NEUROGEN CORP
8-K/A, 1996-08-12
PHARMACEUTICAL PREPARATIONS
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<PAGE>
 
                      SECURITIES EXCHANGE AND COMMISSION

                           Washington, D. C.  20549

                                 ____________

                                  FORM 8-K/A

                                CURRENT REPORT

                                 ____________



                    Pursuant to Section 13 or 15(d) of the
                        Securities Exchange Act of 1934


                                 Date of Report
              (Date of earliest event reported):  November 1, 1995



                             Neurogen Corporation
             -----------------------------------------------------
            (Exact name of registrant as specified in its charter)


   Delaware                     0-18311                          22-2845714
- ---------------          ------------------------           -------------------
(State of                (Commission File Number)              (IRS Employer
Incorporation)                                              Identification No.)


   35 Northeast Industrial Road, Branford, Connecticut              06405
- -------------------------------------------------------------------------------
      (Address of principal executive offices)                    (Zip Code)


                                (203) 488-8201
              ---------------------------------------------------- 
              (Registrant's telephone number, including area code)
                                        

                                     None
         ------------------------------------------------------------
         (Former name or former address, if changed since last report)
<PAGE>
 
                                   SIGNATURE
                                   ---------

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


                                 NEUROGEN CORPORATION



Dated:  August 12, 1996               By:   /s/ Stephen R. Davis
                                            ------------------------------
                                            Stephen R. Davis
                                            Vice President- Finance and
                                               Chief Financial Officer

                                      2.
<PAGE>
 
                                 EXHIBIT INDEX

 
                                                                Sequentially
                                                               numbered page
                                                               -------------
10.1      Collaborative Research Agreement between the                
          Company and Pfizer Inc., dated as of 
          November 1, 1995
          (confidential treatment requested).

10.2      Development and Commercialization Agreement                
          between the Company and Pfizer Inc., 
          dated as of November 1, 1995 
          (confidential treatment requested).

10.3      Stock Purchase Agreement between the Company and           
          Pfizer Inc., dated as of November 1, 1995/1/.
 
- --------------
/1/Previously filed with the Current Report on Form 8-K filed April 1, 1996.

                                      3.

<PAGE>
 
==================================
 CONFIDENTIAL TREATMENT REQUESTED
Under 17 C.F.R. (SS)200.80(b)(4),
      200.83 and 240.24b-2
==================================

                                                                    EXHIBIT 10.1


                       COLLABORATIVE RESEARCH AGREEMENT

          This collaborative research agreement (this "Agreement") is entered
into as of November 1, 1995 by and between PFIZER INC. ("Pfizer"), a Delaware
corporation, having an office at 235 East 42nd Street, New York, New York 10017,
and NEUROGEN CORPORATION ("Neurogen"), a Delaware corporation, having an office
at 35 Northeast Industrial Road, Branford, Connecticut 06405, each on behalf of
itself and its Affiliates. Pfizer and Neutrogen are sometimes referred to herein
as a "Party" and collectively as the "Parties," and references to "Pfizer,"
"Neurogen," a "Party" or the "Parties" shall include their respective
Affiliates.

          Whereas, Neurogen has expertise regarding the neurotransmitter NPY and
the biological processes involving NPY, and has developed a compound designated
NGD 95-1 which the Parties believe may have pharmaceutical utility for the
treatment of obesity and eating disorders; and

          Whereas, Pfizer has the capability to discover, evaluate, develop and
market pharmaceutical products for the prevention and treatment of human
conditions, including products developed based upon NPY technology for the
treatment of obesity and other conditions;

          Whereas, the Parties wish to establish a collaborative program for the
research and development of Products (as defined below), including but not
limited to NGD 95-1, on the terms and conditions provided herein;

          Now, therefore, in consideration of the mutual covenants and promises
set forth in this Agreement, the Parties agree as follows:

1.        DEFINITIONS.

          Whenever used in this agreement, the terms defined in this Section 1
shall have the meanings specified.

          1.1  "Affiliate"  means any corporation or other legal entity owning
directly or indirectly, fifty percent (50%) or more voting capital shares or
similar voting securities of Pfizer or Neurogen; any corporation or other legal
entity fifty percent (50%) or more of the voting capital shares or similar
voting rights of which is owned, directly or indirectly, by Pfizer

                                       1
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

or Neurogen; or any corporation or other legal entity fifty percent (50%) or
more of the voting capital shares or similar voting rights of which is owned,
directly or indirectly, by a corporation or other legal entity which owns,
directly or indirectly, fifty percent (50%) or more of the voting capital shares
or similar voting securities of Pfizer or Neurogen.

          1.2  "Annual Research Plan"  means the written plan describing the
research and budgets in the Area to be carried out during each year during the
Contract Period by Pfizer and Neurogen pursuant to this Agreement. Each Annual
Research Plan will be attached to and made a part of this agreement as Exhibit
B.  A "year" will begin on the Effective Date and each of its anniversaries and
end on the day preceding the next anniversary of the Effective Date.

          1.3  "Area"  means [_______________]

          1.4  "Commercialization Agreement"  means the Development and
Commercialization Agreement between the Parties which has been executed
concurrently with the execution of this Agreement.

          1.5  "Contract Period"  means the period beginning on the Effective
Date and ending on the date on which this Agreement terminates.

          1.6  "Effective Date"  means the date set forth in the opening
paragraph of this Agreement.

          1.7  "Joint Technology"  means Technology that is or was:

               (a) developed by employees of or consultants to Pfizer or
Neurogen solely or jointly with each other during the Contract Period; or

               (b) acquired by purchase, license, assignment or other means from
third parties by Neurogen or Pfizer during the Contract Period.

          1.8 "Neurogen Confidential Information" means all information about
any element of the Neurogen or Joint Technology which is disclosed by Neurogen
to Pfizer and designated "Confidential" in writing by Neurogen at the time of
disclosure to Pfizer, to the extent that such information as of the date of
disclosure to Pfizer, is not (i) demonstrably

                                       2
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

known to Pfizer, other than by virtue of a prior confidential disclosure to
Pfizer by Neurogen; or (ii) disclosed in published literature or otherwise
generally known to the public through no fault or omission of Pfizer; or (iii)
obtained from a Third Party free from any obligation of confidentiality to
Neurogen.

          1.9  "Neurogen Technology"  means Technology that is or was:

               (a) developed by employees of or consultants to Neurogen alone or
jointly with Third Parties prior to the Effective Date or which is the subject
of patent applications filed by Neurogen in the two year period immediately
following the Contract Period, other than Joint Technology; or

               (b) acquired by purchase, license, assignment or other means from
Third Parties by Neurogen prior to the Effective Date.
          
          1.10 "NGD 95-1"  means the Neurogen compound designated as NGD 95-1
[_______________]

          1.11 "NPY"  means the neurotransmitter neuropeptide Y.

          1.12 "NPY Receptor"  means [_______________]

          1.13 "Patent Rights"  shall mean:

               (1) the Valid Claims of Neurogen's patent applications listed in
Exhibit A, and patents issuing on them, including any division, continuation,
continuation-in-part, renewal, extension, reexamination, reissue or foreign
counterpart thereof; and

               (2) all inventions deemed patentable within [_______________]
 including all the Valid Claims of patent applications, whether domestic or
 foreign, claiming such patentable inventions, including all continuations,
 continuations-in-part, divisions, and renewals, all letters patent granted
 thereon, and all reissues, reexaminations and extensions thereof.

          1.14 "Pfizer Confidential Information"  means all information about
any element of the Pfizer or Joint Technology which is

                                       3
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

disclosed by Pfizer to Neurogen and designated "Confidential" in writing by
Pfizer at the time of disclosure to Neurogen, to the extent that such
information as of the date of disclosure to Neurogen, is not (i) demonstrably
known to Neurogen, other than by virtue of a prior confidential disclosure to
Neurogen by Pfizer; or (ii) disclosed in published literature or otherwise
generally known to the public through no fault or omission of Neurogen; or (iii)
obtained from a Third Party free from any obligation of confidentiality to
Pfizer.

          1.15 "Pfizer Technology"  means Technology that is or was:

               (a) developed by employees of or consultants to Pfizer alone or
jointly with Third Parties prior to the Effective Date or which is the subject
of patent applications filed by Pfizer in the two year period immediately
following the Contract Period, other than Joint Technology; or

               (b) acquired by purchase, license, assignment or other means from
Third Parties by Pfizer prior to the Effective Date.

          1.16 "Product" means any pharmaceutical product, [_______________]
provided, however, that the term "Product" shall all exclude [_______________]
The Parties agree that NGD 95-1 shall be a "Product."

          1.17 "Research Program" is the collaborative research program
described in Article 2 and conducted by Pfizer and Neurogen pursuant to this
Agreement.

          1.18 "Stock Purchase Agreement"  means the Stock Purchase Agreement
between the Parties which has been executed concurrently with the execution of
this Agreement.

          1.19 "Technology" means all compounds, materials, technology,
technical information, know-how, expertise and trade secrets within the Area;
provided, however, it is agreed and understood that

                                       4
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

"Technology" shall not include any compounds, materials, technology, technical
information, know-how, expertise or trade secrets relating to[_______________]

          1.20 "Third Party"  means any entity other than Pfizer or Neurogen or
an Affiliate of either of them.

          1.21 "Valid Claim"  means a claim within Patent Rights so long as such
claim shall not have been disclaimed by either Pfizer or Neurogen or both, as
the case may be, or shall not have been held invalid in a final decision
rendered by a tribunal of competent jurisdiction from which no appeal has been
or can be taken.

2.        COLLABORATIVE RESEARCH PROGRAM.

          2.1  Purpose.  Neurogen and Pfizer shall conduct the Research Program
throughout the Contract Period. The objective of the Research Program is to
discover and develop Products.

          2.2  Annual Research Plan.  The Annual Research Plan for the first
year (commending on the Effective Date) during the Contract Period is described
in the attached Exhibit B. For each year after the first, the Annual Research
Plan shall be prepared by the Research Committee for submission to and approval
by Pfizer and Neurogen no later than ninety (90) days before the end of the
prior year. Each new Annual Research Plan for each succeeding year shall be
appended to Exhibit B and made part of this Agreement.

          2.3  Exclusivity.

               (a) Pfizer and Neurogen agree that during the Contract Period
they will not engage in any research, development, manufacturing or
commercialization activity (including entering into any agreement or arrangement
with a Third Party relating to any such activity) with respect to
[_______________] Section 7 of this Agreement contains additional provisions
regarding relevant Third Party technologies. The initial focus of the Parties'
efforts will be on [_______________]

                                       5
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (b) If during the term of the Commercialization Agreement and so
long as Neurogen retains or has exercised the option set forth in section 5.5
thereof a Party wishes to engage in, or enter into an arrangement with a Third
Party for, cli ical development or commercialization of [_______________]

               (c) During the Contract Period, prior to undertaking a drug
discovery or research program with a Third Party for chemical entities
[_______________] each Party will provide the other 90 days notice and an
opportunity during such 90-day period to negotiate an agreement between the
Parties regarding such a program. If no such agreement is executed within such
90-day period, the notifying Party will be free to enter into any agreement with
any Third Party regarding such a program without obligation to the Receiving
Party. Notwithstanding the foregoing, either Party may in-license known chemical
entities [_______________] without obligation to the other Party under this
Section 2.3(c); provided, however, that such arrangement does not provide for
further research of such chemical entity by the Third Party.

          2.4  Research Committee.

               (a) Purpose.  Pfizer and Neurogen shall establish a Research
Committee (the "Research Committee"):

                   (1) to review and evaluate progress under each Annual
Research Plan;

                   (2) to prepare the Annual Research Plan for each year; and

                                       6
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (b) to coordinate and monitor publication of research results
obtained from, and the exchange of information and materials that relate to, the
Research Program.

          2.5  Membership. Pfizer and Neurogen each shall appoint,in its sole
discretion, four members to the Research Committee. Substitutes may be appointed
at any time.

              The members initially shall be:

              Pfizer Appointees:    [         ]
                                    [         ]
                                    [         ]
                                    [         ]


               Neurogen Appointees: [         ]
                                    [         ]
                                    [         ]
                                    [         ]

               (a) Chair.  The Research Committee shall be chaired by two co-
chairpersons, one appointed by Pfizer and the other appointed by Neurogen.

               (b) Meetings. The Research Committee shall meet at least
quarterly, at places and on dates selected by each Party in turn.
Representatives of Pfizer or Neurogen or both, in addition to members of the
Research Committee, may attend such meetings at the invitation of either Party.

               (c) Minutes. The Research Committee shall keep accurate minutes
of its deliberations which record all proposed decisions and all actions
recommended or taken. Drafts of the minutes shall be delivered to all Research
Committee members within five (5) business days after each meeting. The Party
hosting the meeting shall be responsible for the preparation and circulation of
the draft minutes. Draft minutes shall be edited by the co-chairpersons and
shall be issued in final form only with their approval and agreement.

               (d) Decisions.  All decisions of the Research Committee shall be
made by majority of the members.

                                       7
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (e) Expenses. Pfizer and Neurogen shall each bear all expenses of
their respective members related to their participation on the Research
Committee.

          2.6  Reports and Materials.

               (a) Reports.  During the Contract Period, Pfizer and Neurogen
each shall furnish to the Research Committee:

                   (1) summary written reports within fifteen (15) days after
the end of each three-month period commencing on the Effective Date, describing
its progress under the Annual Research Plan; and

                   (2) comprehensive written reports within thirty (30) days
after the end of each year, describing in detail the work accomplished by it
under the Annual Research Plan during the year and discussing and evaluating the
results of such work.

               (b) Materials. Neurogen and Pfizer shall, during the Contract
Period, as a matter of course as described in the Annual Research Plan, or upon
each other's written or oral request, furnish to each other samples of
biochemical, biological or synthetic chemical materials which are part of Pfizer
Technology, Neurogen Technology or Joint Technology and which are necessary for
each Party to carry out its responsibilities under the Annual Research Plan. To
the extent that the quantities of materials requested by either Party exceed the
quantities set forth in the Annual Research Plan, the requesting Party shall
reimburse the other Party for the reasonable costs of such materials if they are
furnished.

          2.7  Laboratory Facilities and Personnel.  Neurogen shall provide
suitable laboratory facilities, equipment and personnel for the work to be done
by Neurogen in carrying out the Research Program.

          2.8  Diligent Efforts.  Pfizer and Neurogen each shall use reasonably
diligent efforts to achieve the objectives of the Research Program.  Neurogen
will use reasonably diligent efforts to achieve the objectives listed in each
Annual Research Plan attached as Exhibit B and Pfizer will use reasonably
diligent efforts to assist Neurogen in the pursuit of those objectives and in
the establishment of a development plan for the Products.

                                       8
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

          2.9 Excluded Technology. Notwithstanding anything to the contrary in
this Agreement or the Commercialization Agreement, Neurogen shall retain all
current and future rights to [_______________]

3.   FUNDING THE RESEARCH PROGRAM.

          3.1 Patent Assignment Fee. In partial consideration for the assignment
of certain Patent Rights as descried in Section 5.1(c) below, Pfizer shall pay
to Neurogen a non-refundable, non-creditable license fee equal to $3,500,000.
Such payment shall be made within five business days of the Effective Date.

          3.2  Research Funding

               (a) Pfizer shall pay Neurogen [_______________] The first such
payment shall be made on the Effective Date and apply to the three-month period
commencing November 1, 1995. Pfizer shall pay Neurogen in advance
[_______________] Each payment shall be paid by Pfizer in U.S. currency by check
or by other mutually acceptable means within thirty(30) days of the of the
commencement of the quarterly period to which such payment applies.

               (b) [_______________]

               (c) [_______________]

                                       9
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

4.   TREATMENT OF CONFIDENTIAL INFORMATION.

          4.1  Confidentiality.  Neurogen Confidential Information and Pfizer
Confidential Information disclosed under this Agreement shall be subject to the
provisions of Section 9.1 of the Commercialization Agreement.

          4.2  Publication.  Notwithstanding anything in this Agreement to the
contrary, results obtained in the course of the Research Program may be
submitted for publication following scientific review by the Research Committee
and subsequent approval by Neurogen's and Pfizer's managements, which approval
shall not be unreasonably withheld. After receipt of the proposed publication by
both Pfizer's and Neurogen's managements, written approval or disapproval shall
be provided within thirty (30) days for a manuscript, within fourteen (14) days
for an abstract for presentation at, or inclusion in, the proceedings of a
scientific meeting, and within fourteen (14) days for a transcript of an oral
presentation to be given at a scientific meeting.

          4.3  Publicity.  Except as required by law, neither Party may disclose
the terms of this Agreement nor the research described in it without the written
consent of the other Party, which consent shall not be unreasonably withheld.

          4.4  Disclosure of Inventions.  Each Party shall promptly inform the
other about all inventions that are conceived, made or developed in the course
of carrying out the Research Program by employees of, or consultants to, either
of them solely, or jointly with employees of, or consultants to the other.

          4.5  Restrictions on Transferring Materials.  Pfizer and Neurogen
recognize that the biological, synthetic, chemical and biochemical materials
which are part of Pfizer Technology, Neurogen Technology or Joint Technology
represent valuable commercial assets.  Therefore, throughout the Contract Period
and for five (5) years thereafter, except as   may be required in a contract
with a Third Party providing for the original grant of rights or transfer of
such materials from such Third Party to Neurogen or Pfizer, Neurogen and Pfizer
agree not to transfer such

                                       10
<PAGE>
 
materials to any third Party unless prior written consent for any such
transfer is obtained from the other Party.

5.        INTELLECTUAL PROPERTY RIGHTS.

          The following provisions relate to rights in the Neurogen Technology,
Pfizer Technology, Joint Technology and Patent Rights developed by Neurogen or
Pfizer or both, during the course of carrying out the Research Program.

          5.1  Ownership.

               (a) All Neurogen Confidential Information and Neurogen Technology
shall be owned by Neurogen. All Pfizer Confidential Information and Pfizer
Technology shall be owned by Pfizer. All Joint Technology shall be owned jointly
by Neurogen and Pfizer.

               (b) Subject to subsection (c) below, all Patent Rights covering
inventions made by Neurogen shall be owned by Neurogen. All Patent Rights
covering inventions made by Pfizer shall be owned by Pfizer. All Patent Rights
covering inventions made jointly by the Parties shall be jointly owned by the
Parties. Inventorship shall be determined in accordance with U.S. patent laws.

               (c) Neurogen hereby assigns to Pfizer all of its right, title and
interest in the patent applications listed in Exhibit A and in patent
applications filed after the Effective Date which cover Products discovered
prior to the Effective Date.

          5.2  Grants of Research Licenses.  Neurogen and Pfizer each grant to
the other a perpetual non-exclusive, worldwide, royalty-free license, including
the right to grant sublicenses to Affiliates, to make and use Confidential
Information, Technology and Patent Rights for all research purposes other than
the sale or manufacture for sale of products or processes.

6.        PROVISIONS CONCERNING THE FILING, PROSECUTION AND MAINTENANCE OF
PATENT RIGHTS.

          During the Contract Period, the Patent Rights shall be filed,
prosecuted and maintained by the Parties in accordance with Sections 8.1 through
8.3 of the Commercialization Agreement.

                                       11
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

7.        ACQUISITION OF RIGHTS FROM THIRD PARTIES.

          During the Contract Period, Neurogen and Pfizer shall each promptly
notify each other of any and all opportunities to acquire in any manner from
Third Parties, technology or patents or information which may be useful in or
may relate to the Research Program. Neurogen and Pfizer shall decide if such
rights should be acquired in connection with the Research Program and, if so,
whether by Neurogen, Pfizer or both. If acquired such rights shall become part
of the Confidential Information, Technology or Patent Rights, whichever is
appropriate, of the acquiring Party or Joint Technology, as the case may be.

8.        OTHER AGREEMENTS.

          Concurrently with the execution of this Agreement, Neurogen and Pfizer
shall enter into the Commercialization Agreement and the Stock Purchase
Agreement. [_______________]

9.        TERM, TERMINATION AND DISENGAGEMENT.

          9.1  Term.  Unless sooner terminated or extended, this Agreement shall
expire on the third anniversary of the Effective Date.

          9.2  Event of Termination.  The following event shall constitute an
event of termination ("Event of Termination"):

          (a) Neurogen or Pfizer shall fail in any material respect to perform
or observe this Agreement or the Commercialization Agreement, and any such
failure shall remain unremedied for thirty (30) days after written notice to the
failing Party.

          9.3  Termination.

                                       12
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (a) Upon the occurrence of any Event of Termination, the Party
not responsible may by notice to the other Party, terminate this Agreement.

               (b) If Pfizer terminates this Agreement pursuant to subparagraph
(a) above, the Commercialization Agreement shall continue according to its
terms. If Neurogen terminates this Agreement pursuant to subparagraph (a) above,
the Commercialization Agreement shall terminate immediately.

          9.4  Renewal of Research by Pfizer.  Pfizer shall have the option, in
its sole discretion, of renewing this Agreement for up to two one-year extension
p riods on the terms provided herein.  [_______________]

          9.5  Surviving Rights and Obligations.  Termination of this Agreement
for any reason shall be without prejudice to:

               (a) the rights and obligations of the Parties provided in
paragraphs 2.3(b), 4.1, 4.2, 4.5 and Section 12;

               (b) Neurogen's right to receive all payments accrued under
Section 3; or

               (c) any other remedies which either Party may otherwise have.

10.       REPRESENTATIONS AND WARRANTIES.

          Neurogen and Pfizer each represents and warrants as follows:

          10.1 Organization.  It is a corporation duly organized, validly
existing and is in good standing under the laws of the state of Delaware, is
qualified to do business and is in good standing as a foreign corporation in
each jurisdiction in which the conduct of its business or the ownership of its
properties requires such qualification and has all requisite power and
authority, corporate or otherwise, to conduct. its business as now being

                                       13
<PAGE>
 
conducted, to own lease and operate its properties and to execute, deliver and
perform this Agreement.

          10.2 Authorization.  The execution, delivery and performance by it of
this Agreement have been duly authorized by all necessary corporate action and
do not and will not (a) require any consent or approval of its stockholders, (b)
violate any provision of any law, rule, regulations, order, writ, judgment,
injunctions, decree, determination award presently in effect having
applicability to it or any provision of its certificate of incorporation or by-
laws or (c) result in a breach of or constitute a default under any material
agreement, mortgage lease, license, permit or other instrument or obligation to
which it is a Party or by which it or its properties may be bound or affected.

          10.3 Binding Agreement.  This Agreement is a legal, valid and binding
obligation of it enforceable against it in accordance with its terms and
conditions, except as such enforceability may be limited by applicable
bankruptcy, insolvency, moratorium, reorganization or similar laws, from time to
time in effect, affecting creditor's rights generally.

          10.4 No Conflict.  It is not under any obligation to any person or
entity, contractual or otherwise, that is conflicting or inconsistent in any
respect with the terms of this Agreement or that would impede the diligent and
complete fulfillment of its obligations.

          10.5 No Guarantee of Success; Limitations of Liability.  Each Party
makes no express or implied warranties, statutory or otherwise, concerning the
success of the Research Program or the quality, Validity, commercial utility,
freedom from infringement or any other characteristics of any Product, Neurogen
Technology, Joint Technology, Patent Right or other intellectual property rights
resulting from the Research Program.  Neurogen shall not be liable to Pfizer
with respect to Pfizer's manufacture, use or sale of Products.

          10.6 Neurogen Ownership of Patents.  Neurogen represents and warrants
that, except for the rights granted to Pfizer under this Agreement and the
Commercialization Agreement, it has, and shall use its reasonable best efforts
to retain, all right, title and interest in and to the Neurogen Technology, and
Patent Rights covering Neurogen Technology, that exist on the Effective Date.

                                       14
<PAGE>
 
          10.7 No Third Party Infringement.  Neurogen represents and warrants
that as of the Effective Date it has no knowledge that making, using and selling
existing Products or Product candidates as pharmaceutical products may or does
infringe the patent rights of any Third Party, nor does it have any knowledge
that any Third Party may be or is infringing the Patent Rights.

          10.8 No Third Party Rights to Products.  Neurogen represents and
warrants that as of the Effective Date it has no agreements, understandings or
undertakings with any Third Parties or entities regarding ownership or
disposition of any Products.

11.       COVENANTS OF NEUROGEN AND PFIZER OTHER THAN REPORTING REQUIREMENTS.

          Throughout the Contract Period, Neurogen and Fizer each shall:

          11.1 Organization.  maintain and preserve its corporate existence,
rights, franchises and privileges in the jurisdiction of its incorporation and
qualify and remain qualified as a foreign corporation in good standing in each
jurisdiction in which such qualification is from time to time necessary or
desirable in view of their business and operations or the ownership of their
properties; and

          11.2 Compliance.  comply in all material respects with the
requirements of all applicable laws, rules, regulations and orders of any
government authority to the extent necessary to conduct the Research Program,
except for those laws, rules, regulations, and orders it may be contesting in
good faith.

                                       15
<PAGE>
 
12.       INDEMNIFICATION.

          Pfizer will indemnify Neurogen for damages, settlements, costs, legal
fees and other expenses incurred in connection with a claim against Neurogen
based on any action or omission of Pfizer, its agents or employees related to
the rights or obligations of Pfizer under this Agreement; provided, however,
that the foregoing shall not apply (i) if the claim is found to be based upon
the negligence, recklessness, or willful misconduct of Neurogen or (ii) if
Neurogen fails to give Pfizer prompt notice of any claim it receives and such
failure materially prejudices Pfizer with respect to any claim or action to
which Pfizer's obligation pursuant to this Section applies. Pfizer, in its sole
discretion, shall choose legal counsel, shall control the defense of such claim
or petition and shall have the right to settle same on such terms and conditions
it deems advisable; provided, however, it shall obtain Neurogen's prior consent
to such part of any settlement which requires payment or other action by
Neurogen or is likely to have a material adverse effect on Neurogen's business
or its economic benefit under this Agreement.

13.       NOTICES.

          All notices shall be in writing mailed via certified mail, return
receipt requested, courier, or facsimile transmission addressed as follows, or
to such other address as may be designated from time to time:

          If to Pfizer:     To Pfizer at its address as set forth
                            at the beginning of this Agreement.
                            Attention: President,  Central Research

          with copy to:     Office of the General Counsel

          If to Neurogen:   Neurogen at its address as set forth at
                            the beginning of this Agreement.
                            Attn: President

          with copy to:     Vice President, Finance

          Notices shall be deemed given as of the date received.

14.       GOVERNING LAW.

                                       16
<PAGE>
 
This Agreement shall be governed by and construed in accordance with the laws of
the State of New York.

15.       MISCELLANEOUS.

          15.1 Binding Effect.  This Agreement shall be binding upon and inure
to the benefit of the Parties and their respective legal representatives,
successors and permitted assigns.

          15.2 Headings.  Paragraph headings are inserted for convenience of
reference only and do not form a part of this Agreement.

          15.3 Counterparts.  This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

          15.4 Amendment; Waiver; etc.  This Agreement may be amended, modified,
superseded or canceled, and any of the terms may be waived, only by a written
instrument executed by each Party or, in the case of waiver, by the Party or
Parties waiving compliance. The delay or failure of any Party at any time or
times to require performance of any provisions shall in no manner affect the
rights at a later time to enforce the same. No waiver by any Party of any
condition or of the breach of any term contained in this Agreement, whether by
conduct, or otherwise, in any one or more instances, shall be deemed to be, or
considered as a further or continuing waiver of any such condition or of the
breach of such terms any other term of this Agreement.

          15.5 No Third Party Beneficiaries.  No Third Party including any
employee of any Party to this Agreement, shall have or acquire any rights by
reason of this Agreement. Nothing contained in this Agreement shall be deemed to
constitute the Parties partners with each other or any Third Party.

          15.6 Assignment and Successors.  This Agreement may not be assigned by
either Party, except that each Party may assign this Agreement and the rights
and interests of such Party, in whole or in part, to any of its Affiliates, any
purchaser of all or substantially all of its assets or to any successor
corporation resulting from any merger or consolidation of such Party with or
into such corporations.

                                       17
<PAGE>
 
or to any successor corporation resulting from any merger or consolidation of
such Party with or into such corporations.

          15.7 Force Majeure.  Neither Pfizer nor Neurogen shall be liable for
failure of or delay in performing obligations set forth in this Agreement, and
neither shall be deemed in breach of its obligations, if such failure or delay
is due to natural disasters or any causes reasonably beyond the control of
Pfizer or Neurogen.

          15.8 Severability.  If any provision of this Agreement is or becomes
invalid or is ruled invalid by any court of competent jurisdiction or is deemed
unenforceable it is the intention of the Parties that the remainder of the
agreement shall not be affected.

          In witness whereof, the Parties have caused this Agreement to be
executed by their duly authorized representatives.


 PFIZER INC.                               NEUROGEN CORPORATION



 By: /s/ George M. Milne, Jr.              By: /s/ Harry H. Penner, Jr.
     ------------------------------           ------------------------------ 
     George M. Milne, Jr.                     Harry H. Penner, Jr.
     President, Pfizer Central Research       President and Chief
                                              Executive Officer

                                       18
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

                                   Exhibit A

                          NEUROGEN PATENT APPLICATIONS

[_______________]

                                       19
<PAGE>
 
                                   Exhibit B

                              ANNUAL RESEARCH PLAN

                                       20
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

                                NEUROGEN/PFIZER
                           NPY PROJECT COLLABORATION

                            RESEARCH PLAN AND GOALS
                            -----------------------

[_______________]

                                       21
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

[_______________]

                                       22
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

[_______________]

                                       23

<PAGE>
 
===================================
Confidential Treatment Requested
Under 17 C.F.R. (SS)200.80(b)(4),
      200.83 and 240.24b-2
===================================

                                                                    EXHIBIT 10.2

                  DEVELOPMENT AND COMMERCIALIZATION AGREEMENT

          This Development and Commercialization Agreement (this "Agreement") is
entered into as of November 1, 1995 (the "Effective Date") by and between Pfizer
Inc. ("Pfizer"), a Delaware corporation, having an office at 235 East 42nd
Street, New York, New York 10017 and Neurogen Corporation ("Neurogen"), a
Delaware corporation, having an office at 35 Northeast Industrial Road,
Branford, Connecticut 06405, each on behalf of itself and its Affiliates.
Pfizer and Neurogen are sometimes referred to herein as a "Party" and
collectively as the "Parties," and references to "Pfizer," "Neurogen," a "Party"
or the "Parties" shall include their respective Affiliates.

                                    RECITALS

          Whereas, Neurogen has expertise regarding the neurotransmitter NPY and
the biological processes involving NPY; and:

          Whereas, Pfizer has the capability to discover evaluate, develop and
market pharmaceutical products for the prevention and treatment of human
conditions, including products developed based upon NPY technology for the
treatment of obesity and other conditions;

          Whereas, the Parties have concurrently entered into a Collaborative
Research Agreement establishing a cooperative research program to discover and
develop Products (as defined below); and

          Whereas, the Parties wish to provide in this Agreement for the
clinical development and commercialization of Products;

          Now, Therefore, in consideration of the mutual covenants and promises
set forth in this Agreement, the Parties agree as follows:

                                   ARTICLE 1

                                  DEFINITIONS

          The capitalized terms used in this Agreement shall have the meanings
specified below in this Article 1 and in the Research Agreement.

          1.1  "Abandoned Product"  shall have the meaning assigned in Section
7.1 of this Agreement.

          1.2  "ACMT"  means the Pfizer Advanced Candidate Management committee
established to manage the development of a drug 

                                       1
<PAGE>
 
candidate from the decision to begin Phase III clinical trials to final
approval. This committee reports to the FDMT committee on operational issues and
strategic issues.

          1.3  "Affiliate" shall have the meaning assigned in Section 1.1 of the
Research Agreement.

          1.4  "Co-Promote" means to promote Products jointly through Pfizer,
Neurogen and their respective sales forces under a single trademark in a given
country.

          1.5  "Cost of Goods" means, with respect to either Party, (i) in the
case of products and manufacture-related services acquired from the other Party
or Third Parties, payments made to such other Party or Third Parties in respect
of the manufacture, production or formulation of Products in bulk or final
therapeutic form (as applicable), and (ii) in the case of manufacturing services
performed by a Party, including manufacturing services performed in support of
Third Party manufacturing, all direct and indirect costs for material, labor and
production overhead incurred by such Party in manufacturing, producing and
formulating Products in bulk or final therapeutic form (as applicable),
calculated in accordance with U.S. generally accepted accounting principles,
utilized consistently for the various pharmaceutical manufacturing operations of
such Party.  Pursuant to the last two sentences of Section 8.7 and solely for
the purpose described therein and not for any other calculations, Cost of Goods
shall also include compensation paid to Third Parties for licenses under certain
intellectual property rights.

          1.6  "Development Costs" means all actual costs incurred by a Party or
the Parties, or for its or their account, following the first filing of an IND
for a given Product, to conduct development of such Product aimed at achieving
Regulatory Approval of the Product in any given regulatory jurisdiction.
Development Costs include but are not limited to costs of conducting and
managing clinical studies and the costs of preparing regulatory submissions.
Development Costs for a Product shall exclude costs of preclinical studies
conducted before the first IND is filed with respect to that Product, process
development costs, scale-up costs and separately assessed general and
administrative overhead (i.e. expenses which for audited external reporting
purposes pursuant to U.S. generally accepted accounting principles utilized
consistently by such Party would be included in general and administrative
expenses rather than research and development expenses).

                                       2
<PAGE>
 
          1.7  "DPC" means the Pfizer Development Planning Committee which
approves the recommendations of the ACMT to proceed to Phase III development of
a drug candidate.
          1.8  "Drug Approval Application" means an application for Regulatory
Approval required before commercial sale or use of a Product as a drug in a
regulatory jurisdiction.

          1.9  "ECMT" means the Pfizer Early Candidate Management Team
established to manage the development of a compound from nomination to the
decision to begin to plan for Phase III clinical trials.  This committee reports
to the EDMT.

          1.10 "EDMT" means the Pfizer Exploratory Development Management Team
which endorses the major development strategy recommendations of the ECMT
including initiation of the development process.

          1.11 "FDA" means the United States Food and Drug Administration, or
any successor agency.

          1.12 "FDMT" means the Pfizer Full Development Management Team which
endorses the operational-issue recommendations of the ACMT.

          1.13 "IND" means an Investigational New Drug application filed with
FDA, and any substantially similar filing in any other regulatory jurisdiction.

          1.14 "Joint Technology" shall have the meaning assigned in Section 1.7
of the Research Agreement.

          1.15 "Marketing Expenses" means actual costs which are specifically
identifiable to the promotion and sale of a Product including activities allowed
by applicable regulatory authorities which are undertaken prior to Regulatory
Approval in preparation for the commercial launch of a Product in a particular
country.  Marketing Expenses include but are not limited to costs of advertising
and professional education, clinical studies conducted to support the Product
and not as part of a Drug Approval Application, specific training regarding the
Product and costs incurred to operate and maintain the sales force which
promotes a Product.  Marketing Expenses shall exclude separately assessed
general and administrative overhead (i.e., expenses which for audited external
reporting purposes pursuant to U.S. generally accepted accounting principles
utilized consistently by such party would be included in general and
administrative expenses rather than marketing expenses) and Cost of Goods.

                                       3
<PAGE>
 
          1.16 "NAFTA Territory" means all of the territories included in the
North American Free Trade Agreement as in effect from time to time during the
term of this Agreement.

          1.17 "Net Sales" means the gross amount invoiced by Pfizer or any
sublicensee of Pfizer for sales of Products to Third Parties, less normal and
customary trade discounts actually allowed, rebates, returns, credits, taxes the
legal incidence of which is on the purchaser and separately shown on Pfizer's or
any sublicensee of Pfizer's invoices and transportation, insurance and postage
charges, if prepaid by Pfizer or any sublicensee of Pfizer and billed on
Pfizer's or any sublicensee of Pfizer's invoices as a separate item.

          1.18 "Neurogen Confidential Information" shall have the meaning
assigned in Section 1.8 of the Research Agreement.

          1.19 "Neurogen Technology" shall have the meaning assigned in Section
1.9 of the Research Agreement.

          1.20 "NGD 95-1" shall have the meaning assigned in Section 1.10 of the
Research Agreement.

          1.21 "NPY" shall have the meaning assigned in Section 1.11 of the
Research Agreement.

          1.22 "Patent Rights" shall have the meaning assigned in Section 1.13
of the Research Agreement.

          1.23 "Pfizer Confidential Information" shall have the meaning assigned
in Section 1.14 of the Research Agreement.

          1.24 "Pfizer Technology" shall have the meaning assigned in Section
1.15 of the Research Agreement.

          1.25 "Product" shall have the meaning assigned in Section 1.16 of the
Research Agreement.

          1.26 "Profit" means Net Sales of Products in the NAFTA Territory minus
Cost of Goods for such finished Products sold in the NAFTA Territory.

          1.27 "Regulatory Approval" means any approvals (including pricing and
reimbursement approves) or other authorizations of any regulatory agency or
other governmental entity necessary for the 

                                       4
<PAGE>
 
manufacture, distribution, use or sale of Products in a regulatory jurisdiction.

          1.28 "Research Agreement" means the Collaborative Research Agreement
entered into between Pfizer and Neurogen concurrently with this Agreement.

          1.29 "Technology" shall have the meaning assigned in Section 1.19 of
the Research Agreement.

          1.30 "Third Party" shall have the meaning assigned in Section 1.20 of
the Research Agreement.

          1.31 "Valid Claim" shall have the meaning assigned in Section 1.21 of
the Research Agreement.

          1.32 "Worldwide Net Sales" means Net Sales of a Product throughout the
world during a given calendar year.

                                   ARTICLE 2

                                  DEVELOPMENT

          2.1  Development Decision-Making.  The clinical development of
Products shall be conducted jointly by the Parties in accordance with this
Article 2. Pfizer's EDMT, FDMT and DPC will have the final authority in the case
of disputes.

               (a) Neurogen shall have primary responsibility for the 
preparation and filing of Investigational New Drug applications and for the
conduct of Phase I clinical trials of NGD 95-1 and any back-up compounds and, as
mutually agreed by the Parties, other Products in the United States and in
accordance with the guidelines set forth in Appendix X attached hereto. Pfizer
shall have the right to designate a representative to participate in Neurogen's
decision-making process with respect to such matters. Such representative shall
have the right to attend and participate at all Neurogen meetings in which
significant decisions are to be made and to participate fully in all such
decision-making. In the event of a dispute or failure to agree, Pfizer's EDMT
will have final authority.

               (b) Pfizer shall have primary responsibility for further clinical
development of Products, commencing with Phase II clinical trials of each
Product, and for the preparation and filing of Drug Approval Applications for
Products.  Pfizer's ACMT and ECMT shall carry out such responsibility.  Neurogen
shall have the right to designate a representative to the ACMT and ECMT, with
the right to attend and participate at all 

                                       5
<PAGE>
 
meetings of the ACMT and ECMT and participate fully in all of the activities of
these bodies.

          2.2  Annual Plan and Budget; Report.

               (a) Within 60 days after the decision to file an IND in the case 
of NGD 95-1 and any back-up compounds, Neurogen and, in the case of all other
Products, Pfizer, shall prepare a detailed plan and budget specifying
development activities to be undertaken for the remainder of such calendar year
and projected expenses related thereto. Thereafter, the Party then having
primary responsibility for furthering development of such Product (the "Lead
Development Party") shall amend and update the plan and budget at least 90 days
prior to the beginning of a new calendar year while such development is ongoing.
The Lead Development Party shall provide the amended plan and budget to the
other Party for comment, but the Lead Development Party shall retain primary
responsibility for the plan and budget and all development activities with
respect to such Product in accordance with Section 2.1. The Lead Development
Party shall keep the other Party promptly informed of any proposed changes to
the plan and budget.

               (b) The Lead Development Party shall report to the other Party at
least once per calendar quarter on the progress of development of such Product.
Such report shall include a detailed comparison of actual activities and
expenses to the most recent plan and budget.

               (c) Notwithstanding any disagreement between the Parties 
regarding the contents of any annual plan and budget, and notwithstanding any
discrepancy between planned and actual activities or expenses, the Parties shall
be responsible for their respective share of Development Costs as provided in
Section 2.5 below.

          2.3  Regulatory Filings.  In the case of NGD 95-1 and any back-up
compounds, Neurogen and Pfizer will have the responsibilities set forth in
Appendix X.  In the case of all other Products, Pfizer will have the
responsibility for interaction with regulatory authorities and Neurogen will
support such activities.

          2.4  Diligent Efforts.  Each Party shall use reasonably diligent
efforts to carry out clinical development and to pursue Regulatory Approvals for
Products.  In conducting development activities under this Agreement, neither
Party shall prejudice the value of any Product by reason of such Party's
activities outside the scope of this Agreement.

                                       6
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED


          2.5  Development Costs.  All Development Costs shall be borne by the
Parties in accordance with this Section 2.5, on a Product-by-Product basis, with
reconciling payments made as provided in Section 2.6.

               (a) Except as set forth in Section 2.5(b)(2) below, Development 
Costs incurred in connection with conducting and completing Phase I and Phase II
clinical studies and preparing regulatory submissions not specifically to
achieve Regulatory Approval of any Product outside the NAFTA Territory will be
borne [_______________ ].

               (b) Within 60 days after commencement of the first Phase III 
clinical study with respect to the Product, Neurogen shall deliver written
notice to Pfizer electing one of the following planned courses of action
regarding funding of further Development Costs:

                   (1) Neurogen may elect [_______________] incurred with
respect to such Product after the completion of the last Phase II clinical study
prior to the commencement of the first Phase III clinical study, in which case
Neurogen shall receive compensation as provided in Section 5.4 on Net Sales of
such Product; or

                   (2) Neurogen may elect (i) [_______________] incurred with
respect to such Product after the completion of the last Phase II clinical study
prior to the commencement of the first Phase II clinical study, and (ii)
[______________] incurred with respect to such Product after the completion of
the first Phase I clinical study and before the completion of the last Phase II
clinical study, without interest, in which case Neurogen shall be eligible to 
Co-Promote such Product with Pfizer in the NAFTA Territory and receive
compensation for sales of such Product as provided in this Section 2.5(b)(2),
and not Sections 5.4 or 5.5. If Neurogen exercises its option to Co-Promote a
Product, it shall have the right to provide up to [_____________] of the
selling, detailing and related effort for the Product. Pfizer shall be
responsible for all major decisions and day-to-day decisions regarding
commercialization of the Product. Neurogen [_____________]

                                       7
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

        Worldwide Net Sales in                    Royalty Rates as a 
     Millions of Dollars ("Tiers")              Percentage of Net Sales
          
            [_____________________________________________]     


If Neurogen exercises this option to Co-Promote a Product, (i) both parties may
book their proportional part of Net Sales, Cost of Goods and related expenses on
a mutually agreeable basis; provided that such accounting treatment shall not
alter the economic terms set forth herein and (ii) the Parties shall enter into
a more detailed agreement to establish the mechanics of how the two Parties
sales forces will work together to Co-Promote the Product and how Neurogen's
contribution to the selling, detailing and related effort will be measured; or

                   (3) Neurogen may elect to (i) [______________] incurred with
respect to such Product after completion of the last Phase II clinical study,
which Development Costs are not specifically directed at achieving Regulatory
Approval outside the NAFTA Territory and (ii) [_______________] Development
Costs which are specifically directed at achieving Regulatory Approval outside
of the NAFTA Territory [_____________]

                                       8
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

                   (4) Notwithstanding anything to the contrary above, 
Neurogen shall be entitled to compensation pursuant to Sections 5.1,5.2 and 5.3
in all cases.

          2.6  Reimbursement of Development Costs.  The Party that incurs more
than its share of the total actual Development Costs for Products in each
quarter shall be paid by the other Party an amount of cash sufficient to
reconcile to its agreed percentage of actual Development Costs in each quarter.
Reconciling payments under this Section 2.6 shall be made within 30 days of
receipt of the other Party's quarterly report.  Failure of a Party to reimburse
the other Party for any Development Costs that are subject to a good faith
dispute hereunder shall not be deemed to be a material breach of this Agreement.

                                   ARTICLE 3

                                   MARKETING

          3.1  Diligent Efforts.  Except as otherwise provided in this
Agreement, Pfizer shall be solely responsible for the commercialization of
Products.  Pfizer shall use reasonably diligent efforts to promote, launch,
market and sell Products and to maximize the economic value of Products.

          3.2  Neurogen Option to Share Marketing Expenses; Co-Promotion by
Mutual Agreement. If Neurogen elects to share Development Costs under Section
2.5(b)(3) and profit share under Section 5.5, Neurogen shall be responsible for
[____________] of the Marketing Expenses of such Products in the NAFTA
Territory. All Marketing Expenses shall be borne by the Parties in accordance
with this Section 3.2, on a Product-by-Product basis, with reconciling payments
made as provided in Section 3.3. Subject to the future agreement of the Parties,
Neurogen may elect, [_____________] to meet part or all of its obligation under
Section 5.5 by supporting a sales force of Neurogen employees or agents,
provided that in such event Pfizer shall remain responsible for all major
decisions and day-to-day decisions regarding commercialization of the Product.
In such event, Neurogen's contribution of the Neurogen sales force towards the
[____________] requirement shall be measured not by the costs associated with
such force but instead based upon the ratio of the Neurogen force's effort to
the total sales effort of the Parties. Sales effort will be measured in a manner
to be mutually agreed upon which reflects the ways in which the Parties expect
such Product to be promoted and marketed in the NAFTA Territory. Pfizer shall
not unreasonably withhold or delay its agreement to such a Co-

                                       9
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

Promotion arrangement, provided that the sales force to be provided by Neurogen
can reasonably be expected to have experience and training commensurate with the
requirements of the Product sales effort. If the parties agree to co-promote,
both parties may book their proportional part of Net Sales, Cost of Goods, and
related expenses on a mutually agreeable basis; provided that such accounting
treatment shall not alter the economic terms set forth herein.

          3.3  Reimbursement of Marketing Expenses.  If Neurogen is to share
Marketing Expenses, the Party that incurs more than its share of the total
actual Marketing Expenses for Products in each quarter shall be paid by the
other Party an amount of cash sufficient to reconcile to its agreed percentage
of actual Marketing Expenses in each quarter.  Reconciling payments under this
Section 3.3 shall be made within 30 days of receipt of the other Party's
quarterly report.  Failure of a Party to reimburse the other Party for any
Marketing Expenses that are subject to a good faith dispute hereunder shall not
be deemed to be a material breach of this Agreement.

                                   ARTICLE 4

                                 MANUFACTURING

          4.1  Manufacture of Products.  Except in the event that Neurogen gives
notice of exercise of the option set forth in Section 4.3, Pfizer shall be
solely responsible for the manufacture and supply of bulk and finished Product
for all purposes.

          4.2  Process Development and Scale-up Costs.

               (a) So long as Neurogen retains or has exercised the option set 
forth in Section 4.3 below with respect to any Product, costs incurred by the
Parties in connection with manufacturing process development and scale-up of
such Product in the NAFTA Territory will be borne [______________] Reconciling
payments shall be made as provided in Section 2.6 with respect to Development
Costs.

               (b) If the option set forth in Section 4.3 below expires with 
respect to any given Product, or if Neurogen notifies Pfizer in writing that it
will not exercise such options with respect to such Product (for purposes of
this paragraph, the option "lapses"), [____________]

                                       10
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

          4.3  Neurogen Option.  Neurogen shall have the right, at its option,
to supply Pfizer with its NAFTA requirements for bulk and finished supplies of
each Product commercialized under this Agreement (during the period royalties or
Profit-share are payable with respect thereto). Neurogen may supply such
products directly, through an Affiliate or through a Third Party contractor
approved by Pfizer provided that such approval shall not be unreasonably
withheld. In each instance, Neurogen must exercise its rights by giving notice
to Pfizer at least [___________] and shall designate in such notice the
commencement date for such commercial supply of Pfizer's NAFTA requirements;
provided, however, that the Parties shall agree to extend such [___________]
period if necessary to satisfy FDA requirements. Such commencement date must
occur during the period [___________] At least ninety (90) days prior to
exercising the foregoing rights, Neurogen will notify Pfizer of its desire to
enter into a supply agreement, and the Parties shall thereafter negotiate in
good faith the terms, which shall include and be constant with the terms set
forth in this Section 4.3, upon which Neurogen shall manufacture and supply, or
cause to be manufactured and supplied, such Products in bulk and finished form.
The Parties shall conclude a definitive manufacturing and supply agreement
within ninety (90) days thereafter. Any such agreement shall include provisions
addressing the following:

               (a) A grant to Pfizer of customary and reasonable rights to
manufacture such bulk and/or finished Products, as the case may be, and/or
qualify a second source or to be that second source, in the event that Neurogen
or its Affiliate or agent fails to fulfill its material production obligations
under such agreement, after reasonable and customary nonce and opportunity to
cure;
               (b) That Pfizer shall consult with Neurogen in connection with 
process development, to assist Neurogen in establishing a cost-competitive
process which shall be identical to the process Pfizer develops to supply its
needs in the rest of the world;

                                       11
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (c) A selling price, subject to adjustment as set forth below 
(prior to applicable freight, postage, excises, sales taxes, and the like, but
excluding duties, all of which shall be borne by Pfizer, except for duties
incurred by reason of a decision by Neurogen to manufacture outside the NAFTA
Territory) not to exceed [____________] (the "Neurogen Transfer Price");

               (d) A provision regarding reduction and termination of
Neurogen manufacturing rights as follows;

                   (1) Except as set forth below, while Pfizer is purchasing 
one hundred percent (100%) of its NAFTA requirements from Neurogen,
notwithstanding the calculation of the applicable Neurogen Transfer Price,
Pfizer shall not be required to pay Neurogen more than [_______________] of
Pfizer's applicable per unit Cost of Goods for Product produced by Pfizer or an
Affiliate for sales outside of NAFTA. While Pfizer is purchasing fifty percent
(50%) or less of its NAFTA requirements from Neurogen, notwithstanding the
calculation of the applicable Neurogen more than [______________] of Pfizer's
applicable per unit Cost of Goods for Product produced by Pfizer or an
Affiliate.

                   (2) If for any consecutive twelve (12) month period 
commencing on an anniversary date of the receipt of the first commercial supply
shipment received by Pfizer under the manufacturing and supply agreement during
which Pfizer is purchasing one hundred percent (100%) of its NAFTA requirements
from Neurogen, the Neurogen Transfer Price is more than [_____________] of
Pfizer's Cost of Goods as calculated pursuant to subsection (a) above,
thereafter Neurogen shall be entitled to supply only fifty percent (50%) of
Pfizer's NAFTA requirements. Notwithstanding the foregoing, Pfizer shall have
the option of continuing to purchase the difference between fifty percent (50%)
and one hundred percent (100%) of its NAFTA requirements at the Neurogen
Transfer Price for up to an additional one (1) year period, provided that Pfizer
shall in no event be required thereby to pay for such excess quantities more
than [____________] of Pfizer's Cost of Goods applicable to similar units of
Product.

                   (3) If for any consecutive twelve (12) month period 
commencing on an anniversary date of the receipt of the first 

                                       12
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

commercial supply shipment received by Pfizer under the manufacturing and supply
agreement during which Pfizer is purchasing fifty percent (50%) of its United
States requirements from Neurogen, the Neurogen transfer Price is more than
[_______________] of Pfizer's Cost of Goods as calculated pursuant to subsection
(b) above, thereafter Neurogen shall not be entitled to supply any of Pfizer's
NAFTA requirements. Notwithstanding the foregoing, Pfizer shall have the option
of continuing to purchase up to fifty percent (50%) of its NAFTA requirements
for up to an additional one (1) year period.

               (e) Notwithstanding the provisions in subsection (iv) above,
Neurogen may retain its manufacturing rights by promptly rebating to Pfizer any
amounts by which Neurogen's Transfer Price exceeded [____________] as the case
may be, of Pfizer's Cost of Goods as contemplated in subparts (3) and (2) of
subsection (d) of this Section 4.3.

               (f) A provision indicating whether, at Neurogen's option, supply
by Neurogen will be for bulk and finished goods or only for bulk goods.

               (g) Notwithstanding the foregoing provisions of this Section 
4.3, the Parties agree to use their respective best efforts to establishing a
manufacturing and supply relationship that complies with Internal Revenue
Service regulation 936 and maintains the relative economic interests of the
Parties, as described above.

          4.4  Assurance of Manufacturing Capability.  Notwithstanding the
foregoing, Pfizer may request, as a condition to the exercise by Neurogen of its
option rights under Section 4.3, reasonable assurances that Neurogen has, or
will have at the time it commences supplying Product, the capability (internally
or through an agent to fulfill Pfizer's requirements for such bulk and finished
Products in a timely and reliable fashion and is willing to establish adequate
commercial manufacturing capability.  Pfizer agrees that upon completion of its
first production batch required for NDA approval and thereafter as long as
Neurogen is preparing to supply or is supplying products hereunder, Pfizer will
inform Neurogen of Pfizer's Cost of Goods for such Product for the immediately
preceding quarter and give Neurogen a good faith estimate of its Cost of Goods
for the succeeding four (4) quarters.

                                       13
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

          4.5  Separate Manufacturing Agreement.   Notwithstanding anything
herein to the contrary, any breach by a Party of obligations under any
manufacturing agreement entered into pursuant to Section 4.3 of this Agreement
shall not be deemed a breach of this Agreement and any remedies relating to any
such breach shall arise from any such manufacturing agreement and not this
Agreement.

                                   ARTICLE 5

                                  COMPENSATION

          5.1  Equity Investment.  In connection with this Agreement, the
Parties have concurrently entered into a Stock Purchase Agreement providing for
the purchase by Pfizer of 750,000 shares of the Common Stock of Neurogen.

          5.2  Milestone Payments.

               (a) Pfizer shall pay to Neurogen, within sixty (60) days of the
completion of each event set forth below, the payment described or listed
opposite that event.  [___________]  Payments shall be made in U.S.
dollars by check or other mutually acceptable means.

               (b)  Upon [__________]

                                       14
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (c) With respect to any Product for use in the prevention or 
treatment of obesity, Pfizer shall pay to Neurogen the following amounts based
upon the following Events. Pfizer shall be obligated to make each payment only
once with respect to each Product.

              Amount               Event
       
              [________________________________________]



               (d) With respect to any Product not described in subsection
(c) above, [____________]

          5.3  Royalty Outside NAFTA Territory.  Pfizer shall pay to Neurogen
royalties on the Net Sales of each Product outside the NAFTA Territory  as
follows.  The amount of the royalties paid by Pfizer to Neurogen shall be equal
to the [____________]

                                       15
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED
 
        Worldwide Net Sales in                    Royalty Rates as a
          Millions of Dollars                      Percentage of Net 
              ("Tiers")                                Sales              
 
            [__________________________________________________]

         
 
          By way of example, [____________]

          5.4   Royalty in NAFTA Territory.  Pfizer shall pay to Neurogen
royalties on Net Sales of each Product in the NAFTA Territory as to which
compensation is not being paid under Section 2.5(b)(2) or 5.5 as follows.
[____________]

                                       16
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

       Worldwide Net Sales in                         Royalty Rates as a 
        Millions of Dollars                            Percentage of Net  
            ("Tiers")                                        Sales

           [____________________________________________________]

                                                           
          5.5  Profit-Sharing in NAFTA Territory.  If Neurogen bears 
[___________] of NAFTA Development Costs of a Product pursuant to Section
2.5(b)(3) and [____________] of Marketing Expenses of a Product in the NAFTA
Territory pursuant to Section 3.2, Pfizer shall pay to Neurogen for each
calendar year [___________] of the Profit for such Product in the NAFTA
Territory provided, however, [__________]

                                       17
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

       Worldwide Net Sales in                         Royalty Rates as a 
        Millions of Dollars                            Percentage of Net  
            ("Tiers")                                        Sales

           [____________________________________________________] 
 
 
          5.6  Payment Term; Royalty Reduction.

               (a) Pfizer shall make payments pursuant to Sections 5.3, 5.4 
and 5.5 with respect to each country of the world from the date of first
commercial sale (the date of invoice of Pfizer or any sublicensee of Pfizer with
respect to such sale) of such Product in each such country until the expiration
of the last Patent Right to expire with respect to each such county and each
such Product. By way of further explanation, Pfizer shall pay royalties pursuant
to Sections 5.3, 5.4 and 5.5 with respect to the sale of Products whose
manufacture would infringe a Valid Claim if it were done by an unlicensed Third
Party, such royalties to be paid on the Net Sales of such Products even if the
actual sale of such Products would not alone infringe a Valid Claim if such
sales were made by an unlicensed Third Party. If Pfizer elects to manufacture in
a county where patent laws are not available, or does not obtain a manufacturing
patent in a country where patent laws are available, then Pfizer shall pay
royalties as if it had a manufacturing patent that issued in such country on the
date manufacture commenced and expired as provided under such country's patent
laws (or U.S. patent laws if such country has no patent laws).

               (b) Following the expiration of such term, Pfizer shall have a 
non-exclusive, fully-paid, worldwide license, including the right to grant
sublicenses, to use Neurogen Technology and Joint Technology to develop, make,
use, offer for sale, sell and import Products.

                                       18
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (c) [___________]

          5.7  Payments.  Royalties, Profit-share payments and payments made
pursuant to Section 2.5(b)(2) shall be made by Pfizer on Net Sales within sixty
(60) days after the end of each calendar quarter in which such Net Sales are
made.  Such payments shall be preceded by a statement, to be delivered within 30
days after the end of such calendar quarter, showing the Net Sales of each
Product by Pfizer or any sublicensee of Pfizer in each county, the applicable
royalty or other payment rate for such Product, and a calculation of all credits
and sums necessary to accurately determine the amount of payment due.

          5.8  Currency Conversion.  The Net Sales used for computing royalty
and Profit-share payments shall be computed and paid in U.S. dollars by check or
other mutually acceptable means.  For purposes of determining the amount of
royalties or Profit-share payments due, the amount of Net Sales in any foreign
currency shall be computed by (a) converting such amount into dollars at the
prevailing commercial rate of exchange for purchasing dollars with such foreign
currency as quoted by Citibank in New York on the last business day of the
calendar quarter for which the relevant payment is to be made by Pfizer and (b)
deducting the amount of any governmental tax duty, charge, or other fee actually
paid in respect of such conversion into, and remittance of dollars.

          5.9  Records.  Pfizer shall keep for three (3) years from the date of
each payment due hereunder complete and accurate records in sufficient detail to
allow the accurate determination, in a manner consistent with generally accepted
accounting principles in the United States, the sums or credits due under this
Agreement, including but not limited to Development Costs, Cost of Goods,
Marketing Expenses, Net Sales, Profit and royalties.  Neurogen shall have the
right for a period of three (3) years after receiving any report or statement
with respect to payments due and payable to appoint at its expense an
independent certified public 

                                       19
<PAGE>
 
accountant reasonably acceptable to Pfizer to inspect the relevant records to
verify such report or statement. Pfizer shall make its records available for
inspection by such independent certified public accountant during regular
business hours at such place or places where such records are customarily kept,
upon reasonable notice from Neurogen to verify the accuracy of the reports and
payments. Such inspection right shall not be exercised more than once in any
calendar year nor more than once with respect to sales in any given period.
Neurogen agrees to hold in strict confidence all information concerning payments
and reports, and all information learned in the course of any audit or
inspection, except to the extent necessary for Neurogen to reveal such
information in order to enforce its rights under this Agreement or if disclosure
is required by law. The failure of Neurogen to request verification of any
report or statement during said three-year period shall be considered acceptance
of the accuracy of such report, and Pfizer shall have no obligation to maintain
records pertaining to such report or statement beyond said three-year period.
The results of each inspection, if any, shall be binding on both Parties.

          5.10 No Other Compensation.  Pfizer shall not be obliged to reimburse
Neurogen for any costs incurred by Neurogen with respect to Products prior to
the Effective Date, except to the extent that payments expressly provided for in
this Agreement or the Research Agreement might be considered compensation for
such costs.

                                   ARTICLE 6

                                    LICENSES

          6.1  Commercialization License to Pfizer.   In addition to the
assignment of certain Patent Rights set forth in Section 5.1 (c) of the Research
Agreement, Neurogen grants to Pfizer an exclusive, worldwide license, including
the right to grant sublicenses, under the Patent Right, Neurogen Technology and
Joint Technology which are not so assigned to develop, make, use, offer for
sale, sell and import Products, subject to the terms of this Agreement.  Unless
terminated earlier in accordance with this Agreement, such license shall
commence on the Effective Date and shall terminate on the expiration date of the
payment obligation set forth in Section 5.6, except to the extent continued
pursuant to Section 5.6 (b).

          6.2  Technical Assistance.  Neurogen shall provide to Pfizer or any
sublicensee of Pfizer, at Pfizer's request and expense, any technical 

                                       20
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

assistance reasonably necessary to enable Pfizer or such sublicensee to
manufacture, use or sell each Product and to enjoy fully all the rights granted
to Pfizer pursuant to this Agreement; provided, however, that Neurogen is
reasonably capable of providing that assistance.

          6.3  Representation and Warranty.  Neurogen represents and warrants to
Pfizer that it has the right to grant the licenses granted pursuant to this
Article 6, and that the licenses so granted does not conflict with or violate
the terms of any agreement between Neurogen and any Third Party.

          6.4  Sublicensing.  If Pfizer grants a license or sublicense under any
rights granted in Section 6.1, (A) Pfizer shall guarantee that any sublicensee
fulfills all of Pfizer's obligations under this Agreement; provided, however
that Pfizer shall not be relieved of its obligations pursuant to this Agreement
and (B) any such licenses or sublicenses shall include obligations for the
licensee or sublicensee (i) to account for and report its sales of Products on
the same basis as if such sales were Net Sales by Pfizer and (ii) not to engage
in any development activities (including sponsoring or conducting clinical
trials) with respect to [___________]



                                   ARTICLE 7

                               ABANDONED PRODUCTS

          7.1   Abandoned Products.  If Pfizer discontinues development or 
commercialization of a Product, the right to such Product (an "Abandoned
Product") shall revert to Neurogen in accordance with this Article 7. So long as
Pfizer continues to diligently pursue development and commercialization of back-
up compounds to such a Product. Pfizer shall not be deemed to have discontinued
development of the Product and such Product shall not be an Abandoned Product
subject to this Article 7.

          7.2   Commercialization by Neurogen.  With respect to any Product 
which becomes an Abandoned Product pursuant to Section 7.1, the following
provisions shall apply.

                (a) The license granted to Pfizer in Section 6.1 shall 
terminate with respect to the Abandoned Product and, if applicable to such

                                       21
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

Abandoned Product, Pfizer shall reassign to Neurogen those Patent Rights
assigned in Section 5.1 (c) of the Research Agreement all, at such time as the
Product becomes an Abandoned Product pursuant to Section 7.1.

               (b) Pfizer grants to Neurogen an exclusive, worldwide license,
including the right to grant sublicenses, under the Patent Right, Pfizer
Technology and Joint Technology to develop, make, use, offer for sale, sell and
import such Abandoned Product, subject to the payment obligations of Section 7.3
below.

               (c) Pfizer shall provide to Neurogen or any sublicensee of 
Neurogen, at Neurogen's request and expense, any technical assistance, Pfizer
Confidential Information, Pfizer Technology, clinical data, regulatory
submissions and registrations or other information, materials, rights or
assistance reasonably necessary to enable Neurogen or such sublicensee to
develop, manufacture, use or sell such Abandoned Product and to enjoy fully all
the rights granted to Neurogen pursuant to this Article 7; provided, however,
that Pfizer is reasonably capable of providing that assistance.

          7.3   Compensation to Pfizer.

                (a) Neurogen shall pay to Pfizer royalties as follows on the 
Net Sales of Products that became Abandoned Products after the completion of
Phase III studies of such Product. The amount of royalties shall be
[____________]


       Worldwide Net Sales in                         Royalty Rates as a 
        Millions of Dollars                            Percentage of Net  
            ("Tiers")                                        Sales

           [____________________________________________________] 

                                       22
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (b) Neurogen shall pay to Pfizer royalties as follows on the 
Net Sales of Products that became Abandoned Products after the completion of
Phase II studies of such Product and before the completion of Phase III studies.
The amount of royalties shall be [___________]


       Worldwide Net Sales in                         Royalty Rates as a 
        Millions of Dollars                            Percentage of Net  
            ("Tiers")                                        Sales

           [____________________________________________________] 



                (c) With respect to Products that became Abandoned Products 
prior to the completion of Phase II studies but following the filing of an IND
for such Product, Neurogen shall compensate Pfizer as follows if Neurogen
commences development of such Abandoned Product. [___________]

                (d) With respect to Products that became Abandoned Products 
prior to the filing of an IND for such Product, Neurogen shall compensate Pfizer
as follows if Neurogen commences development of such Abandoned Product. 
[____________]

                                       23
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

                (e) The provisions relating to royalty term, royalty reduction,
payment, currency conversion and records set forth in Sections 5.6 through 5.10
with respect to payments to be made by Pfizer shall also apply with respect to
payments to be made by Neurogen pursuant to this Section 7.3.  In no event shall
compensation be due to Pfizer under more than one of the above paragraphs of
this Section 7.3.

          7.4  Indemnification.  Neurogen shall indemnify and hold Pfizer
harmless with respect to claims based upon Neurogen's sales of Products pursuant
to this Article 7, on the same terms applicable to Pfizer under Article 11.

                                   ARTICLE 8

                             PATENTS; INFRINGEMENT

          8.1  Filing, Prosecution and Maintenance by Pfizer.

               (a) With respect to Patent Rights covering (i) Neurogen 
Technology which relates solely to Products, (ii) Joint Technology or (iii)
Pfizer Technology, Pfizer shall have the exclusive right:

                   (1) To file applications for letters patent on any patentable
invention included in such Neurogen Technology, Joint Technology or Pfizer
Technology; provided, however, that Pfizer shall consult with Neurogen regarding
countries in which such patent applications should be filed and shall file
patent applications in those countries where Neurogen requests that Pfizer file
such applications; and, further provided, that Pfizer, at its option and
expense, may file in countries where Neurogen does not request that Pfizer file
such applications;

                   (2) To prosecute all pending and new patent applications 
included within Patent Rights;

                   (3) To respond to oppositions filed by Third Parties against 
the grant of letters patent for such applications; and

                                       24
<PAGE>
 
                   (4) To maintain in force any letters patent included in 
Patent Rights by duly filing all necessary papers and paying any fees required
by the patent laws of the particular country in which such letters patent were
granted.

               (b) Pfizer shall notify Neurogen in a timely manner of any 
decision to abandon a pending patent application or an issued patent included in
Patent Right. Thereafter, Neurogen shall have the option, at its expense, of
continuing to prosecute any such pending patent application or of keeping the
issued patent in force.

               (c) Pfizer shall provide to Neurogen copies of all patent 
applications that are part of Patent Rights prior to filing, for the purpose of
obtaining substantive comment of Neurogen patent counsel. Pfizer shall also
provide to Neurogen copies of all documents relating to prosecution of all such
patent applications in a timely manner and shall provide to Neurogen every six
(6) months a report detailing status.

               (d) Pfizer shall have the right to file on behalf of Neurogen all
applications and take actions necessary to obtain patent extensions pursuant to
35 U.S.C. Section 156 or similar foreign statutes for Patent Rights licensed to
Pfizer hereunder.  Neurogen agrees to sign, at Pfizer's expense, such further
documents and take such further actions as may be requested by Pfizer in this
regard.

          8.2  Filing, Prosecution and Maintenance by Neurogen.  With respect to
Patent Rights covering Neurogen Technology which does not relate solely to
Products, Neurogen shall have those rights and duties ascribed to Pfizer in
Section 8.1.

          8.3  Disclaimer of Claims.  Neither Party may disclaim a claim of a
patent application within the Patent Rights without the consent of the other.

          8.4  Actual or Threatened Infringement.

                                       25
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

               (a) When information comes to the attention of Neurogen to the 
effect that any Patent Rights relating to a Product have been or are threatened
to be unlawfully infringed, Neurogen shall promptly notify Pfizer of such
information. When information comes to the attention of Pfizer (through Neurogen
or otherwise) to the effect that any Patent Rights relating to a Product have
been or are threatened to be unlawfully infringed, Pfizer shall have the right
at its expense to take such action as it may deem necessary to prosecute or
prevent such unlawful infringement, including the right to bring or defend any
suit, action or proceeding involving any such infringement. Pfizer shall notify
Neurogen promptly of the receipt of any such information and of the commencement
of any such suit, action or proceeding. If Pfizer determines that it is
necessary or desirable for Neurogen to join any such suit, action or proceeding,
Neurogen shall, at Pfizer's expense, execute all papers and perform such other
acts as may be reasonably required to permit Pfizer to act in Neurogen's name.
[___________]

               (b) If Pfizer does not, within one hundred twenty (120) days 
after giving notice to Neurogen of the above-described information, notify
Neurogen of Pfizer's intent to bring suit against any infringer, Neurogen shall
have the right to bring suit for such alleged infringement, but it shall not be
obligated to do so, and may join Pfizer as Party plaintiff, if appropriate, in
which event Neurogen shall hold Pfizer free, clear and harmless from any and all
costs and expenses of such litigation, including attorney's fees, and any sums
recovered in any such suit or in its settlement shall belong to Neurogen.
[___________] Each party shall have the right to be represented by counsel of
its own selection and at its own expense in any suit instituted by the other for
infringement under the terms of this Section 8.4. If Pfizer lacks standing and
Neurogen has standing to bring any such suit, action or proceeding, then
Neurogen shall do so at the request of Pfizer and at Pfizer's expense.

          8.5  Defense of Infringement Claims.  Neurogen will cooperate with
Pfizer at Pfizer's request and expense in the defense of any suit, action or
proceeding against Pfizer or any sublicensee of Pfizer 

                                       26
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

alleging the infringement of the intellectual property rights of a Third Party
by reason of the manufacture, use or sale of a Product. Pfizer shall give
Neurogen prompt written notice of the commencement of any such suit, action or
proceeding or claim of infringement and will furnish Neurogen a copy of each
communication relating to the alleged infringement. Neurogen shall give to
Pfizer all authority (including the right to exclusive control of the defense of
any such suit, action or proceeding and the exclusive right, after consultation
with Neurogen, to compromise, litigate, settle or otherwise dispose of any such
suit, action or proceeding), information and assistance necessary to defend or
settle any such suit, action or proceeding; provided, however, Pfizer shall
obtain Neurogen's prior consent to such part of any settlement which requires
payment or other action by Neurogen of adversely affects Neurogen's business. If
the Parties agree that Neurogen should institute or join any suit, action or
proceeding pursuant to this Section 8.5, Pfizer may, at Pfizer's expense, join
Neurogen as a defendant if necessary or desirable, and Neurogen shall execute
all documents and take all other actions, including giving testimony, which may
reasonably be required in connection with the prosecution of such suit action or
proceeding.

          8.6  Hold Harmless.  Neurogen agrees to defend, protect, indemnify and
hold harmless Pfizer and any sublicensee of Pfizer, from and against any loss or
expense arising from any proven claim of a Third Party that it has been granted
rights by Neurogen and that Pfizer or any sublicensee of Pfizer in exercising
their rights granted to Pfizer by Neurogen pursuant to this Agreement, has
infringed upon such rights granted to such Third Party by Neurogen.

          8.7  Third Party Licenses.  If the manufacture, use or sale by Pfizer
or Neurogen, as the case may be, of a Product in any country would, in the
opinion of both Pfizer and Neurogen, infringe a patent owned by a Third Party
which covers substantially the same subject matter covered by any Neurogen
Technology, Pfizer and Neurogen shall attempt to obtain a license under such
patent.  [_____________

                                       27
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

_______________] All such computations, payments, and adjustments shall be on a
country by country and patent by patent basis.

          8.8  Abandoned Products.  With respect to Abandoned Products, Neurogen
shall have those rights and duties ascribed to Pfizer and Pfizer shall have
those rights and duties ascribed to Neurogen in this Article 8.

                                   ARTICLE 9

                                CONFIDENTIALITY

          9.1  Confidentiality.

               (a) Pfizer and Neurogen each recognize that the other's 
Confidential Information constitutes highly valuable, confidential information.
Pfizer and Neurogen each agree that during the term of this Agreement and for
five (5) years thereafter, it will keep confidential, and will cause its
Affiliates to keep confidential, all Neurogen Confidential Information or Pfizer
Confidential Information, as the case may be, that is disclosed to it or to any
of its Affiliates pursuant to this Agreement.

               (b) Pfizer and Neurogen each agree that any disclosure of the 
others Confidential Information to any officer, employee or agent of the other
Party or of any of its Affiliates shall be made only if and to the extent
necessary to carry out its responsibilities under this Agreement and shall be
limited to the maximum extent possible consistent with such responsibilities.
Pfizer and Neurogen each agree not to use the other's Confidential Information
for any purpose except for those purposes expressly permitted under this
Agreement. Pfizer and Neurogen each agree not to disclose the other's
Confidential Information to any Third Parties under any circumstance without
written permission from the other Party. Each Party shall take such action and
shall cause its Affiliates to take such action, to preserve the confidentiality
of each other's Confidential Information as it would customarily take to
preserve the confidentiality of its own Confidential Information. Each Party,
upon the other's request, will return all the Confidential Information disclosed
to the other Party pursuant to this Agreement, including all copies and extracts
of documents, within sixty (60) days of the request upon the termination of this
Agreement except for one (1) copy which may be kept for the purpose of complying
with continuing obligations under this Agreement.

                                       28
<PAGE>
 
          9.2  Publicity.  Except as required by law, neither Party may disclose
the terms of this Agreement without the written consent of the other Party,
which consent shall not be unreasonably withheld.

                                   ARTICLE 10

                                  TERMINATION

          10.1 Term.  This Agreement shall become effective on the Effective
Date and shall remain in effect with respect to each Product until the
expiration of the last royalty or Profit-sharing obligation with respect to such
Product, as provided in Section 5.6.  If the Parties Co-Promote any Product,
this Agreement shall survive for so long as such Co-Promotion continues.

          10.2 Events of Termination.  The following event shall constitute an
event of termination ("Event of Termination"):

               (a) Neurogen or Pfizer shall fail in any material respect to 
perform or observe this Agreement or the Research Agreement and any such failure
shall remain unremedied for thirty (30) days after written notice to the failing
Party.

          10.3 Termination.  Upon the occurrence of any Event of Termination,
the Party not responsible may, by notice to the other Party, terminate this
Agreement.

          10.4 Surviving Rights and Obligations.   Termination of this Agreement
for any reason shall be without prejudice to:

               (a) The rights and obligations of the Parties provided in 
Article 9 (Confidentiality) and Article 11 (Indemnification);

               (b) Neurogen's rights to receive all royalty and other payments
accrued hereunder; and

               (c) Any other remedies which either Party may otherwise have.


                                   ARTICLE 11

                                INDEMNIFICATION

          11.1 Indemnification.  Pfizer will indemnify Neurogen for damages,
settlement, costs, legal fees and other expenses incurred in connection with a
claim against Neurogen based on any action or omission of Pfizer, its agents,
employees or sublicensees related to the development 

                                       29
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

or commercialization of Products or other performance of this Agreement
provided, however, that the forgoing shall not apply (i) if the claim is found
to be based upon the negligence, recklessness or willful misconduct of Neurogen,
or (ii) if Neurogen fails to give Pfizer prompt notice of any claim it receives
and such failure materially prejudices Pfizer with respect to any claim or
action to which Pfizer's obligation pursuant to this Section applies. Pfizer, in
its sole discretion, shall choose legal counsel, shall control the defense of
such claim or action, and shall have the right to settle same on such terms and
conditions it deems advisable; provided, however, it shall obtain Neurogen's
prior consent to such part of any settlement which requires payment or other
action by, or is likely to have a material adverse effect on Neurogen's business
or its economic benefit under this Agreement. Pfizer will name Neurogen as an
additional insured on all clinical trial liability or product liability
insurance relating to Products.

                                   ARTICLE 12

                                 MISCELLANEOUS

          12.1 Entire Agreement; Other Agreements. Concurrently with the
execution of this Agreement, Neurogen and Pfizer shall enter into the Research
Agreement and the Stock Purchase Agreement.   [_____________]

          12.2 Notices.  All notices shall be in writing mailed via certified
mail, return receipt requested, courier, or facsimile transmission addressed as
follows, or to such other address as may be designated from time to time:

          If to Pfizer:  To Pfizer at its address as set forth at the beginning
          of this Agreement,

          attention:  President, Central Research
          with a copy to: Office of the General Counsel.

                                       30
<PAGE>
 
          If to Neurogen: To Neurogen at its address as set forth at the
          beginning of this Agreement,

          attention: President
          with a copy to: Vice President - Finance

          Notices shall be deemed given as of the date received.

          12.3 Governing Law.  This Agreement shall be governed by and construed
in accordance with the laws of the State of New York.

          12.4 Binding Effect.  This Agreement shall be binding upon and inure
to the benefit of the Parties and their respective successors and permitted
assigns.

          12.5 Headings.  Paragraph headings are inserted for convenience of
reference only and do not form a part of this Agreement.

          12.6 Counterpart.  This Agreement may be executed in two or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

          12.7 Amendment; Waiver; etc.  This Agreement may be amended, modified,
superseded or canceled, and any of the terms may be waived, only by a written
instrument executed by each Party or, in the case of waiver, by the Party or
Parties waiving compliance.  The delay or failure of any Party at any time or
times to require performance of any provisions shall in no manner affect the
rights at a later time to enforce the same.  No waiver by any Party of any
condition or of the breach of any term contained in this Agreement, whether by
conduct, or otherwise, in any one or more instances, shall be deemed to be, or
considered as, a further or continuing waiver of any such condition or of the
breach of such term or any other term of this Agreement.

          12.8 No Third Party Beneficiaries.  No Third Party, including any
employee of any Party to this Agreement, shall have or acquire any rights by
reason of this Agreement. Nothing contained in this Agreement shall be deemed to
constitute the Parties partners with each other or any Third Party.

                                       31
<PAGE>
 
          12.9 Assignment and Successors.  This Agreement may not be assigned by
either Party, except that each Party may assign this Agreement and the rights
and interests of such Party in whole or in part to any of its Affiliates, any
purchaser of all or substantially all of its assets or to any successor
corporation resulting from any merger or consolidation of such Party with or
into such corporations.

          12.10  Force Majeure.  Neither Pfizer nor Neurogen shall be liable for
failure of or delay in performing obligations set forth in this Agreement and
neither shall be deemed in breach of its obligations, if such failure or delay
is due to natural disasters or any causes reasonably beyond the control of
Pfizer or Neurogen.

          12.11  Severability.   If any provision of this Agreement is or
becomes invalid or is ruled invalid by any court of competent jurisdiction or is
deemed unenforceable, it is the intention of the Parties that the remainder of
the Agreement shall not be affected.

          In Witness Whereof, the Parties have caused this Agreement to be
executed by their duly authorized representatives.


Pfizer Inc.                           Neurogen Corporation



By:  /s/ George M. Milne, Jr.         By:  /s/ Harry H. Penner, Jr.
   -----------------------------          ----------------------------- 
   George M. Milne, Jr.                   Harry H. Penner, Jr.
   President, Pfizer Central Research     President and Chief Executive
                                          Officer

                                       32
<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

                                                                      Appendix X

                                PFIZER/NEUROGEN
                           NPY Project Collaboration

                    [______________________________________]


<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED


                                Development Plan
                                    NGD 95-1

                    [______________________________________]


<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED

Current Anticipated Responsibilities:

                    [______________________________________]


<PAGE>
 
                                                CONFIDENTIAL TREATMENT REQUESTED


                                    NGD 95-1
                    STRATEGY FOR EARLY CLINICAL DEVELOPMENT

                    [______________________________________]




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