ELAN CORP PLC
SC 13D, 1999-01-06
PHARMACEUTICAL PREPARATIONS
Previous: COVER ALL TECHNOLOGIES INC, 424B3, 1999-01-06
Next: VARIFLEX, 497, 1999-01-06



                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D
                    Under the Securities Exchange Act of 1934

                       LIGAND PHARMACEUTICALS INCORPORATED
- -------------------------------------------------------------------------------
                                (Name of Issuer)

                         Common Stock, $0.001 par value
- -------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                   53220K 20 7
- -------------------------------------------------------------------------------
                                 (CUSIP Number)

                                William F. Daniel
                              Elan Corporation, plc
                                  Lincoln House
                                  Lincoln Place
                                Dublin 2, Ireland
                                (353) 1-709-4000

                                    Copy to:
                            Lisabeth F. Murphy, Esq.
                           Athena Neurosciences, Inc.
                              800 Gateway Boulevard
                      South San Francisco, California 94080
                                 (650) 877-0900
                            Telecopy: (650) 875-3620
- -------------------------------------------------------------------------------
            (Name, Address and Telephone Number of Person Authorized
                     to Receive Notices and Communications)

                                November 9, 1998
- -------------------------------------------------------------------------------
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
schedule because of ss.ss. 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the
following box / /.

NOTE: Schedules filed in paper format shall include a signed original and five
copies of the schedule, including all exhibits. See ss. 240.13d-7(b) for other
parties to whom copies are to be sent.

*The remainder of this cover page shall be filled out for a reporting person's
initial filing on this form with respect to the subject class of securities, and
for any subsequent amendment containing information which would alter
disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed
to be "filed" for the purpose of Section 18 of the Securities Exchange Act of
1934 ("Act") or otherwise subject to the liabilities of that section of the Act
but shall be subject to all other provisions of the Act (however, see the
Notes).



<PAGE>


                                  SCHEDULE 13D

- -------------------------------------------------------------------------------

CUSIP No. 53220K 20 7

- -------------------------------------------------------------------------------
1         NAME OF REPORTING PERSON
          I.R.S. IDENTIFICATION NO. OF ABOVE PERSON (ENTITIES
             ONLY)
          Elan Corporation, plc
          I.R.S. Employer Identification No.: NA
- -------------------------------------------------------------------------------
2         CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP    (a)  / /
                                                              (b) / /
          N/A
- -------------------------------------------------------------------------------
3         SEC USE ONLY

- -------------------------------------------------------------------------------
4         SOURCE OF FUNDS

- -------------------------------------------------------------------------------
          WC
- -------------------------------------------------------------------------------
5         CHECK IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
          PURSUANT TO ITEMS 2(d) or 2(e)  N/A

- -------------------------------------------------------------------------------
6         CITIZENSHIP OR PLACE OF ORGANIZATION

          Ireland
- -------------------------------------------------------------------------------
                             7         SOLE VOTING POWER

        NUMBER OF                      5,041,160
         SHARES              __________________________________________________
       BENEFICIALLY          8         SHARED VOTING POWER
         OWNED BY
           EACH                        None
        REPORTING            __________________________________________________
       PERSON WITH           9         SOLE DISPOSITIVE POWER

                                       5,041,160
                             --------------------------------------------------
                             10        SHARED DISPOSITIVE POWER

                                       None
- -------------------------------------------------------------------------------
11        AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON

            5,041,160
- -------------------------------------------------------------------------------
12        CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
          CERTAIN SHARES                                                  / /
- -------------------------------------------------------------------------------
13        PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)

            11.8 (based upon outstanding common stock as of October 31,
            1998)
- -------------------------------------------------------------------------------
14        TYPE OF REPORTING PERSON

          CO
- -------------------------------------------------------------------------------


<PAGE>



Item 1.  Security and Issuer.

     This statement relates to the Common Stock, $0.001 par value ("Common
Stock"), of Ligand Pharmaceuticals Incorporated (the "Issuer"), a Delaware
corporation, whose principal executive offices are located at 10275 Science
Center Drive, San Diego, California 92121.

Item 2.  Identity and Background.

     This Form 13-D is filed on behalf of Elan Corporation, plc ("Elan"), a
public limited company organized and existing under the laws of Ireland.

     Elan is a leading worldwide specialty pharmaceutical company. The principal
business and office address of Elan is: Lincoln House, Lincoln Place, Dublin 2,
Ireland. Information as to the name, business address, present principal
occupation or employment and organization in which such occupation or employment
is conducted and citizenship of each director, executive officer and controlling
person of Elan is annexed hereto as Schedule A, and is incorporated herein by
reference.

     Neither Elan nor, to the best of Elan's knowledge, any of the persons
listed on Schedule A hereto, has during the last five years (i) been convicted
in a criminal proceeding (excluding traffic violations or similar misdemeanors)
or (ii) been a party to a civil proceeding of a judicial or administrative body
of competent jurisdiction and as a result of such proceeding was or is subject
to a judgment, decree or final order enjoining future violations of, or
prohibiting or mandating activities subject to, federal or state securities laws
or finding any violation with respect to such laws.

Item 3.  Sources and Amount of Funds or Other Consideration.

     Pursuant to a Stock Purchase Agreement, dated as of September 30, 1998, by
and between the Issuer and Elan International Services, Ltd., a wholly-owned
subsidiary of Elan ("EIS"), EIS acquired 1,278,970 shares of Common Stock (the
"First Shares") on September 30, 1998 for an aggregate cash purchase price of
$14,900,000.50. In addition, pursuant to a Securities Purchase Agreement, dated
as of November 6, 1998, by and among the Issuer, EIS and Elan (the "Purchase
Agreement") (a copy of which is filed as an exhibit to this Schedule 13D), on
November 9, 1998, EIS acquired (i) an additional 437,768 shares of Common Stock
(the "Second Shares") for an aggregate cash purchase price of $5,099,997.20 and
(ii) zero coupon convertible senior notes due 2008 of the Issuer with an 8.0%
per annum yield to maturity (the "Notes") and an issue price of $30,000,000 (the
"Initial Notes"). The issue price plus all accrued interest on the Initial Notes
is convertible into Common Stock of the Issuer at any time at the option of EIS
at a conversion price of $14.00 per share. Finally, pursuant to a Development,
License and Supply Agreement, dated as of November 6, 1998 (the "License
Agreement") (a copy of which is filed as an exhibit to this Schedule 13D), by
and between the Issuer and Elan, on November 9, 1998, Elan acquired (i) 429,185
shares of Common Stock of the Issuer (the "Third Shares") and (ii) Notes of the
Issuer (the 

                                      -1-
<PAGE>

"Additional Notes" and, together with the First Shares, the Second Shares, the
Third Shares and the Initial Notes, the "Securities") with an issue price of
$10,000,000, in each case, in lieu of certain cash license fees payable by the
Issuer to Elan pursuant to the License Agreement. The issue price plus all
accrued interest on the Additional Notes is convertible into Common Stock of the
Issuer at any time at the option of Elan at a conversion price of $14.00 per
share. The First Shares, the Second Shares and the Initial Notes were purchased
by EIS with general corporate funds. None of such funds were borrowed.

Item 4.  Purpose of Transaction.

     Elan acquired the Securities for the purpose of making an investment in the
Issuer and in connection with the execution of the License Agreement.

     Each of the Initial Notes and the Additional Notes are convertible into
Common Stock of the Issuer at the option of EIS and Elan, respectively, at a
conversion price of $14.00 per share. The number of shares of Common Stock into
which the Initial Notes and the Additional Notes may be converted is based upon
the quotient obtained by dividing the issue price thereof plus all accrued
interest thereon to the conversion date by $14.00.

     The Issuer has granted to Elan and EIS certain registration rights for the
First Shares, the Second Shares and the Third Shares and the shares of Common
Stock issuable upon conversion of the Initial Notes and the Additional Notes.

     Pursuant to the Purchase Agreement, subject to certain conditions, at the
Issuer's request, EIS will purchase additional Notes with an issue price of up
to $70,000,000 on or before December 31, 1999. Such Notes will be convertible
into Common Stock of the Issuer at the option of EIS at a conversion price equal
to the average of the closing prices of the Common Stock for the 20 consecutive
trading days immediately preceding the issue date of such Notes, plus a premium;
provided that the conversion price of such Notes will not be less than $14.00 or
greater than $20.00 per share. In addition, pursuant to the License Agreement,
Elan may, at the option of the Issuer, acquire additional shares of Common Stock
in lieu of certain cash fees which may become payable by the Issuer to Elan
pursuant thereto upon the achievement of certain milestones.

     Other than as set forth above, neither Elan nor EIS has any present plans
or intentions which would result in or relate to any of the transactions
described in subparagraphs (a) through (j) of Item 4 of Schedule 13D.

     The foregoing descriptions of the Purchase Agreement and the License
Agreement do not purport to be complete and are qualified in their entirety by
reference to the full text thereof, copies of which are filed herewith as
Exhibits 1 and 2 and are incorporated herein by reference.


                                      -2-
<PAGE>

Item 5. Interest in Securities of the Issuer.

     (a) Elan is the beneficial owner of 5,041,160 shares of Common Stock, or
approximately 11.8%, of the outstanding shares of Common Stock (based upon the
outstanding shares of Common Stock as of October 31, 1998 and the shares of
Common Stock issuable upon conversion of the Initial Notes and the Additional
Notes). To the best knowledge of Elan, no other person named in Item 2 above
beneficially owns any shares of Common Stock of the Issuer.

     (b) Elan has sole power to vote and sole authority to dispose or direct the
disposition of all shares of Common Stock reported by this Schedule 13D.

     (c) See Items 3 and 4 above.

     (d) N/A

     (e) N/A

Item 6.  Contracts, Arrangements, Understandings
         or Relationships with Respect to
         Securities of the Issuer.                                

     There are no contracts, arrangements, understandings or relationships
described in Item 6 of Schedule 13D.

Item 7.  Items to be Filed as Exhibits.

Exhibit 1*   Securities Purchase Agreement, dated as of November 6, 1998, by 
             and among Elan, EIS and the Issuer.

Exhibit 2*   Development, License and Supply Agreement, dated as of 
             November 9, 1998, by and between Elan and the Issuer.


- ----------

*    Certain confidential portions of these Exhibits were omitted by means of
     marking such portions with an asterisk (the "Mark"). These Exhibits have
     been filed separately with the Secretary of the Commission without the Mark
     pursuant to Elan's Request for Confidential Treatment under Rule 24b-2 of
     the Securities Exchange Act of 1934.


                                      -3-
<PAGE>



                                    Signature


     The undersigned certifies that, after reasonable inquiry and to the best of
its knowledge and belief, the information set forth in this statement is true,
complete and correct.

January 6, 1999

                                     ELAN CORPORATION, PLC


                                     By: /s/ William F. Daniel
                                         -----------------------------------
                                         Name: William F. Daniel
                                         Title: Group Financial Controller



                                      -4-
<PAGE>



                                   Schedule A

     The (a) name, (b) business address, (c) principal occupation or employment
and the organization in which such occupation or employment is conducted and (d)
citizenship of each director (other than Messrs. Armen, Balog, Boushel, Crowley,
Gillespie, McIntyre, McLaughlin, Selkoe and Thornburgh) and officer of Elan
Corporation, plc ("Elan") are set forth in the following table:

1.       (a)      Donal J. Geaney
         (b)      Lincoln House, Lincoln Place, Dublin 2, Ireland
         (c)      Director, Chairman of the Board and Chief Executive
                  Officer of Elan
         (d)      Ireland

2.       (a)      John Groom
         (b)      Lincoln House, Lincoln Place, Dublin 2, Ireland
         (c)      Director, President and Chief Operating Officer of Elan
         (d)      United Kingdom

3.       (a)      Thomas G. Lynch
         (b)      Lincoln House, Lincoln Place, Dublin 2, Ireland
         (c)      Director, Executive Vice President and Chief Financial
                  Officer of Elan
         (d)      United Kingdom

4.       (a)      William F. Daniel
         (b)      Lincoln House, Lincoln Place, Dublin 2, Ireland
         (c)      Group Vice President, Finance and Group Controller of Elan
         (d)      Ireland

5.       (a)      Lisabeth F. Murphy
         (b)      800 Gateway Boulevard, South San Francisco, CA 94080
         (c)      Vice President and General Counsel of Elan
         (d)      United States

6.       (a)      Mark A. Pearson
         (b)      Lincoln House, Lincoln Place, Dublin 2, Ireland
         (c)      Partner, McCann FitzGerald; Secretary of Elan
         (d)      Ireland

         The (a) name, (b) business address, (c) principal occupation or
employment and the organization in which such occupation or employment is
conducted and (d) citizenship of each director (other than Messrs. Geaney,
Groom, and Lynch) are set forth in the following table:

1.       (a)      Garo H. Armen, Ph.D.
         (b)      630 Fifth Avenue, Suite 2167, New York, New York  10111
         (c)      Managing General Partner, Armen Partners, L.P.; Chairman of
                  the Board and Chief Executive Officer of Antigenics, LLC
         (d)      United States

                                      A-1
<PAGE>

2.       (a)      James Balog
         (b)      c/o Elan Corporation, plc, Lincoln House, Lincoln Place,
                  Dublin 2, Ireland
         (c)      Retired
         (d)      United States

3.       (a)      Brendan E. Boushel
         (b)      9 Upper Mount Street, Dublin 2, Ireland
         (c)      Retired
         (d)      Ireland

4.       (a)      Laurence G. Crowley
         (b)      c/o Elan Corporation, plc, Lincoln House, Lincoln Place,
                  Dublin 2, Ireland
         (c)      Executive Chairman, Michael Smurfit Graduate School of 
                  Business of University College Dublin
         (d)      Ireland

5.       (a)      Alan R. Gillespie, Ph.D.
         (b)      c/o Elan Corporation, plc, Lincoln House, Lincoln Place,
                  Dublin 2, Ireland
         (c)      Managing Director, Goldman Sachs International
         (d)      United Kingdom

6.       (a)      Kevin McIntyre, M.D.
         (b)      c/o Elan Corporation, plc, Lincoln House, Lincoln Place,
                  Dublin 2, Ireland
         (c)      Associate Clinical Professor of Medicine at Harvard 
                  Medical School
         (d)      United States

7.       (a)      Kyran McLaughlin
         (b)      Davy House, 49 Dawson Street, Dublin 2, Ireland
         (c)      Joint Chief Executive, Davy Stockbrokers
         (d)      Ireland

8.       (a)      Dennis J. Selkoe, M.D.
         (b)      c/o Elan Corporation, plc, Lincoln House, Lincoln Place,
                  Dublin 2, Ireland
         (c)      Professor of Neurology and Neuroscience at Harvard Medical
                  School
         (d)      United States



                                      A-2
<PAGE>

9.       (a)      Richard L. Thornburgh
         (b)      c/o Elan Corporation, plc, Lincoln House, Lincoln Place,
                  Dublin 2, Ireland
         (C)      Counsel to the law firm of Kirkpatrick & Lockhart LLP
         (d)      United States

10.      (a)      Kieran McGowan
         (b)      c/o Elan Corporation, plc, Lincoln House, Lincoln Place,
                  Dublin 2, Ireland
         (c)      Retired
         (d)      Ireland



                                      A-3
<PAGE>



                                  Exhibit Index

Exhibit No.          Exhibit

1*          Securities Purchase Agreement, dated
            as of November 6, 1998, by and among
            Elan Corporation, plc and Ligand
            Pharmaceuticals Incorporated.

2*          Development, License and Supply Agreement, dated as of November 9,
            1998, by and between Elan Corporation, plc and Ligand Pharmaceuti-
            cals Incorporated.







- ----------

*    Certain confidential portions of these Exhibits were omitted by means of
     marking such portions with an asterisk (the "Mark"). These Exhibits have
     been filed separately with the Secretary of the Commission without the Mark
     pursuant to Elan's Request for Confidential Treatment under Rule 24b-2 of
     the Securities Exchange Act of 1934.



                                                                       Exhibit 1


                        CONFIDENTIAL TREATMENT REQUESTED



                          SECURITIES PURCHASE AGREEMENT


     SECURITIES PURCHASE AGREEMENT (the "Agreement"), dated as of November 6,
1998, by and among Ligand Pharmaceuticals Incorporated, a Delaware corporation
(the "Company"), Elan International Services, Ltd., a Bermuda corporation (the
"Purchaser"), and Elan Corporation, plc, a public limited company organized
under the laws of Ireland ("Elan").

                                    RECITALS

     WHEREAS, the Company, the Purchaser and Elan have entered into a binding
letter of intent, dated as of September 28, 1998 (the "Letter of Intent");

     WHEREAS, pursuant to the Letter of Intent, the Purchaser has agreed to
purchase from the Company shares of the Company's common stock, par value $0.001
per share (the "Common Stock"), and Zero Coupon Convertible Senior Notes due
2008 (the "Notes") of the Company, in each case, on the terms and subject to the
conditions set forth in this Agreement.

     NOW, THEREFORE, in consideration of the mutual covenants and agreements set
forth herein and for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto agree as
follows:

                                    AGREEMENT


     SECTION 1. Purchase and Sale of Common Stock and Notes.

     (a) Shares and Initial Notes. On the basis of the representations,
warranties, agreements and covenants herein contained and subject to the terms
and conditions herein set forth, at the Initial Closing (as defined in Section
2(a)) the Company shall sell to the Purchaser, and the Purchaser shall purchase
from the Company, (i) 437,768 shares of Common Stock (the "Shares") at a
purchase price of $11.65 per share (the "Share Purchase Price"), (ii) Notes (the

<PAGE>
                                      -2-


"Initial Notes") hav-ing an issue price of $30,000,000 (the "Initial Note Issue
Price") and the Initial Note Conversion Price (as defined in Section 12(a)), to
be issued in the form of the promissory note attached hereto as Exhibit A and
(iii) Notes (the "License Notes") having an issue price of $10,000,000 (the
"License Note Issue Price") and the License Note Conversion Price (as defined in
Section 12(b)), to be issued in the form of the promissory note attached hereto
as Exhibit A and in lieu of the payment by the Company to Elan of $10,000,000 in
cash pursuant to clause 10.1.1(2) of the License Agreement (as defined in
Section 6(f)).

     (b) Additional Notes. On the basis of the representations, warranties,
agreements and covenants herein contained and subject to the terms and
conditions herein set forth, the Company may, upon [ * * * ] on or prior to
December 31, 1999 and upon not less than 60 days' prior written notice (the
"Purchase Request"), request that the Purchaser purchase from the Company
additional Notes (the "Additional Notes" and, together with the Initial Notes
and the License Notes, the "Securities"), having an aggregate issue price of not
more than $70,000,000 (the aggregate issue price of the Additional Notes to be
issued and sold on each such occasion being referred to herein as the
"Additional Note Issue Price") and having the Additional Note Conversion Price
(as defined in Section 12(c)), to be issued in the form of the promissory note
attached hereto as Exhibit A; provided, however, that the gross proceeds to be
received by the Company as a result of the issuance and sale of such Additional
Notes shall be used solely to, without duplication, (i) make all remaining
milestone payments, if any, due and payable to the stockholders, creditors and
other obligees of Seragen, Inc. ("Seragen"), pursuant to and in accordance with
the terms of that certain Agreement and Plan of Reorganization, dated as of May
11, 1998, by and among Seragen, the Company and Knight Acquisition Corp., as in
effect on the date of this Agreement, or as amended with the Purchaser's written
consent (the "Seragen Payments"), (ii) pay the purchase price for the assets of
Marathon Biopharmaceuticals, LLC ("Marathon"), pursuant to and in accordance
with the terms of that certain Option and Asset Purchase Agreement, dated as of
May 11, 1998, by and among the Company, Marathon, 520 Commonwealth Avenue Real
Estate Corp. and 660 Corporation, as in effect on the date of this Agreement, or
as amended with the Purchaser's written consent (the "Marathon Payment"), and
(iii) otherwise finance the development of the Company's business. Each Purchase
Request shall set forth (i) the proposed closing date of such purchase and sale
of Additional Notes, which shall be a date at least 60 days but not more than
180 


<PAGE>
                                      -3-


days prior to such Additional Closing Date (each such date, an "Additional
Closing Date"), (ii) the Additional Note Issue Price of the Additional Notes
proposed to be issued and sold by the Company on such Additional Closing Date
and (iii) a description in reasonable detail of the transaction or transactions
pursuant to which the Company proposes to utilize the gross proceeds to be
received by the Company from such proposed issuance and sale of Additional
Notes, which description shall be accompanied by all documents and agreements
entered into or proposed to be entered into in connection with such transaction
or transactions, to the extent such documents or any preliminary drafts thereof
are available at the time such Purchase Request is provided by the Company.

     (c) License Shares. On the basis of the representations, warranties,
agreements and covenants herein contained and subject to the terms and
conditions herein set forth, pursuant to the License Agreement, the Company may,
at its option, issue to Elan shares of Common Stock (the "License Shares") in
lieu of making cash payments thereunder (each such issuance, a "License Share
Issuance") at the times set forth in, and in accordance with the terms of,
clauses 10.1.1(1), (3) and (4) of the License Agreement.


     SECTION 2. Closings.

     (a) Initial Closing. The closing of the sale and purchase of each of the
Shares, the Initial Notes, the License Notes and the License Shares to be issued
under clause 10.1.1(1) of the License Agreement (the "Initial Closing") shall
take place at the offices of Cahill Gordon & Reindel, 80 Pine Street, New York,
NY 10005, at 10:00 AM, New York City time, on November 9, 1998, or such other
time and place as the Company and the Purchaser may agree (the "Initial Closing
Date"). At the Initial Closing, the Company shall deliver to the Purchaser (i) a
certificate or certificates, registered in the name of the Purchaser,
representing the Shares, against payment of the Share Purchase Price, (ii) one
or more promissory notes in the form attached hereto as Exhibit A, registered in
the name of the Purchaser, representing the Initial Notes, against payment of
the Initial Note Issue Price and (iii) one or more promissory notes in the form
attached hereto as Exhibit A, registered in the name of the Purchaser,
representing the License Notes.

     (b) Additional Closings. The closing of each purchase and sale of
Additional Notes (each such closing, an "Additional Closing") shall take place
at the offices of Ca-


<PAGE>
                                      -4-


hill, Gordon & Reindel, 80 Pine Street, New York, NY 10005, at 10:00 AM, New
York City time, on the Additional Closing Date set forth in the Purchase Notice
delivered to the Purchaser by the Company in accordance with Section 1(b), or
such other time and place as the Company and the Purchaser may agree. At each
Additional Closing, the Company shall deliver to the Purchaser one or more
promissory notes in the form attached hereto as Exhibit A, registered in the
name of the Purchaser and/or in the name of one or more of its Affiliates (as
defined in Section 14(a)) (subject to compliance with Regulation S under the
Securities Act of 1933, as amended (the "Securities Act")) and in such
denomination or denominations as the Purchaser may direct in writing,
representing such Additional Notes, against payment of the Additional Note Issue
Price.

     (c) License Share Issuances. Each License Share Issuance shall take place
at the offices of Cahill Gordon & Reindel, 80 Pine Street, New York, NY 10005,
at 10:00 AM, New York City time, on the applicable dates set forth in clauses
10.1.1(1), (3) and (4) of the License Agreement, or such other time and place as
the Company and Elan may agree (each such date, a "License Share Issuance
Date"). At each such License Share Issuance, the Company shall deliver to Elan a
certificate or certificates, registered in the name of Elan and/or in the name
of one or more of its Affiliates, (subject to compliance with Regulation S under
the Securities Act) as Elan may direct in writing, representing the License
Shares to be issued pursuant to and in accordance with the License Agreement.

     (d) Payments. Each payment required to be made by the Purchaser to the
Company pursuant to this Section 2 shall be made by wire transfer in immediately
available funds to an account designated in writing by the Company


     SECTION 3. Representations of the Company. Except as otherwise set forth in
the Schedule of Exceptions attached hereto, the Company represents and warrants
to and agrees with the Purchaser as follows:

          (a) Each of the Company and the Subsidiaries (as defined in paragraph
     (f) of this Section 3) is duly incorporated, validly existing and in good
     standing under the laws of its jurisdiction of organization and has all
     requisite corporate power and authority to own its properties and conduct
     its business as now being conducted. Each of the Company and the
     Subsidiaries is duly qualified to do business as a foreign corporation and
     is in good standing in all other jurisdictions where the ownership or
     leasing 


<PAGE>
                                      -5-


     of its properties or the conduct of its business requires such
     qualification, except where the failure to be so qualified would not,
     individually or in the aggregate, have a material adverse effect on the
     business, assets, liabilities (contingent or otherwise), operations,
     condition (financial or otherwise), solvency, properties, prospects or
     material agreements of the Company and its Subsidiaries, taken as a whole
     (any such event, a "Material Adverse Effect").

          (b) The Company has all requisite corporate power and authority to
     execute, deliver and perform each of its obligations under the Initial
     Notes and the License Notes. The Initial Notes and the License Notes have
     each been duly and validly authorized by the Company and, when executed by
     the Company and delivered to the Purchaser in accordance with the terms of
     this Agreement, will constitute valid and legally binding obligations of
     the Company, enforceable against the Company in accordance with their
     terms, except that the enforcement thereof may be subject to (i)
     bankruptcy, insolvency, reorganization, moratorium or other similar laws
     now or hereafter in effect relating to creditors' rights generally and (ii)
     general principles of equity and the discretion of the court before which
     any proceeding therefor may be brought.

          (c) Other than any stockholder approval that may be required by law,
     the Company has all requisite corporate power and authority to execute,
     deliver and perform each of its obligations under the Additional Notes. The
     Additional Notes, if and when issued, will have been duly and validly
     authorized by the Company and, when executed by the Company and delivered
     to the Purchaser in accordance with the terms of this Agreement, will
     constitute valid and legally binding obligations of the Company,
     enforceable against the Company in accordance with their terms, except that
     the enforcement thereof may be subject to (i) bankruptcy, insolvency,
     reorganization, moratorium or other similar laws now or hereafter in effect
     relating to creditors' rights generally and (ii) general principles of
     equity and the discretion of the court before which any proceeding therefor
     may be brought.

          (d) The Company has all requisite corporate power and authority to
     execute, deliver and perform each of its obligations under this Agreement.
     This Agreement has been duly and validly authorized, executed and delivered
     by the Company and constitutes a valid and legally binding agree-


<PAGE>
                                      -6-


     ment of the Company, enforceable against the Company in accordance with its
     terms, except that the enforcement hereof may be subject to (i) bankruptcy,
     insolvency, reorganization, moratorium or other similar laws now or
     hereafter in effect relating to creditors' rights generally and (ii)
     general principles of equity and the discretion of the court before which
     any proceeding therefor may be brought.

          (e) The Company has all requisite corporate power and authority to
     execute, deliver and perform its obligations under the Registration Rights
     Agreement (as defined in Section 6(d) hereof). The Registration Rights
     Agreement has been duly and validly authorized by the Company and, when
     executed and delivered by the Company, will constitute a valid and legally
     binding agreement of the Company, enforceable against the Company in
     accordance with its terms, except that (A) the enforcement thereof may be
     subject to (i) bankruptcy, insolvency, reorganization, moratorium or other
     similar laws now or hereafter in effect relating to creditors' rights
     generally and (ii) general principles of equity and the discretion of the
     court before which any proceeding therefor may be brought and (B) any
     rights to indemnity or contribution thereunder may be limited by federal
     and state securities laws and public policy considerations.

          (f) The authorized, issued and outstanding capitalization of the
     Company as of the date hereof consists of: (i) 80,000,000 shares of Common
     Stock, of which 42,526,245 shares were issued and outstanding as of
     September 30, 1998, and (ii) 5,000,000 shares of convertible preferred
     stock (80,000 shares of which have been designated as "Series A
     Participating Preferred Stock"), of which no shares are issued and
     outstanding as of the date of this Agreement; all of the subsidiaries of
     the Company are listed on Schedule 3(f)(i) hereto (each, a "Subsidiary" and
     collectively, the "Subsidiaries"); all of the outstanding shares of capital
     stock of the Company and the Subsidiaries have been duly authorized and
     validly issued, are fully paid and nonassessable and were not issued in
     violation of any preemptive or similar rights; all of the outstanding
     shares of capital stock of the Subsidiaries are owned, directly or
     indirectly, by the Company, free and clear of all liens, encumbrances,
     equities and claims or restrictions on transferability (other than those
     imposed by the Securities Act and the securities or "Blue Sky" laws of
     certain jurisdictions) or voting; except for 


<PAGE>
                                      -7-


     the Securities and except as described in the SEC Reports (as defined in
     paragraph (m) of this Section 3) or as otherwise set forth on Schedule
     3(f)(ii) hereto, there are no (i) options, warrants or other rights to
     purchase, (ii) agreements or other obligations to issue or (iii) other
     rights to convert any obligation into or exchange any securities for,
     shares of capital stock of or ownership interests in the Company or any of
     the Subsidiaries; except for the Subsidiaries, the Company does not own,
     directly or indirectly, any shares of capital stock or any other equity or
     long-term debt securities or have any equity interest in any firm,
     partnership, joint venture or other entity.

          (g) The Shares, when issued, sold and delivered to the Purchaser at
     the Initial Closing against payment therefor in accordance with the terms
     of this Agreement, will be duly and validly issued, fully paid and
     nonassessable, will not be issued in violation of any preemptive or similar
     rights and will be free of any liens, encumbrances or restrictions on
     transfer other than those imposed by the Securities Act and applicable
     state securities or "Blue Sky" laws.

          (h) The License Shares, if and when issued and delivered to Elan in
     accordance with the terms of this Agreement and the License Agreement, will
     be duly and validly issued, fully paid and nonassessable, will not be
     issued in violation of any preemptive or similar rights and will be free of
     any liens, encumbrances or restrictions on transfer other than those
     imposed by the Securities Act and applicable state securities or "Blue Sky"
     laws.

          (i) The shares of Common Stock issuable upon conversion of the Initial
     Notes and the License Notes have been, and, upon the issuance of any
     Additional Notes, the shares of Common Stock issuable upon conversion of
     such Additional Notes will be, reserved for issuance upon such conversion
     and, if and when issued upon such conversion, will be duly and validly
     issued, fully paid and nonassessable, will not be issued in violation of
     any preemptive or similar rights and will be free of any liens,
     encumbrances or restrictions on transfer other than those imposed by the
     Securities Act and applicable state securities or "Blue Sky" laws. The
     shares of Common Stock issuable upon conversion of the Securities are
     referred to herein as the "Conversion Shares."


<PAGE>
                                      -8-


          (j) No consent, approval, authorization or order of any court or
     governmental agency or body or third party is required for the issuance and
     sale by the Company of the Shares, the Conversion Shares, the License
     Shares or the Securities or the consummation by the Company of the other
     transactions contemplated hereby or by the Registration Rights Agreement
     and, in the case of the Additional Notes and the License Shares, no such
     consent, approval, authorization or order will be required upon any
     issuance and sale thereof by the Company, except that no representation or
     warranty is made with respect to filings required by the Hart-Scott-Rodino
     Antitrust Improvements Act of 1976, as amended (the "HSR Act"), in
     connection with the issuance of the License Shares or upon conversion of
     the Securities. None of the Company or the Subsidiaries is (i) in violation
     of its certificate of incorporation or bylaws, (ii) in breach or violation
     of any statute, judgment, decree, order, rule or regulation applicable to
     it or any of its properties or assets, except for any such breach or
     violation which would not, individually or in the aggregate, have a
     Material Adverse Effect, or (iii) in breach of or default under (nor has
     any event occurred which, with notice or passage of time or both, would
     constitute a default under) or in violation of any of the terms or
     provisions of any indenture, mortgage, deed of trust, loan agreement, note,
     lease, license, franchise agreement, permit, certificate, contract or other
     agreement or instrument to which any of them is a party or to which any of
     them or their respective properties or assets is subject (collectively,
     "Contracts"), except for any such breach, default, violation or event which
     would not, individually or in the aggregate, have a Material Adverse
     Effect.

          (k) None of the Company, the Subsidiaries, any of their respective
     Affiliates (as defined in Rule 501(b) of Regulation D under the Securities
     Act) or any person acting on its or their behalf has engaged in any
     directed selling efforts (as that term is defined in Regulation S under the
     Securities Act ("Regulation S")) with respect to the Shares, the Securities
     or the License Shares; the Company, the Subsidiaries and their respective
     Affiliates (as defined in Rule 501(b) of Regulation D under the Securities
     Act) and any person acting on its or their behalf have complied and will
     comply with the offering restrictions requirement of Regulation S.


<PAGE>
                                      -9-


          (l) The execution, delivery and performance by the Company of this
     Agreement and the Registration Rights Agreement and the consummation by the
     Company of the transactions contemplated hereby and thereby will not
     conflict with or constitute or result in a breach of or a default under (or
     an event which with notice or passage of time or both would constitute a
     default under) or violation of any of (i) the terms or provisions of any
     Contract, except for any such conflict, breach, default, violation or event
     which would not, individually or in the aggregate, have a Material Adverse
     Effect, (ii) the certificate of incorporation or bylaws of the Company or
     any of the Subsidiaries or (iii) (assuming compliance with all applicable
     state securities or "Blue Sky" laws and assuming the accuracy of the
     representations and warranties of the Purchaser and Elan set forth in
     Section 4 of this Agreement) any statute, judgment, decree, order, rule or
     regulation applicable to the Company or any of the Subsidiaries or any of
     their respective properties or assets, except for any such conflict, breach
     or violation which would not, individually or in the aggregate, have a
     Material Adverse Effect.

          (m) The Company has filed with the Securities and Exchange Commission
     (the "SEC") all required forms, reports, registration statements and
     documents required to be filed by it with the SEC since December 31, 1996
     (collectively, the "SEC Reports"), all of which complied as to form when
     filed in all material respects with the applicable provisions of the
     Securities Act and the Securities Exchange Act of 1934, as amended (the
     "Exchange Act"), as the case may be. As of their respective dates, the SEC
     Reports (including all exhibits and schedules thereto and documents
     incorporated by reference therein) did not contain any untrue statement of
     a material fact or omit to state a material fact required to be stated
     therein or necessary to make the statements therein, in light of the
     circumstances under which they were made, not misleading.

          (n) The audited consolidated financial statements and unaudited
     consolidated interim financial statements of the Company and the
     Subsidiaries included or incorporated by reference in any of the SEC
     Reports have been prepared in accordance with generally accepted accounting
     principles applied on a consistent basis during the periods involved,
     except as otherwise stated therein, and present fairly, in all material
     respects, the consolidated finan-


<PAGE>
                                      -10-


     cial position of the Company and the Subsidiaries at the dates thereof and
     the consolidated results of operations and cash flows for the periods then
     ended (subject, in the case of any unaudited interim financial statements,
     to normal year-end adjustments and to the extent they include footnotes or
     may be condensed or summary statements) and such audited financial
     statements are accompanied by an unqualified opinion thereon by the
     Company's independent auditors.

          (o) Except as set forth on Schedule 3(o), there is not pending or, to
     the knowledge of the Company, threatened any action, suit, proceeding,
     inquiry or investigation to which the Company or any of the Subsidiaries is
     a party, or to which the property or assets of the Company or any of the
     Subsidiaries are subject, before or brought by any court, arbitrator or
     governmental agency or body which, if determined adversely to the Company
     or any such Subsidiary, would, individually or in the aggregate, have a
     Material Adverse Effect, or which seeks to restrain, enjoin, prevent the
     consummation of or otherwise challenge (i) the issuance or sale of the
     Shares, the License Shares or the Securities, (ii) the consummation of the
     other transactions contemplated by this Agreement or the Registration
     Rights Agreement or (iii) the issuance of the License Shares pursuant to
     the License Agreement.

          (p) Each of the Company and the Subsidiaries possesses all licenses,
     permits, certificates, consents, orders, approvals and other authorizations
     from, and has made all declarations and filings with, all federal, state,
     local and other governmental authorities, all self-regulatory organizations
     and all courts and other tribunals presently required or necessary to own
     or lease, as the case may be, and to operate its respective properties and
     to carry on its respective businesses as now conducted and as proposed to
     be conducted ("Permits"), except as disclosed in the SEC Reports and except
     where the failure to obtain such Permits would not, individually or in the
     aggregate, have a Material Adverse Effect; each of the Company and the
     Subsidiaries has fulfilled and performed all of its obligations with
     respect to such Permits and no event has occurred which allows, or after
     notice or lapse of time would allow, revocation or termination thereof or
     results in any other material impairment of the rights of the holder of any
     such Permit; and none of the Company or the Subsidiaries has received any
     notice of any proceeding relating to revocation or modification of any such
     Permit, 


<PAGE>
                                      -11-


     except where such revocation or modification would not, individually or in
     the aggregate, have a Material Adverse Effect.

          (q) Since June 30, 1998 and except as otherwise set forth in the SEC
     Reports, (i) except as set forth on Schedule 3(q), none of the Company or
     the Subsidiaries has incurred any liabilities or obligations, direct or
     contingent, or entered into or agreed to enter into any transactions or
     contracts (written or oral) not in the ordinary course of business, which
     liabilities, obligations, transactions or contracts would, individually or
     in the aggregate, be material to the business, assets, liabilities
     (contingent or otherwise), operations, condition (financial or otherwise),
     solvency or prospects of the Company and the Subsidiaries, taken as a
     whole, (ii) none of the Company or the Subsidiaries has purchased any of
     its outstanding capital stock, nor declared, paid or otherwise made any
     dividend or distribution of any kind on its capital stock (other than with
     respect to the Subsidiaries, the purchase of, or dividend or distribution
     on, capital stock owned by the Company) and (iii) there has not been any
     material change in the capital stock or long-term indebtedness of the
     Company or the Subsidiaries.

          (r) Each of the Company and the Subsidiaries has filed all necessary
     federal, state and foreign income and franchise tax returns, except where
     the failure to so file such returns would not, individually or in the
     aggregate, have a Material Adverse Effect, and has paid all taxes shown as
     due thereon; and other than tax deficiencies which the Company or any
     Subsidiary is contesting in good faith and for which the Company or such
     Subsidiary has provided adequate reserves, there is no tax deficiency that
     has been asserted against the Company or any of the Subsidiaries that
     would, individually or in the aggregate, have a Material Adverse Effect.

          (s) Each of the Company and the Subsidiaries has good and marketable
     title to all real property and good title to all personal property owned by
     it and good and marketable title to all leasehold estates in the real and
     personal property being leased by it free and clear of all liens, charges,
     encumbrances or restrictions, except as set forth on Schedule 3(s) and
     except to the extent the failure to have such title or the existence of
     such liens, charges, encumbrances or restrictions would not, individually
     or in the aggregate, have a Material Adverse Effect.


<PAGE>
                                      -12-


          (t) Each of the Contracts is valid and enforceable against the Company
     or the Subsidiaries, as the case may be, and to the best of the Company's
     knowledge, is valid and enforceable against the other party or parties
     thereto and the Company is not, and has no actual knowledge that any other
     party is, in default under or in respect of any such Contract, with only
     such exceptions as would not, individually or in the aggregate, have a
     Material Adverse Effect.

          (u) Each of the Company and the Subsidiaries owns or possesses
     adequate licenses or other valid rights to use all patents and applications
     therefore, trademarks, service marks, trade names, copyrights and know-how
     (collectively, "Proprietary Rights") necessary to conduct the businesses
     now or proposed to be conducted by it, except for such lack of or defects
     in ownership as would not, individually or in the aggregate, have a
     Material Adverse Effect. None of the Company or the Subsidiaries has
     received any notice that any Proprietary Rights have been declared
     unenforceable or otherwise invalid by any court or governmental agency
     other than notices relating to Proprietary Rights the loss of which would
     not, individually or in the aggregate, have a Material Adverse Effect.
     Except as set forth on Schedule 3(u), none of the Company or the
     Subsidiaries has received any notice of infringement of or conflict with
     (or knows of any such infringement of or conflict with) asserted rights of
     others with respect to any Proprietary Rights which, if such assertion of
     infringement or conflict were sustained, would have a Material Adverse
     Effect.

          (v) Except as would not, individually or in the aggregate, have a
     Material Adverse Effect (A) each of the Company and the Subsidiaries is in
     compliance with and not subject to liability under applicable Environmental
     Laws (as defined below), (B) each of the Company and the Subsidiaries has
     made all filings and provided all notices required under any applicable
     Environmental Law, and has and is in compliance with all Permits required
     under any applicable Environmental Laws and each of them is in full force
     and effect, (C) there is no civil, criminal or administrative action, suit,
     demand, claim, hearing, notice of violation, investigation, proceeding,
     notice or demand letter or request for information pending or, to the
     knowledge of the Company or the Subsidiaries, threatened against the
     Company or any Subsidiary under any Environmental Law, (D) no lien, charge,
     encumbrance or restric-


<PAGE>
                                      -13-


     tion has been recorded under any Environmental Law with respect to any
     assets, facility or property owned, operated, leased or controlled by the
     Company or any Subsidiary, (E) none of the Company or the Subsidiaries has
     received notice that it has been identified as a potentially responsible
     party under the Comprehensive Environmental Response, Compensation and
     Liability Act of 1980, as amended ("CERCLA"), or any comparable state law,
     (F) no property or facility of the Company or any Subsidiary is (i) listed
     or proposed for listing on the National Priorities List under CERCLA or
     (ii) listed in the Comprehensive Environmental Response, Compensation and
     Liability Information System List promulgated pursuant to CERCLA, or on any
     comparable list maintained by any state or local governmental authority.

          For purposes of this Agreement, "Environmental Laws" means the common
     law and all applicable federal, state and local laws or regulations, codes,
     orders, decrees, judgments or injunctions issued, promulgated, approved or
     entered thereunder, relating to pollution or protection of public or
     employee health and safety or the environment, including, without
     limitation, laws relating to (i) emissions, discharges, releases or
     threatened releases of hazardous materials into the environment (including,
     without limitation, ambient air, surface water, groundwater, land surface
     or subsurface strata), (ii) the manufacture, processing, distribution, use,
     generation, treatment, storage, disposal, transport or handling of
     hazardous materials, and (iii) underground and aboveground storage tanks
     and related piping, and emissions, discharges, releases or threatened
     releases therefrom.

          (w) There is no strike, labor dispute, slowdown or work stoppage with
     the employees of the Company or the Subsidiaries which is pending or, to
     the knowledge of the Company or the Subsidiaries, threatened, other than
     any such strike, labor dispute, slowdown or work stoppage which would not,
     individually or in the aggregate, have a Material Adverse Effect.

          (x) Each of the Company and the Subsidiaries carries insurance in such
     amounts and covering such risks as is adequate for the conduct of its
     business and the value of its properties.

          (y) None of the Company or the Subsidiaries has any liability for any
     prohibited transaction or funding defi-


<PAGE>
                                      -14-


     ciency or any complete or partial withdrawal liability with respect to any
     pension, profit sharing or other plan which is subject to the Employee
     Retirement Income Security Act of 1974, as amended ("ERISA"), to which the
     Company or any Subsidiary makes or ever has made a contribution and in
     which any employee of the Company or any Subsidiary is or has ever been a
     participant. With respect to such plans, the Company and the Subsidiaries
     are in compliance in all material respects with all applicable provisions
     of ERISA.

          (z) Each of the Company and the Subsidiaries (i) makes and keeps
     accurate books and records and (ii) maintains internal accounting controls
     which provide reasonable assurance that (A) transactions are executed in
     accordance with management's authorization, (B) transactions are recorded
     as necessary to permit preparation of its financial statements and to
     maintain accountability for its assets, (C) access to its assets is
     permitted only in accordance with management's authorization and (D) the
     reported accountability for its assets is compared with existing assets at
     reasonable intervals.

          (aa) Except as provided in the Registration Rights Agreement, the
     Company has not granted or agreed to grant any registration rights to any
     person or entity.

          (bb) Immediately after the issuance of each of the Initial Notes, the
     License Notes and any Additional Notes, the fair value and present fair
     saleable value of the assets of the Company (on a consolidated basis) will
     exceed the sum of its stated liabilities and identified contingent
     liabilities; the Company (on a consolidated basis) is not and will not be
     (on a consolidated basis) after giving effect to the issuance of each of
     the Initial Notes, the License Notes or any Additional Notes, (a) left with
     unreasonably small capital with which to carry on its business as it is
     proposed to be conducted, (b) unable to pay its debts (contingent or
     otherwise) as they mature or (c) otherwise insolvent.

          (cc) Under the Preferred Share Rights Agreement, dated as of September
     13, 1996, between the Company and Wells Fargo Bank, N.A., as amended (the
     "Rights Agreement"), no event has occurred that has caused or will cause,
     and none of the execution of this Agreement, the Registration Rights
     Agreement or the License Agreement, or the consummation of the transactions
     contemplated hereby 


<PAGE>
                                      -15-


     or thereby, including the issuance and sale of the Shares, the Conversion
     Shares, the License Shares and the Securities, will cause, rights issued
     thereunder to become exercisable or a "Distribution Date" to occur,
     assuming compliance by Elan and its Affiliates with the provisions of
     Section 14(c) of this Agreement.

          (dd) Except as otherwise disclosed to the Purchaser, no person has or
     will have, as a result of the transactions contemplated by this Agreement
     or the License Agreement, any right, interest or valid claim against or
     upon the Company for any commission, fee or other compensation as a finder
     or broker because of any act by the Company or of any agent of the Company.
     The Company will pay, and hold the Purchaser harmless against, any
     liability, loss or expense (including, without limitation, reasonable
     attorneys' fees and out-of-pocket expenses) arising in connection with any
     claim for any such commission, fee or other compensation.

     Elan is intended to be a third-party beneficiary of each of the
representations, warranties and agreements set forth in this Section 3,
excluding Section 3(b), (c), (h), (i) and (bb).


     SECTION 4. Representations of the Purchaser and Elan.

     (a) The Purchaser represents and warrants to and agrees with the Company as
follows:

          (i) The Purchaser has all requisite corporate power and authority to
     execute, deliver and perform its obligations under this Agreement. This
     Agreement has been duly and validly authorized, executed and delivered by
     the Purchaser and constitutes a valid and legally binding agreement of the
     Purchaser enforceable against the Purchaser in accordance with its terms,
     except that the enforcement hereof may be subject to (i) bankruptcy,
     insolvency, reorganization, moratorium or other similar laws now or
     hereafter in effect relating to creditors' rights generally and (ii)
     general principles of equity and the discretion of the court before which
     any proceeding therefor may be brought.

          (ii) The Purchaser has all requisite corporate power and authority to
     execute, deliver and perform its obligations under the Registration Rights
     Agreement. The Regis-


<PAGE>
                                      -16-


     tration Rights Agreement has been duly and validly authorized by the
     Purchaser and, when executed and delivered by the Purchaser, will
     constitute a valid and legally binding agreement of the Purchaser
     enforceable against the Purchaser in accordance with its terms, except that
     (A) the enforcement thereof may be subject to (i) bankruptcy, insolvency,
     reorganization, moratorium or other similar laws now or hereafter in effect
     relating to creditors' rights generally and (ii) general principles of
     equity and the discretion of the court before which any proceeding therefor
     may be brought and (B) any rights to indemnity or contribution thereunder
     may be limited by federal and state securities laws and public policy
     considerations.

          (iii) The Purchaser acknowledges that none of the Shares or the
     Initial Notes have been, nor will the Additional Notes or the Conversion
     Shares be, registered under the Securities Act or any other applicable
     securities laws, are being issued or sold, or will be issued or sold, in
     transactions not requiring registration under the Securities Act and,
     unless so registered, may not be offered, sold or otherwise transferred
     except in compliance with the registration requirements of the Securities
     Act or any other applicable securities law, pursuant to an exemption
     therefrom or in a transaction not subject thereto and in each case in
     compliance with the conditions for transfer set forth in clause (v) of this
     paragraph (a).

          (iv) The Purchaser is outside the United States and is not a "U.S.
     person" (as such term is defined in Regulation S).

          (v) Until the expiration of the "one-year distribution compliance
     period" within the meaning of Rule 903 of Regulation S, the Purchaser will
     not sell or otherwise transfer the Shares, the Securities or the Conversion
     Shares, except (i) to the Company or its Subsidiaries, (ii) pursuant to an
     effective registration statement which has been declared effective under
     the Securities Act, (iii) in an offshore transaction in accordance with
     Rule 904 of Regulation S or (iv) pursuant to any other available exemption
     from the registration requirements of the Securities Act, including Rule
     144 thereunder ("Rule 144"). After the expiration of such "one-year
     distribution compliance period," the Purchaser will not sell or otherwise
     transfer the Shares, the Securities or the Conversion Shares, except
     pursuant to registration under the Securities Act or an available exemption
     therefrom and, in 


<PAGE>
                                      -17-


     any case, in accordance with the provisions of Regulation S and applicable
     state securities laws.

          (vi) The Purchaser understands that the certificates representing the
     Shares and any Conversion Shares will, so long as appropriate, bear the
     following legend:

          THE SHARES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED
          UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), MAY NOT BE
          SOLD, TRANSFERRED OR OTHERWISE DISPOSED OF IN THE ABSENCE OF AN
          EFFECTIVE REGISTRATION STATEMENT UNDER THE ACT OR PURSUANT TO A VALID
          EXEMPTION THEREFROM AND HAVE BEEN SOLD IN RELIANCE ON THE EXEMPTION
          FROM REGISTRATION PROVIDED BY REGULATION S UNDER THE ACT ("REGULATION
          S"). THE SHARES REPRESENTED BY THIS CERTIFICATE MAY NOT BE SOLD,
          TRANSFERRED OR OTHERWISE DISPOSED OF EXCEPT IN ACCORDANCE WITH THE
          PROVISIONS OF REGULATION S (ss.230.901 THROUGH ss.230.905, AND
          PRELIMINARY NOTES). HEDGING TRANSACTIONS INVOLVING THE SHARES
          REPRESENTED BY THIS CERTIFICATE MAY NOT BE CONDUCTED UNLESS IN
          COMPLIANCE WITH THE ACT.

          THE TRANSFER OF THE SHARES REPRESENTED BY THIS CERTIFICATE IS SUBJECT
          TO THE CONDITIONS SPECIFIED IN A SECURITIES PURCHASE AGREEMENT, DATED
          AS OF NOVEMBER 6, 1998, BY AND AMONG THE COMPANY, ELAN INTERNATIONAL
          SERVICES, LTD. AND ELAN CORPORATION, PLC, AND THE COMPANY RESERVES THE
          RIGHT TO REFUSE THE TRANSFER OF SUCH SHARES UNTIL SUCH CONDITIONS HAVE
          BEEN FULFILLED WITH RESPECT TO SUCH TRANSFER. A COPY OF SUCH
          CONDITIONS WILL BE FURNISHED BY THE COMPANY TO THE HOLDER HEREOF
          WITHOUT CHARGE.

          (vii) The Purchaser agrees that the Company shall be entitled to make
     a notation on its records and give instructions to any transfer agent of
     the Common Stock in order to implement the restrictions on transfer set
     forth in this Agreement.

          (viii) The Purchaser acknowledges that it believes that it has
     received all information it considers necessary or appropriate and has had
     an opportunity to ask questions and receive answers from the Company
     regarding the terms and conditions of the issuance and sale of the Shares
     and 


<PAGE>
                                      -18-


     the Securities and the business, properties, prospects and financial
     condition of the Company; provided that this clause (viii) shall in no way
     limit or modify the representations and warranties of the Company set forth
     in Section 3 of this Agreement or the right of the Purchaser to rely
     thereon. The Purchaser acknowledges that it is a sophisticated investor and
     that an investment in the Shares and the Securities involves a high degree
     of risk. The Purchaser further acknowledges that the Share Purchase Price
     may or may not exceed the latest publicly quoted per share "asked" price of
     the Common Stock.

          (ix) The Purchaser is purchasing the Shares and the Securities, and,
     to the extent that the Purchaser converts the Securities, will acquire the
     Conversion Shares, for its own account for the purpose of investment and
     not (i) with a view to, or for sale in connection with, any distribution
     thereof or (ii) for the account or on behalf of any "U.S. person" (as such
     term is defined in Regulation S). The Purchaser understands, acknowledges
     and agrees that it must bear the economic risk of its investment in the
     Shares, the Conversion Shares and the Securities for an indefinite period
     of time and that prior to any offer or sale of such securities, the Company
     may require, as a condition to effecting a transfer of the Shares, the
     Conversion Shares or the Securities, an opinion of counsel to the
     Purchaser, acceptable to the Company, as to the registration or exemption
     therefrom under the Securities Act.

          (x) The Purchaser was not formed specifically for the purpose of
     acquiring the Shares or the Securities purchased or to be purchased
     pursuant to this Agreement.

          (xi) The execution, delivery and performance by the Purchaser of this
     Agreement and the Registration Rights Agreement and the consummation by the
     Purchaser of the transactions contemplated hereby and thereby will not
     conflict with or constitute or result in a breach of or a default under (or
     an event which with notice or passage of time or both would constitute a
     default under) or violation of any of (i) the terms or provisions of any
     indenture, mortgage, deed of trust, loan agreement, note, lease, license,
     franchise agreement, permit, certificate, contract or other agreement or
     instrument to which the Purchaser is a party, except for any such conflict,
     breach, default, violation or event which would not, individually or in the
     aggregate, have a material adverse ef-


<PAGE>
                                      -19-


     fect on the business, assets, liabilities (contingent or otherwise),
     operations, condition (financial or otherwise), solvency, properties,
     prospects or material agreements of the Purchaser and its subsidiaries,
     taken as a whole, (ii) the certificate of incorporation or bylaws of the
     Purchaser or (iii) (assuming compliance with all applicable state
     securities or "Blue Sky" laws and assuming the accuracy of the
     representations and warranties of the Company set forth in Section 3 of
     this Agreement) any statute, judgment, decree, order, rule or regulation
     applicable to the Purchaser or any of its respective properties or assets,
     except for any such conflict, breach or violation which would not,
     individually or in the aggregate, have a material adverse effect on the
     business, assets, liabilities (contingent or otherwise), operations,
     condition (financial or otherwise), solvency, properties, prospects or
     material agreements of the Purchaser and its subsidiaries, taken as a
     whole.

          (xii) No consent, approval, authorization or order of any court or
     governmental agency or body or third party is required for the execution,
     delivery or performance of this Agreement or the Registration Rights
     Agreement by the Purchaser or the consummation of the transactions
     contemplated hereby or thereby, except that no representation or warranty
     is made with respect to filings required by the HSR Act in connection with
     the conversion of the Securities.

          (xiii) Except as otherwise disclosed to the Company, no person has or
     will have, as a result of the transactions contemplated by this Agreement,
     any right, interest or valid claim against or upon the Purchaser for any
     commission, fee or other compensation as a finder or broker because of any
     act by the Purchaser or of any agent of the Purchaser. The Purchaser will
     pay, and hold the Company harmless against, any liability, loss or expense
     (including without limitation, reasonable attorneys' fees and out-of-pocket
     expenses) arising in connection with any claim for any such commission, fee
     or other compensation.

     (b) Elan represents and warrants to and agrees with the Company as follows:

          (i) Elan has all requisite corporate power and authority to execute,
     deliver and perform its obligations under this Agreement. This Agreement
     has been duly and validly authorized, executed and delivered by Elan and

<PAGE>
                                      -20-


     constitutes a valid and legally binding agreement of Elan enforceable
     against Elan in accordance with its terms, except that the enforcement
     hereof may be subject to (i) bankruptcy, insolvency, reorganization,
     moratorium or other similar laws now or hereafter in effect relating to
     creditors' rights generally and (ii) general principles of equity and the
     discretion of the court before which any proceeding therefor may be
     brought.

          (ii) Elan acknowledges that the License Shares will not be registered
     under the Securities Act or any other applicable securities laws, will be
     issued in transactions not requiring registration under the Securities Act
     and, unless so registered, may not be offered, sold or otherwise
     transferred except in compliance with the registration requirements of the
     Securities Act or any other applicable securities law, pursuant to an
     exemption therefrom or in a transaction not subject thereto and in each
     case in compliance with the conditions for transfer set forth in paragraph
     (v) of this paragraph (b).

          (iii) Elan is outside the United States and is not a "U.S. person" (as
     such term is defined in Regulation S).

          (iv) Until the expiration of the "one-year distribution compliance
     period" within the meaning of Rule 903 of Regulation S, Elan will not sell
     or otherwise transfer the License Shares, except (i) to the Company or its
     Subsidiaries, (ii) pursuant to an effective registration statement which
     has been declared effective under the Securities Act, (iii) in an offshore
     transaction in accordance with Rule 904 of Regulation S or (iv) pursuant to
     any other available exemption from the registration requirements of the
     Securities Act, including Rule 144. After the expiration of such "one-year
     distribution compliance period," Elan will not sell or otherwise transfer
     the License Shares, except pursuant to registration under the Securities
     Act or an available exemption therefrom and, in any case, in accordance
     with the provisions of Regulation S and applicable state securities laws.

          (v) Elan understand that the certificates representing the License
     Shares will, so long as appropriate, bear the legend set forth in clause
     (vi) of paragraph (a) of this Section 4.

          (vi) Elan agrees that the Company shall be entitled to make a notation
     on its records and give instructions to 


<PAGE>
                                      -21-


     any transfer agent of the Common Stock in order to implement the
     restrictions on transfer set forth in this Agreement.

          (vii) Elan acknowledges that it believes that it has received all
     information it considers necessary or appropriate and has had an
     opportunity to ask questions and receive answers from the Company regarding
     the terms and conditions of the issuance and sale of the License Shares and
     the business, properties, prospects and financial condition of the Company;
     provided that this clause (viii) shall in no way limit or modify the
     representations and warranties of the Company set forth in Section 3 of
     this Agreement or the right of Elan to rely thereon. Elan acknowledges that
     it is a sophisticated investor and that an investment in the License Shares
     involves a high degree of risk. Elan further acknowledges that the
     valuation price of the License Shares set forth in clauses 10.1.1(1), (3)
     and (4) of the License Agreement may or may not exceed the last publicly
     quoted per share "asked" price of the Common Stock on any License Share
     Issuance Date.

          (viii) Elan will be acquiring the License Shares for its own account
     for the purpose of investment and not (i) with a view to, or for sale in
     connection with, any distribution thereof or (ii) for the account or on
     behalf of any "U.S. person" (as such term is defined in Regulation S). Elan
     understands, acknowledges and agrees that it must bear the economic risk of
     its investment in the License Shares for an indefinite period of time and
     that prior to any offer or sale of such securities, the Company may
     require, as a condition to effecting a transfer of the License Shares, an
     opinion of counsel to Elan , acceptable to the Company, as to the
     registration or exemption therefrom under the Securities Act.

          (ix) Elan was not formed specifically for the purpose of acquiring the
     License Shares purchased pursuant to this Agreement.

          (x) Neither Elan nor any of its Affiliates has, directly or
     indirectly, within the past 90 days nor will such persons until the
     expiration of the "one-year distribution compliance period" within the
     meaning of Rule 903 of Regulation S commencing from the later to occur of
     (i) the last Additional Closing occurring on or before December 31, 1999
     and (ii) the last License Share Issuance occurring on or before the
     expiration or termination of the 


<PAGE>
                                      -22-


     License Agreement directly or indirectly, enter into any short selling of
     any equity security of the Company (including, without limitation, the
     Common Stock) or any hedging transaction with respect to any equity
     security of the Company, including, without limitation, puts, calls, or
     other option transactions, option writing and equity swaps, unless in
     compliance with the Securities Act.

          (xi) The execution, delivery and performance by Elan of this Agreement
     and the Registration Rights Agreement and the consummation by Elan of the
     transactions contemplated hereby and thereby will not conflict with or
     constitute or result in a breach of or a default under (or an event which
     with notice or passage of time or both would constitute a default under) or
     violation of any of (i) the terms or provisions of any indenture, mortgage,
     deed of trust, loan agreement, note, lease, license, franchise agreement,
     permit, certificate, contract or other agreement or instrument to which
     Elan is a party, except for any such conflict, breach, default, violation
     or event which would not, individually or in the aggregate, have a material
     adverse effect on the business, assets, liabilities (contingent or
     otherwise), operations, condition (financial or otherwise), solvency,
     properties, prospects or material agreements of Elan and its subsidiaries,
     taken as a whole, (ii) the certificate of incorporation or bylaws of Elan
     or (iii) (assuming compliance with all applicable state securities or "Blue
     Sky" laws and assuming the accuracy of the representations and warranties
     of the Company set forth in Section 3 of this Agreement) any statute,
     judgment, decree, order, rule or regulation applicable to Elan or any of
     its respective properties or assets, except for any such conflict, breach
     or violation which would not, individually or in the aggregate, have a
     material adverse effect on the business, assets, liabilities (contingent or
     otherwise), operations, condition (financial or otherwise), solvency,
     properties, prospects or material agreements of Elan and its subsidiaries,
     taken as a whole.

          (xii) No consent, approval, authorization or order of any court or
     governmental agency or body or third party is required for the execution,
     delivery or performance of this Agreement by Elan or the consummation of
     the transactions contemplated hereby, except that no representation or
     warranty is made with respect to filings required by the HSR Act in
     connection with the issuance and sale of 


<PAGE>
                                      -23-


     the License Shares pursuant to clauses 10.1.1(3) and (4) of the License
     Agreement.

          (xiii) Except as otherwise disclosed to the Company, no person has or
     will have, as a result of the transactions contemplated by this Agreement,
     any right, interest or valid claim against or upon Elan for any commission,
     fee or other compensation as a finder or broker because of any act by Elan
     or of any agent of Elan. Elan will pay, and hold the Company harmless
     against, any liability, loss or expense (including without limitation,
     reasonable attorneys' fees and out-of-pocket expenses) arising in
     connection with any claim for any such commission, fee or other
     compensation.

     SECTION 5. Conditions to Company's and Purchaser's Obligations at Initial
Closing. The respective obligations of each of the Company and the Purchaser to
consummate the purchase and sale of each of the Shares, the Initial Notes and
the License Notes, in each case, pursuant to Section 1(a) of this Agreement
shall be subject to the satisfaction of the following conditions at or prior to
the Initial Closing Date:

          (a) The sale of the Shares, the Initial Notes and the License Notes
     hereunder shall not be enjoined (temporarily or permanently) on the Initial
     Closing Date.

          (b) All consents, approvals, authorizations and orders of any court or
     governmental agency or body, or third party required in connection with the
     execution and delivery of this Agreement, the Registration Rights Agreement
     and the License Agreement and the consummation of the transactions
     contemplated hereby and thereby shall have been obtained.


     SECTION 6. Conditions to Purchaser's Obligations at Initial Closing. The
obligation of the Purchaser to purchase the Shares, the Initial Notes and the
License Notes, in each case, pursuant to Section 1(a) of this Agreement shall be
subject to satisfaction or waiver of the following conditions at or prior to the
Initial Closing Date: 

          (a) Each of the representations and warranties of the Company set
     forth in Section 3 hereof that are qualified by Material Adverse Effect or
     materiality shall be true and correct in all respects and each of the
     representations and warranties of the Company set forth in Section 3 hereof
     that are not so qualified shall be true and cor-


<PAGE>
                                      -24-


     rect in all material respects, in each case, on and as of the date hereof
     and on and as of the Initial Closing Date as if made on and as of the
     Initial Closing Date, except to the extent that such representations and
     warranties expressly relate to an earlier date; the statements of the
     Company's officers made pursuant to any certificate delivered in accordance
     with the provisions hereof shall be true and correct on and as of the date
     made; the Company shall have performed all covenants and agreements and
     satisfied all conditions on its part to be performed or satisfied hereunder
     at or prior to the Initial Closing Date; since June 30, 1998, and except as
     disclosed in the Company's (i) Registration Statement on Form S-4 filed
     with the SEC on July 9, 1998, (ii) Form 10-Q filed with the SEC on August
     14, 1998, (iii) Form 8-K filed with the SEC on August 25, 1998 and (iv)
     Form 8-K/A filed with the SEC on September 25, 1998 (the "Additional SEC
     Reports"), there shall have been no event or development, and no
     information shall have become known, that, individually or in the
     aggregate, has or would be reasonably likely to have a Material Adverse
     Effect.

     (b) On the Initial Closing Date, the Purchaser shall have received the
opinion, dated as of the Initial Closing Date and addressed to the Purchaser, of
each of Brobeck, Phleger & Harrison LLP, counsel for the Company, and the
General Counsel of the Company, substantially in the form attached hereto as
Exhibit B1 and Exhibit B2, respectively.

     (c) The Purchaser shall have received a certificate of the Company, dated
the Initial Closing Date, signed on behalf of the Company by its Chief Executive
Officer and its Chief Financial Officer, to the effect that:

          (i) Each of the representations and warranties of the Company
     contained in this Agreement that are qualified by Material Adverse Effect
     or materiality are true and correct in all respects and the representations
     and warranties of the Company contained in this Agreement that are not so
     qualified are true and correct in all material respects, in each case, on
     and as of the Initial Closing Date, except to the extent that such
     representations and warranties expressly relate to an earlier date, and the
     Company has performed all covenants and agreements and satisfied all
     conditions on its part to be performed or 


<PAGE>
                                      -25-


     satisfied hereunder at or prior to the Initial Closing Date;

          (ii) At the Initial Closing Date and since June 30, 1998, except as
     disclosed in the Additional SEC Reports, no event or development has
     occurred, and no information has become known, that, individually or in the
     aggregate, has or would be reasonably likely to have a Material Adverse
     Effect; and

          (iii) The sale of the Shares, the Initial Notes and the License Notes
     hereunder has not been enjoined (temporarily or permanently).

     (d) On the Initial Closing Date, the Purchaser shall have received the
Eleventh Addendum to the Amended Registration Rights Agreement, dated as of June
24, 1994, by and among the Company and those entities party thereto (the
"Registration Rights Agreement"), duly executed by the Company, and such
agreement shall be in full force and effect and there shall exist at and as of
the Initial Closing Date no condition that would constitute or result in a
breach of or a default under (or an event which with notice or passage of time
or both would constitute a default under) the Registration Rights Agreement.

     (e) On or prior to the Initial Closing Date, the Purchaser shall have
received a true and correct copy of the Rights Agreement, as amended through the
Initial Closing Date.

     (f) On the Initial Closing Date, the Company shall have delivered to the
Purchaser a duly executed copy of the Development, License and Supply Agreement,
dated as of the Initial Closing Date, by and between the Company and Elan (the
"License Agreement"); the License Agreement shall be in full force and effect
and there shall exist at and as of the Initial Closing Date no condition that
would constitute or result in a breach of or a default under (or an event which
with notice or passage of time or both would constitute a default under) the
License Agreement by the Company.

     All such documents, certificates, schedules or instruments delivered
pursuant to this Agreement will comply with the provisions hereof only if they
are reasonably satisfactory in all material respects to the Purchaser and
counsel for the Purchaser.



<PAGE>
                                      -26-


     SECTION 7. Conditions to Company's Obligations at Initial Closing. The
obligation of the Company to issue and sell the Shares, the Initial Notes and
the License Notes, in each case, pursuant to Section 1(a) of this Agreement
shall be subject to satisfaction or waiver of the following conditions at or
prior to the Initial Closing Date:

          (a) Each of the representations and warranties of each of the
     Purchaser and Elan set forth in Section 4 hereof that are qualified by
     materiality shall be true and correct in all respects and each of the
     representations and warranties of each of the Purchaser and Elan set forth
     in Section 4 hereof that are not so qualified shall be true and correct in
     all material respects, in each case, on and as of the date hereof and on
     and as of the Initial Closing Date as if made on and as of the Initial
     Closing Date, except to the extent that such representations and warranties
     expressly relate to an earlier date; the statements of each of the
     Purchaser's and Elan's officers made pursuant to any certificate delivered
     in accordance with the provisions hereof shall be true and correct on and
     as of the date made; each of the Purchaser and Elan shall have performed
     all covenants and agreements and satisfied all conditions on its part to be
     performed or satisfied hereunder at or prior to the Initial Closing Date.

          (b) The Company shall have received a certificate of the Purchaser,
     dated the Initial Closing Date, signed on behalf of the Purchaser by its
     President and Chief Financial Officer, to the effect that the
     representations and warranties of the Purchaser contained in this Agreement
     that are qualified by materiality are true and correct in all respects and
     the representations and warranties of the Purchaser contained in this
     Agreement that are not so qualified are true and correct in all material
     respects, in each case, on and as of the Initial Closing Date, except to
     the extent that such representations and warranties expressly relate to an
     earlier date, and the Purchaser has performed all covenants and agreements
     and satisfied all conditions on its part to be performed or satisfied
     hereunder at or prior to the Initial Closing Date.

          (c) The sale of the Shares and the Initial Notes hereunder has not
     been enjoined (temporarily or permanently).

          (d) The Purchaser shall have delivered the Share Purchase Price, the
     Initial Note Issue Price and the Li-


<PAGE>
                                      -27-


     cense Note Issue Price in accordance with Section 2(a) hereof.

          (e) On the Initial Closing Date, Elan shall have delivered to the
     Company a duly executed copy of the License Agreement; the License
     Agreement shall be in full force and effect and there shall exist at and as
     of the Initial Closing Date no condition that would constitute or result in
     a breach of or a default under (or an event which with notice or passage of
     time or both would constitute a default under) the License Agreement by
     Elan.

     All such documents, certificates, schedules or instruments delivered
pursuant to this Agreement will comply with the provisions hereof only if they
are reasonably satisfactory in all material respects to the Company and counsel
for the Company.


     SECTION 8. Conditions to Purchaser's Obligations at Additional Closings.

     (a) The obligation of the Purchaser to purchase Additional Notes pursuant
to Section 1(b) of this Agreement, the gross proceeds of which are to be used by
the Company to make the Seragen Payments or the Marathon Payment, as set forth
in the Purchase Request applicable thereto, shall be subject to satisfaction or
waiver of the following conditions at or prior to the Additional Closing Date
applicable thereto:

          (i) Each of the representations and warranties of the Company set
     forth in Section 3 hereof that are qualified by Material Adverse Effect or
     materiality shall be true and correct in all respects and each of the
     representations and warranties of the Company set forth in Section 3 hereof
     that are not so qualified shall be true and correct in all material
     respects, in each case, on and as of such Additional Closing Date as if
     made on and as of such Additional Closing Date, except to the extent that
     such representations and warranties expressly relate to an earlier date;
     the statements of the Company's officers made pursuant to any certificate
     delivered in accordance with the provisions hereof shall be true and
     correct on and as of the date made; the Company shall have performed all
     covenants and agreements and satisfied all conditions on its part to be
     performed or satisfied hereunder at or prior to such Additional Closing
     Date; since June 30, 1998 and except as disclosed in Additional SEC
     Reports, there shall have been no event or development, and no informa-


<PAGE>
                                      -28-


     tion shall have become known, that, individually or in the aggregate, has
     or would be reasonably likely to have a Material Adverse Effect.

          (ii) On such Additional Closing Date, the Purchaser shall have
     received the opinion, dated as of such Additional Closing Date and
     addressed to the Purchaser, of each of Brobeck, Phleger & Harrison LLP,
     counsel for the Company (or such other counsel as is reasonably acceptable
     to the Purchaser), and the General Counsel of the Company substantially in
     the form attached hereto as Exhibit C1 and Exhibit C2, respectively.

          (iii) The Purchaser shall have received a certificate of the Company,
     dated such Additional Closing Date, signed on behalf of the Company by its
     Chief Executive Officer and its Chief Financial Officer, to the effect
     that:

               (1) The representations and warranties of the Company contained
          in this Agreement that are qualified by Material Adverse Effect or
          materiality are true and correct in all respects and the
          representations and warranties of the Company contained in this
          Agreement that are not so qualified are true and correct in all
          material respects, in each case, on and as of such Additional Closing
          Date, except to the extent that such representations and warranties
          expressly relate to an earlier date, and the Company has performed all
          covenants and agreements and satisfied all conditions on its part to
          be performed or satisfied hereunder at or prior to such Additional
          Closing Date;

               (2) At such Additional Closing Date and since June 30, 1998,
          except as set forth in the Additional SEC Reports, no event or
          development has occurred, and no information has become known, that,
          individually or in the aggregate, has or would be reasonably likely to
          have a Material Adverse Effect;

               (3) The sale of such Additional Notes hereunder has not been
          enjoined (temporarily or permanently); and

               (4) Each of this Agreement, the Registration Rights Agreement or
          the New Registration Rights Agreement, as the case may be, the License
          Agreement (to the extent not previously terminated by mutual 


<PAGE>
                                      -29-


          agreement of the parties thereto) and, to the extent outstanding, the
          Securities, are, and after giving effect to the issuance and sale of
          such Additional Notes, will be, valid and enforceable against the
          Company, except that (A) the enforcement hereof and thereof may be
          subject to (i) bankruptcy, insolvency, reorganization, moratorium or
          other similar laws now or hereafter in effect relating to creditors'
          rights generally and (ii) general principles of equity and the
          discretion of the court before which any proceeding therefor may be
          brought and (B) any rights to indemnity or contribution under the
          Registration Rights Agreement or the New Registration Rights
          Agreement, as the case may be, may be limited by federal and state
          securities laws and public policy considerations, and no event that
          constitutes a material breach of or a material default under (or an
          event which, with notice or passage of time or both would constitute a
          material default under) this Agreement, the Registration Rights
          Agreement or the New Registration Rights Agreement, as the case may
          be, the License Agreement (to the extent not previously terminated by
          mutual agreement of the parties thereto) or, to the extent
          outstanding, the Securities, by the Company has occurred and is
          continuing or, after giving effect to the issuance and sale of such
          Additional Notes, will have occurred and be continuing.

          (iv) Both before and after giving effect to the issuance and sale of
     such Additional Notes, each of this Agreement, the Registration Rights
     Agreement or the New Registration Rights Agreement, as the case may be, the
     License Agreement (to the extent not previously terminated by mutual
     agreement of the parties thereto) and, to the extent outstanding, the
     Securities, shall be valid and enforceable against the Company, except that
     (A) the enforcement hereof and thereof may be subject to (i) bankruptcy,
     insolvency, reorganization, moratorium or other similar laws now or
     hereafter in effect relating to creditors' rights generally and (ii)
     general principles of equity and the discretion of the court before which
     any proceeding therefor may be brought and (B) any rights to indemnity or
     contribution under the Registration Rights Agreement or the New
     Registration Rights Agreement, as the case may be, may be limited by
     federal and state securities laws and public policy considerations, and no
     event that constitutes a material breach of or a material default under (or
     an event which, with notice or passage of 


<PAGE>
                                      -30-


     time or both would constitute a material default under) this Agreement, the
     Registration Rights Agreement or the New Registration Rights Agreement, as
     the case may be, the License Agreement (to the extent not previously
     terminated by mutual agreement of the parties thereto) or, to the extent
     outstanding, the Securities, by the Company shall have occurred and be
     continuing.

          (v) The Company shall have delivered to the Purchaser a Purchase
     Request relating to such Additional Notes in accordance with Section 1(b)
     of this Agreement.

          (vi) The Purchaser shall have completed a confirmatory due diligence
     investigation relating to Seragen or Marathon, as the case may be
     (including confirmatory legal, accounting and business due diligence), and
     shall be satisfied, in its reasonable judgment, with the results thereof.

          (vii) All consents, approvals, authorizations and orders of any court
     or governmental agency or body, or third party required in connection with
     the issuance and sale of such Additional Notes shall have been obtained,
     except for any filings required by the HSR Act upon conversion of such
     Additional Notes.

          (viii) The issuance and sale of such Additional Notes hereunder shall
     not be enjoined (temporarily or permanently) on the Additional Closing Date
     applicable thereto.

     (b) The obligation of the Purchaser to purchase Additional Notes pursuant
to Section 1(b) of this Agreement the gross proceeds of which are to be used by
the Company for any purpose other than to make the Seragen Payments or the
Marathon Payment, as set forth in the Purchase Request applicable thereto, shall
be subject to the prior written consent of the Purchaser, which consent may be
withheld in the Purchaser's sole discretion whether or not the conditions set
forth in paragraph (a) of this Section 8 have been satisfied or previously
waived.

     All such documents, certificates, schedules, notices and instruments
delivered pursuant to this Agreement will comply with the provisions hereof only
if they are reasonably satisfactory in all material respects to the Purchaser
and counsel for the Purchaser.



<PAGE>
                                      -31-


     SECTION 9. Conditions to the Company's Obligations at Additional Closings.
The obligation of the Company to issue Additional Notes pursuant to Section 1(b)
of this Agreement shall be subject to satisfaction or waiver of the following
conditions at or prior to the Additional Closing Date applicable thereto:

          (a) Each of the representations and warranties of the Purchaser set
     forth in Section 4(a) hereof that are qualified by materiality shall be
     true and correct in all respects and each of the representations and
     warranties of the Purchaser set forth in Section 4(a) hereof that are not
     so qualified shall be true and correct in all material respects, in each
     case, on and as of such Additional Closing Date as if made on and as of
     such Additional Closing Date, except to the extent that such
     representations and warranties expressly relate to an earlier date; the
     statements of the Purchaser's officers made pursuant to any certificate
     delivered in accordance with the provisions hereof shall be true and
     correct on and as of the date made; the Purchaser shall have performed all
     covenants and agreements and satisfied all conditions on its part to be
     performed or satisfied hereunder at or prior to such Additional Closing
     Date.

          (b) The Company shall have received a certificate of the Purchaser,
     dated the Initial Closing Date, signed on behalf of the Purchaser by its
     President and Chief Financial Officer, to the effect that:

               (i) the representation and warranties of the Purchaser contained
          in this Agreement that are qualified by materiality are true and
          correct in all respects and the representations and warranties of the
          Purchaser contained in this Agreement that are not so qualified are
          true and correct in all material respects, in each case, on and as of
          such Additional Closing Date, except to the extent that such
          representations and warranties expressly relate to an earlier date,
          and the Purchaser has performed all covenants and agreements and
          satisfied all conditions on its part to be performed or satisfied
          hereunder at or prior to such Additional Closing Date; and

               (ii) each of this Agreement, the Registration Rights Agreement or
          the New Registration Rights Agreement, as the case may be, and the
          License Agreement (to the extent not previously terminated by mu-


<PAGE>
                                      -32-


          tual agreement of the parties thereto) are valid and enforceable
          against the Purchaser and Elan, to the extent a party thereto, except
          that (A) the enforcement hereof and thereof may be subject to (i)
          bankruptcy, insolvency, reorganization, moratorium or other similar
          laws now or hereafter in effect relating to creditors' rights
          generally and (ii) general principles of equity and the discretion of
          the court before which any proceeding therefor may be brought and (B)
          any rights to indemnity or contribution under the Registration Rights
          Agreement or the New Registration Rights Agreement, as the case may
          be, may be limited by federal and state securities laws and public
          policy considerations, and no event that constitutes a material breach
          of or a material default under (or an event which, with notice or
          passage of time or both would constitute a material default under)
          this Agreement, the Registration Rights Agreement or the New
          Registration Rights Agreement, as the case may be, or the License
          Agreement (to the extent not previously terminated by mutual agreement
          of the parties thereto) by the Purchaser or Elan, to the extent a
          party thereto, has occurred and is continuing.

          (c) All consents, approvals, authorizations and orders of any court or
     governmental agency or body, or third party required in connection with the
     issuance and sale of such Additional Notes shall have been obtained, except
     for any filings required by the HSR Act upon conversion of such Additional
     Notes.

          (d) The sale of such Additional Notes hereunder has not been enjoined
     (temporarily or permanently).

          (e) The Purchaser shall have delivered the Additional Note Issue Price
     in accordance with Section 2(a) hereof.

     All such documents, certificates, schedule, notices and instruments
delivered pursuant to this Agreement will comply with the provisions hereof only
if they are reasonably satisfactory in all material respects to the Company and
counsel for the Company.


     SECTION 10. Conditions to Elan's Obligations at License Share Issuances.
The obligation of Elan to accept the issuance of License Shares in lieu of cash
payments pursuant to 


<PAGE>
                                      -33-


and in accordance with the terms of clauses 10.1.1(1), (3) and (4) of the
License Agreement shall be subject to satisfaction or waiver of the following
conditions at or prior to each License Share Issuance Date applicable thereto
(provided that, nothing in this Agreement shall relieve the Company from its
obligation to make cash payments to Elan pursuant to clauses 10.1.1(1), 10.1(3)
and (4) of the License Agreement in the event that any of the following
conditions is not so satisfied or waived at or prior to such License Share
Issuance Date):

          (a) Each of the representations and warranties of the Company set
     forth in Section 3 hereof that are qualified by Material Adverse Effect or
     materiality shall be true and correct in all respects and each of the
     representations and warranties of the Company set forth in Section 3 hereof
     that are not so qualified shall be true and correct in all material
     respects, in each case, on and as of such License Share Issuance Date as if
     made on and as of such License Share Issuance Date, except to the extent
     that such representations and warranties expressly relate to an earlier
     date; the statements of the Company's officers made pursuant to any
     certificate delivered in accordance with the provisions hereof shall be
     true and correct on and as of the date made; the Company shall have
     performed all covenants and agreements and satisfied all conditions on its
     part to be performed or satisfied hereunder at or prior to such License
     Share Issuance Date; since June 30, 1998 and except as disclosed in the
     Additional SEC Reports, there shall have been no event or development, and
     no information shall have become known, that, individually or in the
     aggregate, has or would be reasonably likely to have a Material Adverse
     Effect.

          (b) On such License Share Issuance Date, Elan shall have received the
     opinion, dated as of such License Share Issuance Date and addressed to the
     Purchaser, of each of Brobeck, Phleger & Harrison LLP, counsel for the
     Company (or such other counsel as is reasonably satisfactory to Elan), and
     the General Counsel of the Company substantially in the form attached
     hereto as Exhibits D1 and D2, respectively; provided that, in the case of
     License Shares to be issued to Elan pursuant to clause 10.1.1(1) of the
     License Agreement, such opinions shall be substantially in the form
     attached hereto as Exhibits D3 and D4, respectively.

          (c) Elan shall have received a certificate of the Company, dated such
     License Share Issuance Date, signed on 


<PAGE>
                                      -34-


     behalf of the Company by its Chief Executive Officer and its Chief
     Financial Officer, to the effect that:

               (i) The representations and warranties of the Company contained
          in this Agreement that are qualified by Material Adverse Effect or
          materiality are true and correct in all respects and the
          representations and warranties of the Company contained in this
          Agreement that are not so qualified are true and correct in all
          material respects, in each case, on and as of such License Share
          Issuance Date, except to the extent that such representations and
          warranties expressly relate to an earlier date, and the Company has
          performed all covenants and agreements and satisfied all conditions on
          its part to be performed or satisfied hereunder at or prior to such
          License Share Issuance Date;

               (ii) At such License Share Issuance Date and since June 30, 1998,
          except as set forth in the Additional SEC Reports, no event or
          development has occurred, and no information has become known, that,
          individually or in the aggregate, has or would be reasonably likely to
          have a Material Adverse Effect;

               (iii) The issuance of such License Shares has not been enjoined
          (temporarily or permanently); and

               (iv) Each of this Agreement, the Registration Rights Agreement or
          the New Registration Rights Agreement, as the case may be, the License
          Agreement and, to the extent outstanding, the Securities, are, and
          after giving effect to the issuance of such License Shares, will be,
          valid and enforceable against the Company, except that (A) the
          enforcement thereof may be subject to (i) bankruptcy, insolvency,
          reorganization, moratorium or other similar laws now or hereafter in
          effect relating to creditors' rights generally and (ii) general
          principles of equity and the discretion of the court before which any
          proceeding therefor may be brought and (B) any rights to indemnity or
          contribution under the Registration Rights Agreement or the New
          Registration Rights Agreement, as the case may be, may be limited by
          federal and state securities laws and public policy considerations,
          and no event that constitutes a breach of or a default under (or an
          event which, with notice or passage of time or both would constitute a
          default un-


<PAGE>
                                      -35-


          der) this Agreement, the Registration Rights Agreement or the New
          Registration Rights Agreement, as the case may be, the License
          Agreement or, to the extent outstanding, the Securities, by the
          Company has occurred and is continuing or, after giving effect to the
          issuance and sale of such License Shares, will have occurred and be
          continuing.

          (d) Both before and after giving effect to the issuance of such
     License Shares, each of this Agreement, the Registration Rights Agreement
     or the New Registration Rights Agreement, as the case may be, the License
     Agreement and, to the extent outstanding, the Securities, shall be valid
     and enforceable against the Company, except that (A) the enforcement
     thereof may be subject to (i) bankruptcy, insolvency, reorganization,
     moratorium or other similar laws now or hereafter in effect relating to
     creditors' rights generally and (ii) general principles of equity and the
     discretion of the court before which any proceeding therefor may be brought
     and (B) any rights to indemnity or contribution under the Registration
     Rights Agreement or the New Registration Rights Agreement, as the case may
     be, may be limited by federal and state securities laws and public policy
     considerations, and no event that constitutes a breach of or a default
     under (or an event which, with notice or passage of time or both would
     constitute a default under) this Agreement, the Registration Rights
     Agreement or the New Registration Rights Agreement, as the case may be, the
     License Agreement or, to the extent outstanding, the Securities, by the
     Company shall have occurred and be continuing.

          (e) All consents, approvals, authorizations and orders of any court or
     governmental agency or body, or third party required in connection with the
     issuance of such License Shares shall have been obtained.

          (f) The issuance of such License Shares shall not be enjoined
     (temporarily or permanently) on the License Share Issuance Date applicable
     thereto.

     All such documents, certificates, schedules, notices and instruments
delivered pursuant to this Agreement will comply with the provisions hereof only
if they are reasonably satisfactory in all material respects to the Purchaser
and counsel for the Purchaser.



<PAGE>
                                      -36-


     SECTION 11. Conditions to the Company's Obligations at License Share
Issuances. The obligation of the Company to issue License Shares in lieu of cash
payments (after the Company, at its option, has elected to issue License Shares)
pursuant to clauses 10.1.1(1), 10.1(3) and (4) of the License Agreement, shall
be subject to satisfaction or waiver of the following conditions at or prior to
the License Share Issuance Date applicable thereto; provided that, nothing in
this Agreement shall relieve the Company from its obligation to make cash
payments to Elan pursuant to clauses 10.1.1(1), 10.1(3) and (4) of the License
Agreement in the event that any of the following conditions is not so satisfied
or waived at or prior to such License Share Issuance Date; provided, further,
that, in the event that Elan is unable to satisfy the following conditions or
such conditions have not been waived prior to such License Share Issuance Date,
the Company and Elan shall negotiate in good faith to agree, on or prior to such
License Share Issuance Date, upon customary terms and conditions which will
enable the Company to issue the License Shares pursuant to a transaction exempt
from the registration requirements of the Securities Act pursuant Regulation D
thereunder, including the giving by Elan, to the extent possible, of
representations and warranties in connection therewith, so long as such
negotiation does not delay any License Share Issuance Date:

          (a) Each of the representations and warranties of Elan set forth in
     Section 4(b) hereof that are qualified by materiality shall be true and
     correct in all respects and each of the representations and warranties of
     Elan set forth in Section 4(b) hereof that are not so qualified shall be
     true and correct in all material respects, in each case, on and as of such
     License Share Issuance Date as if made on and as of such License Share
     Issuance Date, except to the extent that such representations and
     warranties expressly relate to an earlier date; the statements of Elan's
     officers made pursuant to any certificate delivered in accordance with the
     provisions hereof shall be true and correct on and as of the date made;
     Elan shall have performed all covenants and agreements and satisfied all
     conditions on its part to be performed or satisfied hereunder at or prior
     to such Additional Closing Date.

          (b) The Company shall have received a certificate of Elan, dated such
     License Share Issuance Date, signed on behalf of Elan by its President and
     Chief Financial Officer, to the effect that the representation and
     warranties of Elan contained in this Agreement that are qualified by
     materiality are true and correct in all respects and the 


<PAGE>
                                      -37-


     representations and warranties of Elan contained in this Agreement that are
     not so qualified are true and correct in all material respects, in each
     case, on and as of such License Share Issuance Date, except to the extent
     that such representations and warranties expressly relate to an earlier
     date and Elan has performed all covenants and agreements and satisfied all
     conditions on its part to be performed or satisfied hereunder at or prior
     to such License Share Issuance Date.

          (c) All consents, approvals, authorizations and orders of any court or
     governmental agency or body, or third party required in connection with the
     issuance of such License Shares shall have been obtained.


          (d) The issuance of such License Shares shall not be enjoined
     (temporarily or permanently) on the License Share Issuance Date applicable
     thereto.

     All such documents, certificates, schedule, notices and instruments
delivered pursuant to this Agreement will comply with the provisions hereof only
if they are reasonably satisfactory in all material respects to the Company and
counsel for the Company.


     SECTION 12. Conversion Prices.

     (a) The Initial Notes shall be convertible by the Purchaser in accordance
with their terms into Common Stock at a conversion price of $14.00 per share
(the "Initial Note Conversion Price").

     (b) The License Notes shall be convertible by the Purchaser in accordance
with their terms into Common Stock at a per share conversion price equal to the
sum of (i) [ * * * ] to the Initial Closing Date [ * * * ] plus (ii) the [ * * *
] (the "License Note Conversion Price"); provided that in no event shall the
License Note Conversion Price be less than $14.00 per share or greater than
$20.00 per share.

     (c) Any Additional Note shall be convertible by the Purchaser in accordance
with its terms into Common Stock at a per share conversion price equal to the
sum of (i) [ * * * ] plus (ii) [ * * * ] (the "Additional Note Conversion
Price"); provided that in no event shall the Additional Note Conversion Price be
less than $14.00 per share (the "Minimum Conversion Price") or greater than
$20.00 per share 


<PAGE>
                                      -38-


(the "Maximum Conversion Price"). Each of the Minimum Conversion Price and the
Maximum Conversion Price shall be subject to adjustment from time to time in
accordance with paragraph 6(i)(i), (ii), (iii), (iv) or (v) of the promissory
note attached hereto as Exhibit A.

     (d) For purposes of this Section 12, the "Closing Price" of the Common
Stock on any trading day shall mean the last reported sales price of the Common
Stock on such trading day, as reported by the Nasdaq National Market or, if the
Common Stock is listed on a United States securities exchange, the closing per
share sales price, regular way, on such trading day on the principal United
States securities exchange on which the Common Stock is traded or, if no such
sale takes place on such trading day, the average of the closing bid and asked
prices on such day.


     SECTION 13. Covenants of the Company.

     (a) The Company agrees that, prior to the termination of all rights
provided for in the Registration Rights Agreement in accordance with Section
1.17 thereof, the Company will prepare, execute and deliver to the Purchaser a
registration rights agreement (the "New Registration Rights Agreement"), to be
effective upon such termination, in form and substance substantially identical
to the Registration Rights Agreement; provided that the New Registration Rights
Agreement shall expire on the later of (i) December 31, 2003 and (ii) the date
on which no Securities are outstanding.

     (b) Subject to the terms and conditions specified in this paragraph (b),
the Company hereby grants to the Purchaser and Elan a right to purchase up to
the number of Additional Shares (as defined below) in connection with any
Transaction (as defined below) undertaken by the Company.

          (i) Each time the Company proposes to offer, sell or otherwise issue
     shares of any class of its capital stock or securities convertible into, or
     exercisable or exchangeable for, a class of capital stock ("Capital
     Stock"), in a public or private transaction (a "Transaction"), the Company
     shall deliver a notice in person, by air courier or by facsimile
     ("Notice"), to the Purchaser and Elan stating (a) the Company's bona fide
     intention to undertake such Transaction, (b) the number of shares of
     Capital Stock to be offered in the Transaction (the "Transaction Shares"),
     (c) the number of Additional Shares up to which the Purchaser and Elan may
     elect to 


<PAGE>
                                      -39-


     purchase in such Transaction (which would be added to the Transaction
     Shares), and (d) the price and terms, if any, upon which it proposes to
     offer, sell or otherwise issue Capital Stock in the Transaction.

          (ii) Within 10 business days after receipt by the Purchaser and Elan
     of the Notice, each of the Purchaser and Elan may elect to purchase, at the
     price and on the terms specified in the Notice, up to the number of
     Additional Shares set forth in the Notice. The number of shares of Capital
     Stock ("Additional Shares") that the Purchaser and Elan may elect to
     purchase and include in the Transaction shall be calculated as follows:

Additional Shares  =  Transaction Shares  --   Transaction Shares
                             1 - X%

     X% represents the percentage (stated as a decimal) of the outstanding
     shares of Common Stock then held by the Purchaser or Elan, as the case may
     be, (assuming the conversion of all Securities then held by the Purchaser
     or Elan, as the case may be, and the conversion, exercise or exchange of
     all Capital Stock then held by the Purchaser or Elan, as the case may be,
     and acquired pursuant to this paragraph (b)).

     In the event that the price or terms upon which the Company proposes to
     offer, sell or otherwise issue Capital Stock in the Transaction or the
     number of Transaction Shares to be included in such Transaction changes for
     any reason (other than including the Additional Shares) after the Notice is
     delivered to the Purchaser and Elan, the number of Additional Shares shall,
     with respect to a change in the number of Transaction Shares, be
     recalculated using the new number of Transaction Shares and, in any case,
     the Company shall promptly provide a revised Notice to the Purchaser and
     Elan reflecting such recalculated Additional Shares and any change to such
     price or terms. If the Company proposes to offer, sell or issue any Capital
     Stock for consideration other than cash, each of the Purchaser and Elan may
     exercise the right set forth in this paragraph (b) and purchase Additional
     Shares for cash at a per share purchase price equal to (i)(a) the face
     amount of any cash received for such Capital Stock plus (b) the fair market
     value of the non-cash consideration expressly received for such Capital
     Stock divided by (ii) the number of Transaction Shares issued in such
     Transaction (excluding any Additional Shares). The fair 


<PAGE>
                                      -40-


     market value of any such non-cash consideration shall be determined by an
     independent appraisal firm of nationally-recognized standing chosen jointly
     by the Company and the Purchaser and Elan.

          (iii) The rights of the Purchaser set forth in this paragraph (b)
     shall not be applicable to (a) the issuance or sale of Capital Stock under
     any plan, agreement or arrangement applicable only to employees, directors
     or consultants and approved by the Company's board of directors or (b) the
     issuance of securities pursuant to the conversion, exercise or exchange of
     convertible, exercisable or exchangeable securities.

          (iv) The rights and obligations of the Purchaser and Elan under this
     paragraph (b) shall not be assignable, except that such rights may be
     assigned by the each of the Purchaser and Elan to any of its Affiliates
     that agrees in writing to be bound by the provisions of this paragraph (b).

          (v) Notwithstanding anything to the contrary in this paragraph (b),
     the provisions of this paragraph (b) shall terminate and be of no further
     force and effect upon the consummation of (x) any consolidation of the
     Company with, or merger of the Company with or into, any person (including
     any individual, partnership, joint venture, corporation, trust or group
     thereof) ("Person") other than a consolidation or merger pursuant to which
     the stockholders of the Company immediately prior to such consolidation or
     merger own more than 50% of the outstanding securities entitled, under
     general circumstances, to vote in the election of directors of the
     surviving Person after such consolidation or merger or (y) any sale,
     transfer or conveyance of all or substantially all of the assets of the
     Company.

     (c) Upon the later of (i) the termination of all rights provided for in the
Registration Rights Agreement in accordance with Section 1.17 thereof and (ii)
the expiration of the New Registration Rights Agreement, and so long as any of
the Purchaser, Elan or any of their Affiliates continues to hold any Securities
or any Shares, Conversion Shares, License Shares or shares of Common Stock or
other Capital Stock issued pursuant to paragraph (b) of this Section 13, in
order to permit each of the Purchaser, Elan and their Affiliates to sell such
securities (subject to Section 14(a) hereof), from time to time, pursuant to
Rule 144, or any successor to such rule or 


<PAGE>
                                      -41-


any other rule or regulation of the SEC that may at any time permit the
Purchaser to sell the Shares without registration, the Company shall:

          (i) make and keep public information available, as those terms are
     understood and defined in Rule 144, at all times during which the Company
     is subject to the reporting requirements of the Securities Act or the
     Exchange Act;

          (ii) use its best efforts to file with the SEC in a timely manner all
     reports and other documents required to be filed by the Company under the
     Securities Act or the Exchange Act (at all times during which it is subject
     to such reporting requirements thereof); and

          (iii) (x) furnish to the Purchaser and Elan promptly upon request, a
     written statement by the Company as to its compliance with the reporting
     requirements of the Securities Act and the Exchange Act (at any time during
     which it is subject to such to such reporting requirements), a copy of the
     most recent annual or quarterly report of the Company, and such other
     reports and documents of the Company and other information in the
     possession of or reasonably obtainable by the Company as the Purchaser or
     Elan may reasonably request in availing itself of Rule 144, or any
     successor to such rule or any other rule or regulation of the SEC that may
     at any time permit the Purchaser or Elan to sell such securities without
     registration and (y) take any action (including cooperating with the
     Purchaser and Elan to cause the transfer agent for the Common Stock to
     remove any restrictive legend on the certificates evidencing such Common
     Stock) as shall be reasonably requested by the Purchaser and Elan or which
     shall otherwise facilitate the sale of such securities from time to time by
     the Purchaser and Elan pursuant to Rule 144, or any successor to such rule
     or any other rule or regulation of the SEC that may at any time permit the
     Purchaser or Elan to sell such securities without registration.

     (d) At such time as Elan acquires beneficial ownership (as defined under
Rule 13d-3 under the Exchange Act) of not less than 15.0% of the outstanding
Common Stock (assuming, for such purpose, the conversion of all Securities held
by Elan and its Affiliates and the conversion, exercise or exchange of all
Capital Stock held by Elan and its Affiliates and acquired pursuant to Section
13(b) hereof, in each case, regardless of the date on which such Securities or
Capital Stock become convertible, exercisable or exchangeable) (the "Beneficial
Owner-


<PAGE>
                                      -42-


ship Threshold"), Elan shall be entitled to designate one member of the
Company's Board of Directors (the "Elan Designee"); provided that, in the event
that Mr. John Groom is a member of the Board of Directors of the Company at such
time as Elan's ownership of Common Stock exceeds the Beneficial Ownership
Threshold (as determined pursuant to this paragraph (d)), Mr. Groom shall be the
Elan Designee. Within five business days following such designation, the Company
shall cause the Elan Designee, if not then a member of the Company's Board of
Directors, to be appointed to the Company's Board of Directors. Thereafter, so
long as Elan's ownership of Common Stock, as determined pursuant to the
immediately preceding sentence, exceeds the Beneficial Ownership Threshold, a
committee of the Company's Board of Directors (or, if no such committee exists
and the full Board of Directors of the Company performs such function, the full
Board of Directors) shall include the Elan Designee in the slate of nominees
recommended by the Company's Board of Directors to stockholders for election as
a director at each annual meeting of stockholders of the Company. If, as a
result of death, disability, retirement, resignation or removal (with or without
cause) of the Elan Designee, Elan shall be entitled to designate a replacement
director to fill the vacancy created by such death, disability, retirement,
resignation or removal and, within five business days following such
designation, the Company shall cause such Elan Designee to be appointed to the
Company's Board of Directors.

     (e) Upon the request of the Purchaser, the Company agrees that, with
respect to the issuance and sale of Additional Notes by the Company on
Additional Closing Dates, it will cooperate with the Purchaser in good faith to
make such changes to the form of the Additional Notes (including to bifurcate
any Additional Notes into two or more separate securities) in order to minimize,
to the greatest extent possible, any withholding or deduction for future Taxes
which might be required in connection with payments made by the Company under or
with respect to the Securities (including the issuance of Common Stock upon
conversion of the Securities), so long as any such change does not materially
adversely affect the Company or delay any Additional Closing Date.

     (f) In the event that the Company exercises its option to issue License
Shares on any License Share Issuance Date pursuant to either of clauses
10.1.1(3) or (4) of the License Agreement and the issuance of such License
Shares to Elan or its Affiliates would require a filing by the Company under the
HSR Act, the Company shall, as soon as practicable prior to such License Share
Issuance Date and, in any event, use all 


<PAGE>
                                      -43-


commercially reasonable efforts to prepare and file or cause to be filed such
required filing on a timely basis in order that the waiting period under the HSR
Act shall expire on or before such License Share Issuance Date.

     Elan is intended to be a third-party beneficiary of the covenants set forth
in this Section 13.


     SECTION 14. Covenants of Elan.

     (a) Elan agrees that, until the [ * * * ] of the Initial Closing Date, it
shall not, and shall not permit any of its Affiliates to, directly or
indirectly, without the prior written consent of the Company, sell, offer to
sell, contract to sell, grant any option to purchase or otherwise transfer or
dispose of ("Transfer"), the Shares, the Conversion Shares, the License Shares
or the Securities; provided that Elan may Transfer the Shares, the Conversion
Shares, the License Shares and the Securities to any of its Affiliates and any
Affiliate of Elan may Transfer the Shares, the Conversion Shares, the License
Shares and the Securities to Elan or to any other Affiliate of Elan, subject to
Elan's agreements set forth in Section 4(b) hereof.

     For purposes of this Agreement, except as otherwise expressly provided
herein, the term "Affiliate" shall mean, with respect to any specified person or
entity, any other person or entity controlling, controlled by, or under common
control with such specified person or entity. For purposes of this definition,
"control" means the possession, directly or indirectly, of the power to direct
or cause the direction of the management and policies of a person or entity,
whether through the ownership of voting securities, by contract or otherwise;
and the terms "controlling" and "controlled" have meanings correlative of the
foregoing.

     (b) Except for Transfers between or among Elan and its Affiliates, as
permitted by Section 14(a) hereof, Elan agrees that if, at any time after the
date hereof, it or any of its Affiliates (each, an "Offeror") shall desire to
Transfer all or any part of the Securities owned by it for cash, the Offeror
shall first submit to the Company a notice (the "Notice") which shall set forth
a reasonably detailed description of the price and the terms of the proposed
Transfer and shall contain an irrevocable offer to the Company to sell to the
Company all, but not less than all, of the Securities to be Transferred at such
price and on such terms. At any time within 10 days after the Notice is given,
the Company may accept the offer made to 


<PAGE>
                                      -44-


it in the Notice by furnishing written notice to the Offeror and may purchase
not less than all of the Securities offered at the price and upon the terms
specified in the Notice by delivering such price to the Offeror, by wire
transfer in immediately available funds to an account designated in the Notice,
against delivery of the promissory note or notes evidencing such Securities. If,
at the end of such 10-day period, the offer contained in the Notice has not been
accepted with respect to all Securities proposed to be Transferred, the Offeror
shall have 60 days in which to Transfer all such Securities to a third party, at
a price not less than [* * *] of the price, and on terms not materially
different from the terms, in each case, set forth in the Notice. If, at the end
of such 60-day period, the Offeror has not completed such Transfer, all
restrictions on Transfer of such Securities set forth in this Section 14(b)
shall again be in effect.

     (c) Except as otherwise set forth in this paragraph (c), Elan agrees that,
until the [ * * * ] of the Initial Closing Date, it shall not, and shall not
permit any of its Affiliates to, without the consent of the Company:

          (i) acquire, offer to acquire, or agree to acquire, directly or
     indirectly, by purchase or otherwise, beneficial ownership (as defined
     under Rule 13d-3 under the Exchange Act) of any Common Stock, any
     securities which at such time are convertible or exchangeable into or
     exercisable for shares of Common Stock, or any direct or indirect rights to
     acquire any Common Stock or any securities which at such time are
     convertible or exchangeable into or exercisable for shares for Common
     Stock, if, after giving effect to any such acquisition, Elan would be the
     beneficial owner (as defined under Rule 13d-3 under the Exchange Act) of
     more than 25.0% of the outstanding Common Stock, on a fully diluted basis;

          (ii) make, or in any way participate, directly or indirectly, in any
     "solicitation" of "proxies" to vote (as such terms are used in the rules of
     the SEC) or seek to advise or influence any person or entity with respect
     to the voting of any Voting Stock of the Company;

          (iii) make any public announcement with respect to, or submit a
     proposal for, or offer of (with or without conditions) any extraordinary
     transaction involving the Company or any of its securities or assets;


<PAGE>
                                      -45-


          (iv) form, join or in any way participate in a Group (as defined
     below) in connection with any of the foregoing;

          (v) take any action that could reasonably be expected to require the
     Company to make a public announcement regarding the possibility of any of
     the events described in clauses (i) and (ii) above; or

          (vi) request that the Company, directly or indirectly, amend or waive
     any provision of this paragraph (c).

     Notwithstanding the foregoing, this paragraph (c) shall in no way limit or
otherwise restrict or impair the ability of Elan and its Affiliates to convert
the Securities in accordance with their terms. This provision shall terminate
and be of no further force and effect upon the acquisition of, or public
announcement of an intent to acquire, beneficial ownership (as defined under
Rule 13d-3 under the Exchange Act) by any person or group of related persons for
purposes of Section 13(d) of the Exchange Act ("Group") of more than [* * *]% of
the outstanding Common Stock. For purposes of clause (i) of this paragraph (c),
any securities of the Company beneficially owned (as defined under Rule 13d-3
under the Exchange Act) by Elan or any of its Affiliates and acquired pursuant
to this Agreement, the License Agreement or upon conversion of the Securities,
or which are beneficially owned (as defined under Rule 13d-3 under the Exchange
Act) by Elan or any of its Affiliates as a result of their ownership of the
Securities, shall not be counted unless Elan or any of its Affiliates shall
beneficially own (as defined under 13d-3 under the Exchange Act) any other
securities of the Company that are acquired other than pursuant to this
Agreement, the Stock Purchase Agreement, the License Agreement or the
Securities. Notwithstanding this paragraph (c), at any time on or after [ * * *
] of the Initial Closing Date, Elan and its Affiliates may communicate with a
committee of the Company's then independent directors regarding a negotiated
acquisition of all, but not less than all, of the Common Stock then outstanding.
Such committee of independent directors may, in its sole discretion, refuse any
proposal from Elan or its Affiliates regarding a negotiated acquisition. Upon
such refusal, Elan and its Affiliates shall continue to be subject to the
limitations set forth in this paragraph (c) until [ * * * ] of the Initial
Closing Date. For purposes of this paragraph (c), "independent directors" shall
mean those directors of the Company who are 


<PAGE>
                                      -46-


not directors, officers or Affiliates of Elan or its Affiliates.

     (d) Elan agrees that, within 10 days following a Change of Control of Elan
occurring prior to [ * * * ], Elan will notify the Company in writing of such
Change of Control (the "Elan Change of Control Notice") and the Company may, at
its option, not later than the 10th day following receipt of such Elan Change of
Control Notice (the "Purchase Election Date"), notify Elan of the Company's
irrevocable election to purchase, no earlier than 10 days and no later than 20
days following such election, all, but not less than all, of the Shares, the
Conversion Shares, the License Shares and the shares of Common Stock (the
"Initial Shares") purchased by the Purchaser pursuant to the Stock Purchase
Agreement, dated as of September 30, 1998, by and between the Company and the
Purchaser (the "Stock Purchase Agreement"), in each case, owned by Elan and its
Affiliates on the date of such Change of Control, at a per share purchase price
equal to the greater of [ * * * ]; provided, however, that, as a condition to
such repurchase, the Company shall repurchase all, but not less than all, of the
Securities then owned by Elan and it Affiliates pursuant to the terms of such
Securities. Elan agrees that it will not, and will cause its Affiliates not to,
convert any Security after the date of the Change of Control of Elan and prior
to the later of (x) the receipt of a notice from the Company of its election to
purchase and (y) the Purchase Election Date.

     For purposes of this paragraph (d), a "Change of Control" of Elan shall be
deemed to have occurred at such time as (i) any other person or Group becomes
the beneficial owner (as defined under Rule 13d-3 under the Exchange Act),
directly or indirectly, of 50.0% or more of the total Voting Stock (as defined
below) of Elan, (ii) there shall be consummated any consolidation or merger of
Elan in which Elan is not the continuing or surviving corporation or pursuant to
which the Voting Stock of Elan would be converted into cash, securities or other
property, other than a merger or consolidation of Elan in which the holders of
the Voting Stock of Elan outstanding immediately prior to the consolidation or
merger hold, directly or indirectly, at least a majority of all Voting Stock of
the continuing or surviving corporation immediately after such consolidation or
merger or (iii) during any period of two consecutive years, individuals who at
the beginning of such period constituted the Board of Directors of Elan
(together with any new directors whose election by such Board of Directors or
whose nomination for election by the shareholders of Elan has been approved by a
majority of the directors then still in office 


<PAGE>
                                      -47-


who either were directors at the beginning of such period or whose election or
recommendation for election was previously so approved) cease to constitute a
majority of the Board of Directors of Elan. The term "Voting Stock" means stock
of any class or classes, however designated, having general voting power under
ordinary circumstances to elect a majority of the board of directors, managers
or trustees of Elan, other than stock having such powers only by reason of the
occurrence of a contingency.

     (e) In the event that the Company exercises its option to issue License
Shares on any License Share Issuance Date pursuant to either of clauses
10.1.1(3) or (4) of the License Agreement and the issuance of such License
Shares to Elan or its Affiliates would require a filing by Elan under the HSR
Act, Elan shall use all commercially reasonably efforts to prepare and file or
cause to be filed such required filing on a timely basis in order that the
waiting period under the HSR Act shall expire on or before such License Share
Issuance Date. Subject to compliance by the Company with the provisions of
Section 13(f) hereof, Elan agrees that any License Share Issuance Date may be
postponed until the expiration or, if earlier, the termination of the waiting
period under HSR Act applicable to the filing thereunder made by Elan and, if
required, the Company.


     SECTION 15. Notices. Any notices or other communications required or
permitted hereunder shall be sufficiently given if delivered personally or sent
by nationally recognized overnight delivery service or facsimile (receipt
confirmed) addressed as follows or to such other address of which the parties
may have given written notice:

                    (i)    if to the Company, to:

                           Ligand Pharmaceuticals Incorporated
                           10275 Science Center Drive
                           San Diego, California  92121
                           Attn:  General Counsel
                           Fax No.:  (619) 550-1825

                           with a copy to:

                           Brobeck, Phleger & Harrison LLP
                           550 West C Street, Suite 1300
                           San Diego, California  92101-3532
                           Attn:  Faye H. Russell, Esq.
                           Fax No.:  (619) 234-3848


<PAGE>
                                      -48-


                   (ii) if to the Purchaser, to:

                           Elan International Services, Ltd.
                           102 St. James Court
                           Flatts Smiths FL 04
                           Bermuda
                           Attn:  President
                           Fax No.:  (441) 292-2224

                           with a copy to:

                           Cahill Gordon & Reindel
                           80 Pine Street
                           New York, New York  10005
                           Attn:  William M. Hartnett, Esq.
                           Fax No.:  (212) 269-5420

                  (iii) if to Elan, to:

                           Elan Corporation, plc
                           Lincoln House
                           Lincoln Place
                           Dublin 2, Ireland
                           Attn:  William F. Daniel
                           Fax No.:  353-1-709-4000

                           with a copy to:

                           Cahill Gordon & Reindel
                           80 Pine Street
                           New York, New York  10005
                           Attn:  William M. Hartnett, Esq.
                           Fax No.:  (212) 269-5420

          (iv) (a) on the date delivered, if delivered by facsimile or
     personally or (b) on the day after the notice is delivered into the
     possession and control of a nationally recognized overnight delivery
     service, duly marked for delivery to the receiving party.


     SECTION 16. Successors and Assigns. This Agreement shall bind and inure to
the benefit of the parties hereto and their respective successors and assigns;
provided that no party may assign its rights or obligations hereunder without
the prior written consent of the other parties. Notwithstanding this Section 16,
each of the Purchaser and Elan may assign any of its rights and obligations
hereunder to any of its Affiliates, subject to its agreements set forth in
Section 4 of this 


<PAGE>
                                      -49-


Agreement; provided, further, that the Company may assign its obligations
hereunder in connection with the transfer or sale of all or substantially all of
its assets or in the event of its merger or consolidation with or into another
entity, in each case, in a transaction in which the Company is not the surviving
entity. Any assignment in contravention of this Section 16 shall be void. No
assignment shall release the Purchaser, Elan or the Company from any obligation
or liability under this Agreement unless expressly agreed to by the
non-assigning parties.


     SECTION 17. Entire Agreement; Amendments. This Agreement and the other
writings referred to herein or delivered pursuant hereto contain the entire
understanding and agreement between the parties hereto with respect to the
subject matter hereof and supersedes all prior oral and written and all
contemporaneous oral negotiations, commitments and understandings between such
parties, including, but not limited to, the Letter of Intent. This Agreement may
be amended only by a written amendment executed by both parties.


     SECTION 18. Severability. Any provision of this Agreement which is invalid,
illegal or unenforceable in any jurisdiction shall, as to that jurisdiction, be
ineffective to the extent of such invalidity, illegality or unenforceability,
without affecting in any way the remaining provisions hereof in such
jurisdiction or rendering that or any other provision of this Agreement invalid,
illegal or unenforceable in any other jurisdiction.


     SECTION 19. Expenses. Except as otherwise expressly provided herein, the
Purchaser, Elan and the Company will pay the respective fees and expenses
(including, without limitation, legal and accounting fees and expenses) incurred
by each of them in connection with the transactions contemplated hereby.


     SECTION 20. Survival of Representations and Warranties. All representations
and warranties made in this Agreement or any other instrument or document
delivered in connection herewith or therewith, shall survive the execution and
delivery hereof or thereof until December 31, 2001.


     SECTION 21. Waiver. No failure or delay on the part of a party hereto in
exercising any right, power or remedy hereunder shall operate as a waiver
thereof; nor shall any sin-


<PAGE>
                                      -50-


gle or partial exercise of any such right, power or remedy preclude any other or
further exercise thereof or the exercise of any other right, power or remedy
hereunder.


     SECTION 22. Further Assurances. From and after the date of this Agreement,
upon the reasonable request of one party hereto, the other party hereto shall
execute and deliver such instruments, documents and other writings as may be
necessary or desirable to confirm and carry out and to effectuate fully the
intent and purposes of this Agreement.


     SECTION 23. GOVERNING LAW. THE VALIDITY AND INTERPRETATION OF THIS
AGREEMENT, AND THE TERMS AND CONDITIONS SET FORTH HEREIN SHALL BE GOVERNED BY
AND CONSTRUED IN ACCORDANCE WITH THE LAWS OF THE STATE OF NEW YORK APPLICABLE TO
CONTRACTS MADE AND TO BE PERFORMED WHOLLY THEREIN, WITHOUT GIVING EFFECT TO ANY
PROVISIONS THEREOF RELATING TO CONFLICTS OF LAW.


     SECTION 24. Section Headings. The section headings are for the convenience
of the parties and in no way alter, modify, amend, limit, or restrict the
contractual obligations of the parties.


     SECTION 25. Counterparts. This Agreement may be executed in one or more
counterparts, each of which shall be deemed to be an original, but all of which
shall be one and the same document.




<PAGE>
                                      -51-


     IN WITNESS WHEREOF, this Agreement has been duly executed under seal by the
parties hereto and delivered as of the date first above written.

                        LIGAND PHARMACEUTICALS
                          INCORPORATED


                        By: /s/ William L. Respess
                            -------------------------------------
                            Name:   William L. Respess
                            Title:  Senior Vice President, General
                                    Counsel Government Affairs


                        ELAN INTERNATIONAL SERVICES, LTD.


                        By:  /s/ Kevin Insley
                             ------------------------------------
                             Name:   Kevin Insley
                             Title:  President and Chief
                                     Financial Officer



For purposes of Section 1(c), 2(c), 
   4(b), 10, 11, 13 and 14 only:


ELAN CORPORATION, PLC


By:  /s/ Liam Daniel                                        
     ------------------------------------
Name:  Liam Daniel
Title: Group Vice President, Finance






                                                                       EXHIBIT 2







                        CONFIDENTIAL TREATMENT REQUESTED





                             Dated November 9, 1998





                              ELAN CORPORATION, plc

                                       AND

                       LIGAND PHARMACEUTICALS INCORPORATED





                    DEVELOPMENT, LICENCE AND SUPPLY AGREEMENT









<PAGE>







                                    CONTENTS

                                                                           Page

CLAUSE 1 - PRELIMINARY.......................................................3

CLAUSE 2 - THE LICENCE.......................................................8

CLAUSE 3 - INTELLECTUAL PROPERTY............................................10

CLAUSE 4 - LIGAND COMPETING PRODUCTS........................................15

CLAUSE 5 - DEVELOPMENT OF THE PRODUCT.......................................15

CLAUSE 6 - PROJECT TEAM AND PROJECT MANAGEMENT..............................17

CLAUSE 7 - REGISTRATION OF THE PRODUCT......................................18

CLAUSE 8 - MARKETING AND PROMOTION OF THE PRODUCT...........................19

CLAUSE 9 - SUPPLY OF THE  PRODUCT...........................................20

CLAUSE 10 - FINANCIAL PROVISIONS............................................25

CLAUSE 11 - PAYMENTS, REPORTS AND AUDITS....................................27

CLAUSE 12 - DURATION AND TERMINATION........................................29

CLAUSE 13 - CONSEQUENCES OF TERMINATION.....................................30

CLAUSE 14 - WARRANTY AND INDEMNITY..........................................31

CLAUSE 15 - ADVERSE EVENTS AND PRODUCT RECALL...............................34

CLAUSE 16 - MISCELLANEOUS PROVISIONS........................................35



SCHEDULE 1    ELAN PATENT RIGHTS

SCHEDULE 2    SPECIFICATIONS

SCHEDULE 3    ELAN CLINICAL TRIALS







                                      -2-
<PAGE>
THIS AGREEMENT is made on November 9, 1998.

BETWEEN:

(1)  ELAN CORPORATION, PLC, a company incorporated in Ireland having its
     registered office at Lincoln House, Lincoln Place, Dublin 2, Ireland
     ("ELAN") and

(2)  LIGAND PHARMACEUTICALS INCORPORATED, a company organized under the laws of
     Delaware, with offices at 10275 Science Center Drive, San Diego, California
     92121, United States of America ("LIGAND").

RECITALS:

A.   ELAN is beneficially entitled to the use of various patents, including the
     ELAN PATENTS, which have been granted or are pending under the
     International Convention in relation to the development and production of
     drug specific dosage forms for pharmaceutical products and processes.

B.   ELAN is knowledgeable in the development of drug specific dosage forms and
     has developed a unique range of delivery systems designed to provide newer
     and better formulations of medicaments.

C.   LIGAND is desirous of entering into a licensing agreement with ELAN by
     virtue of which it will be free to have manufactured in accordance with the
     terms of this Agreement and to market the PRODUCT in the TERRITORY without
     infringing any of the ELAN INTELLECTUAL PROPERTY rights held by ELAN.

D.   ELAN is prepared to licence the ELAN PATENTS in the TERRITORY to LIGAND and
     ELAN is prepared to supply the PRODUCT to LIGAND.

E.   ELAN and LIGAND are desirous of entering into an agreement to give effect
     to the arrangements described at Recitals C and D.

NOW IT IS HEREBY AGREED AS FOLLOWS:

                             CLAUSE 1 - PRELIMINARY

Definitions: In this Agreement unless the context otherwise requires:

     1.1.1   AFFILIATE shall mean any corporation or entity controlling or
             controlled or under common control with ELAN or LIGAND, as the case
             may be. For the purposes of this Agreement, "control" shall mean
             the direct or indirect ownership of more than 50% of the issued
             voting shares or other voting rights of the subject entity to elect
             directors, or if not meeting the preceding criteria, any entity
             owned or controlled by or owning or controlling at the maximum
             control or ownership right permitted in the country where such
             entity exists.



                                      -3-
<PAGE>

     1.1.2   cGCP, cGMP, cGLP shall mean respectively current Good Clinical
             Practice, as defined in the Good Clinical Practice Guideline as
             published in 62 Federal Register 90 (May 9, 1997), and current Good
             Manufacturing Practice and current Good Laboratory Practice as
             defined in the FFDCA.

     1.1.3   CFR shall mean the US Code of Federal Regulations 21, as amended
             from time to time.

     1.1.4   CLOSING PRICE shall mean, with respect to the Common Stock of
             LIGAND on any trading day, the last reported per share sales price
             on [**********] as reported by the NASDAQ National Market or, if
             the Common Stock is listed on a United States securities exchange,
             the closing per share sales price, regular way, on [**********] on
             the principal United States securities exchange on which the Common
             Stock is traded, or if no such sale takes place on [**********],
             the average of the closing bid and asked prices on [**********].

     1.1.5   CMC SECTION shall mean the chemistry, manufacturing, and controls
             section of the NDA in the USA as defined in CFR Section 314.50 (1),
             as may be amended from time to time, and/or its equivalent in
             foreign NDAs.

     1.1.6   COMPOUND shall mean the active drug substance morphine and its
             salts.

     1.1.7   CONVERTIBLE NOTE shall mean the Zero Coupon Convertible Senior Note
             due 2008 of November 9 executed by Ligand Pharmaceuticals
             Incorporated and issued pursuant to the PURCHASE AGREEMENT.

     1.1.8   DMF shall mean Drug Master File, as defined in the CFR Section
             314.420 and/or its equivalent in the other countries of the
             TERRITORY.

     1.1.9   EFFECTIVE DATE shall mean September 30, 1998.

     1.1.10  ELAN shall mean Elan Corporation, plc and any of its AFFILIATES.

     1.1.11  ELAN IMPROVEMENTS shall mean any improvement or enhancement to the
             ELAN PATENTS that is created, conceived or invented during the
             INITIAL PERIOD which ELAN is free to license and which are not
             subject to contractual obligations with any third party,.

     1.1.12  ELAN INTELLECTUAL PROPERTY shall mean the ELAN PATENTS and/or the
             ELAN KNOW-HOW and shall include the improvements made by LIGAND as
             referred to in Clause 3.1.3 to the extent such improvements relate
             to the PRODUCT.

     1.1.13  ELAN KNOW-HOW shall mean all knowledge, information, trade secrets,
             data and expertise relating to the PRODUCT and which is not
             generally known to the public, owned or licensed by ELAN as of the
             EFFECTIVE DATE, or developed by ELAN whether before or during the
             INITIAL PERIOD relating to the 



                                      -4-
<PAGE>

             PRODUCT, and which ELAN is free to license and which is not
             subject to contractual obligations with any third party, whether
             or not covered by any patent, copyright, design patent,
             trademark, trade secret or other industrial or any intellectual
             property rights.

             In the event that ELAN acquires or merges with a third party
             entity, ELAN KNOW-HOW shall not include any know-how to the
             extent that such know-how relates to a product containing the
             COMPOUND which has been approved for marketing or is in
             development by the said third party entity. For the avoidance
             of doubt, the occurrence of any such acquisition or merger
             shall not affect the licence of the ELAN KNOW-HOW granted to
             LIGAND hereunder.

             For the avoidance of doubt, ELAN KNOW-HOW shall exclude any
             know-how owned, licenced or controlled by [**********]
             (collectively, the "EXCLUDED KNOW-HOW").

             For the avoidance of doubt, ELAN KNOW-HOW shall include any
             know-how relating to the PRODUCT owned, licenced or controlled
             by [**********], if any.

     1.1.14  ELAN PATENTS shall mean all patents and patent applications listed
             in Schedule 1. ELAN PATENTS shall also include all continuations,
             continuations-in-part, divisionals, ELAN IMPROVEMENTS, and any
             patents issuing thereon, and re-issues or re-examinations of such
             patents and extensions of any patents licenced hereunder.
             Extensions of patents shall include extensions under the U.S.
             Patent Term Restoration Act.

             For the avoidance of doubt, ELAN PATENTS shall exclude any
             patents owned, licenced or controlled by [**********] (the
             "EXCLUDED PATENTS").

             For the avoidance of doubt, ELAN PATENTS shall include any
             patents relating to the PRODUCT owned, licenced or controlled
             by [**********], if any.

             In the event that ELAN acquires or merges with a third party
             entity, ELAN PATENTS shall not include any patent rights of
             such third party entity to the extent that such patent rights
             relate to a product containing the COMPOUND which has been
             approved for marketing or is in development by the said third
             party entity. For the avoidance of doubt, the occurrence of
             any such acquisition or merger shall not affect the licence of
             the ELAN PATENTS granted to LIGAND hereunder.

     1.1.15  ELAN TRADEMARK shall mean the trademark, Morphelan(TM).

     1.1.16  ENFORCEMENT PROCEEDINGS shall mean the proceedings referred to in
             Clause 3.3.2.

     1.1.17  EU shall mean the Member States of the European Union, as same may
             change from time to time in terms of Member States.



                                      -5-
<PAGE>

     1.1.18  EX WORKS shall have the meaning as such term is defined in the ICC
             Incoterms, 1990, International Rules for the Interpretation of
             Trade Terms, ICC Publication No. 460.

     1.1.19  FDA shall mean the United States Food and Drug Administration or
             any other successor agency whose approval is necessary to market
             the PRODUCT in the United States of America and/or its foreign
             equivalents in any other country of the TERRITORY.

     1.1.20  FFDCA shall mean the US Federal Food, Drug and Cosmetic Act, and
             the regulations promulgated thereunder, as may be amended from time
             to time.

     1.1.21  FINANCE AGREEMENTS means the PURCHASE AGREEMENT and CONVERTIBLE
             NOTE entered into between Elan International Services, Ltd., Elan
             Corporation, plc and Ligand Pharmaceuticals Incorporated.

     1.1.22  FULLY ALLOCATED COST shall mean, with respect to a party, the fully
             allocated cost which is the sum total of all production related
             costs for the PRODUCT including direct labour, direct materials and
             supplies, variable labour, reasonable overhead and allocable
             administration, quality control, quality assurance and other costs;
             such costs to be calculated in accordance with a [**********].

     1.1.23  INITIAL PERIOD shall mean the initial period of this Agreement, as
             more fully described in Clause 12.1.

     1.1.24  IN MARKET shall mean the sale of the PRODUCT by LIGAND or by a
             distributor of LIGAND to an unaffiliated third party including but
             not limited to a wholesaler, chain store, managed care
             organisation, hospital, pharmacy or governmental agency.

     1.1.25  LAUNCH STOCKS shall mean the quantities of stocks of the PRODUCT
             required by LIGAND in relation to the launch of the PRODUCT
             following NDA APPROVAL in each country of the TERRITORY, as more
             fully described in Clause 9.6.

     1.1.26  LIGAND shall mean Ligand Pharmaceuticals Incorporated and any of
             its AFFILIATES.

     1.1.27  NDA shall mean the New Drug Application or any other application
             for regulatory approval which ELAN intends to file and any
             supplements or amendments thereto which LIGAND may file, for the
             PRODUCT in the United States of America and its foreign equivalent
             in Canada.

     1.1.28  NDA APPROVAL shall mean the final approval to market the PRODUCT in
             the United States of America and/or its foreign equivalent in
             Canada and in the case 



                                      -6-
<PAGE>

             of Clause 2.2. its foreign equivalent in the applicable Member 
             States of the EU (excluding Ireland and the United Kingdom).

     1.1.29  NSP shall, subject to the provisions of Clause 10.3.7, mean in the
             case of PRODUCT sold by LIGAND or by a distributor of LIGAND, that
             sum determined by [**********] by LIGAND in accordance with
             LIGAND's standard accounting principles, expenses incurred by
             LIGAND under Clause 3.2.2 if, as a result thereof, a patent is
             granted to ELAN and a maximum deduction of [**********] to cover
             the following:-

             (a)      customs duties or other taxes (excluding income or
                      corporation tax), directly related to the sale of the
                      PRODUCT which are paid by LIGAND;

             (b)      a discount from the gross sales proceeds to cover
                      such normal costs as are incurred by LIGAND in
                      respect of transport, shipping insurance, returns,
                      rebates, allowances for bad debt actually taken, and
                      discounts directly related to the sale of the
                      PRODUCT.

     1.1.30  PRODUCT shall mean the [**********] of the once-daily oral dosage
             microparticulate formulation being developed and manufactured by
             ELAN containing the COMPOUND as its primary active ingredient.

     1.1.31  PROJECT TEAM shall mean the group to be established pursuant to
             Clause 6.

     1.1.32  PURCHASE AGREEMENT shall mean the Securities Purchase Agreement,
             dated as of November 6, 1998 by and among Elan Corporation plc,
             Elan International Services, Ltd. and Ligand Pharmaceuticals
             Incorporated.

     1.1.33  SPECIFICATIONS shall mean the specifications for the PRODUCT set by
             the parties for the NDA, as well as such other specifications such
             as additional specifications for the PRODUCT as may be agreed by
             the parties in writing.

     1.1.34  TECHNOLOGICAL COMPETITOR shall mean [**********].

     1.1.35  TERRITORY shall mean the United States of America and its
             territories and Canada.

     1.1.36  $ shall mean United States Dollars.

     1.1.37  US or USA shall mean the United States of America.

Interpretation:   In this Agreement:

     1.2.1   the singular includes the plural and vice versa, the masculine
             includes the feminine and vice versa and references to natural
             persons include corporate bodies, partnerships and vice versa.



                                      -7-
<PAGE>

     1.2.2   any reference to a Clause or Schedule, unless otherwise
             specifically provided, shall be respectively to a Clause or
             Schedule of this Agreement.

     1.2.3   the headings of this Agreement are for ease of reference only and
             shall not affect its construction or interpretation.

                             CLAUSE 2 - THE LICENCE

2.1  Licence to LIGAND:

     2.1.1   Subject to the terms of this Agreement, ELAN hereby grants to
             LIGAND and LIGAND hereby accepts for the INITIAL PERIOD an
             exclusive licence (even as to ELAN) of the ELAN INTELLECTUAL
             PROPERTY to import, use, offer for sale and sell the PRODUCT in the
             TERRITORY; provided that LIGAND shall grant back to ELAN a non
             exclusive royalty-free license to make, use and co-promote the
             PRODUCT in the TERRITORY so as to enable ELAN to perform its
             obligations pursuant to this Agreement, to enable ELAN to exercise
             its rights as set forth in Clause 2.2.1, and for the avoidance of
             doubt to conduct further research, development and manufacturing
             within the TERRITORY with regard to ELAN's commercialisation of the
             PRODUCT outside the TERRITORY.

     2.1.2   [**********] shall [**********]; provided, however, LIGAND can
             appoint distributors or wholesalers for the PRODUCT in any country
             of the TERRITORY to perform those activities which are within
             customary boundaries of pharmaceutical product distribution for the
             sole purpose of delivering the PRODUCT to retailers for final
             commercial sale to patients without such prior consent.

     2.1.3   ELAN covenants that neither ELAN nor any of its AFFILIATES will
             prosecute any suit against LIGAND regarding any EXCLUDED KNOW-HOW
             and EXCLUDED PATENTS by reason of LIGAND exercising its rights
             under this Agreement. ELAN further covenants that after the
             EFFECTIVE DATE it will not incorporate any know-how or patented
             technology of any third party into the PRODUCT without the ability
             to licence such know-how or patented technology without LIGAND's
             written permission.

2.2  Co-Promotion of the PRODUCT:

     ELAN    

     2.2.1   For the period from the EFFECTIVE DATE up until [**********] in
             each country of the TERRITORY, ELAN shall have [**********] to
             co-promote the PRODUCT in such country of the TERRITORY for
             [**********] on other terms to be agreed in good faith between the
             parties and having regard to standard industry practices in such
             country of the TERRITORY.

     LIGAND  



                                      -8-
<PAGE>

     2.2.2   For the period from the EFFECTIVE DATE up until [**********] in
             each Member State of the EU (excluding Ireland and the United
             Kingdom), whether on an individual approval basis or through the
             European decentralised procedure, LIGAND shall have a [**********]
             to co-promote the PRODUCT in such Member State of the EU for
             [**********] on other terms to be agreed in good faith between the
             parties (including supply provisions) and having regard to standard
             industry practices in such Member State of the EU; provided that
             LIGAND has an established sales force in [**********] in such
             Member State.

2.3  Exercise of Co-Promotion Option

     2.3.1   To exercise the option granted to ELAN in Clause 2.2.1, ELAN shall
             deliver written notice of exercise to LIGAND prior to the end of
             such option period described in Clause 2.2.1. Thereafter, the
             parties shall diligently attempt to reach an agreement of the terms
             and conditions governing the co-promotion of the PRODUCT for
             [**********] in the TERRITORY. If the parties are unable to reach
             in good faith such an agreement within [*****] of the receipt of
             such notice, either party may seek arbitration pursuant to Clause
             2.3.3.

     2.3.2   To exercise the option granted to LIGAND in Clause 2.2.2, LIGAND
             shall deliver written notice of exercise to ELAN prior to the end
             of such option period described in Clause 2.2.2, specifying which
             Member State or Member States in the EU LIGAND intends to
             co-promote the PRODUCT. Thereafter, the parties shall diligently
             attempt to reach an agreement of the terms and conditions governing
             the co-promotion of the PRODUCT for [**********] in such Member
             State or Member States, as the case may be. If the parties are
             unable to reach in good faith such an agreement within [*****] of
             the receipt of such notice, either party may seek arbitration
             pursuant to Clause 2.3.3.

     2.3.3   In the event that the parties are unable to agree upon the terms
             for co-promotion of the PRODUCT by either party as set out at
             Clauses 2.2.1. and 2.2.2. above, the parties shall appoint an
             arbitrator who is technically knowledgeable in the pharmaceutical
             industry to choose either ELAN's last proposed terms or LIGAND's
             last proposed terms for the co-promotion on the basis of which
             terms he determines to be closer to standard industry practice in
             the relevant country or Member State, as the case may be. LIGAND
             and ELAN each shall be responsible for [**********] of the total
             costs of arbitration incurred in connection with this Clause 2.





                                      -9-
<PAGE>



                        CLAUSE 3 - INTELLECTUAL PROPERTY

3.1 Ownership of ELAN INTELLECTUAL PROPERTY:

     3.1.1   ELAN shall remain the sole owner of the ELAN INTELLECTUAL PROPERTY.

     3.1.2   ELAN shall be entitled to use the ELAN INTELLECTUAL PROPERTY, and
             all technical, clinical and other data, generated by ELAN and/or by
             LIGAND pursuant to this Agreement in connection with:

             (a)      ELAN's commercial arrangements otherwise than in relation
                      to the PRODUCT; and

             (b)      ELAN's promotion of the PRODUCT for [**********] only
                      in the event that ELAN exercises the option set out
                      in Clause 2.2.1.; and

             (c)      the commercialization of the PRODUCT in any countries
                      outside of the TERRITORY or those which cease to be
                      part of the TERRITORY; and in the TERRITORY following
                      termination of this Agreement; and

     3.1.3   In consideration for the licences granted by ELAN pursuant to this
             Agreement, any improvements relating to the ELAN INTELLECTUAL
             PROPERTY, including improvements relating to the formulation,
             process or manufacturing of the PRODUCT, made solely by LIGAND, its
             officers, servants, agents, and pursuant to the conduct of clinical
             trials conducted by or on behalf of LIGAND, its officers, servants,
             agents, during the INITIAL PERIOD shall be assigned by LIGAND to
             ELAN and shall form part of the ELAN INTELLECTUAL PROPERTY licenced
             to LIGAND pursuant to Clause 2.1.

3.2  Filing and maintenance of patents:

     3.2.1   ELAN will be entitled but not obliged, at its own expense, to file
             and prosecute ELAN PATENTS; to determine the patent filing strategy
             in relation to same at its sole discretion and upon grant of any
             letters patent of the ELAN PATENTS, to maintain such letters patent
             in force.

     3.2.2   Should ELAN elect not to file or not to continue the maintenance or
             prosecution of any case under the ELAN PATENTS in the TERRITORY, it
             shall at LIGAND's request and at LIGAND's expense and within the
             rules and regulations of the appropriate patent issuing office
             attempt to secure a proprietary position for LIGAND provided,
             however, that ELAN shall not be obliged to perform such acts in any
             country of the TERRITORY at LIGAND's request where to do so would
             violate any law (statutory or judge-made) or regulations in such
             country. Any such patent applications shall be made in the name of
             ELAN and ownership of such patent applications or patents, if
             granted, shall remain with ELAN and will become part of the ELAN
             PATENTS for the purpose of this Agreement.



                                      -10-
<PAGE>

3.3  Enforcement

     3.3.1   LIGAND and ELAN shall promptly inform the other in writing of any
             alleged infringement or unauthorised use of which it shall become
             aware by a third party of any intellectual property within the ELAN
             INTELLECTUAL PROPERTY and provide such other with any available
             evidence of infringement or unauthorized use.

     3.3.2   ELAN, at its option, shall be entitled to institute enforcement
             proceedings ("ENFORCEMENT PROCEEDINGS") in respect of any
             infringement or unauthorised use of the ELAN INTELLECTUAL PROPERTY.
             LIGAND agrees to provide all reasonable co-operation and assistance
             to ELAN in relation to any such ENFORCEMENT PROCEEDINGS (and agrees
             to be named as a party if legally required) at ELAN's expense. Any
             reasonable fees and costs borne by LIGAND shall be reimbursed by
             ELAN. ELAN shall be entitled to deduct its reasonable expenses in
             relation to such ENFORCEMENT PROCEEDINGS (including reasonable
             attorney's fees and expenses) from any recovery [**********]. ELAN
             and LIGAND each recognise that it is in both parties interest to
             enforce ELAN INTELLECTUAL PROPERTY to the full amount provided by
             law, and neither party shall, except as required by law, knowingly
             make any admission to jeopardise, compromise or otherwise limit the
             scope of such ELAN INTELLECTUAL PROPERTY.

     3.3.3   In the event that ELAN does not want to institute, or to continue
             already instituted, ENFORCEMENT PROCEEDINGS, then LIGAND, using
             attorneys of LIGAND's choosing reasonably acceptable to ELAN, can
             enforce such rights at its own expense. In such event, LIGAND must
             keep ELAN fully and timely informed of the action so as to enable
             ELAN to provide input which LIGAND shall reasonably consider.
             LIGAND [**********] relating to the invalidity, unenforceability or
             non-infringement of the ELAN INTELLECTUAL PROPERTY without ELAN's
             prior written consent. ELAN agrees to provide all reasonable
             co-operation and assistance to LIGAND in relation to any such
             ENFORCEMENT PROCEEDINGS at LIGAND's expense and agrees to be named
             as a party in any ENFORCEMENT PROCEEDINGS. Any reasonable fees and
             costs borne by ELAN shall be reimbursed by LIGAND. In the event
             that LIGAND enforces ELAN INTELLECTUAL PROPERTY in accordance with
             this paragraph, LIGAND shall be entitled to deduct its reasonable
             expenses in relation to such ENFORCEMENT PROCEEDINGS (including
             reasonable attorney's fees and expenses and reimbursements to ELAN)
             from any recovery [**********].

3.4  Defence

     3.4.1   In the event that a claim or proceeding is brought against LIGAND
             or ELAN by a third party alleging that the sale, manufacture, offer
             for sale or use of the PRODUCT infringes the patent rights of such
             a third party in the TERRITORY, LIGAND shall promptly advise ELAN
             of such claim or proceeding and the party 



                                      -11-
<PAGE>

              against whom the claim or proceeding is brought and the other
              party shall meet to discuss in what manner such claim or
              proceeding should be defended. Such discussion shall include,
              among other things, responsibility of defense, financial
              undertaking, cessation of the sale of the PRODUCT and
              modification of the PRODUCT to avoid unauthorised use.

     3.4.2   In the circumstance where (i) LIGAND or ELAN, or both LIGAND and
             ELAN, are sued for infringement of a patent and ELAN is in breach
             of its representation and warranty under Clause 14.13 and (ii) no
             agreement is made by ELAN and LIGAND under Clause 3.4.1 concerning
             a defense, then LIGAND shall defend such action at its expense.
             ELAN shall reasonably cooperate with LIGAND in such defense and
             shall bear its own expenses (including reasonable attorney fees) to
             the extent it participates in the action. LIGAND shall be
             responsible for [**********], except that neither party shall be
             liable for [**********] against the other for [**********] (or, in
             the U.S., as otherwise provided in [**********]) or for any
             [**********] (or, in the U.S., as otherwise provided in
             [**********]) to the third party against the other arising from
             [**********]. LIGAND must keep ELAN fully and timely informed of
             the action, including any offers of settlement made to or by
             LIGAND, so as to enable ELAN to provide input which LIGAND shall
             reasonably consider. LIGAND shall have the right to settle any
             claim against LIGAND based on such patent without ELAN's approval
             [**********]. LIGAND shall have [**********]. If ELAN [**********]
             of a settlement, then ELAN [**********] of such action [**********]
             as and from such date, in which case LIGAND [**********] of any
             award of [**********] (including the legal costs incurred by LIGAND
             up to the date of ELAN [**********] of the action) and shall have
             no obligation to contribute to [**********] (or, in the U.S., as
             otherwise provided in [**********]) or for [**********] (or, in the
             U.S., as otherwise provided in [**********]) arising from
             [**********]. In the case in which ELAN [**********] of an action,
             LIGAND's contribution to an award of [**********] ELAN shall be
             [********************] ELAN and (ii) [**********] LIGAND,
             [**********] by [**********] LIGAND; provided however, that in the
             event that such sum paid by LIGAND to [**********] LIGAND
             [**********] shall be [**********] LIGAND to ELAN. In no event,
             shall ELAN be obliged to make any payment to LIGAND arising from
             any award [**********] ELAN where ELAN has [**********] of an
             action pursuant to this Clause 3.4.2.

     3.4.3.  In the circumstance where (i) LIGAND or ELAN, or both LIGAND and
             ELAN, are sued for infringement of a patent and [**********] of its
             [**********] and (ii) no agreement is made by ELAN and LIGAND under
             Clause 3.4.1 concerning a defense, then LIGAND shall defend such
             action at its expense including the reasonable expenses of ELAN
             (not including ELAN's attorney fees) incurred in cooperating with
             LIGAND in such defense. LIGAND shall be obligated to pay
             [**********] to the third party except that LIGAND shall not be
             obligated to pay [**********] (or, in the U.S., as otherwise
             provided in [**********]) or for [**********] (or, in the U.S., as
             otherwise provided in [**********]) to the 



                                      -12-
<PAGE>

             third party against ELAN arising from [**********]. LIGAND must
             keep ELAN fully and timely informed of the action, including
             offers of settlement made to or by LIGAND, so as to enable ELAN
             to provide input which LIGAND shall reasonably consider. LIGAND
             shall have the right to settle any claim against LIGAND based on
             such patent without ELAN's approval. LIGAND shall have no right
             to settle a claim against ELAN without ELAN's written approval.
             If ELAN [**********] of a settlement, then ELAN shall
             [**********] of such action [**********] as and from such date,
             in which case [**********] to (i) [**********] by LIGAND up to
             the date of ELAN [**********] of the action, and (ii)
             [**********] and LIGAND shall have no obligation to contribute to
             any [**********] (or, in the U.S., as otherwise provided in
             [**********]) or for [**********] (or, in the U.S., as otherwise
             provided in [**********]) arising from [**********] by ELAN.

     3.4.4   In the situation where (i) LIGAND settles an action against LIGAND
             and ceases distribution of the PRODUCT and (ii) ELAN [**********]
             of any claim against ELAN under either Clause 3.4.2 or Clause 3.4.3
             and, if applicable, ELAN is selling the PRODUCT on its own behalf
             or through a distributor in accordance with Clause 2.2.1, then
             LIGAND shall have [**********] to an award of damages against ELAN
             for the manufacture, use or sale of the PRODUCT which is referable
             to the period after LIGAND and/or its distributor ceases
             distribution of the PRODUCT.

     3.4.5   ELAN shall have no liability to LIGAND whatsoever or howsoever
             arising for any losses incurred by LIGAND as a result of having to
             cease selling the PRODUCT or having to defer the launch of selling
             the PRODUCT, whether as a result of a court order or otherwise

3.5  Trademarks

     3.5.1   LIGAND shall be entitled to market the PRODUCT in the TERRITORY
             under the ELAN TRADEMARK.

     3.5.2   ELAN hereby grants to LIGAND a non-exclusive royalty free license
             in the TERRITORY for the INITIAL PERIOD (and thereafter for as long
             as LIGAND continues to import, make or have made, use, offer for
             sale or sell the PRODUCT in the TERRITORY in accordance with the
             provisions of Clause 12.2) to use the ELAN TRADEMARK solely for the
             purposes of exercising its rights and performing its obligations
             under this Agreement and the following provisions shall apply as
             regards the use of the ELAN TRADEMARK by LIGAND:

          (1)  LIGAND shall ensure that each reference to and use of the ELAN
               TRADEMARK by LIGAND is in a manner from time to time approved by
               ELAN and accompanied by an acknowledgement, in a form approved by
               ELAN, that the same is a trademark (or registered trademark) of
               ELAN.



                                      -13-
<PAGE>

          (2)  LIGAND shall not use the ELAN TRADEMARK in any way which might
               materially prejudice its distinctiveness or validity or the
               goodwill of ELAN therein.

          (3)  LIGAND shall not use in relation to the PRODUCT any trademarks
               other than the ELAN TRADEMARK without obtaining the prior consent
               in writing of ELAN, which consent may not be unreasonably
               withheld, and except that LIGAND shall have the right to employ
               in connection with the PRODUCT, the trademark "LIGAND" and the
               tradename "Ligand Pharmaceuticals Incorporated" and such other
               trademarks and tradenames as required by law.

          (4)  LIGAND shall not use in the TERRITORY any trademarks or trade
               names so resembling the ELAN TRADEMARK as to be likely to cause
               confusion or deception.

          (5)  LIGAND shall promptly notify ELAN in writing of any alleged
               infringement of which it becomes aware by a third party of the
               ELAN TRADEMARK and provide ELAN with any applicable evidence of
               infringement.

     3.5.3   ELAN shall, at its expense, file and prosecute applications to
             register and maintain registrations of the TRADEMARK in the
             TERRITORY.

     3.5.4   ELAN will be entitled to conduct all enforcement proceedings
             relating to the ELAN TRADEMARK and shall at its sole discretion
             decide what action, if any, to take in respect of any infringement
             or alleged infringement of the ELAN TRADEMARK or passing-off or any
             other claim or counter-claim brought or threatened in respect of
             the use or registration of the ELAN TRADEMARK. Any such proceedings
             shall be conducted at ELAN's expense and for its own benefit.

             In the event that ELAN fails to take action in respect of any
             infringement or alleged infringement of the ELAN TRADEMARK or
             passing-off or any other claim or counter-claim brought or
             threatened in respect of the use or registration of the ELAN
             TRADEMARK, LIGAND may require ELAN defend such action, at
             LIGAND's expense, when there is evidence of actual mistake,
             confusion, or deception. LIGAND may request ELAN to take action
             in respect of acts it deems likely to cause mistake, confusion or
             deception at LIGAND's expense. If ELAN denies LIGAND's request,
             LIGAND can request an independent attorney skilled in trademark
             law to render an opinion, at LIGAND's expense, with respect to
             whether such acts are likely to cause mistake, confusion or
             deception and if such attorney opines that such acts constitute
             an infringement then ELAN shall take such action at LIGAND's
             expense; provided however that such independent attorney shall
             not be retained by either party in any such subsequent action.
             Any amount remaining after the deduction of any reasonable
             expenses (including reasonable attorney fees and expenses) shall
             be distributed [**********] among 



                                      -14-
<PAGE>

             the parties in which LIGAND shall receive [**********] and ELAN 
             shall receive [**********].

     3.5.5   Except as provided in this Clause 3.5, LIGAND will have no
             ownership rights in respect of the ELAN TRADEMARK or any trade
             names or trademarks used by ELAN in relation to the PRODUCT or of
             the goodwill associated therewith, and LIGAND hereby acknowledges
             that, except as expressly provided in this Agreement, it shall not
             acquire any rights in respect thereof and that all such rights and
             goodwill are, and will remain, vested in ELAN.

             LIGAND shall not, at any time during or after the INITIAL
             PERIOD, challenge or assist others to challenge the ELAN
             TRADEMARK, or the registration thereof or attempt to register
             any trademarks, marks, or trade names confusingly similar to
             the ELAN TRADEMARK.

                      CLAUSE 4 - LIGAND COMPETING PRODUCTS

4.1  LIGAND undertakes [**********] in the TERRITORY during the INITIAL PERIOD
     and for [**********] thereafter.

                      CLAUSE 5 - DEVELOPMENT OF THE PRODUCT

5.1  ELAN shall diligently apply its technical skill and expertise, including
     the ELAN PATENTS and ELAN KNOW-HOW, in the development of the PRODUCT on
     behalf of LIGAND. However, it is acknowledged that pharmaceutical research
     and development incorporates inherent risk in terms of outcomes and, save
     for acts of negligence or omission by ELAN, ELAN shall have no liability to
     LIGAND as a result of any failure or delay of the PRODUCT to obtain the NDA
     APPROVAL in one or more of the other countries of the TERRITORY.

5.2  ELAN and LIGAND hereby confirm that each shall undertake its respective
     part of the development of the PRODUCT as a collaborative effort and that
     the provisions of this Agreement requires that each party diligently
     carries out those tasks assigned to it. Each party shall co-operate with
     the other in good faith particularly with respect to unknown problems or
     contingencies and shall perform its obligations in good faith and in a
     commercially reasonable, diligent and workmanlike manner.

5.3  In the event that LIGAND wishes to have more than [**********] developed
     pursuant to this Agreement, the parties shall negotiate in good faith as to
     the additional costs to be paid to ELAN for such development. The parties
     agree that ELAN's charges to LIGAND for any such work shall be as set out
     in Clause 10.2 of the Agreement.

5.4  ELAN shall be responsible, [**********], for the completion of the clinical
     studies for the PRODUCT listed in Schedule 3 which are currently in
     progress. LIGAND shall be responsible for the cost of all development work
     and/or clinical trials on the PRODUCT in relation to the NDA APPROVAL and
     commercialisation of the PRODUCT in the TERRITORY in addition to such
     ongoing clinical trials but shall have no obligation to 



                                      -15-
<PAGE>

     perform such development, work and/or clinical trials. [**********]. In the
     event that LIGAND decides not to incur any [**********] or [**********] on
     the PRODUCT , the provisions of Clause 7.4 shall be applicable. In relation
     to the conduct of all clinical studies other than those listed in Schedule
     3, ELAN shall be entitled to charge LIGAND for all research, development
     and manufacturing work conducted by ELAN, including the oversight of the
     conduct of such clinical studies by one or more third parties, on the basis
     set forth in Clause 10.2.

5.5  For the [**********] following submission of the NDA in the USA, LIGAND
     shall commit to undertake additional clinical expenditure, including
     [**********] (including FULLY ALLOCATED COST of LIGAND and the sums paid by
     LIGAND to ELAN as referred to in Clause 5.4 above). The objective of the
     programme so conducted shall be to [**********]. LIGAND agrees to carry out
     and complete the clinical efficacy programme to a standard and timeframe
     that LIGAND would otherwise find acceptable for one of its major branded
     products. LIGAND shall keep ELAN informed as to the [**********]. LIGAND
     undertakes that it shall carry out all [**********] to prevailing cGCP and
     cGLP and most specifically in accordance with FDA standards and guidelines.
     In the event that LIGAND does not expend [**********] during the
     [**********] following submission of the NDA in the USA, then, unless
     otherwise agreed in writing between the parties, LIGAND shall pay any
     shortfall between the [**********] and the actual sum expended by LIGAND to
     ELAN, provided however, in the event the FDA notifies ELAN of its refusal
     to grant the NDA submitted by ELAN and LIGAND, after discussion with ELAN,
     determines that it is not commercially viable for LIGAND to incur any
     additional development expenses as provided in Clause 5.4, LIGAND shall
     have no further obligation to expend or remit sums under this Clause 5.5.
     In such event, ELAN shall have the right to terminate this Agreement.
     Thereafter, ELAN shall be entitled to research, develop and commercialise
     the PRODUCT in the TERRITORY. In the event of such termination, all monies
     paid to ELAN by LIGAND pursuant to this Agreement shall not be recoverable
     by LIGAND.

5.6  During the development of the PRODUCT, the parties shall review and agree
     on interim specifications for the PRODUCT and shall also agree on the final
     SPECIFICATIONS following the filing of the NDA in the United States of
     America, which shall at that time be attached to this Agreement as Schedule
     2. The SPECIFICATIONS may thereafter be amended as agreed by the parties or
     as may otherwise be requested or mandated by the regulatory authorities in
     the TERRITORY, most specifically the FDA.

5.7  For the avoidance of doubt, the parties hereby confirm that the primary
     objective of the development work on the PRODUCT is to generate data
     required for inclusion in the NDA and secure NDA APPROVAL for the PRODUCT
     in the United States of America. As of the date of this Agreement, it is
     the parties' expectation that the body of data so generated in the
     development of the PRODUCT will also be used to support such applications
     for regulatory approval that LIGAND shall make in the other countries of
     the TERRITORY.



                                      -16-
<PAGE>

5.8  In the event however that such expectation proves unfounded or incorrect
     and further data is required to obtain such other NDA APPROVAL as are
     pursued by LIGAND in the other countries of the TERRITORY, LIGAND shall
     determine the viability of proceeding further with the regulatory
     application and generation of the further data requirements. In the event
     that LIGAND elects to continue, the parties shall agree on the programme of
     work to be undertaken to generate such additional data and the apportioning
     of tasks and costs therefor. LIGAND shall reimburse ELAN for all such
     additional work which it requires ELAN to carry out in accordance with
     ELAN's charges as set out in Clause 10.2 of the Agreement.

                 CLAUSE 6 - PROJECT TEAM AND PROJECT MANAGEMENT

6.1  It is recognised by the parties that a significant commitment of resources
     shall be required from each party to accomplish successful NDA APPROVAL in
     the TERRITORY and launch of the PRODUCT, particularly in the co-ordination
     of logistics, finalisation of various specifications, preparation and
     agreement of clinical study designs and protocols (other than in relation
     to the clinical trials listed in Schedule 3), methodologies transfer,
     supply and packaging configurations, shipping and handling procedures etc.
     and for this purpose, the parties will establish a PROJECT TEAM.

6.2  The PROJECT TEAM shall consist of a chief representative from each party
     together with such additional business and development personnel from each
     party who are appropriately skilled and knowledgeable in relation to the
     development of the PRODUCT and who are deemed necessary to accomplish such
     work. The PROJECT TEAM shall have an equal number of members from each of
     the parties.

6.3  Unless otherwise agreed by the parties, the PROJECT TEAM shall meet at
     least once each calendar quarter, such meetings to continue until the time
     of launch or such later time as may be agreed. The PROJECT TEAM shall meet
     alternately at the Georgia offices of ELAN and the San Diego offices of
     LIGAND or as otherwise agreed by the parties. Meetings shall be co-chaired
     by the chief representatives of the parties. At and between meetings of the
     PROJECT TEAM, each party shall keep the other fully and regularly informed
     as to its progress with its respective obligations.

6.4  In the event of a dispute amongst the PROJECT TEAM which cannot be resolved
     by consensus, such dispute shall be resolved by a management committee
     which shall have an equal number of members from each of the parties. In
     the event that the dispute cannot be resolved by the management committee,
     the dispute shall be referred to the Vice President, Marketing of LIGAND
     and the Vice President, Commercial Development, Elan Pharmaceutical
     Technologies, a division of ELAN, who shall discuss the matter and attempt
     to reach an amicable solution. In the event that the foregoing officers
     cannot resolve the dispute amicably, the said officers shall refer the
     dispute to the Chairmen of LIGAND and ELAN who shall discuss the matter and
     attempt to reach an amicable solution. The provisions of this Clause 6.4.
     shall be without prejudice to the parties' other rights and remedies.



                                      -17-
<PAGE>

                     CLAUSE 7 - REGISTRATION OF THE PRODUCT

7.1  ELAN shall be responsible for the compilation, preparation, submission and
     prosecution to approval of the NDA for the PRODUCT in each country of the
     TERRITORY. ELAN will use its reasonable efforts in prosecuting the NDA to
     approval. ELAN shall thereafter maintain at its own cost the NDA and the
     NDA APPROVAL in each country of the TERRITORY for the INITIAL PERIOD. The
     NDAs shall remain the property of ELAN, provided that ELAN shall allow
     LIGAND access thereto to enable LIGAND to fulfill its obligations and
     exercise its rights hereunder, including the confidential portions of the
     CMC SECTION relating to the formulation and manufacturing processes.

7.2  At meetings of the PROJECT TEAM, ELAN shall consult with LIGAND on the
     preparation of the NDA. Notwithstanding the foregoing, ELAN shall at its
     sole discretion decide on the ultimate content of the NDA. ELAN shall
     notify LIGAND of the NDA APPROVAL in each country of the TERRITORY.

7.3  ELAN shall bear the costs and expenses of filing the NDA with the FDA in
     the USA provided that such costs as of the date of submission and filing of
     the NDA are consistent with the filing charges prevailing as of the date of
     this Agreement. All costs associated with maintaining the NDA APPROVAL
     (other than maintaining the manufacturer's licence, the costs of which
     shall be borne by ELAN) in each country of the TERRITORY including any post
     approval studies required by the FDA in respect of the PRODUCT shall be
     paid by ELAN. LIGAND may elect to conduct [**********] in conjunction with
     ELAN whether or not [**********] are mandated by the FDA provided that
     LIGAND shall bear [**********] in relation to commercialisation of the
     PRODUCT in the TERRITORY. Such costs incurred by LIGAND shall be deemed
     [**********] under Clause 5.5 of this Agreement.

7.4  If any information or clinical data are requested by the FDA in addition to
     the data generated from the clinical trials specified in Schedule 3 in
     order to obtain NDA APPROVAL in any country of the TERRITORY, LIGAND, at
     its option and at its own cost, may undertake to supply said information or
     data. If LIGAND so requests, ELAN will assist LIGAND, at LIGAND's expense,
     in the collection of said information or data. [**********], if incurred by
     LIGAND, will be deemed [**********] under Clause 5.5 of this Agreement. In
     the event that LIGAND decides not to generate any additional information or
     clinical data which is requested by the FDA to obtain NDA APPROVAL in any
     country of the TERRITORY, then, ELAN shall have the right to terminate the
     license granted to LIGAND pursuant to Clause 2.1. for any such country or
     countries of the TERRITORY. Thereafter, ELAN shall be entitled to research,
     develop and commercialise the PRODUCT in such country or countries of the
     TERRITORY. In the event of such termination, all monies paid to ELAN by
     LIGAND pursuant to this Agreement shall not be recoverable by LIGAND.

7.5  ELAN shall at its option file DMF(s) for the PRODUCT in its own name and
     shall be responsible for all interaction with FDA, and where applicable
     other REGULATORY AUTHORITIES, concerning the DMF.



                                      -18-
<PAGE>

7.6  ELAN [**********] LIGAND, its agents and employees [**********] to which
     LIGAND, its agents and employees [**********] in connection with
     [**********] or failure to [**********].

7.7  It is hereby acknowledged that there are inherent uncertainties involved in
     the development and registration of pharmaceutical products with the FDA
     insofar as obtaining approval is concerned and such uncertainties form part
     of the business risk involved in undertaking the form of commercial
     collaboration as set forth in this Agreement. Therefore, save for using its
     reasonable efforts, neither party shall have any liability to the other
     solely as a result of any failure of the PRODUCT to successfully achieve
     the interim specifications or to achieve the NDA APPROVAL by the FDA.

7.8  LIGAND shall not conduct any technical analysis, study or test on the
     formulations of the PRODUCT without the prior agreement of ELAN, save for
     the routine quality tests required to verify conformance with the
     SPECIFICATIONS.

                CLAUSE 8 - MARKETING AND PROMOTION OF THE PRODUCT

8.1  LIGAND shall control and be responsible for the content and format of the
     promotional campaign to be submitted to the FDA; provided that ELAN has the
     opportunity to review and provide input into such promotional campaign.
     LIGAND shall use reasonable endeavours to obtain approval by the FDA of the
     promotional campaign for the PRODUCT.

8.2  Within [**********] after the filing of the NDA in each country of the
     TERRITORY, LIGAND and ELAN shall agree upon appropriate due diligence
     obligations on LIGAND for marketing the PRODUCT, including the promotional
     support budget and minimum sales figures for the [**********] following
     commercial launch of the PRODUCT in each country of the TERRITORY, having
     regard to standard industry practises. In the event that the parties are
     unable to agree upon such due diligence obligations for the PRODUCT within
     the time period as set out above, the parties shall appoint an arbitrator
     who is technically knowledgeable in the pharmaceutical industry to choose
     either ELAN's proposed terms or LIGAND's proposed terms on the basis of
     which terms he determines to be closer to standard industry practice in the
     relevant country of the Territory. LIGAND and ELAN each shall be
     responsible for [**********] of the costs of arbitration incurred in
     connection with this Clause 8.2.

8.3  LIGAND shall diligently pursue the commercialisation of the PRODUCT and
     shall use all [******] efforts to market and promote the PRODUCT throughout
     the TERRITORY and in doing so, shall use the same level of effort as with
     other similar products of similar sales potential which it markets. LIGAND
     covenants that it shall not use the PRODUCT as a "loss leader" in its
     marketing programs and shall at all times use its reasonable efforts in
     marketing the PRODUCT.

8.4  LIGAND shall submit to ELAN for ELAN's information, copies of all
     promotional and other printed materials which LIGAND proposes at any time
     to use in relation to the sale 



                                      -19-
<PAGE>

     of the PRODUCT provided always that the provisions of this Clause 8.4 shall
     be without prejudice to the obligations and responsibilities of LIGAND
     under Clauses 8.1 and 14.9 and LIGAND shall indemnify and hold harmless
     ELAN from and against all claims, damages, losses, liabilities and expenses
     to which ELAN may become liable arising out of LIGAND's bad faith, gross
     negligence or intentional misconduct in connection with the activities
     described in this Clause 8.

8.5  To the extent permitted by law, such materials shall include due
     acknowledgement that the PRODUCT is developed and manufactured by ELAN.

8.6  LIGAND shall effect the first full scale national commercial launch of the
     PRODUCT in the each country of the TERRITORY within [**********] of the NDA
     APPROVAL in such country, provided that LIGAND shall have received the
     agreed quantities of LAUNCH STOCKS ordered pursuant to firm purchase orders
     at least [**********] in advance of the launch date. ELAN shall not
     unreasonably withhold its agreement to a request by LIGAND for an extension
     of the said [**********] period if there are legitimate commercial reasons
     for such an extension.

8.7  The parties shall meet to discuss the sales performance of the PRODUCT on a
     quarterly basis for the first year following the initial launch of the
     PRODUCT, on a semi-annual basis for the second and third years and on an
     annual basis thereafter. At such meetings, LIGAND shall report on the
     ongoing marketing and sales strategy related to the PRODUCT in the
     TERRITORY, including marketing approaches educational campaigns,
     promotional and advertising materials and campaigns, sales plans and
     results, performance against competitors, its objectives for the PRODUCT
     and its plans for the next year of the Agreement.

8.8  LIGAND shall mark or have marked all patent number(s) of the ELAN PATENTS
     on all PRODUCT or otherwise communicate to the trade the existence of the
     ELAN PATENTS in the countries of the TERRITORY in such a manner as to give
     constructive or actual notice of infringement under applicable laws.

                        CLAUSE 9 - SUPPLY OF THE PRODUCT

9.1  Save as otherwise provided in this Agreement, ELAN shall produce and supply
     to LIGAND its entire requirements of the PRODUCT. ELAN shall be the sole
     and exclusive supplier of the PRODUCT to LIGAND in the TERRITORY and LIGAND
     will purchase the PRODUCT exclusively from ELAN in the TERRITORY.

9.2  As a consequence of the restrictions currently imposed upon the
     importation, use and distribution of the COMPOUND in and into the countries
     of the TERRITORY, the parties acknowledge the requirement to order the
     appropriate quantity of COMPOUND in sufficient time to enable the supplier
     of the COMPOUND to obtain the appropriate aggregate quota from the Drug
     Enforcement Agency in the U.S.A. or its successor agency,, and its
     equivalent in Canada (where applicable). In this regard, the parties shall
     negotiate and agree upon a binding forecast for the supply of COMPOUND for
     the 



                                      -20-
<PAGE>

     applicable calendar year (or part thereof) including the quantity of
     COMPOUND which is necessary for the manufacture of the LAUNCH STOCKS. In
     the event that LIGAND does not order sufficient PRODUCT to utilise the
     quantity of COMPOUND, LIGAND shall reimburse ELAN for the cost of the
     unutilised COMPOUND.

9.3  The PRODUCT to be supplied to LIGAND by ELAN shall be in
     [******************] complying with the SPECIFICATIONS. ELAN shall deliver
     the PRODUCT to LIGAND and/or any party designated by LIGAND in proper
     packaging so as to permit safe storage and transport. ELAN shall bear all
     the costs of labeling the PRODUCT so as to appropriately display the LIGAND
     name provided that LIGAND supplies all the appropriate graphics, designs,
     logos and related and appropriate artwork.

9.4  As a consequence of the restrictions currently imposed upon the
     importation, use and distribution of COMPOUND into the countries of the
     TERRITORY, the parties currently envisage that the PRODUCT shall be
     manufactured by ELAN or a nominated sub-contractor in the USA for supply in
     the USA and Canada. In the event that the relevant authorities in Canada
     prohibit the importation of the PRODUCT from the USA, the parties shall
     review alternative arrangements which can be put in place having regard to
     such expenditure as is justified and the commercial opportunities available
     in the country or countries concerned. In the event that ELAN appoints a
     third party manufacturer, such appointment shall be subject to the secrecy
     provisions of Clause 16.1 and ELAN shall be solely responsible and liable
     to LIGAND for the performance of the said manufacturer. ELAN shall ensure
     that the said manufacturer's facility is approved by and complies in all
     material respects with the requirements of the FDA of the country where the
     PRODUCT is manufactured and sold and that LIGAND has the customary rights
     of audit and inspection of such third party manufacturer.

9.5  Within [**********] following the signing hereof, LIGAND shall provide ELAN
     with a forecast of LIGAND requirements for the PRODUCT for the 18 month
     period following the first anticipated NDA APPROVAL in the TERRITORY. The
     said forecast will be updated quarterly until the first NDA APPROVAL in the
     TERRITORY. Except as otherwise provided herein (and specifically except as
     set out in Clause 9.2. regarding ordering of the COMPOUND), all forecasts
     made hereunder shall be made to assist ELAN in planning its production and
     LIGAND in planning marketing and sales. Such forecasts shall not be binding
     purchase orders, shall not be the basis for a binding commitment under
     Clause 9.2 and shall be without prejudice to LIGAND's subsequent firm
     purchase orders for the PRODUCT in accordance with the terms of this
     Agreement.

9.6  In advance of the first NDA APPROVAL in the TERRITORY and in advance of NDA
     APPROVAL in the USA where such approval is not the first NDA APPROVAL in
     the TERRITORY, the parties shall discuss and agree upon the manufacture and
     purchase of specific quantities of LAUNCH STOCKS; however, for the
     avoidance of doubt, the parties hereby confirm that ELAN's manufacturing
     obligations shall only arise on receipt of firm purchase orders.



                                      -21-
<PAGE>

9.7  ELAN shall deliver the PRODUCT to LIGAND within [**********] of the receipt
     of a firm purchase order therefor ([**********] in the case of LAUNCH
     STOCKS). In any event and notwithstanding any firm purchase orders for
     LAUNCH STOCKS which LIGAND has already placed with ELAN, ELAN will notify
     LIGAND within 5 working days of ELAN's receipt of an approval letter, or a
     pre-approval letter in respect of a NDA from FDA. LIGAND shall within
     [*****] of such notification place a firm purchase order with ELAN for
     LAUNCH STOCKS, unless such a purchase order has already been submitted to
     ELAN prior to that date. In addition, LIGAND will use its reasonable
     efforts to provide forecasts for deliveries in addition to the LAUNCH
     STOCKS for the balance of the year in which the NDA APPROVAL is obtained.

9.8  Within [**********] after the first NDA APPROVAL in the TERRITORY and on or
     before the 23rd day of each calendar month thereafter, LIGAND shall provide
     a rolling 18 month-forecast for the period beginning on the first day of
     the relevant calendar month. The format of such 18 month-forecasts shall be
     comprised of a 12 month-forecast together with 2 quarterly forecasts. The
     first calendar quarter of such 18 month-forecast shall be a binding
     purchase commitment of LIGAND. In addition to the obligation of LIGAND
     regarding rolling 18 month-forecasts outlined herein, LIGAND shall provide
     ELAN with rolling 3 years' forecasts on 1st August of each year of this
     Agreement.

9.9  Subject to the agreement of ELAN, the 12 month forecasts (other than for
     LAUNCH STOCKS) may increase or decrease from one quarter to the next,
     provided, however, ELAN shall not be obligated to produce an amount of
     PRODUCT which differs by more than [**********] in terms of volume of
     PRODUCT ordered as compared to the preceding quarter. Notwithstanding the
     foregoing, ELAN will use its reasonable efforts to fulfil LIGAND's
     requirements in excess of forecasted amounts, but shall not be obliged to
     meet such requirements if it is not reasonably practicable to do so
     provided that ELAN shall supply the PRODUCT so ordered but not immediately
     available as soon thereafter as reasonably practicable.

9.10 The parties shall agree upon a minimum order quantity for the manufacture
     and supply of each dosage strength the PRODUCT. ELAN shall have the right
     to refuse to fulfil orders which do not conform with the provisions of this
     Clause 9.10. Where ELAN in its absolute discretion, fulfils any order which
     does not conform with the provisions of this Clause 9.10, the fulfillment
     of such order by ELAN shall not affect ELAN's right to refuse to fulfil any
     subsequent order which does not conform with the provisions hereof.

9.11 Save as otherwise agreed between the parties, delivery of consignments of
     PRODUCT shall be effected by ELAN EX-WORKS the manufacturing facility
     designated by ELAN. Risk of loss of or damage to any consignment of the
     PRODUCT shall pass to LIGAND when each such consignment of the PRODUCT is
     loaded onto the vehicle of LIGAND's agent on which it is to be despatched
     from the manufacturing facility designated by ELAN. LIGAND shall fully
     insure or procure the insurance of all consignments of the PRODUCT from the
     time when risk passes as aforesaid and shall produce the supporting
     insurance when requested by ELAN.



                                      -22-
<PAGE>

9.12 All claims for failure of any delivery of the PRODUCT to conform to the
     SPECIFICATIONS under Clause 14 shall be made by LIGAND to ELAN in writing
     within [******] following delivery except in the case of latent defects.
     Claims for latent defects, which could not reasonably have been discovered
     during the routine testing protocol (to be agreed by LIGAND and ELAN),
     shall be made by LIGAND to ELAN in writing within [******] of discovery.
     Failure to make timely claims in the manner prescribed shall constitute
     acceptance of the delivery.

9.13 PRODUCT which has been delivered and which has been shown within the period
     designated in Clause 9.12 not to conform to the SPECIFICATIONS where such
     non-conformity is attributable to negligent acts or omissions of ELAN shall
     be replaced at ELAN's cost within [******] of the receipt by ELAN of the
     failed PRODUCT except where such non-conformity is attributable to
     negligent acts or omissions of LIGAND.

9.14 In the event of an unresolved dispute as to conformity of the PRODUCT with
     the SPECIFICATIONS, the parties shall within 30 days appoint an independent
     first class laboratory to undertake the relevant testing and its findings
     shall be conclusive and binding upon the parties. All costs relating to
     this process shall be borne solely by the unsuccessful party. In the event
     that the parties should fail to agree a mutually acceptable independent
     laboratory within such 30 day period, the Head of the School of Pharmacy,
     Trinity College, Dublin, Ireland shall be entrusted with appointing such
     independent laboratory.

9.15 In the event that ELAN fails to deliver to LIGAND a significant portion of
     an order of PRODUCT for a period exceeding [******] from the due delivery
     date therefor, or there are [***************************************] are
     caused by the supplier of the COMPOUND or other raw materials or due to the
     applicable governmental imposed quota system for the COMPOUND), ELAN shall,
     if requested by LIGAND, meet with LIGAND as soon as possible thereafter to
     discuss the reasons for the [******] and outline to LIGAND its plans to
     remedy the situation. If following such meeting, or further meetings which
     may be agreed by the parties, the parties agree that ELAN is unlikely to
     remedy the situation within 90 days of the last such meeting, upon written
     request by LIGAND, ELAN shall for so long as such conditions exist:

     9.15.1  grant to LIGAND a production licence in the applicable country or
             countries of the TERRITORY so that LIGAND may manufacture the
             relevant PRODUCT without infringing any of the ELAN INTELLECTUAL
             PROPERTY. Any such licence shall apply only in regard to the
             relevant PRODUCT as well as to the applications of technology
             derived from the ELAN PATENT RIGHTS related to its use with such
             PRODUCT;

     9.15.2  provide LIGAND with any technical data incorporated in the ELAN
             KNOW-HOW, including but not limited to, access to the CMC SECTION,
             to give effect to the provisions of Clause 9.15.1 and ELAN shall
             promptly provide to LIGAND the documentation constituting the
             required material support, more particularly 



                                      -23-
<PAGE>

             practical performance advice, shop practice, specifications as to
             materials to be used and control methods; and

     9.15.3  assist LIGAND with the working up and use of the technology and
             with the training of LIGAND's personnel to the extent which may
             reasonably be necessary in relation to the manufacture of the
             PRODUCT by LIGAND. In this regard, ELAN will receive LIGAND's
             scientific staff in its premises for certain periods, the term of
             which will be agreed by the parties.

             For the avoidance of doubt, the parties confirm that a royalty of
             [**********] shall be payable by LIGAND to ELAN on sales of
             PRODUCT manufactured by LIGAND hereunder.

9.16 When ELAN has remedied the cause of its failure to satisfy LIGAND's
     requirements and is once again able to fulfil its obligations to supply the
     PRODUCT, LIGAND shall cease manufacturing the PRODUCT and shall resume
     purchasing the PRODUCT exclusively from ELAN pursuant to the terms of this
     Agreement provided that LIGAND shall be entitled to manufacture the PRODUCT
     for such period as is [*************] to enable LIGAND to [*************]
     by LIGAND in establishing its manufacturing capability for the PRODUCT
     prior to commercial production of the PRODUCT as provided for in this
     Clause 9.16. To the extent LIGAND's FULLY ALLOCATED COST of manufacturing
     the PRODUCT is [*************] to which ELAN would be entitled to under
     Clause 10.3.1, such [*************] of LIGAND's FULLY ALLOCATED COST
     expended in establishing such manufacturing capability for the PRODUCT.
     Furthermore, the royalty payable by LIGAND to ELAN pursuant to Clause 9.15
     on sales of PRODUCT manufactured by LIGAND shall be [*********] from
     [**********] to [**********]. Such [*********] in the royalty shall be
     [*********] towards [*********] of such FULLY ALLOCATED COST [*********] by
     LIGAND establishing such manufacturing capability for the PRODUCT. At such
     time LIGAND [*********] such FULLY ALLOCATED COST from the [*********]
     price of PRODUCT and the reduction in royalty payments, the royalty payable
     pursuant to Clause 9.15 shall revert to [**********]. Upon cessation of
     manufacture by LIGAND under this Clause 9.16, the production licence
     granted by ELAN to LIGAND under Clause 9.15 shall automatically terminate.

9.17 In manufacturing the PRODUCT under Clause 9.15, LIGAND shall be responsible
     for all process and equipment validation required by the FDA and the
     regulations thereunder and shall take all steps reasonably necessary to
     pass government inspection by the FDA.

9.18 At any time during the INITIAL PERIOD, ELAN shall be entitled to notify
     LIGAND of its intention to cease manufacture of the PRODUCT due to poor
     economic return on the PRODUCT, provided, however, that such notice is
     given to LIGAND at least [**********] prior to the date ELAN intends to
     cease manufacturing the PRODUCT. In such event, ELAN shall grant LIGAND a
     production licence in accordance with Clauses 9.15 and 9.17. For the
     avoidance of doubt, the parties confirm that a royalty of 



                                      -24-
<PAGE>

     [**********] shall be payable by LIGAND to ELAN on sales of PRODUCT
     manufactured by LIGAND hereunder.

9.19 ELAN will grant to [**********] or any other subsidiaries of ELAN, as
     necessary or appropriate, a licence of the ELAN PATENTS and ELAN KNOW-HOW
     and other intellectual property rights necessary for such company or
     companies to manufacture the PRODUCT in accordance with the terms of this
     Agreement.

                        CLAUSE 10 - FINANCIAL PROVISIONS

10.1 Licence Royalties:

     10.1.1  In consideration of the licence of the ELAN PATENTS granted to
             LIGAND under this Agreement, LIGAND shall pay to ELAN the following
             amounts:-

          (1)  $5 million in cash or in shares of Common Stock of LIGAND, par
               value $.001 per share (the "Common Stock") (valued at $11.65 per
               share), at LIGAND's option, upon the execution of the Agreement
               by both parties;

          (2)  $10 million in cash, or at LIGAND's option, in cash through an
               increase in the issue amount of the CONVERTIBLE NOTE, upon the
               execution of the Agreement by both parties;

          (3)  [**********] in cash or in shares of Common Stock of LIGAND
               (valued at a price per share equal to [**********]; and

          (4)  [**********] in cash or in shares of Common Stock of LIGAND
               (valued at a price per share equal to [**********].

     10.1.2. In the event that LIGAND elects to issue shares of the Common Stock
             pursuant to Clause 10.1.1(1), (3) or (4) or the CONVERTIBLE NOTE
             pursuant to Clause 10.1.1(2), each such issuance shall be made
             pursuant to, and subject to the terms and conditions set forth in,
             the PURCHASE AGREEMENT. Nothing in this Agreement shall relieve
             LIGAND from its obligations to make the payments set forth in
             Clauses 10.1.1(1), (2), (3), or (4), in cash, in the event that any
             of the applicable conditions set forth in the PURCHASE AGREEMENT
             are not satisfied or waived on or prior to the required payment
             date thereof; provided however, that in the event that LIGAND
             elects to issues shares of Common Stock pursuant to Clause
             10.1.1.(1), (3) or (4) and ELAN is unable to satisfy the conditions
             to such issuance as set forth in the PURCHASE AGREEMENT or if such
             conditions have not been waived by LIGAND, as the case may be,
             LIGAND and ELAN shall negotiate in good faith to agree upon
             customary terms and conditions which will enable LIGAND to issue
             such shares pursuant to a transaction exempt from the registration
             requirements of the Securities Act pursuant to Regulation D
             thereunder, including the giving by ELAN, to the extent possible,
             of representations and warranties in connection therewith.

10.2 Additional Assistance and Work:



                                      -25-
<PAGE>

             In the event that work or technical assistance beyond that
             specified in Schedule 3 ("ADDITIONAL WORK") is requested by
             LIGAND, or is necessary to complete the development of the
             PRODUCT, LIGAND shall reimburse ELAN in respect of the cost of
             such ADDITIONAL WORK requested by LIGAND or required pursuant to
             the terms of this Agreement provided that:

     10.2.1  where ELAN conducts ADDITIONAL WORK under Clause 10.2, ELAN's
             charges for such work shall be ELAN's [**********] except where
             ELAN is supervising any clinical studies for LIGAND, ELAN's charges
             for such supervisory work shall be ELAN's [**********].

     10.2.2  payment for all ADDITIONAL WORK carried out by ELAN hereunder shall
             be effected in U.S. Dollars within [**********] of the date of
             receipt of the relevant invoice for completed ADDITIONAL WORK.

10.3 Price of PRODUCT:

     10.3.1  The price of the PRODUCT to be charged by ELAN to LIGAND for
             commercial sale shall be :

          (1)  [**********] of NSP for the [**********] in the TERRITORY;

          (2)  [**********] of NSP for the [**********] in the TERRITORY; and

          (3)  [**********] of NSP for [**********] during the INITIAL PERIOD of
               the Agreement.

               Said price shall apply to PRODUCT supplied EX WORKS ELAN's
               facility to LIGAND. Notwithstanding the other provisions of this
               Agreement, ELAN shall in no circumstances be obliged to supply
               PRODUCT to LIGAND for commercial sale at less than [**********]
               ("FLOOR PRICE").

     10.3.2  The price of the PRODUCT to be charged to LIGAND for supplies of
             PRODUCT for distribution as [**********] promotional samples
             (including an indigent patient program not to exceed [**********]
             of PRODUCT sold IN MARKET by LIGAND in each country of the
             TERRITORY) in its marketing of the PRODUCT shall be equivalent to
             [**********] which price shall apply to PRODUCT supplied EX WORKS
             ELAN's facility to LIGAND.

     10.3.3  ELAN shall supply the PRODUCT to LIGAND at the [**********]. The
             purchase price of the PRODUCT may be adjusted by ELAN each calendar
             quarter with the understanding that such purchase price is intended
             to represent the [**********].

     10.3.4  Within 45 days of the end of each calendar quarter, LIGAND shall
             notify ELAN of the NSP of PRODUCT for that previous calendar
             quarter and pay to ELAN the excess of: (i) the percentage of NSP of
             PRODUCT for that previous calendar 



                                      -26-
<PAGE>

             quarter calculated in accordance with Clause 10.3.1. over (ii)
             the [**********] paid by LIGAND for such PRODUCT pursuant to
             Clause 10.3.4.

     10.3.5  Payment for all PRODUCT supplied by ELAN to LIGAND shall be made in
             $ within [****] of the date of the relevant invoice.

     10.3.6  All prices for the PRODUCT are exclusive of any applicable value
             added or any other sales tax, for which LIGAND will be additionally
             liable.

     10.3.7  In the event that LIGAND shall sell the PRODUCT together with other
             products of LIGAND to third parties (by the method commonly known
             in the pharmaceutical industry as "bundling") and the price
             attributable to the PRODUCT is less than the average price of "arms
             length" sales to similar customers for the reporting period in
             which sales occur (such sales to be excluded from the calculation
             of the average price of "arms length" sales), NSP for any such
             sales shall be the average price of "arms length" sales by LIGAND
             to similar customers in the country where such bundling occurs
             during the reporting period in which such sales occur.

     10.3.8  For the avoidance of doubt the parties agree that if for whatever
             reason the PRODUCT supplied by ELAN to LIGAND is not sold by
             LIGAND, payment to ELAN for such PRODUCT shall nonetheless be
             effected at [**********].

                    CLAUSE 11 - PAYMENTS, REPORTS AND AUDITS

11.1 LIGAND shall keep true and accurate records of gross sales of the PRODUCT,
     the items deducted from the gross amount in calculating the NSP, the NSP
     and the royalties payable to ELAN under Clause 10. LIGAND shall deliver to
     ELAN a written statement ("the STATEMENT") thereof within 45 days following
     the end of each calendar quarter, (or any part thereof in the first or last
     calendar quarter of this Agreement) for such calendar quarter. The
     STATEMENT shall outline on a country-by-country basis, the calculation of
     the NSP from gross revenues during that calendar quarter, the applicable
     percentage rate, and a computation of the sums due to ELAN (i.e. the price
     of the PRODUCT determined in accordance with Clause 10.3.1 less
     [**********]). The parties' financial officers shall agree upon the precise
     format of the STATEMENT.

11.2 Payments due on NSP of the PRODUCT based on sales amounts in a currency
     other than US Dollars shall first be calculated in the foreign currency and
     then converted to US Dollars on the basis of the exchange rate in effect
     for the purchase of US Dollars with such foreign currency quoted in the
     Wall Street Journal (or comparable publication if not quoted in the Wall
     Street Journal) with respect to the sale of currency of the country of
     origin of such payment for the day prior to the date on which the payment
     by LIGAND is being made.

11.3 Any income or other taxes which LIGAND is required by law to pay or
     withhold on behalf of ELAN with respect to royalties and any other monies
     payable to ELAN under 



                                      -27-
<PAGE>

     this Agreement shall be deducted from the amount of such NSP payments,
     royalties and other monies due. LIGAND shall furnish ELAN with proof of
     such payments. Any such tax required to be paid or withheld shall be an
     expense of and borne solely by ELAN. LIGAND shall promptly provide ELAN
     with a certificate or other documentary evidence to enable ELAN to support
     a claim for a refund or a foreign tax credit with respect to any such tax
     so withheld or deducted by LIGAND. The parties will reasonably cooperate in
     completing and filing documents required under the provisions of any
     applicable tax treaty or under any other applicable law, in order to enable
     LIGAND to make such payments to ELAN without any deduction or withholding.

11.4 All payments due hereunder shall be made to the designated bank account of
     ELAN in accordance with such timely written instructions as ELAN shall from
     time to time provide.

11.5 LIGAND shall pay interest to ELAN at the Prime Rate publicly announced by
     Morgan Guaranty Trust Company of New York at its principal office on the
     date (or next to occur business day, if such date is not a business day) on
     which payment should have been made pursuant to the applicable provisions
     of this Agreement plus [****] on all late payments more than 10 days past
     due under this Agreement applicable from the date on which payment should
     have been made pursuant to the applicable provisions of this Agreement
     until the date of payment.

11.6 Where meetings of the PROJECT TEAM have ceased and where ELAN so requests
     to supplement the information available to ELAN at the meetings of the
     parties under Clause 8.7, LIGAND shall provide ELAN with annual sales
     reports outlining the status of the PRODUCT in the TERRITORY, including a
     report on the competitive position of the PRODUCT in its relevant market
     segment(s).

11.7 For the 180 day period following the close of each calendar year of the
     Agreement, ELAN and LIGAND will, in the event that the other party
     reasonably requests such access, provide each other's independent certified
     accountants (reasonably acceptable to the other party) with access, during
     regular business hours and subject to the confidentiality provisions as
     contained in this Agreement, to such party's books and records relating to
     the PRODUCT, solely for the purpose of verifying the accuracy and
     reasonable composition of the calculations hereunder for the calendar year
     then ended.

11.8 In the event of a discovery of a discrepancy which exceeds [***] of the
     amount due or charged by a party for any period, the cost of such
     accountants shall be borne by the audited party; otherwise, such cost shall
     be borne by the auditing party.

11.9 ELAN shall make (and where relevant shall procure that ELAN's subcontractor
     shall make) that portion of its manufacturing, testing or storage facility
     where PRODUCT is manufactured, tested or stored, including all record and
     reference samples relating to the PRODUCT available for inspection by
     LIGAND's duly qualified person or by the relevant governmental or
     regulatory authority. The investigation shall be limited to 



                                      -28-
<PAGE>

     determining whether there is compliance with cGMP and other requirements of
     applicable law.

                      CLAUSE 12 - DURATION AND TERMINATION

12.1 This Agreement shall be deemed to have come into force on the EFFECTIVE
     DATE and, subject to the rights of termination outlined in this Clause 12
     will expire on a country by country basis:

     12.1.1  on the [**********] of the date of the launch of the PRODUCT in the
             country concerned; or

     12.1.2  in any country upon the expiration of the life of the last to
             expire patent included in the ELAN PATENTS in that country;

             whichever date is later to occur ("the INITIAL PERIOD").

12.2 Not later than [**********] prior to the end of the INITIAL PERIOD on a
     country by country basis, ELAN and LIGAND shall enter into a long-term
     supply agreement upon terms and conditions to be mutually agreed between
     the parties. If the parties fail to enter into such a long-term supply
     agreement, ELAN shall grant LIGAND a licence to the ELAN KNOW-HOW to
     manufacture the PRODUCT for sale in the TERRITORY and access to the CMC
     SECTION of the NDA APPROVAL upon terms and conditions to be mutually agreed
     between the parties, including a [**********] on NSP of sales of such
     PRODUCT.

12.3 In addition to the rights of termination provided for elsewhere in this
     Agreement, either party will be entitled forthwith to terminate this
     Agreement by written notice to the other party if:

     12.3.1  that other party commits any material breach of this Agreement, and
             (A) in the case of a breach capable of cure, fails to cure the same
             within 60 days after receipt of a written notice giving full
             particulars of the breach and requiring it to be remedied or (B) in
             the case of a breach not capable of cure, the non-breaching party
             has a remedy at law;

     12.3.2  that other party goes into liquidation (except for the purposes of
             amalgamation or reconstruction and in such manner that the company
             resulting therefrom effectively agrees to be bound by or assume the
             obligations imposed on that other party under this Agreement);

     12.3.3  an encumbrancer takes possession or a receiver is appointed over
             any of the property or assets of that other party;

     12.3.4  any proceedings are filed or commenced by that other party under
             bankruptcy, insolvency or debtor relief laws or anything analogous
             to any of the foregoing 



                                      -29-
<PAGE>

             under the laws of any jurisdiction occurs in relation to that
             other party, and such proceeding is not dismissed within 90 days;

12.4 For the purposes of Clause 12.3.1, a breach will be considered capable of
     remedy if the party in breach can comply with the provision in question in
     all respects other than as to the time of performance (provided that time
     of performance is not of the essence).

12.5 In further addition to the rights and termination provided for elsewhere in
     this Agreement, ELAN shall be entitled to terminate the licence granted to
     LIGAND under this Agreement for any country or countries of the TERRITORY
     in the event that:-

     12.5.1  LIGAND fails to effect any one of the commercial launches required
             by Clause 8 in accordance with the provisions thereof; or

     12.5.2  a TECHNOLOGICAL COMPETITOR of ELAN shall directly or indirectly,
             acquire [**********] or more of LIGAND's capital stock, or
             otherwise control or influence in any material respect the
             management or business of LIGAND, or

     12.5.3  any person or entity other than a TECHNOLOGICAL COMPETITOR shall
             acquire [**********] or more of the voting stock of LIGAND, or
             otherwise merge, consolidate or enter into any similar transaction
             (or binding agreement in respect thereof) with LIGAND; provided,
             however, that the foregoing shall not apply in relation to any
             exercise of any options by ELAN as contemplated herein or by the
             FINANCE AGREEMENTS.

                     CLAUSE 13 - CONSEQUENCES OF TERMINATION

13.1 Upon exercise of those rights of termination specified in Clause 12 or
     elsewhere in this Agreement, this Agreement shall, subject to the
     provisions of the Agreement which survive the termination of the Agreement
     automatically terminate forthwith and be of no further legal force or
     effect.

13.2 Upon termination of the Agreement by either party, or upon termination by
     ELAN of a licence for a particular country under Clause 12.5, the following
     shall be the consequences relating to the TERRITORY or the particular
     country, as applicable:

     13.2.1  any sums that were due from LIGAND to ELAN under the provisions of
             Clause 10 or otherwise howsoever prior to the exercise of the right
             to terminate this Agreement as set forth herein shall be paid in
             full within 30 days of termination of this Agreement and, subject
             to Clause 13.2.4, ELAN shall not be liable to repay to LIGAND any
             amount of money paid or payable by LIGAND to ELAN up to the date of
             the termination of this Agreement;

     13.2.2  all confidentiality provisions set out herein shall remain in full
             force and effect for a period of [******] from the date of
             termination of this Agreement;



                                      -30-
<PAGE>

     13.2.3  all responsibilities and warranties shall insofar are appropriate
             remain in full force and effect;

     13.2.4  the rights of inspection and audit shall continue in force for the
             period referred to in the relevant provisions of this Agreement;

     13.2.5  ELAN shall be entitled to research, develop and commercialise the
             PRODUCT for its own benefit in the TERRITORY or in the relevant
             country or countries of the TERRITORY;

     13.2.6  the licence granted by ELAN to LIGAND of the ELAN TRADEMARK under
             Clause 3.5 shall automatically terminate; and

     13.2.7  the option granted by ELAN to LIGAND to co-promote the PRODUCT in
             the Member States of the EU (excluding Ireland and Great Britain)
             under Clause 2.2.2. shall automatically terminate.

                       CLAUSE 14 - WARRANTY AND INDEMNITY

14.1 ELAN represents and warrants that it has all requisite corporate power and
     authority to execute, deliver and perform its obligations under this
     Agreement. This Agreement has been duly and validly authorized, executed
     and delivered by ELAN and constitutes a valid and legally binding agreement
     of ELAN enforceable against ELAN in accordance with its terms, except that
     (A) the enforcement thereof may be subject to (i) bankruptcy, insolvency,
     reorganization, moratorium or other similar laws now or hereafter in effect
     relating to creditors' rights generally and (ii) general principles of
     equity and the discretion of the court before which any proceeding therefor
     may be brought and (B) any rights to indemnity or contribution thereunder
     may be limited by federal and state securities laws and public policy
     considerations.

14.2 ELAN represents and warrants that it has the sole, exclusive and
     unencumbered right to grant the licences and rights herein granted to
     LIGAND, and that it has not granted any option, licence, right or interest
     in or to the ELAN PATENTS or ELAN KNOW-HOW to any third party which would
     conflict with the rights granted by this Agreement. ELAN also represents
     and warrants that none of the EXCLUDED PATENTS or EXCLUDED KNOW-HOW is
     necessary to import, use, offer for sale, sell and make or have made the
     PRODUCT. ELAN agrees to hold LIGAND harmless from any and all damages and
     reasonable out-of-pocket expenses and costs (including reasonable
     attorneys' fees) incurred or sustained by LIGAND as the result of any third
     party's challenges to ELAN's right to grant the licences and rights herein
     granted to LIGAND.

14.3 ELAN represents and warrants that the execution of this Agreement and the
     consummation of the transactions contemplated hereby will not breach or in
     any way conflict with the terms and conditions of any licence, contract,
     understanding or agreement, whether express, implied, written or oral
     between ELAN and any third party.

14.4 ELAN represents and warrants that no consent, approval, authorization or
     order of any 



                                      -31-
<PAGE>

     court or governmental agency or body or third party is required for the
     execution and delivery by ELAN of this Agreement of the consummation by
     ELAN of the transactions contemplated hereby, except that no representation
     or warranty is made with repsect to filings required by the Hart-Scot
     Rodino Antitrust Improvements Act of 1976, as amended, upon issuance of
     shares of Common Stock of LIGAND pursuant to Clauses 10.1.1 (3) and (4)
     hereof.

14.5 ELAN represents and warrants that, once successfully developed, the PRODUCT
     supplied by ELAN to LIGAND under this Agreement will conform to:

     14.5.1  the SPECIFICATIONS;

     14.5.2  all applicable regulations and requirements of the FDA including
             the then cGMP regulations which apply to the manufacture and supply
             of the PRODUCT.

             EXCEPT AS EXPRESSLY STATED IN THIS CLAUSE 14, ALL OTHER
             WARRANTIES, CONDITIONS AND REPRESENTATIONS, EXPRESS OR IMPLIED,
             STATUTORY OR OTHERWISE, INCLUDING A WARRANTY AS TO THE QUALITY OR
             FITNESS FOR ANY PARTICULAR PURPOSE OF THE PRODUCT ARE HEREBY
             EXCLUDED AND EXCEPT AS EXPRESSLY STATED IN THIS CLAUSE 14, ELAN
             SHALL NOT BE LIABLE IN CONTRACT, TORT OR OTHERWISE FOR ANY LOSS,
             DAMAGE, EXPENSE OR INJURY, ARISING OUT OF OR IN CONNECTION WITH
             THE PRODUCT OR ANY DEFECT IN THE PRODUCT OR FROM ANY OTHER CAUSE.

14.6 LIGAND represents and warrants that it has all requisite corporate power
     and authority to execute, deliver and perform its obligations under this
     Agreement. This Agreement has been duly and validly authorized , executed
     and delivered by LIGAND and constitutes a valid and legally binding
     agreement of LIGAND enforceable against LIGAND in accordance with its
     terms, except that (A) the enforcement thereof may be subject to (i)
     bankruptcy, insolvency, reorganization, moratorium or other similar laws
     now or hereafter in effect relating to creditors' rights generally and (ii)
     general principles of equity and the discretion of the court before which
     any proceeding therefor may be brought and (B) any rights to indemnity or
     contribution thereunder may be limited by federal and state securities laws
     and public policy considerations.

14.7 LIGAND represents and warrants that the execution, delivery and performance
     by LIGAND of this Agreement and the consummation by LIGAND of the
     transactions contemplated hereby will not conflict with or constitute or
     result in a breach of or a default under (or an event which with notice or
     passage of time or both would constitute a default under) or violation of
     any of (i) the terms or provisions of any indenture, mortgage, deed of
     trust, loan agreement, note, lease, license, franchise agreement, permit,
     certificate, contract or other agreement or instrument to which LIGAND is
     bound or to which any of its properties or assets is subject, except for
     any such conflict, breach, default, violation or event which would not,
     individually or in the aggregate, have a material adverse effect on the
     business, assets, liabilities (contingent or otherwise, 



                                      -32-
<PAGE>

     operations, condition (financial or otherwise), solvency, properties,
     prospects or material agreements of the LIGAND (any such event, a "Material
     Adverse Effect"), (ii) the certificate of incorporation or bylaws of LIGAND
     or (iii) (assuming compliance with all applicable state securities or "Blue
     Sky" laws and assuming the accuracy of the representations and warranties
     of each of ELAN set forth in this Clause 14 of this Agreement and the
     accuracy of the representations and warranties of ELAN and Elan
     International Services, Ltd., set forth in Section 4 of the SECURITIES
     PURCHASE AGREEMENT of even date herewith) any statute, judgment, decree,
     order, rule or regulation applicable to LIGAND or any of its properties or
     assets, except for any such conflict, breach or violation which would not,
     individually or in the aggregate, have a Material Adverse Effect.

14.8 LIGAND represents and warrants that no consent, approval, authorization or
     order of any court or governmental agency or body or third party is
     required for the execution and delivery by LIGAND of this Agreement of the
     consummation by LIGAND of the transactions contemplated hereby, except that
     no representation or warranty is made with repsect to filings required by
     the Hart-Scot Rodino Antitrust Improvements Act of 1976, as amended, upon
     issuance of shares of Common Stock of LIGAND pursuant to Clauses 10.1.1 (3)
     and (4) hereof.

14.9 LIGAND represents and warrants to ELAN that in the promotion, marketing,
     transporting, storing, handling, distributing and selling the PRODUCT
     hereunder:

     14.9.1  it will exercise all due skill, care and diligence in conducting
             such activities; and

     14.9.2  it will comply with the provisions of this Agreement, all FDA and
             other approvals, all applicable state and local regulatory
             approvals and all applicable laws, ordinances and regulations.

14.10 LIGAND represent and warrants that immediately after the consummation of
     the transactions contemplated by this Agreement. the fair value and present
     fair saleable value of the assets of LIGAND (on a consolidated basis) will
     exceed the sum of its stated liabilities and identified contingent
     liabilities; LIGAND (on a consolidated basis) is, nor will LIGAND (on a
     consolidated basis) be, after giving effect to the execution, delivery and
     performance of this Agreement, and the consummation of the transactions
     contemplated hereby and thereby, (a) left with unreasonably small capital
     with which to carry on its business as it is proposed to be conducted, (b)
     unable to pay its debts (contingent or otherwise) as they mature or (c)
     otherwise insolvent.

14.11 ELAN is cognisant in all material respects of all applicable statutes,
     ordinances and regulations of the TERRITORY with respect to the manufacture
     of the PRODUCT including, but not limited to the FFDCA, including cGLP and
     cGMP. ELAN shall manufacture or procure the manufacture the PRODUCT in
     conformance with the SPECIFICATIONS and the relevant NDA or DMF and in a
     manner which complies in all material respects with such statutes,
     ordinances, regulations and practises.



                                      -33-
<PAGE>

14.12 Each of the parties shall indemnify, defend and hold harmless the other
     party from all actions, losses, claims, demands, damages, costs and
     liabilities (including reasonable attorneys' fees) to which the other party
     is or may become liable insofar as they arise out of any breach by the
     first party of any of its obligations or warranties under this Agreement.

14.13 ELAN represents and warrants that, as of the date of this Agreement, to
     the best of its knowledge and belief, that making, using or selling the
     PRODUCT would not infringe any patent of any third party in the TERRITORY.

14.14 As a condition of obtaining an indemnity in the circumstances set out in
     Clauses 14.5, 14.6 and 14.9, the party seeking an ------------ ---- ----
     indemnity shall:

     14.14.1 fully and promptly notify the other party of any claim or
             proceedings, or threatened claim or proceedings;

     14.14.2 permit the indemnifying party to take full control of such claim or
             proceedings;

     14.14.3 assist in the investigation and defence of such claim or
             proceedings;

     14.14.4 not compromise or otherwise settle any such claim or proceedings
             without the prior written consent of the other party, which consent
             shall not be unreasonably withheld; and

     14.14.5 take all reasonable steps to mitigate any loss or liability in
             respect of any such claim or proceedings.

14.15 Notwithstanding anything to the contrary in this Agreement, ELAN and
     LIGAND shall not be liable to the other by reason of any representation or
     warranty, condition or other term or any duty of common law, or under the
     express terms of this Agreement, for any consequential or incidental or
     punitive loss or damage (whether for loss of profits or otherwise) and
     whether occasioned by the negligence of the respective parties, their
     employees or agents or otherwise.

                  CLAUSE 15 - ADVERSE EVENTS AND PRODUCT RECALL

15.1 Each party shall notify the other party promptly:

     15.1.1  of any complaints from third parties reported to such party
             involving any serious and unexpected adverse reactions resulting
             from the use of the PRODUCT; and

     15.1.2  of any potential recall of the PRODUCT by any governmental
             authority.

15.2 LIGAND and ELAN shall establish a procedure for formal adverse event
     handling and reporting. It is envisaged that LIGAND shall be responsible
     for 



                                      -34-
<PAGE>

     furnishing post-marketing reports to ELAN and where applicable, ELAN will
     be responsible for furnishing such reports to the FDA. LIGAND and ELAN
     shall keep each other informed and shall copy the other party with all
     communications with the FDA and other relevant regulatory agencies with
     respect to the PRODUCT.

15.3 In the event of any recall of the PRODUCT, as suggested or requested by any
     governmental authority:

     15.3.1  LIGAND shall perform the recall of the PRODUCT in the TERRITORY and
             save as provided in Clause 15.3.2, [**********].

     15.3.2  If the recall arises from ELAN's negligent acts or omissions in
             manufacturing the PRODUCT, the recall costs [**********] provided
             that LIGAND [**********] of the PRODUCT [**********].

             In the event that ELAN [**********] hereunder, ELAN shall be
             entitled but shall not obliged to [**********] of the PRODUCT
             described in Clause 15.3.1 and LIGAND shall provide ELAN
             [**********] by ELAN.

     15.3.3  Neither party shall be liable to the other party or to any third
             party for consequential or incidental damages which may arise as a
             result of the recall of the PRODUCT.

15.4 In the event that ELAN exercises its option pursuant to Clause 2.2, the
     parties shall review, and if appropriate, negotiate and amend the
     provisions of Clause 15, as appropriate.

                      CLAUSE 16 - MISCELLANEOUS PROVISIONS

16.1 Secrecy:

     16.1.1  Any information, whether written or oral (oral information shall be
             reduced to writing within one month by the party giving the oral
             information and the written form shall be furnished to the other
             party) pertaining to the PRODUCT that has been or will be
             communicated or delivered by ELAN to LIGAND, or by LIGAND to ELAN,
             including, without limitation, trade secrets, business methods, and
             cost, supplier, manufacturing and customer information, shall be
             treated by LIGAND and ELAN, respectively, as confidential
             information, and shall not be disclosed or revealed to any third
             party whatsoever or used in any manner except as expressly provided
             for herein; provided, however, that such confidential information
             shall not be subject to the restrictions and prohibitions set forth
             herein to the extent that such confidential information:

          (1)  is available to the public in public literature or otherwise, or
               after disclosure by one party to the other becomes public
               knowledge through no default of the party receiving such
               confidential information; or



                                      -35-
<PAGE>

          (2)  was known to the party receiving such confidential information
               prior to the receipt of such confidential information by such
               party, whether received before or after the date of this
               Agreement; or

          (3)  is obtained by the party receiving such confidential information
               from a third party not subject to a requirement of
               confidentiality with respect to such confidential information; or

          (4)  is required to be disclosed pursuant to: (A) any order of a court
               having jurisdiction and power to order such information to be
               released or made public; or (B) any lawful action of a
               governmental or regulatory agency provided that each party shall
               notify the other in writing of any disclosure of information
               required hereunder prior to such disclosure.

     16.1.2  Each party shall take in relation to the confidential information
             of the other party all such precautions as it normally takes with
             its own confidential information to prevent any improper disclosure
             of such confidential information to any third party; provided,
             however, that such confidential information may be disclosed within
             the limits required to obtain any authorisation from the applicable
             FDA or any governmental or regulatory agency or, with the prior
             written consent of the other party, which shall not be unreasonably
             withheld, or as may otherwise be required in connection with the
             purposes of this Agreement.

     16.1.3  LIGAND agrees that it will not use, directly or indirectly, any
             ELAN KNOW-HOW, or other confidential information disclosed to it by
             ELAN or obtained by it from ELAN pursuant to this Agreement, other
             than as expressly provided herein.

     16.1.4  Neither party will publicise the existence of this Agreement in any
             way without the prior written consent of the other party subject to
             the disclosure requirements of applicable laws and regulations. In
             the event that either party wishes to make an announcement
             concerning the Agreement, that party will seek the consent of the
             other party. The terms of any such announcement shall be agreed in
             good faith.

     16.1.5  At the request of a party in writing, the other party shall not
             disseminate any public announcement for a period of 60 days from
             the receipt of such request regarding this Agreement or the
             transactions contemplated hereby or regarding such requesting
             party, without such requesting party's consent, which shall not be
             unreasonably withheld, provided, however, a party may disseminate a
             public announcement regarding the foregoing if such party obtains
             an opinion of independent counsel that such party is obligated by
             law to disseminate such information to the public.

16.2 Specific Performance:



                                      -36-
<PAGE>

     Each of ELAN and LIGAND acknowledges and agrees that in the event either
     party materially breaches an obligations under this Agreement which can be
     specifically performed, the aggrieved party shall be entitled to seek
     specific performance of this Agreement and to enjoin any continuing breach
     of this Agreement (without the necessity of proving actual damages and
     without posting bond or other security), in addition to any other remedy
     which such aggrieved party may be entitled to at law or in equity and each
     of ELAN and LIGAND will waive the defence in any action for specific
     performance or other equitable relief that a remedy at law would be
     adequate or that the services provided hereunder are personal in nature.

16.3 Assignments/Sub-contracting:

     Neither party shall be permitted to assign or sub-licence any of its rights
     under this Agreement without the prior written consent of the other;
     provided that ELAN and LIGAND may assign this Agreement to an AFFILIATE
     without such consent provided that such assignment has no adverse tax
     implications for the other party and provided further that such assigning
     party is not relieved of its obligations hereunder. Notwithstanding the
     foregoing, but subject to ELAN's right to terminate this Agreement in
     Clause 12.5.3, LIGAND may transfer or assign its rights under this
     Agreement without the prior written consent of ELAN to a person that
     acquires all or substantially all of the assets or capital stock of LIGAND,
     provided that such assignment has no adverse tax implications for ELAN
     under this Agreement (but not in connection with the transfer of Shares of
     Common Stock of LIGAND granted to ELAN pursuant to this Agreement or the
     Securities Purchase Agreement). ELAN shall also have the right to
     subcontract all or any portion of the manufacturing or packaging of the
     PRODUCT to one or more third parties. LIGAND shall also have the right to
     subcontract all or any of its obligation regarding development of the
     PRODUCT. Each party shall be responsible for the acts and/or omissions of
     its respective AFFILIATES and subcontractors.

16.4 Parties bound:

     This Agreement shall be binding upon and enure for the benefit of parties
     hereto, their successors and permitted assigns.

16.5 Severability:

     If any provision in this Agreement is agreed by the parties to be, or is
     deemed to be, or becomes invalid, illegal, void or unenforceable under any
     law that is applicable hereto:

     16.5.1  such provision will be deemed amended to conform to applicable laws
             so as to be valid and enforceable or, if it cannot be so amended
             without materially altering the intention of the parties, it will
             be deleted, with effect from the date of such agreement or such
             earlier date as the parties may agree; and

     16.5.2  the validity, legality and enforceability of the remaining
             provisions of this Agreement shall not be impaired or affected in
             any way.



                                      -37-
<PAGE>

16.6 Force Majeure:

     Neither party to this Agreement shall be liable for delay in the
     performance of any of its obligations hereunder if such delay results from
     causes beyond its reasonable control, including, without limitation, acts
     of God, fires, strikes, acts of war, or intervention of a government
     authority, non-availability of raw materials, but any such delay or failure
     shall be remedied by such party as soon as practicable.

16.7 Relationship of the parties:

     Nothing contained in this Agreement is intended or is to be construed to
     constitute ELAN and LIGAND as partners or members of a joint venture or
     either party as an employee of the other. Neither party hereto shall have
     any express or implied right or authority to assume or create any
     obligations on behalf of or in the name of the other party or to bind the
     other party to any contract, agreement or undertaking with any third party.

16.8 Amendments:

     No amendment, modification or addition hereto shall be effective or binding
     on either party unless set forth in writing and executed by a duly
     authorised representative of both parties.

16.9 Waiver:

     No waiver of any right under this Agreement shall be deemed effective
     unless contained in a written document signed by the party charged with
     such waiver, and no waiver of any breach or failure to perform shall be
     deemed to be a waiver of any future breach or failure to perform or of any
     other right arising under this Agreement.

16.10 No effect on other agreements:

     This Agreement supersedes that certain Letter of Intent dated September 28,
     1998 between the parties as such Letter of Intent relates to the subject
     matter hereof. Except as limited by the foregoing sentence, no provision of
     this Agreement shall be construed so as to negate, modify or affect in any
     way the provisions of any other agreement between the parties unless
     specifically referred to, and solely to the extent provided, in any such
     other agreement.

16.11 Governing law and jurisdiction:

     This Agreement is construed under and ruled by the laws of New York. For
     the purposes of this Agreement the parties submit to the non-exclusive
     jurisdiction of the courts of New York.

16.12 Notice:



                                      -38-
<PAGE>

     16.12.1 Any notice or communications to be given under this Agreement shall
             be written in English and shall be sufficiently given if delivered
             personally or sent by nationally recognised overnight delivery
             service, or telecopier (receipt confirmed), addressed as follows:

                      ELAN at

                      Elan Corporation, plc.
                      Lincoln House
                      Lincoln Place
                      Dublin 2
                      Ireland.

                      Attention:    Vice-President & General Counsel,
                      Elan Pharmaceutical Technologies

                      Telephone:    353 1 7094000

                      Telefax:      353 1 6624960

                      LIGAND at

                      Ligand Pharmaceuticals Incorporated
                      10275 Science Center Drive
                      San Diego
                      California 92121
                      USA.

                      Attention:  General Counsel

                      Telephone:    (619) 550-7500

                      Telefax:      (619) 550-7506

                      or to such other address(es) and telecopier numbers as may
                      from time to time be notified by either party to the other
                      hereunder.

     16.12.2 Any notice sent by mail shall be deemed to have been delivered
             within 7 working days after dispatch and any notice sent by
             telecopy shall be deemed to have been delivered within 24 hours of
             the time of the despatch. Notice of change of address shall be
             effective upon receipt.

IN WITNESS of which the parties have executed this Agreement.





                                      -39-
<PAGE>


Executed by LIGAND on November  , 1998

By :      /s/ William L. Respess             
          -----------------------------------
Name:     William L. Respess                
          -----------------------------------
          Senior Vice President General      
          -----------------------------------
Title:    Counsel, Government Affairs       
          -----------------------------------


Executed by ELAN on November  , 1998

By:       /s/ Liam Daniel                    
          -----------------------------------
Name:     Liam Daniel                       
          -----------------------------------
Title:    Group Vice President, Finance
          -----------------------------------




<PAGE>


                                   SCHEDULE 1



                                  ELAN PATENTS



[**********]                        [**********]

[**********]                        [**********]

[**********]                        [**********]









<PAGE>




                                   SCHEDULE 2



                                 SPECIFICATIONS





<PAGE>




                                   SCHEDULE 3

                                 CLINICAL TRIALS

                                                             [**********]





© 2022 IncJournal is not affiliated with or endorsed by the U.S. Securities and Exchange Commission