<PAGE>   1
                                                                    EXHIBIT 10.3

         Portions of this Exhibit have been redacted and are the subject of a
confidential treatment request filed with the Secretary of the Securities and
Exchange Commission.
<PAGE>   2
                              TRIPARTITE AGREEMENT

         This TriPartite Agreement ("Agreement") is made as of the Effective
Date (as hereafter defined), by and among OSI Pharmaceuticals, Inc., a Delaware
corporation with its principal offices at 106 Charles Lindbergh Boulevard,
Uniondale, New York 11553-36549 (together with its Affiliates (as hereinafter
defined) unless the context otherwise requires, "OSI"), Genentech, Inc., a
Delaware corporation with its principal offices at 1 DNA Way, South San
Francisco, California 94080 ("Genentech"), and F.Hoffmann-La Roche Ltd, a Swiss
corporation with its principal offices at Grenzacher Strasse 124, CH-4070-Basel,
Switzerland (together with its Affiliates (as hereinafter defined) unless the
context otherwise requires, "Roche"). OSI, Genentech and Roche are sometimes
referred to herein individually as a "Party" and collectively as the "Parties."

                                    RECITALS

         1. OSI has participated in the development of a certain molecule known
as OSI-774 (defined below) and has certain intellectual property rights related
thereto.

         2. Genentech, OSI and Roche each wish to conduct development of OSI-774
with Genentech and OSI emphasizing activities in the U.S. and Roche emphasizing
activities in Europe.

         3. The Parties wish to set up a structure which is intended to
generally result in the optimization of the use of the Parties' resources to
develop OSI-774 globally and to share Global Development Costs (as defined in
Exhibit A hereof) on a 1/3, 1/3, 1/3 basis and facilitate their sharing of
information about OSI-774.
<PAGE>   3
         4. OSI is party to an agreement with Genentech (the "OSI-Genentech
Agreement") and OSI is a party to an agreement with Roche (the "OSI-Roche
Agreement").

         5. To further their purposes, the Parties' personnel will participate
in various Teams and Committees as set forth in the charts on Exhibit B, and

         6. OSI and Roche will, pursuant to the OSI-Roche Agreement, conduct
development activities which will not be covered by the Global Development Plan.

         7. OSI and Genentech will, pursuant to the OSI-Genentech Agreement,
conduct development activities which will not be covered by the Global
Development Plan

                                    AGREEMENT

         NOW, THEREFORE, in consideration of the premises and mutual covenants
and agreements herein contained and for other good and valuable consideration,
the receipt and sufficiency of which is hereby acknowledged, the Parties,
intending to be legally bound hereby, do hereby agree as follows:

                                   ARTICLE 1.

                                   DEFINITIONS

         Section 1.1 "AFFILIATE" shall mean any corporation, firm, limited
liability company, partnership or other entity which directly or indirectly
controls or is controlled by or is under common control with a Party to this
Agreement. For the purposes of this Section 1.1, "control" means ownership,
directly or through one or more Affiliates, of fifty percent (50%) or more or
the shares of stock entitled to vote for the election of directors, in the case
of a corporation, or fifty percent (50%) or more of the equity interests in the
case of any other type of legal entity,


                                       2
<PAGE>   4
status as a general partner in any partnership, or any other arrangement whereby
a party controls or has the right to control the Board of Directors or
equivalent governing body of a corporation or entity. For the purposes of this
Agreement, Genentech shall be deemed to not be an Affiliate of Roche.

         Section 1.2 "EFFECTIVE DATE" shall mean the date of execution of the
OSI-Roche Agreement and OSI-Genentech Agreement.

         Section 1.3 "GLOBAL DEVELOPMENT COMMITTEE" shall mean that body
established pursuant to Section 3.1 hereof.

         Section 1.4 "GLOBAL DEVELOPMENT COSTS" shall have the meaning set forth
in Exhibit A.

         Section 1.5 "GLOBAL DEVELOPMENT COUNTRIES" shall mean **

         Section 1.6 "GLOBAL DEVELOPMENT PLAN", which in its initial form is
attached as Exhibit C, shall mean the plan for development of OSI-774, as
amended from time to time (e.g. to take into account feedback from key
regulatory authorities of the Global Development Countries.

         Section 1.7 "OSI-774" shall mean the selective inhibitor of epidermal
growth factor receptor having the IUPAC name
[6,7-bis(2-methoxyethoxy)quinazolin4-y1]-(3-ethynylphenyl)-amine having the U.S.
Approved Name erlotinib.



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** This portion has been redacted pursuant to a confidential treatment request.


                                       3
<PAGE>   5
         Section 1.8 "OSI/GENENTECH JOINT PROJECT TEAM" shall mean that body
established pursuant to the OSI-Genentech Agreement.

         Section 1.9 "ROCHE PROJECT TEAM" shall mean that body established
pursuant to the OSI-Roche Agreement.

         Section 1.10 "TRIPARTITE LICENSED PRODUCT" shall mean pharmaceutical
formulations of OSI-774 (including, without limitation, prodrugs, salts,
solvates and polymorphs of all the above in any form or formulation).

                                   ARTICLE 2.

                             GLOBAL GOALS AND PLANS

         Section 2.1 GLOBAL GOALS. The Parties agree, pursuant and subject to
the terms of this Agreement, to set up a structure which is intended to
generally result in the optimization of the use of the Parties' resources to
develop OSI-774 in the Global Development Countries and share Global Development
Costs on a 1/3, 1/3, 1/3 basis, to share information generated under the Global
Development Plan to facilitate the obtaining of Regulatory Approval of OSI-774
Products in commercially significant indications as soon as reasonably
practicable for commercial marketing and sale in the world and to work together
on such other matters as the Global Development Committee shall determine. The
Parties shall also coordinate matters concerning manufacturing of supplies for
all development purposes.

         Section 2.2 GLOBAL DEVELOPMENT PLAN - MODIFICATIONS. The Parties have
attached hereto as Exhibit C the initial Global Development Plan, pursuant to
which, among other things, each Party will spend up to $100,000,000 for the
further development of OSI-774. Hereafter, the


                                       4
<PAGE>   6
Global Development Plan (including the work, budget and timeline therefor) shall
not be modified except upon formal decision by the OSI-774 Liaison Team and
approval by the Global Development Committee as described in Section 3.1(c)
below, which formal approval shall automatically constitute a valid binding
amendment to Exhibit C attached hereto. The Global Development Plan will be
updated annually.

                                   ARTICLE 3.

                              TRIPARTITE MANAGEMENT

     Section 3.1 GLOBAL DEVELOPMENT COMMITTEE.

         (a) ESTABLISHMENT OF THE GLOBAL DEVELOPMENT COMMITTEE. The Parties
hereby establish a Global Development Committee or GDC for directing the
development of OSI-774. The GDC will be composed of up to two (2)
representatives of each Party, who shall be appointed (and may be replaced at
any time) by such Party on written notice to the other party in accordance with
this Agreement. Such representatives shall include individuals within the senior
management of each Party with expertise in pharmaceutical drug development. The
initial GDC members from each Party are listed on Exhibit D attached hereto. Any
member of the GDC may designate a substitute to attend and perform the functions
of that member at any meeting of the GDC. The GDC will meet at least twice each
year during the Term of this Agreement, or at any frequency agreed by the GDC
and will operate by unanimous vote. In any event, the GDC will meet thirty (30)
days after the execution of this Agreement or as soon as practicable as mutually
agreed by the Parties. The representatives from each Party will collectively
have one vote in decisions.


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<PAGE>   7
         (b)  GLOBAL DEVELOPMENT COMMITTEE RESPONSIBILITIES. The GDC shall
perform the following functions:

              (i)    approve material changes to the Global Development Plan
     including the approval of an annual budget

              (ii)   oversee execution of the Global Development Plan

              (iii)  resolve disputes concerning overall strategy or funding

              (iv)   provide guidance to the OSI-774 Liaison Team

              (v)   approve the handling of budget issues, in particular,
     significant variances from the approved annual budget

              (vi)  Resolve disputes arising in the OSI-774 Liaison Team
     including, without limitation, determining which clinical and pre-clinical
     activities should be done, as well as sourcing material for such activity

              (vii)  perform such other functions as appropriate to further the
     purposes of this Agreement, as determined by the Parties

         (c)  GLOBAL DEVELOPMENT COMMITTEE PROCEDURES. Initially, OSI shall
designate a Chairperson who will serve as such for the first year. Thereafter,
the Chairperson shall be determined by the Global Development Committee. The
Chairperson shall send notices and agendas for all regular GDC meetings to all
GDC members. The location of regularly scheduled GDC meetings shall alternate
among the offices of the Parties, unless otherwise agreed. Meetings may be held
telephonically, but each member shall attend at least one meeting


                                       6
<PAGE>   8
in person each year. The Party hosting any GDC meeting shall appoint one person
(who need not be a member of the GDC) to attend the meeting and record the
minutes of the meeting. Such minutes shall be circulated to the Parties promptly
following the meeting for review, comment and distribution. Any modifications to
the Global Development Plan (including the work, budget and timeline therefor)
approved at a GDC meeting shall be considered approved and shall constitute an
amendment to Exhibit C upon ratification of the meeting minutes related thereto.
In addition, any study referred to in Section 3.1(d) that is conducted shall be
included in the Global Development Plan.

         (d)  DISPUTE RESOLUTION. **

     Section 3.2 OSI-774 LIAISON TEAM.

         (a) OSI-774 LIAISON TEAM. The Parties have established the OSI-774
Liaison Team to liaise between the Roche Project Team and the OSI/Genentech
Joint Project Team which will be composed of one representative of each Party
(who should be the head of the applicable Project Team) who has been appointed
by each Party (and may be replaced at any time by such Party) on written notice
to the other Parties in accordance with this Agreement. Each member may utilize
and bring to meetings other personnel from such member's company. The members
shall communicate frequently and outside of formal meetings. Ongoing
communication and updates will be provided to the Parties as the Global
Development Plan unfolds. Any member of the OSI-774 Liaison Team may designate a
substitute to attend and


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** This portion has been redacted pursuant to a confidential treatment request.


                                       7
<PAGE>   9
perform the functions of that member in any meeting of the OSI-774 Liaison Team.
The OSI-774 Liaison Team will coordinate the activities of the Project Teams of
the Parties and closely interact to establish key logistical parameters for the
Global Development Plan.

         (b)  OSI-774 LIAISON TEAM. The OSI-774 Liaison Team shall perform the
following functions:

              (i)    coordination of pre-clinical activities

              (ii)   coordination of clinical team activity

              (iii)  coordination of regulatory activity

              (iv)   coordination of manufacturing activity to, among other
     things, assure that if there is more than one manufacturer there is
     uniformity as to specifications and formulations being manufactured

              (v)    coordination of communication and publication strategy

              (vi)   preparation of budgets and updates to present to the GDC

              (vii)  prioritization and allocation of supply of OSI-774

              (viii) such other matters as directed by the Global Development
     Committee

              (ix)   Such other matters set forth in Exhibit C hereto

         (c)  OSI-774 LIAISON TEAM PROCEDURES. OSI-774 Liaison Team meetings
shall take place by telephone or video conference or in person on an as needed
basis. In addition,


                                       8
<PAGE>   10
the OSI-774 Liaison Team shall meet in person at least once a year. The Party
hosting any meeting shall appoint one person (who need not be a member of the
Committee) to attend the formal meetings and record the minutes of the meeting.
Such minutes shall be circulated to the Parties promptly following the meeting
for review, comment and distribution.

         (d)  DISPUTE RESOLUTION. For issues coming before the OSI-774 Liaison
Team for which the Parties' OSI-774 Liaison Team members have disagreements,
decision-making authority will rest with the Global Development Committee for
dispute resolution under Section 3.1(d).

     Section 3.3 ACCOUNTING AND FINANCIAL REPORTING. Each Party will appoint
a representative with expertise in the areas of accounting, cost allocation,
budgeting and financial reporting. Such representatives shall work under the
direction of the OSI-774 Liaison Team to provide services to and consult with
the OSI-774 Liaison Team in order to address the financial, budgetary and
accounting issues which arise in connection with the Global Development Plan and
the Financial Planning, Accounting and Reporting Procedures attached hereto as
Exhibit A. Each representative may designate a substitute to perform such
functions or may be replaced at any time by the representative Party providing
notice thereof to the other Party.

                                   ARTICLE 4.

                         COVENANTS, TERM AND TERMINATION

     Section 4.1 REASONABLE EFFORTS. Subject to the terms and conditions of
the OSI-Genentech Agreement, OSI-Roche Agreement and this Agreement, each of the
Parties agrees to use all reasonable efforts to take, or cause to be taken, all
reasonable actions and to do, or cause


                                       9
<PAGE>   11
to be done, all things necessary and appropriate to consummate the transactions
contemplated by such Agreement in accordance with the terms thereof.

     Section 4.2 TERMINATION. This Agreement shall commence as of the
Effective Date and shall terminate when either the OSI-Genentech Agreement or
the OSI-Roche Agreement shall terminate.

                                   ARTICLE 5.

                              TRANSFER OF MATERIALS

         Each Party may transfer certain of its proprietary materials to the
other Parties. Each Party agrees that it will use such materials of the other
Parties only for the purposes of the OSI-Genentech Agreement, the OSI-Roche
Agreement or this Agreement, as the case may be, and will not transfer such
materials to any third party without the prior written consent of the
transferring Party. Except as expressly provided in the OSI-Roche Agreement, the
OSI-Genentech Agreement or this Agreement, the transfer of any such proprietary
materials by one Party to another shall not be deemed to be a grant of any
rights in the proprietary material. All right, title and interest in and to all
such proprietary materials (and any patent rights relating thereto) shall remain
in the Party transferring such materials

                                   ARTICLE 6.

                                 CONFIDENTIALITY

     Section 6.1 CONFIDENTIALITY. Except to the extent expressly authorized
by this Agreement or otherwise agreed in writing, the Parties agree that, for
the Term of this Agreement and for five (5) years thereafter, the receiving
Party shall keep confidential and shall not publish or otherwise disclose or use
for any purpose other than as permitted under this Agreement any


                                       10
<PAGE>   12
Know-how (as defined in each of the OSI-Genentech Agreement and OSI-Roche
Agreement) and other proprietary information and materials furnished to it by
any other Party pursuant to this Agreement (collectively, "Confidential
Information"), except to the extent that it can be established by the receiving
Party that such Confidential Information:

         (a) was already known to the receiving Party as demonstrated by written
records, other than under an obligation of confidentiality, at the time of
disclosure by the other Party as demonstrated by competent written records;

         (b) was generally available to the public or otherwise part of the
public domain at the time of its disclosure to the receiving Party;

         (c) became generally available to the public or otherwise part of the
public domain after its disclosure and other than through any act or omission of
the receiving Party in breach of this Agreement;

         (d) was disclosed to the receiving Party, other than under an
obligation of confidentiality, by a third party who had no obligation to the
disclosing Party not to disclose such information to others; or

         (e) was subsequently developed by the receiving Party without use of
the Confidential Information as demonstrated by competent written records.

     Section 6.2 AUTHORIZED DISCLOSURE. Each Party may disclose Confidential
Information hereunder to the extent such disclosure is required to comply with
applicable governmental regulations or conduct pre-clinical or clinical trials
or to the extent ordered by a court of competent jurisdiction (subject to an
appropriate protection order) under the Global


                                       11
<PAGE>   13
Development Plan, provided that if a Party is required by law or regulation to
make any such disclosure of any other Party's Confidential Information it will
give reasonable advance notice to such other Party of such disclosure
requirement and will use its reasonable best efforts to secure confidential
treatment of such Confidential Information required to be disclosed. In
addition, each Party shall be entitled to disclose, under a binder of
confidentiality containing provisions substantially as protective as those of
this Article 6, Confidential Information to its consultants, clinical
investigators and contract manufacturers but only for any purposes provided for
in the Global Development Plan.

     Section 6.3 SURVIVAL. This Article 6 shall survive the termination or
expiration of this Agreement for a period of **

     Section 6.4 TERMINATION OF PRIOR AGREEMENTS. As of the Effective Date
hereof, this Agreement supersedes the Confidentiality Agreement between OSI and
Roche dated September 25, 2000 and the Confidentiality Agreement between OSI and
Genentech dated August 4, 2000 (the "Confidentiality Agreements"), but only
insofar as the Confidentiality Agreements relate to the subject matter of this
Agreement. All Confidential Information (as defined in the Confidentiality
Agreements) exchanged between the Parties under the Confidentiality Agreements
relating to the subject matter of this Agreement shall be deemed Confidential
Information hereunder and shall be subject to the terms of this Article 6.


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** This portion has been redacted pursuant to a confidential treatment request.


                                       12
<PAGE>   14
                                   ARTICLE 7.

                          REPRESENTATION AND WARRANTIES

     Section 7.1 REPRESENTATIONS AND WARRANTIES.

         (a) Each of the Parties hereby represents and warrants that this
Agreement is a legal and valid obligation binding upon such Party and
enforceable in accordance with its terms. The execution, delivery and
performance of the Agreement by such parties does not conflict with any
agreement, instrument or understanding, oral or written to which it is a party
or by which it is bound nor violate any law or regulation of any Court,
government body or administrative agency having any jurisdiction over it.

         (b) Each Party has not, and during the Term of the Agreement will not,
grant any rights related to Tripartite Licensed Products to any Third Party
which would conflict with the rights granted to any other Party hereunder or
under the OSI-Roche Agreement, OSI-Genentech Agreement or the Divestiture
Agreement (as defined in the OSI-Roche Agreement and OSI-Genentech Agreement),
whether by execution of or amendment to any agreement or otherwise.


                                       13
<PAGE>   15
                                   ARTICLE 8.

                             INFORMATION AND REPORTS

         Section 8.1 SAFETY DATA BASE. The Parties will, as soon as practical,
organize a serious adverse event data base (the "SAE Data Base") that meets
regulatory requirements in each of the Global Development Countries.

         Section 8.2 CRO DATA BASE. All data which may include, without
limitation, database information, safety reports and final reports from such
clinical trials under the Global Development Plan for Tripartite Licensed
Products under (i) the OSI-Genentech Agreement, (ii) the OSI-Roche Agreement and
** All such clinical trial data and information shall be accessible to the
Parties. If a Party itself conducts a clinical trial under the Global
Development Plan, it shall transfer all of the clean, final data for such trial
to ** no later than six (6) months after the date that the last trial data has
been collected under the trial protocol for the last clinical trial subject. The
OSI-774 Liaison Team shall coordinate the transfers of any such data.



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** This portion has been redacted pursuant to a confidential treatment request.


                                       14
<PAGE>   16
                                   ARTICLE 9.

                              INTELLECTUAL PROPERTY

     Section 9.1 SOLE AND JOINT INVENTIONS. The Parties recognize that any
Party may make, separately or jointly with another Party, inventions during the
course of the activities under the Global Development Plan ("OSI-774
Inventions"). In such event, the Parties' rights to OSI-774 Inventions and any
patent applications and patents thereon made by a Party solely or jointly with
either or both of the other Parties will be governed by the OSI-Genentech
Agreement and the OSI-Roche Agreement.

     Section 9.2 GRANT OF RIGHTS TO STEP-IN.

         (a) The Parties acknowledge that OSI has secondary rights pursuant to
the OSI-Genentech Agreement to file, prosecute, maintain and enforce patent
applications and patents for certain Genentech OSI-774 Inventions, if Genentech
declines to exercise its primary rights to such actions. If OSI elects not to
exercise its secondary rights, Genentech and OSI grant Roche the right to file,
prosecute and maintain patent applications and patents for such OSI-774
Inventions and to enforce patents for such OSI-774 Inventions.

         (b) The Parties acknowledge that OSI has secondary rights pursuant to
the OSI-Roche Agreement to file, prosecute, maintain and enforce patent
applications and patents for certain Roche OSI-774 Inventions, if Roche declines
to exercise its primary rights to such actions. If OSI elects not to exercise
its secondary rights, Roche and OSI grant Genentech the right to file, prosecute
and maintain patent applications and patents for such OSI-774 Inventions and to
enforce patents for such OSI-774 Inventions. This Section 9.2 shall survive any
expiration or termination of this Agreement.


                                       15
<PAGE>   17
         Section 9.3 ENFORCEMENT OF PATENTS FOR GENENTECH-OSI-ROCHE JOINT
INVENTIONS. In the event of an infringement of a patent for a
Genentech-OSI-Roche joint invention, the Parties shall decide the best way for
the Parties to proceed.



                                  ARTICLE 10.

                                  MISCELLANEOUS

         Section 10.1 FURTHER ACTIONS. Each Party agrees to execute, acknowledge
and deliver such further instruments, and to do all such other acts, as may be
necessary or appropriate in order to carry out the purposes and intent of this
Agreement.

         Section 10.2 PUBLICITY REVIEW. The Parties agree that the public
announcement of the execution of the OSI-Genentech Agreement, the OSI Roche
Agreement and this Agreement shall be in the form of a press release to be
agreed upon on or before the Effective Date and thereafter each Party shall be
entitled to make or publish any public statement consistent with the contents
thereof. Thereafter, the Parties will jointly discuss and agree on any statement
to the public regarding the Global Development Plan or any aspect of the Global
Development Plan, and the results of clinical studies conducted thereunder,
subject in each case to disclosure otherwise required by law or regulation as
determined in good faith by each Party. When a Party elects to make any such
statement it will give at least five (5) applicable day's notice, unless
disclosure is required by law in a shorter period of time, to the other Parties
to review and comment on such statement.


                                       16
<PAGE>   18
         Section 10.3 PUBLICATIONS. Except as required by law, each Party agrees
that it shall not publish or present the results of studies or clinical trials
carried out by such Party under the Global Development Plan without the
opportunity for prior review by the other Parties. Each Party shall provide to
the other Parties the opportunity to review any of the submitting Party's
proposed abstracts, manuscripts or presentations (including information to be
presented verbally) which relate to the Field under either the OSI-Genentech
Agreement or the OSI-Roche Agreement, as the case may be, at least thirty (30)
days prior to their intended submission for publication, and such submitting
Party agrees, upon written request from any other Party, not to submit such
abstract or manuscript for publication or to make such presentation until such
other Party is given up to forty-five (45) days from the date of such written
request to seek appropriate patent protection for any material in such
publication or presentation which it reasonably believes is patentable. Once
such abstracts, manuscripts or presentations have been reviewed by each Party
and have been approved for publication, the same abstracts, manuscripts or
presentations do not have to be provided again to any Party for review for a
later submission for publication. Expedited reviews for abstracts or poster
presentations within ten (10) days of receipt by a Party may be arranged by
sending a prior written notice to the other Parties requesting such expedited
review, unless another arrangement is mutually agreed upon by the Parties. Each
Party also shall have the right to require that its Confidential Information
that may be disclosed in any such proposed publication be deleted prior to such
publication. In the event that any Party submits any manuscript or other
publication relating to any Tripartite Licensed Product under either the
OSI-Genentech Agreement or OSI-Roche Agreement, it will consider and acknowledge
the contributions of the other Parties, including, as appropriate,
co-authorship.


                                       17
<PAGE>   19
         Section 10.4 NOTICES. All notices hereunder shall be in writing and
shall be deemed given if delivered personally or by facsimile transmission
(receipt verified), telexed, mailed by registered or certified mail (return
receipt requested), postage prepaid, or sent by express courier service, to the
Parties at the following addresses (or at such other address for a Party as
shall be specified by like notice, provided, that notices of a change of address
shall be effective only upon receipt thereof).

                   If to OSI:

                            OSI Pharmaceuticals, Inc.
                            106 Charles Lindbergh Boulevard
                            Uniondale, NY 11553
                            Attention: President
                            Telecopy:  (516) 745-6429

                   With a copy to:

                            Mintz Levin Cohn Ferris Glovsky and Ferris, P.C.
                            666 Third Avenue
                            New York, NY 10017
                            Attn: Joel Papernik, Esq.
                            Telecopy:  (212) 983-3115

                   If to Genentech:

                            Genentech, Inc.
                            1 DNA Way
                            South San Francisco, CA 94080
                            Attention: Corporate Secretary
                            Telecopy: (650) 952-9881

                   If to F.Hoffman-La Roche Ltd:

                            Grenzacher Strasse 124
                            CH-4070-Basel
                            Switzerland
                            Attention:  Corporate Law
                            Telecopy: 41-61-688-13-96


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<PAGE>   20
         Section 10.5 WAIVER. Except as specifically provided for herein, the
waiver from time to time by either of the Parties of any of their rights or
their failure to exercise any remedy shall not operate or be construed as a
continuing waiver of same or of any other of such Party's rights or remedies
provided in this Agreement.

         Section 10.6 SEVERABILITY. If any term, covenant or condition of this
Agreement or the application thereof to any Party or circumstance shall, to any
extent, be held to be invalid or unenforceable, then (a) the remainder of this
Agreement, or the application of such term, covenant or condition to Parties or
circumstances other than those as to which it is held invalid or unenforceable,
shall not be affected thereby and each term, covenant or condition of this
Agreement shall be valid and be enforced to the fullest extent permitted by law;
and (b) the Parties hereto covenant and agree to renegotiate any such term,
covenant or application thereof in good faith in order to provide a reasonable
acceptable alternative to the term, covenant or condition of this Agreement or
the application thereof that is invalid or unenforceable, it being the intent of
the Parties that the basic purposes of this Agreement are to be effectuated.

         Section 10.7 GOVERNING LAW. This Agreement shall be governed by, and
construed in accordance with, the laws of the State of New York.

         Section 10.8 AMBIGUITIES. Ambiguities, if any, in this Agreement shall
not be construed against any Party, irrespective of which Party may be deemed to
have authorized the ambiguous provision.

         Section 10.9 HEADINGS. All headings are for reference purposes only and
shall not in any way affect the meaning or interpretation of this Agreement.


                                       19
<PAGE>   21
         Section 10.10 COUNTERPARTS. This Agreement may be executed in two (2)
or more counterparts, each of which shall be deemed an original, but all of
which together shall constitute one and the same instrument.

         Section 10.11 ENTIRE AGREEMENT. This Agreement, including all Exhibits
attached hereto which are hereby incorporated herein by reference, sets forth
all the covenants, promises, agreements, warranties, representations, conditions
and understandings between the Parties hereto with respect to the subject matter
hereof and supersedes and terminates all prior agreements and understandings
between the Parties, subject to Section 6.4 above with respect to prior
Confidentiality Agreements. There are no covenants, promises, agreements,
warranties, representations, conditions or understandings, either oral or
written, between the Parties with respect to the subject matter hereof other
than as set forth herein and therein. No subsequent alteration, amendment,
change or addition to this Agreement shall be binding upon the Parties hereto
unless reduced to writing and signed by the respective authorized officers of
the Parties.

         Section 10.12 CONFLICTS. If any provision of the OSI-Genentech
Agreement or the OSI-Roche Agreement conflicts with the provisions of this
Agreement, the provisions of this Agreement shall govern such conflict.

         Section 10.13 RIGHT TO CONDUCT OTHER STUDIES. Nothing in this Agreement
shall limit in any respect the right of each Party to itself and at its own
expense conduct clinical and pre-clinical activities for additional indications
for OSI-774 not called for under the Global Development Plan, provided that no
other Party reasonably has objected (after 60 days prior notice) and that no
such activity adversely affects the goals of the Global Development Plan or the
effectuation of the Global Development Plan, subject, in the case of OSI and
Genentech, to


                                       20
<PAGE>   22
the OSI-Genentech Agreement. Any serious adverse event safety data resulting
from these activities shall be part of the SAE Data Base. Any Party who did not
participate may buy the data by paying ** of the total cost of these activities.
Roche and OSI shall without prior notice to Genentech or Genentech's consent be
able to conduct development activities not covered by the Global Development
Plan outside of the Global Development Countries, but Genentech may nevertheless
buy the data from such activity by payment of ** of the total cost thereof.

         Nothing in this Agreement shall affect the right of OSI or Genentech to
conduct development of other epidermal growth factor receptor inhibitors under
the OSI-Genentech Agreement.


[This space is intentionally left blank]












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                                       21
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         IN WITNESS WHEREOF, the Parties have executed this Agreement in
duplicate originals by their proper officers as of the date and year first above
written.

<TABLE>
<S>                                                        <C>
OSI PHARMACEUTICALS, INC.                                  GENENTECH, INC.



By:    /s/ COLIN GODDARD                                   By:    /s/ ARTHUR D. LEVINSON
       ----------------------------------                         ----------------------
Name:  Colin Goddard                                       Name:  Arthur D. Levinson
       ----------------------------------                         ------------------
Title: Chairman & Chief Executive Officer                  Title: Chairman & Chief Executive Officer
       ----------------------------------                         ----------------------------------
</TABLE>



F.HOFFMANN-LA ROCHE LTD




By:    /s/ WERNER HENRICH
       ----------------------------------
Name:  Werner Henrich
       ----------------------------------
Title: Senior Vice President
       ----------------------------------



By:    /s/ RUDOLF SCHAFFNER
       ----------------------------------
Name:  Rudolf Schaffner
       ----------------------------------
Title: Vice President
       ----------------------------------


                                       22
<PAGE>   24
                                    EXHIBIT A

             Financial Planning, Accounting and Reporting Procedures


A.1.     GLOBAL DEVELOPMENT PLAN AND BUDGET

         The initial Global Development Plan and preliminary budget attached to
this Agreement as Appendix C shall be expanded into a ** long range Global
Development Plan, at the latest within six (6) months from the Effective Date,
which shall be updated on an annual basis ** Such Global Development Plan shall
be supplemented by a comprehensive budget which will project the related Global
Development Costs (as defined below) by quarters for the first running 8
calendar quarters and by year for the remaining ** on an indication by
indication basis, and shall be ratified by the GDC. The budget derived from the
Global Development Plan will be updated as a rolling development budget whenever
needed quarterly if changes in the Global Development Plan so require it, but at
least on an annual basis ** The rolling development budget will be developed in
a manner consistent with the accounting systems of each Party and will be
supplemented with detailed business plans for clinical trials and drug approval
applications as determined by the OSI-774 Liaison Team and ratified by the GDC.
The Global Development Plan and rolling development budget once approved by the
OSI-774 Liaison Team, and ratified by the GDC, can only be changed with the
approval of the OSI-774 Liaison Team, which change is ratified by the GDC as
provided in the Agreement. The rolling development budget shall identify
activities and costs in sufficient detail as agreed upon between the Parties to
allow an appropriate monitoring of expenses versus budget.



-------------------
** This portion has been redacted pursuant to a confidential treatment request.
<PAGE>   25
A.2.     GLOBAL DEVELOPMENT COSTS

         Global Development Costs shall mean the costs specifically attributable
to the development of a Tripartite Licensed Product and actually incurred under
the Global Development Plan after the Effective Date of the Agreement through
the date of termination as defined under the Tripartite Agreement, provided that
no Party shall be required to spend more than $100,000,000 unless otherwise
agreed to by the Parties. Such costs shall comprise those costs, both direct and
indirect including Development Allocable Overhead (i.e. fully burdened
development costs), required to obtain, expand and/or maintain the authorization
and/or ability to manufacture, formulate, fill, ship and/or sell a Tripartite
Licensed Product in commercial quantities in the Global Development Countries.

         Global Development Costs shall include but are not limited to costs of
development including cost of studies on the toxicological, pharmacokinetic,
metabolic or clinical aspects of a Tripartite Licensed Product conducted
internally or by individual investigators, or consultants, process development,
process improvement, qualification lots, costs for preparing, submitting,
reviewing or developing data or information necessary for the purpose of
submission to a governmental authority in order to obtain, expand and/or
maintain approval of a Tripartite Licensed Product in the Global Development
Countries.

         Global Development Costs shall include expenses for data management,
statistical designs and studies, document preparation, and other administration
expenses associated with the clinical testing program or post registration
clinical studies required to obtain, expand and/or maintain approvals in the
Global Development Countries.


                                      A-2
<PAGE>   26
Global Development Costs may include costs incurred in geographical areas other
than the Global Development Countries ** only to the extent that the activities
related with such costs are specifically included in the Global Development Plan
and budget, as ratified by unanimous vote of the Global Development Committee
and not subject to further dispute resolution, to be incurred in such
geographical areas for the purpose of generating data or information required to
obtain, expand and/or maintain approval of a Tripartite Licensed Product in the
Global Development Countries.

         Global Development Costs shall not include patent costs,
pre-registration marketing costs (e.g. trademark costs, advertising agency
selection costs, pre-marketing studies), post-registration clinical and
marketing studies which are not conducted as part of the Global Development
Plan.

         Global Development Costs shall include amounts equivalent to ** of the
development costs of each Party as defined above, in lieu of General and
Administrative Costs.

         In determining Global Development Costs, each Party will use its
respective project accounting systems with the purpose of tracking costs as much
as possible on a product indication-by-product indication basis, and will review
and approve its respective project accounting systems and methodologies with the
other Parties. In general, these project accounting systems report actual time
spent on specific projects, applying the actual labor costs, capture actual
costs of specific projects and allocate other expenses to projects.



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** This portion has been redacted pursuant to a confidential treatment request.


                                      A-3
<PAGE>   27
A.3.     DEVELOPMENT ALLOCABLE OVERHEAD

         Development Allocable Overhead shall mean costs incurred by a Party or
for its account which are attributable to a Party's supervisory, services,
occupancy costs, payroll, information systems, human resources or purchasing
functions and which are allocated to the development activities based on a space
occupied or headcount or other activity-based method. Development Allocable
Overhead shall not include any costs attributable to general corporate
activities including, by way of example, executive management, investor
relations, business development, legal affairs and finance.

A.4.     ADDITIONAL INDICATION OPT OUT - OPT BACK IN

         Each Party has the right to opt out of the development of an additional
indication for a Tripartite Licensed Product beyond the initial indications
included in the Global Development Plan for that Tripartite Licensed Product at
(and only at) the point of time when the GDC takes its formal decision to
include such additional indication in the Global Development Plan, subject, in
the case of OSI and Genentech, to the OSI-Genentech Agreement which might
require joint action by OSI and Genentech. Prior to such opt out decision, the
Parties shall have a good faith discussion about the reasons and consequences of
the opt out.

         The Global Development Costs related to an additional indication for
which a Party has opted out shall be equally shared between the Parties, or
solely supported by the Party, which have not elected to opt out.


                                      A-4
<PAGE>   28
         The Party electing to opt out of an additional indication will provide
the other Parties with ** notice prior to its election and will be obligated to
pay its share of the cost of all ongoing clinical and preclinical studies and
its share of other Global Development Costs already committed as of the date of
such notice. Thereafter the Party electing to opt out will not share any costs
or benefits of such additional indication within its on going share of the
Global Development Costs.

         In the event that a Party which previously opted out of an additional
indication wishes to regain its rights to such indication then it may regain
such rights by electing to do so at the latest within thirty days of the first
formal decision of the GDC to file for approval for that indication in the
Global Development Countries and by paying within thirty days, ** of the total
Global Development Costs incurred by the other Party or Parties for such
indication during the period of opt out and by thereafter assuming from the opt
back in date its ongoing obligations as if no opt out had occurred. Such payment
shall be shared in proportion to the amount expended by each Party who
contributed to the study.

A.5.     CHARGING, REPORTING, AND CONSOLIDATING OF GLOBAL DEVELOPMENT COSTS

         The Global Development Plan and rolling development budget as ratified
by the GDC for the Tripartite Licensed Product shall be the reference for
charging and sharing Global Development Costs.



-------------------
** This portion has been redacted pursuant to a confidential treatment request.


                                      A-5
<PAGE>   29
         The responsibility for the consolidated reporting of the Global
Development Costs to the OSI-774 Liaison Team shall be with OSI in close
cooperation with Roche and Genentech. The OSI-774 Liaison Team shall determine
the structure and the level of details which shall apply for the Parties to
report their incurred Global Development Costs to OSI for consolidation and to
allow an appropriate monitoring of expenses versus rolling development budget.
This will be the basis for Global Development Plan accounting and determining of
payments to the Parties.

         The Clinical Supplies for clinical studies of the Global Development
Program shall be charged as material costs, at Fully Burdened Manufacturing Cost
(excluding General and Administrative Costs), whether supplied by a Party or by
a Third Party. Fully Burdened Manufacturing Cost means one hundred percent
(100%) of a Party's manufacturing cost (in accordance with the Party's
accounting policies consistently applied), which shall comprise the cost of
goods produced as determined by the Party manufacturing or contracting with a
Third Party for each stage of the manufacturing process in accordance with GAAP
or IAS as consistently applied by such Party, including product quality
assurance/control costs, applicable Allocable Overhead, and other costs borne by
the Party for transport, customs clearance and storage of product at the request
of the other Party prior to the time of sale (i.e. freight, customs, duty and
insurance).







                                      A-6
<PAGE>   30
         Each Party shall report quarterly its incurred Global Development Costs
in US Dollars as early as possible, but no later than ** days after the last day
of the calendar quarter in question, and shall separately provide the quarterly
and year-to-date cumulative figures. Each Party shall report Global Development
Costs in a manner consistent with its project accounting system.

         As early as possible, but no later than ** days after the last day of
each calendar quarter, Genentech and Roche will provide OSI with financial
statements for their respective activities, prepared in accordance with the
terms contained in this Exhibit A in order for OSI to prepare the consolidated
reports. No later than ** after the last day of the calendar quarter OSI shall
provide Genentech and Roche with a copy of a reconciliation statement
identifying on an indication-by-indication basis the Global Development Costs
and the calculation serving as the basis of determining payments between the
Parties. Each quarterly report will be accompanied by and include reasonable
documentation which itemizes and explains the costs incurred as to allow
comparison to the ratified rolling development budget and provide details as
agreed upon by the Parties, in US Dollars, in a manner consistent with the
amounts budgeted for such activities.

     The financial representatives from the Parties will meet as appropriate but
at least quarterly either by telecon, video conference, or in person, to address
the following:

-   methodologies for charging costs to the Global Development Plan





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** This portion has been redacted pursuant to a confidential treatment request.


                                      A-7
<PAGE>   31
-   analysis of the consolidated actual Global Development Costs, of the
    determination of the quarterly settlement payments to the Parties and
    supporting detailed documents and reports from the Parties

-   identification and reporting of all significant line item budget variances
    to the OSI-774 Liaison Team

-   proposal for updated rolling development budget and projections to the
    OSI-774 Liaison Team

-   submission of updates of the long range Global Development Plan and rolling
    development budget to the OSI-774 Liaison Team.

A.6.     SHARING OF GLOBAL DEVELOPMENT COSTS - PAYMENTS BETWEEN THE PARTIES

         Global Development Costs will be shared pursuant to Section 2.1 of this
Tripartite Agreement.

         The OSI-774 Liaison Team, will be responsible for, analyzing and
reporting all significant line item budget variances and all overall, total
budget variances to the GDC.

A settlement balancing payment will be invoiced ** to one or both of the other
Parties, no later than ** such that each Party bears its proportionate share of
the Global Development Costs. The OSI-774 Liaison Team will provisionally
approve materially unfavorable deviations from the line item budget, as defined
by the OSI-774 Liaison Team, and subsequently approve the calculation and basis
for invoicing such balancing payments between the Parties. The Parties



-------------------
** This portion has been redacted pursuant to a confidential treatment request.


                                      A-8
<PAGE>   32
shall meet on an annual basis no later than ninety (90) days after the last day
of the year in question and a "true-up" of the calendar year actual Global
Development Costs and its sharing between the Parties shall be presented for
approval by the GDC. Only the GDC may provide final approval for materially
unfavorable line item budget variations and all overall, total budget
variations, chargeable under the Global Development Plan. Corrective settlement
payments may be issued as a consequence of the final decision taken by the GDC.
Such yearly corrective settlement payments will be approved and invoiced as
early as possible, but no later than ninety (90) days after the last day of the
year in question.

         Any payment which is not paid before ** days from receipt of
an invoice will bear interest at a rate equal to the prime rate of interest **.

A.7.     AUDITS AND INTERIM REVIEWS.

         The Parties shall maintain and cause the Third Parties acting for their
account to maintain books of account and complete and accurate records
pertaining to the Global Development Costs in sufficient detail to permit to
confirm the correct calculation of the Global Development Costs.

At the reasonable expense of a Party (the "Requesting Party"), the Requesting
Party or its authorized independent public accountant has the right to engage
the officially appointed worldwide independent public accountant of any other
Party (the "Audited Party") to perform, on behalf of the Requesting Party or its
independent public accountant, an audit, conducted in



-------------------
** This portion has been redacted pursuant to a confidential treatment request.


                                      A-9
<PAGE>   33
accordance with international accounting standards (IAS), of such books and
records of the Audited Party, its Affiliates and sublicensees, that are deemed
necessary by the Audited Party's independent public accountant to report on
Global Development Costs for the period or periods requested by the Requesting
Party and the correctness of any report or payments made under this Agreement.

         Upon timely request and at least thirty (30) working days' prior
written notice from the Requesting Party, such audit shall be conducted as an
additional audit work during the Audited Party's annual audit of the countries
specifically requested by the Requesting Party, during regular business hours in
such a manner as to not unnecessarily interfere with the Audited Party's normal
business activities, **. Such audit shall not be performed more frequently than
once per calendar year nor more frequently than once with respect to records
covering any specific period of time. ** All information, data documents and
abstracts herein referred to shall be used only for the purpose of verifying
Global Development Costs or compliance with this Agreement, shall be treated as
Confidential Information subject to the obligations of this Agreement and need
neither be retained more than one (1) year after completion of an audit hereof,
if an audit has been requested; nor more than ** from the end of the calendar
year to which each shall pertain; nor more than one (1) year after the date of
termination of this Agreement. Audit results shall be shared by the Requesting
Party and the Audited Party. If accounting errors found greater than ** in the
items sampled such that the Audited Party has been overpaid, then the costs of
such



-------------------
** This portion has been redacted pursuant to a confidential treatment request.


                                      A-10
<PAGE>   34
audit shall be borne by the Audited Party, and such Audited Party shall return
to the Requesting Party the amount of money received in error plus interest **

         The failure of a Party to request verification of any calculation of
Global Development Costs during the period when records have to be retained
shall be considered acceptance of the accuracy of such reporting by such Party.

         In the case a Party has overpaid Global Development Costs to the other,
such Party shall be entitled to claim reimbursement of any such amount overpaid
and the other Party shall promptly reimburse the Party having overpaid for any
such amount plus interest **

A.8.     START OF OPERATIONS AND EFFECTIVE ACCOUNTING DATE TERMINATION.
Operation of the Global Development Plan will be deemed to have commenced as of
the Effective Date of the Agreement. Costs and expenses incurred prior to such
date are not chargeable to the Global Development Plan.

         For reporting and accounting purposes with respect to the Global
Development Plan, the effective termination date of the Agreement will be the
nearest month end to which such termination takes place.





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** This portion has been redacted pursuant to a confidential treatment request.


                                      A-11
<PAGE>   35
                                    EXHIBIT B

                                   TRIPARTITE


                     -------------------------------------
                                 OSI/GNE/ROCHE
                                ----------------
                          GLOBAL DEVELOPMENT COMMITTEE
                        -Annual Plan/Dispute Resolution
                        -Budget and Cost Reconciliation
                        -Each company has 2 members
                          -Chairman rotates, OSI first
                     -------------------------------------

----------------------    --------------------------  -----------------------
                              OSI-744 LIASON TEAM
     OSI/GNE                                                   ROCHE
    ---------                                                ---------
  US PROJECT TEAM           (Heads of Project Team          Project Team
                           from OSI, GNE and Roche)
----------------------    --------------------------  -----------------------


                     -------------------------------------
                                      CRO
                                 MANUFACTURING
                                   DATA, ETC.
                     -------------------------------------

<PAGE>   36
                                    GENENTECH



              --------------------------------------------------
                        OSI/GNE JOINT STEERING COMMITTEE
                        --------------------------------
                        US Development/Commercialization
                             3 Senior Managers Each
                                   -Guidance
                        -Annual Plan and Budget Approval
              --------------------------------------------------


                                                               -----------------
                                                                 Joint Finance
                                                                 Sub-Committee
                                                               -----------------

                     -------------------------------------
                                    OSI/GNE
                                   ----------
                                US PROJECT TEAM
                     -------------------------------------


                                                             -------------------
                                                                     CRO
                                                                MANUFACTURING
                                                                  DATA, ETC.
                                                             -------------------

                   --------------------
  GNE               Regulatory Affairs
Clinical              Sub-Committee         R&D             OSI Clinical
  Team             --------------------     Activities           Team



<PAGE>   37
                                      ROCHE



                     -------------------------------------
                                     ROCHE
                                    -------
                                  Project Team
                     -------------------------------------


-------------------      Clinical     Regulatory     Marketing     Manufacturing
       CRO
   MANUFACTURING
     DATA, ETC.
-------------------
<PAGE>   38
                                    EXHIBIT C

                             GLOBAL DEVELOPMENT PLAN

                                       **
















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** This portion has been redacted pursuant to a confidential treatment request.
<PAGE>   39
                                    EXHIBIT D

                     MEMBERS OF GLOBAL DEVELOPMENT COMMITTEE


GENENTECH

Susan Hellmann
Stephen Dilly


OSI

Nicholas Bacopoulos
Paul Nadler


ROCHE

Ed Holdener
To be advised