COLLABORATIVE RESEARCH AND LICENSE AGREEMENT

                                     BETWEEN

                                 COMBICHEM, INC.

                                       AND

                          IMCLONE SYSTEMS INCORPORATED

                                October 10, 1997

<PAGE>

                  COLLABORATIVE RESEARCH AND LICENSE AGREEMENT

     THIS  COLLABORATIVE  RESEARCH AND LICENSE  AGREEMENT (the  "Agreement")  is
entered into and made effective as of October 10, 1997 (the  "Effective  Date"),
by and between  COMBICHEM,  INC., a Delaware  corporation  having its  principal
offices  at 9050  Camino  Santa Fe,  San Diego,  California  ("CombiChem"),  and
IMCLONE  SYSTEMS  INCORPORATED,  a Delaware  corporation  having  its  principal
offices located at 180 Varick Street, 7th Floor, New York, New York ("ImClone").

     WHEREAS, CombiChem has developed and owns certain drug discovery technology
and  intellectual  property  rights,  including but not  necessarily  limited to
chemical  library design  software,  multi-parallel  synthesis and  purification
methods,  chemical  libraries  suitable  for  biological  screening  assays  and
medicinal chemistry (collectively, "CombiChem Technology");

     WHEREAS,  ImClone  desires to  utilize  CombiChem  Technology  for its drug
discovery  activities under ImClone know-how  concerning the  identification and
characterization   of  novel  small  molecule   inhibitors  for  development  as
therapeutics for treatment of human disease in the area of oncology;

     WHEREAS,  the parties wish to  collaborate  in a Research  Program  against
Collaboration Target(s) ("Collaboration");

     WHEREAS, for purposes of the Collaboration,  the Parties intend to focus on
up to *** Collaboration Targets per *** related to ImClone's Areas of Interest;

     NOW, THEREFORE, the Parties agree as follows:

     1. DEFINITIONS

     1.1 "Abandoned Compound" shall have the meaning set forth in Section 3.1.

     1.2 "Abandoned Target" shall have the meaning set forth in Section 3.1.

     1.3 "Active Compound(s)" means a compound (or compounds) which

          (a) (i)  is selected by either  Party under the Research  Program from
                   Collaboration Compounds, or

              (ii) is derived from a Collaboration Compound; and

          (b) shows In Vitro Activity.

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       1
<PAGE>

     1.4   "Additional   Target(s)"   means  a  Target  that  is  added  to  the
Collaboration in accordance with Section 4.2.

     1.5  "Affiliate" of a Party means any  corporation or other business entity
controlled by,  controlling or under common control with,  such Party.  For this
purpose  "control"  shall mean direct or indirect  beneficial  ownership of more
than fifty  percent (50%) of the voting  securities  or income  interest in such
corporation or other business, or if not meeting the preceding requirements, any
company  owned or  controlled  by or owning  or  controlling  such  Party at the
maximum  control or ownership  right permitted in the country where such company
exists.

     1.6 "Areas of Interest" shall include         ***        *** .

     1.7 "Collaboration" has the meaning set forth in the preamble.

     1.8  "Collaboration  Compound(s)" means a compound (or compounds) which (a)
is   synthesized   following  the  Effective   Date  for  screening   against  a
Collaboration Target under the Research Program, (b) is a pre-existing CombiChem
Compound which CombiChem  desires to designate as a Collaboration  Compound,  or
(iii) is a pre-existing ImClone Compound which ImClone desires to designate as a
Collaboration Compound.

     1.9  "Collaboration  Target(s)"  means  either  an  Initial  Target  or  an
Additional Target.

     1.10 "CombiChem  Compound" means a chemical compound that is proprietary to
CombiChem, or whose use or manufacture is proprietary to CombiChem.

     1.11 "CombiChem Technology" has the meaning set forth in the preamble.

     1.12 "Confidential Information" includes, but is not limited to,

          (a) all  information  and materials  received by either Party from the
     other Party pursuant to this Agreement;

          (b) all  information  and  materials  developed  in the  course of the
     Collaboration; and

          (c) the material financial terms of this Agreement.

     1.13 "Development Compound(s)" means a compound ( or compounds) which

          (a) (i) is a Lead  Compound or (ii) is derived  from a Lead  Compound;
     and

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       2
<PAGE>

          (b) are  determined  by  ImClone  to be  appropriate  for  preclinical
     studies for the purpose of IND filing by ImClone.

     1.14 "Due  Diligence"  means the use of the  resources  of  ImClone  or its
licensees  or CombiChem  in a manner  which is  consistent  with the exercise of
prudent scientific and business judgment as applied to other programs of ImClone
or CombiChem, as the case may be, targeting products aimed at markets or patient
groups of similar sizes and of similar scientific and commercial potential. With
respect to any Development Compound,  "Due Diligence" shall also require ImClone
or its licensees to conduct all necessary preclinical studies and to file an IND
for such  Development  Compound  within *** from the date upon which ImClone has
designated such Development Compound from any Lead Compound or its derivatives.

     1.15  "Exclusivity  Period"  means the  Research  Period  plus  twelve (12)
months. .

     1.16 "Field"  means all  therapeutic  indications  of human disease for the
Collaboration Target.

     1.17 "First Commercial Sale" of a Product shall mean the first sale for use
or consumption of such Product in a country after required marketing and pricing
approval has been granted by the governing health  regulatory  authority of such
country.  Sale  to an  Affiliate  or  licensee  shall  not  constitute  a  First
Commercial Sale unless the Affiliate or licensee is the end user of the Product.

     1.18  "FTE"  means  full time  equivalent  with  respect  to  employees  of
CombiChem.

     1.19 "ImClone  Compound"  means a chemical  compound that is proprietary to
ImClone, or whose use or manufacture is proprietary to ImClone.

     1.20 "Inactive  Compound(s)"  means a Collaboration  Compound(s) which does
not have the In Vitro Activity required for an Active Compound.

     1.21 "In Vitro Activity" shall mean the observation of       ***      *** .

     1.22  "Initial  Target"  shall have the  meaning  set forth in Section  4.1
hereof.

     1.23 "Lead Compound(s)" means a compound (or compounds) which

          (a) is  selected  from an  Active  Compound(s)  by the RMC  under  the
     Research Program, or

          (b) is derived from Active Compound(s) and is selected by the RMC.

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       3
<PAGE>

     1.24  "Net  Sales"  means  the  gross  sales  invoiced  by  ImClone  or its
Affiliates or licensees for Products to non-Affiliated Third Parties less actual
deductions  of returns  (including  withdrawals  and  recalls),  rebates  (price
reductions,  including Medicaid and similar types of rebates e.g.  chargebacks),
volume (quantity)  discounts,  discounts  granted at the time of invoicing,  the
cost of transport,  insurance, delivery, sales taxes and other taxes (other than
income  taxes)  directly  linked to and included in the gross sales  amount,  as
computed on a product-by-product basis for the countries concerned,  whereby the
amount of such sales in foreign  currencies  is  converted  into  United  States
dollars at the exchange rate of the last business day for each calendar month as
reported by Citibank, N.A. (New York).

     1.25 "Patent" means,  (a) valid and enforceable  Letters Patent,  including
any extension (including  Supplemental  Protection  Certificate),  registration,
confirmation,   reissue,   continuation,   divisionals,    continuation-in-part,
reexamination  or renewal  thereof,  or (b) pending  applications for any of the
foregoing.

     1.26 "Payments" shall have the meaning set forth in Section 9.3

     1.27  "Party"  means  CombiChem or ImClone,  as the case may be,  including
their respective Affiliates, permitted successors and assigns.

     1.28 "Product(s)" means any product containing a Development  Compound with
such compound as the active ingredient and which is granted regulatory  approval
by the  governing  health  regulatory  authority of the  applicable  country for
marketing in the Field.

     1.29 "Project Team" shall have the meaning set forth in Section 2.1(c).

     1.30 "Research Management  Committee" or" RMC" has the meaning set forth in
Article 6 below.

     1.31 "Research Period" means the initial twenty-four (24) month term of the
Collaboration, which can be extended in accordance with Section 7.1 below.

     1.32  "Research  Plan"  means  the  mutually-agreed  research  plan for the
Collaboration attached hereto as Appendix A.

     1.33  "Research  Program" means the research to be conducted as part of the
Collaboration  under the Research Plan, and shall include,  without  limitation,
the activities and items set forth in Sections 2.1 and 2.2 of this Agreement.

     1.34 "Returned Compound" shall have the meaning set forth in Section 9.2.

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       4
<PAGE>

     1.35 "Royalty Term" means, in the case of any Product, in any country,  the
period of time commencing on the First Commercial Sale and ending upon the later
of (a)  fifteen  (15)  years  from  the date of  First  Commercial  Sale in such
country;  or (b) the expiration of the last-to-expire  Patent resulting from the
Research  Program  filed in the Field with claims  covering  that Product in the
relevant country.

     1.36 "Target" means a biomolecular entity that a small molecule is screened
against in order to determine whether the small molecule  demonstrates  relevant
activity.

     1.37 "Territory" means the entire world.

     1.38 "Third Party" means an entity other than CombiChem or ImClone or their
respective Affiliates.

     1.39  "Universal  Informer  Library"  shall  mean  CombiChem's  proprietary
Universal Informer Library of compounds.

     2. RESEARCH COLLABORATION

     2.1 CombiChem Responsibilities.  CombiChem shall with Due Diligence conduct
the following activities under the Research Program in accordance with the terms
of this Agreement and as more fully described in the Research Plan:

          (a)  During the Research  Period,  CombiChem shall (i) review data and
               information  regarding  the  Collaboration  Targets  provided  by
               ImClone;  (ii) based on such data and  information  and using the
               CombiChem Technology,  design informative compound libraries; and
               (iii) supply all lead  chemistries  and  synthesize  compounds as
               provided in Section 5.3 below.

          (b)  During the Research Period, CombiChem shall keep ImClone informed
               of its activities performed in connection with the Collaboration,
               including,  without  limitation,  providing ImClone with data and
               information  regarding   Collaboration  Compounds  prior  to  the
               meetings of the Research Management Committee.

          (c)  Subject to Article 4 and at all times during the Research Period,
               CombiChem  shall  dedicate  a  project  team  of  five  (5)  FTEs
               comprised of synthetic and analytical chemists,  compound control
               scientists, and a computational scientist (the "Project Team") to
               conduct   all  of  its   activities   in   connection   with  the
               Collaboration;  provided,  however,  that the RMC may at any time
               during the  Research  Period  substitute  employees  for the FTEs
               described above; provided, further, that 

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       5
<PAGE>

               ImClone may request  that  CombiChem  expand its Project  Team by
               adding  additional FTEs to work on the  Collaboration at the rate
               and in the manner specified in Section 8.2(b).

     2.2 ImClone  Responsibilities.  ImClone  shall with Due  Diligence  provide
CombiChem with the following  resources under the Research Program as more fully
described in the Research Plan:

          (a)  ImClone  shall  provide  CombiChem  with  support and  assistance
               useful or  necessary  for the  conduct of the  Research  Program,
               including providing data and information  (including leads and/or
               screening hits to the extent available) relating to Collaboration
               Targets,   certain  chemistries  useful  in  compound  synthesis,
               information concerning assay methods and screening data.

          (b)  During the Research Period,  ImClone shall provide CombiChem with
               data and information  regarding  Collaboration  Compounds and the
               Collaboration  Target  assays  developed  by  ImClone  under  the
               Research Program prior to the meetings of the Research Management
               Committee.

          (c)  During the  Exclusivity  Period and with Due  Diligence,  ImClone
               shall  screen  Collaboration  Compounds  for In Vitro and,  where
               appropriate, in vivo activity against the Collaboration Target.

          (d)  During the  Exclusivity  Period and with Due  Diligence,  ImClone
               shall (i) screen  Lead  Compounds,  (ii)  endeavor  to  determine
               Development Compounds, and (iii) develop Products.

     2.3 Research Plan. The Parties hereby agree that the Research Program shall
be carried out in accordance  with the Research Plan which is attached hereto as
Appendix A. At the direction of the RMC, the Research  Program shall involve the
use of CombiChem's  Universal Informer Library in order to initiate  CombiChem's
discovery  process with the objective of identifying Lead Compounds with respect
to a specific  Collaboration  Target.  The Research  Management  Committee shall
review  the  Research  Plan on an  ongoing  basis  and may make  changes  to the
Research  Plan so long as such changes are mutually  agreed to by CombiChem  and
ImClone.

     2.4 Annual Reports. Following the first IND filing through First Commercial
Sale,  ImClone  shall  provide  CombiChem  with  an  annual  report  summarizing
ImClone's activities in developing Development Compounds.

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       6
<PAGE>

     2.5 Third Party  Licenses.  Each Party shall be solely  responsible for any
Third  Party  license  fees  required  to  perform  its  obligations  under this
Agreement  subject to Section  8.4. Any  agreements  between a Party and a Third
Party shall in all material respects permit performance under this Agreement.

     3. EXCLUSIVITY

     3.1 Collaboration Target Exclusivity. So long as ImClone or its licensee is
proceeding  with Due  Diligence,  CombiChem  shall  not work on a  Collaboration
Target with any Third  Parties.  In the event that ImClone or its licensee fails
to exercise Due  Diligence  with respect to, or notifies  CombiChem  that it has
abandoned  work on, any  Collaboration  Target (an  "Abandoned  Target") and any
Collaboration  Compound,  other than an ImClone Compound which is subject to the
rights of a Third Party  licensor,  associated  with such  Collaboration  Target
(together with all  derivatives of such  Collaboration  Compound,  an "Abandoned
Compound"),  then,  (a)  such  Abandoned  Target  shall  not be  subject  to any
provision  hereunder,  and (b) such  Abandoned  Compound  shall be  available to
CombiChem for any purpose thereafter.

     3.2 Active Compounds.

     (a) Following the  designation of any  Collaboration  Compound as an Active
Compound,  such Active Compound shall be exclusively available to ImClone during
the Research  Period.  Following the expiration of the Research  Period,  Active
Compounds  with respect to which  ImClone  fails to proceed  with Due  Diligence
shall be deemed to be Inactive Compounds for all purposes  hereunder;  provided,
that any Active Compound which is the subject of claim(s) under a pending Patent
shall continue to be treated as an Active Compound during the Exclusivity Period
so long as ImClone  exercises  Due Diligence  with respect to any  Collaboration
Compound.

     (b) Prior to the  existence of Patent(s)  in  accordance  with Section 5.2,
ImClone shall have exclusive  rights in all  intellectual  property  relating to
Active  Compounds,  their  use,  and  method of  manufacture  so long as ImClone
continues to show Due Diligence under this Agreement;  provided,  however,  that
ImClone  acknowledges and agrees that CombiChem  reserves the right to assign or
grant exclusive rights,  including rights to Active Compounds,  to a third party
collaborator who first  identifies a novel compound,  a novel use of a compound,
or a novel  method of  manufacturing  a  compound,  to the extent  CombiChem  is
obligated to do so under its existing  contractual  obligations.  Upon notice by
ImClone that it intends to file a Patent  application with respect to any Active
Compound,  Lead  Compound,  Development  Compound  or Product,  CombiChem  shall
promptly inform ImClone  whether  CombiChem has the power to grant the exclusive
rights in  accordance  with this Section 3.2 and the  assignments  in accordance
with Section 5.2; provided,  however, that under no circumstances CombiChem will
grant  assurances  to  ImClone  to the effect  that any  Active  Compound,  Lead
Compound, Development Compound or Product is not covered under the patent claims
of  Third  Parties   wherein  such  claims  are  not  the  direct  result  of  a
collaboration between the Third Party and CombiChem.

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       7
<PAGE>

     3.3 Inactive Compounds/Returned Compounds. Subject to Section 9.4, Inactive
Compounds  and  Returned  Compounds  shall be  available to both Parties for any
purpose.

     4. TARGETS

     4.1 Initial Targets.  During the Research Period,  ImClone may designate up
to ***  Collaboration  Targets per *** under the  Research  Program.  During the
initial *** *** of the  Research  Program,  subject to the  Research  Plan it is
anticipated that the Collaboration shall initially focus on up to *** Targets as
follows:    ****       ***       (collectively,  the  "Initial  Targets").  With
respect to Collaboration  Targets, the RMC will determine whether to continue to
pursue work against  designated  Collaboration  Targets and will  prioritize the
activities of the Project Team against such Collaboration  Targets. In the event
that the results of the initial screening  activities of ImClone with respect to
the Initial Targets specified in Section 4.1      ***       *** 
which shall  determine  whether such Targets are  suitable  for  designation  as
Additional Targets.  Subject to the dispute resolution mechanism provided for in
Article  6,  ImClone  shall have the right to make a final  determination  as to
whether to  continue  or pursue work  against  any  Collaboration  Target if the
respective  Chief  Executive  Officers  of  CombiChem  and ImClone are unable to
resolve  any  dispute  concerning  the same.  In  addition,  ImClone's  right to
designate or substitute a Target  (including those Additional  Targets set forth
in Section 4.2) relating to ImClone's  Areas of Interest shall be subject to the
written notice and approval requirements specified in Section 4.2(b).

     4.2 Additional Targets.

     (a)  Within  ninety  (90)  days  prior to the  commencement  of the  second
12-month period of the Research  Program,  ImClone may add up to *** relating to
ImClone's  Areas of Interest to the  Collaboration  by  notifying  CombiChem  in
writing that it wishes to designate such Target(s) as Additional  Target(s);  it
being understood that the Project Team shall be obligated to simultaneously work
on no more than *** Collaboration Targets as directed by the RMC.

     (b) If CombiChem has already committed to working on a proposed  Additional
Target  or has  delivered  a term  sheet  to any  Third  Party  and  remains  in
discussions to enter into a binding agreement with such Third Party with respect
to the  proposed  Target at the time of  notification,  CombiChem  shall  inform
ImClone that such proposed  Additional Target is not available.  Otherwise,  the
RMC shall establish the specific scientific  achievements (to be mutually agreed
between  CombiChem and ImClone) for such Target and the same shall be designated
as an  Additional  Target  for  the  Collaboration  and  subject  to  the  terms
(including the commercial terms) of this Agreement.

     4.3 Expansion of Project Team.  Notwithstanding  the provisions of Sections
4.1 and 4.2,  ImClone may request that CombiChem  expand its Project Team during
the Research Period 

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       8
<PAGE>

in order to accelerate  work on  Collaboration  Targets and/or to add additional
Target(s).  In such event,  the RMC shall promptly  confer as to the appropriate
number of FTEs to be added to  Project  Team to work on the  Collaboration  at a
cost to ImClone as specified in Section 2.1(c).

     5. COLLABORATION COMPOUNDS

     5.1   Pre-Existing   Compounds.   ImClone  shall  have  no  rights  to  any
pre-existing  CombiChem Compound unless and until such compound is designated as
a Collaboration  Compound by CombiChem.  Additionally,  CombiChem may decline to
synthesize a  particular  compound or library of compounds by reason of existing
Patents  or  contractual  obligations.  CombiChem  shall  have no  rights to any
pre-existing ImClone Compound which is not utilized in the Research Program.

     5.2 Intellectual Property Rights; Assignment to ImClone. Subject to Section
3.2(b)  above,  ImClone  shall have the right and  responsibility  at  ImClone's
expense to file,  maintain and prosecute  Patents relating to Active  Compounds,
Lead Compounds, Development Compounds and Products, their use, and their methods
of  manufacture.  At ImClone's  request,  CombiChem  shall assign all its right,
title and  interest  in such  Patents to ImClone.  If ImClone  fails to so file,
maintain or  prosecute  such Patent,  CombiChem  shall have the right to request
ImClone to do so. If ImClone  elects not to file,  maintain  or  prosecute  such
Patent, CombiChem shall have the right to take over such filing,  maintenance or
prosecution  of such Patent,  at its sole expense,  and ImClone shall assign all
intellectual property rights it may have in the Active Compound,  Lead Compound,
Development Compound or Product to CombiChem.

     5.3 Supply of Collaboration Compounds. Aliquots of         ***       of any
Collaboration  Compound that has been  synthesized will be prepared and given to
ImClone.  CombiChem  shall  replenish  that  amount  upon  ImClone's  reasonable
request.  CombiChem shall maintain aliquots of any  Collaboration  Compound that
has been  synthesized by CombiChem.  CombiChem  shall also provide  ImClone with
additional requirements of samples at CombiChem's cost.

                        6. RESEARCH MANAGEMENT COMMITTEE

     The design,  review and conduct of the Research Program will be coordinated
by  the  Research  Management   Committee,   which  will  meet  regularly  on  a
mutually-agreeable schedule. The Research Management Committee may establish and
amend or revise  the  Research  Plan as  necessary  to  reflect  the  scientific
progress and work performed  under the Research  Program,  such amendments to be
mutually agreed to by ImClone and CombiChem.  The Research Management  Committee
will consist of an equal number of members from ImClone and  CombiChem  and will
include  appropriate  representatives  from  ImClone and  CombiChem  as mutually
agreed. The co-chairs of the Research Management Committee will initially be the
Vice  President,  Chemistry of CombiChem and the Vice  President for Research of
ImClone and  subsequently  may change as  mutually-agreed  upon by the  Parties.
Decisions of the  Research  Management  Committee  shall be by  

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       9
<PAGE>

consensus. If a decision is not reached by the RMC with respect to management of
the Research Program,  the dispute will be referred to the co-chairs of the RMC.
If the co-chairs of the RMC are unable to resolve the dispute,  the dispute will
be referred to the respective Chief Executive Officers of CombiChem and ImClone.

     7. RESEARCH PERIOD; TERMINATION OF RESEARCH PROGRAM

     7.1 Research Period: Option to Extend the Research Period. The initial term
of the  Collaboration  shall be the Research  Period,  subject to extension upon
mutual agreement.  To extend the Research Period,  ImClone must notify CombiChem
no later than ninety (90) days prior to the then-current expiration date and the
Parties  shall  negotiate  in good  faith the terms and  conditions  of any such
extension.

     7.2 Termination of Research Program.

     (a) The  Research  Program may be  terminated  by a Party for the  material
breach by the other Party of  obligations  under the Research  Program by giving
the breaching party notice of the breach and of the intent of the  non-breaching
Party to terminate the Research Program unless the breach is cured within ninety
(90) days of notification.  The  non-breaching  Party may terminate the Research
Program  following such ninety (90) day period by providing the breaching  party
with  ninety  (90) days'  prior  written  notice  that the  Research  Program is
terminated,  and the  Research  Program  shall  be  terminated  on the  90th day
following such date.

     (b) Within thirty (30) days prior to the one (1) year  anniversary  of this
Agreement,  ImClone and CombiChem  senior and  scientific  management  personnel
shall  meet to review  the  status of the  Collaboration.  If,  based  upon such
review,  the status of the  Collaboration  is satisfactory  to ImClone,  ImClone
shall make the Second Research Payment  described in Section 8.2 to CombiChem on
or before the one (1) year  anniversary of this  Agreement;  provided,  however,
that ImClone may, in its discretion,  make such Second  Research  Payment at any
time prior to the date which is the one (1) year  anniversary of this Agreement.
If  however,  based  upon  such  review,  the  status  of the  Collaboration  is
unsatisfactory  to  ImClone,  ImClone  may  terminate  the  Research  Program by
providing  90-days' prior written notice to CombiChem that the Research  Program
shall be  terminated.  Upon receipt of such notice by  CombiChem,  ImClone shall
have no further  obligation to make the Second Research Payment to CombiChem (if
such payment has not already been made to CombiChem),  and the Research  Program
shall be terminated on the 90th day following such date.

     (c) CombiChem  shall,  within thirty (30) days following the effective date
of termination under Section 7.2(a) or 7.2(b),  pay to ImClone such amount as is
calculated  by taking                       *** 
                         *** 
*** shall be based  upon              ***                    . Any amount due by
CombiChem  under  this  Section  7.2(c)  may  be in  the  form,  at  CombiChem's
discretion, of

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       10
<PAGE>

                    *** 
                    *** 
          *** . 

     8. CONSIDERATION

     8.1 Equity  Purchase.  Upon  execution  of this  Agreement,  ImClone  shall
purchase  1,000,000  shares (on a pre-split  basis and subject to adjustment) of
Common Stock of CombiChem at a per share purchase price equal to $2.00 per share
for an  aggregate  purchase  price of U.S. $2 million,  pursuant to the terms of
that certain Common Stock Purchase Agreement, dated as of the Effective Date, by
and  between  CombiChem  and ImClone  (together  with all  ancillary  agreements
thereto, the "Stock Purchase Agreement").  In the event that CombiChem closes an
initial  public  offering of its common  stock at a sales price per share to the
public  (the "IPO  Price")  which is less than  $2.50 per share (on a  pre-split
basis), then, upon the closing of such initial public offering,  CombiChem shall
issue to ImClone,  without further  consideration  other than the purchase price
paid by ImClone pursuant to the Stock Purchase Agreement, such additional number
of shares of CombiChem common stock equal to:

                             2,000,000
                             -------------- -1,000,000
                             Adjusted Price

wherein the "Adjusted Price" = the IPO Price X .80 if the IPO Price is less than
$2.50 per share.  All shares of CombiChem  common stock issued  pursuant to this
Section  8.1 shall be deemed to be  "Shares"  within  the  meaning  of the Stock
Purchase Agreement.

     8.2 Program Funding.

     (a) ImClone shall support  CombiChem's  efforts in conducting  the Research
Program by making a payment upon the  execution of this  Agreement in the sum of
U.S. $0.5 million as direct research support..  In addition,  subject to Section
7.2(b),  ImClone  shall  make a  payment  (the  "Second  Research  Payment")  to
CombiChem  prior to October 10, 1998 in the amount of U.S.  $0.5  million in the
form either,  at ImClone's  discretion,  of (i) cash, or (ii) stock equal to the
quotient  obtained by dividing (i) U.S.  $0.5 million by (ii) the average of the
last reported  sales price of the ImClone common stock as quoted on the National
Market  System of the National  Association  of  Securities  Dealer's  Automated
Quotation System during the thirty (30)  consecutive  trading days ending on the
day prior to delivery of such shares (the "ImClone Price Per Share").

     (b) In the event that the  Project  Team is  expanded  in  accordance  with
Section 4.3, ImClone shall make payments, in cash, to CombiChem,  at a per annum
rate of U.S.          ***       payable  quarterly  in advance of the work to be
performed by such additional FTE(s).

     (c) Any shares of  ImClone  common  stock  issued to  CombiChem  under this
Section 8.2 shall be restricted  securities under the Securities Act of 1933, as
amended,  and shall 

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       11
<PAGE>

be issued pursuant to a stock issuance  agreement  between ImClone and CombiChem
which shall contain provisions for representations and warranties equivalent to,
and registration rights and indemnification (and such other relevant provisions)
with respect to the shares of ImClone  common stock  issued  thereunder  no less
favorable than, those contained in the Stock Purchase Agreement.


     8.3  Milestone  Payments.  Within  thirty (30) days of the  occurrence of a
development  milestone  triggered  by the  activities  of  ImClone  as  shown on
Appendix B, ImClone shall pay CombiChem  the related  milestone  payment in U.S.
dollars as set forth on Appendix  B.  Alternatively,  in the event that  ImClone
shall outlicense the Patents  covering any Product,  CombiChem shall be entitled
to the  payments  set forth in Section 9.3 in lieu of any  payments  pursuant to
this Section 8.3.

     8.4 Royalties.

     (a) Direct Sales by ImClone

          (i) Subject to Section 8.4(c),  during the Royalty Term,  ImClone will
     pay  CombiChem a running  royalty of *** of Net Sales of  Products  sold by
     ImClone or its Affiliates in all countries in the  Territory.  Each payment
     of royalties  shall be  accompanied by a report of Net Sales of Products in
     sufficient  detail to permit  confirmation  of the  accuracy of the royalty
     payment made.

          (ii) The royalties owed under Section  8.4(a)(i)  shall not be reduced
     in accordance  with Sections  8.4(c)(i)  through  8.4(c)(iii)  in an amount
     which  results in a royalty  payable to  CombiChem  of less than *** of Net
     Sales for Products sold directly by ImClone or its Affiliate.

     (b) Sales by ImClone's Licensees

          In  the  event  that  ImClone   outlicenses  Active  Compounds,   Lead
     Compounds,  Development  Compounds  and  resulting  Products  are  sold  by
     ImClone's  licensees  in any country in the  Territory,  ImClone's  royalty
     payable to CombiChem shall be as follows: 



ImClone Royalty from Outlicensing   CombiChem Royalty due to Outlicensing  
---------------------------------   -------------------------------------  

Greater than ***                   (1) *** of ImClone royalty,  but no greater
                                       than ***

                                   (2) Subject  to  reduction  as  outlined in
                                       Sections  8(c)(i)  through   8(c)(iii),  
                                       but  such  reductions  shall not reduce
                                       CombiChems royalty  below *** except as
                                       otherwise provide in Section 8.4(c)(iii).

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       12
<PAGE>

Less than or equal to ***          (1) ***  of ImClone royalty  and  not subject
                                       to  reduction  as  outlined  in  Sections
                                       8(c)(i) and and 8(c)(ii).  

     (c) Royalty Reductions

     (i) In any country in which  Patents do not include a valid  issued  patent
covering  a Product  sold by  ImClone or its  licensee,  and/or  where a generic
equivalent  has been  approved for sale and is being sold in such  country,  the
royalty  provided for in Section  8.4(a)(i) and in Section 8.4(b),  as indicated
therein, shall be reduced by *** .

     (ii) In any country in which ImClone pays a Third Party royalty for patents
and  related  technology  in order to sell a Product,  *** of such  Third  Party
royalty  shall be *** the  royalty  payment  owed by  ImClone  to  CombiChem  in
accordance  with Section  8.4(a)(i) and Section  8.4(b),  as indicated  therein.
During  the  Research  Period,  the RMC will make the  determination  whether to
include any Third Party  royalty-bearing  patents and related  technology in the
Collaboration. After the Research Period, ImClone shall, in its discretion, make
the  determination  whether to enter into any  agreements  with respect to Third
Party  royalty-bearing  patents  and  related  technology  for  purposes of this
Agreement.

     (iii) In any country in which CombiChem receives any Additional Payments in
respect of payments  received by ImClone which are treated as an advance against
royalties due ImClone from its licensee,  such Additional  Payments shall be ***
the  royalties  provided  for in  Section  8.4(b)  that are  derived  from  such
licensee.

     8.5 Manner and Place of Payment. Royalty payments and reports for Net Sales
of Products  shall be  calculated  in local  currencies  and  reported  for each
calendar  quarter.  All royalty payments owed under this Agreement shall be made
by wire transfer to the bank account to be designated by CombiChem within thirty
(30) days following the end of each such calendar quarter.

     8.6 Records and Audit.  During the term of this  Agreement and for a period
of five (5) years  thereafter,  ImClone shall keep complete and accurate records
pertaining to the sale or other  disposition of Products in sufficient detail to
permit  CombiChem  to  confirm  the  accuracy  of all  payments  due  hereunder.
CombiChem  shall  have  the  right  to cause  an  independent  certified  public
accounting  firm  reasonably  acceptable  to ImClone  to audit  such  records to
confirm  ImClone's Net Sales for the preceding  year. Any  information  obtained
during such audit shall be treated as Confidential Information.  Such audits may
be  exercised  during  normal  business  hours of ImClone no more than once each
year.  CombiChem  shall  bear the full  cost of such  audit  unless  such  audit
discloses a variance of more than five percent (5%) in ImClone's  favor from the
amount of the Net Sales  reported by ImClone for such  audited  period.  In such
case, ImClone shall bear the fill cost of such audit.

     8.7 Taxes.  All income and other taxes  levied on account of the  royalties
and other payments  accruing to CombiChem  under this Agreement shall be paid by
CombiChem,  

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       13
<PAGE>

including  taxes levied thereon as income to CombiChem.  If provision is made in
law or regulation for  withholding,  such tax shall be deducted from the royalty
or other payment made by ImClone to the proper taxing authority and a receipt of
payment of the tax secured  and  promptly  delivered  to  CombiChem.  Each Party
agrees to assist the other Party in claiming  exemption from such  deductions or
withholdings  under any double taxation or similar agreement or treaty from time
to tune in force.

     9. LICENSE GRANTS; OUTLICENSE

     9.1 CombiChem License Grant to ImClone. Subject to the terms and conditions
of this  Agreement,  CombiChem  hereby grants to ImClone an exclusive  worldwide
license,  with the right to sublicense,  to use such CombiChem  Technology as is
necessary  to make,  have  made,  use,  have  used,  sell,  have sold and import
Collaboration Compounds or Products in the Territory.  Such license shall remain
exclusive in relation to each  Collaboration  Compound and/or Product so long as
ImClone  or  its   licensee   continues  to  develop  and   commercialize   such
Collaboration  Compound and/or Product  containing such  Collaboration  Compound
against a Collaboration Target with Due Diligence.

     9.2 ImClone License Grant to CombiChem. Subject to the terms and conditions
of this  Agreement  and  following  the  failure of ImClone or its  licensee  to
develop and  commercialize  with Due  Diligence a Lead  Compound,  a Development
Compound or Product,  as the case may be,  (collectively,  and together with all
Abandoned Compounds,  "Returned Compound"),  ImClone shall grant to CombiChem an
exclusive  license  (exclusive even as to ImClone and its Affiliates),  with the
right to  sublicense,  under  those  ImClone  Patents  and  know-how  which  are
resulting  from the  Research  Program and related  exclusively  to the Returned
Compound to make,  have made,  use, have used,  sell,  have sold and import such
Returned Compound in the Territory.

     9.3  ImClone  Outlicense.  ImClone  shall  have a right to  outlicense  the
Patents  covering the Product to a Third Party subject to  CombiChem's  right to
receive (a) royalties as provided in Section 8.4(b), and (b) additional payments
("Additional  Payments")  such that  CombiChem has received,  as of each Payment
Date, the greater of (i) the cumulative amount due CombiChem by ImClone upon the
attainment of the milestones set forth in Appendix B by ImClone' s licensee,  or
(ii) the cumulative amount equal to *** of the
                         ***
                         ***
                         ***
                         ***

          ***       but excluding, to the extent reasonable and customary, all 
                ***
                     *** (collectively, the royalties described in clause (a and
the payments described in clause (b) of this sentence,  the "Payments") received
by ImClone from such Third Party in connection  with such  license.  The royalty
Payments  described in clause (a) of the preceding sentence shall be remitted to
CombiChem within thirty (30) days after receipt by ImClone 

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       14
<PAGE>

of such Payments from its licensee.  The Additional Payments described in clause
(b) of the preceding sentence shall be paid to CombiChem within thirty (30) days
following  each date (a "Payment  Date") upon which any milestone  designated in
Appendix B is achieved  and/or ImClone  receives a payment (as described  above)
from its  licensee.  As an express  condition of any such  outlicense,  any such
licensee shall be required to agree in writing to be bound by royalty  reporting
and recordkeeping and inspection  provisions  consistent with those contained in
this Agreement. In addition, CombiChem shall have the right to receive all audit
reports  relating  to sales of  Products of  ImClone's  licensees,  and to cause
ImClone or its successor to have an independent certified public accounting firm
audit such  licensees  records on the same terms as those  specified  in Section
8.6. All payments shall be made by wire transfer to such bank account designated
by CombiChem.  Failure of such licensee to make any milestone or royalty payment
in respect of such Product shall not relieve  ImClone of its obligations to make
royalty and milestone payments to CombiChem hereunder.

     9.4 Rights to Inactive  Compounds/Returned  Compounds. No provision of this
Agreement  shall prevent either Party from making,  having made,  using,  having
used, selling, having sold, or importing Inactive Compounds, products containing
Inactive Compounds, Returned Compounds or products containing Returned Compounds
or screening  Inactive Compounds and Returned Compounds against any target other
than the  Collaboration  Targets.  In the event that either ImClone or CombiChem
(the  "Contracting  Party")  shall enter into a binding  agreement  with a Third
Party to  develop,  market  and/or  sell any  product  containing  any  Inactive
Compound  or  Returned   Compound  as  an  active  ingredient  (a  "Third  Party
Transaction"), then the other Party hereto (the "Other Party") shall be entitled
to *** of *** by the Contracting  Party from such Third Party in respect of such
Third Party  Transactions.  All such payments  shall be sent by wire transfer to
such bank account  designated  by the Other Party within  thirty (30) days after
the  Contracting  Party's  receipt of such  payments and shall be subject to the
recording and auditing provisions of Section 8.6.

     9.5  Miscellaneous  License.  In  addition to any other  rights  granted by
either Party in  accordance  with this Article 9, each Party grants to the other
party a non-exclusive license without the right to grant sublicenses,  under any
intellectual  property rights the granting Party has the power to grant in order
for the other Party to carry out its rights and obligations under this Agreement
including,  but not necessarily  limited to, conducting the Research Program and
manufacturing, developing, selling and importing Products.

     10. TERM AND TERMINATION

     10.1 Term.  The term of this  Agreement  shall  commence upon the Effective
Date of this  Agreement,  and shall expire on the expiration of the last royalty
obligation under this Agreement, except as provided hereunder.

     10.2 Termination by ImClone or CombiChem. Subject to Section 7.2, if either
Party materially  breaches this Agreement and fails to remedy that breach within
ninety (90) days of receiving  written notice  thereof from the other Party,  or
enters into any  arrangement  of  composition  

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       15
<PAGE>

with  its   creditors  or  goes  into   liquidation,   insolvency,   bankruptcy,
receivership or reorganization proceedings,  whether voluntarily or compulsorily
which is not dismissed  within ninety (90) days, then the other Party may at any
time, by notice in writing or by telefax, terminate this Agreement.

     10.3 After Termination.

     (a) Upon any  termination of the Research  Program under Section 7.2(a) due
to a material breach of this Agreement by ImClone,  ImClone's rights pursuant to
Sections 3.1, 3.2, 5.3, 9.1, 9.3 and 9.5 shall immediately cease, and all rights
granted  hereunder with respect to Targets and Collaboration  Compounds,  Active
Compounds, Lead Compounds,  Development Compounds, or Products shall immediately
revert to CombiChem  without  further  obligation to ImClone.  ImClone's  rights
pursuant  to Section  5.2 and 9.3 above that  accrue  prior to such  termination
shall be retained by ImClone.  ImClone  may make,  use,  sell and import  Active
Compounds,  Lead  Compounds,  Development  Compounds  or Products  under  rights
retained  by  ImClone  pursuant  to this  Section  10.3(a)  so  long as  ImClone
continues to satisfy all of its royalty,  milestone,  and Payment obligations in
accordance with Sections 8.3, 8.4, 9.3 and 9.4.

     (b) Upon any  termination of the Research  Program under Section 7.2(a) due
to  a  material  breach  of  this  Agreement  by  CombiChem  with  respect  to a
Collaboration Compound, Active Compound, Lead Compound,  Development Compound or
Product,  all of ImClone's  rights pursuant to Sections 3.1, 3.2, 5.2, 5.3, 9.1,
9.3 and 9.5 shall be retained by ImClone.  ImClone may make, use, sell or import
Active  Compounds,  Lead  Compounds,  Development  Compounds  and Products  with
respect to which  ImClone is not in material  breach  under  rights  retained by
ImClone pursuant to this Section 10.3(b) so long as ImClone continues to satisfy
all of its  royalty,  milestone,  and Payment  obligations  in  accordance  with
Sections  8.3,  8.4, 9.3 and 9.4,  except that ImClone  shall not be required to
satisfy such  obligations  with respect to any  Collaboration  Compound,  Active
Compound,  Lead Compound,  Development Compound or Product with respect to which
CombiChem is in material breach.

     (c) If ImClone  materially  breaches this Agreement  following the Research
Period with respect to an Active Compound,  Lead Compound,  Development Compound
or Product for any reason including,  but not limited to, failing to satisfy its
royalty,  milestone and Payment  obligations  pursuant to Sections 8.3, 8.4, 9.3
and 9.4,  ImClone shall not make,  use, sell or import  Active  Compounds,  Lead
Compounds, Development Compounds or Products with respect to which ImClone is in
material  breach.  ImClone shall retain the right to make,  use, sell and import
Active Compounds, Lead Compounds, Development Compounds or Products with respect
to which  ImClone  is not in  material  breach so long as ImClone  continues  to
satisfy all of its royalty,  milestone,  and Payment  obligations  in accordance
with Sections 8.3, 8.4, 9.3 and 9.4.

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       16
<PAGE>

     (d) If CombiChem  materially breaches this Agreement following the Research
Period for any reason  including,  but not  limited  to,  failing to satisfy its
confidentiality and warranty obligations under Articles 11 and 19, ImClone shall
have the right to make,  use, sell or import Active  Compounds,  Lead Compounds,
Development  Compounds  and  Products  with  respect to which  ImClone is not in
material  breach so long as ImClone  continues  to satisfy  all of its  royalty,
milestone, and Payment obligations in accordance with Sections 8.3, 8.4, 9.3 and
9.4.

     (e) Upon any  expiration or earlier  termination  of this Agreement for any
reason,  ImClone  shall not be  entitled to any refund of any  payments  made to
CombiChem hereunder except as provided in Section 7.2(c).

     10.4 Effect of Termination on Licensees. In the event of any termination of
this Agreement pursuant to this Article 10 where such termination shall not have
been caused by the action or inaction on the part of any respective  licensee of
ImClone or CombiChem, or by any breach by such licensee of its obligations under
its licensee from ImClone or CombiChem, as appropriate, such termination of this
Agreement  shall  be  without  prejudice  to the  rights  of each  non-breaching
licensee and such licensee shall be deemed to be a direct licensee hereunder.

     11. CONFIDENTIAL INFORMATION

     11.1  Nondisclosure.  During the term of the Collaboration and for a period
of five (5) years  after  termination  thereof,  each  Party will  maintain  all
Confidential  Information  in trust and  confidence  and will not  disclose  any
Confidential  Information  to any third  party  for any  purpose  except  (i) as
expressly  authorized  by this  Agreement,  or (ii) as  required by law or court
order, or (iii) to its consultants, subcontractors or agents who need to know to
accomplish the purposes of this Agreement.  Each Party may use such Confidential
Information  only to the extent  required  to  accomplish  the  purposes of this
Agreement.  Each Party will use at least the same standard of care as it uses to
protect  proprietary or  confidential  information of its own to ensure that its
Affiliates,  employees,  agents,  consultants and other  representatives  do not
disclose or make any  unauthorized  use of the  Confidential  Information.  Each
Party will promptly notify the other upon discovery of any  unauthorized  use or
disclosure  of  the  Confidential   Information.   Confidential  Information  is
understood to include,  but not  necessarily to be limited to, the structures of
chemical compounds and the identification of chemical compounds as Collaboration
Compounds,  Active Compounds,  Inactive Compounds,  Lead Compounds,  Development
Compounds, or Products.

     11.2 Exceptions. Confidential Information shall not include any information
which the  receiving  Party  can prove by  competent  evidence:  (a) is now,  or
hereafter becomes, through no act or failure to act on the part of the receiving
Party, generally known or available;  (b) is known by the receiving Party at the
time  of  receiving  such  information,  as  evidenced  by its  records;  (c) is
hereafter  disclosed to the  receiving  Party by a Third  Party,  as a matter of
right and without restriction on disclosure;  (d) is independently  developed by
the  receiving  Party  without  the  aid,  application  or use  of  Confidential
Information;  (e) is the subject of a written permission to disclose provided by
the disclosing  Party; or (f) is necessary to obtain  regulatory  approval for a
Product, or
 

                                       17
<PAGE>

patent protection with respect to Active Compounds, Lead Compounds,  Development
Compounds, or Products, and the uses and methods of manufacturing thereof.

     12. PUBLICATIONS AND PUBLIC STATEMENTS

     12.1   Publications.   Each  Party  shall  be   permitted  to  publish  any
information,  except Confidential Information,  relating to the Research Program
as long as the Party has the prior written  permission of the other Party.  Such
permission  shall be  approved or  disapproved  within  twenty-one  (21) days of
written  request  for  permission.  Such  permission  shall not be  unreasonably
withheld.

     12.2 Public Statements. Neither Party shall use the name of the other Party
in any public  statement,  prospectus,  annual  report or press release or other
public  communication  (collectively  "Public  Statements")  without  the  prior
written approval of the other Party,  which may not be unreasonably  withheld or
delayed;  provided,  however,  that both Parties shall endeavor in good faith to
give the other  Party a minimum of two (2)  business  days to review such Public
Statements; provided, further, that, upon approval of any such Public Statement,
both Parties may  disclose to third  parties the  information  contained in such
Public  Statement  without the  further  approval  of the other;  and  provided,
further,  that if a Party does not approve such Public  Statement,  either Party
may still use the name of the other  Party in any Public  Statement  without the
prior written  approval of the other Party,  if such Party is advised by counsel
that such disclosure is required to comply with applicable law.

     13. INDEMNIFICATION

     13.1 EACH PARTY HEREBY AGREES TO SAVE,  DEFEND AND HOLD THE OTHER PARTY AND
ITS OFFICERS,  DIRECTORS,  EMPLOYEES,  CONSULTANTS  AND AGENTS HARMLESS FROM AND
AGAINST ANY AND ALL SUITS, CLAIMS, ACTIONS, DEMANDS,  LIABILITIES,  EXPENSES AND
LOSSES,  INCLUDING  REASONABLE  LEGAL  EXPENSES AND ATTORNEYS'  FEES  ("LOSSES")
RESULTING DIRECTLY OR INDIRECTLY FROM ANY ACTIVITY PERFORMED BY THE INDEMNIFYING
PARTY PURSUANT TO THIS AGREEMENT,  INCLUDING BUT NOT NECESSARILY  LIMITED TO THE
MANUFACTURE,  DEVELOPMENT,  USE, HANDLING, STORAGE, SALE OR OTHER DISPOSITION OF
CHEMICAL AGENTS,  COLLABORATION  COMPOUNDS,  ACTIVE  COMPOUNDS,  LEAD COMPOUNDS,
DEVELOPMENT  COMPOUNDS OR PRODUCTS BY SUCH PARTY,  ITS  AFFILIATES  OR LICENSEES
except to the extent such Losses  result  from the gross  negligence  or willful
misconduct of the Party claiming a right of  indemnification  under this Article
13.

     13.2 Indemnification.

     (a) Subject to Section 13.2(c) below,  ImClone shall hold CombiChem and its
officers,  directors,  employees,  consultants,  and  agents  harmless  from and
against any and all losses  resulting from the  infringement  of any Patent of a
Third Party due to the performance by

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       18
<PAGE>

ImClone of any activity contemplated hereunder,  including,  but not necessarily
limited to,  ImClone's  responsibilities  under  Section  2.2 above,  developing
Products, and selling Products.

     (b) Subject to Section 13.2(c) below,  CombiChem shall hold ImClone and its
officers,  directors,  employees,  consultants,  and  agents  harmless  from and
against any and all losses  resulting from the  infringement  of any Patent of a
Third Party due to the  performance  by CombiChem  of any activity  contemplated
hereunder,    including,   but   not   necessarily   limited   to,   CombiChem's
responsibilities under Section 2.1 above.

     (c) The indemnity  provided in Sections 13.2(a) and 13.2(b) above shall not
apply where the loss is due to the breach by the indemnified Party of a warranty
made in Article 19.

     13.3 Procedures.  If either Party seeks  indemnification under this Article
13, it shall inform the other Party of a claim as soon as reasonable practicable
after it receives  notice of the claim,  shall  permit the other Party to assume
direction and control of the defense of the claim (including the right to settle
me claim solely of the other Party),  and shall give reasonable  cooperation (at
the expense of the other Party) in the defense of the claim.

     14. ASSIGNABILITY

     This  Agreement  may not be  assigned  by either  Party  without  the prior
written  consent of the other Party;  provided,  however,  that either Party may
assign this Agreement, in whole or in part, to an Affiliate or to a successor of
a  Party  in  connection  with  the  merger,  consolidation  or  sale  of all or
substantially  all of such  Party's  assets  or  that  portion  of its  business
pertaining to the subject matter of this Agreement.

     15. DISPUTE RESOLUTION PROCEDURES

     15.1  Senior  Executives  Discussions.  If a decision is not reached by the
RMC, the dispute will be resolved as set forth in Article 6 above.  If a dispute
arises  between  CombiChem  and ImClone with  respect to matters  other than the
management of the Research Program,  either during or after the Research Period,
such dispute will be referred to the appropriate  senior  management in the area
of the dispute.  If such senior  management  are unable to resolve such dispute,
such dispute will be referred to the Chief  Executive  Officers of CombiChem and
ImClone.  If such  officers are unable to reach an agreement  within thirty (30)
days following the initiation of discussions between them, such dispute shall be
settled by arbitration as described in Section 15.2 below.

     15.2 Binding Arbitration.  If the parties have not been able to resolve the
dispute as provided in Section 15.1 above,  the dispute shall be finally settled
by binding arbitration. Any arbitration hereunder shall be conducted under rules
of the American  Arbitration  Association.  The  arbitration  shall be conducted
before one (1)  arbitrator  chosen by mutual  agreement of the  Parties.  If the
Parties cannot agree on the choice of the  arbitrator  within a period of thirty
(30) days after 

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       19
<PAGE>

submission,  then the arbitrator  shall be appointed by the Court of Arbitration
of the American Arbitration Association. Any such arbitration shall be held in a
mutually  agreeable  location;  provided,  however that if the parties cannot so
agree,  the location(s)  for such  arbitration(s)  shall  alternate  between San
Diego,  California and New York, New York, with the first such arbitration to be
located in San Diego,  California.  The arbitrators  shall have the authority to
grant  specific  performance,  and to allocate  between the parties the costs of
arbitration  in such equitable  manner as he or she may determine.  The arbitral
award (i) shall be final and binding upon the  parties;  and (ii) may be entered
in any court of competent jurisdiction.

     15.3 Injunctive  Relief.  Nothing contained in this Article 15 or any other
provisions  of this  Agreement  shall be  construed to limit or preclude a Party
from bringing any action in any court of competent  jurisdiction  for injunctive
or other  provisional  relief to  compel  the  other  Party to  comply  with its
obligations hereunder before or during the pendency of arbitration proceedings.

     16. NOTICES

     Any notice  required or  permitted  to be given  hereunder  shall be deemed
sufficient  if sent by facsimile  letter or overnight  courier,  or delivered by
hand to ImClone or CombiChem at the respective  addresses and facsimile  numbers
as set forth below or at such other address and facsimile number as either Party
hereto may designate.  If sent by facsimile letter, notice shall be deemed given
when the  transmission  is completed if the sender has a confirmed  transmission
report. If a confirmed  transmission report does not exist, then the notice will
be deemed given when the notice is actually received by the person to whom it is
sent.  If delivered by overnight  courier,  notice shall be deemed given when it
has been signed for. If  delivered  by hand,  notice  shall be deemed given when
received.

         if to CombiChem, to:   CombiChem, Inc.
                                9050 Camino Santa Fe San Diego, California 92121
                                Attention: President
                                Fax number: (619) 530-9998

         with a copy to:        Brobeck, Phleger & Harrison LLP
                                550 South Hope Street, 21st Floor
                                Los Angeles, California 90071
                                Attention: Laurie A. Allen, Esq.
                                Fax number: (213) 239-1324

         if to ImClone, to:     ImClone Systems Incorporated
                                180 Varick Street
                                New York, New York 10014
                                Attn: Vice President, Business Development
                                Fax number: (212) 645-2054

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       20
<PAGE>

         with a copy to:       Hoffmann and Baron
                               350 Jericho Turnpike
                               Jericho, New York 11753
                               Attn: Irving N. Feit, Esq.
                               Fax number:  (516) 822-3582

     17. SURVIVAL

     The provisions of Sections 2.5, 5.1, 5.2,  7.2(c),10.3,  10.4, and Articles
1, 3, 8, 9, 11,  12,  13,  14,  15,  16, 18 and this  Article  17 shall  survive
termination  of this  Agreement in addition to those  provisions  which by their
terms survive.

     18. ADDITIONAL TERMS

     18.1  Entire  Agreement.  This  Agreement  and the  Common  Stock  Purchase
Agreement constitute the entire  understanding  between the Parties with respect
to  the  subject   matter  hereto  and  supersedes  and  replaces  all  previous
negotiations, understandings,  representations, writings and contract provisions
and  rights  relating  hereof.  The  Parties  agree that all  services  provided
hereunder shall be subject to and governed by the terms and provisions set forth
herein, and none of the terms and conditions contained on any proposal, purchase
order,  invoice or other writing shall have any effect or change the  provisions
of this Agreement.

     18.2 Amendment;  No Waiver.  No provision of this Agreement may be amended,
revoked or waived  except by a writing  signed and  delivered  by an  authorized
officer of each Party.  Any waiver on the part of either  Party of any breach or
any fight or  interest  hereunder  shall not imply the waiver of any  subsequent
breach or waiver of any other right or interest.

     18.3 Validity.  The invalidity or unenforceability of any provision of this
Agreement shall not affect the validity or enforceability of any other provision
of this  Agreement,  each of which  shall  remain in full force and  effect.  In
addition,  should the  invalidity or  unenforceability  of any provision of this
Agreement  cause an  unintended  result or result  in any  unfairness  to either
Party,  then ImClone and  CombiChem  shall  promptly  meet and negotiate in good
faith to modify or amend this  Agreement  to change such result or to  eliminate
such unfairness.

     18.4 Headings.  The  descriptive  headings are inserted for  convenience of
reference only and are not intended to be part of or to affect the meaning of or
interpretation of this Agreement.

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

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       21
<PAGE>

     18.6 Governing  Law. This Agreement  shall be governed by and construed and
enforced in accordance with the laws of the State of California,  without regard
to conflicts of laws principles.

     19. WARRANTY

     Each  Party  warrants  that it has the  power  to grant  all of the  rights
granted and make such required assignments, and to assume all of the obligations
required,  under this Agreement.  If, at the time a Patent  application is to be
filed by ImClone with respect to any Active Compound, Lead Compound, Development
Compound or Products,  CombiChem informs ImClone that CombiChem has the power to
grant the exclusive rights to such Active Compound,  Lead Compound,  Development
Compound or Products,  and to assign such Patents related thereto, to ImClone in
accordance with Sections 3.2 and 5.2 above,  CombiChem further warrants that, in
fact,  as of such date,  it has such power  subject to the proviso that under no
circumstances  does  CombiChem  warrant to ImClone that its rights in any Active
Compound,  Lead Compound,  Development Compound or Products are exclusive to the
extent such Active Compound, Lead Compound, Development Compound or Products may
be covered under the patent claims of Third Parties  wherein such claims are not
the direct result of a collaboration between the Third Party and CombiChem.

     IN  WITNESS  WHEREOF,  the  parties  have  executed  this  Agreement  to be
effective as of the Effective Date.

COMBICHEM, INC.                                   IMCLONE SYSTEMS INCORPORATED

By:  /s/ Vicente Anido                            By:  /s/ Carl S. Goldfischer
----------------------                            ----------------------------
Its: President and CEO                            Its: CFO

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.


                                       22
<PAGE>

                                   Appendix A

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

                                       ***

***  Portions  of  this  page  have  been  omitted  pursuant  to a  request  for
     Confidential Treatment and filed separately with the Commission.

<PAGE>

                                   Appendix B

                               Milestone Payments
              (Triggered by Activities of ImClone or Its Licensees)


Development Milestone                          Milestone Payment

        ***
        ***                                     U.S.     ***

        ***                                     U.S.     ***
        ***

        ***                                     U.S.     ***
        ***

        ***                                     U.S.     ***
        ***
        ***                                    __________________

                            Total               U.S.     ***


legal\highriver\combicon.doc


***      Portions  of this page  have been  omitted  pursuant  to a request  for
         Confidential Treatment and filed separately with the Commission.