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                                                                     EXHIBIT 2.2

                CORE TECHNOLOGY DEVELOPMENT AND LICENSE AGREEMENT
                                 by and between
                         MICROCIDE PHARMACEUTICALS, INC.
                                       and
                                 EPIGENIX, INC.


         This CORE TECHNOLOGY DEVELOPMENT AND LICENSE AGREEMENT (the
"Agreement") is entered into as of the 14th day of January, 1998 (the "Effective
Date") by and between MICROCIDE PHARMACEUTICALS, INC., a Delaware corporation
having a principal place of business at 850 Maude Ave., Mt. View, CA 94043
("Microcide"), and EPIGENIX, INC., a Delaware corporation having a principal
place of business at 850 Maude Ave., Mt. View, CA 94043 ("EpiGenix"), with
reference to the following:

                                    RECITALS

         WHEREAS Microcide is a biopharmaceuticals company in the business of
discovering, developing, and commercializing novel antimicrobials for the
treatment of serious bacterial and fungal infections;

         WHEREAS EpiGenix is a company established to use genomic approaches,
including surrogate genetics, to discover, develop, and commercialize products
for use in human health, animal health, agriculture, and the like; and

         WHEREAS the parties wish to develop products in their respective
fields, based on existing technology owned and retained by Microcide and
existing technology owned by Microcide and transferred or licensed to EpiGenix,
as well as on new technology developed during a period of joint development; and

         WHEREAS the parties have entered into a Stock Purchase Agreement, by
which Microcide is acquiring certain shares of stock in EpiGenix (the "Stock
Purchase Agreement"), and an Anti-Viral Research Collaboration Agreement, by
which the parties agree to collaborate in developing certain viral therapeutics
technology (the "Research Collaboration Agreement"), both of which are executed
concurrently herewith (collectively, the "Ancillary Agreements");

         NOW, THEREFORE, in consideration of the mutual covenants and conditions
set forth in this Agreement and in the Ancillary Agreements, and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties do hereby agree as follows:


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                                    AGREEMENT

SECTION 1:  DEFINITIONS AND RULES OF CONSTRUCTION

1.1 Definitions. For purposes of this Agreement, the following words and phrases
shall have the following meaning:

         "Affiliate" shall mean, with respect to a party, any person,
corporation or other business entity that directly, or indirectly through one or
more intermediaries, controls or is controlled by, or is under common control
with, a party. For this purpose, control of a corporation or other business
entity shall mean direct or indirect beneficial ownership of fifty percent (50%)
or more of the voting interest in, or a fifty percent (50%) or greater interest
in the equity of, such corporation or other business entity.

         "Assigned Technology" shall mean the issued patents, pending patent
applications, invention disclosures and certain technology owned by Microcide,
which Microcide has the right to assign to EpiGenix without obligation (or for
which EpiGenix agrees to pay any sublicensing royalties) relating to Surrogate
Genetics, informatics and genome sciences [ * ], or relating primarily to the
EpiGenix Field, as more specifically identified in Exhibit A together with a
description of any applicable royalties.

         "Change in Control" shall mean the occurrence of one of the following
events or circumstances with respect to a party to this Agreement:

                  (a) as a result of a tender or exchange offer, open market
purchases, privately negotiated purchases, consolidation, merger or otherwise,
any entity or individual becomes the beneficial owner, as defined in Rule 13d-3
under the Securities Exchange Act of 1934, directly or indirectly, of fifty
percent (50%) of the then outstanding voting shares or other equity interests of
a party;

                  (b) in any share exchange, extraordinary dividend,
acquisition, disposition or recapitalization (or series of related transactions
of such nature), the holders of voting securities of the respective party
immediately prior thereto do not continue to beneficially own voting securities
or other equity interests representing at least a majority of the same ownership
and voting interests of the total combined entity (or any successor entity)
immediately thereafter;

                  (c) the party files a petition in bankruptcy, insolvency or
similar law for the protection of all or a substantial portion of its assets
against creditors whether such filing is in a state or federal court and whether
it is on a voluntary or involuntary basis, provided such filing or plan is not
dismissed or vacated within thirty (30) days, or a plan of liquidation or
dissolution of a party is submitted to and approved by the holders of voting
securities of such party;

                  (d) the sale or disposition by a party (in one transaction or
a series of transactions) of all or substantially all of such party's assets;

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                  (e) any entity or individual is granted the right to appoint a
majority of the members of the board of directors of the respective party
through a proxy contest or otherwise; or

                  (f) the board of directors of a party approves, or that party
enters into, an agreement providing for a transaction, event or development that
constitutes (or would constitute if consummated) a Change of Control of that
party pursuant to (a) through (e) above.

         "FDA" shall mean the United States Food and Drug Administration or any
successor agency thereof.

         "Intellectual Property Rights" shall mean, collectively, worldwide
Patents, Trade Secrets, Copyrights, Trademarks, moral rights, know-how (whether
or not patentable), and all other intellectual property rights and proprietary
rights, whether arising under the laws of the United States or any other state,
country or jurisdiction, including all rights or causes of action for
infringement or misappropriation of any of the foregoing. For purposes of this
Agreement: (i) "Patents" shall mean all patent rights and all right, title, and
interest in all letters patent or equivalent rights and applications, including
provisional applications, and all government issued or granted indicia of
invention ownership, including any reissue, extension, division, continuation,
or continuation-in-part applications and patents throughout the world; (ii)
"Trade Secrets" shall mean all right, title and interest in all trade secrets
and trade secret rights arising under common law, state law, federal law or laws
of foreign countries; (c) "Copyrights" shall mean all copyrights, all other
literary property and authorship rights, and all right, title, and interest in
all copyrights, copyright registrations, certificates of copyright and copyright
interests throughout the world; and (iii) "Trademarks" shall mean all right,
title, and interest in all trademark, service mark, trade name, and trade dress
rights arising under the common law, state law, federal law, and laws of foreign
countries, and all right, title, and interest in all trademark, service mark,
trade name, domain name, and trade dress applications and registrations
interests throughout the world.

         "Joint Technology" shall mean that technology, including Intellectual
Property Rights therein, jointly developed by the parties during the three (3)
year period following the Effective Date, in the areas of molecular diversity,
high throughput screening ("HTS"), informatics, and genomic sciences, and such
other technology as the parties shall mutually agree. The parties hereto agree
that the Joint Technology Committee shall amend Exhibit F attached hereto to
include a definition of such technology within thirty (30) days after the
Effective Date.

         "Licensed Patents" shall mean the Patents, invention disclosures, owned
or licensed by Microcide, which Microcide has the right to license to EpiGenix
without obligation (or for which EpiGenix agrees to pay any sublicensing
royalties), and relating to both the EpiGenix Field and fields of use outside
the EpiGenix Field, as listed in Exhibit B.

         "Licensed Technology" shall mean all technology, including Intellectual
Property Rights therein, owned or licensed by Microcide (other than the Assigned
Technology and Joint Technology), including Licensed Patents which Microcide has
the right to license to EpiGenix 


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without obligation (or for which EpiGenix agrees to pay any sublicensing
royalties), as of the Effective Date of this Agreement, and during the three (3)
years following the Effective Date (provided that such period shall terminate
earlier upon the closing of a transaction in which EpiGenix or Microcide shall
consummate a Change in Control), and in each case which are necessary or
materially useful in the EpiGenix Field; provided, however, [ * ].

         "Microcide Field" shall mean research and development of products for
infectious diseases caused by bacteria, fungi, viruses or other infectious
agents, for use in [ * ].

         "Microcide Joint Technology" shall mean the Joint Technology primarily
relating to molecular diversity and HTS technology.

         "EpiGenix Field" shall mean research, development and commercialization
of products using genomics (for gene identification), functional genomics (for
functional characterization), genetic-based assays, including Surrogate
Genetics, for uses such as [ * ], to discover and develop products such as but
not limited to [ * ], for use in human health, animal health, agriculture or
other applications, except for infectious diseases caused by bacteria or fungi.

         "EpiGenix Inner Field" shall mean the non-infectious diseases [ * ]
portion of the EpiGenix Field that relates to products for [ * ].

         "Development Stage Product" shall mean any compound or potential
product entity identified and selected other than by Microcide for development
for which formal preclinical testing (such as GLP toxicological and
pharmacological studies as well as product substance, product formulation and
manufacturing development activities) are being undertaken or are planned to be
undertaken reasonably promptly, using reasonable commercial efforts to develop
and register the entity as a product.

         "EpiGenix Joint Technology" shall mean the Joint Technology primarily
relating to informatics and genome science technology.

         "EpiGenix Technology" shall mean all technology, including Intellectual
Property Rights therein, owned or licensed by EpiGenix (other than Joint
Technology), including the Assigned Technology, necessary or materially useful
in the Microcide Field, which EpiGenix has the right to license to Microcide
without obligation (or for which Microcide agrees to pay any 

* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.

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sublicensing royalties) as of the Effective Date and during the three (3) years
following the Effective Date; provided, however, that such period shall
terminate upon the closing of a transaction in which EpiGenix or Microcide shall
consummate a Change in Control; provided, further, [ * ].

         "Regulatory Approval" shall mean the granting of all governmental or
regulatory approvals required, if any, for the sale of a Licensed Product in a
given country or jurisdiction within the Territory, including without
limitation, FDA approval in the United States.

         "Surrogate Genetics" shall mean the use of genetically engineered
recipient cells, such as, but not limited to bacteria, fungi, worm, fly, or
mammalian cells, to create heterologous systems useful for gene-based functional
assays for any gene, in applications such as, but not limited to gene discovery,
functional genomics, drug screening, phenoprinting and diagnostics.

1.2 Rules of Construction. As used in this Agreement, all terms used in the
singular shall be deemed to include the plural, and vice versa, as the context
may require. The words "hereof," "herein" and "hereunder" and other words of
similar import refer to this Agreement as a whole, including any exhibits
hereto, as the same may from time to time be amended or supplemented. The word
"including" when used herein is not intended to be exclusive and means
"including, without limitation." The descriptive headings of this Agreement are
inserted for convenience of reference only and do not constitute a part of and
shall not be utilized in interpreting this Agreement. The terms "party" and
"parties" shall refer to Microcide and EpiGenix, individually or collectively.
This Agreement has been negotiated by the parties hereto and their respective
counsel and shall be fairly interpreted in accordance with its terms and without
any rules of construction relating to which party drafted the Agreement being
applied in favor of or against either party.

SECTION 2:  LICENSE GRANTS; ASSIGNMENT.

2.1 License from EpiGenix to Microcide. Subject to the rights of third parties
heretofore or hereafter existing with regard to technology developed after the
Effective Date, and to the extent that it is legally able to do so, EpiGenix
grants to Microcide a worldwide, royalty free, perpetual license, under
EpiGenix's Intellectual Property Rights in and to the EpiGenix Technology,
Assigned Technology, and the EpiGenix Joint Technology for use in: (i) the
antibacterial and antifungal portions of the Microcide Field on an exclusive
basis for the period of [ * ] after the Effective Date; (ii) the remainder of
the Microcide Field on a co-exclusive basis (together with EpiGenix) basis for
the period of [ * ] after the Effective Date; and (iii) thereafter on a
non-exclusive basis within and outside the Microcide Field; provided, however,
that in the event any Intellectual Property Rights are developed that are
considered part of the [ * ] program at EpiGenix and not developed pursuant to
the Research Collaboration Agreement or other collaboration agreements between
EpiGenix and Microcide, 

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then Microcide shall obtain no rights to such Intellectual Property Rights. The
rights shall include the right to sublicense, and all the customary rights to
make, have made, use, offer to sell, sell, have sold, import, export,
distribute, and have distributed products using the EpiGenix Technology,
Assigned Technology, and EpiGenix Joint Technology.

2.2 License from Microcide to EpiGenix. Subject to the rights of third parties
heretofore or hereafter existing and to the extent that it is legally able to do
so, Microcide grants to EpiGenix a worldwide, royalty-free, perpetual license,
under all Microcide's Intellectual Property Rights, in and to the Licensed
Technology and the Microcide Joint Technology for use in: (i) the EpiGenix Inner
Field, on an exclusive basis, for the period of [ * ] after the Effective Date;
(ii) the remainder of the EpiGenix Field on a co-exclusive basis (together with
Microcide) for the period of [ * ] after the Effective Date; and (iii)
thereafter on a non-exclusive basis within and outside the EpiGenix Field. The
rights shall include the right to sublicense, and all of the customary rights to
make, have made, use, offer to sell, sell, have sold, import, export,
distribute, and have distributed products developed using the Licensed
Technology, Licensed Patents, and Microcide Joint Technology.

2.3 Assignment. Subject to the license granted in Section 2.1 above, Microcide
agrees to irrevocably assign to EpiGenix all right, title and interest in and to
the Assigned Technology, and agrees to execute the Assignment Agreement,
attached hereto as Exhibit E, concurrently herewith. In addition, Microcide
agrees to execute all documents, and to fully cooperate as necessary and as
reasonably requested by EpiGenix to effect such assignment.

SECTION 3: PRODUCT DEVELOPMENT.

3.1      Joint Technology Committee.

         (a) Microcide and EpiGenix shall form a Joint Technology Committee
which shall meet no less than quarterly or as otherwise mutually agreed to
oversee the transfer of technology, coordinate the joint research conducted
pursuant to this Agreement, and, prior to the end of any particular calendar
year, to establish a work plan for the ensuing calendar year for each party to
develop or acquire such technology, including, without limitation, specifying
the amount to be paid therefor by each party and the number of full time
employees to be assigned to the work plan. A draft of an initial work plan for
the first year is set forth hereto as Exhibit D, which will be revised and
modified in good faith by the parties to reflect the mutual agreement of the
parties over a period not to exceed sixty (60) days from the Effective Date. The
Joint Technology Committee will be composed of an equal number of voting
representatives from each of Microcide and EpiGenix (not to exceed three (3)
representatives per party).

         (b) All decisions of the Joint Technology Committee will require a
unanimous vote of such committee. A quorum shall not exist for the purpose of a
vote of the Joint Technology Committee unless all members thereof are in
attendance. In the event of an inability of the Joint Technology Committee to
reach a decision on any issue, then such issue shall be submitted to the CEOs of
both parties. In the event that the CEOs are unable to reach a decision on such
issue, 

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then the matter shall go to arbitration pursuant to Section 11.6 hereto. Any
decision by the Joint Technology Committee shall be binding upon the parties.

         (c) Either EpiGenix or Microcide may recommend changes, additions or
deletions to any work plan to the Joint Technology Committee which then will
consider whether to approve such changes in good faith. Any and all Confidential
Information, including Licensed Technology and Assigned Technology as well as
Microcide Joint Technology or EpiGenix Joint Technology, shall be provided to
the Joint Technology Committee and shall be disclosed to others within EpiGenix
or Microcide solely to assist either of them in conducting their respective
responsibilities under the Agreement or as necessary to utilize the license
rights granted under the Agreement.

3.2 Costs of Joint Technology Committee. In the event that the parties are each
located in separate cities, each party shall pay its own travel and lodging
expenses incurred in connection with the meetings of the Joint Technology
Committee described in Section 3.1, which meetings shall alternate between
locations so as to balance travel requirements and expenses. Each party shall
use reasonable efforts to cause its respective representatives to attend all
meetings of the Joint Technology Committee.

3.3 Joint Technology Development. During the three (3) year period following the
Effective Date (the "Joint Development Period"), the parties shall jointly work
to develop and utilize Joint Technology; provided, however, that the Joint
Development Period shall terminate upon the closing of a transaction in which
EpiGenix or Microcide shall consummate a Change in Control. During the Joint
Development Period, Microcide shall primarily be responsible for developing
molecular diversity and HTS technology, and EpiGenix will primarily be
responsible for developing informatics and genome science technology. In the
event that the parties cannot agree on the appropriate allocation of payment to
develop Joint Technology, either party shall be free to develop or have
developed such technology on its behalf, at its own expense, and shall
thereafter solely own such technology ("Non-Joint Technology"), subject to the
licenses granted pursuant to Section 2 hereto; provided, however, that any
license granted under Non-Joint Technology from one party to the other pursuant
to Section 2, shall commence on the date that is [ * ] after the Effective Date
(the "Non-Joint Technology License Date"); provided, further, that if during
such [ * ] the licensee desires to have such license commence prior to the
Non-Joint Technology License Date, the licensor shall negotiate in good faith
such a license, contingent upon such licensee agreeing to pay a mutually agreed
portion of the development costs associated with the development of such
Non-Joint Technology.

3.4 Costs of Joint Technology Development. Costs incurred in connection with the
development of the Joint Technology will be accounted for and paid as determined
by the Joint Technology Committee pursuant to the relevant work plan.

3.5 Permitted Use of Information and Assistance. EpiGenix and Microcide each
shall be entitled to use the information and assistance furnished by the other
party pursuant to this Section 3 solely as necessary to fulfill the obligations
set forth in this Agreement, without incurring any 

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additional royalty or other payment obligation. All such information and
assistance shall be deemed Confidential Information as defined in Section 9.1
hereto.

3.6 Delivery of Materials. Promptly after the Effective Date, and at regular
intervals thereafter: (i) Microcide will deliver to EpiGenix all materials owned
or licensed by Microcide, which Microcide has the right to license to EpiGenix,
that constitute the Licensed Patents, Licensed Technology, Microcide Joint
Technology, and Assigned Technology, or as necessary for EpiGenix to exercise
its rights thereto; and (ii) EpiGenix will deliver to Microcide all materials
and things that constitute the EpiGenix Technology, EpiGenix Joint Technology,
or as necessary for Microcide to exercise its rights thereto.

SECTION 4:  OBLIGATIONS OF THE PARTIES

4.1 Non-Compete Obligations of EpiGenix. For a period of [ * ] from the
Effective Date of this agreement (the "Non-Compete Period"), EpiGenix agrees
that it will not undertake any efforts to discover, develop, commercialize,
offer to sell, sell, or distribute (alone or jointly with others, or authorize
others to do so) any products in the [ * ] EpiGenix further agrees not to
undertake any efforts to discover, develop, commercialize, offer to sell, sell
or distribute (alone or jointly with others, or authorize others to do so)
products in the [ * ] that utilize, are derived from, based upon or developed
using the [ * ] for a period of [ * ] after the Effective Date, and only to the
extent that each such technology is not in the public domain and freely
available for use at the time.

4.2 Non-Compete Obligations of Microcide. For a period of [ * ] from the
Effective Date, Microcide agrees that it will not undertake any efforts to
discover, develop, commercialize, offer to sell, sell, or distribute (alone or
jointly with others, or authorize others to do so) any products in the [ * ] and
for a period of [ * ] thereafter Microcide agrees that it will not undertake any
efforts to discover, develop, commercialize, offer to sell, sell, or distribute
(alone or jointly with others, or authorize others to do so) any products within
the [ * ] in a program area in which EpiGenix has entered into a corporate
collaboration or has undertaken an effort consisting of at least [ * ] Microcide
further agrees not to undertake any efforts to discover, develop, commercialize,
offer to sell, sell, or distribute (alone or jointly with others, or authorize
others to do so) products in the [ * ] using (i) [ * ] for a period of [ * ]
from the Effective Date, or (ii) [ * ] for a period of [ * ] after the Effective
Date, and only to the extent that each such technology is not in the public
domain and freely available for use at the time; provided, however, that
Microcide may use the [ * ] in the [ * ] Microcide further agrees not to
undertake any efforts to discovery, develop, commercialize, offer to sell, sell,
or distribute (alone or jointly with others, or authorize others to do so)
products in the [ * ] that utilize, are derived from, based upon or developed
using the [ * ] for a period of [ * ] after the Effective Date.

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4.3 Disclosure. For a period of [ * ] after the Effective Date, each party will
promptly disclose to the other, by means of the Joint Technology Committee or
otherwise, any new inventions, improvements, derivative works, enhancements, and
know-how developed by or for such party and relating to: (i) the [ * ] in the
case of Microcide; or (ii) the [ * ] in the case of EpiGenix.

4.4 Inventions. In the event that EpiGenix solely invents or discovers any
improvement(s) or modification(s) solely applicable to: (i) Microcide
Technology, then ownership therein shall be solely in Microcide; or (ii)
EpiGenix Technology, then ownership therein shall be solely in EpiGenix. In the
event that Microcide solely invents or discovers any improvement(s) or
modification(s) solely applicable to: (x) EpiGenix Technology, then ownership
therein shall be solely in EpiGenix; or (y) Microcide Technology, then ownership
therein shall be solely in Microcide. Each party shall fully cooperate in
assuring that all rights in and to such inventions and discoveries are fully
vested in the other party in accordance with this Section 4.4. Each party shall
promptly notify the other party of any such inventions or discoveries set forth
in this Section 4.4.

SECTION 5:  PATENT PROSECUTION.

5.1 Microcide Rights and Obligations. Microcide will have primary responsibility
for prosecuting and paying maintenance fees relating to the Licensed Patents and
for filing, prosecuting, and maintaining patent applications relating to the
Licensed Technology and Microcide Joint Technology, at Microcide's sole expense,
and in any and all countries in Microcide's sole discretion. EpiGenix will
cooperate fully with Microcide in connection with all filings and prosecution of
the Microcide Joint Technology. In the event that Microcide elects to abandon
any patent or claimed invention, or issued patent, or to withhold patenting any
disclosed invention, in any country, then Microcide shall provide EpiGenix with
at least sixty (60) days prior notice before the applicable deadline or
statutory bar of its election not to file, prosecute, or maintain any one of the
Licensed Patents or patents or patent applications relating to the Microcide
Joint Technology or Licensed Technology. If Microcide makes such election, then
EpiGenix will have the right to file, prosecute, or maintain the same at
EpiGenix's sole cost and expense, and Microcide will cooperate with EpiGenix's
filing, prosecution, and maintenance, as applicable, at EpiGenix's expense.

5.2 EpiGenix Rights and Obligations. EpiGenix will have the primary
responsibility for filing, prosecuting and paying maintenance fees relating to
the Assigned Technology, EpiGenix Technology, and EpiGenix Joint Technology, at
EpiGenix's sole expense, and in any and all countries in EpiGenix's sole
discretion. Microcide will cooperate fully with EpiGenix in connection with all
filings and prosecution of the EpiGenix Joint Technology. In the event EpiGenix
elects to abandon any patent or claimed invention, or issued patent, or to
withhold patenting any disclosed invention, in any country, then EpiGenix shall
provide Microcide with at least sixty (60) days prior notice before the
applicable deadline or statutory bar of its election not to file, prosecute, or
maintain any one of the patents or patent applications relating to the Assigned
Technology, EpiGenix Technology, or EpiGenix Technology. If EpiGenix makes such

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election, then Microcide will have the right to file, prosecute or maintain the
same at Microcide's sole cost and expense, and EpiGenix will cooperate with
EpiGenix's filing, prosecution, and maintenance, as applicable, at Microcide's
expense.

SECTION 6:  ENFORCEMENT RIGHTS.

6.1 Microcide Rights and Obligations. Microcide will have primary responsibility
for enforcing the Licensed Technology, Licensed Patents, and Microcide Joint
Technology rights with respect to third party infringers. Microcide shall use
diligent, good faith efforts to enforce all Intellectual Property Rights
included within the Licensed Technology, Licensed Patents, and Microcide Joint
Technology that would be infringed by the manufacture, use or sale by an
unlicensed party of products based on, derived from, or incorporating any such
Licensed Technology, Licensed Patents, or Microcide Joint Technology
(collectively, the "Microcide Rights"). Upon learning of a significant and
continuing infringement of any Microcide Rights by a Third Party, Microcide or
EpiGenix, as the case may be, promptly shall provide notice to the other party
in writing of the fact and shall supply the other party with all evidence
possessed by the notifying party pertaining to said infringement(s). Microcide
shall have ninety (90) days from the giving of notice under this Section 6.1, or
such lesser period of time if a further delay would result in material harm to,
or the loss of a material right of EpiGenix, to abate the infringement, or to
file suit against at least one of the infringers, at its sole expense, following
consultation with EpiGenix. If Microcide does not, within ninety (90) days of
the giving of such notice, or such lesser period of time if a further delay
would result in material harm to, or the loss of a material right of, EpiGenix,
abate the infringement or file suit to enforce the Microcide Rights, EpiGenix
shall have the right, at its own expense, to take whatever action it deems
appropriate in its own name or, if required by law, in the name of Microcide, to
enforce the Microcide Patent Rights. All monies recovered upon the final
judgment or settlement of any such suit shall be retained by the party bearing
the costs of enforcement of the Microcide Rights.

6.2 EpiGenix Rights and Obligations. EpiGenix will have primary responsibility
for enforcing the Assigned Technology, EpiGenix Technology, and EpiGenix Joint
Technology rights with respect to third party infringers. EpiGenix shall use
diligent, good faith efforts to enforce all Intellectual Property Rights
included within the Assigned Technology, EpiGenix Technology, and EpiGenix Joint
Technology that would be infringed by the manufacture, use or sale by an
unlicensed party of products based on, derived from, or incorporating any such
Assigned Technology, EpiGenix Technology, and EpiGenix Joint Technology
(collectively, the "EpiGenix Rights"). Upon learning of a significant and
continuing infringement of any EpiGenix Rights by a Third Party, EpiGenix or
Microcide, as the case may be, promptly shall provide notice to the other party
in writing of the fact and shall supply the other party with all evidence
possessed by the notifying party pertaining to said infringement(s). EpiGenix
shall have ninety (90) days from the giving of notice under this Section 6.2, or
such lesser period of time if a further delay would result in material harm to,
or the loss of a material right of Microcide, to abate the infringement, or to
file suit against at least one of the infringers, at its sole expense, following
consultation with Microcide. If EpiGenix does not, within ninety (90) days of
the giving of such notice, or such lesser period of time if a further delay
would result in material harm to, or the loss of a material right of Microcide,
abate the infringement or file suit to 


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enforce the EpiGenix Rights, Microcide shall have the right, at its own expense,
to take whatever action it deems appropriate in its own name or, if required by
law, in the name of EpiGenix, to enforce the EpiGenix Rights. All monies
recovered upon the final judgment or settlement of any such suit shall be
retained by the party bearing the costs of enforcement of the EpiGenix Rights.

SECTION 7:  REPRESENTATIONS AND WARRANTIES

7.1 Microcide Representations and Warranties. Microcide hereby represents and
warrants to EpiGenix that: (i) Microcide has the right to enter into and perform
Microcide's obligations under this Agreement and to grant the licenses granted
herein; (ii) to the best of Microcide's knowledge and belief, the execution,
delivery, and performance of this Agreement does not conflict with, violate, or
breach any agreement of Microcide or with Microcide's Certificate of
Incorporation or Bylaws; (iii) to the best of its knowledge and belief it owns
all unencumbered rights to the Licensed Patents and Assigned Technology; (iv) to
the best of Microcide's knowledge and belief it has not received any written
communication alleging infringement of any third party Intellectual Property
Rights with regard to the Licensed Patents or Assigned Technology.

7.2 EpiGenix Representation and Warranties. EpiGenix hereby represents and
warrants to Microcide that: (i) EpiGenix has the right to enter into and perform
EpiGenix's obligations under this Agreement and to grant the licenses granted
herein; (ii) to the best of EpiGenix's knowledge and belief, the execution,
delivery, and performance of this Agreement does not conflict with, violate, or
breach any agreement of EpiGenix or with EpiGenix's Certificate of Incorporation
or Bylaws.

7.3 Disclaimer of Warranties. EXCEPT AS SPECIFICALLY SET FORTH HEREIN, NEITHER
PARTY MAKES ANY OTHER REPRESENTATIONS OR WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
PURPOSE OR USE AND ANY OTHER STATUTORY WARRANTIES.

SECTION 8:  INDEMNIFICATION

8.1 By Microcide. Subject to the provisions of Section 8.3 hereto, Microcide
hereby agrees at all times during the Term of this Agreement to be responsible
for, and to indemnify, defend and hold harmless EpiGenix from and against any
and all claims, actions, proceedings, expenses, liabilities or losses, including
reasonable legal expenses and costs, including attorney fees arising from or
based on a breach of Microcide's representations and warranties contained in
Section 7.1 hereto.

8.2 By EpiGenix. Subject to the provisions of Section 8.3 hereto, EpiGenix
hereby agrees to indemnify, defend and hold harmless Microcide from and against
any and all claims, actions, proceedings, liabilities or losses, including
reasonable legal expenses and costs, including attorney fees arising from or
based on a breach of EpiGenix's representations and warranties contained herein.


                                      -11-


   12
8.3 Notification. The parties shall promptly notify each other of any claims or
suits with respect to which indemnification is sought. The party requesting
indemnification shall permit the indemnifying party to assume the defense of
such claims or suits giving rise to the request at the indemnifying party's
expense. The requesting party shall cooperate with the indemnifying party in
such defense when reasonably requested to do so. No settlement or compromise
involving any liability or obligation on the part of a party to this Agreement
shall be binding on such party without such party's prior written consent, such
consent not to be unreasonably withheld.

8.4 Limitation of Liability. IN NO EVENT WILL EITHER PARTY HERETO BE LIABLE FOR
ANY SPECIAL, INCIDENTAL, CONSEQUENTIAL OR INDIRECT DAMAGES SUFFERED BY THE OTHER
PARTY ARISING IN ANY WAY OUT OF THIS AGREEMENT, HOWEVER CAUSED AND ON ANY THEORY
OF LIABILITY; PROVIDED HOWEVER, THAT THE FOREGOING LIMITATION SHALL NOT APPLY TO
A BREACH BY EITHER PARTY OF SECTION 9. THIS LIMITATION WILL APPLY EVEN IF THE
PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

SECTION 9:  CONFIDENTIALITY

9.1 "Confidential Information" shall mean any and all non-public and proprietary
information, including, without limitation, information relating to the
Intellectual Property Rights of the other party, the Licensed Technology,
Licensed Patents, Assigned Technology, EpiGenix Technology, or Joint Technology,
and the business plans of the other party, including information provided by
either party to the other party prior to the Effective Date, which such party
knows or has reason to know are or contain trade secrets or other proprietary
information of the other, and which is specifically designated as such and which
is disclosed by either party to the other in any form in connection with this
Agreement, and if orally disclosed, is reduced in writing and provided to the
other party within thirty (30) days of such disclosure. During the term of this
Agreement and thereafter, each party shall maintain in confidence all
Confidential Information and materials disclosed by the other party and shall
not use such Confidential Information for any purpose except as permitted by
this Agreement or disclose the same to anyone other than those of its
Affiliates, sublicensees, employees, consultants, agents or subcontractors as
are necessary in connection with such party's activities as contemplated in this
Agreement. Each party shall obtain a written agreement from any sublicensees,
employees, consultants, agents and subcontractors, prior to disclosure, to hold
in confidence and not make use of such Confidential Information for any purpose
other than those permitted by this Agreement.

9.2 Exceptions. Notwithstanding the above, neither party shall have liability to
the other with regard to any Confidential Information that: (i) is or becomes
publicly known through no wrongful act of the receiving party; (ii) was already
known to the receiving party; (iii) has rightfully been received from a third
party not under confidentiality obligations with respect to such information;
(iv) has been independently developed by the receiving party without reference
to or use of the other party's Confidential Information; (v) has been approved
for release by 


                                      -12-


   13
written authorization of the disclosing party; or (vi) is required to be
disclosed by the receiving party pursuant to the order or requirement of a
court, administrative agency, or other governmental body; provided, however,
that the receiving party shall provide reasonable advance notice to enable the
disclosing party to seek a protective order or otherwise prevent such
disclosure.

9.3 Agreement and Terms Confidential. Unless otherwise agreed to in writing or
as necessary to comply with a valid legal order of a court of law or agency of
competent jurisdiction or with the rules and regulations promulgated by the
Securities and Exchange Commission, both the existence and terms of this
Agreement shall be kept confidential by the parties.

9.4 Publication. Both parties agree not to publish any reports or papers, make
any public presentation or otherwise publicly disseminate any information
relating to any Confidential Information or other documentation or data
belonging to the other, and which was received pursuant to the terms of this
Agreement without first obtaining written consent of the other party hereto,
unless and to the extent disclosure of such documentation or data is necessary
to comply with any law or government regulations, and provided further that the
non-publishing party is so notified. Both parties also agree to provide each
other with a manuscript of any proposed publication or written summary of any
proposed oral disclosure at least twenty-one (21) days prior to submission
thereof for publication and to incorporate any changes in such manuscript as are
necessary to protect the Confidential Information of the non-publishing party.
EpiGenix and Microcide may also require the other to include an acknowledgment
of its role in any study to be published. Except as otherwise provided herein,
no right, express or implied, is granted by this Agreement to either party to
use in any manner the name of EpiGenix or Microcide or any other trade name or
trademark of the other party in connection with the performance of this
Agreement.

SECTION 10:  TERM AND TERMINATION

10.1 Term and Expiration. The term of this Agreement shall begin on the
Effective Date of this Agreement, and shall end at the expiration of the
last-to-expire Licensed Patent, unless earlier terminated pursuant to the
provisions of this Section 10. This Agreement may be terminated at any time upon
mutual agreement of the parties.

10.2 Termination With Cause. Upon any material breach of this Agreement or the
Stock Purchase Agreement by either party, the non-breaching party may terminate
this Agreement upon sixty (60) days written notice to the breaching party. The
notice shall become effective at the end of the thirty (60) day period unless
the breaching party shall cure such breach within such period.

10.3 Bankruptcy of Microcide. All rights and licenses granted under or pursuant
to this Agreement by Microcide to EpiGenix in respect of Licensed Patents,
Licensed Technology, and Microcide Joint Technology are and shall otherwise be
deemed to be, for purposes of Section 365(n) of the Bankruptcy Code, licenses of
rights to "Intellectual Property" as defined under Section 101(57) of the
Bankruptcy Code. The parties agree that EpiGenix, as licensee of such 


                                      -13-


   14
rights and licenses, shall retain and may fully exercise all of its rights and
elections under the Bankruptcy Code. The parties further agree that, in the
event that any proceeding shall be instituted by or against Microcide seeking to
adjudicate it as bankrupt or insolvent, or seeking liquidation, winding up,
reorganization, arrangement, adjustment, protection, relief or composition of it
or its debts under any law relating to bankruptcy, insolvency, or reorganization
or relief of debtors, or seeking an entry of any order for relief or the
appointment of a receiver, trustee or other similar official for it for any
substantial part of its property or if it shall take any action to authorize any
of the foregoing actions (each "Proceeding"), EpiGenix shall have the right to
retain and enforce its rights under this Agreement, including, but not limited
to the right to a complete duplicate of (or complete access to, as appropriate)
all Licensed Patents, Licensed Technology, and Microcide Joint Technology, if
not already in EpiGenix's possession, which shall be promptly delivered to
EpiGenix upon any such commencement of a Proceeding upon written request
therefore by EpiGenix, unless Microcide elects to continue to perform all of its
obligations under this Agreement; or if not otherwise delivered upon rejection
of this Agreement by or on behalf of Microcide upon written request therefore by
EpiGenix.

10.4 Bankruptcy of EpiGenix. All rights and licenses granted under or pursuant
to this Agreement by EpiGenix to Microcide in respect of EpiGenix Technology,
Assigned Technology, and EpiGenix Joint Technology are and shall otherwise be
deemed to be, for purposes of Section 365(n) of the Bankruptcy Code, licenses of
rights to "Intellectual Property" as defined under Section 101(57) of the
Bankruptcy Code. The parties agree that Microcide, as licensee of such rights
and licenses, shall retain and may fully exercise all of its rights and
elections under the Bankruptcy Code. The parties further agree that, in the
event that any Proceeding shall be instituted by or against EpiGenix, Microcide
shall have the right to retain and enforce its rights under this Agreement,
including, but not limited to the right to a complete duplicate of (or complete
access to, as appropriate) all EpiGenix Technology, Assigned Technology, and
EpiGenix Joint Technology, if not already in Microcide's possession, which shall
be promptly delivered to Microcide upon any such commencement of a Proceeding
upon written request therefore by Microcide, unless EpiGenix elects to continue
to perform all of its obligations under this Agreement; or if not otherwise
delivered upon rejection of this Agreement by or on behalf of EpiGenix upon
written request therefore by Microcide.

10.5 Effect of Termination. Termination or expiration of this Agreement shall
not release any party hereto from any liability which, at the time of such
termination or expiration, has already accrued to the other party, or which is
attributable to such termination or expiration, nor shall it preclude either
party from pursuing all rights and remedies it may have hereunder or at law or
in equity with respect to any breach of this Agreement. Termination of this
Agreement pursuant to Section 10.2 shall not affect any rights or licenses
granted to the non-breaching party, which shall survive any such termination.
Breach of this Agreement shall constitute a breach of the Stock Purchase
Agreement.

SECTION 11:  MISCELLANEOUS PROVISIONS

11.1 Relationship of Parties. It is understood and agreed that both parties
hereto are independent contractors and are engaged in the operation of its own
respective businesses, and 


                                      -14-


   15
neither party hereto is to be considered the agent or partner of the other party
for any purpose whatsoever. Neither party has any authority to enter into any
contracts or assume any obligations for the other party or make any warranties
or representations on behalf of the other party.

11.2 Survival. The provisions of Sections 1, 2, 4 (as stated), 5, 6, 7, 8, 9,
10.5, and 11 shall survive termination or expiration of this Agreement. In the
event that this Agreement is terminated by EpiGenix pursuant to Section 10.2,
then the provisions of Section 4.1 shall not survive the termination of this
Agreement. In the event that this Agreement is terminated by Microcide pursuant
to Section 10.2, then the provisions of Section 4.2 shall not survive the
termination of this Agreement.

11.3 Entire Agreement. This Agreement sets forth the entire agreement and
understanding between the parties and supersedes all previous agreements,
promises, representations, understandings, and negotiations, whether written or
oral between the parties with respect to the subject matter hereof. There shall
be no amendments or modifications to this Agreement, except by a written
document signed by both parties.

11.4 Assignment. Subject to the express provisions regarding the effects of
Change in Control, this Agreement shall not be assigned by either party without
the prior written consent of the other party, except as part of a sale or
transfer, by way of merger or otherwise, of all or substantially all of the
business assets of such party to which this Agreement relates, and provided
further that the assignee agrees to be bound in writing by all the terms of this
Agreement in place of the assignor, or the assignor agrees to remain responsible
for the obligations of the assignee pursuant to the terms set forth herein.

11.5 Binding Upon Successors and Assigns. This Agreement shall be binding upon
and inure to the benefit of successors in interest and assigns of Microcide and
EpiGenix subject to the limitations on assignment.

11.6 Governing Law; Disputes and Alternative Dispute Resolution. This Agreement
shall be construed and enforced in accordance with the laws of the State of
California, without giving effect to its principles of conflicts of law. Any
dispute or claim arising out of or in connection with this Agreement (unless
otherwise set forth herein) shall be resolved in accordance with the provisions
set forth herein and attached as Exhibit C attached hereto.

11.7 Severability. If any provision of this Agreement is finally held to be
invalid, illegal or unenforceable by a court or agency of competent
jurisdiction, that provision shall be severed or shall be modified by the
parties so as to be legally enforceable (and to the extent modified, it shall be
modified so as to reflect, to the extent possible, the intent of the parties)
and the validity, legality and enforceability of the remaining provisions shall
not be affected or impaired in any way.

11.8 No Waiver. Any delay in enforcing a party's rights under this Agreement or
any waiver as to a particular default or other matter shall not constitute a
waiver of a party's right to the future enforcement of its rights under this
Agreement.


                                      -15-


   16
11.9 Attorney's Fees. In the event of a dispute under this Agreement between the
parties, or in the event of any default, the party prevailing in the resolution
of any such dispute or default shall be entitled to request a recovery of its
attorneys' fees and other costs. 

11.10 Notices. Any notice required or permitted by this Agreement to be given to
either party shall be in writing and shall be deemed given when delivered
personally, by confirmed telecopy to a fax number designated in writing by the
party to whom notice is given, or by registered, recorded or certified mail,
return receipt requested, and addressed to the party to whom such notice is
directed, at:

If to Microcide:  Microcide Pharmaceuticals, Inc.
                  850 Maude Avenue
                  Mt. View, CA  94043
                  Telephone: 650-428-3525
                  Facsimile: 650-428-3534
                  Attention: President and CEO

with a copy to:   Michael O'Donnell, Esq.
                  Wilson, Sonsini, Goodrich & Rosati
                  650 Page Mill Road
                  Palo Alto, CA  94304
                  Telephone: 415-493-9300
                  Facsimile: 415-493-6811

If to EpiGenix:   EpiGenix, Inc.                     cc: Joshua Green, Esq.
                  _______________________________    Venture Law Group
                  _______________________________    2800 Sand Hill Road
                  Telephone:_____________________    Menlo Park, CA 94025
                  Fax:___________________________    Telephone: 415-854-4488
                  Attention:_____________________    Fax: 415-854-1121

or at such other address or telecopy number as such party to whom notice is
directed may designate to the other party in writing.

11.11 Public Announcements. The parties will cooperate to create appropriate
public announcements of the relationship set forth in this Agreement. Neither
party shall make any public announcement regarding the existence or content of
this Agreement without the other party's prior written approval and consent.

11.12 Force Majeure. If the performance of this Agreement or any obligations
hereunder is prevented, restricted or interfered with by reason of fire or other
casualty or accident, strikes or labor disputes, war or other violence, any law,
order, proclamation, ordinance, demand or requirement of any government agency,
or any other act or condition beyond the control of the parties hereto, the
party so affected, upon giving prompt notice to the other party shall be 


                                      -16-


   17
excused from such performance (other than the obligation to pay money) during
such prevention, restriction or interference.

11.13 Counterparts. This Agreement shall be fully executed in two (2) original
counterparts, each of which shall be deemed an original.


                            [Signature page follows.]


                                      -17-


   18
         IN WITNESS WHEREOF, authorized officers of each of EpiGenix and
Microcide have executed this Agreement as of the date first set forth above.

MICROCIDE                            EPIGENIX, INC.
PHARMACEUTICALS, INC.



By:  [SIG]                          By:  [SIG]
   -------------------------------     -------------------------------
         Name:                               Name:
               -------------------                --------------------
         Title:                              Title:
               -------------------                --------------------

Date:                                        Date:
     -----------------------------                --------------------


                                      -18-


   19
                                    EXHIBIT A
                               ASSIGNED TECHNOLOGY

             (TO BE COMPLETED PRIOR TO EXECUTION OF THIS AGREEMENT.)

1.   INTELLECTUAL PROPERTY

1.1. PATENT APPLICATIONS

     [*]

1.2. SURROGATE GENETICS TECHNOLOGY

     [*]

1.3. INFORMATICS TECHNOLOGY

     [*]

1.4. LABORATORY NOTEBOOKS AND OTHER WRITTEN MATERIALS

     1.4.1.   Microcide Notebook [ * ]
     1.4.2.   Microcide Notebook [ * ]
     1.4.3.   Microcide Notebook [ * ]
     1.4.4.   Microcide Notebook [ * ]
     1.4.5.   Microcide Notebook [ * ]
     1.4.6.   Microcide Notebook [ * ]
     1.4.7.   Microcide Notebook [ * ]
     1.4.8.   Microcide Notebook [ * ]
     1.4.9.   Microcide Notebook [ * ]
     1.4.10.  Microcide Notebook [ * ]
     1.4.11.  Microcide Notebook [ * ]
     1.4.12.  Microcide Notebook [ * ]
     1.4.13.  Microcide Notebook [ * ]
     1.4.14.  Microcide Notebook [ * ]
     1.4.15.  Microcide Notebook [ * ]
     1.4.16.  Other notes and written information from [ * ]
     1.4.17.  Business Plan and earlier drafts dated 11/18/97

1.5. CONTRACTS AND COLLABORATIVE AGREEMENTS

     1.5.1.   Collaborative agreement between [ * ] and Microcide 
              Pharmaceuticals, Inc.
     1.5.2.   Intranet development contract between Vivid Studios and Microcide
              Pharmaceuticals, Inc.
     1.5.3.   Intellectual property resulting from Genetics Consulting
              Board/Scientific Advisory Board Agreements with [ * ] pertaining
              to the human genetics program.

     [*]


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* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.
   20

                                    EXHIBIT B

                                LICENSED PATENTS

[ * ]







- -------

* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.
   21
                                    EXHIBIT C

                    ALTERNATIVE DISPUTE RESOLUTION MECHANISM


1.       Mediation

         In the event of any dispute or claim arising out of or related to this
Agreement, the parties will attempt in good faith to resolve such dispute or
claim by mediation in San Jose, California, in accordance with the American
Arbitration Association Commercial Mediation Rules. The mediation shall be held
within thirty (30) days of the end of the fifteen day negotiation period.
Nothing herein, however, shall prohibit either party from initiating arbitration
proceedings if such party would be substantially prejudiced by a failure to act
during the time that such good faith efforts are being made to resolve the
dispute or claim through negotiation or mediation. The cost of mediation shall
be shared equally by the parties to the mediation. Any settlement reached by
mediation shall be reduced to writing, signed by the parties, and shall be
binding on them.

2.       Arbitration

         Any dispute or claim arising out of or related to this Agreement, or
the interpretation, making, performance, breach, validity or termination
thereof, which has not been resolved by negotiation or mediation as set forth
above, shall be finally settled by binding arbitration in San Jose, California,
under the Commercial Arbitration Rules and the Supplementary Procedures for
Large Complex Disputes of the American Arbitration Association (together with
"AAA Rules") by one arbitrator appointed in accordance with the AAA Rules.

         This Agreement shall be governed by the law of the state of California.
The arbitrator shall apply California law to the merits of any dispute or claim,
without reference to rules of conflict of law. The arbitrator shall have the
power to decide all questions of arbitrability. The arbitration proceedings
shall be governed by federal arbitration law and by the AAA Rules, without
reference to state arbitration law. At the request of either party, the
arbitrator will enter an appropriate protective order to maintain the
confidentiality of information produced or exchanged in the course of the
arbitration proceedings. Judgment on the award rendered by the arbitrator may be
entered in any court having jurisdiction thereof.

         The parties may apply to any court of competent jurisdiction for a
temporary restraining order, preliminary injunction, or other interim or
conservatory relief, as necessary, without breach of this arbitration agreement
and without any abridgment of the powers of the arbitrator.

         The arbitrator may award to the prevailing party, if any, as determined
by the arbitrator, all of its costs and fees, including, without limitation, AAA
administrative fees, arbitrator fees, travel expenses, out-of-pocket expenses
(including, without limitation, such expenses as copying, telephone, facsimile,
postage, and courier fees), witness fees, and reasonable attorneys' fees.


                                       -i-


   22

                                    EXHIBIT D

                                 1998 WORK PLAN




[ * ]




- -------

* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.
   23
                                    EXHIBIT E

                                   ASSIGNMENT


     THIS ASSIGNMENT, is by and between MICROCIDE PHARMACEUTICALS, INC.
("Assignor"), a corporation duly organized under and pursuant to the laws of
Delaware, and having a principal place of business at 850 Maude Ave., Mt. View,
CA 94043, and ICONIX PHARMACEUTICALS, INC., a corporation duly organized under
and pursuant to the laws of Delaware, and having a principal place of business
at 850 Maude Ave., Mt. View, CA 94043 ("Assignee").

     WHEREAS, Assignor is desirous of assigning all of its right, title, and
interest in and the issued patents, pending patent applications, and invention
disclosures listed in Schedule A attached hereto, including any U.S. or foreign
patents that issue thereon (the "Patents") to Assignee; and

     WHEREAS, Assignee is desirous of acquiring the entire right, title and
interest in and to said Patents;

     NOW THEREFORE, in consideration of good and sufficient considerations, the
receipt of which is hereby acknowledged, said Assignor has sold, assigned,
transferred and set over, and by these presents does sell, assign, transfer and
set over, to Assignee, its successors, legal representatives and assigns, the
entire right, title and interest in and to the above-referenced Patents, and any
and all Letters Patent or Patents in the United States of America and all
foreign countries which may be granted therefor and thereon, and in and to any
and all divisions, continuations, and continuations-in-part of said application,
and reissues and extensions of said Patents, and all rights under the
International Convention for the Protection of Industrial Property, the same to
be held and enjoyed by said Assignee, for its own use and behoof and the use and
behoof of its successors, legal representatives and assigns, to the full end of
the term or terms for which Patents may be granted, as fully and entirely as the
same would have been held and enjoyed by the Assignor, had this sale and
assignment not been made.

     AND for the same consideration, said Assignor hereby covenants and agrees
to and with said Assignee, its successors, legal representatives and assigns,
that, at the time of execution and delivery of these presents, said Assignor is
the sole and lawful owner of the entire right, title and interest in and to the
above-referenced Patents, and that the same are encumbered and that said
Assignor has good and full right and lawful authority to sell and convey the
same in the manner herein set forth.

     AND for the same consideration, said Assignor hereby covenants and agrees
to and with said Assignee, its successors, legal representatives and assigns,
that said Assignor will, whenever counsel of the said Assignee, or the counsel
of its successors, legal representatives and assigns, shall advise that any
proceeding in connection with said Patents in any country, including
interference proceedings, is lawful and desirable, or that any division,
continuation or continuation-in-part of any application for Patent, or any
reissue or extension of any Patent, to be obtained thereon, is lawful and
desirable, sign all papers and documents, take all lawful oaths, and do all acts
necessary or required to be done for the procurement, maintenance, enforcement
and defense of such Patents, without charge to said Assignee, its successors,
legal representatives and assigns, but at the cost and expense of said Assignee,
its successors, legal representatives and assigns.

     AND said Assignor hereby requests the Commissioner of Patents to issue said
Patents of the United States to said Assignee as the Assignee of said inventions
and the Patents to be issued thereon for the sole use and behoof of said
Assignee, its successors, legal representatives and assigns.

Date:  January 14, 1998            Assignor:  /s/ James E. Rurka
                                             -----------------------------

                                   By:       James E. Rurka
                                             -----------------------------
                                             (Name)       

                                   Its:      President & CEO
                                             -----------------------------
                                             (Title) 
                                           
   24
                                    EXHIBIT F

                                   DEFINITIONS


The MOLECULAR DIVERSITY CORE TECHNOLOGY AREA includes work related to
maintaining and continuing the expansion of the synthetic compound and the
natural products library and follow-up work on screening hits identified from
the libraries. [ * ]

The HIGH THROUGHPUT SCREENING CORE TECHNOLOGY AREA includes work related to
both the enabling and the actual task of high throughput screening. [ * ]

The INFORMATICS CORE TECHNOLOGY AREA includes work related to computational
support for research programs and corporate administration. [ * ]

The GENOME SCIENCES CORE TECHNOLOGY AREA includes work related to the [ * ]


* Certain information on this page has been omitted and filed separately with
  the Commission. Confidential treatment has been requested with respect to the
  omitted portions.