price of the Common Stock
         on the date of conversion, multiplied by such fraction.

            (H)   REORGANIZATION, RECLASSIFICATION, CONSOLIDATION, MERGER OR
         SALE.  If any (i) reorganization of the capital stock of the
         Corporation, (ii) consolidation or merger of the Corporation in which
         the Corporation is not the surviving corporation, or (iii) sale of all
         or substantially all of the Corporation's assets to another
         corporation (each, an "Event") shall be effected in such a way that
         holders of Common Stock shall be entitled to receive securities, cash
         or other assets or property, the Automatic Conversion Date shall be
         accelerated to the date immediately preceding such Event, or such
         other date necessary to assure that any holder of Series B Preferred
         Stock receives such shares of stock, securities or other

                                       4.

<PAGE>

         assets or property as may be issued or payable with respect to or in
         exchange for shares of Common Stock.

            SECTION 6. NO REDEMPTION.  The shares of Series B Preferred Stock 
         shall not be redeemable. 

            SECTION 7. AMENDMENT.  The Restated Certificate of Incorporation of
         the Corporation shall not be amended in any manner which would
         materially alter or change the powers, preferences or special rights
         of the Series B Preferred Stock so as to affect them adversely without
         the affirmative vote of the holders of at least two-thirds of the
         outstanding shares of Series B Preferred Stock, voting together as a
         single class.



                                       5.

<PAGE>


    IN WITNESS WHEREOF the undersigned have executed this certificate as of May
16, 1996.








                                   /s/ Daniel L. Korpolinski 
                                   ----------------------------------
                                   Daniel L. Korpolinski
                                   President and Chief Executive Officer







                                   /s/ Alan C. Mendelson  
                                   ----------------------------------
                                   Alan C. Mendelson
                                   Secretary













                                       6.


<PAGE>

                                                                 Exhibit 3(i).4


                               CERTIFICATE OF AMENDMENT

                                          OF

                  AMENDED AND RESTATED CERTIFICATE OF INCORPORATION

                                          OF

                                    COCENSYS, INC.



    Daniel L. Korpolinski and Alan C. Mendelson hereby certify that: 

    FIRST:  They are the duly elected and acting President and Secretary,
respectively, of CoCensys, Inc., a Delaware corporation.

    SECOND: The name of this Corporation is COCENSYS, INC. (the "Corporation").

    THIRD: The date on which the Amended and Restated Certificate of
Incorporation was filed with the Secretary of State of the State of Delaware is
February 5, 1993.  A Certificate of Retirement of Series A, Series B and Series
C Preferred Stock was filed with the Secretary of State of the State of Delaware
on February 5, 1993.  A Certificate of Designation of Series A Junior
Participating Preferred Stock was filed with the Secretary of State of the State
of Delaware on May 15, 1995.  A Certificate of Powers, Designation, Preferences,
Rights and Limitations of Series B Convertible Preferred Stock was filed with
the Secretary of State of the State of Delaware on May 17, 1996. 

    FOURTH: The amendment to the Corporation's Amended and Restated Certificate
of Incorporation set forth below was duly adopted by the Board of Directors of
the Corporation, and approved by the Stockholders in accordance with the
provisions of Section 242 of the General Corporation Law of the State of
Delaware.

    FIFTH:  Article IV, Paragraph A of the Corporation's Certificate of
Incorporation is amended to read in its entirety as follows:

                                         "IV.

    A.   This corporation is authorized to issue two classes of stock to be
designated, respectively, "Common Stock" and "Preferred Stock."  The total
number of shares which the corporation is authorized to issue is eighty million
(80,000,000) shares.  Seventy-five million (75,000,000) shares shall be Common
Stock, each having a par value of one-tenth of one cent ($.001).  Five million
(5,000,000) shares shall be Preferred Stock, each having a par value of
one-tenth of one cent ($.001)." 


                                          1.


<PAGE>

    IN WITNESS WHEREOF, the undersigned have signed this Certificate of
Amendment of Amended and Restated Certificate of Incorporation this 12th day of
June, 1996 and hereby affirm and acknowledge under penalty of perjury that the
filing of this Certificate of Amendment of Amended and Restated Certificate of
Incorporation of CoCensys, Inc. is the act and deed of COCENSYS, INC.

                                  COCENSYS, INC. 





                                  By: /s/ Daniel L. Korpolinski
                                      ______________________________________

                                       Daniel L. Korpolinski, President and
                                       Chief Executive Officer


ATTEST:



By: /s/ Alan C. Mendelson 
    ____________________________________
    Alan C. Mendelson, 
    Secretary


                                          2.


<PAGE>

                CERTIFICATE OF POWERS, DESIGNATION, PREFERENCES,
                             RIGHTS AND LIMITATIONS

                                       OF

                      SERIES C CONVERTIBLE PREFERRED STOCK

                                       OF

                                 COCENSYS, INC.

                         (Pursuant to Section 151 of the
                        Delaware General Corporation Law)


     COCENSYS, INC., a corporation organized and existing under the General 
Corporation Law of the State of Delaware (hereinafter called the 
"Corporation"), hereby certifies that the following resolution was adopted by 
the Board of Directors of the Corporation as required by Section 151 of the 
General Corporation Law at a meeting duly called and held on April 29, 1997:

               RESOLVED, that pursuant to the authority granted to and
          vested in the Board of Directors of the Corporation in
          accordance with the provisions of its Amended and Restated
          Certificate of Incorporation, the Board of Directors hereby
          creates a series of Preferred Stock, par value $.001 per
          share, of the Corporation and hereby states the designation
          and number of shares, and fixes the relative rights,
          preferences and limitations thereof (in addition to the
          provisions set forth in the Restated Certificate of
          Incorporation of the Corporation, which are applicable to
          the Preferred Stock of all classes and series), as follows:

          Series C Convertible Preferred Stock:

               SECTION 1.  DESIGNATION AND AMOUNT.  One Hundred
          Thousand (100,000) shares of Preferred Stock, $.001 par
          value, are designated "Series C Convertible Preferred Stock"
          with the rights, preferences, privileges and restrictions
          specified herein (the 

                                       1.

<PAGE>

          "Series C Preferred Stock").  Such number of shares may be not 
          increased or decreased without the consent of the holder.

               SECTION 2.  DIVIDENDS AND DISTRIBUTIONS.  The holders
          of the Series C Preferred Stock shall be entitled to
          receive, when, as and if declared by the Board of Directors,
          out of funds legally available therefor, dividends at the
          rate per share equal to any dividend declared or paid per
          share to the Common Stock of the Corporation ("Common
          Stock").  The right to such dividends on the Series C
          Preferred Stock shall be non-cumulative.

               SECTION 3.  VOTING RIGHTS.    Except as set forth
          herein, or as otherwise provided by law, holders of Series C
          Preferred Stock shall have no special voting rights and
          their consent shall not be required (except to the extent
          they are entitled to vote with holders of Common Stock as
          set forth herein) for taking any corporate action.

               SECTION 4.  LIQUIDATION PREFERENCE. In the event of any
          liquidation, dissolution or winding up of the Corporation,
          either voluntary or involuntary (a "Liquidation Event"), 
          the holders of the Series C Preferred Stock shall be
          entitled to receive, prior and in preference to any
          distribution of any of the assets or surplus funds of the
          Corporation to the holders of the Common Stock or Junior
          Preferred Stock of the Corporation, an amount per share (as
          adjusted for any combinations, consolidations, stock
          distributions or stock dividends with respect to such
          shares) equal to the quotient of (a) $5,000,000 divided by
          (b) the number of shares of Series C Preferred Stock issued
          and outstanding as of the date of such Liquidation Event. 
          If upon the occurrence of such Liquidation Event, the assets
          and funds thus distributed among the holders of the Series C
          Preferred Stock shall be insufficient to permit the payment
          to such holders of the full aforesaid preferential amount,
          then the entire assets and funds of the Corporation legally
          available for distribution shall be distributed among the
          holders of the Series C Preferred Stock in proportion to the
          shares of Series C Preferred Stock then held by them.

               SECTION 5.  CONVERSION.  Subject to the limitations set
          forth in Subsection (B) below, the Series C Preferred Stock
          shall convert only as follows:  

               (A)  CONVERSION AT HOLDER'S OPTION.  At any time after
          May 11, 1999, the Series C Preferred Stock shall be
          convertible, in whole or in part, on a maximum of three
          occasions, at the 

                                       2.

<PAGE>

          option of the holder, into such number of fully paid and 
          nonassessable shares of Common Stock equal to the quotient 
          of (a) the product of $50 and the number of shares of 
          Series C Preferred Stock being converted, divided by (b) 
          the Conversion Price.  

          The "Conversion Price" shall be equal to the greater of:

               (i)  $5.43 or

               (ii) the lesser of:

                    (x) the Future Market Price x 0.80 or

                    (y) $7.76;

          PROVIDED, HOWEVER, that if the Future Market Price is less
          than $3.88, the Conversion Price shall be $4.37.

          The "Future Market Price" set forth above shall be the
          average closing price of the Common Stock for the period
          commencing on the 23rd trading day prior to the date upon
          which the holder delivers notice to the Corporation of such
          conversion (each, a "Conversion Date") and ending on the
          third trading day prior to the Conversion Date, as reported
          in the WALL STREET JOURNAL, WESTERN EDITION.

               (B)  ADJUSTMENTS FOR COMBINATIONS OR SUBDIVISIONS OF
          COMMON STOCK.  In the event the Corporation at any time or
          from time to time shall declare or pay any dividend on the
          Common Stock payable in Common Stock or in any right to
          acquire Common Stock, or shall effect a subdivision of the
          outstanding shares of Common Stock into a greater number of
          shares of Common Stock (by stock split, reclassification or
          otherwise), or in the event the outstanding shares of Common
          Stock shall be combined or consolidated, by reclassification
          or otherwise, into a lesser number of shares of Common
          Stock, then the maximum and minimum number of shares of
          Common Stock into which the Series C Preferred Stock may be
          converted, shall be proportionately decreased or increased,
          as appropriate.

               (C)  MECHANICS OF CONVERSION.  Before any holder of
          Series C Preferred Stock shall be entitled to receive shares
          of Common Stock, he shall surrender the certificate or
          certificates thereof, duly endorsed, at the office of the
          Corporation or of any transfer agent for such stock, and
          shall state therein the name or 

                                       3.

<PAGE>

          names in which he wishes the certificate or certificates 
          for shares of Common Stock to be issued.  The Corporation 
          shall, as soon as practicable thereafter, issue and deliver 
          at such office to such holder of Series C Preferred Stock, 
          a certificate or certificates for the number of shares of 
          Common Stock to which he shall be entitled as aforesaid.  
          Such conversion shall be deemed to have been made on the 
          Conversion Date, and the person or persons entitled to 
          receive the shares of Common Stock issuable upon such 
          conversion shall be treated for all purposes as the record 
          holder or holders of such shares of Common Stock on such 
          date.  

               (D)  RESERVATION OF STOCK ISSUABLE UPON CONVERSION. 
          The Corporation shall at all times reserve and keep
          available out of its authorized but unissued shares of
          Common Stock, solely for the purpose of effecting the
          conversion of the shares of the Series C Preferred Stock,
          such number of its shares of Common Stock as shall from time
          to time be sufficient to effect the conversion of all
          outstanding shares of the Series C Preferred Stock.

               (E)  FRACTIONAL SHARES.  No fractional share shall be
          issued upon the conversion of any share or shares of Series
          C Preferred Stock.  All shares of Common Stock (including
          fractions thereof) issuable upon conversion of Series C
          Preferred Stock shall be aggregated for purposes of
          determining whether the conversion would result in the
          issuance of any fractional share.  If, after the
          aforementioned aggregation, the conversion would result in
          the issuance of a fraction of a share of Common Stock, the
          Corporation shall, in lieu of issuing any fractional share,
          pay the holder otherwise entitled to such fraction a sum in
          cash equal to the closing price of the Common Stock on the
          date of conversion, multiplied by such fraction.

               (F)  REORGANIZATION, RECLASSIFICATION, CONSOLIDATION,
          MERGER OR SALE.  If any (i) reorganization of the capital
          stock of the Corporation, (ii) consolidation or merger of
          the Corporation in which the Corporation is not the
          surviving corporation, or (iii) sale of all or substantially
          all of the Corporation's assets to another corporation
          (each, an "Event") shall be effected in such a way that
          holders of Common Stock shall be entitled to receive
          securities, cash or other assets or property, the first
          Conversion Date shall be accelerated to the date immediately
          preceding such Event, or such other date necessary to assure
          that any holder of Series C Preferred Stock receives such
          shares of stock, securities or other assets or property as
          may be issued or payable with respect to or in exchange for
          shares of Common Stock.

                                       4.

<PAGE>

               SECTION 6.     NO REDEMPTION.  The shares of Series C
          Preferred Stock shall not be redeemable. 

               SECTION 7.  AMENDMENT.  The Restated Certificate of
          Incorporation of the Corporation shall not be amended in any
          manner which would materially alter or change the powers,
          preferences or special rights of the Series C Preferred
          Stock so as to affect them adversely without the affirmative
          vote of the holders of at least two-thirds of the
          outstanding shares of Series C Preferred Stock, voting
          together as a single class.

                                       5.

<PAGE>

     IN WITNESS WHEREOF the undersigned have executed this certificate as of May
12, 1997.


                                   /s/ F. Richard Nichol, Ph.D.
                                   --------------------------------------------
                                   President and Chief Executive Officer



                                   /s/ Alan C. Mendelson
                                   --------------------------------------------
                                   Secretary






                                       6.




<PAGE>



                               1997 PROMOTION AGREEMENT

                                       BETWEEN

                            SOMERSET PHARMACEUTICALS, INC.

                                         AND

                                    COCENSYS, INC.


<PAGE>

                                  TABLE OF CONTENTS

                                                                            PAGE

ARTICLE 1.    DEFINITIONS...................................................  2
    1.1       "Actual Gross Sales"..........................................  2
    1.2       "Actual Monthly Details"......................................  2
    1.3       "Actual Quarterly Details"....................................  2
    1.4       "Adjusted Annualized Detail Payment Reduction"................  2
    1.5       "Adjusted Detail-Based Compensation Reconciliation Payment"...  3
    1.6       "Adjusted Target Details".....................................  3
    1.7       "Affiliate"...................................................  3
    1.8       "Annualized Detail Payment Reduction".........................  3
    1.9       "CoCensys ELDEPRYL Sales Force"...............................  3
    1.10      "Detail-Based Compensation"...................................  3
    1.11      "Detail-Based Compensation Reconciliation Payment"............  3
    1.12      "Effective Date"..............................................  4
    1.13      "ELDEPRYL Brand"..............................................  4
    1.14      "ELDEPRYL Brand Unit".........................................  4
    1.15      "ELDEPRYL Detail".............................................  4
    1.16      "FDA".........................................................  4
    1.17      "First Position Presentation".................................  5
    1.18      "Gross Sales-Based Compensation"..............................  5
    1.19      "Key Prescribers".............................................  5
    1.20      "Key Prescriber Marketing Plan"...............................  5
    1.21      "Managing Committee"..........................................  5
    1.22      "Minimum Aggregate Monthly Details"...........................  6
    1.23      "Minimum Aggregate Quarterly Details".........................  6
    1.24      "Monthly Detail Payment"......................................  7
    1.25      "Monthly Detail Payment Reduction"............................  7
    1.26      "NDA".........................................................  7
    1.27      "Promotional Materials".......................................  7
    1.28      "Proprietary Information".....................................  7
    1.29      "Quarterly Detail Payment"....................................  7
    1.30      "Quarterly Detail Payment Reduction"..........................  7
    1.31      "Sample"......................................................  7
    1.32      "Target Aggregate Monthly Details"............................  8
    1.33      "Target Aggregate Quarterly Details"..........................  8
    1.34      "Term"........................................................  8
    1.35      "Territory"...................................................  9
    1.36      "Total Actual Details"........................................  9
    1.37      "Total Detail Payment Reduction"..............................  9
    1.38      "Total Government Discounts and Rebates"......................  9


                                          i.

<PAGE>

                                  TABLE OF CONTENTS
                                     (CONTINUED)
                                                                            PAGE

ARTICLE 2.    PROMOTION RIGHTS.............................................. 10
    2.1       Appointment of CoCensys....................................... 10
    2.2       Rights Retained by Somerset................................... 10

ARTICLE 3.    MANAGING COMMITTEE; KEY PRESCRIBER MARKETING PLAN............. 11
    3.1       Managing Committee............................................ 11
              (a)  Formation; Meetings...................................... 11
              (b)  Functions of the Managing Committee...................... 12
    3.2       Dispute Resolution............................................ 13

ARTICLE 4.    PROMOTION OF ELDEPRYL BRAND................................... 14
    4.1       CoCensys ELDEPRYL Sales Force................................. 14
    4.2       Training of CoCensys ELDEPRYL Sales Force..................... 14
              (a)  Continued Training....................................... 14
              (b)  Training Costs........................................... 15
    4.3       CoCensys ELDEPRYL Sales Force Support......................... 15
    4.4       Conduct of the CoCensys ELDEPRYL Sales Force.................. 15
    4.5       Bonus Program for CoCensys ELDEPRYL Sales Force............... 16
    4.6       Other Marketing Activities to Physicians...................... 17
              (a)  Physicians Who Are Not Key Prescribers................... 17
              (b)  Non-Sales Call Activity.................................. 17
    4.7       Other Uses of CoCensys Sales Force............................ 18
    4.8       Number of ELDEPRYL Details.................................... 19
    4.9       Records and Reports Regarding Promotion Activities............ 19
    4.10      Forwarding of ELDEPRYL Brand Orders........................... 20

ARTICLE 5.    SOMERSET RIGHTS AND OBLIGATIONS............................... 20
    5.1       [     *     ] Marketing Responsibility........................ 20
    5.2       Supply and Distribution of ELDEPRYL Brand..................... 21
    5.3       Regulatory Compliance......................................... 21
    5.4       Product Recall................................................ 21
    5.5       Promotional Materials......................................... 22
              (a)  Somerset Materials....................................... 22
              (b)  Rights To Promotional Materials.......................... 22
    5.6       [     *     ] Developments Relating to ELDEPRYL Brand......... 23
    5.7       Sales and Inventory Data...................................... 23
    5.8       Somerset Costs................................................ 24


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                                  TABLE OF CONTENTS
                                     (CONTINUED)
                                                                            PAGE

ARTICLE 6.    JOINT OBLIGATIONS............................................. 24
    6.1       Assistance and Notifications to Other Party................... 24
    6.2       Samples of ELDEPRYL Brand..................................... 25
              (a)  Costs.................................................... 25
              (b)  Shrink-Wrap.............................................. 25
              (c)  Disposition Upon Termination............................. 25
    6.3       Requests for Information from Key Prescribers................. 26
    6.4       Market Surveys................................................ 26
    6.5       Withdrawal of ELDEPRYL Brand.................................. 26
    6.6       Non-Solicitation of Employees................................. 27

ARTICLE 7.    COMPENSATION.................................................. 27
    7.1       Detail-Based Compensation..................................... 27
              (a)  Detail Payments.......................................... 27
              (b)  Reduction in Detail Payments............................. 29
              (c)  Detail-Based Compensation Reconciliation................. 31
              (d)  ......................................................... 34
    7.2       Gross Sales-Based Compensation................................ 34
              (a)  ......................................................... 34
              (b)  ......................................................... 34
              (c)  ......................................................... 35
              (d)  ......................................................... 35
    7.3       Adjustments in the Event of Changes in Government Mandated
              Discounts and Rebates......................................... 36
    7.4       Audit Rights.................................................. 37

ARTICLE 8.    TERM; TERMINATION............................................. 38
    8.1       Renewal Terms................................................. 38
    8.2       Termination Rights............................................ 38
    8.3       Termination Upon Cessation of Sale of ELDEPRYL Brand.......... 38
    8.4       Termination for Breach........................................ 38
    8.5       Effect of Termination......................................... 39
    8.6       Termination of the 1996 Agreement............................. 39

ARTICLE 9.    WARRANTIES, REPRESENTATIONS AND COVENANTS..................... 40
    9.1       Warranties and Representations of Each Party.................. 40
    9.2       Warranties and Representations of Somerset.................... 40
    9.3       Warranties and Representations of CoCensys.................... 41


                                         iii.


<PAGE>

                                  TABLE OF CONTENTS
                                     (CONTINUED)
                                                                            PAGE

ARTICLE 10.   INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS.................. 41
    10.1      Notice........................................................ 41
    10.2      Conduct of Infringement Actions............................... 41

ARTICLE 11.   INDEMNIFICATION............................................... 42
    11.1      Indemnification by Somerset................................... 42
    11.2      Indemnification by CoCensys................................... 42
    11.3      Indemnification Procedure..................................... 43

ARTICLE 12.   CONFIDENTIALITY............................................... 44
    12.1      Nondisclosure and Nonuse Obligations.......................... 44
    12.2      Exceptions.................................................... 45
    12.3      Authorized Disclosure......................................... 45
    12.4      Obligations at End of Term.................................... 46
    12.5      Retention of Proprietary Information.......................... 46

ARTICLE 13.   PUBLICITY..................................................... 47
    13.1      ...............................................................47
    13.2      ...............................................................47

ARTICLE 14.   MISCELLANEOUS................................................. 48
    14.1      Notices....................................................... 48
    14.2      Captions and Section References............................... 48
    14.3      Severability.................................................. 49
    14.4      Entire Agreement.............................................. 49
    14.5      Amendment..................................................... 49
    14.6      Counterparts.................................................. 50
    14.7      Waiver........................................................ 50
    14.8      Force Majeure................................................. 50
    14.9      Assignment; Benefits and Binding Nature of Agreement.......... 50
    14.10     Survival...................................................... 51
    14.11     Not Strictly Construed Against Either Party................... 51
    14.12     Governing Law................................................. 51


                                         iv.
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                                  TABLE OF CONTENTS
                                     (CONTINUED)
                                                                            PAGE

Exhibit 5.7 - Somerset Standard Sales Report Format.......................... 53

Exhibit 7.1(d) -  Examples of Calculation of Detail-Based Compensation Under
    Different Hypothetical Scenarios......................................... 54

Exhibit 7.2.................................................................. 57


                                          v.
<PAGE>


                               1997 PROMOTION AGREEMENT

    THIS 1997 PROMOTION AGREEMENT ("Agreement"), is made this 7 day of April,
1997, by and between SOMERSET PHARMACEUTICALS, INC., with offices at 5215  W.
Laurel Street, Tampa, Florida 33607 ("Somerset"), and COCENSYS, INC., with
offices at 213 Technology Drive, Irvine, California 92718 ("CoCensys"), with
respect to the following:

    WHEREAS, Somerset has the right, under its approved New Drug Application,
to market ELDEPRYL Brand (as further defined in Section 1.13) in the United
States; and

    WHEREAS, CoCensys has established a marketing and a sales organization
which currently is promoting certain drugs belonging to third parties to
neurologists and psychiatrists pursuant to certain agreements on file with the
United States Securities and Exchange Commission as of the date of this
Agreement; and

    WHEREAS, the  parties  executed a Promotion Agreement dated January 4, 1996
whereby Somerset utilized CoCensys' sales force to promote ELDEPRYL Brand to
neurologists in the United States on terms and conditions contained therein.

    WHEREAS, the parties wish to terminate the January 4, 1996 Promotion
Agreement and continue their relationship on the revised terms provided for in
this Agreement.


                                          1.
<PAGE>

    NOW, THEREFORE, in consideration of the foregoing premises and of the
mutual covenants and obligations hereinafter set forth, the parties hereto agree
as follows:

                                      ARTICLE 1.
                                     DEFINITIONS

    The following capitalized terms shall have the meanings indicated for
purposes of this Agreement:

    1.1  "ACTUAL GROSS SALES" shall mean,  during the Term, [      *      ].
The amount of Actual Gross Sales may be adjusted upon mutual agreement of the
parties pursuant to Section 7.3.

    1.2  "ACTUAL MONTHLY DETAILS" shall have the meaning set forth in Section
7.1(b)(ii)

    1.3  "ACTUAL QUARTERLY DETAILS" shall have the meaning set forth in Section
7.1(b)(i).

    1.4  "ADJUSTED ANNUALIZED DETAIL PAYMENT REDUCTION" shall have the meaning
set forth in Section 7.1(c)(ii).

    1.5  "ADJUSTED DETAIL-BASED COMPENSATION RECONCILIATION PAYMENT" shall have
the meaning set forth in Section 7.1(c)(ii).


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    1.6   "ADJUSTED TARGET DETAILS" shall have the meaning set forth in Section
7.1(c)(ii).

    1.7   "AFFILIATE" shall mean any corporation, association or other entity
which directly or indirectly controls, is controlled by or is under common
control with the party in question.  Solely for purposes of this definition, the
term "control" shall mean direct or indirect beneficial ownership equal to or in
excess of 50% of the voting or income interest in such corporation or other
business entity.

    1.8   "ANNUALIZED DETAIL PAYMENT REDUCTION" shall have the meaning set
forth in Section 7.1(c)(i).

    1.9   "COCENSYS ELDEPRYL SALES FORCE" shall mean those members of
CoCensys's sales force, as more fully described in Section 4.7, who make
ELDEPRYL Details to Key Prescribers.

    1.10  "DETAIL-BASED COMPENSATION" shall have the meaning set forth in
Section 7.1(a)(i).

    1.11  "DETAIL-BASED COMPENSATION RECONCILIATION PAYMENT" shall have the
meaning set forth in Section 7.1(c)(i).


    1.12  "EFFECTIVE DATE" shall mean January 1, 1997.


                                          3.
<PAGE>

    1.13  "ELDEPRYL BRAND" shall mean (i) that prescription pharmaceutical
product, in 5 mg capsule form, indicated in the Territory for the adjunctive
treatment of late stage Parkinson's disease, owned by Somerset and promoted as
of the Effective Date under the trademark ELDEPRYL, the active ingredient of
which is selegiline hydrochloride (the "Current Formulation") and 
[      *      ].

    1.14  "ELDEPRYL BRAND UNIT" shall mean 60 capsules, 5 mg each, of ELDEPRYL
Brand.

    1.15  "ELDEPRYL DETAIL" shall mean a [     *     ] detail for ELDEPRYL
Brand between a CoCensys salesperson and a Key Prescriber.  As used herein, [
*     ] means that ELDEPRYL Brand is [          *          ] such sales call.

    1.16  "FDA" shall mean the United States Food and Drug Administration.

    1.17  "FIRST POSITION PRESENTATION" shall mean a single discussion relating
to a pharmaceutical product which is held at the commencement of a meeting
between a CoCensys salesperson and a physician.

    1.18  "GROSS SALES-BASED COMPENSATION" shall have the meaning set forth in
Section 7.2.


                                          4.

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   1.19  "KEY PRESCRIBERS" shall mean those neurologists and "High Prescribing
Non-Neurologists" in the Territory, set forth on a target list approved by the
Managing Committee pursuant to Section 3.1(b)(v), as such target list may be
amended from time to time during the Term, to whom CoCensys will make ELDEPRYL
Details.  "High Prescribing Non-Neurologists" shall mean those non-neurologists
in the Territory who rank [     *     ] in CoCensys' decile system for
identifying high prescribers of ELDEPRYL Brand, and any other non-neurologists
agreed to by Somerset.

   1.20  "KEY PRESCRIBER MARKETING PLAN" shall mean that marketing plan which
has been agreed to by the parties and which sets forth the marketing strategy
and tactics to be used in promoting ELDEPRYL Brand to Key Prescribers during the
Term.  The Key Prescriber Marketing Plan may be adjusted from time-to-time
pursuant to Section  3.1(b)(ii).

   1.21  "MANAGING COMMITTEE" shall mean the committee established pursuant to
Section 3.1 which is responsible for oversight of the co-promotion relationship
between CoCensys and Somerset in the Territory, including, but not limited to,
the marketing, advertising and promotion of ELDEPRYL Brand pursuant to this
Agreement.

   1.22  "MINIMUM AGGREGATE MONTHLY DETAILS" shall be equal to:


             [   *   ], at the conclusion of the first month of the Term; or

             [   *   ], at the conclusion of the second month of the Term; or


                                          5.

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             [   *   ], at the conclusion of the third month of the Term; or

             [   *   ], at the conclusion of the fourth month of the Term; or

             [   *   ], at the conclusion of the fifth month of the Term; or

             [   *   ], at the conclusion of the sixth month of the Term; or

             [   *   ], at the conclusion of the seventh month of the Term; or

             [   *   ], at the conclusion of the eighth month of the Term; or

             [   *   ], at the conclusion of the ninth month of the Term; or

             [   *   ], at the conclusion of the tenth month of the Term; or

             [   *   ], at the conclusion of the eleventh month of the Term; or

             [   *   ], at the conclusion of the twelfth month of the Term.


   1.23  "MINIMUM AGGREGATE QUARTERLY DETAILS" shall be equal to:

             [   *   ], at the conclusion of the first quarter of the Term; or

             [   *   ], at the conclusion of the second quarter of the Term; or

             [   *   ], at the conclusion of the third quarter of the Term; or

             [   *   ], at the conclusion of the fourth quarter of the Term.


                                          6.

* Confidential treatment requested
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   1.24  "MONTHLY DETAIL PAYMENT" shall have the meaning set forth in Section
7.1(a)(ii).

   1.25  "MONTHLY DETAIL PAYMENT REDUCTION" shall have the meaning set forth in
Section 7.1(b)(ii).

   1.26  "NDA" shall mean an FDA-approved new drug application.

   1.27  "PROMOTIONAL MATERIALS" shall have the meaning set forth in
Section 5.5.

   1.28  "PROPRIETARY INFORMATION" shall mean any proprietary or confidential
information communicated by one party hereto to the other, whether in written,
electronic, graphic or oral form, which is so identified as proprietary or
confidential by the disclosing party, or which the receiving party knows or has
reason to know is proprietary or confidential including, but not limited to,
financial, marketing, business, technical or scientific information or data. 

   1.29  "QUARTERLY DETAIL PAYMENT" shall have the meaning set forth in Section
7.1(a)(i).

   1.30  "QUARTERLY DETAIL PAYMENT REDUCTION" shall have the meaning set forth
in Section 7.1(b)(i).

   1.31  "SAMPLE" shall mean complimentary supply of ELDEPRYL Brand capsules or
other dosage forms which are distributed by the CoCensys ELDEPRYL Sales Force to
Key Prescribers, pursuant to the provisions of the Prescription Drug Marketing
Act.


                                          7.
<PAGE>

   1.32  "TARGET AGGREGATE MONTHLY DETAILS" shall be equal to:

             [   *   ], at the conclusion of the first month of the Term; or

             [   *   ], at the conclusion of the second month of the Term; or

             [   *   ], at the conclusion of the third month of the Term; or

             [   *   ], at the conclusion of the fourth month of the Term; or

             [   *   ], at the conclusion of the fifth month of the Term; or

             [   *   ], at the conclusion of the sixth month of the Term; or

             [   *   ], at the conclusion of the seventh month of the Term; or

             [   *   ], at the conclusion of the eighth month of the Term; or

             [   *   ], at the conclusion of the ninth month of the Term; or

             [   *   ], at the conclusion of the tenth month of the Term; or

             [   *   ], at the conclusion of the eleventh month of the Term; or

             [   *   ], at the conclusion of the twelfth month of the Term.



   1.33  "TARGET AGGREGATE QUARTERLY DETAILS" shall be equal to:

             [   *   ], at the conclusion of the first quarter of the Term; or

             [   *   ], at the conclusion of the second quarter of the Term; or


                                          8.
<PAGE>

             [   *   ], at the conclusion of the third quarter of the Term; or

             [   *   ], at the conclusion of the fourth quarter of the Term.


   1.34  "TERM" shall mean the period commencing on the Effective Date and
terminating December 31, 1997, unless terminated earlier pursuant to the
provisions of Article 8. 


   1.35  "TERRITORY" shall mean the United States of America, the District of
Columbia and Puerto Rico, but not any other United States territories or
possessions.

   1.36  "TOTAL ACTUAL DETAILS" shall equal the total number of ELDEPRYL
Details conducted by the CoCensys ELDEPRYL Sales Force from the Effective Date
to the date of calculation.  "Total Actual Details" shall be calculated (i) as
of the last day of each calendar quarter during the Term; or, (ii)  in the event
this Agreement terminates prior to December 31, 1997, as of the last day of each
month during the quarter in which such termination occurs and as of the
effective date of termination.

   1.37  "TOTAL DETAIL PAYMENT REDUCTION" shall equal the sum of [   *   ] if
any, made to date and shall be calculated (i) at the conclusion of the Term, or
(ii) in the event of termination prior to December 31, 1997, as of the effective
date of termination.


                                          9.

* Confidential treatment requested
<PAGE>

   1.38  "TOTAL GOVERNMENT DISCOUNTS AND REBATES" shall mean all government
mandated discounts and rebates on sales of ELDEPRYL Brand in the Territory
during the Term.

                                      ARTICLE 2

                                   PROMOTION RIGHTS

   2.1   APPOINTMENT OF COCENSYS.  Subject to Section 4.6, Somerset hereby
appoints CoCensys, effective on the Effective Date and throughout the Term, as
its exclusive agent to detail ELDEPRYL Brand to Key Prescribers in the
Territory, in accordance with this Agreement.  In addition, Somerset hereby
appoints CoCensys, as of the Effective Date and throughout the Term, as a
non-exclusive agent to promote ELDEPRYL Brand in the Territory to those third
parties whom CoCensys's regional business directors meet with in the normal
course of their business, in accordance with this Agreement.

   2.2   RIGHTS RETAINED BY SOMERSET.  Except as otherwise expressly provided
in this Agreement, Somerset shall be responsible for maintaining (or, to the
extent permissible under existing contracts with third parties, causing such
third parties to maintain) all rights in and to ELDEPRYL Brand including, but
not limited to, the NDA(s) for ELDEPRYL Brand, the drug master file(s) for
ELDEPRYL Brand, and all manufacturing, distribution, patent, copyright and
trademark rights relating to ELDEPRYL Brand.


                                         10.
<PAGE>

                                      ARTICLE 3

                  MANAGING COMMITTEE; KEY PRESCRIBER MARKETING PLAN

   3.1   MANAGING COMMITTEE.

         (a)  FORMATION; MEETINGS.  The Managing Committee will be responsible
for all decisions regarding the marketing, advertising and promotion of ELDEPRYL
Brand to Key Prescribers in the Territory.  Somerset and CoCensys shall each
appoint one (1) person as voting members of the Managing Committee, who will
have expertise in marketing or sales.  Each person will have experience which is
relevant to the promotion of ELDEPRYL Brand contemplated by this Agreement. 
Somerset and CoCensys may from time to time each replace their respective voting
representatives on the Managing Committee upon one (1) month prior written
notice to the other party.  In addition, each party may bring any non-voting
representatives to meetings of the Managing Committee.  Each party will ensure
that at least one of its employees who has experience sufficient to monitor and
coordinate the payments to be made between the parties hereunder will be
available in person or by telephone for each meeting of the Managing Committee. 
The Managing Committee will meet quarterly, or more or less often as the
Managing Committee determines to be appropriate.  Such meetings shall be
scheduled at mutually convenient times in places alternately selected by
Somerset and CoCensys.  Each party will bear its own costs for attendance at
Managing Committee meetings.  Any member may designate an alternate to act on
his or her behalf at any meetings by notice (which may be oral) to the other
members, said right not to be exercised more than two (2) times per year by each
such member.  Any member of the Managing Committee may request a meeting 


                                         11.
<PAGE>

of the Managing Committee by giving written notice of such meeting at least
fourteen (14) days before the desired date of such meeting.  Any disputes within
the Managing Committee will be resolved pursuant to Section 3.2 hereof.

         (b)  FUNCTIONS OF THE MANAGING COMMITTEE.  The Managing Committee will
perform the following functions:

              (i)     establish guidelines to govern the promotion of ELDEPRYL
                      brand by CoCensys.

              (ii)    review, comment upon and approve adjustments to the Key
                      Prescriber Marketing Plan.

              (iii)   monitor whether third party or governmental actions (e.g.
                      third party publication, FDA mandated labeling change,
                      new discovery, new product on the market, infringement of
                      trademark rights) are having, or are likely to have, a
                      material effect on Actual Gross Sales and suggest
                      adjustments to the Key Prescriber Marketing Plan and/or
                      recommend to the parties amendments to this Agreement to
                      respond to such third party or governmental actions.

              (iv)    in accordance with section 7.3, make recommendations to
                      the parties in the event of material increases in Total
                      Government Discounts and Rebates.

              (v)     approve the target list of Key Prescribers, the initial
                      version of which has already been approved by the
                      parties.  In addition, upon 


                                         12.
<PAGE>

                      approval of the Managing Committee, physicians may, from
                      time to time, be added to or deleted from the list of Key
                      Prescribers.

              (vi)    determine whether and when the CoCensys ELDEPRYL Sales
                      Force should provide Samples to Key Prescribers.

              (vii)   otherwise monitor and oversee the promotion and marketing
                      of ELDEPRYL Brand to physicians in the Territory and the
                      relationship of the parties hereunder.

   3.2   DISPUTE RESOLUTION.  In the event of a disagreement between the
parties as to any matters within the scope of the responsibilities of the
Managing Committee, the Managing Committee will, diligently and in good faith,
seek to resolve the matter in dispute.  If the Managing Committee is unable to
resolve the dispute, despite its good faith efforts, within thirty (30) days of
first addressing the matter, it shall, within ten (10) days thereafter, refer
such dispute to the President of CoCensys and the President of Somerset who will
discuss and attempt to resolve the dispute.  If the Presidents of the parties
are unable to resolve the dispute, the President of Somerset shall have ultimate
authority to resolve all matters within the scope of the responsibilities of the
Managing Committee, except for those matters set forth in Sections 1.19 and
3.1(b)(v).


                                         13.
<PAGE>

                                       ARTICLE 4.

                             PROMOTION OF ELDEPRYL BRAND

   4.1   COCENSYS ELDEPRYL SALES FORCE.  During the Term, subject to review and
approval by the Managing Committee and consistent with the Key Prescriber
Marketing Plan, CoCensys shall deploy the CoCensys ELDEPRYL Sales Force for the
delivery of ELDEPRYL Details to the Key Prescribers.  [     *     ].

   4.2   TRAINING OF COCENSYS ELDEPRYL SALES FORCE.

         (a)  CONTINUED TRAINING.  Subsequent to the Effective Date, Somerset
may invite the CoCensys ELDEPRYL Sales Force to attend any training sessions
which are provided by Somerset for the purpose of upgrading information relating
to sales of ELDEPRYL Brand, including, but not limited to, information relating
to new developments as set forth in Section 5.6.  It is understood that such
training sessions (i) will be provided on an as-needed basis by Somerset after
discussions between CoCensys and Somerset regarding the content and format of
such sessions and (ii) are subject to the approval of the Managing Committee. 
Somerset may require some or all of the CoCensys ELDEPRYL Sales Force to attend
certain training sessions ("Mandatory Training Sessions").

         (b)  TRAINING COSTS.  All costs incurred under Section 4.2(a) shall be
subject to prior approval by the Managing Committee.  All costs incurred under
Section 4.2(a) 


                                         14.

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<PAGE>

(including but not limited to, training costs, transportation, and room and
board) for Mandatory Training Sessions will be borne [     *     ].  All costs
incurred under Sections 4.2(a)  (including, but not limited to, training costs,
transportation and room and board) for any other training will be borne
[     *     ].

    4.3  COCENSYS ELDEPRYL SALES FORCE SUPPORT.  CoCensys will, [     *     ]
employ a product segment manager and appropriate secretarial support to
implement its obligations under this Agreement.

    4.4  CONDUCT OF THE COCENSYS ELDEPRYL SALES FORCE.  In accordance with the
Key Prescriber Marketing Plan and the terms and conditions of this Agreement,
and subject to the Federal Food, Drug and Cosmetic Act, all regulations
promulgated pursuant thereto and any and all applicable state laws and
regulations, CoCensys shall use commercially diligent efforts to direct its
CoCensys ELDEPRYL Sales Force to detail ELDEPRYL Brand to the Key Prescribers to
so persuade such Key Prescribers to prescribe and use ELDEPRYL Brand.  The
CoCensys ELDEPRYL Sales Force shall conduct ELDEPRYL Details, shall execute the
programs set forth in the Key Prescriber Marketing Plan and, where deemed
appropriate by the Managing Committee, shall provide Samples to Key 
Prescribers.  Somerset may, from time to time and upon reasonable prior notice,
request that a Somerset employee be allowed to join the CoCensys ELDEPRYL Sales
Force for certain ELDEPRYL Details.  Upon the authorization of CoCensys sales
management, such authorization not to be unreasonably withheld, CoCensys will


                                         15.

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<PAGE>

accommodate such request, provided that [          *          ] associated with
its employee engaging in such activity.  In addition CoCensys will cause its
regional business directors to make presentations regarding ELDEPRYL Brand to
those third parties with whom such regional business directors meet in the
normal course of their business.  All presentations and materials to be utilized
by CoCensys to so market, advertise or promote ELDEPRYL Brand shall be subject
to the prior review of Somerset and, if applicable, the FDA.  CoCensys shall
cause the CoCensys ELDEPRYL Sales Force, and all other employees, agents and
representatives of CoCensys, to comply with all applicable laws, regulations and
guidelines in connection with the marketing, advertising and promotion of
ELDEPRYL Brand, including the Prescription Drug Marketing Act and the Federal
Anti-Kickback Statute.

    4.5  BONUS PROGRAM FOR COCENSYS ELDEPRYL SALES FORCE.  [     *     ] an
incentive cash bonus program for the CoCensys ELDEPRYL Sales Force.  The amount
of [     *     ] to be made available for distribution through such bonus
program (the "Bonus Pool") will be determined by [          *          ].  The
size of the Bonus Pool for the second six months of the Term shall be determined
by [          *          ] during such period.   Notwithstanding the foregoing,
[          *          ]. [          *          ] establish the criteria to be
used in dividing the Bonus Pool among the CoCensys ELDEPRYL Sales Force. 
[        *          ] adjust the specific bonus amounts to be paid to individual
members of the


                                         16.

* Confidential treatment requested
<PAGE>

CoCensys ELDEPRYL Sales Force in order to reflect the ELDEPRYL Brand sales
efforts of such individuals; provided, however, that [          *          ]
documentation which lists the names of the recipients and the amount of the
bonus he/she received.  [          *          ].

    4.6  OTHER MARKETING ACTIVITIES TO PHYSICIANS.

              (a)  PHYSICIANS WHO ARE NOT KEY PRESCRIBERS.  During the Term
hereof, CoCensys may, at its sole discretion, make sales calls or presentations
regarding ELDEPRYL Brand to physicians in the Territory who are not Key
Prescribers.

              (b)  NON-SALES CALL ACTIVITY.  During the Term hereof, Somerset
will not make sales calls regarding ELDEPRYL Brand to Key Prescribers in the
Territory.  Somerset may, however, engage in other (i.e. non-sales call)
marketing, advertising or promotion activities for ELDEPRYL Brand directed at
neurologists or other physicians in the Territory, provided that all of the
foregoing activities will be funded in full by Somerset.  Somerset agrees to
notify CoCensys of any such other activities.

    4.7  OTHER USES OF COCENSYS SALES FORCE.  Somerset acknowledges and
understands that CoCensys has certain obligations relating to the deployment of
the CoCensys ELDEPRYL Sales Force pursuant to a promotion agreement which is on
file with the United States Securities and Exchange Commission as of the date of
execution of this Agreement.  CoCensys represents and warrants that, as of the
Effective Date, there are at least [     *     ] members of the


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CoCensys ELDEPRYL Sales Force and that, during the Term, the CoCensys ELDEPRYL
Sales Force will only be utilized to deliver to Key Prescribers (i) a 
[     *    ] Presentation for a [     *     ] pharmaceutical product and (ii)
an ELDEPRYL Detail.  CoCensys further represents and warrants that the size of
the CoCensys ELDEPRYL Sales Force will not fall below [     *     ] in number 
except as a result of attrition, in which event CoCensys will, within sixty 
(60) days of the date upon which the size of the CoCensys ELDEPRYL Sales Force
fell below [     *    ] hire additional salespeople to replace those lost 
through attrition and to cause the size of the CoCensys ELDEPRYL Sales Force
to number at least [     *    ] Provided that the CoCensys ELDEPRYL Sales Force
is comprised of at least [    *     ] CoCensys sales representatives and 
provided that CoCensys continues to meet all of its obligations hereunder, in
the event that CoCensys increases the size of its overall sales force to more
than [     *     ] sales representatives, CoCensys shall have the right, in its
sole discretion and upon prior written notice to Somerset and after 
consultation with Somerset, to utilize those members of its sales force who are
not members of the CoCensys ELDEPRYL Sales Force to market, advertise, promote
or otherwise sell other pharmaceutical products to neurologists.  
Notwithstanding the foregoing, during the Term, CoCensys will not promote any
pharmaceutical product, other than ELDEPRYL Brand, with an approved indication
for Parkinson's disease without the prior written consent of Somerset.


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    4.8  NUMBER OF ELDEPRYL DETAILS.   CoCensys represents that the CoCensys
ELDEPRYL Sales Force will present at least [     *     ] ELDEPRYL Details per
calendar quarter. Failure to deliver the full [     *     ] ELDEPRYL Details per
calendar quarter shall not be deemed a material breach of, or failure to perform
under, this Agreement, PROVIDED, HOWEVER, if, in any calendar quarter, CoCensys
fails to deliver the Minimum Aggregate Quarterly Details, and such failure was
not caused by an event of force majeure, then Detail-Based Compensation for such
calendar quarter shall be adjusted pursuant to Section 7.1(b)(i).

    4.9  RECORDS AND REPORTS REGARDING PROMOTION ACTIVITIES.  CoCensys will
keep complete and accurate records of the ELDEPRYL Details made by the CoCensys
ELDEPRYL Sales Force (including numbers of ELDEPRYL Details, names of Key
Prescribers, date of presentation and general response to such presentations)
and the other activities carried out pursuant to the Key Prescriber Marketing
Plan.  CoCensys will provide Somerset a quarterly report summarizing such
matters.  CoCensys will maintain such records for three (3) years following the
period to which they relate.  CoCensys shall permit Somerset to have such
records examined by independent certified public accountants retained by
Somerset and acceptable to CoCensys, during regular business hours and upon
reasonable advance notice, but not later than three (3) years following the date
of any such records and no more often than one (1) time per year.  Such
independent accountants shall, pursuant to separate written contract, keep
confidential any information obtained during such examination and shall report
to Somerset only the number of ELDEPRYL Details per quarter.  Any such
information so reviewed and any such information reported shall be considered
the Proprietary Information of CoCensys.  In the


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absence of material discrepancies (in excess of [     *     ] of the total
number of ELDEPRYL Details required of CoCensys for such quarter) in any request
for a refund resulting from such audit, the accounting expense shall be paid by
Somerset.  If material discrepancies do result, CoCensys shall bear the
accounting expense.  Any amounts due to Somerset arising from such discrepancies
shall be paid by CoCensys within ten (10) business days of receipt by CoCensys
of a written notice from Somerset that such discrepancies exists.  Somerset will
keep complete and accurate records of the activities carried out by Somerset
pursuant to the Key Prescriber Marketing Plan.  Somerset will make such records
available to CoCensys during Somerset's regular business hours and will provide
CoCensys a quarterly report summarizing such matters.  Somerset will maintain
such records for three (3) years following the period to which they relate.

    4.10  FORWARDING OF ELDEPRYL BRAND ORDERS.  Any orders for ELDEPRYL Brand
received by CoCensys, including members of the CoCensys ELDEPRYL Sales Force,
will be promptly forwarded to Somerset.

                                       ARTICLE 5.
                           SOMERSET RIGHTS AND OBLIGATIONS

    5.1   [     *     ] MARKETING RESPONSIBILITY.  Except as explicitly set
forth in this Agreement, Somerset shall be responsible for 
[         *         ].


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    5.2   SUPPLY AND DISTRIBUTION OF ELDEPRYL BRAND.  In accordance with
Somerset's general business practices, Somerset shall use commercially diligent
efforts to perform, or cause to be performed, all manufacturing, labeling,
packaging, warehousing, maintenance of inventory, distribution, order entry,
customer services and all other activities to supply and distribute ELDEPRYL
Brand in order to fill the orders generated by the activities of CoCensys
hereunder and to supply and distribute Samples in accordance with Section 6.2. 
Somerset shall accept orders for ELDEPRYL Brand in accordance with Somerset's
general business practices.

    5.3   REGULATORY COMPLIANCE.  Unless otherwise required by law, Somerset
will retain exclusive authority and responsibility for complying with all
regulatory requirements and maintaining all government agency contacts relating
to ELDEPRYL Brand, including, but not limited to, maintaining and updating the
NDA(s) for ELDEPRYL Brand; [          *          ] the reporting of any adverse
drug reactions to the FDA; the filing of Promotional Materials with the FDA; and
the payment of Medicaid and other governmental rebates which in Somerset's sole
judgment are due and owing.  Nothing herein shall obligate Somerset 
[          *         ].

    5.4   PRODUCT RECALL.  In the event that (i) Somerset determines that an
event, incident or circumstances has occurred which may result in the need for a
recall or other removal of ELDEPRYL Brand or any lot or lots thereof from the
market in the Territory, (ii) the FDA requires a recall of ELDEPRYL Brand or
(iii) the FDA requires distribution of a "Dear Doctor" letter, Somerset shall
promptly advise CoCensys with respect thereto.  With respect to clause (i)
above, Somerset shall, in its sole discretion, have the right to order a recall
or other removal


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after such notification.  With respect to clauses (ii) and (iii) above, Somerset
shall order such recall or distribute such "Dear Doctor" letter after such
notification.  [          *          ].

    5.5   PROMOTIONAL MATERIALS.

          (a) SOMERSET MATERIALS.  In accordance with the Key Prescriber
Marketing Plan, Somerset shall, [     *     ] produce, provide and ship to
CoCensys reasonable quantities of promotional, sales, marketing and educational
materials for ELDEPRYL Brand (the "Promotional Materials") to allow CoCensys to
fulfill its obligations hereunder.  Such Promotional Materials shall include, by
way of example, promotional brochures, videos, visual aids, approved reprints,
medically relevant reminder items, continuing medical education programs,
patient education and compliance programs, medical literature, medical group
presentations, market research and direct mail programs.  All Promotional
Materials will be approved by the medical and regulatory departments of
Somerset.  In addition to the foregoing, Somerset shall provide CoCensys with
two (2) copies of each item of Promotional Material for CoCensys's archives.

          (b) RIGHTS TO PROMOTIONAL MATERIALS.  As between Somerset and
CoCensys, Somerset shall own all right, title and interest in and to any
Promotional Materials provided to CoCensys pursuant to this Section 5.5
including applicable copyrights and trademarks.  Somerset hereby grants to
CoCensys the right, during the Term, to use all Promotional Materials and all
sales, marketing, educational and training materials produced by Somerset and
supplied to


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CoCensys with respect to ELDEPRYL Brand in conjunction with CoCensys's promotion
of ELDEPRYL Brand.

    5.6   [     *     ] DEVELOPMENTS RELATING TO ELDEPRYL BRAND.  Somerset
will promptly inform CoCensys of the following information relating to ELDEPRYL
Brand: (i) [          *          ] (ii) [          *          ] (iii) 
[          *          ] and (iv) any changes in regulations affecting
ELDEPRYL Brand or Somerset's obligations with respect to this Agreement. 
CoCensys will promptly inform Somerset of information relating to changes in
regulations affecting CoCensys' obligations with respect to this Agreement. 
Based on such information, and subject to any federal, state or local laws
and/or regulations, Somerset shall use commercially diligent efforts to maintain
the training materials supplied to CoCensys pursuant to this Agreement current
with such [     *     ] information.

    5.7   SALES AND INVENTORY DATA.  Somerset will provide CoCensys with a
report of overall sales of ELDEPRYL Brand in the Territory, in Somerset's
standard sales report format, a copy of which is attached hereto as Exhibit 5.7,
for each month of the Term as it becomes available to Somerset in the normal
course of business.  Somerset shall also provide CoCensys with a report of
inventories and back orders of ELDEPRYL Brand.


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    5.8   SOMERSET COSTS.  Except as specifically set forth in this Agreement,
[          *          ] in accordance with the marketing budget which has been
established for the Term.  In the event [     *     ] are materially affecting
sales of ELDEPRYL Brand, Somerset may, after notification to CoCensys, 
[     *    ] to respond to such [     *     ].

                                      ARTICLE 6.
                                  JOINT OBLIGATIONS

    6.1   ASSISTANCE AND NOTIFICATIONS TO OTHER PARTY.  Each party agrees to
provide to the other reasonable assistance and take actions reasonably requested
by the other party that are necessary to enable the other party to comply with
its obligations hereunder and with any law or regulation applicable to ELDEPRYL
Brand, including, but not limited to, Somerset's meeting its reporting and other
obligations under Section 5.3.  Such assistance and actions shall include, among
other things:  (i) CoCensys promptly reporting to Somerset adverse drug
reactions of which it becomes aware, so as to permit Somerset to meet its FDA
reporting and other obligations in a timely fashion; (ii) Somerset carrying out
any FDA-mandated notifications relating to ELDEPRYL Brand; (iii) Somerset
immediately notifying CoCensys of any inquiry or other contact by the FDA or any
other governmental agency or authority with Somerset or its Affiliates relating
to ELDEPRYL Brand, except that Somerset will notify CoCensys only of such
inquiries or contacts which may materially affect CoCensys's performance of its
obligations relating to ELDEPRYL Brand under this Agreement or which may
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ability to manufacture and supply ELDEPRYL Brand; and (iv) Somerset promptly
notifying CoCensys of any adverse drug reactions to ELDEPRYL Brand or any
regulatory action with respect to ELDEPRYL Brand.  Somerset will make available
to CoCensys all FDA-authorized procedures and forms necessary for CoCensys to
meet its obligations hereunder.

    6.2  SAMPLES OF ELDEPRYL BRAND.

         (a)  COSTS.  Pursuant to Section 3.1(b)(vi) hereof, the Managing
Committee may determine that the CoCensys ELDEPRYL Sales Force should provide
Samples of ELDEPRYL Brand to some or all Key Prescribers.  Upon such
determination, Somerset shall make Samples of ELDEPRYL Brand available to
CoCensys in such amounts and at such times as may be determined by the Managing
Committee.  Samples will be shipped to the one or more locations designated by
CoCensys by written notice to Somerset.  Sample distribution and accountability
will be administered by Somerset.

         (b)  SHRINK-WRAP.  All Samples shall be encased in shrink-wrap and
packaged appropriately to comply with FDA packaging requirements.

         (c)  DISPOSITION UPON TERMINATION.  Within thirty (30) days after the
end of the Term, or other earlier termination date, CoCensys shall return, or
otherwise dispose of in accordance with written instructions from Somerset, all
remaining Samples provided by Somerset and will provide Somerset with a
certified statement that CoCensys has utilized commercially diligent efforts to
ensure that, to the best of CoCensys's knowledge, all remaining Samples have


                                         25.
<PAGE>

been returned or otherwise properly disposed of and that CoCensys is no longer
in possession or control of any such Samples in any form or fashion.

    6.3  REQUESTS FOR INFORMATION FROM KEY PRESCRIBERS.  The parties
acknowledge that each may receive requests for medical or technical information,
or reports of adverse drug reactions, concerning ELDEPRYL Brand from Key
Prescribers and others.  The parties agree that it shall be the obligation of
Somerset to so respond and/or report, as appropriate, and CoCensys shall ensure
that its employees and agents comply with Somerset's adverse event reporting
procedures and policies.


    6.4  MARKET SURVEYS.  Each party hereto may, at its discretion and expense,
undertake such market surveys, research or analyses relating to ELDEPRYL Brand
as it deems fit, and such surveys, research or analyses shall remain the
property of the party undertaking same.  Each party shall make such surveys,
research and analyses specifically relating to ELDEPRYL Brand available to the
other party at no cost to that other party.  Somerset may request that CoCensys
undertake market surveys, research or analyses relating to ELDEPRYL Brand and
CoCensys may, in its sole discretion, elect to undertake such surveys, research
or analyses.  [          *          ].

    6.5  WITHDRAWAL OF ELDEPRYL BRAND.  Each party agrees to notify the other
immediately of any pending or threatened event which may lead to withdrawal of
ELDEPRYL Brand from the market, including, without limitation; (i) actual or
threatened regulatory action


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by the FDA or other governmental entity, including, but not limited to, the loss
by Somerset of any right necessary to market ELDEPRYL Brand; or (ii) safety
concerns relating to ELDEPRYL Brand.  The final decision as to whether to so
withdraw ELDEPRYL Brand shall be within Somerset's sole discretion.  In the
event of such withdrawal of ELDEPRYL Brand, the rights of the parties shall be
governed by Section 8.3 hereof.


    6.6  NON-SOLICITATION OF EMPLOYEES.  During the Term, neither party will
solicit for the purpose of hiring the sales and marketing employees of the other
party.

                                      ARTICLE 7.

                                     COMPENSATION

    7.1  DETAIL-BASED COMPENSATION.

         (a)  DETAIL PAYMENTS.

              (i)  Subject to the terms and conditions of this agreement, as
                   compensation for the ELDEPRYL Details to be made each
                   calendar quarter by the CoCensys ELDEPRYL Sales Force during
                   the calendar year 1997, Somerset shall pay 
                   [          *          ] ("Detail-Based Compensation") to 
                   CoCensys. Detail-Based Compensation shall be due and 
                   payable in four (4) equal quarterly installments of 
                   [          *          ] for each calendar quarter


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                   during the Term ("Quarterly Detail Payment") (unless subject
                   to adjustment under Sections 7.1 (a) (ii) or 7.1 (b)).
                   CoCensys acknowledges that, prior to the date of execution
                   of this Agreement it received [     *     ] of the first
                   Quarterly Detail Payment due hereunder.  The [     *     ]
                   balance of the first Quarterly Detail Payment shall be made
                   within 5 days after the execution of this Agreement by both
                   parties, and each subsequent Quarterly Detail Payment shall
                   be made on April 1, 1997, July 1, 1997 and October 1, 1997.

              (ii) In the event that a notice of termination is given by either
                   party pursuant to Section 8 hereof, then commencing on the
                   first day of the calendar quarter following the calendar
                   quarter for which the last Quarterly Detail Payment has been
                   made, (if the effective date of such termination has not yet
                   occurred) Detail-Based Compensation shall be paid, until the
                   effective date of termination, on a monthly basis on the
                   first day of each month and shall be in the amount of 
                   [     *     ] (unless subject to adjustment under 
                   Section 7.1 (b)(ii)) ("Monthly Detail Payment").  The final 
                   Monthly Detail Payment shall be paid on a pro-rata basis in 
                   the event that the effective date of termination does not 
                   occur on the final day of any calendar month.


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         (b)  REDUCTION IN DETAIL PAYMENTS.

              (i)  Commencing with the first quarter of the Term, not later
                   than thirty (30) days after the end of each quarter during
                   the Term, CoCensys will send to Somerset a statement
                   indicating the number of ELDEPRYL Details made by the
                   CoCensys ELDEPRYL Sales Force during each such completed
                   quarter ("Actual Quarterly Details") and shall compute the
                   Total Actual Details as of the last day of the completed
                   quarter in the manner provided in Section 1.36.  In the
                   event that Total Actual Details as of the end of such
                   quarter are less than the Minimum Aggregate Quarterly
                   Details for such quarter as set forth in Section 1.23,
                   Somerset shall be entitled to a "Quarterly Detail Payment
                   Reduction".  The Quarterly Detail Payment Reduction for such
                   quarter shall be equal to [     *     ] where

                   A =  [     *     ] (applicable to the end of such quarter)
                        minus [     *     ] (through the end of such quarter);
                        and
                   B =  the [     *     ] paid to Somerset by CoCensys, if any,
                        for any prior quarters of the Term.

                   CoCensys shall pay to Somerset such Quarterly Detail Payment
                   Reduction with delivery of the statement indicating the
                   Actual


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                   Quarterly Details.  If payment is not received, Somerset may
                   deduct any Quarterly Detail Payment Reduction from any
                   future Quarterly Detail Payment or any other payment due to
                   CoCensys by Somerset.

              (ii) In the event that any Monthly Detail Payment is due pursuant
                   To Section 7.1 (a) (ii) hereof, CoCensys shall be required,
                   within 30 days after the end of the month, to provide
                   Somerset with a statement indicating the number of ELDEPRYL
                   Details made by the CoCensys ELDEPRYL Sales Force during
                   each such month or portion thereof ("Actual Monthly
                   Details").  CoCensys shall include on the statement the
                   number of Total Actual Details completed as of the end of
                   such month as set forth in Section 1.36.  In the event that
                   Total Actual Details are not equal to or greater than the
                   Minimum Aggregate Monthly Details for the period upon which
                   Total Actual Details are based, as defined in Section 1.22,
                   Somerset shall be entitled to a "Monthly Detail Payment
                   Reduction."  The Monthly Detail Payment Reduction for a
                   given month shall be equal to [     *     ], where

                   C =  [     *     ] (applicable to the end of such month)
                        minus [          *          ] (through the end of such
                        month); and


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                   D =  the [          *          ] if any, for any prior
                        months of the Term.

                        CoCensys shall pay to Somerset such Monthly Detail
                        Payment Reduction with delivery of the statement
                        indicating the Actual Monthly Details.  If payment is
                        not received, Somerset may deduct any Monthly Detail
                        Payment Reduction from any future Monthly Detail
                        Payment or any other payment due to CoCensys by
                        Somerset.

         (c)  DETAIL-BASED COMPENSATION RECONCILIATION.

              (i)  At the conclusion of the full Term, Somerset shall calculate
                   the Total Actual Details for the entire Term and Total
                   Detail Payment Reduction for the entire Term, if any, in the
                   manner provided in Sections 1.36 AND 1.37 respectively.  In
                   the event that Total Actual Details are equal to or greater
                   than [     *     ], then Somerset shall reimburse to
                   CoCensys the amount of the Total Detail Payment Reduction,
                   if any, previously paid by CoCensys.   In the event that the
                   Total Actual Details are less than [     *     ], Somerset
                   shall calculate the "Annualized Detail Payment


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                   Reduction" by multiplying [          *          ].  If the
                   Annualized Detail Payment Reduction is less than the Total
                   Detail Payment Reduction for the entire Term, 
                   [          *          ].  If the Annualized Detail Payment
                   Reduction is equal to the Total Detail Payment Reduction,
                   then Somerset shall [          *          ].  If the 
                   Annualized Detail Payment Reduction is greater than the 
                   Total Detail Payment Reduction, then CoCensys shall pay to 
                   Somerset an amount equal to [          *          ] The 
                   Detail-Based Compensation Reconciliation Payment, if any, 
                   shall be made no later than February 10, 1998.

              (ii) In the event that this Agreement is terminated prior to the
                   conclusion of the Term, Somerset shall calculate Total
                   Actual Details as of the termination date and Total Detail
                   Payment Reduction as of the termination date in the manner
                   provided in Sections 1.36 AND 1.37 respectively.  In
                   addition, "Adjusted Target Details" shall be calculated in
                   the following manner: Adjusted Target Details = 
                   [     *     ].  In the event that the Total Actual Details 
                   are equal to or greater than the Adjusted Target Details, 
                   [          *          ].  In the event that the Total Actual
                   Details are less than the Adjusted Target Details, 
                   [          *          ].  If the


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                   Adjusted Annualized Detail Reduction is less than the Total
                   Detail Payment Reduction, [          *          ].  If the
                   Adjusted Annualized Detail Payment Reduction is equal to the
                   Total Detail Payment Reductions, [          *          ].  If
                   the Adjusted Annualized Detail Payment Reduction is greater
                   than the Total Detail Payment Reduction, then 
                   [          *          ].  The Adjusted Detail-Based 
                   Compensation Reconciliation Payment shall be made no later 
                   than February 10, 1998.

         (d)  Examples of Detail-Based Compensation, under different
              hypothetical sales scenarios, are set forth on Exhibit 7.1 (d).

    7.2  GROSS SALES-BASED COMPENSATION.

         (a)  No later than February 10, 1998, Somerset shall send CoCensys a
              statement setting forth Actual Gross Sales of ELDEPRYL Brand and
              shall pay to CoCensys, with delivery of the statement indicating
              the Actual Gross Sales, the amount of compensation listed on
              Exhibit 7.2 (the "Gross Sales-Based Compensation"), so long as
              CoCensys' ELDEPRYL Sales Force provided services to Somerset
              through December 31, 1997.


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         (b)  In the event that this Agreement is terminated by either party
              prior to the end of the Term, then all amounts listed on Exhibit
              7.2 shall be adjusted [          *          ].  No later than
              February 10, 1998, Somerset shall send CoCensys a statement
              setting forth Actual Gross Sales through the effective date of
              termination of the Agreement and shall pay to CoCensys, with
              delivery of the statement indicating such Actual Gross Sales, the
              amount of Gross Sales-Based Compensation listed on Exhibit 7.2 as
              hereby adjusted.

         (c)  In the event that Somerset terminates this Agreement under
              Section 8.4 below (Termination for Breach), Somerset may 
              [         *          ].  No later than February 10, 1998 
              following such early termination, Somerset shall send CoCensys a 
              statement setting forth Actual Gross Sales, a revised Exhibit 7.2
              (as adjusted under Section 7.2 (b)) and any offset permitted 
              under this Section 7.2 (c) and shall pay to CoCensys, with 
              delivery of the statement indicating such amounts, the amount of
              Gross Sales-Based Compensation listed on the revised Exhibit 7.2,
              as adjusted pursuant to this Section 7.2 (c).

         (d)  The parties acknowledge and understand that the outcome of
              certain litigation, currently pending in the United States
              District Court, District of Delaware entitled SOMERSET
              PHARMACEUTICALS, INC. V. SHALALA, ET AL.,


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        Docket No. 96-403-SLR, may materially affect the sales of ELDEPRYL 
        Brand without regard to the efforts of CoCensys' ELDEPRYL Sales 
        Force.  In the event such litigation results in rescission or 
        suspension of FDA approval for any of the generic ELDEPRYL Brand 
        products or otherwise results in a significant reduction of the 
        competitive forces in the marketplace for ELDEPRYL Brand, then the 
        parties shall immediately commence good faith negotiations to amend 
        Exhibit 7.2 in order [          *          ] so that Gross 
        Sales-Based Compensation continues to reflect the marketing efforts 
        of CoCensys and not increased sales arising from the results of 
        such litigation.  The parties will use reasonable efforts to 
        complete such good faith negotiations promptly; PROVIDED, HOWEVER, 
        in the event the good faith negotiations described in the preceding 
        sentence are not completed as of February 1, 1998, Somerset shall 
        not be obligated to make the payment to CoCensys required by this 
        Section 7.2 (as adjusted pursuant to this Section 7.2 (d)) until 
        the parties are able to mutually agree upon revised dollar 
        thresholds.

    7.3  ADJUSTMENTS IN THE EVENT OF CHANGES IN GOVERNMENT MANDATED DISCOUNTS 
AND REBATES.  Somerset represents that Total Government Discounts and Rebates 
during 1996 total approximately [          *          ].  In the event that 
governmental actions result in a mandated increase in Total Government 
Discounts and Rebates so that the Total Government Discounts and Rebates are 
higher than [         *          ] and Somerset makes a good faith 
determination 


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that such increased [     *     ] is a material increase, Somerset may call 
an emergency meeting of the Managing Committee, upon five (5) days written 
notice, and the Managing Committee will meet to discuss the circumstances 
surrounding such government mandated increase and recommend to the parties 
amendments to this Agreement so that the parties will share the risks 
associated with such government mandated increase.  The parties will then 
meet to consider the recommendations put forth by the Managing Committee and 
to negotiate in good faith an amendment to this Agreement so that the parties 
will share the risks associated with such government mandated increase.  Such 
amendment may include amendments to the [     *     ].

    7.4  AUDIT RIGHTS.  In accordance with its standard accounting practices, 
Somerset shall keep full and accurate books, records and invoices with 
respect to Actual Gross Sales, and the amounts payable hereunder, for no less 
than three (3) years after the end of the Term.  Somerset shall permit 
CoCensys to have such books and records examined by independent certified 
public accountants retained by CoCensys and acceptable to Somerset, during 
regular business hours and upon reasonable advance notice, but not later than 
three (3) years following the rendering of any such reports, accounting and 
payments and no more often than one (1) time per year.  Such independent 
accountants shall, pursuant to separate written contract, keep confidential 
any information obtained during such examination and shall report to CoCensys 
only Actual Gross Sales and the amounts which the independent accountant 
believes to be due and payable hereunder.  Any such information so reviewed 
and any such information reported shall be considered the Proprietary 
Information of Somerset.  In the absence of material discrepancies (in excess 
of [     *     ] of the total amount due to CoCensys in respect of the 
audited period) 


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in any request for payment resulting from such audit, the accounting expense 
shall be paid by CoCensys.  If material discrepancies do result, Somerset 
shall bear the accounting expense.



                                     ARTICLE 8.

                                  TERM; TERMINATION


    8.1  RENEWAL TERMS.  On or before November 1, 1997, the parties shall 
meet to discuss whether the term of this Agreement shall be renewed following 
the Term  hereof.

    8.2  TERMINATION RIGHTS.  Either party may terminate this Agreement for 
any reason, upon ninety (90) days advance written notice, subject to Sections 
8.3 and 8.4.

    8.3  TERMINATION UPON CESSATION OF SALE OF ELDEPRYL BRAND.  This 
Agreement may be terminated at any time without advance notice by either 
party, if, pursuant to Section 6.5 hereof, ELDEPRYL Brand is withdrawn from 
the market in the Territory.

    8.4  TERMINATION FOR BREACH.  Either party may terminate this Agreement 
for material breach or failure to perform any material duties or obligations 
under this Agreement by the other party, where such breach shall remain 
uncured, or such failure to perform shall continue, for at least thirty (30) 
days after the aggrieved party shall have given written notice of the breach 
or failure to perform to the other party.  If after the thirty (30) day 
period for cure and/or performance such breach remains uncured or such 
failure to perform continues, then the aggrieved party may, in accordance 
with Section 14.1, provide written notice to the other party 


                                       37.

<PAGE>

of termination of this Agreement ("Notice of Termination").  Such termination 
shall be effective fifteen (15) days from receipt of said Notice of 
Termination.

    8.5  EFFECT OF TERMINATION.  In the event this Agreement is terminated 
early, Gross Sales Based Compensation shall be calculated in the manner 
provided in Section 7.2(b) and Detail-Based Compensation shall be calculated 
in the manner provided in Section 7.1.  In the event that the effective date 
of termination occurs prior to June 30, 1997, [          *          ] payment 
due for the first six months of the Term, based on the portion of the first 
six months of 1997 during which the Agreement was in effect.  In the event 
that the effective date of termination occurs during the second six months of 
the Term, [         *          ].  Any sums which may be due to either party 
by reason of its performance through the effective date of termination will 
be paid by the other party within thirty (30) days of such termination.  
Neither party shall have any further rights to compensation from the other 
party in connection with ELDEPRYL Brand after the effective date of 
termination.

    8.6  TERMINATION OF THE 1996 AGREEMENT.  As of the Effective Date, the 
Promotion Agreement between Somerset and CoCensys effective January 4, 1996 
is terminated.


                                       38.

* Confidential treatment requested
<PAGE>

                                     ARTICLE 9.

                      WARRANTIES, REPRESENTATIONS AND COVENANTS


    9.1  WARRANTIES AND REPRESENTATIONS OF EACH PARTY.  Each party warrants 
and represents that (i) such party possesses all right, title, interest and 
authority necessary to enter into this Agreement, perform its obligations 
hereunder and to make the appointments set forth herein, (ii) all necessary 
corporate action has been taken to enable such party to execute and deliver 
this Agreement and perform its obligations hereunder, (iii) no governmental 
or third party consent is required in connection with such party's execution, 
delivery or performance of this Agreement, except such regulatory approvals 
as may be required to manufacture, sell and distribute ELDEPRYL Brand, (iv) 
this Agreement is such party's valid and binding obligation, enforceable in 
accordance with its terms, (v) such party is not and will not become party to 
any agreement in conflict herewith and (vi) such party will comply with all 
applicable local, state and federal laws and regulations, including, but not 
limited to, the Federal Food, Drug and Cosmetic Act, the Prescription Drug 
Marketing Act and the Federal Anti-Kickback Statute in carrying out its 
obligations pursuant to this Agreement.

    9.2  WARRANTIES AND REPRESENTATIONS OF SOMERSET.  Somerset warrants and 
represents that it is a corporation duly organized and validly existing under 
the laws of Delaware, with full power to conduct its affairs as contemplated 
herein.


                                       39.

<PAGE>

    9.3  WARRANTIES AND REPRESENTATIONS OF COCENSYS.  CoCensys warrants and 
represents that it is a corporation duly organized and validly existing under 
the laws of Delaware, with full power to conduct its affairs as contemplated 
herein.



                                     ARTICLE 10.

                     INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS


    10.1  NOTICE.  If either party shall learn of a claim or assertion that 
the manufacture, use or sale of ELDEPRYL Brand infringes or otherwise 
violates the intellectual property rights of any third party in the 
Territory, or that any third party violates the intellectual property rights 
of Somerset in ELDEPRYL Brand in the Territory, then the party becoming so 
informed shall promptly, but in all events within ten (10) business days 
thereof, notify the other party to this Agreement of the claim or assertion.

    10.2  CONDUCT OF INFRINGEMENT ACTIONS.  At its sole discretion, subject 
to this Article 10, Somerset shall conduct all infringement actions relating 
to ELDEPRYL Brand at its own expense.  Should any third party violation of 
the intellectual property rights of ELDEPRYL Brand have a material effect on  
Actual Gross Sales, the Managing Committee may address such material effect, 
as provided for in Section 3.1(b)(iii).


                                       40.

<PAGE>

                                     ARTICLE 11.

                                   INDEMNIFICATION


    11.1  INDEMNIFICATION BY SOMERSET.  Somerset shall defend, indemnify and 
hold harmless CoCensys from all liability, loss, costs, judgments, amounts 
paid in settlement, fines or penalties, including, but not limited to, 
reasonable attorneys' fees incurred by CoCensys which (i) relate to the 
manufacture, promotion, use or sale of ELDEPRYL Brand and (ii) CoCensys may 
suffer or sustain as a direct result of any third party claim, charge, suit 
or other action (a "Claim"), including, but not limited to Claims related to 
product liability, intellectual property infringement and advertising and 
promotion of ELDEPRYL Brand, except to the extent CoCensys's negligence or 
intentional malfeasance in connection with its promotion, use or sale of 
ELDEPRYL Brand shall have given rise to such Claim.

    11.2  INDEMNIFICATION BY COCENSYS.  CoCensys shall defend, indemnify and 
hold Somerset harmless from all liability, loss, costs, judgments, amounts 
paid in settlement, fines or penalties, including, but not limited to, 
reasonable attorneys' fees incurred by Somerset which Somerset may suffer or 
sustain as a direct result of any third party claim, charge, suit or other 
action as a direct result of any CoCensys negligence or intentional 
malfeasance in connection with its promotion, use or sale of ELDEPRYL Brand.


                                       41.

<PAGE>

    11.3  INDEMNIFICATION PROCEDURE.  The obligations of Somerset and CoCensys 
under this Article 11 shall be subject to the following terms and conditions:

            (i)    The party claiming a right to indemnification shall, within
                   ten (10) business days after receipt of any claim, charge,
                   suit or other action (or within ten (10) business days after
                   learning of a situation that is reasonably likely to lead to
                   a claim, charge, suit or other action), give, in accordance
                   with Section 14.1, written notice to the indemnifying party,
                   of any such claim, charge, suit or other action received
                   from a third party (or a description of the situation that
                   is reasonably likely to lead to the same) which is governed
                   by the indemnity obligations of this agreement;

           (ii)    The indemnifying party shall conduct, at its own expense,
                   the defense of any and all such claims, charges, suits or
                   other actions by a third party;

          (iii)    Neither party shall settle or admit liability with respect
                   to any such claims, charges, suits or other actions which
                   could result in liability to the other party without the
                   prior written consent of the other party, which consent
                   shall not be unreasonably withheld or delayed;

           (iv)    If the indemnifying party does not promptly take the steps
                   necessary against any such claims, charges, suits or other
                   actions by a third party, the party claiming indemnification
                   may defend against or settle such claims, charges, suits or
                   other actions 


                                       42.

<PAGE>

                   provided that party may not settle such claims, charges,
                   suits or other actions without prior written consent of
                   the indemnifying party which consent shall not be
                   unreasonably withheld or delayed; however, the defense
                   and/or settlement under this Article 11 shall not act as a
                   waiver of rights to indemnification under this Agreement,
                   or any other rights or remedies of a party claiming
                   indemnification and shall not excuse the indemnifying party
                   from its obligations hereunder and all reasonable costs and
                   expenses incurred by the party claiming indemnification
                   shall be subject to indemnity by the indemnifying party;
                   and,

            (v)    Each party will offer reasonable assistance to the other
                   party in defending or settling the claim, charge, suit or
                   other action.



                                     ARTICLE 12.

                                   CONFIDENTIALITY


    12.1  NONDISCLOSURE AND NONUSE OBLIGATIONS.  During the Term, and for a 
period of [     *     ] after expiration or termination hereof, each party 
will maintain all Proprietary Information in trust and confidence and will 
not disclose any Proprietary Information to any third party or use any 
Proprietary Information for any unauthorized purpose.  Each party may use 
such Proprietary Information only to the extent required to accomplish the 
purposes of this Agreement.  No Proprietary Information shall be disclosed to 
any employee, agent, Affiliate or 


                                       43.

* Confidential treatment requested
<PAGE>

consultant who does not have a need for such information. To the extent that 
disclosure to any third party is authorized by this Agreement, such third 
party shall be bound by written obligations to hold in confidence and not 
make use of such Proprietary Information for any purpose other than those 
permitted by this Agreement.  Each party will promptly notify the other upon 
discovery of any unauthorized use or disclosure of the Proprietary 
Information.

    12.2  EXCEPTIONS.  Proprietary Information shall not include any 
information which:

            (i)  is now, or hereafter becomes, through no act or failure to act
                 on the part of the receiving party, generally known or
                 available to the public;

           (ii)  is known by the receiving party at the time of receiving such
                 information, as evidenced by its written records;

          (iii)  is hereafter furnished to the receiving party by a third party,
                 as a matter of right and without restriction on disclosure;

           (iv)  is independently developed by the receiving party without any
                 breach of this Article 12; or

            (v)  is the subject of a written permission to disclose provided by
                 the disclosing party.

    12.3  AUTHORIZED DISCLOSURE.  Notwithstanding any other provision of this 
Agreement, each party may disclose Proprietary Information if such disclosure 
is required (i) by an order of a court or other governmental body of the 
United States or any political subdivision thereof; (ii) by law or 
regulation; or (iii) to prosecute or defend litigation or otherwise establish 
rights or enforce obligations under this Agreement, but only to the extent 
that any such disclosure is 


                                       44.

<PAGE>

necessary; provided that the disclosing party shall first have given notice to
the other party hereto, so that the other party may raise any objections to such
disclosure, shall cooperate with the other party to minimize the scope and
content of such disclosure, and, with respect to clauses (i) and (iii) of this
sentence, shall have made a reasonable effort to obtain a protective order
requiring that the Proprietary Information so disclosed be used only for the
purposes set forth in clause (i) or (iii) and, with respect to clause (ii) of
this sentence, shall have made a reasonable effort to obtain confidential
treatment for such Proprietary Information.  Notwithstanding any other provision
of this Agreement, each party may disclose the terms of this Agreement, on a
confidential basis, to lenders, investment bankers and other financial
institutions of its choice solely for due diligence purposes relating to
financing the business operations of such party.

    12.4   OBLIGATIONS AT END OF TERM.  Each party agrees, at the request of
the other party, at the end of the Term to either (i) return to the other party
all originals and copies of the other party's Proprietary Information; or, (ii)
at the other party's option, destroy all originals and copies of the other
party's Proprietary Information and to certify in writing such destruction to
the other party.

    12.5   RETENTION OF PROPRIETARY INFORMATION.  Each party may maintain 1
copy of any document containing Proprietary Information in its legal department,
or with its counsel, solely for archival purposes.


                                         45.
<PAGE>

                                     ARTICLE 13.

                                      PUBLICITY

    13.1   Subject to Section 13.2, all publicity, press releases and other
announcements relating to this Agreement or the transaction contemplated hereby
shall be reviewed in advance by, and be subject to the approval of, both
parties; PROVIDED, HOWEVER, that either party may, without the consent of the
other, (i) disclose the existence and general subject matter of this Agreement
without the other party's approval and (ii) subject to Section 12.3, disclose
the terms of this Agreement as required to comply with applicable securities
laws.  Any party that determines applicable securities laws require it to file
this Agreement shall first provide the other party a copy of the redacted
version it intends to file and shall provide the other party the opportunity to
comment thereon.  Notwithstanding the foregoing, the filing party will make the
final decisions regarding the version hereof to file.

    13.2   Subject to Section 12.3, any party that determines applicable
securities laws require it to disclose publicly (i) non-financial information
with respect to its relationship to the other party or (ii) any aspect of the
other party's business, shall first provide the other party a copy of the
disclosure it intends to disclose and shall provide the other party the
opportunity to comment thereon.  Notwithstanding the foregoing, the disclosing
party will have final decision-making authority with respect to its disclosures.


                                         46.
<PAGE>

                                     ARTICLE 14.

                                    MISCELLANEOUS

    14.1   NOTICES.  All notices required or permitted hereunder shall be given
in writing and sent by facsimile transmission, or mailed postage prepaid,
certified or registered mail, return receipt requested, or sent by a nationally
recognized express courier service, or hand-delivered at the following address:

           Somerset Pharmaceuticals, Inc.
           5215 West Laurel Street
           Tampa, Florida 33607
           Attn: Dr. Melvin Sharoky, President
           Fax: (813) 282-3804



           CoCensys, Inc.
           213 Technology Drive
           Irvine, California 92718
           Attn:  Office of the President
           Fax:  (714) 753-6161


All notices shall be deemed made upon receipt by the addressee as evidenced by
the applicable written receipt or, in the case of a facsimile, as evidenced by
the confirmation of transmission.

    14.2   CAPTIONS AND SECTION REFERENCES.  The titles, headings or captions
in this Agreement do not define, limit, extend, explain or describe the scope or
extent of this Agreement or any of its terms or conditions and therefore shall
not be considered in the interpretations, construction or application of this
Agreement.


                                         47.
<PAGE>

    14.3   SEVERABILITY.  Whenever possible, each clause, subclause, provision
or condition of this Agreement shall be interpreted in such manner as to be
effective and valid under applicable law, but if any clause, subclause,
provision or condition of this Agreement should be prohibited or invalid under
applicable law, such clause, subclause, provision or condition shall be
considered separate and severable from this Agreement to the extent of such
prohibition or invalidity without invalidating the remaining clauses,
subclauses, provisions and conditions of this Agreement, so long as the
remaining Agreement reflects the economic intentions of the parties as evidenced
by this Agreement as a whole.

    14.4   ENTIRE AGREEMENT.  This Agreement sets forth the entire agreement
between the parties hereto pertaining to the subject matter hereof and
supersedes all negotiations, preliminary agreements, memoranda or letters of
proposal or intent, discussions and understandings of the parties hereto in
connection with the subject matter hereof.  All discussions between the parties
have been merged into this Agreement and neither party shall be bound by any
definition, condition, understanding, representation, warranty, covenant or
provision other than as expressly stated in or contemplated by this Agreement or
as subsequently shall be set forth in writing and executed by a duly authorized
representative of the party to be bound thereby.

    14.5   AMENDMENT.  No amendment, change or modification of any of the
terms, provisions or conditions of this Agreement shall be effective unless made
in writing and signed on behalf of the parties hereto by their duly authorized
representatives.


                                         48.
<PAGE>

    14.6   COUNTERPARTS.  This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original document, but all
such separate counterparts shall constitute only one and the same Agreement.

    14.7   WAIVER.  No waiver of any term, provision or condition of this
Agreement, whether by conduct or otherwise, in any one or more instances, shall
be deemed to be or construed as a further or continuing waiver of any such or
other term, provision or condition of this Agreement.

    14.8   FORCE MAJEURE.  Neither party shall be liable hereunder to the other
party nor shall be in breach for failure to perform its obligations caused by
circumstances beyond the control of either party, including, but not limited to,
acts of God; fires; earthquakes; floods; riots; wars; civil disturbances;
sabotage; accidents; labor disputes; shortages or government actions.  In the
case of any such event, the affected party shall promptly notify the other
party, and shall keep the other party informed of the efforts to resume
performance.  After thirty (30) days of such inability to perform, the parties
agree to meet and in good faith discuss to proceed.  In the event that the
affected party is prevented from performing its obligations pursuant to this
Section 14.8 for a period of thirty (30) additional days, the other party shall
have the right to terminate this Agreement on thirty (30) days prior written
notice, i.e. ninety (90) days from the date of such force majeure event, subject
to the provisions of Section 8.5.

    14.9   ASSIGNMENT; BENEFITS AND BINDING NATURE OF AGREEMENT.  This
Agreement may not be assigned by either party without the consent of the other
party, which consent shall not


                                         49.
<PAGE>

be unreasonably withheld, except to any Affiliate or successor by merger or sale
of substantially all of its business units to which this Agreement relates. 
Upon a permitted assignment, the assigning party shall promptly notify the other
party of such assignment.  If CoCensys assigns this Agreement, either party may,
within thirty (30) days of the date on which notice is given pursuant to the
preceding sentence, terminate this Agreement upon ninety (90) days written
notice.  This Agreement shall be binding upon and shall inure to the benefit of
the parties hereto and their respective successors and assigns permitted under
this Agreement.

    14.10  SURVIVAL.  The provisions of Sections 4.9, 6.2(c), 7.4  and 8.5 and
Articles 11, 12, and 13 shall survive, and remain in effect, after termination
or expiration of this Agreement.

    14.11  NOT STRICTLY CONSTRUED AGAINST EITHER PARTY.  This Agreement has
been prepared jointly and shall not be strictly construed against either party.

    14.12  GOVERNING LAW.  This Agreement shall be construed and interpreted in
accordance with the laws of the State of Delaware other than those provisions
governing conflicts of law.  In the event the parties are unable to resolve
disputes which go beyond the scope of the responsibilities of the Managing
Committee, or any disputes arising from matters set forth in Sections
3.1(b)(iii) and 3.1(b)(iv), each party shall be free to pursue any action at law
or equity.


                                         50.
<PAGE>

    IN WITNESS WHEREOF, the parties have caused this Agreement to be executed
on the day and year first above written.


SOMERSET PHARMACEUTICALS, INC.              COCENSYS, INC.


By: /s/                                         By: /s/ Richard A. Henson
    -------------------------------                 ----------------------------

Title: President                                    Title: President
       Somerset Pharmaceuticals                            CoCensys Pharma 
                                                           Sales & Marketing
       ----------------------------                        ---------------------


                                         51.
<PAGE>

                                     EXHIBIT 5.7
                        SOMERSET STANDARD SALES REPORT FORMAT

[SOMERSET LETTERHEAD]









                                  ELDEPRYL SHIPMENTS

                                                 DATE OF SHIPMENTS
                                                                    ------------


                                     BOTTLES             DOLLARS
                                     -------             -------

TODAYS SHIPMENT
                               -------------      --------------
MONTH-TO-MONTH
                               -------------      --------------
QUARTER-TO-DATE
                               -------------      --------------
YEAR-TO-DATE
                               -------------      --------------



<PAGE>

                                    EXHIBIT 7.1(d)
                              EXAMPLES OF CALCULATION OF
                           DETAIL-BASED COMPENSATION UNDER 
                           DIFFERENT HYPOTHETICAL SCENARIOS

(1) HYPOTHETICAL #1:  QUARTERLY DETAIL PAYMENT REDUCTION


                                  [       *       ]


                                         53.

* Confidential treatment requested
<PAGE>

HYPOTHETICAL #2:   MONTHLY DETAIL PAYMENT REDUCTION (E.G., AGREEMENT TERMINATES
                   ON 9/1/97)


                                  [       *       ]



                                         54.

* Confidential treatment requested
<PAGE>

                                     EXHIBIT 7.2

                                  [       *       ]



                                         55.

* Confidential treatment requested

<PAGE>


                 DEVELOPMENT AND COMMERCIALIZATION AGREEMENT (NO. 1)



                                       BETWEEN



                                   COCENSYS, INC.,


                                         AND


                              WYETH-AYERST LABORATORIES

<PAGE>

                                  TABLE OF CONTENTS

                                                                          PAGE

1.  DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   1
    1.1   "Affiliate(s)" . . . . . . . . . . . . . . . . . . . . . . . . .   1
    1.2   "Agreement (No. 2)"  . . . . . . . . . . . . . . . . . . . . . .   1
    1.3   "All Other Markets". . . . . . . . . . . . . . . . . . . . . . .   2
    1.4   "Back-Up Compound Candidate" . . . . . . . . . . . . . . . . . .   2
    1.5   "Back-Up Program". . . . . . . . . . . . . . . . . . . . . . . .   2
    1.6   "Back-Up Program Term" . . . . . . . . . . . . . . . . . . . . .   2
    1.7   "Beginning of [     *     ]. . . . . . . . . . . . . . . . . . .   2
    1.8   "Beginning of [     *     ]. . . . . . . . . . . . . . . . . . .   2
    1.9   "CO 2-6749". . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.10  "CoCensys Patent Rights" . . . . . . . . . . . . . . . . . . . .   2
    1.11  "Commercially Reasonable Efforts". . . . . . . . . . . . . . . .   2
    1.12  "Control". . . . . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.13  "Co-Promotion" . . . . . . . . . . . . . . . . . . . . . . . . .   2
    1.14  "Development". . . . . . . . . . . . . . . . . . . . . . . . . .   3
    1.15  "Epalon" . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    1.16  "FDA". . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    1.17  "Field". . . . . . . . . . . . . . . . . . . . . . . . . . . . .   3
    1.18  "First Commercial Sale". . . . . . . . . . . . . . . . . . . . .   3
    1.19  "Fully Burdened Cost". . . . . . . . . . . . . . . . . . . . . .   3
    1.20  "Good Clinical Practice" . . . . . . . . . . . . . . . . . . . .   3
    1.21  "Good Laboratory Practice" . . . . . . . . . . . . . . . . . . .   3
    1.22  "Good Manufacturing Practice". . . . . . . . . . . . . . . . . .   4
    1.23  "Gross Margin" . . . . . . . . . . . . . . . . . . . . . . . . .   4
    1.24  [     *     ]. . . . . . . . . . . . . . . . . . . . . . . . . .   4
    1.25  "IND". . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
    1.26  "Intellectual Property Rights" . . . . . . . . . . . . . . . . .   4
    1.27  "Invention". . . . . . . . . . . . . . . . . . . . . . . . . . .   4
    1.28  "Joint Marketing Committee" or "JMC" . . . . . . . . . . . . . .   4
    1.29  "Know-How" . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
    1.30  "Licensed Compound". . . . . . . . . . . . . . . . . . . . . . .   5
    1.31  "Marketing Plan" . . . . . . . . . . . . . . . . . . . . . . . .   5
    1.32  "NDA". . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
    1.33  "Net Sales". . . . . . . . . . . . . . . . . . . . . . . . . . .   5
    1.34  "Neurologist Market" . . . . . . . . . . . . . . . . . . . . . .   6
    1.35  [     *     ]. . . . . . . . . . . . . . . . . . . . . . . . . .   6
    1.36  "Non-Scheduled Product". . . . . . . . . . . . . . . . . . . . .   6
    1.37  "Patent Rights". . . . . . . . . . . . . . . . . . . . . . . . .   6
    1.38  "Phase I," . . . . . . . . . . . . . . . . . . . . . . . . . . .   6


                                          i.
* Confidential treatment requested

<PAGE>

                                  TABLE OF CONTENTS
                                     (CONTINUED)

                                                                          PAGE

    1.39  "Prescription Audit" . . . . . . . . . . . . . . . . . . . . . .   6
    1.40  "Product". . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
    1.41  "Promotion". . . . . . . . . . . . . . . . . . . . . . . . . . .   6
    1.42  "Psychiatrist Market". . . . . . . . . . . . . . . . . . . . . .   7
    1.43  "Regulatory Approval". . . . . . . . . . . . . . . . . . . . . .   7
    1.44  "Scheduled Product". . . . . . . . . . . . . . . . . . . . . . .   7
    1.45  "Term of Co-Promotion" . . . . . . . . . . . . . . . . . . . . .   7
    1.46  "Third Party(ies)" . . . . . . . . . . . . . . . . . . . . . . .   7
    1.47  "Trademark". . . . . . . . . . . . . . . . . . . . . . . . . . .   7
    1.48  "USA". . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   7
    1.49  "Wyeth-Ayerst Patent Rights" . . . . . . . . . . . . . . . . . .   7

2.  DEVELOPMENT OF LICENSED COMPOUND . . . . . . . . . . . . . . . . . . .   7
    2.1   General Obligations. . . . . . . . . . . . . . . . . . . . . . .   7
    2.2   Records, Reports and Information Exchange. . . . . . . . . . . .   8
    2.3   Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . .   8
    2.4   Funding of the Development . . . . . . . . . . . . . . . . . . .   8
    2.5   Regulatory Approvals . . . . . . . . . . . . . . . . . . . . . .   8

3.  BACK-UP PROGRAM. . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
    3.1   Purpose. . . . . . . . . . . . . . . . . . . . . . . . . . . . .   9
    3.2   Back-Up Program Term . . . . . . . . . . . . . . . . . . . . . .   9
    3.3   Reporting and Submission of Back-Up Compound Candidates. . . . .   9
    3.4   Back-Up Compound Development.. . . . . . . . . . . . . . . . . .   9
    3.5   Back-Up Program Funding. . . . . . . . . . . . . . . . . . . . .   9
    3.6   Partial Reimbursement of Back-Up Program Fees. . . . . . . . . .   9
    3.7   Applicability of this Agreement. . . . . . . . . . . . . . . . .  10

4.  INDICATIONS; EXCLUSIVITY . . . . . . . . . . . . . . . . . . . . . . .  10
    4.1   Indications. . . . . . . . . . . . . . . . . . . . . . . . . . .  10
    4.2   No [     *     ] by CoCensys [     *     ] . . . . . . . . . . .  11
    4.3   No [     *     ] . . . . . . . . . . . . . . . . . . . . . . . .  11

5.  LICENSE GRANTS . . . . . . . . . . . . . . . . . . . . . . . . . . . .  11
    5.1   Licenses to Wyeth-Ayerst . . . . . . . . . . . . . . . . . . . .  11
    5.2   Licenses to CoCensys . . . . . . . . . . . . . . . . . . . . . .  11
    5.3   Licenses upon Expiration . . . . . . . . . . . . . . . . . . . .  12


                                         ii.

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                                  TABLE OF CONTENTS
                                     (CONTINUED)

                                                                          PAGE

6.  CONSIDERATION TO COCENSYS. . . . . . . . . . . . . . . . . . . . . . .  12
    6.1   Upfront Fee. . . . . . . . . . . . . . . . . . . . . . . . . . .  12
    6.2   Equity Investment. . . . . . . . . . . . . . . . . . . . . . . .  12
    6.3   Payments . . . . . . . . . . . . . . . . . . . . . . . . . . . .  12
    6.4   Method of Payment of Payments. . . . . . . . . . . . . . . . . .  13
    6.5   Payments for Back-Up Compound Candidates . . . . . . . . . . . .  13
    6.6   Royalties and Profit Sharing . . . . . . . . . . . . . . . . . .  13

7.  CO-PROMOTION OF THE PRODUCT IN THE USA . . . . . . . . . . . . . . . .  13
    7.1   Promotion and Co-Promotion Rights. . . . . . . . . . . . . . . .  13
    7.2   Joint Marketing Committee. . . . . . . . . . . . . . . . . . . .  16
    7.3   Marketing Plan . . . . . . . . . . . . . . . . . . . . . . . . .  18
    7.4   Sales Force Expenses . . . . . . . . . . . . . . . . . . . . . .  18
    7.5   Determination and Allocation of Gross Margin and Royalties . . .  18
    7.6   Adjustment to Royalties. . . . . . . . . . . . . . . . . . . . .  19
    7.7   Prescription Audit.. . . . . . . . . . . . . . . . . . . . . . .  20
    7.8   Payment and Reporting. . . . . . . . . . . . . . . . . . . . . .  20
    7.9   Promotional and Advertising Materials. . . . . . . . . . . . . .  21
    7.10  Pricing. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  21
    7.11  No Delegation. . . . . . . . . . . . . . . . . . . . . . . . . .  21
    7.12  Returns. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  21
    7.13  Orders . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  21
    7.14  Samples. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  22
    7.15  Completion of Sales. . . . . . . . . . . . . . . . . . . . . . .  22
    7.16  Training . . . . . . . . . . . . . . . . . . . . . . . . . . . .  22
    7.17  Exchange of Marketing Information. . . . . . . . . . . . . . . .  22

8.  ACCOUNTS AND RECORDS . . . . . . . . . . . . . . . . . . . . . . . . .  22
    8.1   Records. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  22
    8.2   Audits.. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  22
    8.3   Sales by Sublicensees. . . . . . . . . . . . . . . . . . . . . .  23
    8.4   Withholding. . . . . . . . . . . . . . . . . . . . . . . . . . .  23

9.  TRADEMARKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  23

10. MANUFACTURING AND DISTRIBUTION . . . . . . . . . . . . . . . . . . . .  23
    10.1  Primary Manufacture. . . . . . . . . . . . . . . . . . . . . . .  23
    10.2  Second Source. . . . . . . . . . . . . . . . . . . . . . . . . .  23
    10.3  Exchange of Information. . . . . . . . . . . . . . . . . . . . .  24


                                         iii.

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                                  TABLE OF CONTENTS
                                     (CONTINUED)

                                                                          PAGE

    10.4  Compliance . . . . . . . . . . . . . . . . . . . . . . . . . . .  24

11. PROSECUTION, MAINTENANCE AND INFRINGEMENT OF INTELLECTUAL PROPERTY
    RIGHTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  24
    11.1  Patentable Inventions. . . . . . . . . . . . . . . . . . . . . .  24
    11.2  Prosecution and Maintenance of Patent Rights . . . . . . . . . .  25
    11.3  Patent Extensions. . . . . . . . . . . . . . . . . . . . . . . .  25
    11.4  Cooperation. . . . . . . . . . . . . . . . . . . . . . . . . . .  25
    11.5  Infringement of Intellectual Property Rights . . . . . . . . . .  25
    11.6  Infringement of Third Party Patent Rights. . . . . . . . . . . .  27

12. FORCE MAJEURE. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  28

13. TERM AND TERMINATION . . . . . . . . . . . . . . . . . . . . . . . . .  28
    13.1  General Conditions of Expiration and Termination . . . . . . . .  28
    13.2  Term . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  28
    13.3  Termination for Breach . . . . . . . . . . . . . . . . . . . . .  29
    13.4  Breach by CoCensys . . . . . . . . . . . . . . . . . . . . . . .  29
    13.5  No Limit on Remedies . . . . . . . . . . . . . . . . . . . . . .  29
    13.6  Unilateral Termination by Wyeth-Ayerst . . . . . . . . . . . . .  29
    13.7  Determination of Co-Promotion Rights upon Change in Control. . .  30

14. ASSIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  30
    14.1  Assignment to Affiliates . . . . . . . . . . . . . . . . . . . .  30
    14.2  Other Permitted Assignment . . . . . . . . . . . . . . . . . . .  30
    14.3  Binding Nature of Assignment . . . . . . . . . . . . . . . . . .  31

15. INDEMNIFICATION. . . . . . . . . . . . . . . . . . . . . . . . . . . .  31
    15.1  Cross Indemnification. . . . . . . . . . . . . . . . . . . . . .  31
    15.2  Insurance. . . . . . . . . . . . . . . . . . . . . . . . . . . .  31

16. WARRANTIES AND REPRESENTATIONS . . . . . . . . . . . . . . . . . . . .  32
    16.1  General. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  32
    16.2  USC/Rockefeller License. . . . . . . . . . . . . . . . . . . . .  32

17. CONFIDENTIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . .  32
    17.1  Information. . . . . . . . . . . . . . . . . . . . . . . . . . .  32
    17.2  Exceptions.. . . . . . . . . . . . . . . . . . . . . . . . . . .  32
    17.3  Permitted Disclosures. . . . . . . . . . . . . . . . . . . . . .  33


                                         iv.
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                                  TABLE OF CONTENTS
                                     (CONTINUED)

                                                                          PAGE

    17.4  Disclosure of Agreement. . . . . . . . . . . . . . . . . . . . .  33
    17.5  Publicity. . . . . . . . . . . . . . . . . . . . . . . . . . . .  33
    17.6  Publication. . . . . . . . . . . . . . . . . . . . . . . . . . .  34

18. MISCELLANEOUS. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  34
    18.1  No Waiver of Contractual Rights. . . . . . . . . . . . . . . . .  34
    18.2  Execution and Amendments . . . . . . . . . . . . . . . . . . . .  34
    18.3  Severability . . . . . . . . . . . . . . . . . . . . . . . . . .  34
    18.4  Relationship between the Parties . . . . . . . . . . . . . . . .  34
    18.5  Correspondence and Notices . . . . . . . . . . . . . . . . . . .  35
    18.6  Choice of Law. . . . . . . . . . . . . . . . . . . . . . . . . .  35
    18.7  Counterparts . . . . . . . . . . . . . . . . . . . . . . . . . .  36


                                          v.
<PAGE>

                 DEVELOPMENT AND COMMERCIALIZATION AGREEMENT (NO. 1)


     THIS DEVELOPMENT AND COMMERCIALIZATION AGREEMENT (NO. 1) (the "Agreement")
is entered into as of the 12th day of May, 1997 (the "Effective Date"), by and
between COCENSYS, INC., a company incorporated under the laws of the State of
Delaware, with its principal place of business at 213 Technology Drive, Irvine,
California 92618, USA ("CoCensys"), and AMERICAN HOME PRODUCTS CORPORATION,
acting through its WYETH-AYERST LABORATORIES DIVISION, a company incorporated
under the laws of the State of Delaware, with its principal place of business at
555 Lancaster Avenue, St. Davids, Pennsylvania 19087, USA ("Wyeth-Ayerst"). 
Both CoCensys and Wyeth-Ayerst are referred to individually as a "Party" and
collectively as the "Parties."

     WHEREAS, CoCensys has discovered, has rights to and is developing that
certain compound CO 2-6749 (as defined in Article 1.9 below); and

     WHEREAS, Wyeth-Ayerst would like to obtain the United States rights to
develop and commercialize CO 2-6749 or a back-up compound therefor; and

     WHEREAS, CoCensys and Wyeth-Ayerst wish to co-promote CO 2-6749 or a
back-up compound in the United States;

     NOW, THEREFORE, in consideration of the foregoing premises and the mutual
premises, covenants and conditions contained in this Agreement, the Parties
agree as follows:

1.   DEFINITIONS.

     For the purposes of this Agreement, the terms hereunder shall have the
     meanings as defined below:

     1.1   "AFFILIATE(S)" shall mean, in the case of either CoCensys or
           Wyeth-Ayerst, any corporation, joint venture, or other business
           entity which directly or indirectly controls, is controlled by, or
           is under common control with that Party.  "Control," as used in this
           Article 1.1, shall mean having the power to direct, or cause the
           direction of, the management and policies of an entity, whether
           through ownership of voting securities, by contract or otherwise.

     1.2   "AGREEMENT (NO. 2)" shall mean that certain Development and
           Commercialization Agreement (No.2) between the Parties relating to
           development and commercialization of CO 2-6749 or a back-up compound
           therefore in all countries and territories in the world except the
           USA, entered into on even date with the Effective Date.


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     1.3   "ALL OTHER MARKETS" shall mean all physicians, other than
           neurologists and psychiatrists, prescribing pharmaceutical products
           in the USA during the Term of Co-Promotion, including without
           limitation, all general practitioners.
     
     1.4   "BACK-UP COMPOUND CANDIDATE" shall mean any Epalon meeting the
           criteria set forth in Exhibit A as determined by CoCensys and
           submitted by CoCensys to Wyeth-Ayerst as a potential substitute for
           CO 2-6749.  "Back-Up Compound Candidate" shall include any prodrugs,
           salt forms and other biologically active isomers or enantiomers of
           such CoCensys Epalon.

     1.5   "BACK-UP PROGRAM" shall mean the program for identification of
           Back-Up Compound Candidates as conducted by CoCensys pursuant to
           Article 3.

     1.6   "BACK-UP PROGRAM TERM" shall mean the period commencing on the
           Effective Date and terminating on the [     *     ] anniversary
           thereof, unless extended pursuant to Article 3.2.

     1.7   "BEGINNING OF [     *     ] shall mean the date upon which the
           [     *     ] for a Product.

     1.8   "BEGINNING OF [     *     ] shall mean the date upon which the
           [     *     ] for a Product.

     1.9   "CO 2-6749"  shall mean the Epalon [     *     ] and any prodrugs,
           including specifically CO 6-0549, salt forms and other biologically
           active isomers or enantiomers palon.  A diagram of the chemical
           structure of each of CO 2-6749 and CO 6-0549 is set forth on Exhibit
           B.

     1.10  "COCENSYS PATENT RIGHTS" shall mean all Patent Rights owned or
           Controlled by CoCensys.  A list of the CoCensys Patent Rights
           existing as of the Effective Date is set out in Exhibit C hereto.

     1.11  "COMMERCIALLY REASONABLE EFFORTS" shall mean efforts and resources
           normally used by a party for a compound owned by it or to which it
           has rights, which is of similar market potential at a similar stage
           in its product life, taking into account the competitiveness of the
           marketplace, the proprietary position of the compound, the
           regulatory structure involved, the profitability of the applicable
           products, and other relevant factors.

     1.12  "CONTROL" shall mean licensed with the right to grant sublicenses
           without violating the terms of any Third Party agreement.


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     1.13  "CO-PROMOTION" shall mean the promotion, marketing and selling of
           the Product, including, in particular, the detailing of the Product
           to physicians, jointly through the sales forces of CoCensys and
           Wyeth-Ayerst in the USA under the Trademark and Regulatory Approval
           held by Wyeth-Ayerst and Wyeth-Ayerst's distribution system.

     1.14  "DEVELOPMENT" shall mean the pre-clinical development of a Licensed
           Compound and clinical development for use in the Field of a Product
           through and including Regulatory Approval.

     1.15  "EPALON" shall mean the class of neuroactive steroid compounds that
           interact with GABA(A) receptor complexes.

     1.16  "FDA" shall mean the Food and Drug Administration of the USA.

     1.17  "FIELD" shall mean the treatment in humans of 
           [          *          ] in the Diagnostic and Statistical Manual of 
           Mental Disorders, Fourth Edition ("DSM-IV").  Also, specifically to 
           be included under [          *          ] defined by research 
           criteria in DSM-IV. It is understood by the Parties that the above-
           named disorders may d differently in future editions of the 
           Diagnostic and Statistical Manual of Mental Disorders, but that, 
           for purposes of this Agreement, the definition of Field shall 
           always be with reference to those diseases which fall within the 
           definition of the above-named disorders in the edition of DSM-IV 
           which is current as of the Effective Date.  Expressly excluded from 
           the Field are [          *          ].

     1.18  "FIRST COMMERCIAL SALE" shall mean the first sale of a Product in
           the USA after the Product has been granted Regulatory Approval by
           the competent authorities in the USA.

     1.19  "FULLY BURDENED COST" shall mean the sum of the costs set forth in
           Exhibit D, to the extent allocable to Product.

     1.20  "GOOD CLINICAL PRACTICE" or "GCP" shall mean the then current
           standards for clinical trials for pharmaceuticals, as set forth in
           the United States Federal Food, Drug and Cosmetics Act and
           applicable regulations promulgated thereunder, as amended from time
           to time.

     1.21  "GOOD LABORATORY PRACTICE" or "GLP" shall mean the then current
           standards for laboratory activities for pharmaceuticals, as set
           forth in the United States Federal Food, Drug and Cosmetics Act and
           applicable regulations promulgated thereunder, as amended from time
           to time.


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     1.22  "GOOD MANUFACTURING PRACTICE" or "GMP" shall mean the current
           standards for the manufacture of pharmaceuticals, as set forth in
           the United States Federal Food, Drug and Cosmetics Act and
           applicable regulations promulgated hereunder, as amended from time
           to time.

     1.23  "GROSS MARGIN" shall mean Net Sales in either the Neurologist
           Market, the Psychiatrist Market and/or All Other Markets, as the
           case may be, minus the Fully Burdened Cost for such Net Sales.

     1.24  [          *          ] shall mean the development milestone 
           [          *          ].

     1.25  "IND" shall mean an Investigational New Drug Application as defined
           in the United States Federal Food, Drug and Cosmetics Act and
           applicable regulations promulgated thereunder, as amended from time
           to time.

     1.26  "INTELLECTUAL PROPERTY RIGHTS" shall mean all Patent Rights,
           trademarks, copyrights, know-how and/or trade secrets which are
           owned or Controlled by one Party hereto (with the right to license)
           or jointly by the Parties, with regard to the development,
           manufacture, importing, use, marketing and/or sale of the Product.

     1.27  "INVENTION" shall mean an invention conceived in the course of the
           performance of and within the scope of this Agreement.

     1.28  "JOINT MARKETING COMMITTEE" or "JMC" shall mean the committee
           appointed by the Parties as set forth in Article 7.2.

     1.29  "KNOW-HOW" shall mean all know-how, processes, information and data
           including any copyright relating thereto owned or controlled by
           either Party (with the right to have or disclose) as of the
           Effective Date or acquired during the term of this Agreement
           relating to:

           (a) the Licensed Compound;

           (b) any Back-Up Compound;

           (c) any Product containing (a) or (b);

           (d) methods of making any of (a), (b) or (c);

           (e) any component of (c);

           (f) any intermediate in the making of any of (a), (b), (c), or
               (e);


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         (G)  any method of using any of (a), (b), (c), (e), or (f); and/or

         (H)  any use of (a), (b) or (c).

         The term "Know-How," however, shall not include any know-how,
         processes, information and data which is, as of the Effective Date or
         becomes later on, generally available to the public.

    1.30 "LICENSED COMPOUND" shall mean CO 2-6749 and any Back-Up Compound
         Candidate.  

    1.31 "MARKETING PLAN" shall have the meaning set forth in Article 7.3.

    1.32 "NDA" shall mean a New Drug Application, as defined in the United
         States Federal Food Drug and Cosmetic Act and applicable regulations
         promulgated thereunder as amended from time to time.

    1.33 "NET SALES" shall mean proceeds from sales of the Product by either
         Party, its Affiliates or sublicensees, as appropriate, to Third
         Parties, less the sum of (a) and (b) where (a) is a provision,
         determined under generally accepted accounting principles in the
         United States, for [          *          ] and (b) is [          *     
             ]

         Sales of Product by and between a Party and its Affiliates are not
         sales to Third Parties and shall be excluded from Net Sales
         calculations for all purposes.

    1.34 "NEUROLOGIST MARKET" shall mean all neurologists prescribing
         pharmaceutical products in the USA during the Term of Co-Promotion.

    1.35  [     *     ] shall have the meaning set forth in Article 4.1.

    1.36 "NON-SCHEDULED PRODUCT" shall mean a Product that has achieved
         Regulatory Approval in the USA as either a "Schedule V" designation,
         as defined in 21 CFR Part 1308, or no scheduling designation under 21
         CFR Part 1308.

    1.37 "PATENT RIGHTS" shall mean all patents or patent applications, in the
         USA, and all divisionals, continuations, continuations-in-part,
         reissues, extensions, supplementary protection certificates thereof,
         existing as of the Effective Date or filed or issuing during the term
         of this Agreement, at least one claim of which covers:

         (A)  the Licensed Compound;

         (B)  any Back-Up Compound;


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         (C)  any Product containing (a) or (b);

         (D)  methods of making any of (a), (b) or (c);

         (E)  any component of (c);

         (F)  any intermediate in the making of any of (a), (b), (c) or (e);

         (G)  any method of using any of (a), (b), (c), (e), or (f); and/or

         (H)  any use of (a), (b) or (c).

    1.38 "PHASE I," "PHASE II," AND "PHASE III" shall mean the phases of the
         clinical development of pharmaceuticals as defined in the United
         States Federal Food, Drug and Cosmetics Act and/or applicable
         regulations promulgated thereunder, as amended from time to time, or
         any comparable foreign regulations.

    1.39 "PRESCRIPTION AUDIT" shall mean an audit conducted pursuant to
         Article 7.7.

    1.40 "PRODUCT" shall mean any pharmaceutical product containing a Licensed
         Compound in any formulation or mode of administration. 

    1.41 "PROMOTION" shall mean, as applied to a Party, the promotion,
         marketing and selling of the Product, including in particular, the
         detailing of the Product to physicians, solely by that Party through
         its sales force in the USA under the Trademark and the Regulatory
         Approval held by Wyeth-Ayerst, and Wyeth-Ayerst's distribution system.

    1.42 "PSYCHIATRIST MARKET" shall mean all psychiatrists prescribing
         pharmaceutical products in the USA during the Term of Co-Promotion.

    1.43 "REGULATORY APPROVAL" shall mean all authorizations by the competent
         authorities which are required for the regular marketing, promotion,
         pricing and sale of the Product in a given country or regulatory
         jurisdiction.

    1.44 "SCHEDULED PRODUCT" shall mean a Product that has received Regulatory
         Approval in the USA as a Schedule I, II, III or IV product, as defined
         in 21 CFR Part 1308.

    1.45 "TERM OF CO-PROMOTION" shall mean the period extending from First
         Commercial Sale in the USA until the later of (i) expiration of the
         last to expire patent within the Patent Rights necessary to make, use,
         import, offer for sale or sell the Product in the USA, or (ii) fifteen
         (15) years from First Commercial Sale in the USA.


                                          6.
<PAGE>

    1.46 "THIRD PARTY(IES)" shall mean any person(s) or entity(ies) other than
         CoCensys, Wyeth-Ayerst or their Affiliates.

    1.47 "TRADEMARK" shall mean the trademark under which the Product shall be
         marketed as set out in Article 9.

    1.48 "USA" shall mean the United States of America, its territories and
         possessions and the Commonwealth of Puerto Rico.

    1.49 "WYETH-AYERST PATENT RIGHTS" shall mean all Patent Rights owned or
         Controlled by Wyeth-Ayerst.  A list of the Wyeth-Ayerst Patent Rights
         existing as of the Effective Date is set out in Exhibit E hereto. 

2.  DEVELOPMENT OF LICENSED COMPOUND.

    2.1  GENERAL OBLIGATIONS.  Wyeth-Ayerst shall be responsible for the
         design, implementation and funding of all Development.  Wyeth-Ayerst
         agrees to use Commercially Reasonable Efforts to conduct the
         Development with the intent of obtaining Regulatory Approval in the
         USA and bringing a Product in the Field to the market as soon as
         reasonably practicable. Wyeth-Ayerst shall ensure that the Development
         is carried out adhering to Wyeth-Ayerst's ethical and safety
         standards.  Wyeth-Ayerst shall have the right to subcontract with
         third parties any of its Development obligations hereunder, without
         the consent or approval of CoCensys.  In the event Wyeth-Ayerst
         intends to exercise its right to subcontract one or more of its
         Development obligations, it shall notify CoCensys of such intent and
         CoCensys shall have the right to submit one or more proposals to
         Wyeth-Ayerst to perform such one or more parts of such Development
         activities.  Wyeth-Ayerst shall consider all such proposals submitted
         by CoCensys on an equal basis with proposals submitted by Third Party
         subcontractors for the same Development tasks.

    2.2  RECORDS, REPORTS AND INFORMATION EXCHANGE.

         2.2.1   TECHNOLOGY AND INFORMATION TRANSFER.  CoCensys will provide to
                 Wyeth-Ayerst all Know-How as Wyeth-Ayerst deems necessary to
                 carry out the Development and [     *     ] of the Product and
                 to obtain Regulatory Approval.  All information transferred,
                 provided or exchanged under this Article 2.2.1 will be subject
                 to the confidentiality requirements set forth in Article 17.

         2.2.2   RECORD KEEPING.  Wyeth-Ayerst will maintain records in
                 sufficient detail and in good scientific manner appropriate
                 for Regulatory Approval and patent purposes.


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         2.2.3   COMMUNICATION REGARDING THE DEVELOPMENT PROGRESS.  A project
                 team shall be appointed by Wyeth-Ayerst and representatives
                 thereof shall meet with representatives of CoCensys on a
                 regular basis (but no less often than every six (6) months) to
                 keep CoCensys apprised of the Development progress and to
                 bring to its attention any problems or issues which may have
                 an impact on the timing of the Development (e.g., regulatory
                 submissions).

    2.3  COMPLIANCE.  Wyeth-Ayerst shall comply with all GLP, GCP and GMP in
         the conduct of the Development.

    2.4  FUNDING OF THE DEVELOPMENT.  Wyeth-Ayerst shall be responsible for one
         hundred percent (100%) of all costs, fees and expenses associated with
         the Development and the obtaining of all Regulatory Approvals.

    2.5  REGULATORY APPROVALS.  [     *     ] shall file all regulatory
         dossiers under its name.  [     *     ] shall own all Regulatory
         Approvals.  [     *     ] shall have the right of reference to the
         extent necessary to exercise its rights or to meet its obligations
         hereunder.  [     *     ] shall be responsible for all communications
         with regulatory agencies, subject to its obligation to keep the Joint
         Marketing Committee informed.


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3.  BACK-UP PROGRAM.

    3.1  PURPOSE.  During the Back-Up Program Term, CoCensys shall use
         Commercially Reasonable Efforts to conduct research, and identify,
         characterize and submit to Wyeth-Ayerst Back-Up Compound Candidates.

    3.2  BACK-UP PROGRAM TERM.  The term of the Back-Up Program shall commence
         on the Effective Date and terminate on the [     *     ] anniversary
         thereof.  Such term may be extended for [          *          ] upon
         120 days prior written notice to [     *     ].  Any Epalons in the
         process of being evaluated for meeting the criteria set forth in
         Exhibit A under the Back-Up Program as of the termination of the
         Back-Up Program shall be submitted to Wyeth-Ayerst promptly thereafter
         to the extent they meet the criteria set forth on Exhibit A.  At the
         end of the Back-Up Program Term, Wyeth-Ayerst shall have rights only
         to those Back-Up Compound Candidates [          *          ] or
         thereafter pursuant to the third sentence of this Article 3.2.

    3.3  REPORTING AND SUBMISSION OF BACK-UP COMPOUND CANDIDATES.  Within
         thirty (30) days of the Effective Date, and at least every six (6)
         months during the Back-Up Program Term, CoCensys shall provide
         Wyeth-Ayerst with a report on the status of the Back-Up Program and
         shall submit on an on-going basis all Back-Up Compound Candidates.

    3.4  BACK-UP COMPOUND DEVELOPMENT.  Wyeth-Ayerst may, at any time and upon
         written notice to CoCensys, (i) elect to [          *          ].

    3.5  BACK-UP PROGRAM FUNDING.  Wyeth-Ayerst shall fund the Back-Up Program
         at the level of Three Million Dollars ($3,000,000) annually, in
         quarterly installments, until the end of the Back-Up Program Term,
         with the first payment of Seven Hundred Fifty Thousand Dollars
         ($750,000) due upon the execution of this Agreement, and the next
         quarter's payment due on the first quarter anniversary thereof. 

    3.6  PARTIAL REIMBURSEMENT OF BACK-UP PROGRAM FEES.  If CO 2-6749 fails to
         meet Wyeth-Ayerst's criteria for [     *     ], and if at such time,
         no Back-Up Compound Candidate has been submitted to Wyeth-Ayerst which
         Wyeth-Ayerst agrees meets the criteria set forth in Exhibit A, then
         Wyeth-Ayerst shall have the right to so notify CoCensys and CoCensys
         will reimburse Wyeth-Ayerst fifty percent (50%) of the funds paid for
         the Back-Up Program to CoCensys as of the date of such notification
         and the Back-Up Program shall immediately terminate.  Such
         reimbursement shall be due within thirty (30) days of receipt of such
         notice, and, at CoCensys' option, shall be in the form either of cash
         or of CoCensys Common Stock.  If reimbursement is to be in CoCensys
         Common Stock,


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         CoCensys will issue to Wyeth-Ayerst that number of shares of CoCensys
         Common Stock which, when multiplied by the Market Price equals the
         amount of such reimbursement.  For purposes of this Article 3.6,
         "Market Price" shall mean the average closing price per share of
         CoCensys Common Stock for twenty (20) trading days prior to the date
         of notification of such reimbursement.

    3.7  APPLICABILITY OF THIS AGREEMENT.  Unless otherwise provided, all of
         the Parties' rights and obligations under this Agreement, including
         those regarding the development, manufacture, distribution, marketing,
         sale, promotion, profit-sharing and royalties of CO 2-6749 and the
         Product are applicable to any Back-Up Compound Candidate either
         replacing CO 2-6749 or otherwise developed in the Field.  The
         provisions herein regarding CO 2-6749 and the Product shall apply to
         such Back-Up Compound Candidate MUTATIS MUTANDIS.

4.  INDICATIONS; EXCLUSIVITY.

    4.1  INDICATIONS.  Wyeth-Ayerst shall have the right to conduct Development
         with respect to any Licensed Compound.  Wyeth-Ayerst [          *      
            ] covenants that it shall not conduct clinical trials of any
         Licensed Compound for [     *     ] in the USA except as provided
         under this Article 4.1.  If Wyeth-Ayerst discovers or determines that
         any Licensed Compound may have efficacy in the treatment of [     *    
         ] and if Wyeth-Ayerst desires to pursue clinical trials of such
         Licensed Compound for [     *     ] it will promptly notify CoCensys
         in writing and disclose to CoCensys its rationale therefor. 
         Wyeth-Ayerst shall have the right to pursue such clinical trials for [ 
            *     ] and market and sell such Licensed Compound as though it
         were a Product developed and sold for [     *     ] under this
         Agreement, subject to the Parties negotiation of terms and conditions,
         including royalty rates, whether and on what terms such Licensed
         Compound will be Co-Promoted by the Parties, and other appropriate
         payment and other terms.  Following such negotiation of such terms and
         conditions the Parties shall either enter into a separate agreement or
         amend this Agreement to so provide for such terms and conditions.  In
         the event the Parties are unable to come to agreement as to the
         appropriate terms and conditions for the development and
         commercialization of such Licensed Compound for [     *     ] by
         Wyeth-Ayerst, the matter shall be referred to the Chief Executive
         Officer of CoCensys and the President of Wyeth-Ayerst Laboratories, an
         Affiliate of Wyeth-Ayerst, for good faith resolution, for a period of
         [     *     ].  If such matter is not resolved by the end of such [    
         *     ] period, the Parties shall be [          *          ]. 
         Notwithstanding the 


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         foregoing, it is expressly understood and agreed that [     *     ] as
         used in this Agreement shall not include [          *          ].

    4.2  NO [     *     ] BY COCENSYS [     *     ].  During the term of this
         Agreement, CoCensys shall not [          *          ].

    4.3  NO [          *          ].  During the term of this Agreement,
         CoCensys will not [          *          ] except under the terms of
         this Agreement, or as otherwise agreed to by Wyeth-Ayerst.

5.  LICENSE GRANTS.

    5.1  LICENSES TO WYETH-AYERST.  Subject to the other provisions of this
         Agreement, CoCensys hereby grants to Wyeth-Ayerst:

         5.1.1   A license in the USA, under its Intellectual Property Rights,
                 to develop, manufacture and have manufactured, import, use,
                 market, offer for sale and sell Products, in the Field, and,
                 subject to Article 4.1, for any New Indication.  Such license
                 shall be exclusive except as to CoCensys, who shall have the
                 right to Promote and Co-Promote the Product in the Field, or
                 outside the Field (where agreed by the Parties pursuant to
                 Article 4.1), in the USA as and to the extent set forth in
                 this Agreement.

         5.1.2   The licenses granted in Article 5.1.1 shall not be
                 sublicensable by Wyeth-Ayerst in the USA without the consent
                 of CoCensys, such consent not to be unreasonably withheld,
                 except to Affiliates of Wyeth-Ayerst, and only for so long as
                 such Affiliates remain Affiliates.

         5.1.3   Unless otherwise provided in this Agreement, Wyeth-Ayerst
                 covenants that it shall not, nor shall it cause any Affiliate
                 to, use or practice directly or indirectly any CoCensys
                 Know-How, and, until expiration thereof, any CoCensys Patent
                 Rights for any purposes other than the development,
                 manufacture, importation, use, marketing, offer for sale or
                 sale of the Product.

    5.2  LICENSES TO COCENSYS.  Subject to the other provisions of this
         Agreement, Wyeth-Ayerst hereby grants to CoCensys:

         5.2.1   A non-exclusive license to practice and use Wyeth-Ayerst's
                 Intellectual Property Rights to the extent needed to Promote
                 and Co-Promote the Product in the Field in the USA under this
                 Agreement and otherwise comply with its obligations under this
                 Agreement;


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         5.2.2   The license granted in Article 5.2.1 shall not be
                 sublicensable by CoCensys without the consent of Wyeth-Ayerst,
                 such consent not to be unreasonably withheld, except to
                 Affiliates of CoCensys, and only for so long as such
                 Affiliates remain Affiliates.

         5.2.3   Unless otherwise provided in this Agreement, CoCensys
                 covenants that it shall not, nor shall it cause any Affiliate
                 to, use or practice directly or indirectly any Wyeth-Ayerst
                 Know-How, and until the expiration thereof, any Wyeth-Ayerst
                 Patent Rights for any purposes other than the marketing,
                 promotion and offering for sale of the Product as provided in
                 this Agreement.

    5.3  LICENSES UPON EXPIRATION.  Upon expiration of the Term of
         Co-Promotion, and provided all sums owing to CoCensys have been paid,
         Wyeth-Ayerst shall have a [          *          ] where agreed under
         Article 4.1, under any remaining CoCensys Intellectual Property
         Rights.

6.  CONSIDERATION TO COCENSYS.

    6.1  UPFRONT FEE.  In consideration for the efforts expended by CoCensys
         prior to the Effective Date and its ongoing assistance with respect to
         the identification and development of CO 2-6749, Wyeth-Ayerst shall
         pay to CoCensys, simultaneous with the execution of this Agreement,
         Five Million Dollars US (US $5,000,000).

    6.2  EQUITY INVESTMENT.  Simultaneous with the execution of this Agreement,
         Wyeth-Ayerst shall enter into a Preferred Stock Purchase Agreement
         with CoCensys, in substantially the form attached hereto as Exhibit F,
         pursuant to which Wyeth-Ayerst shall invest a total amount of Five
         Million Dollars US (US $5,000,000) in convertible preferred capital
         stock of CoCensys.

    6.3  PAYMENTS.  In further consideration of CoCensys' continuing assistance
         in research and development of the Product, Wyeth-Ayerst shall pay to
         CoCensys the following amounts at the time of the following
         achievements with respect to the Product:

         6.3.1   [          *          ]  Upon [          *          ] under
                 this Agreement or Agreement (No. 2), Wyeth-Ayerst shall make
                 to CoCensys a non-refundable payment of [        *        ].

         6.3.2   [          *          ]  Upon [     *     ] Wyeth-Ayerst shall
                 promptly notify CoCensys in writing of such determination and
                 shall make to CoCensys a non-refundable payment of [    *   ].


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         6.3.3   [     *     ].  Upon the [          *          ] Wyeth-Ayerst
                 shall make to CoCensys a non-refundable payment of [         
                 *          ].

         6.3.4   [     *     ].  Upon [     *     ] for the Product,
                 Wyeth-Ayerst shall make to CoCensys a non-refundable payment
                 of [          *          ].

         6.3.5   [     *     ].  Upon [          *          ] Wyeth-Ayerst
                 shall make to CoCensys a non-refundable payment of [     *    
                 ] if the Product is a [     *     ] Product or [     *     ]
                 if the Product is a [     *     ] Product.


    6.4  METHOD OF PAYMENT OF PAYMENTS.  All payments shall be made by
         Wyeth-Ayerst to CoCensys by way of wire transfer to CoCensys within
         thirty (30) days from the date corresponding to the event triggering
         the milestone payment.

    6.5  PAYMENTS FOR BACK-UP COMPOUND CANDIDATES.  Each payment payable
         pursuant to this Article 6 shall [     *     ] be payable [     *    
         ] for the Product [          *          ].

    6.6  ROYALTIES AND PROFIT SHARING.  Wyeth-Ayerst shall, in addition to the
         payments set forth above, also pay to CoCensys royalties and such
         other amounts as set forth in Article 7.

7.  CO-PROMOTION OF THE PRODUCT IN THE USA.

    7.1  PROMOTION AND CO-PROMOTION RIGHTS.

         7.1.1   COCENSYS' RIGHTS TO PROMOTE AND CO-PROMOTE.  With respect to
                 the commercialization of the Product in the USA,
                 notwithstanding the exclusive rights granted to Wyeth-Ayerst,
                 CoCensys shall have:  (i) the right to Promote the Product in
                 the Neurologist Market, and (ii) the right to Co-Promote the
                 Product in the Psychiatrist Market during the Term of
                 Co-Promotion.  The Parties agree and understand that all other
                 rights to Promote, market and otherwise commercialize the
                 Product shall reside with Wyeth-Ayerst, including in
                 particular, the right to Promote the Product in All Other
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    7.1.2     CONDUCT OF PROMOTION AND CO-PROMOTION.  CoCensys and Wyeth-Ayerst
              shall each use Commercially Reasonable Efforts to Promote and
              Co-Promote the Product pursuant to the terms and conditions
              hereof.  The Joint Marketing Committee shall oversee and
              implement all such Promotion and Co-Promotion activities, based
              on the principle of maximizing profits from sales of the Product
              in the USA during the Term of Co-Promotion.  Each Party shall
              cause its sales force, and all other employees and approved
              agents and representatives, to comply with all applicable laws,
              regulations and guidelines in connection with the Co-Promotion of
              the Product, including the Prescription Drug Marketing Act and
              the Federal Anti-Kickback Statute.

    7.1.3     ELECTION OF CO-PROMOTION RIGHT.  CoCensys shall provide
              Wyeth-Ayerst written notice prior to [     *     ] for the
              Product as to whether CoCensys elects to exercise its right to
              Promote and Co-Promote the Product in the USA.  If CoCensys
              elects not to so participate, Wyeth-Ayerst shall have the
              exclusive right to commercialize, market, Promote and sell the
              Product in the USA, subject to the payment to CoCensys of a
              running royalty on Net Sales in the USA at the rates set forth in
              Article 7.1.5.

    7.1.4     TERMINATION OF RIGHTS BY COCENSYS.  Notwithstanding an election
              by CoCensys to Promote and Co-Promote the Product, CoCensys may
              elect to forego its right to Promote and Co-Promote the Product
              if [          *          ] upon [     *     ] months prior
              written notice to Wyeth-Ayerst.

    7.1.5     ROYALTIES IN THE EVENT COCENSYS DOES NOT PROMOTE AND CO-PROMOTE.
              In the event (i) CoCensys elects not to Promote and Co-Promote
              the Product pursuant to Article 7.1.3, (ii) CoCensys elects to
              cease to Promote and Co-Promote the Product pursuant to Article
              7.1.4, or (iii) CoCensys's rights to Promote and Co-Promote the
              Product are terminated pursuant to Article 13.4 or Article
              13.7.1, Wyeth-Ayerst shall have the exclusive right to market,
              sell and Promote the Product in the USA and CoCensys shall
              receive a running royalty on Net Sales in the USA until the end
              of the Term of Co-Promotion as follows:

                   (a)  [     *     ] PRODUCT ROYALTY.  If the Product is a
                        [     *     ] Product, Wyeth-Ayerst shall pay to
                   CoCensys the following running marginal royalty:


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                   (i)       For annual Net Sales of all [     *     ] Products
                             which are less than or equal to [     *     ]
                             million, [     *     ] of such Net Sales per year;
                             and

                   (ii)      For annual Net Sales of all [     *     ] Products
                             which are more than [     *     ] million but less
                             than or equal to [     *     ] million,
                             [     *     ] of such Net Sales per year; and

                   (iii)     For annual Net Sales of all [     *     ] Products
                             which are more than [     *     ] million,
                             [     *     ] of such Net Sales per year.

              (b)  [     *     ] PRODUCT ROYALTY.  If the Product is a
                   [     *     ] Product, Wyeth-Ayerst shall pay to CoCensys
                   the following running marginal royalty:

                   (i)       For annual Net Sales of all [     *     ] Products
                             which are less than or equal to [     *     ]
                             million, [     *     ] of such Net Sales per year;
                             and

                   (ii)      For annual Net Sales of all [     *     ] Products
                             which are more than [     *     ] million but less
                             than or equal to [     *     ] million, [     *
                             ] of such Net Sales per year; and

                   (iii)     For annual Net Sales of all [     *     ] Products
                             which are more than [     *     ] million, [     *
                                ] of such Net Sales per year.

    7.1.6     TERMINATION OF RIGHTS BY WYETH-AYERST.  Wyeth-Ayerst may elect to
              forego its right to Promote and Co-Promote the Product at any
              time following [     *     ] months prior written notice to
              CoCensys, in


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              which case CoCensys shall obtain the exclusive, subject to
              Wyeth-Ayerst's retained right to manufacture Product in the USA
              for sale outside the USA right (with the right to sublicense) to
              manufacture, have manufactured, use, market and sell the Product
              in the USA, and Wyeth-Ayerst shall receive a running royalty on
              Net Sales in the USA until the end of the Term of Co-Promotion as
              follows:

                   (a)  [     *     ] PRODUCT ROYALTY.  If the Product is a
                        [     *     ] Product, CoCensys shall pay to Wyeth-
                        Ayerst the following running marginal royalty:

                        (i)       For annual Net Sales of all [     *     ]
                                  Products which are less than or equal to
                                  [     *     ] million, [     *     ] of such
                                  Net Sales per year; and

                        (ii)      For annual Net Sales of all [     *     ]
                                  Products which are more than [     *     ]
                                  million but less than or equal to
                                  [     *     ] million, [     *     ] of such
                                  Net Sales per year; and

                        (iii)     For annual Net Sales of all [     *     ]
                                  Products which are more than [     *     ]
                                  million, [     *     ] of such Net Sales per
                                  year.

                   (b)  [     *     ] PRODUCT ROYALTY.  If the Product is a
                        [     *     ] Product, CoCensys shall pay to Wyeth-
                        Ayerst the following running marginal royalty:

                        (i)       For annual Net Sales of all [     *     ]
                                  Products which are less than or equal to
                                  [     *     ] million, [     *     ] of such
                                  Net Sales per year; and


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                        (ii)    For annual Net Sales of all [     *     ]
                                Products which are more than [     *     ]
                                million but less than or equal to [     *     ]
                                million, [     *     ] of such Net Sales per
                                year; and

                        (iii)   For annual Net Sales of all [     *     ]
                                Products which are more than [     *     ]
                                million, [     *     ] of such Net Sales per
                                year.

              In the event Wyeth-Ayerst makes the election set forth in this
              Article 7.1.6, Wyeth-Ayerst shall [     *     ].

    7.1.7     NO REINSTATEMENT.  A Party's rights to Promote or Co-Promote the
              Product may not be reinstated after delivery of a notice of early
              termination thereof.

7.2 JOINT MARKETING COMMITTEE.  The Parties agree that the Promotion and
    Co-Promotion will be managed by a Joint Marketing Committee (the "JMC").

    7.2.1     COMPOSITION.  No later than the Beginning of Phase III for the
              Product, each of the Parties will appoint [     *     ]
              representatives to the JMC.  The chairperson of the JMC will be
              [     *     ].  A Party may change any of its representatives at
              any time by giving written notice to the other Party.

    7.2.2     RESPONSIBILITIES.  The JMC will:

              (a)  monitor compliance with the Marketing Plan and approve any
                   immaterial change in the Marketing Plan; and

              (b)  oversee the Promotion and Co-Promotion as discussed in this
                   Article 7, including determining the appropriate level of
                   effort of each Party in the markets in which they Co-Promote
                   in a manner commensurate with each Party's economic interest
                   in such market.

    7.2.3     MEETINGS OF THE JMC.  The chairperson of the JMC shall call
              meetings when deemed appropriate, currently anticipated to be no
              less frequently than once every three (3) months.  If possible,
              the meetings shall be held in person, or where appropriate, by
              video or telephone conference.  The chairperson shall determine
              the form of the meeting.  Additional participants may be invited
              by any member to attend meetings where


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              appropriate (e.g., representatives of regulatory affairs or
              outside consultants).  Such additional participants shall have no
              vote.  Minutes of each meeting of the JMC shall be exchanged for
              review and comment by the members.  Thereafter, they shall be
              signed by the chairperson.

    7.2.4     VOTING OF THE JMC. The JMC shall make decisions by majority vote,
              with at least one consenting vote of each Party's JMC members.
              If the required majority for a decision cannot be found and all
              the members of each Party take the same opposing positions in a
              matter which either Party deems to be of major importance, the
              matter shall be handled pursuant to Article 7.2.6.  Voting by
              proxy is permissible.  Urgent matters (including regulatory and
              adverse event matters) may be decided by unanimous vote of the
              chairperson and a representative designated by CoCensys.

    7.2.5     ROLE OF CHAIRPERSON.  Except as explicitly set forth herein, in
              no event shall the chairperson of the JMC have any additional
              powers or responsibilities beyond those delegated to such person
              by virtue of such person's membership on the JMC.  Without
              limiting the foregoing, it is understood that, except as a voting
              member of the JMC, the chairperson shall not have the power to
              control or dictate decisions or to veto any decisions reached by
              the committee under the decision-making processes set forth in
              Article 7.2.4.

    7.2.6     DISPUTE RESOLUTION.  If the JMC is unable to resolve, after
              thirty (30) days, a dispute regarding any issue presented to it
              or arising in it, such dispute will be referred to the Chief
              Executive Officer of CoCensys and the President of Wyeth-Ayerst
              Laboratories, an Affiliate of Wyeth-Ayerst for good faith
              resolution, for a period of ninety (90) days.  If such dispute is
              not resolved by the end of such ninety (90) day period, the
              Parties shall be free to pursue any legal or equitable remedy
              available to them.

7.3 MARKETING PLAN.  The Promotion and Co-Promotion of the Product will be
    governed by a marketing plan (the "Marketing Plan").  The Marketing Plan
    will describe fully, to the extent practicable, the proposed plan for
    commercialization of the Product in the USA, including overall marketing
    strategy, anticipated marketing, sales and promotion efforts by each Party
    in each of the Neurologist Market, the Psychiatrist Market and All Other
    Markets, market and sales forecasts, pricing analysis and estimated launch
    date, guidelines for discounting the Product, as well as advertising and
    other promotional materials to be used in the Promotion and Co-Promotion.
    The Marketing Plan will be prepared by Wyeth-Ayerst, after consultation
    with representatives of CoCensys, and will take into consideration factors
    such as market conditions, regulatory factors and competition.  The initial
    Marketing Plan shall be prepared under the direction of and adopted by the
    JMC no later than six (6) months after the first filing of the NDA for the
    Product (unless otherwise agreed by the Parties).  Such Marketing


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    Plan shall thereafter be reviewed and, where necessary, updated, at least
    every three (3) months (or more frequently if so determined by the JMC).

7.4 SALES FORCE EXPENSES.  [          *          ].

7.5 DETERMINATION AND ALLOCATION OF GROSS MARGIN AND ROYALTIES.

    7.5.1     PSYCHIATRY MARKET.  In consideration for each Party's
              Co-Promotion efforts in the Psychiatry Market, Wyeth-Ayerst shall
              be entitled to [          *          ] and CoCensys shall be
              entitled to [     *     ] of the Gross Margin from sales of the
              Product in the Psychiatry Market, as determined by a Prescription
              Audit.

    7.5.2     NEUROLOGIST MARKET.  In consideration for CoCensys' Promotion
              efforts in the Neurologist Market, CoCensys shall be entitled to
              [     *     ] and Wyeth-Ayerst shall be entitled to [     *     ]
              of the Gross Margin from sales of the Product in the Neurologist
              Market, as determined by a Prescription Audit.

    7.5.3     ALL OTHER MARKETS.  In consideration for Wyeth-Ayerst's Promotion
              efforts in All Other Markets, Wyeth-Ayerst shall be entitled to
              [     *     ] of the Gross Margin from sales of the Product in
              All Other Markets, as determined by a Prescription Audit, and
              shall pay to CoCensys a running royalty on Net Sales in the USA
              until the end of the Term of Co-Promotion as follows:

                   (a)  [     *     ] PRODUCT ROYALTY.  If the Product is a
                        [     *     ] Product, Wyeth-Ayerst shall pay to
                        CoCensys the following running marginal royalty:

                        (i)     For annual Net Sales of all [     *     ]
                                Products which are less than or equal to
                                [     *     ] million, [     *     ] of such
                                Net Sales per year; and

                        (ii)    For annual Net Sales of all [     *     ]
                                Products which are more than [     *     ]
                                million but less than or equal to [     *     ]
                                million, [     *     ] of such Net Sales per
                                year; and


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                        (iii)   For annual Net Sales of all [     *     ]
                                Products which are more than [     *     ]
                                million, [     *     ] of such Net Sales per
                                year.

                   (b)  [     *     ] PRODUCT ROYALTY.  If the Product is a
                        [     *     ] Product, Wyeth-Ayerst shall pay to
                   CoCensys the following running marginal royalty:

                        (i)     For annual Net Sales of all [     *     ]
                                Products which are less than or equal to
                                [     *     ] million, [     *     ] of such
                                Net Sales per year; and

                        (ii)    For annual Net Sales of all [     *     ]
                                Products which are more than [     *     ]
                                million but less than or equal to [     *     ]
                                million, [     *     ] of such Net Sales per
                                year; and

                        (iii)   For annual Net Sales of all [     *     ]
                                Products which are more than [     *     ]
                                million, [     *     ] of such Net Sales per
                                year.

7.6 ADJUSTMENT TO ROYALTIES.

    7.6.1     GENERIC PRODUCTS.  In the event that, during the Term of
              Co-Promotion, a generic version (i.e., same chemical entity) of
              the Product is introduced in the USA by a Third Party, and if
              unit sales for all such generic product(s) constitute more than
              [     *     ] of the combined unit sales in the USA of both the
              Product and any such generic product(s), then the annual royalty
              amount owed by one Party under Article 7.1.5, 7.1.6 or 7.5.3
              shall be reduced by [     *     ] such reduction to be done in
              the fourth quarter payment as described in Article 7.8.

    7.6.2     [     *     ]  In the event one Party (the "Royalty Paying
              Party") owes royalties to the other Party (the "USA Royalty
              Receiving Party") pursuant to Article 7.1.5, 7.1.6 or 7.5.3
              hereunder with respect to Net Sales in the USA and, at the end of
              a given calendar year [     *     ] (where [


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                    *     ] = [          *          ]= [          *          ];
              and [     *     ]= [     *     ] then the Royalty Paying Party
              will provide written notice to the USA Royalty Receiving Party of
              such fact and the Parties shall meet promptly thereafter to
              discuss and develop in good faith a commercially reasonable plan
              to [          *          ].  In the event that, at any time after
              the eight (8) month anniversary of the date of the first meeting
              to discuss the [     *     ] (where [     *     ] =
              [          *          ] then, for so long as [     *     ], an
              amount equal to [     *     ] may be deducted from the royalty
              due the USA Royalty Receiving Party for such year; PROVIDED,
              HOWEVER, in no event shall the royalty due the USA Royalty
              Receiving Party be less than that paid at the lowest applicable
              rate (i.e., [     *     ] for [     *     ] Products and
              [     *     ] for [     *     ] Products, or [     *     ]
              respectively, where Article 7.6.1 applies) set forth in Article
              7.1.5, 7.1.6 or 7.5.3.

    7.7   PRESCRIPTION AUDIT.  Wyeth-Ayerst shall retain, at its own cost, a
          Third Party such as IMS America, Ltd. to conduct an audit of the
          prescribing activity in all markets and to provide the prescription
          data necessary to calculate Net Sales in each of the Neurologist
          Market, the Psychiatry Market and All Other Markets (the
          "Prescription Audit").  Wyeth-Ayerst will provide to CoCensys such
          data consistent with its obligations to IMS and such data will be
          the property of Wyeth-Ayerst.

    7.8   PAYMENT AND REPORTING.  Within three (3) months after the close of
          each calendar quarter, or earlier if possible, during the Term of
          Co-Promotion (i.e., on or before the last day of each of the months
          of June, September, December and March), Wyeth-Ayerst shall furnish
          to CoCensys a statement (the "P&L Statement") setting forth Net
          Sales in the USA and all data on which the determination of Gross
          Margin was calculated.  Wyeth-Ayerst will submit any amount due to
          CoCensys pursuant to Articles 7.1, 7.5 and 7.6 with the P&L
          Statement.  For any given royalty period during the first three
          quarters of the year, Wyeth-Ayerst shall pay to CoCensys the royalty
          at the lowest rate specified in Articles 7.1.5 or 7.5.3 applicable
          to the then current year-to-date Net Sales level in the USA.  Each
          statement provided at the end of the fourth quarter shall contain a
          reconciliation of actual royalty payments made during that year and
          the amount actually owed for such year, and any amounts owing to
          CoCensys shall be paid to CoCensys at the time of such fourth
          quarter statement, in accordance with the terms of this Article 7.8.
          If the Term of Co-Promotion ends during an accounting quarter, the
          amounts due hereunder shall be calculated for such shortened
          calendar quarter.  Any adjustments to royalties owed in the USA


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          pursuant to Articles 7.6.1 and 7.6.2 shall be done at the end of the
          calendar year in which such event giving rise to such adjustment
          occurred; PROVIDED, HOWEVER, that following the entry of one or more
          generic products in any year, and where royalties were reduced for
          that year pursuant to Article 7.6.1, the following year's royalty
          rate for quarterly royalty payments shall be at [     *     ] with a
          reconciliation upward at year end in the event sales of such generic
          product(s) do not rise to the level specified in Article 7.6.1.

    7.9   PROMOTIONAL AND ADVERTISING MATERIALS.  The Parties shall
          disseminate in the USA only those promotional and advertising
          materials which have been provided or approved for use by the Joint
          Marketing Committee, the cost of which shall be the responsibility
          of Wyeth-Ayerst.  All such materials shall be consistent with the
          relevant Marketing Plan approved by the Joint Marketing Committee
          and neither Party shall make any claims or representations in
          respect of the Product that have not been approved by the Joint
          Marketing Committee.  All such written and visual materials and all
          documentary information, promotional material, and oral
          presentations (where practical) regarding the promotion of the
          Product will state this arrangement and will display the
          Wyeth-Ayerst and CoCensys names and logos with equal prominence, as
          permitted by applicable law.

    7.10  PRICING.  The Parties will discuss, and the Marketing Plan will
          include, the general operating guidelines and strategies for the
          pricing and discounting of the Product in the USA; PROVIDED,
          HOWEVER, that [          *          ] as to pricing and discounting
          in the USA.

    7.11  NO DELEGATION.  Each of the Parties may use only its own employees
          or the employees of one or more of its Affiliates in the course of
          exercising its Promotion and Co-Promotion rights under this
          Agreement, unless an alternative arrangement is approved in advance
          by the JMC.  Notwithstanding the foregoing, in the event CoCensys is
          exclusively marketing, selling, or promoting the Product in the USA,
          it shall be free to delegate or sublicense such rights to any Third
          Party.

    7.12  RETURNS.  Wyeth-Ayerst shall be responsible for handling all returns
          relating to Product.  Any Product returned to CoCensys shall be
          shipped by CoCensys to the address designated by Wyeth-Ayerst.

    7.13  ORDERS.  All customer orders for the Product shall be received and
          executed by Wyeth-Ayerst.

    7.14  SAMPLES.  Each of the Parties will keep accurate records as to the
          distribution of samples of Products and comply with all applicable
          laws, rules and regulations dealing with the distribution of
          samples.


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    7.15  COMPLETION OF SALES.  All sales of the Product will be completed,
          distributed, accounted for, billed and booked by Wyeth-Ayerst.

    7.16  TRAINING.  Consistent with the Marketing Plan, but not less than
          ninety (90) days prior to the commencement of the Term of
          Co-Promotion for the Product, Wyeth-Ayerst and CoCensys shall
          conduct joint initial training of each Party's sales force at a site
          to be determined by the JMC.  [          *          ]

    7.17  EXCHANGE OF MARKETING INFORMATION.  From time-to-time the Joint
          Marketing Committee will develop call lists, schedules, and other
          appropriate information for the purpose of determining the
          physicians and other persons involved in the drug purchase
          decision-making process to whom CoCensys and Wyeth-Ayerst,
          respectively, may detail and otherwise promote each Product.  The
          Parties agree to cooperate in finding an inexpensive and expeditious
          way to provide a call list and other information indicating the
          identity of those physicians and other persons involved in the
          decision-making process regarding the purchase of pharmaceuticals.

8.  ACCOUNTS AND RECORDS; WITHHOLDING TAX.

    8.1   RECORDS.  Wyeth-Ayerst shall keep accurate books and accounts of
          record in connection with the manufacture, use and/or sale by or for
          it of the Products in sufficient detail to permit accurate
          determination of all figures necessary for verification of
          royalties, profits, milestone payments and other compensation
          required to be paid hereunder.  Wyeth-Ayerst shall maintain such
          records for a period of three (3) years after the end of the year in
          which they were generated.

    8.2   AUDITS.  CoCensys, through an independent certified public
          accountant reasonably acceptable to Wyeth-Ayerst, shall have the
          right, at its own expense, to access the books and records of
          Wyeth-Ayerst for the sole purpose of verifying statements furnished
          by Wyeth-Ayerst pursuant to Article 7.8.  Such access shall be
          conducted after reasonable prior written notice to Wyeth-Ayerst and
          during ordinary business hours and shall not be more frequent than
          once during each calendar year.  CoCensys agrees to keep in strict
          confidence all information learned in the course of such audit,
          except when it is necessary to reveal such information in order to
          enforce its rights under this Agreement.  CoCensys' right to have
          such records examined shall survive termination or expiration of
          this Agreement.  In the event such audit reveals an underpayment of
          [     *     ] or more of the amount actually due, Wyeth-Ayerst shall
          reimburse CoCensys for the costs of such audit in addition to
          promptly remitting to CoCensys the amount of any underpayment.

    8.3   SALES BY SUBLICENSEES.  In the event Wyeth-Ayerst grants licenses or
          sublicenses to others to make or sell the Product, such licenses or
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         an obligation for the licensee or sublicensee to account for and
         report its Net Sales of such Products on the same basis as if such
         sales were Net Sales by Wyeth-Ayerst, and CoCensys shall receive
         royalties in the same amounts as if the Net Sales of the licensee or
         sublicensee were Net Sales of Wyeth-Ayerst.

    8.4  WITHHOLDING.  All taxes, assessments and fees of any nature levied or
         incurred on account of any payments accruing under this Agreement, by
         national, state or local governments, will be assumed and paid by
         Wyeth-Ayerst, except taxes levied thereon as income to CoCensys and if
         such taxes are required to be withheld by Wyeth-Ayerst they will be
         deducted from payments due to CoCensys and will be timely paid by
         Wyeth-Ayerst to the proper taxing authority for the account of
         CoCensys, a receipt or other proof of payment therefor secured and
         sent to CoCensys as soon as practicable.

9.  TRADEMARKS.

    [     *     ] shall select and own the Trademarks for marketing the Product
    in the USA.  [     *     ] for (i) registration of such Trademarks and
    (ii) bringing, maintaining and prosecuting any action to protect or defend
    such Trademarks shall be borne [          *          ]  At the termination
    of this Agreement, [     *     ] shall continue to have unrestricted
    ownership of such Trademark(s) in the USA.  [     *     ] rights in this
    Article are subject to Article 7.1.6.

10. MANUFACTURING AND DISTRIBUTION.

    10.1 PRIMARY MANUFACTURE.  [     *     ] shall manufacture or have
         manufactured its requirements for clinical and commercial supplies of
         the Product.  In fulfilling its manufacturing obligations hereunder, 
         [     *     ] will use at least the same level of effort as it employs
         for its other products of similar scientific and commercial promise. 
         If [     *     ] elects to have the Product manufactured, 
         [     *     ] shall favorably consider using, but shall not be 
         obligated to use, [          *          ] as its manufacturing 
         sublicensee.

    10.2 SECOND SOURCE.  In order to ensure an uninterrupted supply of the
         Product, the Parties intend to identify a Third Party manufacturer
         (the "Second Source") to manufacture the Product in the event that 
         [     *     ] is unable to supply all of the reasonably anticipated
         requirements of the Product.  If the Second Source manufactures the
         Product pursuant to this Article 10.2, Wyeth-Ayerst and CoCensys shall
         cooperate and assist each other to obtain, transfer or use any
         licenses, registrations or information reasonably required to permit
         such Second Source to manufacture the Product.


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    10.3 EXCHANGE OF INFORMATION.  Subject to Article 17, the Parties undertake
         to exchange and to use diligent efforts to cause Third Party
         manufacturers to exchange, on a regular basis, all data and know-how
         relating to the manufacture of the Product.

    10.4 COMPLIANCE.  Any manufacture of the Product for sale in the USA shall
         be performed in full compliance with United States GMP and all
         applicable laws and regulations.  The JMC shall be entitled to audit
         such compliance and in particular the quality assurance program for
         the manufacture of the Product.

11. PROSECUTION, MAINTENANCE AND INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS.

    11.1 PATENTABLE INVENTIONS.

         11.1.1    Wyeth-Ayerst shall own all Inventions made solely by
                   itsemployees and agents, and all patent applications and
                   patents claiming such Inventions.  CoCensys shall own all
                   Inventions made solely by its employees and agents, and all
                   patent applications and patents claiming such Inventions. 
                   All Inventions made jointly by employees or agents of
                   CoCensys and employees or agents of Wyeth-Ayerst and all
                   patent applications and patents claiming such Inventions
                   shall be owned jointly by CoCensys and Wyeth-Ayerst.  All
                   determinations of inventorship under this Article 11.1.1
                   shall be in accordance with U.S. law.

         11.1.2    Wyeth-Ayerst and CoCensys shall each disclose to the other
                   and discuss any Inventions and the desirability of filing a
                   United States patent application covering the Invention, as
                   well as any foreign counterparts.  The Party owning the
                   Invention shall make the final decision with respect to any
                   such filings.  With respect to jointly owned Inventions, the
                   Parties shall determine which Party shall file and prosecute
                   any patent applications thereon.  [     *     ] shall be
                   responsible for expenses for preparing and prosecuting joint
                   patent applications in the USA.

         11.1.3    Each Party shall have the right to select patent counsel and
                   to take such other actions as are reasonably appropriate to
                   prepare, file, prosecute and maintain patent protection with
                   respect to its Inventions arising under this Article 11.1.

    11.2 PROSECUTION AND MAINTENANCE OF PATENT RIGHTS.  In the USA, each Party
         shall be responsible for prosecuting and maintaining its own Patent
         Rights, subject to Article 11.1.2.  To facilitate such
         decision-making, each Party will appoint a "patent coordinator", who
         will have the authority to make such decision on behalf 


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         of such Party.  All expenses for filing, prosecuting and maintaining
         the CoCensys Patent Rights in the USA shall be borne [     *     ]

    11.3 PATENT EXTENSIONS.  The Party holding a Patent Right, if requested by
         and with the assistance of the other Party, shall apply in a timely
         manner for such patent term extensions or patent restoration
         certificates for such Patent Right as are available under the Federal
         Drug Price Competition and Patent Term Restoration Act of 1984 (Pub.
         L. No. 98-417), and any amendments thereof or any successor acts
         thereto in the USA.  [     *     ] expenses incurred in connection
         with such patent term extensions or patent restoration certificates
         shall be borne [          *          ].

    11.4 COOPERATION.  Each of the Parties shall execute or have executed by
         its appropriate employees, representatives, agents, and contractors
         such documents as may be necessary to obtain, perfect or maintain any
         Patent Rights filed or to be filed pursuant to this Agreement, and to
         cooperate with the other Party so far as reasonably necessary with
         respect to furnishing all information and data in its possession
         reasonably necessary to obtain or maintain such Patent Rights.

    11.5 INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS.

         11.5.1

              (a)  If either Party should become aware of any infringement or
                   threatened infringement or misappropriation, as the case may
                   be, in the USA of any Intellectual Property Rights of the
                   other Party, it shall promptly notify such other Party in
                   writing.  As soon as practicable the Parties shall confer on
                   the particulars of such infringement or misappropriation and
                   the possible courses of action to be taken.  The Party
                   holding the affected Intellectual Property Rights shall have
                   the right, but not the obligation, to institute, prosecute
                   and control any legal proceedings in its own name and by its
                   own counsel and at its own expense, subject to
                   Article 11.5.1(d), to prevent or restrain such infringement,
                   and the other Party shall have the right, [     *     ] to
                   be represented in such action by its own counsel.  If one
                   Party brings any such action or proceeding, the other Party
                   hereby consents to being joined as a party plaintiff where
                   necessary and, in case of joining, such other Party agrees
                   to give the first Party reasonable assistance and authority
                   to file and to prosecute such suit, at the exercise of the
                   Party bringing such suit.


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              (b)  Notwithstanding the foregoing, the Parties shall jointly
                   determine which Party shall have the primary right and
                   responsibility (but not the obligation) to institute,
                   prosecute, and control any action or proceeding with respect
                   to infringement or misappropriation of jointly owned
                   Intellectual Property Rights in the USA and the other Party
                   shall have the right, [     *     ] to be represented by its
                   counsel.  Each Party hereby consents to the filing of any
                   such action by the other Party with respect to any jointly
                   owned Patent Rights in accordance with this Article
                   11.5.1(b).

              (c)  If one Party alone prosecutes an infringement or
                   misappropriation of Intellectual Property Rights, 
                   [         *         ] any damages and costs recovered in 
                   any proceedings or by way of settlement under Articles 
                   11.5.1(a) and 11.5.1(b) above or Article 11.5.2 shall 
                   [         *         ] as applicable.

              (d)  If both Parties participate in prosecuting an infringement
                   or misappropriation of Intellectual Property Rights, the
                   actual costs and expenses of all suits brought by either
                   Party under this Article 11.5.1 shall be [        *        ] 
                   Any remaining damages shall then be split [     *     ] to
                   CoCensys and [     *     ] to Wyeth-Ayerst.

         11.5.2    If the Party having the primary right to institute,
                   prosecute, and control such infringement or misappropriation
                   action under Article 11.5.1 fails to do so within a period
                   of one hundred twenty (120) days after receiving notice of
                   the infringement, or if that Party, after initiating an
                   action, determines to discontinue such action, the other
                   Party shall have the right to bring and control or take over
                   any such action by counsel of its own choice, and at its own
                   expense, subject to Article 11.5.1(c) unless prevented from
                   doing so by the laws of the country where the infringement
                   or misappropriation occurred or is threatened.

         11.5.3    In connection with any proposed settlement in respect of any
                   infringement or threatened infringement of any Intellectual
                   Property Rights, the Party intending to settle shall notify
                   and consult with the other Party as to the terms of
                   settlement, whose written consent shall be required prior to
                   any such settlement, such consent shall not be unreasonably
                   withheld.

         11.5.4    In connection with any action taken by either Party against
                   a Third Party to protect or enforce any Intellectual
                   Property Rights, the 


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                   other Party shall, if requested, consult with the Party
                   taking such action, and make available as witnesses its
                   employees or as evidence any materials, and/or data as are
                   reasonably necessary for the furtherance of such action. 
                   The expenses in connection with the providing of witnesses
                   and/or the making available of any materials and/or data
                   shall be [          *          ]

11.6     INFRINGEMENT OF THIRD PARTY PATENT RIGHTS.

         11.6.1    If Wyeth-Ayerst should be of the opinion that it cannot
                   make, import, use, market and/or sell the Product in the USA
                   under its own Intellectual Property Rights or those licensed
                   to it by CoCensys under this Agreement without infringing a
                   Third Party's patent, it shall notify CoCensys.  Both
                   Parties then shall seek an opinion of patent counsel
                   acceptable to both Parties.  If such patent counsel concurs
                   with Wyeth-Ayerst's opinion, they shall jointly or
                   independently endeavor to secure a license from the Third
                   Party on terms that are acceptable to both Parties.

         11.6.2    If, in the opinion of patent counsel selected under
                   Article 11.6.1, the Third Party patent, if litigated, would
                   be found invalid or not be infringed by the manufacture or
                   sale of the Product or if the Parties otherwise mutually
                   agree to obtain a license to such Third Party patent, the
                   Parties shall proceed in accordance with the terms of this
                   Agreement, unless an action for infringement is brought
                   against one or both Parties.

         11.6.3    If either Party is sued for patent infringement of any Third
                   Party patents arising out of the manufacture, use, sale or
                   importation of the Product in the USA, the Parties shall
                   promptly meet to discuss the course of action to be taken to
                   resolve or defend any such infringement litigation.  Each
                   Party shall provide the other with such assistance as is
                   reasonably necessary and shall cooperate in the defense of
                   any such action.  [     *     ] of any cost/expense of
                   defending such action incurred by Wyeth-Ayerst in the USA
                   and any damages and/or other compensation imposed on
                   Wyeth/Ayerst in such country may be deducted by Wyeth-Ayerst
                   from any amounts otherwise due CoCensys under this Agreement
                   in the form of royalties and/or profit-sharing for the USA,
                   PROVIDED, HOWEVER, in no event shall royalty and/or profit
                   sharing amounts due CoCensys for such country be reduced by
                   more than [     *     ] in any given calendar year as a
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12. FORCE MAJEURE.

    Neither Party shall be liable to the other for delay or failure in the
    performance of the obligations on its part contained in this Agreement if
    and to the extent that such failure or delay is due to circumstances beyond
    its control which it could not have avoided by the exercise of reasonable
    diligence.  It shall notify the other Party promptly should such
    circumstances arise, giving an indication of the likely extent and duration
    thereof, and shall use all commercially reasonable efforts to resume
    performance of its obligations as soon as practicable.

13. TERM AND TERMINATION.

    13.1 GENERAL CONDITIONS OF EXPIRATION AND TERMINATION.

         13.1.1    Any permitted sublicenses granted hereunder shall
                   automatically terminate or expire at the same time as this
                   Agreement expires (insofar as they haven't already
                   terminated), except where, and to the extent, any license
                   granted hereunder survives expiration of this Agreement, as
                   expressly provided in this Agreement.  Upon early
                   termination of this Agreement for any reason, if any
                   permitted sublicensee is not then in default under its
                   sublicense agreement with Wyeth-Ayerst, then such
                   sublicensee shall automatically have a license under this
                   Agreement as a direct licensee of CoCensys, on economic
                   terms as are set forth herein with respect to Wyeth-Ayerst
                   and otherwise with the same rights and obligations as
                   Wyeth-Ayerst under this Agreement.

         13.1.2    The provisions of Articles 8, 9, 11, 14, 15, and 17 shall
                   survive termination or expiration of this Agreement.

         13.1.3    Termination or expiration of this Agreement shall not
                   operate to deprive either Party of any rights or remedies
                   either at law or in equity or to relieve either Party of any
                   of its obligations incurred prior to the effective date of
                   such termination or expiration.

    13.2 TERM.  Unless earlier terminated as set out in this Agreement, the
         term of this Agreement shall end when all the respective royalty and
         profit payment obligations of the Parties under this Agreement have
         expired.

    13.3 TERMINATION FOR BREACH.

         13.3.1    TERMINATION FOR BREACH.  Except as otherwise provided in
                   this Section 13.3.1, either Party may terminate this
                   Agreement for material breach by the other Party, which
                   breach remains uncured for [     *     ] in the case of
                   nonpayment of any amount due 


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                   and [     *     ] for all other breaches, each measured from
                   the date written notice of such breach is given to the
                   breaching party, or, if such breach is not susceptible of
                   cure within such [     *     ] period and the breaching
                   party uses diligent good faith efforts to cure such breach,
                   for [     *     ] after written notice to the breaching
                   party.

         13.3.2    BREACH BY WYETH-AYERST.  If termination is due to a material 
                   breach by Wyeth-Ayerst, all rights granted to Wyeth-Ayerst
                   under this Agreement shall revert to CoCensys, provided that
                   [          *          ] as of the date of such termination.

    13.4 BREACH BY COCENSYS.  In the event of an uncured material breach by
         CoCensys, [          *          ] subject to the payment of royalties
         as provided in Article 7.1.5.

    13.5 NO LIMIT ON REMEDIES.  Nothing herein shall exclude or limit any
         remedies or entitlements whatsoever which the law confers to either
         Party in the event of a breach of contractual obligations by the other
         Party.

    13.6 UNILATERAL TERMINATION BY WYETH-AYERST.  Wyeth-Ayerst shall have the
         right to unilaterally terminate this Agreement upon [     *     ]
         written notice.  In the event of such termination by Wyeth-Ayerst, all
         Wyeth-Ayerst's worldwide rights to the Licensed Compound and the
         Product shall revert to CoCensys.  Wyeth-Ayerst shall not be obligated
         to further fund the Development or the Back-Up Program or to make any
         other payments under this Agreement for events which occur after the
         effective date of such termination.  After the termination date,
         Wyeth-Ayerst will make its relevant personnel, relevant data and other
         resources available as are reasonably necessary to effect an orderly
         transition of Development and commercialization of the Product for a
         period of [     *     ] after termination.  In the event of such
         termination, Wyeth-Ayerst shall (i) [          *          ] (ii)
         transfer to CoCensys [          *          ] and (iii) 
         [          *           ]

    13.7 DETERMINATION OF CO-PROMOTION RIGHTS UPON CHANGE IN CONTROL.

         13.7.1    In the event of a Change of Control (as defined below) of 
                   [     *     ] promptly shall notify [     *     ] of such 
                   Change in Control and [     *     ] shall have the right, 
                   for a period of [


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                        *     ] from receipt of such notice, and upon 
                   [     *     ] written notice to [     *     ] (the "Notice 
                   of Intent"), to [          *          ]

         13.7.2    For purposes of this Article 13.7, "Change in Control" shall
                   mean (1) a merger or consolidation in which a Party hereto
                   is not the surviving corporation; (2) a reverse merger in
                   which a Party hereto is the surviving corporation but the
                   shares of such Party's voting stock outstanding immediately
                   preceding the merger are converted by virtue of the merger
                   into other property, whether in the form of securities, cash
                   or otherwise; or (3) if, after giving effect to any
                   agreements among stockholders of a Party hereto, any person
                   holds and may vote in excess of 50% of such Party's voting
                   stock.

         13.7.3    A Change of Control of [     *     ] shall have no effect on
                   this Agreement.

14. ASSIGNMENT.

    14.1 ASSIGNMENT TO AFFILIATES.  Either Party may assign any of its rights
         or obligations under this Agreement in any country to any Affiliates,
         for so long as they remain Affiliates; provided, however, that such
         assignment shall not relieve the assigning Party of its
         responsibilities for performance of its obligations under this
         Agreement.

    14.2 OTHER PERMITTED ASSIGNMENT.  Either Party may assign its rights or
         obligations under this Agreement in connection with a merger or
         similar reorganization or the sale of all or substantially all of its
         assets, subject to provisions of Article 13.7, [          *          ]
         provided, that in the event of such merger, reorganization or sale, 
         [          *          ]  All other assignments by any Party shall 
         [          *          ]

    14.3 BINDING NATURE OF ASSIGNMENT.  This Agreement shall be binding upon
         and inure to the benefit of the successors and permitted assigns of
         the Parties.  Any assignment not in accordance with this Article 14
         shall be void.


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15. INDEMNIFICATION.

    15.1 CROSS INDEMNIFICATION.  

         15.1.     Each Party hereby agrees to save, defend and hold the other
                   Party and its agents and employees harmless from and against
                   any and all suits, claims, actions, demands, liabilities,
                   expenses and/or losses, including reasonable legal expense
                   and attorneys' fees, brought by a Third Party or that arise
                   in connection with any claim brought by a Third Party
                   ("Losses") resulting directly from the manufacture, use,
                   handling, storage, sale or other disposition of Products in
                   the USA to the extent such Losses result solely from (i) the
                   negligence of the indemnifying party or breach by the
                   indemnifying party of any provision of this Agreement, (ii)
                   failure of the indemnifying party to manufacture or have
                   manufactured Products (bulk or finished  form) according to
                   cGMP or Product specifications, or (iii) marketing
                   activities of the indemnifying party contrary to applicable
                   governmental regulations or outside the approved labeling of
                   the Product.

         15.1.2    In the event CoCensys is seeking indemnification under
                   Article 15.1.1, it shall inform Wyeth-Ayerst of a claim as
                   soon as is reasonably practicable after it receives notice
                   of the claim, shall permit Wyeth-Ayerst to assume direction
                   and control of the defense of the claim (including the right
                   to settle the claim solely for monetary consideration), and
                   shall cooperate as requested (at the expense of
                   Wyeth-Ayerst) in the defense of the claim.

         15.1.3    In the event Wyeth-Ayerst is seeking indemnification under   
                   Article 15.1.1, it shall inform CoCensys of a claim as soon
                   as is reasonably practicable after it receives notice of the
                   claim, shall permit CoCensys to assume direction and control
                   of the defense of the claim (including the right to settle
                   the claim solely for monetary consideration), and shall
                   cooperate as requested (at the expense of CoCensys) in the
                   defense of the claim.

    15.2 INSURANCE.  Each Party further agrees to use reasonable commercial
         efforts to obtain and maintain, during the term of this Agreement,
         Comprehensive General Liability Insurance, including Products
         Liability, with reputable and financially secure insurance carriers to
         cover its indemnification obligations under Articles 15.1 and 15.2 or
         self-insurance, with limits of not less than $5,000,000 per occurrence
         and in the aggregate.


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<PAGE>

16. WARRANTIES AND REPRESENTATIONS.

    16.1 GENERAL.  Each Party hereby warrants to the other:

         16.1.1    that it has full power and authority to execute and deliver
                   this Agreement and to perform the obligations on its part
                   hereunder; and

         16.1.2    that the execution and delivery by it of this Agreement and
                   the performance of its obligations hereunder have been duly
                   approved by all necessary corporate action and do not
                   require any shareholder action or approval.

         16.1.3    that to the best of its knowledge, the manufacture, use,     
                   importation, offer for sale or sale of CO 2-6749 will not
                   infringe any Third Party patent in the USA.

    16.2 USC/ROCKEFELLER LICENSE.  Wyeth-Ayerst acknowledges and understands
         that certain technologies sublicensed to Wyeth-Ayerst hereunder were
         licensed to CoCensys under terms of that certain Exclusive License
         Agreement among CoCensys, The University of Southern California and
         the Rockefeller University dated August 28, 1990 (the "USC/Rockefeller
         License"), a copy of which has been provided to Wyeth-Ayerst. 
         CoCensys has received a letter from the University of Southern
         California, dated April 11, 1997, permitting CoCensys to grant to
         Wyeth-Ayerst a sublicense under such license.

17. CONFIDENTIAL INFORMATION.

    17.1 INFORMATION.  Each Party shall keep all information received from the
         other Party (the "Information") confidential and shall not disclose
         nor use the Information without the other Party's written consent
         except to the extent contemplated by this Agreement.  This restriction
         shall not, however, prevent disclosure of the Information if and to
         the extent that disclosure is required by law, PROVIDED THAT the
         disclosing Party informs the other Party without delay of any such
         requirement, in order to allow such other Party to object to such
         disclosure and to seek an appropriate protective order or similar
         protection prior to disclosure.

    17.2 EXCEPTIONS.  The above obligations shall not apply or shall cease to
         apply to Information which:

         17.2.1    is now, or hereafter becomes, through no act or failure to
                   act on the part of the receiving Party, generally known or
                   available;

         17.2.2    is known by the receiving Party at the time of receiving
                   such information, as evidenced by its written records;


                                         33.
<PAGE>

         17.2.3    is hereafter furnished to the receiving Party by a Third
                   Party, as a matter of right and without restriction on
                   disclosure;

         17.2.4    is independently developed by or for the receiving Party
                   without any breach of this Article 17; or

         17.2.5    is the subject of a written permission to disclose provided
                   by the disclosing Party.

    17.3 PERMITTED DISCLOSURES.  Information may be disclosed to employees,
         agents, consultants, sublicensees or suppliers of the recipient Party
         or its Affiliates, but only to the extent required to accomplish the
         purposes of this Agreement and only if the recipient Party obtains
         prior agreement from its employees, agents, consultants, sublicensees
         or suppliers to whom disclosure is to be made to hold in confidence
         and not make use of such information for any purpose other than those
         permitted by this Agreement.  Each Party will use at least the same
         standard of care as it uses to protect proprietary or confidential
         information of its own to ensure that such employees, agents,
         consultants, sublicensees or suppliers do not disclose or make any
         unauthorized use of the Information.

    17.4 DISCLOSURE OF AGREEMENT.  Neither CoCensys nor Wyeth-Ayerst shall
         release to any Third Party or publish in any way any non-public
         information with respect to the terms of this Agreement or concerning
         their cooperation without the prior written consent of the other,
         which consent will not be unreasonably withheld or delayed; provided;
         however that either Party may disclose the terms of this Agreement to
         the extent required to comply with applicable laws, including without
         limitation the rules and regulations promulgated by the Securities and
         Exchange Commission and the Party intending to disclose the terms of
         this Agreement shall provide the nondisclosing party an opportunity to
         review and comment on the intended disclosure which is reasonable
         under the circumstances.  Notwithstanding any other provision of this
         Agreement, each Party may disclose the terms of this Agreement to
         lenders, investment bankers and other financial institutions of its
         choice solely for purposes of financing the business operations of
         such Party either (i) upon the written consent of the other Party or
         (ii) if the disclosing Party uses reasonable efforts to obtain a
         signed confidentiality agreement with such financial institution with
         respect to such information, upon terms substantially similar to those
         contained in this Article 17.

    17.5 PUBLICITY.  Subject to Article 17.4, all publicity, press releases and
         other announcements relating to this Agreement or the transaction
         contemplated hereby shall be reviewed in advance by, and shall be
         subject to the approval of, both Parties.

    17.6 PUBLICATION.  The Parties shall cooperate in appropriate publication
         of the results of research and development work performed pursuant to
         this Agreement, but


                                         34.
<PAGE>

         subject to their predominating interest in obtaining patent protection
         for any patentable subject matter.  The determination of authorship
         for any paper shall be in accordance with accepted scientific
         practice.  Notwithstanding anything in this Article 17.6 to the
         contrary, all publication and presentations of the results of research
         and development work performed pursuant to this Agreement must be
         approved in advance by both Parties.

18. MISCELLANEOUS.

    18.1 NO WAIVER OF CONTRACTUAL RIGHTS.  The failure of either Party to
         require performance by the other Party of any of that other Party's
         obligations hereunder shall in no manner affect the right of such
         Party to enforce the same at a later time.  No waiver by any Party
         hereto of any condition, or of the breach of any provision, term,
         representation or warranty contained in this Agreement, whether by
         conduct or otherwise, in any one or more instances, shall be deemed to
         be or construed as a further or continuing waiver of any such
         condition or breach, or of any other condition or of the breach of any
         other provision, term representation or warranty hereof.

    18.2 EXECUTION AND AMENDMENTS.

         18.2.1    Each Party shall execute and deliver all such instruments
                   and perform all such other acts as the other Party may
                   reasonably request in order to carry out the transactions
                   contemplated by this Agreement.

         18.2.2    This Agreement may not be amended or modified except by
                   written instrument signed by or on behalf of both Parties.

    18.3 SEVERABILITY.  If a court or other tribunal of competent jurisdiction
         should hold any term or provision of this agreement to be excessive,
         or invalid, void or unenforceable, the offending term or provision
         shall be deleted, and, if possible, replaced by a term or provision
         which, so far as practicable achieves the legitimate aims of the
         Parties.

    18.4 RELATIONSHIP BETWEEN THE PARTIES.  Both Parties are independent
         contractors under this Agreement.  Nothing contained in this Agreement
         is intended nor shall be construed so as to constitute CoCensys or
         Wyeth-Ayerst as partners or joint venturers with respect to this
         Agreement.  Neither Party shall have the express or the implied right
         nor authority to assume or create any obligations on behalf of or in
         the name of the other Party, nor to bind the other Party to any other
         contract, agreement or undertaking with any Third Party.

    18.5 CORRESPONDENCE AND NOTICES.


                                         35.
<PAGE>

         18.5.1    Correspondence, reports, documentation, and any other
                   communication in writing between the Parties in the course
                   of ordinary implementation of this Agreement shall be
                   delivered by hand, sent by facsimile, or by airmail to any
                   one member of the JMC appointed by the Party which is to
                   receive such written communication, or any other way as the
                   JMC deems appropriate.

         18.5.2    Extraordinary notices and communications (including but not
                   limited to notices of termination, force majeure, material
                   breach, change of address) shall be in writing and sent by
                   prepaid registered or certified air mail, or by facsimile
                   confirmed by prepaid registered or certified air mail
                   letter, and shall be deemed to have been properly served to
                   the addressee upon receipt of such written communication.

         18.5.3    In the case of CoCensys, the proper address for
                   communications and for all payments shall be:

                   CoCensys, Inc.
                   213 Technology Drive
                   Irvine, California 92618, USA
                   Attn:  Chief Executive Officer

                   and in the case of Wyeth-Ayerst, the proper address for
                   communications and for all payments shall be:

                   Wyeth-Ayerst Laboratories
                   555 Lancaster Avenue
                   St. Davids, PA  19087
                   Attn:  Senior Vice President, Global Business Development

         With a copy to:

                   American Home Products Corporation
                   5 Giralda Farms
                   Madison, NJ  07940
                   Attn:  Senior Vice President and General Counsel

    18.6 CHOICE OF LAW.  This Agreement is subject to and governed by the laws
         of the State of Delaware, excluding its conflict of laws provisions.

    18.7 COUNTERPARTS.  This Agreement may be executed in one or more
         counterparts, each of which shall be an original and all of which
         shall constitute together the same document.


                                         36.
<PAGE>

This Agreement together with its Exhibits and further agreements mentioned
herein and Agreement (No. 2) constitutes the entire agreement of the Parties
with respect to the subject matter hereof as of its date, and supersedes all
prior agreements, understandings, representations and proposals, written or
oral, relating thereto.

AMERICAN HOME PRODUCTS CORPORATION     COCENSYS, INC.



- -------------------------------        -------------------------------
Name                                   Name
Title                                  Title


                                         37.
<PAGE>

                                      EXHIBIT A

                         BACK-UP COMPOUND CANDIDATE CRITERIA
             -----------------------------------------------------------
             -----------------------------------------------------------

              CRITERION FOR IND-TRACKING            ACTIVITIES REQUIRED
             -----------------------------------------------------------
             -----------------------------------------------------------
                               [          *          ]


* Confidential treatment requested

<PAGE>

                                      EXHIBIT B



                               [          *          ]


* Confidential treatment requested

<PAGE>

                                      EXHIBIT C

                                COCENSYS PATENT RIGHTS



US  ISSUE DATE     EXPIRATION DATE     CORRESPONDING FOREIGN APPLICATION
- -------------------------------------------------------------------------

                               [          *          ]


* Confidential treatment requested

<PAGE>

                                      EXHIBIT D


                          DEFINITION OF FULLY BURDENED COST

The following expenses are manufacturing expenses which are prepared in
accordance with generally accepted accounting principles consistently applied.

THE FOLLOWING EXPENSES ARE INCLUDED IN MANUFACTURING COSTS:


                               [          *          ]


* Confidential treatment requested

<PAGE>

                                      EXHIBIT E

                             WYETH-AYERST PATENT RIGHTS


                               [          *          ]


* Confidential treatment requested

<PAGE>

                                      EXHIBIT F

                               STOCK PURCHASE AGREEMENT
<PAGE>

                                 COCENSYS, INC.

                                   -----------


                       PREFERRED STOCK PURCHASE AGREEMENT

                                   -----------


                                  MAY   , 1997

<PAGE>

                                TABLE OF CONTENTS
                                                                        PAGE

1.   PURCHASE AND SALE . . . . . . . . . . . . . . . . . . . . . . .      1
     1.1  Shares.. . . . . . . . . . . . . . . . . . . . . . . . . .      1
     1.2  Closing Date . . . . . . . . . . . . . . . . . . . . . . .      1
     1.3  Delivery . . . . . . . . . . . . . . . . . . . . . . . . .      1

2.   REPRESENTATIONS AND WARRANTIES OF THE COMPANY . . . . . . . . .      1
     2.1  Organization and Standing; Articles and Bylaws . . . . . .      1
     2.2  Authorization. . . . . . . . . . . . . . . . . . . . . . .      1
     2.3  Validity of Shares and Conversion Shares . . . . . . . . .      2
     2.4  Offering . . . . . . . . . . . . . . . . . . . . . . . . .      2
     2.5  Full Disclosure. . . . . . . . . . . . . . . . . . . . . .      2
     2.6  SEC Filings. . . . . . . . . . . . . . . . . . . . . . . .      3
     2.7  Authorized Capital; Outstanding Shares . . . . . . . . . .      3
     2.8  Litigation . . . . . . . . . . . . . . . . . . . . . . . .      3
     2.9  Voting Arrangements. . . . . . . . . . . . . . . . . . . .      3
     2.10 No Conflict; No Violation. . . . . . . . . . . . . . . . .      3
     2.11 Consents and Approvals.. . . . . . . . . . . . . . . . . .      3
     2.12 Absence of Certain Developments. . . . . . . . . . . . . .      4

3.   REPRESENTATIONS AND WARRANTIES OF THE PURCHASER . . . . . . . .      4
     3.1  Legal Power. . . . . . . . . . . . . . . . . . . . . . . .      4
     3.2  Due Execution. . . . . . . . . . . . . . . . . . . . . . .      4
     3.3  Investment Representations . . . . . . . . . . . . . . . .      4

4.   REGISTRATION RIGHTS . . . . . . . . . . . . . . . . . . . . . .      6
     4.1  Definitions. . . . . . . . . . . . . . . . . . . . . . . .      6
     4.2  Registration . . . . . . . . . . . . . . . . . . . . . . .      6
     4.3  Expenses of Registration . . . . . . . . . . . . . . . . .      7
     4.4  Obligations of the Company . . . . . . . . . . . . . . . .      8
     4.5  Indemnification. . . . . . . . . . . . . . . . . . . . . .      9
     4.6  Information by Holder. . . . . . . . . . . . . . . . . . .     11
     4.7  Transfer of Registration Rights. . . . . . . . . . . . . .     11
     4.8  Delay of Registration. . . . . . . . . . . . . . . . . . .     11
     4.9  Rule 144 Reporting.. . . . . . . . . . . . . . . . . . . .     11
     4.10 "Market Stand-Off" Agreement.. . . . . . . . . . . . . . .     12

5.   CONDITIONS TO CLOSING . . . . . . . . . . . . . . . . . . . . .     12
     5.1  Conditions to Obligations of Purchaser . . . . . . . . . .     12
     5.2  Conditions to Obligations of the Company . . . . . . . . .     13

6.   MISCELLANEOUS . . . . . . . . . . . . . . . . . . . . . . . . .     14
     6.1  Governing Law. . . . . . . . . . . . . . . . . . . . . . .     14
     6.2  Survival . . . . . . . . . . . . . . . . . . . . . . . . .     14
     6.3  Successors and Assigns . . . . . . . . . . . . . . . . . .     14


                                        i
<PAGE>

     6.4  Entire Agreement . . . . . . . . . . . . . . . . . . . . .     14
     6.5  Separability . . . . . . . . . . . . . . . . . . . . . . .     14
     6.6  Amendment and Waiver . . . . . . . . . . . . . . . . . . .     14
     6.7  Delays or Omissions. . . . . . . . . . . . . . . . . . . .     15
     6.8  Notices, etc . . . . . . . . . . . . . . . . . . . . . . .     15
     6.9  Finder's Fees. . . . . . . . . . . . . . . . . . . . . . .     16
     6.10 Fees and Expenses. . . . . . . . . . . . . . . . . . . . .     16
     6.11 Information Confidential . . . . . . . . . . . . . . . . .     16
     6.12 Titles and Subtitles . . . . . . . . . . . . . . . . . . .     17
     6.13 Counterparts . . . . . . . . . . . . . . . . . . . . . . .     17


                                       ii
<PAGE>

                                 COCENSYS, INC.

                       PREFERRED STOCK PURCHASE AGREEMENT


     THIS AGREEMENT is made as of May 12, 1997, by and among COCENSYS, INC., a
Delaware corporation (the "Company"), and AMERICAN HOME PRODUCTS CORPORATION, a
Delaware corporation ("Purchaser").

     1.   PURCHASE AND SALE

          1.1  SHARES.  Subject to the terms and conditions hereof, and in
reliance upon the representations, warranties and agreements contained herein,
the Company hereby agrees to issue and sell to Purchaser, and Purchaser hereby
agrees to purchase from the Company, for $5,000,000 (the "Purchase Price"),
100,000 shares (the "Shares") of the Company's Series C Convertible Preferred
Stock (the "Preferred Stock").  The terms of the Preferred Stock are set forth
in the Certificate of Designation annexed hereto as Exhibit A (the "Certificate
of Designation").

          1.2  CLOSING DATE.  The closing of the sale and purchase of the Shares
(the "Closing") shall take place on May 12, 1997 (the "Closing Date").

          1.3  DELIVERY.  At the Closing, the Company will deliver to Purchaser
a certificate or certificates, in such denominations and registered in such
names as Purchaser may designate by notice to the Company, representing the
Shares to be purchased by Purchaser from the Company, dated the Closing Date,
against payment of the Purchase Price by wire transfer, a check made payable to
the order of the Company, or any combination thereof.

     2.   REPRESENTATIONS AND WARRANTIES OF THE COMPANY.

          Except as otherwise specifically disclosed to Purchaser in writing on
the date hereof, the Company hereby represents and warrants to Purchaser as
follows:

          2.1  ORGANIZATION AND STANDING; ARTICLES AND BYLAWS.  The Company is a
corporation duly organized, validly existing and in good standing under the laws
of the State of Delaware, and has full and requisite power and authority to own
and operate its properties and assets and to carry on its business as presently
conducted and as proposed to be conducted.  The Company is duly qualified as a
foreign corporation to do business in each jurisdiction in which the ownership
of its property or the conduct of its business requires such qualification,
except where the failure to so qualify would not materially or adversely affect
the Company, its business, assets, prospects, condition (financial or otherwise)
or operations.

          2.2  AUTHORIZATION.  The Company has all requisite corporate power and
authority to execute and deliver this Agreement and to perform its obligations
hereunder and to issue the Shares as contemplated herein.  All corporate action
on the part of the Company, its


                                        1
<PAGE>

officers, directors and stockholders necessary for the authorization, execution
and delivery of this Agreement, the performance of all the Company's obligations
hereunder, for the authorization, issuance, sale and delivery of the Shares and
for the reservation for issuance of the shares of Common Stock issuable upon
conversion of the Shares (the "Conversion Shares") has been taken or will be
taken prior to the Closing.  This Agreement, when executed and delivered, shall
constitute a valid and legally binding obligation of the Company in accordance
with its terms, subject to laws of general application relating to bankruptcy,
insolvency and the relief of debtors.

          2.3  VALIDITY OF SHARES AND CONVERSION SHARES.  The sale of the Shares
is not and will not be subject to any preemptive rights or rights of first
refusal that have not been waived and, when issued, sold and delivered in
compliance with the provisions of this Agreement and, as applicable, the
Certificate of Designation, the Shares and the Conversion Shares will be validly
issued, fully paid and nonassessable and will be free of any liens, claims or
encumbrances; PROVIDED, HOWEVER, that the Shares and the Conversion Shares will
be subject to restrictions on transfer under state and/or federal securities
laws, and the Shares will be subject to additional restrictions on transfer, in
each case as set forth herein, or as otherwise required by such laws at the time
a transfer is proposed.

          2.4  OFFERING.  Assuming the accuracy of the representations and
warranties of Purchaser contained in Section 3.3 hereof on the date hereof and
on the Closing Date, the offer, issue, and sale of the Shares, and the issuance
of the Conversion Shares (assuming no change in applicable law on each
Conversion Date), are and will be exempt from the registration and prospectus
delivery requirements of the Securities Act of 1933, as amended (the "1933 Act")
and have been or will be registered or qualified (or are or will be exempt from
registration and qualification) under the registration, permit, or qualification
requirements of all applicable state securities laws.

          2.5  FULL DISCLOSURE.

               (a) The Company has furnished to Purchaser the Company's annual
report on Form 10-K for the fiscal year ended December 31, 1996, as amended (the
"1996 10-K") and the Company's Current Report on Form 8-K dated April 29, 1997
(the "8-K") (the "SEC Documents").  The Company warrants that, as of their
respective dates (or if amended, as of the date of such amendment), the SEC
documents complied as to form with the requirements of the Securities Exchange
Act of 1934 (the "1934 Act"), and the information contained in such documents
did not contain any untrue statement of a material fact, and did not omit to
state any material fact necessary to make any statement, in light of the
circumstances under which such statement was made, not misleading.  The Company
further warrants that the 1996 10-K, as modified by the 8-K, does not contain
any untrue statement of a material fact and does not omit to state any material
fact necessary to make the statements therein not misleading as of the date
hereof.

               (b)  The Company has not filed with the Securities and Exchange
Commission (the "SEC") any reports under the 1934 Act since the date of the 8-K.


                                        2
<PAGE>

          2.6  SEC FILINGS.  The Company has timely filed with the SEC all
reports and other documents required to be so filed.  The Company agrees that,
as long as the Development and Commercialization Agreement between the Company
and Wyeth-Ayerst Laboratories, dated as of May 12, 1997, is in effect, it will,
upon the Purchaser's written request, promptly furnish to Purchaser all SEC
filings and any annual and quarterly reports furnished to the Company's
stockholders.

          2.7  AUTHORIZED CAPITAL; OUTSTANDING SHARES.  The Company is
authorized to issue 75,000,000 shares of Common Stock and 5,000,000 shares of
Preferred Stock.  As of March 31, 1997, there were 22,516,863 shares of Common
Stock and 100,000 shares of Preferred Stock outstanding.  No shares of capital
stock, or securities convertible into or exercisable for capital stock or other
rights affecting the capital stock, have been issued since such date except for
issuances pursuant to the Company's equity compensation plans or pursuant to
outstanding options, warrants or rights, in each case as described in the 1996
10-K.  All outstanding shares of Common Stock have been duly authorized and
validly issued and are fully paid and non-assessable; and none of the
outstanding shares of Common Stock were issued in violation of the preemptive
rights, if any, of any stockholders of the Company.

          2.8  LITIGATION.  There is no action, suit or proceeding pending, or,
to the Company's knowledge, threatened, against the Company (a) which questions
the validity of this Agreement or the ability of the Company to consummate the
transactions contemplated hereby or (b) which, singly or in the aggregate, if
the subject of unfavorable decision, ruling or finding, would materially
adversely affect the business, properties, prospects, operations, or financial
condition of the Company, in each case as described in the 1996 10-K.

          2.9  VOTING ARRANGEMENTS.  To the best of the Company's knowledge,
there are no outstanding stockholder agreements, voting trusts, proxies or other
arrangements or understandings among the stockholders of the Company relating to
the voting of their respective shares.

          2.10 NO CONFLICT; NO VIOLATION.  The execution, delivery and
performance of this Agreement and consummation of the transactions contemplated
hereby will not (a) violate or conflict with any provisions of the Amended and
Restated Certificate of Incorporation, as amended, or Bylaws of the Company; (b)
result in any breach, conflict with, violation of or default or loss of a
benefit under, or permit the acceleration of any obligation under (in each case,
upon the giving of notice, the passage of time, or both) any mortgage,
indenture, lease, loan agreement or other agreement or instrument, permit,
franchise, license, judgment, order, decree, law, ordinance, rule or regulation
applicable to the Company or its properties.

          2.11 CONSENTS AND APPROVALS.  All consents, approvals, orders, or
authorizations of, or registrations, qualifications, designations, declarations,
or filings with, any federal, state or local governmental authority, required on
the part of the Company in connection with the valid execution, delivery and
performance of this Agreement, the offer, sale or issuance of the Shares, or the
consummation of any other transaction contemplated hereby have been obtained, or
will be effective at the Closing, except for notices required or permitted to be
filed


                                        3
<PAGE>

with certain state and federal securities commissions after the Closing, which
notices will be filed on a timely basis.

          2.12 ABSENCE OF CERTAIN DEVELOPMENTS.  Except as disclosed in or
contemplated by the SEC Documents, since December 31, 1996, the Company has not
(a) incurred or become subject to any material liabilities (absolute or
contingent) except current liabilities incurred, and liabilities under contracts
entered into, in the ordinary course of business, consistent with past
practices; (b) mortgaged, pledged or subjected to lien, charge or any other
encumbrance any of its assets, tangible or intangible; (c) sold, assigned or
transferred any of its assets or canceled any debts or obligations except in the
ordinary course of business, consistent with past practices; (d) suffered any
extraordinary losses, or waived any rights of substantial value; (e) sold,
assigned or transferred to a third party that is not an affiliate (within the
meaning set forth in Rule 405 under the Securities Act of 1933, as amended) any
material patents, trademarks, copyrights, trade secrets or other intangible
assets for compensation less than the fair value of such assets; (f) declared,
paid or otherwise made any dividend or distribution of any kind on its capital
stock; (g) entered into any material transaction other than in the ordinary
course of business, consistent with past practices; or (h) otherwise had any
material change in its condition, financial or otherwise, except for changes in
the ordinary course of business, consistent with past practices, none of which
individually or in the aggregate has been materially adverse.

          2.13 NASDAQ NATIONAL MARKET DESIGNATION.  The Common Stock of the
Company is listed on the Nasdaq National Market and the Company knows of no
reason or set of facts which is likely to result in the delisting of the Common
Stock by the Nasdaq National Market or the inability of such stock to continue
to be included in the Nasdaq National Market.

     3.   REPRESENTATIONS AND WARRANTIES OF THE PURCHASER.

          Purchaser hereby represents and warrants to the Company as follows:

          3.1  LEGAL POWER.  It has the requisite legal power to enter into this
Agreement, to purchase the Shares hereunder, and to carry out and perform its
obligations under the terms of this Agreement.

          3.2  DUE EXECUTION.  This Agreement has been duly authorized, executed
and delivered by it, and, upon due execution and delivery by the Company, this
Agreement will be a valid and binding agreement of it in accordance with its
terms, subject to laws of general application relating to bankruptcy, insolvency
and the relief of debtors.

          3.3  INVESTMENT REPRESENTATIONS.

               (a)  It is acquiring the Shares, and intends to acquire the
Conversion Shares, for its own account, not as nominee or agent, for investment
and not with a view to, or for resale in connection with, any distribution or
public offering thereof within the meaning of the 1933 Act.


                                        4
<PAGE>

               (b)  It understands and agrees that  the Shares have not been
and, when issued, the Conversion Shares will not be, registered under the 1933
Act by reason of a specific exemption therefrom, that they must be held by it
indefinitely, and that it must, therefore, bear the economic risk of such
investment indefinitely, unless a subsequent disposition thereof is registered
under the 1933 Act or is exempt from such registration;  each certificate
representing the Shares and the Conversion Shares will be endorsed with the
following legend:

          THE SECURITIES EVIDENCED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
     UNDER THE 1933 ACT, AND MAY NOT BE SOLD, TRANSFERRED, ASSIGNED OR
     HYPOTHECATED UNLESS (A) PURSUANT TO RULE 144 UNDER THE 1933 ACT OR (B)
     THERE IS AN EFFECTIVE REGISTRATION STATEMENT UNDER THE 1933 ACT COVERING
     SUCH SECURITIES OR (C) THE COMPANY RECEIVES AN OPINION OF COUNSEL FOR THE
     HOLDER OF THESE SECURITIES REASONABLY SATISFACTORY TO THE COMPANY, STATING
     THAT SUCH SALE, TRANSFER, ASSIGNMENT OR HYPOTHECATION IS EXEMPT FROM THE
     REGISTRATION AND PROSPECTUS DELIVERY REQUIREMENTS OF THE 1933 ACT;

(iii) each certificate representing the Shares also will be endorsed with the
following legend:

          THE SECURITIES EVIDENCED BY THIS CERTIFICATE MAY NOT BE SOLD,
     TRANSFERRED, ASSIGNED OR HYPOTHECATED UNLESS (A) THE TRANSFEREE IS AN
     AFFILIATE OF THE HOLDER WITHIN THE MEANING OF RULE 144 UNDER THE 1933 ACT
     OR (B) ALL SUCH SECURITIES ARE TRANSFERRED TO A SINGLE INDIVIDUAL OR
     ENTITY;

and  the Company will instruct any transfer agent not to register the transfer
of any of the Shares unless the conditions specified in the foregoing legends
are satisfied, PROVIDED HOWEVER, that to the extent the legend set forth in
clause (b)(ii) above is no longer required, the Company shall cause its transfer
agent to issue a new certificate or certificates free of such legend.

               (c)  It has been furnished with such materials and has been given
access to such information relating to the Company as it or its qualified
representative has requested and it has been afforded the opportunity to ask
questions regarding the Company and the Shares, all as it has found necessary to
make an informed investment decision.

               (d)  It is an "accredited investor" within the meaning of
Regulation D under the 1933 Act.

               (e)  It was not formed for the specific purpose of acquiring the
Shares or the Conversion Shares.


                                        5
<PAGE>

     4.   REGISTRATION RIGHTS.

          The Company hereby grants to Purchaser the registration rights set
forth in this Section 4, with respect to the Registrable Securities (as
hereinafter defined) owned by Purchaser.

          4.1  DEFINITIONS.  As used in this Section 4:

               (a)  The term "Holder" or "Holders" shall mean (i) Purchaser and
(ii) any other person holding or having the right to acquire Registrable
Securities to whom these registration rights have been transferred pursuant to
Subsection 4.7 hereof.

               (b)  The terms "register," "registered," and "registration" refer
to a registration effected by filing with the SEC a registration statement (the
"Registration Statement") in compliance with the 1933 Act and the declaration or
ordering by the SEC of the effectiveness of such Registration Statement.

               (c)  The term "Registrable Securities" means (i) the shares of
Common Stock of the Company issued upon conversion of the Shares (the
"Conversion Shares") in accordance with the Certificate of Designation and such
other shares of Common Stock of the Company held by Purchaser from time to time
and (ii) any Common Stock of the Company issued as (or issuable upon the
conversion or exercise of any warrant, right, or other security that is issued
as) a dividend or other distribution with respect to, or in exchange or in
replacement of, the shares referred to in clause (i) of this subsection (c);
PROVIDED, HOWEVER, that Registrable Securities shall cease to be Registrable
Securities upon the expiration of the Market Stand-Off Agreement set forth in
Section 4.10 hereof.  In the event of any recapitalization by the Company,
whether by stock split, reverse stock split, stock dividend or the like, the
number of shares of Registrable Securities shall be proportionately increased or
decreased.

          4.2  REGISTRATION.


               (a)  REGISTRATION.  If at any time or from time to time the
Company shall determine to register any of its securities for its own account
(other than a registration relating solely to employee benefit plans or a
registration on Form S-4 relating solely to an SEC Rule 145 transaction) or for
the account of security holders pursuant to demand registration rights, the
Company will:

                    (i)  promptly give to each Holder written notice thereof
(which shall include a list of the jurisdictions in which the Company intends to
attempt to qualify such securities under the applicable blue sky or other state
securities laws); and

                    (ii) include in such registration (and any related
qualification under blue sky laws or other compliance), and in any underwriting
involved therein, all the Registrable Securities specified in a written request
or requests, made within 20 calendar days


                                        6
<PAGE>

after receipt of such written notice from the Company, by any Holder or Holders,
except as set forth in Subsection 4.2(b) below.

               (b)  UNDERWRITING.  If the registration of which the Company
gives notice is for a registered public offering involving an underwriting, the
Company shall so advise the Holders as a part of the written notice given
pursuant to Subsection 4.2(a)(i).  In such event the right of any Holder to
registration pursuant to this Section 4 shall be conditioned upon such Holder's
participation in such underwriting and the inclusion of such Holder's
Registrable Securities in the underwriting to the extent provided herein.  All
Holders proposing to distribute their securities through such underwriting
shall, together with the Company and any other parties distributing their
securities through such underwriting, enter into an underwriting agreement in
customary form with the underwriter or underwriters selected for such
underwriting by the Company.  Notwithstanding any other provision of this
Subsection 4.2, if the underwriter determines that marketing factors require a
limitation of the number of shares to be underwritten, the underwriter may limit
the number of Registrable Securities to be included in the registration and
underwriting, or may exclude Registrable Securities entirely from such
registration and underwriting subject to the terms of this paragraph.  The
Company shall so advise all holders of the Company's securities that would
otherwise be registered and underwritten pursuant hereto, and the number of
shares of such securities, including Registrable Securities, that may be
included in the registration and underwriting shall be allocated in the
following manner:  shares, other than Registrable Securities and other
securities carrying registration rights, requested to be included in such
registration by stockholders shall be excluded and if a limitation on the number
of shares is still required, the number of securities that may be included shall
be allocated among the Holders and holders of securities having PARI PASSU
registration rights, if any, in proportion, as nearly as possible, to the
respective amounts of such securities held by each such holder, in each case at
the time of filing the Registration Statement.  In the event of any underwriter
cutback, if any selling stockholder which is a Holder of Registrable Securities
is a partnership or corporation, the partners, retired partners and stockholders
of such Holder, or the estates and family members of any such partners and
retired partners and any trusts for the benefit of any of the foregoing persons
shall be deemed to be a single "selling Holder", and any pro rata reduction with
respect to such "selling Holder" shall be based upon the aggregate amount of
shares carrying registration rights owned by all entities and individuals
included in such "selling Holder", as defined in this sentence.  No securities
excluded from the underwriting by reason of the underwriter's marketing
limitation shall be included in such registration.  If any Holder disapproves of
the terms of the underwriting, it may elect to withdraw therefrom by written
notice to the Company and the underwriter.  The Registrable Securities so
withdrawn shall also be withdrawn from registration.

          4.3  EXPENSES OF REGISTRATION.  All expenses incurred in connection
with a registration effected pursuant to Subsection 4.2, including without
limitation all registration, filing, and qualification fees (including blue sky
fees and expenses), printing expenses, escrow fees, fees and disbursements of
counsel for the Company and, if there are more than two (2) participating
Holders, of one special counsel for the participating Holders, and expenses of
any special audits incidental to or required by such registration (collectively,
"Registration Expenses"), shall be borne by the Company; provided, however, that
the term Registration


                                        7
<PAGE>

Expenses shall not include, and in no event will the Company be obligated to
pay, stock transfer taxes or underwriters' discounts or commissions relating to
Registrable Securities.

          4.4  OBLIGATIONS OF THE COMPANY.  Whenever required under Section 4.2
to effect the registration of any Registrable Securities, the Company shall, as
expeditiously as reasonably possible:

               (a)  Prepare and file with the SEC a registration statement with
respect to such Registrable Securities and use its best efforts to cause such
registration statement to become effective, and, upon the request of the Holders
of a majority of the Registrable Securities registered thereunder, keep such
registration statement effective until the earlier of (i) one hundred eighty
(180) days or (ii) until the Holder or Holders have completed the distribution
relating thereto; PROVIDED HOWEVER, that the Company may delay the filing of
such registration statement for up to 60 days following such request by giving
notice to Purchaser if the Company shall have determined that the Company may be
required to disclose any material corporate development which disclosure may
have a material effect on the Company.  Following the effectiveness of a
registration statement filed pursuant to Rule 415 under the 1933 Act, the
Company may, at any time, but not more than once in any six-month period,
suspend the effectiveness of such registration statement for up to 60 days, as
appropriate (a "Suspension Period"), by giving notice to Purchaser, if the
Company shall have determined that the Company may be required to disclose any
material corporate development which disclosure may have a material effect on
the Company.  The duration of any Suspension Period shall be added to the period
of time the Company agrees to keep the registration statement effective.
Purchaser agrees that, upon receipt of any notice from the Company of a
Suspension Period, Purchaser shall forthwith discontinue disposition of shares
covered by such registration statement or prospectus until Purchaser (i) is
advised in writing by the Company that the use of the applicable  prospectus may
be resumed, (ii) has received copies of a supplemental or amended prospectus, if
applicable, and (iii) has received copies of any additional or supplemental
filings which are incorporated or deemed to be incorporated by reference in such
prospectus.

               (b)  Prepare and file with the SEC such amendments and
supplements to such registration statement and the prospectus used in connection
with such registration statement as may be necessary to comply with the
provisions of the 1933 Act with respect to the disposition of all securities
covered by such registration statement.

               (c)  Furnish to the Holders such numbers of copies of a
prospectus, including a preliminary prospectus, in conformity with the
requirements of the 1933 Act, and such other documents as they may reasonably
request in order to facilitate the disposition of Registrable Securities owned
by them.

               (d)  Use its best efforts to register and qualify the securities
covered by such registration statement under such other securities or Blue Sky
laws of such jurisdictions as shall be reasonably requested by the Holders,
provided that the Company shall not be required in connection therewith or as a
condition thereto to qualify to do business or to file a general consent to
service of process in any such states or jurisdictions.


                                        8
<PAGE>

               (e)  In the event of any underwritten public offering, enter into
and perform its obligations under an underwriting agreement, in usual and
customary form, with the managing underwriter of such offering and, if requested
by such underwriter, cause appropriate officers to participate in a "road show"
to market such offering.  Each Holder participating in such underwriting shall
also enter into and perform its obligations under such an agreement.

               (f)  Notify each Holder of Registrable Securities covered by such
registration statement, at any time when a prospectus relating thereto is
required to be delivered under the 1933 Act, of the happening of any event as a
result of which the prospectus included in such registration statement, as then
in effect, includes an untrue statement of a material fact or omits to state a
material fact required to be stated therein or necessary to make the statements
therein not misleading in the light of the circumstances then existing.

               (g)  Furnish, at the request of any Holder requesting
registration of Registrable Securities pursuant to this Section 4, on the date
that such Registrable Securities are delivered to the underwriters for sale in
connection with a registration pursuant to this Section 4, if such securities
are being sold through underwriters, on the date that the registration statement
with respect to such securities becomes effective, (i) an opinion, dated such
date, of the counsel representing the Company for the purposes of such
registration, in form and substance as is customarily given to underwriters in
an underwritten public offering, addressed to the underwriters, if any, and to
the Holders requesting registration of Registrable Securities and (ii) a letter
dated such date, from the independent accountants of the Company, in form and
substance as is customarily given by independent accountants to underwriters in
an underwritten public offering, addressed to the underwriters, if any, and to
the Holders requesting registration of Registrable Securities.

          4.5  INDEMNIFICATION.

               (a)  The Company will, and does hereby undertake to, indemnify
and hold harmless each Holder of Registrable Securities, each of such Holder's
officers, directors, partners and agents, and each person controlling such
Holder, with respect to any registration, qualification, or compliance effected
pursuant to this Section 4, and each underwriter, if any, and each person who
controls any underwriter, of the Registrable Securities held by or issuable to
such Holder, against all claims, losses, damages, and liabilities (or actions in
respect thereto) to which they may become subject under the 1933 Act, the 1934
Act, or other applicable law arising out of or based on (i) any untrue statement
(or alleged untrue statement) of a material fact contained in any prospectus,
offering circular, or other similar document (including any related Registration
Statement, notification, or the like) incident to any such registration,
qualification, or compliance, or based on any omission (or alleged omission) to
state therein a material fact required to be stated therein or necessary to make
the statements therein not misleading, or (ii) any violation or alleged
violation by the Company of any law, rule or regulation applicable to the
Company in connection with any such registration, qualification, or compliance,
and will reimburse, as incurred, each such Holder, each such underwriter, and
each such director, officer, partner, agent and controlling person, for any
legal and any other expenses reasonably incurred in connection with
investigating or defending any such claim, loss,


                                        9
<PAGE>

damage, liability, or action; provided that the Company will not be liable in
any such case to the extent that any such claim, loss, damage, liability or
expense, arises out of or is based on any untrue statement or omission based
upon written information furnished to the Company by an instrument duly executed
by such Holder or underwriter and stated to be specifically for use therein.

               (b)  Each Holder will, if Registrable Securities held by or
issuable to such Holder are included in such registration, qualification, or
compliance, indemnify the Company, each of its directors, and each officer who
signs a Registration Statement in connection therewith, and each person
controlling the Company, each underwriter, if any, and each person who controls
any underwriter, of the Company's securities covered by such a Registration
Statement, and each other Holder, each of such other Holder's officers,
partners, directors and agents and each person controlling such other Holder,
against all claims, losses, damages, and liabilities (or actions in respect
thereof) arising out of or based on any untrue statement (or alleged untrue
statement) of a material fact contained in any such Registration Statement,
prospectus, offering circular, or other document, or any omission (or alleged
omission) to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, and will reimburse, as
incurred, the Company, each such underwriter, each such other Holder, and each
such director, officer, partner, and controlling person, for any legal or any
other expenses reasonably incurred in connection with investigating or defending
any such claim, loss, damage, liability, or action, in each case to the extent,
but only to the extent, that such untrue statement (or alleged untrue statement)
or omission (or alleged omission) was made in such Registration Statement,
prospectus, offering circular, or other document, in reliance upon and in
conformity with written information furnished to the Company by an instrument
duly executed by such Holder and stated to be specifically for use therein.  In
no event will any Holder be required to enter into any agreement or undertaking
in connection with any registration under this Section 4 providing for any
indemnification or contribution obligations on the part of such Holder greater
than such Holder's obligations under this Subsection 4.5.  The liability of each
Holder for indemnification under this Section 4.5 shall not exceed the proceeds
to such Holder from the sale of Registrable Securities.

               (c)  Each party entitled to indemnification under this
Subsection 4.5 (the "Indemnified Party") shall give notice to the party required
to provide such indemnification (the "Indemnifying Party") of any claim as to
which indemnification may be sought promptly after such Indemnified Party has
actual knowledge thereof, and shall permit the Indemnifying Party to assume the
defense of any such claim or any litigation resulting therefrom; provided that
counsel for the Indemnifying Party, who shall conduct the defense of such claim
or litigation, shall be subject to approval by the Indemnified Party (whose
approval shall not be reasonably withheld) and the Indemnified Party may
participate in such defense at the Indemnifying Party's expense if
representation of such Indemnified Party would be inappropriate due to actual or
potential differing interests between such indemnified party and any other party
represented by such counsel in such proceeding; and provided further that the
failure of any Indemnified Party to give notice as provided herein shall not
relieve the Indemnifying Party of its obligations under this Section 4, except
to the extent that such failure to give notice shall materially adversely affect
the Indemnifying Party in the defense of any such claim or any such litigation.
No


                                       10
<PAGE>

Indemnifying Party, in the defense of any such claim or litigation, shall,
except with the consent of each Indemnified Party, consent to entry of any
judgment or enter into any settlement that does not include as an unconditional
term thereof the giving by the claimant or plaintiff therein, to such
Indemnified Party, of a release from all liability in respect to such claim or
litigation.

          4.6  INFORMATION BY HOLDER.  The Holder or Holders of Registrable
Securities included in any registration shall furnish to the Company such
information regarding such Holder or Holders and the distribution proposed by
such Holder or Holders as the Company may reasonably request in writing and as
shall be required in connection with any registration, qualification, or
compliance referred to in this Section 4.

          4.7  TRANSFER OF REGISTRATION RIGHTS.  The rights contained in this
Section 4 to cause the Company to register the Registrable Securities, may be
assigned or otherwise conveyed to any affiliate (as such term is defined in Rule
405 under the 1933 Act) of Purchaser who is a transferee or assignee of Shares
or Registrable Securities, or to a third party acquiring all of the Registrable
Securities, each of whom shall be considered a "Holder" for purposes of this
Section 4, provided that the Company is given written notice by Purchaser, at
the time of or within a reasonable time after said transfer, stating the name
and address of said transferee or assignee and identifying the securities with
respect to which such registration rights are being assigned, and provided that
any such transferee agrees in writing to be bound by the provisions of this
Section 4.

          4.8  DELAY OF REGISTRATION.  No Holder shall have any right to obtain
or seek an injunction restraining or otherwise delaying any such registration as
the result of any controversy that might arise with respect to the
interpretation or implementation of this Section 4.

          4.9  RULE 144 REPORTING.  With a view to making available to the
Holders the benefits of certain rules and regulations of the SEC which may
permit the sale of the Registrable Securities to the public without
registration, the Company agrees to use its best efforts to:

               (a)  Make and keep public information available, in accordance
with subsection (c) of Rule 144 under the 1933 Act ("Rule 144") or any similar
or analogous rule promulgated under the 1933 Act, as long as Registrable
Securities are outstanding;

               (b)  File with the SEC, in a timely manner, all reports and other
documents required of the Company under the 1933 Act and 1934 Act;

               (c)  So long as a Holder owns any Registrable Securities, furnish
to such Holder forthwith upon request: a written statement by the Company as to
its compliance with the reporting requirements of Rule 144 and of the 1934 Act;
a copy of the most recent annual or quarterly report of the Company; and such
other reports and documents as a Holder may reasonably request in availing
itself of any rule or regulation of the SEC allowing it to sell any such
securities without registration.


                                       11
<PAGE>

               (d)  Take all such action (including without limitation the
furnishing of the information described in Rule 144(d)(4)) as may be necessary
or helpful to facilitate a sale of Registrable Securities by a Holder to a
"qualified institutional buyer," as such term is defined in Rule 144A of the
1933 Act.

          4.10 "MARKET STAND-OFF" AGREEMENT.  Purchaser hereby agrees that,
except for Registrable Securities being sold pursuant to this Section 4, during
the ninety (90)-day period following the effective date of a registration
statement of the Company filed under the 1933 Act, it shall not, to the extent
requested by the Company or any underwriter, sell or otherwise transfer or
dispose of any Common Stock of the Company held by it at any time during such
period; PROVIDED, HOWEVER, that:

               (a)  Such agreement shall be applicable only to registration
statements (other than on Form S-8) of the Company which cover Common Stock (or
other securities) to be sold on its behalf to the public;

               (b)  Such Agreement shall be applicable only if Purchaser holds
at least one percent (1%) of the Common Stock of the Company then outstanding;
and

               (c)  All executive officers and directors of the Company, and all
other corporate partners of the Company similarly situated, enter into similar
agreements.

     The Company may impose stop-transfer instructions with respect to
securities subject to the foregoing restriction until the end of such period.
The agreement of the Purchaser set forth in this Section 4.10 shall lapse five
(5) years after the Closing Date provided that Purchaser is not at such time an
affiliate of the Company (as defined in Rule 405 under the 1933 Act), in which
case such restrictions shall lapse at such time as Purchaser ceases to be an
affiliate.

     5.   CONDITIONS TO CLOSING.

          5.1  CONDITIONS TO OBLIGATIONS OF PURCHASER.  Purchaser's obligation
to purchase the Shares at the Closing is subject to the fulfillment, at or prior
to the Closing, of all of the following conditions, any of which may be waived
by Purchaser:

               (a)  REPRESENTATIONS AND WARRANTIES TRUE; PERFORMANCE OF
OBLIGATIONS.  The representations and warranties made by the Company in
Section 2 hereof, to the extent qualified as to materiality, shall be true and
correct in all respects and, to the extent not so qualified, shall be true and
correct in all material respects on the date of the Closing with the same force
and effect as if they had been made on and as of said date; the business and
assets of the Company shall not have been adversely affected in any material way
prior to the Closing; and the Company shall have performed and complied with all
obligations, agreements and conditions herein required to be performed by it on
or prior to the Closing.


                                       12
<PAGE>

               (b)  OPINION OF THE COMPANY'S COUNSEL.  Purchaser shall have
received from Cooley Godward LLP, counsel to the Company, an opinion letter
substantially in the form attached hereto as Exhibit B, addressed to it, dated
the date of the Closing.

               (c)  PROCEEDINGS AND DOCUMENTS.  All corporate and other
proceedings in connection with the transactions contemplated at the Closing
hereby and all documents and instruments incident to such transactions shall be
reasonably satisfactory in substance and form to Purchaser, and Purchaser shall
have received all such counterpart originals or certified or other copies of
such documents as they may reasonably request.

               (d)  QUALIFICATIONS, LEGAL INVESTMENT.  All authorizations,
approvals, or permits, if any, of any governmental authority or regulatory body
of the United States or of any state that are required in connection with the
lawful sale and issuance of the Shares pursuant to this Agreement shall have
been duly obtained and shall be effective on and as of the Closing.  No stop
order or other order enjoining the sale of the Shares shall have been issued and
no proceedings for such purpose shall be pending or, to the knowledge of the
Company, threatened by the SEC or any commissioner of corporations or similar
officer of any other state having jurisdiction over this transaction.  At the
time of the Closing, the sale and issuance of the Shares shall be legally
permitted by all laws and regulations to which Purchaser and the Company are
subject.

               (e)  COMPLIANCE CERTIFICATE.  The Company shall have delivered to
Purchaser a Certificate, executed by the President of the Company, dated the
Closing Date, certifying to (i) the fulfillment of the conditions specified in
subparagraphs (a) and (d) of this Subsection 5.1. and (ii) the incumbency of the
officers of the Company executing this Agreement and the other instruments
delivered by the Purchaser upon the Closing.

          5.2  CONDITIONS TO OBLIGATIONS OF THE COMPANY.  The Company's
obligation to issue and sell the Shares at the Closing is subject to the
fulfillment, on or prior to the Closing, of the following conditions, any of
which may be waived by the Company:

               (a)  REPRESENTATIONS AND WARRANTIES TRUE.  The representations
and warranties made by Purchaser in Section 3 hereof shall be true and correct
at the date of the Closing, with the same force and effect as if they had been
made on and as of said date.

               (b)  PERFORMANCE OF OBLIGATIONS.  Purchaser shall have performed
and complied with all obligations, agreements and conditions herein required to
be performed or complied with by it on or before the Closing.

               (c)  QUALIFICATIONS, LEGAL INVESTMENT.  All authorizations,
approvals, or permits, if any, of any governmental authority or regulatory body
of the United States or of any state that are required in connection with the
lawful sale and issuance of the Shares pursuant to this Agreement shall have
been duly obtained and shall be effective on and as of the Closing.  No stop
order or other order enjoining the sale of the Shares shall have been issued and
no proceedings for such purpose shall be pending or, to the knowledge of the
Company, threatened


                                       13
<PAGE>

by the SEC or any commissioner of corporations or similar officer of any state
having jurisdiction over this transaction.  At the time of the Closing, the sale
and issuance of the Shares shall be legally permitted by all laws and
regulations to which Purchaser and the Company are subject.

     6.   MISCELLANEOUS.

          6.1  GOVERNING LAW.  This Agreement shall be governed by and construed
under the laws of the State of Delaware, without regard to the principles
regarding conflicts of laws of such State.

          6.2  SURVIVAL.  The representations, warranties, covenants, and
agreements made herein shall survive any investigation made by Purchaser and the
closing of the transactions contemplated hereby.  All statements as to factual
matters contained in any certificate or other instrument delivered by or on
behalf of the Company pursuant hereto or in connection with the transactions
contemplated hereby shall be deemed to be representations and warranties by the
Company hereunder as of the date of such certificate or instrument.

          6.3  SUCCESSORS AND ASSIGNS.  Except as otherwise expressly provided
herein, the provisions hereof shall inure to the benefit of, and be binding
upon, the successors, assigns, heirs, executors, and administrators of the
parties hereto (including any permitted transferee of the Shares).

          6.4  ENTIRE AGREEMENT.  This Agreement, the Exhibits hereto, and the
other documents delivered pursuant hereto constitute the full and entire
understanding and agreement among the parties with regard to the subjects hereof
and no party shall be liable or bound to any other party in any manner by any
representations, warranties, covenants, or agreements except as specifically set
forth herein or therein.  Nothing in this Agreement, express or implied, is
intended to confer upon any party, other than the parties hereto and their
respective successors and assigns, any rights, remedies, obligations, or
liabilities under or by reason of this Agreement, except as expressly provided
herein.

          6.5  SEPARABILITY.  In case any provision of this Agreement shall be
invalid, illegal, or unenforceable, it shall to the extent practicable, be
modified so as to make it valid, legal and enforceable and to retain as nearly
as practicable the intent of the parties, and the validity, legality, and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

          6.6  AMENDMENT AND WAIVER.  Any term of this Agreement may be amended
and the observance of any term of this Agreement may be waived (either generally
or in a particular instance, either retroactively or prospectively, and either
for a specified period of time or indefinitely), with the written consent of the
Company and the holders of not less than a majority-in-interest of the aggregate
of outstanding Shares.  Any amendment or waiver effected in accordance with this
paragraph shall be binding upon Purchaser, each future holder of the Shares, and
the Company.  Upon the effectuation of each such amendment or waiver, the


                                       14
<PAGE>

Company shall promptly give written notice thereof to the record holders of the
Shares who have not previously consented thereto in writing, if any.

          6.7  DELAYS OR OMISSIONS.  No delay or omission to exercise any right,
power, or remedy accruing to Purchaser or any subsequent holder of any Shares
upon any breach, default or noncompliance of the Company under this Agreement,
shall impair any such right, power, or remedy, nor shall it be construed to be a
waiver of any such breach, default or noncompliance, or any acquiescence
therein, or of any similar breach, default or noncompliance thereafter
occurring.  It is further agreed that any waiver, permit, consent, or approval
of any kind or character on Purchaser's part of any breach, default or
noncompliance under this Agreement or any waiver on Purchaser's part of any
provisions or conditions of this Agreement must be in writing and shall be
effective only to the extent specifically set forth in such writing, and that
all remedies, either under this Agreement, by law, or otherwise afforded to
Purchaser, shall be cumulative and not alternative.

          6.8  NOTICES, ETC.  All notices and other communications required or
permitted hereunder shall be in writing and shall be deemed effectively given
(a) upon personal delivery, (b) on the first business day after receipted
delivery to a courier service which guarantees next business-day delivery, under
circumstances in which such guaranty is applicable, or (c) on the earlier of
delivery or five (5) business days after mailing by United States certified by
mail, postage and fees prepaid, to the appropriate party at the address set
forth below or to such other address as the part so notifies the other in
writing:

               (a)  if to the Company, to:

                    COCENSYS, INC.
                    213 Technology Drive
                    Irvine, CA 92718
                    Attention:  President and Chief Executive Officer
                    Fax:(714) 753-6141

                    with a copy to:

                    COOLEY GODWARD LLP
                    5 Palo Alto Square
                    3000 El Camino Real
                    Palo Alto, CA 94306-2155
                    Attention:  Alan C. Mendelson, Esq.
                    Fax:(415) 857-0663


                                       15
<PAGE>

                    if to Purchaser, to:

                    AMERICAN HOME PRODUCTS CORPORATION
                    5 Giralda Farms
                    Madison, NJ  07940
                    Attention: Senior Vice President and General Counsel

          Notwithstanding the foregoing, all notices and other communications to
an address outside of the United States shall be sent by telecopy and confirmed
in writing to be sent by first class mail.

          6.9  FINDER'S FEES.

               (a)  The Company  represents and warrants that it has retained no
finder or broker in connection with the transactions contemplated by this
Agreement and  hereby agrees to indemnify and to hold harmless of and from any
liability for any commission or compensation in the nature of a finder's fee to
any broker or other person or firm (and the costs and expenses of defending
against such liability or asserted liability) for which the Company or any of
its employees or representatives is responsible.

               (b)  Purchaser  represents and warrants that it has retained no
finder or broker in connection with the transactions contemplated by this
Agreement, and  hereby agrees to indemnify and to hold the Company harmless of
and from any liability for any commission or compensation in the nature of a
finder's fee to any broker or other person or firm (and the costs and expenses
of defending against such liability or asserted liability) for which Purchaser
or any of its employees or representatives are responsible.

          6.10 FEES AND EXPENSES.  Each party agrees to pay all its own
fees, costs and expenses, including legal and accounting fees, relating to the
negotiation, execution, delivery and performance this Agreement and the
transactions contemplated hereby.  If legal action is brought by, or on behalf
of, Purchaser to enforce or interpret this Agreement, the prevailing party shall
be entitled to recover its attorneys' fees and legal costs in connection
therewith.

               6.11 INFORMATION CONFIDENTIAL.  Purchaser acknowledges that
certain information received by it pursuant hereto is confidential and for
Purchaser's use only, and it will refrain from using such information or
reproducing, disclosing, or disseminating such information to any other person
(other than its employees, affiliates, agents, or partners having a need to know
the contents of such information and its attorneys, in each case who agree to be
bound by this Section 6.11), except in connection with the exercise of rights
under this Agreement, unless such information (i) is or becomes, through no
fault of Purchaser, available to the public generally; (ii) was already known by
Purchaser, as demonstrated by competent evidence, at the time of its receipt
from the Company; (iii) is obtained by Purchaser from a third party legally free
to disclose such information; or (iv) Purchaser is required by a governmental
body or court of competent jurisdiction to disclose such information.


                                       16
<PAGE>

          6.12  TITLES AND SUBTITLES.  The titles of the sections and
subsections of this Agreement are for convenience of reference only and are not
to be considered in construing this Agreement.

          6.13  COUNTERPARTS.  This Agreement may be executed in any number of
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one instrument.


                                       17
<PAGE>

      The foregoing Agreement is hereby executed as of the date first above
written.


COCENSYS, INC.                         AMERICAN HOME PRODUCTS CORPORATION
213 Technology Drive                   5 Giralda Farms
Irvine, CA 92718                       Madison, NJ  07940



By:                                    By:
   ---------------------------            ----------------------------
F. Richard Nichol                      Name:
President and Chief Executive Officer  Title:


                                          18
<PAGE>

                                       EXHIBITS


Exhibit A  -  CERTIFICATE OF DESIGNATION
Exhibit B  -  OPINION OF COMPANY'S COUNSEL


<PAGE>

                                      EXHIBIT A


                              CERTIFICATE OF DESIGNATION

<PAGE>

                   CERTIFICATE OF POWERS, DESIGNATION, PREFERENCES,
                                RIGHTS AND LIMITATIONS

                                          OF

                         SERIES C CONVERTIBLE PREFERRED STOCK

                                          OF

                                    COCENSYS, INC.

                           (Pursuant to Section 151 of the
                          Delaware General Corporation Law)

        COCENSYS, INC., a corporation organized and existing under the General
Corporation Law of the State of Delaware (hereinafter called the "Corporation"),
hereby certifies that the following resolution was adopted by the Board of
Directors of the Corporation as required by Section 151 of the General
Corporation Law at a meeting duly called and held on April 29, 1997:

         RESOLVED, that pursuant to the authority granted to and vested in the
    Board of Directors of the Corporation in accordance with the provisions of
    its Amended and Restated Certificate of Incorporation, the Board of
    Directors hereby creates a series of Preferred Stock, par value $.001 per
    share, of the Corporation and hereby states the designation and number of
    shares, and fixes the relative rights, preferences and limitations thereof
    (in addition to the provisions set forth in the Restated Certificate of
    Incorporation of the Corporation, which are applicable to the Preferred
    Stock of all classes and series), as follows:

    Series C Convertible Preferred Stock:

         SECTION 1. DESIGNATION AND AMOUNT. One Hundred Thousand (100,000)
    shares of Preferred Stock, $.001 par value, are designated "Series C
    Convertible Preferred Stock" with the rights, preferences, privileges and
    restrictions specified herein (the


                                          1.
<PAGE>

    "Series C Preferred Stock"). Such number of shares may be not increased or
    decreased without the consent of the holder.

         SECTION 2. DIVIDENDS AND DISTRIBUTIONS. The holders of the Series C
    Preferred Stock shall be entitled to receive, when, as and if declared by
    the Board of Directors, out of funds legally available therefor, dividends
    at the rate per share equal to any dividend declared or paid per share to
    the Common Stock of the Corporation ("Common Stock"). The right to such
    dividends on the Series C Preferred Stock shall be non-cumulative.

         SECTION 3. VOTING RIGHTS. Except as set forth herein. or as otherwise
    provided by law, holders of Series C Preferred Stock shall have no special
    voting rights and their consent shall not be required (except to the extent
    they are entitled to vote with holders of Common Stock as set forth herein)
    for taking any corporate action.

         SECTION 4. LIQUIDATION PREFERENCE. In the event of any liquidation,
    dissolution or winding up of the Corporation, either voluntary or
    involuntary (a "Liquidation Event"), the holders of the Series C Preferred
    Stock shall be entitled to receive, prior and in preference to any
    distribution of any of the assets or surplus funds of the Corporation to
    the holders of the Common Stock or Junior Preferred Stock of the
    Corporation, an amount per share (as adjusted for any combinations,
    consolidations, stock distributions or stock dividends with respect to such
    shares) equal to the quotient of (a) $5,000,000 divided by (b) the number
    of shares of Series C Preferred Stock issued and outstanding as of the date
    of such Liquidation Event. If upon the occurrence of such Liquidation
    Event, the assets and funds thus distributed among the holders of the
    Series C Preferred Stock shall be insufficient to permit the payment to
    such holders of the full aforesaid preferential amount, then the entire 
    assets and funds of the Corporation legally available for distribution shall
    be distributed among the holders of the Series C Preferred Stock in
    proportion to the shares of Series C Preferred Stock then held by them.

         SECTION 5. CONVERSION. Subject to the limitations set forth in
    Subsection (B) below, the Series C Preferred Stock shall convert only as
    follows:

         (A) CONVERSION AT HOLDER'S OPTION. At any time after May _, 1999, the
    Series C Preferred Stock shall be convertible, in whole or in part, on a
    maximum of three occasions, at the


                                          2.
<PAGE>

    option of the holder, into such number of fully paid and nonassessable
    shares of Common Stock equal to the quotient of (a) the product of $50 and
    the number of shares of Series C Preferred Stock being converted, divided
    by (b) the Conversion Price.

    The "Conversion Prices" shall be equal to the greater of:

         (i)  $[5.43] or

         (ii) the lesser of:

              (x)  the Future Market Price x 0.80 or

              (y)  $[7.76];

    PROVIDED, HOWEVER, that if the Future Market Price is less than $[3.88],
    the Conversion Price shall be $[4.37].

    The "Future Market Price" set forth above shall be the average closing
    price of the Common Stock for the period commencing on the 23rd trading day
    prior to the date upon which the holder delivers notice to the Corporation
    of such conversion (each, a "Conversion Date") and ending on the third
    trading day prior to the Conversion Date, as reported in the WALL STREET
    JOURNAL, WESTERN EDITION.

         (B) ADJUSTMENTS FOR COMBINATIONS OR SUBDIVISIONS OF COMMON STOCK. In
    the event the Corporation at any time or from time to time shall declare or
    pay any dividend on the Common Stock payable in Common Stock or in any
    right to acquire Common Stock, or shall effect a subdivision of the
    outstanding shares of Common Stock into a greater number of shares of
    Common Stock (by stock split, reclassification or otherwise), or in the
    event the outstanding shares of Common Stock shall be combined or
    consolidated, by reclassification or otherwise, into a lesser number of
    shares of Common Stock, then the maximum and minimum number of shares of
    Common Stock into which the Series C Preferred Stock may be converted,
    shall be proportionately decreased or increased, as appropriate.

         (C) MECHANICS OF CONVERSION. Before any holder of Series C Preferred
    Stock shall be entitled to receive shares of Common Stock, he shall
    surrender the certificate or certificates thereof, duly endorsed, at the
    office of the Corporation or of any transfer agent for such stock, and
    shall state therein the name or


                                          3.
<PAGE>

    names in which he wishes the certificate or certificates shares of Common
    Stock to be issued. The Corporation shall, as soon as practicable
    thereafter, issue and deliver at such office to such holder of Series C
    Preferred Stock, a certificate or certificates for the number of shares of
    Common Stock to which he shall be entitled as aforesaid. Such conversion
    shall be deemed to have been made on the Conversion Date, and the person or
    persons entitled to receive the shares of Common Stock issuable upon such
    conversion shall be treated for all purposes as the record holder or
    holders of such shares of Common Stock on such date.

         (D) RESERVATION OF STOCK ISSUABLE UPON CONVERSION. The Corporation
    shall at all times reserve and keep available out of its authorized but
    unissued shares of Common Stock, solely for the purpose of effecting the
    conversion of the shares of the Series C Preferred Stock, such number of
    its shares of Common Stock as shall from time to time be sufficient to
    effect the conversion of all outstanding shares of the Series C Preferred
    Stock.

         (E) FRACTIONAL SHARES. No fractional share shall be issued upon the
    conversion of any share or shares of Series C Preferred Stock. All shares
    of Common Stock (including fractions thereof) issuable upon conversion of
    Series C Preferred Stock shall be aggregated for purposes of determining
    whether the conversion would result in the issuance of any fractional
    share. If, after the aforementioned aggregation, the conversion would
    result in the issuance of a fraction of a share of Common Stock, the
    Corporation shall, in lieu of issuing any fractional share, pay the holder
    otherwise entitled to such fraction a sum in cash equal to the closing
    price of the Common Stock on the date of conversion, multiplied by such
    fraction.

         (F) REORGANIZATION, RECLASSIFICATION, CONSOLIDATION, MERGER OR SALE.
    If any (i) reorganization of the capital stock of the Corporation, (ii)
    consolidation or merger of the Corporation in which the Corporation is not
    the surviving corporation, or (iii) sale of all or substantially all of the
    Corporation's assets to another corporation (each, an "Event") shall be
    effected in such a way that holders of Common Stock shall be entitled to
    receive securities, cash or other assets or property, the first Conversion
    Date shall be accelerated to the date immediately preceding such Event, or
    such other date necessary to assure that any holder of Series C Preferred
    Stock receives such shares of stock, securities or other assets or property
    as may be issued or payable with respect to or in exchange for shares of
    Common Stock.


                                          4.
<PAGE>

         SECTION 6. NO REDEMPTION. The shares of Series C Preferred Stock shall
    not be redeemable.

         SECTION 7. AMENDMENT. The Restated Certificate of Incorporation of the
    Corporation shall not be amended in any manner which would materially alter
    or change the powers, preferences or special rights of the Series C
    Preferred Stock so as to affect them adversely without the affirmative vote
    of the holders of at least two-thirds of the outstanding shares of Series C
    Preferred Stock, voting together as a single class.


                                          5.
<PAGE>

    IN WITNESS WHEREOF the undersigned have executed this certificate as of
May ___, 1997.

                                       ---------------------------------------
                                       F. Richard Nichol, Ph.D.
                                       President and Chief Executive Officer

                                       ---------------------------------------
                                       Alan C. Mendelson
                                       Secretary


                                          6.
<PAGE>

                                      EXHIBIT B


                             OPINION OF COMPANY'S COUNSEL


<PAGE>

                                      EXHIBIT B
                                   FORM OF OPINION


May ___, 1997


American Home Products Corporation
5 Giralda Farms
Madison, NJ  07940

RE:  SALE AND PURCHASE OF COCENSYS, INC. SERIES C PREFERRED STOCK

Gentlemen:

We have acted as counsel for CoCensys, Inc., a Delaware corporation (the
"Company"), in connection with the issuance and sale of 100,000 shares of the
Company's Series C Preferred Stock to American Home Products Corporation, a
Delaware corporation ("Purchaser"), pursuant to the terms of that certain Stock
Purchase Agreement, dated May ___, 1997, by and between the Company and
Purchaser (the "Agreement").  The shares of Company Series C Preferred Stock
issued to Purchaser at the closing (the "Closing") are referred to herein as the
"Shares".  We are rendering this opinion pursuant to Section 5.1(b) of the
Agreement.  Except as otherwise defined herein, capitalized terms used but not
defined herein have the respective meanings given to them in the Agreement.

In connection with this opinion, we have examined and relied upon the
representations and warranties as to factual matters contained in and made
pursuant to the Agreement by the parties thereto and originals or copies
certified to our satisfaction, of such records, documents, certificates,
opinions, memoranda and other instruments as in our judgment are necessary or
appropriate to enable us to render the opinion expressed below.  Where we render
an opinion "to the best of our knowledge" or concerning an item "known to us" or
our opinion otherwise refers to our knowledge, it is based solely upon (i) an
inquiry of attorneys within this firm who perform legal services for the
Company, (ii) receipt of a certificate executed by an officer of the Company
covering such matters, and (iii) such other investigation, if any, that we
specifically set forth herein.

In rendering this opinion, we have assumed:  the genuineness and authenticity of
all signatures on original documents; the authenticity of all documents
submitted to us as originals; the conformity to originals of all documents
submitted to us as copies; the accuracy, completeness and authenticity of
certificates of public officials; and the due authorization, execution and
delivery of all documents where authorization, execution and delivery are
prerequisites to the effectiveness of such documents (except the due
authorization, execution and delivery of the Agreement by the Company).  We have
also assumed: that all individuals executing and delivering documents had the
legal capacity to so execute and deliver; that you have received all documents
you were to receive under the Agreement; that the Agreement is an obligation
binding upon you; if you are a corporation or other entity, that you have filed
any required California franchise or income tax returns and have paid any
required


<PAGE>

American Home Products Corporation
May ___, 1997
Page 2


California franchise or income taxes; and that there are no extrinsic agreements
or understandings among the parties to the Agreement that would modify or
interpret the terms of the Agreement or the respective rights or obligations of
the parties thereunder.

Our opinion is expressed only with respect to the federal laws of the United
States of America and the laws of the State of California and the General
Corporation Law of the State of Delaware.  We express no opinion as to whether
the laws of any particular jurisdiction apply, and no opinion to the extent that
the laws of any jurisdiction other than those identified above are applicable to
the subject matter hereof.  We are not rendering any opinion as to compliance
with any antifraud law, rule or regulation relating to securities, or to the
sale or issuance thereof.

Our opinions in paragraphs 5, 6 and 7 below as they relate to the Conversion
Shares are based upon the hypotheses that the Shares are convertible, and are
being converted, on the date hereof.

On the basis of the foregoing, in reliance thereon and with the foregoing
qualifications, we are of the opinion that:

    1.   The Company has been duly incorporated and is a validly existing
corporation in good standing under the laws of the State of Delaware.

    2.   The Company has the requisite corporate power to own or lease its
property and assets and to conduct its business as it is currently being
conducted and, to the best of our knowledge, is qualified as a foreign
corporation to do business in each jurisdiction in the United States in which
the ownership of its property or the conduct of its business requires such
qualification and where any statutory fines or penalties or any corporate
disability imposed for the failure to qualify would materially or adversely
affect the Company, its assets, financial condition or operations.

    3.   The Agreement has been duly and validly authorized, executed and
delivered by the Company and constitutes a valid and binding agreement of the
Company in accordance with its terms, except as rights to indemnity thereunder
may be limited by applicable laws and except as enforcement may be limited by
applicable bankruptcy, insolvency, reorganization, arrangement, moratorium or
other similar laws affecting creditors' rights, and subject to general equity
principles and to limitations on availability of equitable relief, including
specific performance.

    4.   The Shares have been duly authorized and, upon issuance and delivery
in accordance with the terms of the Agreement, will be validly issued, fully
paid and nonassessable.  The


<PAGE>

American Home Products Corporation
May ___, 1997
Page 3

Conversion Shares have been duly authorized and, upon issuance and delivery in
accordance with the Certificate of Designation, will be validly issued, fully
paid and nonassessable.

    5.   The issuance and sale of the Shares and the issuance of the Conversion
Shares, in each case as contemplated by the Agreement, do not violate any
provision of the Company's Amended and Restated Certificate of Incorporation or
Bylaws and do not violate or contravene (a) any governmental statute, rule or
regulation applicable to the Company or (b) any order, writ, judgment,
injunction, decree, determination or award which has been entered against the
Company and of which we are aware, the violation or contravention of which would
materially and adversely affect the Company, its assets, financial condition or
operations.

    6.   All consents, approvals, authorizations, or orders of, and filings,
registrations, and qualifications with any regulatory authority or governmental
body in the United States required for the issuance and sale of the Shares and
the issuance of the Conversion Shares, in each case as contemplated by the
Agreement, have been made or obtained.

    7.   The issuance and sale of the Shares and the issuance of the Conversion
Shares, in each case as contemplated by the Agreement is exempt from the
registration requirements of the Securities Act of 1933, as amended.

This opinion is intended solely for your benefit and is not to be made available
to or be relied upon by any other person, firm, or entity without our prior
written consent.

Very truly yours,

COOLEY GODWARD LLP



By ________________________

<PAGE>

                                                                         DOC. 3
                                                                   EXHIBIT 10.3


                       DEVELOPMENT AND COMMERCIALIZATION
                               AGREEMENT (NO. 2)
                                           
                                           
                                           
                                    BETWEEN
                                           
                                           
                                           
                                COCENSYS, INC.,
                                           
                                           
                                      AND
                                           
                                           
                           WYETH-AYERST LABORATORIES
                                           

<PAGE>

                               TABLE OF CONTENTS

                                                                           PAGE

1.  DEFINITIONS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  1
    1.1  "Affiliate(s)". . . . . . . . . . . . . . . . . . . . . . . . . . .  1
    1.2  "Agreement (No. 1)" . . . . . . . . . . . . . . . . . . . . . . . .  1
    1.3  "Back-Up Compound Candidate". . . . . . . . . . . . . . . . . . . .  1
    1.4  "Back-Up Program" . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.5  "Beginning of [     *     ] . . . . . . . . . . . . . . . . . . . .  2
    1.6  "Beginning of [     *     ] . . . . . . . . . . . . . . . . . . . .  2
    1.7  "CO 2-6749" . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.8  "CoCensys Patent Rights". . . . . . . . . . . . . . . . . . . . . .  2
    1.9  "Commercially Reasonable Efforts" . . . . . . . . . . . . . . . . .  2
    1.10 "Control" . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.11 "Development" . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.12 "Epalon". . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.13 "FDA" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.14 "Field" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  2
    1.15 "First Commercial Sale" . . . . . . . . . . . . . . . . . . . . . .  3
    1.16 "Fully Burdened Cost" . . . . . . . . . . . . . . . . . . . . . . .  3
    1.17 "Good Clinical Practice". . . . . . . . . . . . . . . . . . . . . .  3
    1.18 "Good Laboratory Practice". . . . . . . . . . . . . . . . . . . . .  3
    1.19 "Good Manufacturing Practice" . . . . . . . . . . . . . . . . . . .  3
    1.20 [     *     ] . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
    1.21 "IND" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
    1.22 "Intellectual Property Rights". . . . . . . . . . . . . . . . . . .  4
    1.23 "Invention" . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
    1.24 "Know-How". . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
    1.25 "Licensed Compound" . . . . . . . . . . . . . . . . . . . . . . . .  5
    1.26 "MAA" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
    1.27 "Major Market Countries". . . . . . . . . . . . . . . . . . . . . .  5
    1.28 "NDA" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
    1.29 "Net Sales" . . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
    1.30 [     *     ] . . . . . . . . . . . . . . . . . . . . . . . . . . .  5
    1.31 "Non-Scheduled Product" . . . . . . . . . . . . . . . . . . . . . .  5
    1.32 "Patent Rights" . . . . . . . . . . . . . . . . . . . . . . . . . .  6
    1.33 "Phase I," "Phase II," and "Phase III". . . . . . . . . . . . . . .  6
    1.34 "Product" . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
    1.35 "Regulatory Approval" . . . . . . . . . . . . . . . . . . . . . . .  6
    1.36 "RoW" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
    1.37 "Royalty Term". . . . . . . . . . . . . . . . . . . . . . . . . . .  6
    1.38 "Scheduled Product" . . . . . . . . . . . . . . . . . . . . . . . .  6


                                       i.

* Confidential treatment requested

<PAGE>

                               TABLE OF CONTENTS
                                   (CONTINUED)

                                                                           PAGE

    1.39 "Third Party(ies)". . . . . . . . . . . . . . . . . . . . . . . . .  7
    1.40 "Trademark" . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
    1.41 "USA" . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
    1.42 "Wyeth-Ayerst Patent Rights". . . . . . . . . . . . . . . . . . . .  7

2.  DEVELOPMENT OF LICENSED COMPOUND . . . . . . . . . . . . . . . . . . . .  7
    2.1  General Obligations . . . . . . . . . . . . . . . . . . . . . . . .  7
    2.2  Records, Reports and Information Exchange . . . . . . . . . . . . .  7
    2.3  Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
    2.4  Funding of the Development. . . . . . . . . . . . . . . . . . . . .  8
    2.5  Regulatory Approvals. . . . . . . . . . . . . . . . . . . . . . . .  8

3.  BACK-UP COMPOUND CANDIDATES. . . . . . . . . . . . . . . . . . . . . . .  8

4.  INDICATIONS; EXCLUSIVITY . . . . . . . . . . . . . . . . . . . . . . . .  8
    4.1  Indications . . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
    4.2  No [     *     ]by CoCensys [     *     ] . . . . . . . . . . . . .  9
    4.3  No [     *     ]. . . . . . . . . . . . . . . . . . . . . . . . . .  9

5.  LICENSE GRANTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  9
    5.1  Licenses to Wyeth-Ayerst. . . . . . . . . . . . . . . . . . . . . .  9
    5.2  Licenses upon Expiration. . . . . . . . . . . . . . . . . . . . . . 10

6.  CONSIDERATION TO COCENSYS. . . . . . . . . . . . . . . . . . . . . . . . 10
    6.1  Payments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
    6.2  Method of Payment of Payments . . . . . . . . . . . . . . . . . . . 11
    6.3  Payments for Back-Up Compound Candidates. . . . . . . . . . . . . . 11
    6.4  Royalties and Profit Sharing. . . . . . . . . . . . . . . . . . . . 11

7.  MARKETING AND ROYALTIES IN THE ROW . . . . . . . . . . . . . . . . . . . 11
    7.1  Marketing by Wyeth-Ayerst . . . . . . . . . . . . . . . . . . . . . 11
    7.2  Commercial and Regulatory Diligence . . . . . . . . . . . . . . . . 11
    7.3  Annual Net Sales Calculation. . . . . . . . . . . . . . . . . . . . 12
    7.4  Non-Scheduled Product Royalty in the RoW. . . . . . . . . . . . . . 12
    7.5  Scheduled Product Royalty.. . . . . . . . . . . . . . . . . . . . . 12
    7.6  Payments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
    7.7  Adjustment to Royalties in RoW. . . . . . . . . . . . . . . . . . . 13


                                      ii.

* Confidential treatment requested

<PAGE>

                               TABLE OF CONTENTS
                                   (CONTINUED)

                                                                           PAGE

8.  ACCOUNTS AND RECORDS . . . . . . . . . . . . . . . . . . . . . . . . . . 14
    8.1  Records . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
    8.2  Audits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
    8.3  Foreign Exchange. . . . . . . . . . . . . . . . . . . . . . . . . . 15
    8.4  Sales by Sublicensees . . . . . . . . . . . . . . . . . . . . . . . 15
    8.5  Currency Blockage . . . . . . . . . . . . . . . . . . . . . . . . . 15
    8.6  Withholding . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

9.  TRADEMARKS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

10. MANUFACTURING AND DISTRIBUTION . . . . . . . . . . . . . . . . . . . . . 16
    10.1 Primary Manufacture . . . . . . . . . . . . . . . . . . . . . . . . 16
    10.2 Second Source . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
    10.3 Exchange of Information . . . . . . . . . . . . . . . . . . . . . . 16
    10.4 Compliance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

11. PROSECUTION, MAINTENANCE AND INFRINGEMENT OF INTELLECTUAL PROPERTY
    RIGHTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
    11.1 Patentable Inventions . . . . . . . . . . . . . . . . . . . . . . . 16
    11.2 Prosecution and Maintenance of Patent Rights. . . . . . . . . . . . 17
    11.3 Patent Extensions . . . . . . . . . . . . . . . . . . . . . . . . . 17
    11.4 Cooperation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
    11.5 Infringement of Intellectual Property Rights. . . . . . . . . . . . 18
    11.6 Infringement of Third Party Patent Rights . . . . . . . . . . . . . 19

12. FORCE MAJEURE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

13. TERM AND TERMINATION . . . . . . . . . . . . . . . . . . . . . . . . . . 20
    13.1 General Conditions of Expiration and Termination. . . . . . . . . . 20
    13.2 Term. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
    13.3 Termination for Breach. . . . . . . . . . . . . . . . . . . . . . . 21
    13.4 No Limit on Remedies. . . . . . . . . . . . . . . . . . . . . . . . 22
    13.5 Unilateral Termination by Wyeth-Ayerst. . . . . . . . . . . . . . . 22
    13.6 Automatic Termination of Agreement (No. 1). . . . . . . . . . . . . 22

14. ASSIGNMENT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
    14.1 Assignment to Affiliates. . . . . . . . . . . . . . . . . . . . . . 22
    14.2 Other Permitted Assignment. . . . . . . . . . . . . . . . . . . . . 22
    14.3 Binding Nature of Assignment. . . . . . . . . . . . . . . . . . . . 22


                                      iii.

<PAGE>

                               TABLE OF CONTENTS
                                   (CONTINUED)

                                                                           PAGE


15. INDEMNIFICATION. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
    15.1 Cross Indemnification . . . . . . . . . . . . . . . . . . . . . . . 23
    15.2 Insurance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

16. WARRANTIES AND REPRESENTATIONS . . . . . . . . . . . . . . . . . . . . . 24
    16.1 General.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

17. CONFIDENTIAL INFORMATION . . . . . . . . . . . . . . . . . . . . . . . . 24
    17.1 Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
    17.2 Exceptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
    17.3 Permitted Disclosures . . . . . . . . . . . . . . . . . . . . . . . 25
    17.4 Disclosure of Agreement . . . . . . . . . . . . . . . . . . . . . . 25
    17.5 Publicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
    17.6 Publication . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

18. MISCELLANEOUS. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
    18.1 No Waiver of Contractual Rights . . . . . . . . . . . . . . . . . . 26
    18.2 Execution and Amendments. . . . . . . . . . . . . . . . . . . . . . 26
    18.3 Severability. . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
    18.4 Relationship between the Parties. . . . . . . . . . . . . . . . . . 26
    18.5 Correspondence and Notices. . . . . . . . . . . . . . . . . . . . . 26
    18.6 Choice of Law . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
    18.7 Counterparts. . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
    18.8 Appointment of Wyeth-Ayerst International, Inc. . . . . . . . . . . 27


                                      iv.

<PAGE>

                 DEVELOPMENT AND COMMERCIALIZATION AGREEMENT (NO. 2)


    THIS DEVELOPMENT AND COMMERCIALIZATION AGREEMENT (NO. 2) (the 
"Agreement") is entered into as of the 12th day of May, 1997 (the "Effective 
Date"), by and between CoCensys, Inc., a company incorporated under the laws 
of the State of Delaware, with its principal place of business at 213 
Technology Drive, Irvine, California 92618, USA ("CoCensys"), and American 
Home Products Corporation, acting through its Wyeth-Ayerst Laboratories 
Division, a company incorporated under the laws of the State of Delaware, 
with its principal place of business at 555 Lancaster Avenue, St. Davids, 
Pennsylvania 19087, USA ("Wyeth-Ayerst"). Both CoCensys and Wyeth-Ayerst are 
referred to individually as a "Party" and collectively as the "Parties."

    WHEREAS, CoCensys has discovered, has rights to and is developing that 
certain compound CO 2-6749 (as defined in Article 1.8 below); and

    WHEREAS, Wyeth-Ayerst would like to obtain the worldwide (except in the 
USA) rights to develop and commercialize CO 2-6749 or a back-up compound 
therefor; 

    NOW, THEREFORE, in consideration of the foregoing premises and the mutual 
premises, covenants and conditions contained in this Agreement, the Parties 
agree as follows:

1.  DEFINITIONS.

    For the purposes of this Agreement, the terms hereunder shall have the
    meanings as defined below:

    1.1  "AFFILIATE(S)" shall mean, in the case of either CoCensys or 
         Wyeth-Ayerst, any corporation, joint venture, or other business 
         entity which directly or indirectly controls, is controlled by, or is 
         under common control with that Party. "Control," as used in this 
         Article 1.1, shall mean having the power to direct, or cause the 
         direction of, the management and policies of an entity, whether 
         through ownership of voting securities, by contract or otherwise.

    1.2  "AGREEMENT (NO. 1)" shall mean that Development and Commercialization
         Agreement (No.1) between the Parties relating to development and
         commercialization of CO 2-6749 or a back-up compound therefore in the
         USA, entered into on even date with the Effective Date.

    1.3  "BACK-UP COMPOUND CANDIDATE" shall mean any Epalon meeting the
         criteria set forth in Exhibit A as determined by CoCensys and
         submitted by CoCensys to Wyeth-Ayerst as a potential substitute for CO
         2-6749.  "Back-Up Compound Candidate" shall include any prodrugs, salt
         forms and other biologically active isomers or enantiomers of such
         CoCensys Epalon.


                                       1.

<PAGE>

    1.4  "BACK-UP PROGRAM" shall mean the program for identification of Back-Up
         Compound Candidates as conducted by CoCensys pursuant to Agreement
         (No. 1)

    1.5  "BEGINNING OF [     *     ] shall mean the date upon which the 
         [       *          ] for a Product.

    1.6  "BEGINNING OF [     *     ] shall mean the date upon which the 
         [       *          ] for a Product.

    1.7  "CO 2-6749" shall mean the Epalon [          *          ] and any
         prodrugs, including specifically CO 6-0549, salt forms and other
         biologically active isomers or enantiomers of this Epalon.  A diagram
         of the chemical structure of each of CO 2-6749 and CO 6-0549 is set
         forth on Exhibit B.

    1.8  "COCENSYS PATENT RIGHTS" shall mean all Patent Rights owned or
         Controlled by CoCensys.  A list of the CoCensys Patent Rights existing
         as of the Effective Date is set out in Exhibit C hereto.

    1.9  "COMMERCIALLY REASONABLE EFFORTS" shall mean efforts and resources
         normally used by a party for a compound owned by it or to which it has
         rights, which is of similar market potential at a similar stage in its
         product life, taking into account the competitiveness of the
         marketplace, the proprietary position of the compound, the regulatory
         structure involved, the profitability of the applicable products, and
         other relevant factors.

    1.10 "CONTROL" shall mean licensed with the right to grant sublicenses
         without violating the terms of any Third Party agreement.

    1.11 "DEVELOPMENT" shall mean the pre-clinical development of a Licensed
         Compound and clinical development for use in the Field in the RoW of a
         Product through and including Regulatory Approval.

    1.12 "EPALON" shall mean the class of neuroactive steroid compounds that
         interact with GABAA receptor complexes.

    1.13 "FDA" shall mean the Food and Drug Administration of the USA.

    1.14 "FIELD" shall mean the treatment in humans of [          *          ]
         in the Diagnostic and Statistical Manual of Mental Disorders, Fourth
         Edition ("DSM-IV").  Also, specifically to be included under [         
         *          ] defined by research criteria in DSM-IV.  It is understood
         by the Parties that the above-named disorders may be defined
         differently in future editions of the Diagnostic and 


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         Statistical Manual of Mental Disorders, but that, for purposes of 
         this Agreement, the definition of Field shall always be with 
         reference to those diseases which fall within the definition of the 
         above-named disorders in the edition of DSM-IV which is current as of 
         the Effective Date. Expressly excluded from the Field are 
         [          *          ].

    1.15 "FIRST COMMERCIAL SALE" shall mean the first sale of a Product in a
         given country after the Product has been granted Regulatory Approval
         by the competent authorities in that country.

    1.16 "FULLY BURDENED COST" shall mean the sum of the costs set forth on
         Exhibit D, to the extent allocable to Product.  

    1.17 "GOOD CLINICAL PRACTICE" or "GCP" shall mean the then current
         standards for clinical trials for pharmaceuticals, as set forth in the
         United States Federal Food, Drug and Cosmetics Act and applicable
         regulations promulgated thereunder, as amended from time to time, and
         such standards of good clinical practice as are required by the
         European Union and other organizations and governmental agencies in
         countries in which the Product is intended to be sold, to the extent
         such standards are not in contravention with United States GCP.

    1.18 "GOOD LABORATORY PRACTICE" or "GLP" shall mean the then current
         standards for laboratory activities for pharmaceuticals, as set forth
         in the United States Federal Food, Drug and Cosmetics Act and
         applicable regulations promulgated thereunder, as amended from time to
         time, and such standards of good laboratory practice as are required
         by the European Union and other organizations and governmental
         agencies in countries in which the Product is intended to be sold, to
         the extent such standards are not in contravention with United States
         GLP.

    1.19 "GOOD MANUFACTURING PRACTICE" or "GMP" shall mean the current
         standards for the manufacture of pharmaceuticals, as set forth in the
         United States Federal Food, Drug and Cosmetics Act and applicable
         regulations promulgated hereunder, as amended from time to time, and
         such standards of good manufacturing practice as are required by the
         European Union and other organizations and governmental agencies in
         countries in which the Product is intended to be sold, to the extent
         such standards are not in contravention with United States GMP.

    1.20 [          *          ] shall mean the development milestone 
         [          *          ].

    1.21 "IND" shall mean an Investigational New Drug Application as defined in
         the United States Federal Food, Drug and Cosmetics Act and applicable
         regulations promulgated thereunder, as amended from time to time.  


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    1.22 "INTELLECTUAL PROPERTY RIGHTS" shall mean all Patent Rights,
         trademarks, copyrights, know-how and/or trade secrets which are owned
         or Controlled by one Party hereto (with the right to license) or
         jointly by the Parties, with regard to the development, manufacture,
         importing, use, marketing and/or sale of the Product.

    1.23 "INVENTION" shall mean an invention conceived in the course of the
         performance of and within the scope of this Agreement.

    1.24 "KNOW-HOW" shall mean all know-how, processes, information and data
         including any copyright relating thereto owned or controlled by either
         Party (with the right to have or disclose) as of the Effective Date or
         acquired during the term of this Agreement relating to:

         (a)  the Licensed Compound;

         (b)  any Back-Up Compound;

         (c)  any Product containing (a) or (b);

         (d)  methods of making any of (a), (b) or (c);

         (e)  any component of (c);

         (f)  any intermediate in the making of any of (a), (b), (c), or (e);

         (g)  any method of using any of (a), (b), (c), (e), or (f); and/or

         (h)  any use of (a), (b) or (c).

         The term "Know-How," however, shall not include any know-how,
         processes, information and data which is, as of the Effective Date or
         becomes later on, generally available to the public.

    1.25 "LICENSED COMPOUND" shall mean CO 2-6749 and any Back-Up Compound
         Candidate.

    1.26 "MAA" shall mean the Marketing Authorization Application filed in the
         European Community for approval to market and sell a pharmaceutical
         product, whether by centralized procedure with the Committee for
         Proprietary Medicinal Products or otherwise.

    1.27 "MAJOR MARKET COUNTRIES" shall mean Germany, the United Kingdom, Italy
         and France.


                                       4.

<PAGE>

    1.28 "NDA" shall mean a New Drug Application, as defined in the United
         States Federal Food, Drug and Cosmetic Act and applicable regulations
         promulgated thereunder as amended from time to time.

    1.29 "NET SALES" shall mean proceeds from sales of the Product by either
         Party, its Affiliates or sublicensees, as appropriate, to Third
         Parties, less the sum of (a) and (b) where (a) is a provision,
         determined under generally accepted accounting principles in the
         United States, for [          *          ] and (b) is 
         [          *          ].

         Sales of Product by and between a Party and its Affiliates are not
         sales to Third Parties and shall be excluded from Net Sales
         calculations for all purposes.

    1.30 [     *     ] shall have the meaning set forth in Article 4.1.

    1.31 "NON-SCHEDULED PRODUCT" shall mean a Product to be sold in the RoW
         that has received a designation similar to a "Schedule V" designation
         in the USA, as defined in 21 CFR Part 1308, or no scheduling
         designation in the course of Regulatory Approval from a foreign
         government.

    1.32 "PATENT RIGHTS" shall mean all patents or patent applications, in
         whatever country in the RoW, and all divisionals, continuations,
         continuations-in-part, reissues, extensions, supplementary protection
         certificates and foreign counterparts thereof in the RoW, existing as
         of the Effective Date or filed or issuing during the term of this
         Agreement, at least one claim of which covers:

         (a)  the Licensed Compound;

         (b)  any Back-Up Compound;

         (c)  any Product containing (a) or (b);

         (d)  methods of making any of (a), (b) or (c);

         (e)  any component of (c);

         (f)  any intermediate in the making of any of (a), (b), (c) or (e);

         (g)  any method of using any of (a), (b), (c), (e), or (f); and/or

         (h)  any use of (a), (b) or (c).


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    1.33 "PHASE I," "PHASE II," AND "PHASE III" shall mean the phases of the
         clinical development of pharmaceuticals as defined in the United
         States Federal Food, Drug and Cosmetics Act and/or applicable
         regulations promulgated thereunder, as amended from time to time, or
         any comparable foreign regulations.

    1.34 "PRODUCT" shall mean any pharmaceutical product containing a Licensed
         Compound in any formulation or mode of administration.

    1.35 "REGULATORY APPROVAL" shall mean all authorizations by the competent
         authorities which are required for the regular marketing, promotion,
         pricing and sale of the Product in a given country or regulatory
         jurisdiction.

    1.36 "ROW" shall mean all countries and territories in the world except the
         USA.

    1.37 "ROYALTY TERM" shall mean the period extending from First Commercial
         Sale in any country in the RoW until the later of (i) expiration of
         the last to expire patent within the Patent Rights necessary to make,
         use, import, offer for sale or sell the Product in one or more Major
         Market Countries, or (b) fifteen (15) years from First Commercial Sale
         in the first Major Market Country.

    1.38 "SCHEDULED PRODUCT" shall mean a Product to be sold in the RoW that
         has received a designation similar to a Schedule I, II, III or IV
         designation in the USA, as defined in 21 CFR Part 1308, in the course
         of Regulatory Approval from a foreign government.

    1.39 "THIRD PARTY(IES)" shall mean any person(s) or entity(ies) other than
         CoCensys, Wyeth-Ayerst or their Affiliates.

    1.40 "TRADEMARK" shall mean the trademark under which the Product shall be
         marketed as set out in Article 9.

    1.41 "USA" shall mean the United States of America, its territories and
         possessions and the Commonwealth of Puerto Rico.

    1.42 "WYETH-AYERST PATENT RIGHTS" shall mean all Patent Rights owned or
         Controlled by Wyeth-Ayerst.  A list of the Wyeth-Ayerst Patent Rights
         existing as of the Effective Date is set out in Exhibit E hereto.

2.  DEVELOPMENT OF LICENSED COMPOUND.

    2.1  GENERAL OBLIGATIONS.  Wyeth-Ayerst shall be responsible for the
         design, implementation and funding of all Development.  Wyeth-Ayerst
         agrees to use Commercially Reasonable Efforts to conduct the
         Development with the intent of obtaining Regulatory Approval in the
         RoW and bringing a Product in the Field 


                                       6.
<PAGE>

          to the market as soon as reasonably practicable. Wyeth-Ayerst shall 
          ensure that the Development is carried out adhering to 
          Wyeth-Ayerst's ethical and safety standards.  Wyeth-Ayerst shall 
          have the right to subcontract with third parties any of its 
          Development obligations   hereunder, without the consent or 
          approval of CoCensys.  In the event Wyeth-Ayerst intends to 
          exercise its right to subcontract one or more of its Development 
          obligations, it shall notify CoCensys of such intent and CoCensys 
          shall have the right to submit one or more proposals to 
          Wyeth-Ayerst to perform such one or more parts of such Development  
          activities.  Wyeth-Ayerst shall consider all such proposals 
          submitted by CoCensys on an equal basis with proposals submitted by 
          Third Party subcontractors for the same Development tasks.

     2.2  RECORDS, REPORTS AND INFORMATION EXCHANGE.

          2.2.1     TECHNOLOGY AND INFORMATION TRANSFER. CoCensys will provide 
                    to Wyeth-Ayerst all Know-How as Wyeth-Ayerst deems 
                    necessary to carry out the Development and [     *     ]
                    of the Product and to obtain Regulatory Approval.  All 
                    information transferred, provided or exchanged under this 
                    Article 2.2.1 will be subject to the confidentiality
                    requirements set forth in Article 17.

          2.2.2     RECORD KEEPING.  Wyeth-Ayerst will maintain records in 
                    sufficient detail and in good scientific manner appropriate
                    for Regulatory Approval and patent purposes.

          2.2.3     COMMUNICATION REGARDING THE DEVELOPMENT PROGRESS.  A 
                    project team shall be appointed by Wyeth-Ayerst and 
                    representatives thereof shall meet with representatives of 
                    CoCensys on a regular basis (but no less often than every 
                    six (6) months) to keep CoCensys apprised of the 
                    Development progress and to bring to its attention any 
                    problems or issues which may have an impact on the timing 
                    of the Development (e.g., regulatory submissions).

     2.3  COMPLIANCE.  Wyeth-Ayerst shall comply with all GLP, GCP and GMP in 
          the conduct of the Development.

     2.4  FUNDING OF THE DEVELOPMENT.  Wyeth-Ayerst shall be responsible for 
          one hundred percent (100%) of all costs, fees and expenses 
          associated with the Development and the obtaining of all Regulatory
          Approvals.

     2.5  REGULATORY APPROVALS.  [     *     ] shall file all regulatory 
          dossiers under its name.  [     *     ] shall own all Regulatory 
          Approvals.  [     *     ] shall have the right of reference to the 
          extent necessary to exercise its rights or to meet its


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          obligations hereunder.  [     *     ] shall be responsible for all 
          communications with regulatory agencies.

3.   BACK-UP COMPOUND CANDIDATES
     
      Unless otherwise provided, all of the Parties' rights and obligations 
      under this Agreement, including those regarding the development, 
      manufacture, distribution, marketing, sale, promotion, profit-sharing 
      and royalties of CO 2-6749 and the Product are applicable to any Back-Up 
      Compound Candidate either replacing CO 2-6749 or otherwise developed in 
      the Field pursuant to Agreement (No. 1).  The provisions herein 
      regarding CO 2-6749 and the Product shall apply to such Back-Up Compound 
      Candidate MUTATIS MUTANDIS.

4.   INDICATIONS; EXCLUSIVITY.

     4.1  INDICATIONS.  Wyeth-Ayerst shall have the right to  conduct 
          Development with respect to any Licensed Compound.  Wyeth-Ayerst 
          [   *   ] covenants that it shall not conduct clinical trials of any 
          Licensed Compound for [   *   ] in the Row except as provided under 
          this Article 4.1.  If Wyeth-Ayerst discovers or determines that any 
          Licensed Compound may have efficacy in the treatment of [   *   ] 
          and if Wyeth-Ayerst desires to pursue clinical trials of such Licensed
          Compound [     *     ] it will promptly notify CoCensys in writing and
          disclose to CoCensys its rationale therefor.  Wyeth-Ayerst shall have 
          the right to pursue such clinical trials for [     *     ] and market 
          and sell such Licensed Compound as though it were a Product developed 
          and sold for [   *    ]under this Agreement, subject to the Parties 
          negotiation of terms and conditions, including royalty rates, whether 
          and on what terms such Licensed Compound will be Co-Promoted by the 
          Parties, and other appropriate payment and other terms.  Following 
          such negotiation of such terms and conditions the Parties shall either
          enter into a separate agreement or amend this Agreement to so provide 
          for such terms and conditions.  In the event the Parties are unable to
          come to agreement as to the appropriate terms and conditions for the 
          development and commercialization of such Licensed Compound for 
          [     *     ] by Wyeth-Ayerst, the matter shall be referred to the 
          Chief Executive Officer of CoCensys and the President of Wyeth-Ayerst
          Laboratories, an Affiliate of Wyeth-Ayerst, for good faith 
          resolution, for a period of [    *     ] days.  If such matter is not
          resolved by the end of such [    *     ] day period, the Parties 
          shall be [     *      ]. Notwithstanding the foregoing, it is 
          expressly understood and


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          agreed that [    *     ] as used in this Agreement shall not include 
          [   *    ].
     
     4.2  NO [     *     ] BY COCENSYS [     *     ].  During the term of this 
          Agreement, CoCensys shall not [     *     ]

     4.3  NO [     *     ]  During the term of this Agreement, CoCensys will 
          not [     *     ] except under the terms of this Agreement, or as 
          otherwise agreed to by Wyeth-Ayerst.

5.   LICENSE GRANTS.

     5.1  LICENSES TO WYETH-AYERST.  Subject to the other
          provisions of this Agreement, CoCensys hereby grants to
          Wyeth-Ayerst:

          5.1.1     An exclusive license in the RoW, under its Intellectual 
                    Property Rights, to develop, manufacture and have
                    manufactured, import, use, market, offer for sale and sell 
                    Products, in the Field, and, subject to Article 4.1, for
                    any New Indication.

          5.1.1     The licenses granted in Article 5.1.1 shall be 
                    sublicensable by Wyeth-Ayerst outside the USA without 
                    the consent of CoCensys to Affiliates and Third Parties.  
                    Wyeth-Ayerst agrees to keep CoCensys informed as to such
                    sublicensing activities.

          5.1.2     Unless otherwise provided in this Agreement, Wyeth-Ayerst 
                    covenants that it shall not, nor shall it cause any 
                    Affiliate to, use or practice directly or indirectly any 
                    CoCensys Know-How, and, until expiration thereof, any
                    CoCensys Patent Rights for any purposes other than the 
                    development, manufacture, importation, use, marketing, offer
                    for sale or sale of the Product.

          5.1.3     Wyeth-Ayerst may at any time request and authorize CoCensys
                    to grant licenses directly to Affiliates of Wyeth-Ayerst 
                    wheresoever located by giving written notice to CoCensys
                    designating to whom a direct license is to be granted by 
                    CoCensys.  CoCensys shall promptly enter into a separate 
                    direct license agreement with each Affiliate of Wyeth-Ayerst
                    designated by Wyeth-Ayerst in such notice. All such direct 
                    license agreements shall be consistent with the terms of 
                    this Agreement, to the extent applicable, except for such
                    modifications as may be required by the laws, regulations 
                    and customs in the country in which the direct license 
                    agreement is to be performed.


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      5.2  LICENSES UPON EXPIRATION.  Upon expiration of the Royalty Term, 
           and provided all sums owing to CoCensys have been paid, 
           Wyeth-Ayerst shall have a [     *      ] where agreed under Article 
           4.1, under any remaining CoCensys Intellectual Property Rights.

6.   CONSIDERATION TO COCENSYS.

     6.1  PAYMENTS.  In further consideration of CoCensys' continuing 
          assistance in research and development of the Product, Wyeth-Ayerst 
          shall pay to CoCensys the following amounts at the time of the 
          following achievements with respect to the Product:

          6.1.1     [    *     ]  Upon [     *     ] Wyeth-Ayerst shall make to
                    CoCensys a non-refundable payment of [      *       ].

          6.1.2     [          *          ]  Upon [     *      ] 
                    Wyeth-Ayerst shall make to CoCensys a non-refundable payment
                    of [         *        ].

          6.1.3     [          *        ]  Upon [      *       ] Wyeth-Ayerst 
                    shall make to CoCensys a non-refundable payment of 
                    [   *   ]if the Product is a [   *  ] Product in such 
                    [   *   ], or [   *   ] if the Product is a [  *  ]
                    Product in such [   *   ].  If the Product is a [   *   ] 
                    Product in all [   *   ] Wyeth-Ayerst shall make to 
                    CoCensys an additional non-refundable payment of 
                    [   *     ].

          6.1.4     [     *     ]  Upon [          *          ]
                    Wyeth-Ayerst shall make to CoCensys a non-refundable payment
                    of [  *   ] if the Product is a [     *     ] Product or
                    [  *  ] if the Product is a [     *      ] Product.

     6.2  METHOD OF PAYMENT OF PAYMENTS.  All payments shall be made  by 
          Wyeth-Ayerst to CoCensys by way of wire transfer to CoCensys 
          within thirty (30) days from the date corresponding to the event 
          triggering the milestone payment.


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     6.3  PAYMENTS FOR BACK-UP COMPOUND CANDIDATES.  Each payment payable 
          pursuant to this Article 6 shall [     *     ] be payable 
          [     *     ] for the Product [     *     ].

     6.4  ROYALTIES AND PROFIT SHARING.  Wyeth-Ayerst shall, in addition to 
          the payments set forth above, also pay to CoCensys royalties and 
          such other amounts as set forth in Article 7.

7.   MARKETING AND ROYALTIES IN THE ROW.

     7.1  MARKETING BY WYETH-AYERST.  Wyeth-Ayerst shall have exclusive rights 
          to the Product in the countries of the RoW, and shall use 
          Commercially Reasonable Efforts to market, sell and distribute the 
          Product at its discretion in such countries through its own network
          and direct licensee Affiliates, and/or through the network of its 
          licensees/distributors, subject to Article 5.1.2.

     7.2  COMMERCIAL AND REGULATORY DILIGENCE.

          7.2.1     Within [     *     ] months of [     *     ] for the Product
                    in the USA or the European Union, Wyeth-Ayerst will commence
                    [     *      ] and notify CoCensys in writing of such event.

          7.2.2     Within [     *     ] months of [    *    ] Wyeth-Ayerst 
                    shall notify CoCensys in writing as to [         *        ].

          7.2.3     After [          *          ] Wyeth-Ayerst agrees that it 
                    will undertake commercial launch of the Product in such 
                    country [         *          ].

     7.3  ANNUAL NET SALES CALCULATIONS.  Annual Net Sales in the RoW of 
          [     *     ] and [     *     ] Products shall be first calculated on
          a country-by-country basis until the end of the Royalty Term.  Then 
          Net Sales of [     *    ] Products in all countries in the RoW shall 
          be added together to calculate annual Net Sales of [     *    ] 
          Products in the RoW; and Net Sales of [     *    ] Products in all 
          countries in the RoW shall be added together to calculate annual 
          Net Sales of [     *     ] Products in the RoW.  Finally, Net Sales 
          of [     *    ] Products and Net Sales of [     *     ] Products 
          shall be added together to calculate annual RoW Net Sales.


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     7.4  [     *     ] PRODUCT ROYALTY IN THE ROW.  In consideration of the 
          licenses granted to Wyeth-Ayerst by CoCensys under Article 5, 
          Wyeth-Ayerst shall pay to CoCensys a running royalty on annual Net 
          Sales of all [     *     ] Products in the RoW according to the
          following marginal rates:

          (a)  For annual RoW Net Sales which are less than or equal to [  *  ]
               million, [     *     ] of such RoW Net Sales which are allocable
               to Net Sales of [     *     ] Products; and

          (b)  For annual RoW Net Sales which are more than [    *     ] million
               but less than or equal to [    *    ] million, 
               [     *     ] of such RoW Net Sales which are allocable to Net 
               Sales of [   *   ] Products; and

          (c)  For annual RoW Net Sales which are more than [   *   ] million, 
               [   *   ] of such RoW Net Sales which are allocable to Net Sales
               of [   *   ] Products.

     7.5  [     *     ] PRODUCT ROYALTY.  In consideration of the licenses    
          granted to Wyeth-Ayerst by CoCensys under Article 5, Wyeth-Ayerst 
          shall pay to CoCensys a running royalty on Net Sales of all [   *   ]
          Products in the RoW according to the following marginal rates:

          (a)  For annual RoW Net Sales which are less than or equal to 
               [   *   ] million, [     *     ] of such RoW Net Sales which are
               allocable to Net Sales of [     *     ] Products; and

          (b)  For annual RoW Net Sales which are more than [  *   ] million 
               but less than or equal to [    *    ] million, [     *     ] of
               such RoW Net Sales which are allocable to Net Sales of 
               [    *    ] Products; and

          (c)  For annual RoW Net Sales which are more than [   *     ] million,
               [     *     ] of such RoW Net Sales which are allocable to Net 
               Sales of [    *   ] Products.


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     7.6  PAYMENTS.  All royalties payable to CoCensys under this Article 7
          shall be paid in U.S. Dollars within three (3) months after
          the close of each calendar quarter, or earlier if possible, during the
          Royalty Term.  Each payment shall be accompanied by a statement, on a 
          country by country basis, of the amount of Net Sales in the RoW during
          such quarter, the aggregate amount of Net Sales for the year-to-date 
          in the RoW, and amount of royalties due on such Net Sales.  For any 
          given royalty period during the first three (3) quarters of the year,
          Wyeth-Ayerst shall pay to CoCensys the royalty at the lowest rate 
          specified in Articles 7.4 and 7.5 applicable to the then current 
          year-to-date worldwide RoW Net Sales level. Each statement provided at
          the end of the fourth quarter shall contain a reconciliation of actual
          royalty payments made during that year, any adjustments to be made to 
          such royalty    amounts owing for such year, and the amount actually 
          owed for such year.  Any amounts owing to CoCensys shall be paid to 
          CoCensys at the time of such fourth quarter statement, in accordance 
          with the terms of this Article 7.6.  Any adjustments to royalties owed
          in the RoW pursuant to Articles 7.7.1 and 7.7.2 shall be done at the 
          end of the calendar year in which such event giving rise to such 
          adjustment occurred; PROVIDED, HOWEVER, that following the entry of 
          one or more generic products in any year, and where royalties were 
          reduced for that year pursuant to Article 7.7.1, the following year's
          royalty rate for quarterly royalty payments shall be at [     *     ]
          with a reconciliation upward at year end in the event sales of such
          generic product(s) do not rise to the level specified in 
          Article 7.7.1.
               
     7.7  ADJUSTMENT TO ROYALTIES IN ROW.
               
          7.7.1     GENERIC PRODUCTS.  In the event that, during the Royalty 
                    Term, a generic version of the Product is introduced in 
                    any country in the RoW by a Third Party, and if unit sales 
                    of all such generic product(s) constitute more than [   *  ]
                    of the combined unit sales in the RoW of both the Product 
                    and any such generic product(s), then the annual royalty
                    amount owed under Article 7.4 or 7.5 for such country shall
                    be reduced by [   *    ] such reduction to be done 
                    in the fourth quarter payment as described in Article 7.6.

          7.7.2     [     *     ]  In the event that at the end of a given 
                    calendar year [     *     ] (where [     *     ] = 
                    [          *          ] = the [       *       ] and 
                    [     *     ] = [     *     ] then Wyeth-Ayerst will provide
                    written notice to CoCensys of such fact and the Parties 
                    shall meet promptly thereafter to discuss and develop in 
                    good faith a commercially reasonable plan to [     *      ]
                    In the event that, at any time after the eight (8) month 
                    anniversary of the date of the first meeting to discuss the 
                    RoW 


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                    Cost Reduction Plan, [     *     ] (where [   *   ] = 
                    [     *     ] then, for so long as [    *     ] an amount 
                    equal to [     *     ] may be deducted from the royalty 
                    amount due CoCensys for such year; PROVIDED, HOWEVER, in
                    no event shall the royalty due CoCensys be less than that 
                    paid at the lowest applicable rate (i.e., [     *     ] 
                    for [     *     ] Products and [     *     ] for [    *    ]
                    Products, or [     *     ] respectively, where 
                    Article 7.7.1 applies) set forth in Article 7.4 or 7.5.

8.   ACCOUNTS AND RECORDS; WITHHOLDING TAX.

     8.1  RECORDS.  Wyeth-Ayerst shall keep accurate books and accounts 
          of record in connection with the manufacture, use and/or sale by or
          for it of the Products in sufficient detail to permit accurate 
          determination of all figures necessary for verification of royalties,
          profits, milestone payments and other compensation required to be
          paid hereunder. Wyeth-Ayerst shall maintain such records for a period
          of three (3) years after the end of the year in which they were 
          generated.

     8.2  AUDITS.  CoCensys, through an independent certified public accountant
          reasonably acceptable to Wyeth-Ayerst, shall have the right, at its 
          own expense, to access the books and records of Wyeth-Ayerst for the 
          sole purpose of verifying statements furnished by Wyeth-Ayerst 
          pursuant to Article 7.6.  Such access shall be conducted after 
          reasonable prior written notice to Wyeth-Ayerst and during ordinary 
          business hours and shall not be more frequent than once during each 
          calendar year.  CoCensys agrees to keep in strict confidence all 
          information learned in the course of such audit, except when it is 
          necessary to reveal such information in order to enforce its rights 
          under this Agreement.  CoCensys' right to have such records examined 
          shall survive termination or expiration of this Agreement.  In the 
          event such audit reveals an underpayment of [     *     ] or more of 
          the amount actually due, Wyeth-Ayerst shall reimburse CoCensys for 
          the costs of such audit in addition to promptly remitting to CoCensys
          the amount of any underpayment.
     
     8.3  FOREIGN EXCHANGE.  For the purpose of computing Net Sales for Products
          sold in a currency other than United States Dollars, such currency 
          shall be converted into United States Dollars in accordance with 
          Wyeth-Ayerst's customary and usual translation procedures, 
          consistently applied.

     8.4  SALES BY SUBLICENSEES.  In the event Wyeth-Ayerst grants 
          licenses or sublicenses to others to make or sell the Product, such 
          licenses or sublicenses shall include an obligation for the licensee 
          or sublicensee to account for and report its Net Sales of such 
          Products on the same basis as if such sales were Net Sales by 


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          Wyeth-Ayerst, and CoCensys shall receive royalties in the same amounts
          as if the Net Sales of the licensee or sublicensee were Net Sales 
          of Wyeth-Ayerst.
     
     8.5  CURRENCY BLOCKAGE.  In the event Wyeth-Ayerst is prevented from 
          making any payment under this Agreement by virtue of the Statutes,
          Laws, Codes or Governmental Regulations of the country from which 
          the payment is to be made, then such payments may be paid by 
          depositing them in the currency in which accrued to CoCensys'
          account in a bank acceptable to CoCensys in the country whose currency
          is involved.  If the Statutes, Laws, Codes or Governmental Regulations
          prohibit both transmittal and deposit of such payments, the obligation
          to pay, deposit, accrue or otherwise account for such payments in such
          country shall be suspended for so long as said prohibition shall be 
          in effect.

     8.6  WITHHOLDING.  All taxes, assessments and fees of any nature levied 
          or incurred on account of any payments accruing under this Agreement,
          by national, state or local governments, will be assumed and paid by 
          Wyeth-Ayerst, except taxes levied thereon as income to CoCensys and 
          if such taxes are required to be withheld by Wyeth-Ayerst they will 
          be deducted from payments due to CoCensys and will be timely paid by 
          Wyeth-Ayerst to the proper taxing authority for the account of 
          CoCensys, a receipt or other proof of payment therefor secured and 
          sent to CoCensys as soon as practicable.

9.   TRADEMARKS.

     [     *     ] shall select and own the Trademarks for marketing the Product
     in the RoW.  [     *     ] for (i) registration of such Trademarks and 
     (ii) bringing, maintaining and prosecuting any action to protect or defend
     such Trademarks shall be borne [     *     ]  At the termination of this 
     Agreement, [     *     ] shall [     *     ] have unrestricted ownership 
     of such Trademark(s) in the RoW.  

10.  MANUFACTURING AND DISTRIBUTION.

     10.1 PRIMARY MANUFACTURE.  [     *     ] shall manufacture or have 
          manufactured its requirements for clinical and commercial supplies 
          of the Product.  In fulfilling its manufacturing obligations 
          hereunder, [     *     ] will use at least the same level of effort 
          as it employs for its other products of similar scientific and 
          commercial promise.  If [     *     ] elects to have the Product
          manufactured, [     *     ] shall favorably consider using, but shall
          not be obligated to use, [     *    ] as its manufacturing 
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     10.2 SECOND SOURCE.  In order to ensure an uninterrupted supply of 
          the Product, the Parties intend to identify a Third Party manufacturer
          (the "Second Source") to manufacture the Product in the event that 
          [     *     ]is unable to supply all of the reasonably anticipated 
          requirements of the Product.  If the Second Source manufactures the 
          Product pursuant to this Article 10.2, Wyeth-Ayerst and CoCensys shall
          cooperate and assist each other to obtain, transfer or use any 
          licenses, registrations or information reasonably required to permit 
          such Second Source to manufacture the Product.
     
     10.3 EXCHANGE OF INFORMATION.  Subject to Article 17, the Parties 
          undertake to exchange and to use diligent efforts to cause Third Party
          manufacturers to exchange, on a regular basis, all data and know-how 
          relating to the manufacture of the Product.

     10.4 COMPLIANCE.  Any manufacture of the Product for sale in the 
          RoW shall be performed in full compliance with all applicable foreign
          GMP and applicable laws and regulations.  CoCensys shall be entitled 
          to audit such compliance and in particular the quality assurance 
          program for the manufacture of the Product.

11.  PROSECUTION, MAINTENANCE AND INFRINGEMENT OF INTELLECTUAL
     PROPERTY RIGHTS.

     11.1 PATENTABLE INVENTIONS.

          11.1.1    Wyeth-Ayerst shall own all Inventions made solely by its 
                    employees and agents, and all patent applications and 
                    patents claiming such Inventions.  CoCensys shall own all 
                    Inventions made solely by its employees and agents, and all
                    patent applications and patents claiming such Inventions.  
                    All Inventions made jointly by employees or agents of 
                    CoCensys and employees or agents of Wyeth-Ayerst and all 
                    patent applications and patents claiming such Inventions 
                    shall be owned jointly by CoCensys and Wyeth-Ayerst. All 
                    determinations of inventorship under this Article 11.1.1 
                    shall be in accordance with U.S. law.

          11.1.2    Wyeth-Ayerst and CoCensys shall each disclose to the other 
                    and discuss any Inventions and the desirability of filing a
                    United States patent application covering the Invention, as
                    well as any foreign counterparts.  The Party owning the 
                    Invention shall make the final decision with respect to any
                    such filings. With respect to jointly owned Inventions, the
                    Parties shall determine which Party shall file and prosecute
                    any patent applications thereon.  [     *     ] shall be 
                    responsible for expenses for preparing and prosecuting joint
                    patent applications in the RoW.


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          11.1.3    Each Party shall have the right to select patent counsel and
                    to take such other actions as are reasonably appropriate to
                    prepare, file, prosecute and maintain patent protection with
                    respect to its Inventions arising under this Article 11.1.

     11.2 PROSECUTION AND MAINTENANCE OF PATENT RIGHTS.  Each Party 
          shall be responsible for prosecuting and maintaining its own Patent 
          Rights, subject to Article 11.1.2.  With respect to the RoW, the 
          decision as to whether to prosecute and maintain Patent Rights, and in
          which countries to do so, shall be made jointly by Wyeth-Ayerst and 
          CoCensys.  To facilitate such decision-making, each Party will appoint
          a "patent coordinator", who will have the authority to make such 
          decision on behalf of such Party.  All expenses for filing, 
          prosecuting and maintaining the CoCensys Patent Rights in the RoW 
          shall be paid by [    *    ].

     11.3 PATENT EXTENSIONS.  The Party holding a Patent Right, if requested by
          and with the assistance of the other Party, shall apply in a timely 
          manner for such patent term extensions or patent restoration 
          certificates for such Patent Right as are available under similar
          legislation to the U.S. Federal Drug Price Competition and Patent 
          Term Restoration Act of 1984 (Pub. L. No. 98-417), and any amendments
          thereof or any successor acts thereto. [     *     ] expenses incurred
          in connection with such patent term extensions or patent restoration 
          certificates shall be borne [     *      ].

     11.4 COOPERATION.  Each of the Parties shall execute or have 
          executed by its appropriate employees, representatives, agents, and 
          contractors such documents as may be necessary to obtain, perfect or 
          maintain any Patent Rights filed or to be filed pursuant to this 
          Agreement, and to cooperate with the other Party so far as reasonably 
          necessary with respect to furnishing all information and data in its 
          possession reasonably necessary to obtain or maintain such Patent 
          Rights.

     11.5 INFRINGEMENT OF INTELLECTUAL PROPERTY RIGHTS.

          11.5.1

               (a)  If either Party should become aware of any infringement or 
                    threatened infringement or misappropriation, as the case 
                    may be, in the RoW of any Intellectual Property Rights of
                    the other Party, it shall promptly notify such other Party 
                    in writing.  As soon as practicable the Parties shall 
                    confer on the particulars of such infringement or 
                    misappropriation and the possible courses of  action to be 
                    taken.  The Party holding the affected Intellectual Property
                    Rights shall have the right, but not the obligation, to
                    institute, prosecute and control any 


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         legal proceedings in its own name and by its own counsel and at its 
         own expense, subject to Article 11.5.1(d), to prevent or restrain 
         such infringement, and the other Party shall have the right, 
         [     *     ] to be represented in such action by its own counsel.  
         If one Party brings any such action or proceeding, the other Party 
         hereby consents to being joined as a party plaintiff where 
         necessary and, in case of joining, such other Party agrees to give 
         the first Party reasonable assistance and authority to file and to 
         prosecute such suit, at the exercise of the Party bringing such 
         suit.

   (b)   Notwithstanding the foregoing, the Parties shall jointly determine 
         which Party shall have the primary right and responsibility (but 
         not the obligation) to institute, prosecute, and control any action 
         or proceeding with respect to infringement or misappropriation of 
         jointly owned Intellectual Property Rights in the RoW and the other 
         Party shall have the right [     *    ] to be represented by its 
         counsel.  Each Party hereby consents to the filing of any such 
         action by the other Party with respect to any jointly owned Patent 
         Rights in accordance with this Article 11.5.1(b).

   (c)   If one Party alone prosecutes an infringement or misappropriation of 
         Intellectual Property Rights, [          *          ] any damages 
         and costs recovered in any proceedings or by way of settlement 
         under Articles 11.5.1(a) and 11.5.1(b) above or Article 11.5.2 
         shall [         *          ] as applicable.

   (d)   If both Parties participate in prosecuting an infringement or 
         misappropriation of Intellectual Property Rights, the actual costs 
         and expenses of all suits brought by either Party under this 
         Article 11.5.1 shall be [          *          ].  Any remaining 
         damages shall then be [          *         ].

11.5.2   If the Party having the primary right to institute, prosecute, and 
         control such infringement or misappropriation action under Article 
         11.5.1 fails to do so within a period of one hundred twenty (120) 
         days after receiving notice of the infringement, or if that Party, 
         after initiating an action, determines to discontinue such action, 
         the other Party shall have the right to bring and control or take 
         over any such action by counsel of its own choice, and at its own 
         expense, subject to Article 11.5.1(c) unless prevented from doing 
         so by the laws of the country where the infringement or 
         misappropriation occurred or is threatened.
         

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     11.5.3   In connection with any proposed settlement in respect of any 
              infringement or threatened infringement of any Intellectual 
              Property Rights, the Party intending to settle shall notify 
              and consult with the other Party as to the terms of 
              settlement, whose written consent shall be required prior to 
              any such settlement, such consent shall not be unreasonably 
              withheld.
         
     11.5.4   In connection with any action taken by either Party against a 
              Third Party to protect or enforce any Intellectual Property 
              Rights, the other Party shall, if requested, consult with the 
              Party taking such action, and make available as witnesses its 
              employees or as evidence any materials, and/or data as are 
              reasonably necessary for the furtherance of such action.  The 
              expenses in connection with the providing of witnesses and/or 
              the making available of any materials and/or data shall be 
              [          *          ].
         
11.6 INFRINGEMENT OF THIRD PARTY PATENT RIGHTS.

     11.6.1   If Wyeth-Ayerst should be of the opinion that it cannot make, 
              import, use, market and/or sell the Product in the RoW under 
              its own Intellectual Property Rights or those licensed to it 
              by CoCensys under this Agreement without infringing a Third 
              Party's patent, it shall notify CoCensys.  Both Parties then 
              shall seek an opinion of patent counsel acceptable to both 
              Parties.  If such patent counsel concurs with Wyeth-Ayerst's 
              opinion, they shall jointly or independently endeavor to 
              secure a license from the Third Party on terms that are 
              acceptable to both Parties.

     11.6.2   If, in the opinion of patent counsel selected under Article 
              11.6.1, the Third Party patent, if litigated, would be found 
              invalid or not be infringed by the manufacture or sale of the 
              Product or if the Parties otherwise mutually agree to obtain a 
              license to such Third Party patent, the Parties shall proceed 
              in accordance with the terms of this Agreement, unless an 
              action for infringement is brought against one or both Parties.

     11.6.3   If either Party is sued for patent infringement of any Third 
              Party patents arising out of the manufacture, use, sale or 
              importation of the Product in the RoW, the Parties shall 
              promptly meet to discuss the course of action to be taken to 
              resolve or defend any such infringement litigation. Each Party 
              shall provide the other with such assistance as is reasonably 
              necessary and shall cooperate in the defense of any such 
              action.  [     *     ] of any cost/expense of defending such 
              action incurred by Wyeth-Ayerst in a given country 


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                    and any damages and/or other compensation imposed on 
                    Wyeth/Ayerst in such country may be deducted by 
                    Wyeth-Ayerst from any amounts otherwise due CoCensys 
                    under this Agreement in the form of royalties for such 
                    country, PROVIDED, HOWEVER, in no event shall royalty 
                    amounts due CoCensys for such country be reduced by more 
                    than [     *     ]in any given calendar year as a result 
                    of this sentence.
                            
12.  FORCE MAJEURE.

     Neither Party shall be liable to the other for delay or failure in the 
     performance of the obligations on its part contained in this Agreement 
     if and to the extent that such failure or delay is due to circumstances 
     beyond its control which it could not have avoided by the exercise of 
     reasonable diligence.  It shall notify the other Party promptly should 
     such circumstances arise, giving an indication of the likely extent and 
     duration thereof, and shall use all commercially reasonable efforts to 
     resume performance of its obligations as soon as practicable.

13.  TERM AND TERMINATION.

     13.1 GENERAL CONDITIONS OF EXPIRATION AND TERMINATION.

          13.1.1    Any permitted sublicenses granted hereunder shall 
                    automatically terminate or expire at the same time as 
                    this Agreement expires (insofar as they haven't already 
                    terminated), except where, and to the extent, any license 
                    granted hereunder survives expiration of this Agreement, 
                    as expressly provided in this Agreement.  Upon early 
                    termination of this Agreement for any reason, if any 
                    permitted sublicensee is not then in default under its 
                    sublicense agreement with Wyeth-Ayerst, then such 
                    sublicensee shall automatically have a license under this 
                    Agreement as a direct licensee of CoCensys, on economic 
                    terms as are set forth herein with respect to 
                    Wyeth-Ayerst and otherwise with the same rights and 
                    obligations as Wyeth-Ayerst under this Agreement.
                    
          13.1.2    The provisions of Articles 8, 9, 11, 14, 15, and 17 shall 
                    survive termination or expiration of this Agreement.

          13.1.3    Termination or expiration of this Agreement
                    shall not operate to deprive either Party of any rights 
                    or remedies either at law or in equity or to relieve 
                    either Party of any of its obligations incurred prior to 
                    the effective date of such termination or expiration.


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13.2 TERM.  Unless earlier terminated as set out in this Agreement, the term 
     of this Agreement shall end when all the respective royalty payment 
     obligations of the Parties under this Agreement have expired.

13.3 TERMINATION FOR BREACH.

     13.3.1    TERMINATION FOR BREACH.  Except as otherwise provided in this
               Section 13.3.1, either Party may terminate this Agreement for
               material breach by the other Party, which breach remains 
               uncured for [     *     ] in the case of nonpayment of any 
               amount due and [     *    ] for all other breaches, each 
               measured from the date written notice of such breach is given
               to the breaching party, or, if such breach is not susceptible 
               of cure within such [     *     ] period and the breaching 
               party uses diligent good faith efforts to cure such breach, 
               for [     *     ] after written notice to the breaching party.

     13.3.2    BREACH BY WYETH-AYERST.  If termination is due to a material 
               breach by Wyeth-Ayerst, all rights granted to Wyeth-Ayerst
               under this Agreement shall revert to CoCensys, provided that
               [          *          ] as of the date of such termination.

13.4 NO LIMIT ON REMEDIES.  Nothing herein shall exclude or limit any remedies 
     or entitlements whatsoever which the law confers to either Party in the 
     event of a breach of contractual obligations by the other Party.

13.5 UNILATERAL TERMINATION BY WYETH-AYERST.  Wyeth-Ayerst shall have the right 
     to unilaterally terminate this Agreement upon [     *     ] written 
     notice.  In the event of such termination by Wyeth-Ayerst, all 
     Wyeth-Ayerst's rights to the Licensed Compound and the Product in the 
     RoW shall revert to CoCensys.  Wyeth-Ayerst shall not be obligated to 
     make any payments under this Agreement for events which occur after the 
     effective date of such termination.  After the termination date, 
     Wyeth-Ayerst will make its relevant personnel, relevant data and other 
     resources available as are reasonably necessary to effect an orderly 
     transition of Development and commercialization of the Product for a 
     period of [     *     ] after termination.  In the event of such 
     termination, Wyeth-Ayerst shall (i) [          *          ] (ii) 
     [         *          ] and (iii) [          *          ].

13.6 AUTOMATIC TERMINATION OF AGREEMENT (NO. 1).  This Agreement shall 
     terminate automatically if Agreement (No. 1) is terminated for any 
     reason other than expiration or for material breach by CoCensys.


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14.  ASSIGNMENT.

     14.1 ASSIGNMENT TO AFFILIATES.  Either Party may assign any of its rights 
          or obligations under this Agreement in any country to any 
          Affiliates, for so long as they remain Affiliates; provided, 
          however, that such assignment shall not relieve the assigning Party 
          of its responsibilities for performance of its obligations under 
          this Agreement.
          
     14.2 OTHER PERMITTED ASSIGNMENT.  Either Party may assign its rights or 
          obligations under this Agreement in connection with a merger or 
          similar reorganization or the sale of all or substantially all of 
          its assets, [         *          ] provided, that in the event of 
          such merger, reorganization or sale, [          *          ] All 
          other assignments by any Party shall [          *         ].
          
     14.3 BINDING NATURE OF ASSIGNMENT.  This Agreement shall be binding upon 
          and inure to the benefit of the successors and permitted assigns of 
          the Parties.  Any assignment not in accordance with this Article 14 
          shall be void.
          
15.  INDEMNIFICATION.

     15.1 CROSS INDEMNIFICATION.

          15.1.1    Each Party hereby agrees to save, defend and hold the other 
                    Party and its agents and employees harmless from and 
                    against any and all suits, claims, actions, demands, 
                    liabilities, expenses and/or losses, including reasonable 
                    legal expense and attorneys' fees, brought by a Third 
                    Party or that arise in connection with any claim brought 
                    by a Third Party ("Losses") resulting directly from the 
                    manufacture, use, handling, storage, sale or other 
                    disposition of Products in the RoW to the extent such 
                    Losses result solely from (i) the negligence of the 
                    indemnifying party or breach by the indemnifying party of 
                    any provision of this Agreement, (ii) failure of the 
                    indemnifying party to manufacture or have manufactured 
                    Products (bulk or finished  form) according to cGMP or 
                    Product specifications, or (iii) marketing activities of 
                    the indemnifying party contrary to applicable 
                    governmental regulations or outside the approved labeling 
                    of the Product.
                    
          15.1.2    In the event CoCensys is seeking indemnification under 
                    Article 15.1.1, it shall inform Wyeth-Ayerst of a claim 
                    as soon as is reasonably practicable after it receives 
                    notice of the claim, shall permit Wyeth-Ayerst to assume 
                    direction and control of the defense of the claim 
                    (including the right to settle the claim solely for 
                    monetary 


                                       22.

* Confidential treatment requested

<PAGE>

                    consideration), and shall cooperate as requested (at the 
                    expense of Wyeth-Ayerst) in the defense of the claim.

          15.1.3    In the event Wyeth-Ayerst is seeking indemnification under 
                    Article 15.1.1, it shall inform CoCensys of a claim as 
                    soon as is reasonably practicable after it receives 
                    notice of the claim, shall permit CoCensys to assume 
                    direction and control of the defense of the claim 
                    (including the right to settle the claim solely for 
                    monetary consideration), and shall cooperate as requested 
                    (at the expense of CoCensys) in the defense of the claim.
                    
     15.2 INSURANCE.  Each Party further agrees to use reasonable commercial 
          efforts to obtain and maintain, during the term of this Agreement, 
          Comprehensive General Liability Insurance, including Products 
          Liability, with reputable and financially secure insurance carriers 
          or self-insurance, with limits of not less than $5,000,000 per 
          occurrence and in the aggregate to cover its indemnification 
          obligations under Articles 15.1 and 15.2.

16.  WARRANTIES AND REPRESENTATIONS.

     16.1 GENERAL.  Each Party hereby warrants to the other:

          16.1.1    that it has full power and authority to execute and deliver 
                    this Agreement and to perform the obligations on its part 
                    hereunder; and

          16.1.2    that the execution and delivery by it of this Agreement and 
                    the performance of its obligations hereunder have been 
                    duly approved by all necessary corporate action and do 
                    not require any shareholder action or approval.

          16.1.3    that, to the best of its knowledge, the manufacture, use, 
                    importation, offer for sale, or sale of CO 2-6749 will 
                    not infringe any Third Party patent in the RoW.

17.  CONFIDENTIAL INFORMATION.

     17.1 INFORMATION.  Each Party shall keep all information received from 
          the other Party (the "Information") confidential and shall not 
          disclose nor use the Information without the other Party's written 
          consent except to the extent contemplated by this Agreement. This 
          restriction shall not, however, prevent disclosure of the 
          Information if and to the extent that disclosure is required by 
          law, PROVIDED THAT the disclosing Party informs the other Party 
          without delay of any such 


                                       23.

<PAGE>

          requirement, in order to allow such other Party to object to such 
          disclosure and to seek an appropriate protective order or similar 
          protection prior to disclosure.
    
    17.2  EXCEPTIONS.  The above obligations shall not apply or shall cease to
          apply to Information which:
    
          17.2.1    is now, or hereafter becomes, through no act or failure to
                    act on the part of the receiving Party, generally known or
                    available;
    
          17.2.2    is known by the receiving Party at the time of receiving
                    such information, as evidenced by its written records;
    
          17.2.3    is hereafter furnished to the receiving Party by a Third
                    Party, as a matter of right and without restriction on
                    disclosure;
    
          17.2.4    is independently developed by or for the receiving Party
                    without any breach of this Article 17; or
    
          17.2.5    is the subject of a written permission to disclose provided
                    by the disclosing Party.
    
    17.3  PERMITTED DISCLOSURES.  Information may be disclosed to employees,
          agents, consultants, sublicensees or suppliers of the recipient Party
          or its Affiliates, but only to the extent required to accomplish the
          purposes of this Agreement and only if the recipient Party obtains
          prior agreement from its employees, agents, consultants, sublicensees
          or suppliers to whom disclosure is to be made to hold in confidence
          and not make use of such information for any purpose other than those
          permitted by this Agreement. Each Party will use at least the same
          standard of care as it uses to protect proprietary or confidential
          information of its own to ensure that such employees, agents,
          consultants, sublicensees or suppliers do not disclose or make any
          unauthorized use of the Information.
    
    17.4  DISCLOSURE OF AGREEMENT.  Neither CoCensys nor Wyeth-Ayerst shall
          release to any Third Party or publish in any way any non-public
          information with respect to the terms of this Agreement or concerning
          their cooperation without the prior written consent of the other,
          which consent will not be unreasonably withheld or delayed; provided;
          however that either Party may disclose the terms of this Agreement to
          the extent required to comply with applicable laws, including without
          limitation the rules and regulations promulgated by the Securities and
          Exchange Commission and the Party intending to disclose the terms of
          this Agreement shall provide the nondisclosing party an opportunity to
          review and comment on the intended disclosure which is reasonable
          under the circumstances.  Notwithstanding any other provision of this
          Agreement, each Party may disclose the terms of this Agreement to
          lenders, investment bankers and other financial
    
    
                                         24.
    
<PAGE>

          institutions of its choice solely for purposes of financing the
          business operations of such Party either (i) upon the written consent
          of the other Party or (ii) if the disclosing Party uses reasonable
          efforts to obtain a signed confidentiality agreement with such
          financial institution with respect to such information, upon terms
          substantially similar to those contained in this Article 17.
    
    17.5  PUBLICITY.  Subject to Section 17.4, all publicity, press releases and
          other announcements relating to this Agreement or the transaction
          contemplated hereby shall be reviewed in advance by, and shall be
          subject to the approval of, both Parties.
    
    17.6  PUBLICATION.  The Parties shall cooperate in appropriate publication
          of the results of research and development work performed pursuant to
          this Agreement, but subject to their predominating interest in
          obtaining patent protection for any patentable subject matter.  The
          determination of authorship for any paper shall be in accordance with
          accepted scientific practice.  Notwithstanding anything in this
          Article 17.6 to the contrary, all publication and presentations of the
          results of research and development work performed pursuant to this
          Agreement must be approved in advance by both Parties.
    
18.   MISCELLANEOUS.
    
    18.1  NO WAIVER OF CONTRACTUAL RIGHTS.  The failure of either Party to 
          require performance by the other Party of any of that other Party's 
          obligations hereunder shall in no manner affect the right of such
          Party to enforce the same at a later time. No waiver by any Party
          hereto of any  condition, or of the breach of any provision, term,
          representation or warranty contained in this Agreement, whether by
          conduct or otherwise, in any one or more instances, shall be deemed
          to be or construed as a further or continuing waiver of any such
          condition or breach, or of any other condition or of the breach of any
          other provision, term representation or warranty hereof.

    18.2  EXECUTION AND AMENDMENTS.

          18.2.1    Each Party shall execute and deliver all such instruments
                    and perform all such other acts as the other Party may
                    reasonably request in order to carry out the transactions
                    contemplated by this Agreement.

          18.2.2    This Agreement may not be amended or modified except by
                    written instrument signed by or on behalf of both Parties.


    18.3  SEVERABILITY.  If a court or other tribunal of competent jurisdiction
          should hold any term or provision of this agreement to be excessive,
          or invalid, void or unenforceable, the offending term or provision
          shall be deleted, and, if possible,


                                      25.
<PAGE>

          replaced by a term or provision which, so far as practicable achieves
          the legitimate aims of the Parties.

    18.4  RELATIONSHIP BETWEEN THE PARTIES.  Both Parties are independent
          contractors under this Agreement.  Nothing contained in this Agreement
          is intended nor shall be construed so as to constitute CoCensys or
          Wyeth-Ayerst as partners or joint venturers with respect to this
          Agreement.  Neither Party shall have the express or the implied right
          nor authority to assume or create any obligations on behalf of or in
          the name of the other Party, nor to bind the other Party to any other
          contract, agreement or undertaking with any Third Party.

    18.5  CORRESPONDENCE AND NOTICES.

          18.5.1    Correspondence, reports, documentation, and any other
                    communication in writing between the Parties in the course
                    of ordinary implementation of this Agreement shall be
                    delivered by hand, sent by facsimile, or by airmail to any
                    one employee appointed by the Party which is to receive such
                    written communication, or any other way as the Parties deem
                    appropriate.

          18.5.2    Extraordinary notices and communications (including but not
                    limited to notices of termination, force majeure, material
                    breach, change of address) shall be in writing and sent by
                    prepaid registered or certified air mail, or by facsimile
                    confirmed by prepaid registered or certified air mail
                    letter, and shall be deemed to have been properly served to
                    the addressee upon receipt of such written communication.

          18.5.3    In the case of CoCensys, the proper address for
                    communications and for all payments shall be:

                    CoCensys, Inc.
                    213 Technology Drive
                    Irvine, California 92618, USA
                    Attn:  Chief Executive Officer

                    and in the case of Wyeth-Ayerst, the proper address for
                    communications and for all payments shall be:

                    Wyeth-Ayerst Laboratories
                    555 Lancaster Avenue
                    St. Davids, PA  19087
                    Attn:  Senior Vice President, Global Business Development

          With a copy to:


                                      26.
<PAGE>

                    American Home Products Corporation
                    5 Giralda Farms
                    Madison, NJ  07940
                    Attn:  Senior Vice President and General Counsel

    18.6   CHOICE OF LAW.  This Agreement is subject to and governed by the
           laws of the State of Delaware, excluding its conflict of laws
           provisions.

    18.7   COUNTERPARTS.  This Agreement may be executed in one or more
           counterparts, each of which shall be an original and all of which
           shall constitute together the same document.

    18.8   APPOINTMENT OF WYETH-AYERST INTERNATIONAL, INC.  Wyeth-Ayerst hereby
           appoints Wyeth-Ayerst International Inc., a subsidiary company of
           Wyeth-Ayerst, organized and existing under the laws of the State of
           New York, U.S.A., having an office and place of business at 150
           Radnor-Chester Road, St. Davids Center, St. Davids, Pennsylvania
           19087, U.S.A., to administer as agent for Wyeth-Ayerst all the rights
           and obligations of Wyeth-Ayerst in respect of this Agreement,
           including, without limitation, the accounting of all royalties and
           other sums or payments due CoCensys hereunder, and the transmittal
           and receipt of all notices, reports, statements or other records
           relating to such royalties and the manufacture and sale of the
           Product. By its execution hereinbelow, Wyeth-Ayerst International
           Inc. accepts the designation and appointment set forth hereinabove.

This Agreement together with its Exhibits and further agreements mentioned
herein and Agreement No. 1 constitutes the entire agreement of the Parties with
respect to the subject matter hereof as of its date, and supersedes all prior
agreements, understandings, representations and proposals, written or oral,
relating thereto.

AMERICAN HOME PRODUCTS CORPORATION             COCENSYS, INC.



- ----------------------------------             ---------------------------------
Name                                           Name
Title                                          Title            


WYETH-AYERST INTERNATIONAL, INC.


- ----------------------------------
Name
Title     


                                     27.

<PAGE>

                                    EXHIBIT A
                                 
                       BACK-UP COMPOUND CANDIDATE CRITERIA


                Criterion for IND-Tracking     Activities Required
                --------------------------     -------------------

                             [          *          ]
                

* Confidential treatment requested

<PAGE>




                                   EXHIBIT B
                                 
                                 
                                 
                            [          *          ]
                                 

















                            [          *          ]

* Confidential treatment requested


<PAGE>


                                   EXHIBIT C
                                 
                            COCENSYS PATENT RIGHTS
                                 
                                 
                                 
 US   ISSUE DATE     EXPIRATION DATE     CORRESPONDING FOREIGN APPLICATIONS
- ------------------------------------------------------------------------------


                            [          *          ]

* Confidential treatment requested


<PAGE>




                                   EXHIBIT D
                                 
                                 
                       DEFINITION OF FULLY BURDENED COST
                                 

The following expenses are manufacturing expenses which are prepared in
accordance with generally accepted accounting principles consistently applied.

THE FOLLOWING EXPENSES ARE INCLUDED IN MANUFACTURING COSTS:


                           [          *          ]
      

* Confidential treatment requested


<PAGE>


                                 EXHIBIT E
                                 
                         WYETH-AYERST PATENT RIGHTS
                                 
                                 
                                 
                                 
                                 
                           [          *          ]

* Confidential treatment requested




<TABLE> <S> <C>

<PAGE>
<ARTICLE> 5
<MULTIPLIER> 1,000
       
<S>                             <C>
<PERIOD-TYPE>                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1997
<PERIOD-START>                             JAN-01-1997
<PERIOD-END>                               JUN-30-1997
<CASH>                                           2,192
<SECURITIES>                                    15,180
<RECEIVABLES>                                      657
<ALLOWANCES>                                         0
<INVENTORY>                                          0
<CURRENT-ASSETS>                                18,839
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<DEPRECIATION>                                   3,565
<TOTAL-ASSETS>                                  21,638
<CURRENT-LIABILITIES>                            4,302
<BONDS>                                            227
                                0
                                     12,000
<COMMON>                                        96,076
<OTHER-SE>                                    (91,005)
<TOTAL-LIABILITY-AND-EQUITY>                    21,638
<SALES>                                              0
<TOTAL-REVENUES>                                 9,257
<CGS>                                                0
<TOTAL-COSTS>                                        0
<OTHER-EXPENSES>                                     0
<LOSS-PROVISION>                                     0
<INTEREST-EXPENSE>                                  51
<INCOME-PRETAX>                                (7,306)
<INCOME-TAX>                                         0
<INCOME-CONTINUING>                            (7,306)
<DISCONTINUED>                                       0
<EXTRAORDINARY>                                      0
<CHANGES>                                            0
<NET-INCOME>                                   (7,306)
<EPS-PRIMARY>                                    (.33)
<EPS-DILUTED>                                    (.33)
        

</TABLE>


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