Document:

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                                                                    Exhibit 10.3

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                       PREFERRED STOCK PURCHASE AGREEMENT
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                         NEOGENESIS DRUG DISCOVERY INC.
            Up to $30,000,000 of Series D Convertible Preferred Stock

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                             Dated December 27, 2000

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

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                                TABLE OF CONTENTS
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ARTICLE 1. PURCHASE AND SALE OF SERIES D PREFERRED STOCK..........................................................1

                1.1      Authorization............................................................................1
                1.2      Closing .................................................................................1
                1.3      Use of Proceeds..........................................................................2

ARTICLE 2. THE COMPANY'S REPRESENTATIONS AND WARRANTIES...........................................................2

                2.1      Incorporation, Standing and Qualification of the Company.................................2
                2.2      Subsidiaries.............................................................................2
                2.3      Corporate Power and Authority............................................................2
                2.4      Certificate of Incorporation and By-Laws.................................................3
                2.5      Litigation; Compliance with Laws; Bankruptcy.............................................3
                2.6      Burdensome and Conflicting Agreements; Violations of Certificates of Incorporation
                           Provisions.............................................................................4
                2.7      Material Agreements......................................................................4
                2.8      Governmental Approvals...................................................................4
                2.9      Tax Returns and Payments.................................................................5
                2.10     Issuance Taxes...........................................................................5
                2.11     ERISA....................................................................................5
                2.12     Title to Assets..........................................................................5
                2.13     Intellectual Property Rights.............................................................5
                2.14     Proprietary Information of Third Parties.................................................6
                2.15     Capitalization; Status of Capital Stock..................................................6
                2.16     Financial Statements.....................................................................8
                2.17     Securities Laws..........................................................................8
                2.18     Insurance................................................................................9
                2.19     Registration Rights......................................................................9
                2.20     No Broker................................................................................9
                2.21     Transactions with Affiliates.............................................................9
                2.22     Employees................................................................................9
                2.23     Labor Relations..........................................................................9
                2.24     Assumptions or Guaranties of Indebtedness of other Persons...............................9
                2.25     Loans and Advances......................................................................10
                2.26     Disclosure..............................................................................10
                2.27     Books and Records.......................................................................10
                2.28     Foreign Corrupt Practices Act...........................................................11
                2.29     U.S. Real Property Holding Corporation..................................................11
                2.30     Environmental Matters...................................................................11
                2.31     Absence of Certain Developments.........................................................12
                2.32     Operating Company Status................................................................13

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       ii

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ARTICLE 3.     THE PURCHASERS' REPRESENTATIONS AND WARRANTIES....................................................13

                3.1      Investment Representations..............................................................13
                3.2      Access to Information...................................................................14
                3.3      Accredited Investor Status..............................................................14
                3.4      Transfer Restrictions Imposed By Securities Laws........................................14

ARTICLE 4. CLOSING CONDITIONS....................................................................................14

                4.1      Conditions to the Purchasers' Obligations...............................................14
                4.2      Conditions to the Company's Obligations.................................................16

ARTICLE 5. INDEMNIFICATION.......................................................................................16

                5.1      Company Indemnification.................................................................16
                5.2      Purchasers' Indemnification.............................................................17

ARTICLE 6. DEFINITIONS...........................................................................................17

                6.1      Definitions.............................................................................17
                6.2      Accounting Principles...................................................................19
                6.3      "Directly or Indirectly"................................................................20

ARTICLE 7. MISCELLANEOUS.........................................................................................20

                7.1      Notices.................................................................................20
                7.2      Entire Agreement........................................................................21
                7.3      Modifications and Amendments............................................................21
                7.4      Waivers and Consents....................................................................21
                7.5      Binding Effect, Assignment..............................................................21
                7.6      Governing Law...........................................................................21
                7.7      Severability............................................................................21
                7.8      Interpretation..........................................................................22
                7.9      Headings and Captions...................................................................22
                7.10     No Waiver of Rights, Powers and Remedies................................................22
                7.11     Reliance................................................................................22
                7.12     Survival................................................................................22
                7.13     Further Assurances......................................................................22
                7.14     Costs, Expenses, and Taxes..............................................................23
                7.15     Counterparts............................................................................23
                7.16     Use of Definitions; Gender..............................................................23
                7.17     Jurisdiction and Service of Process.....................................................23
                7.18     Publicity...............................................................................23
                7.19     Brokers or Finders......................................................................23
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* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       iii

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                                    EXHIBITS

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EXHIBIT A          Purchasers

EXHIBIT B          Second Amended and Restated Certificate of Incorporation

EXHIBIT C-1        Form of Invention and Non-Disclosure Agreement

EXHIBIT C-2        Form of Non-Competition and Non-Solicitation Agreement

EXHIBIT D          Form of Opinion of Company Counsel

EXHIBIT E          Form of Investor Rights Agreement

EXHIBIT F          Form of Right of First Refusal, Co-Sale and Waiver Agreement
</Table>

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       iv

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                                    SCHEDULES

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SCHEDULE 2.1       Foreign Qualifications

SCHEDULE 2.7       Material Agreements

SCHEDULE 2.12      Title to Assets

SCHEDULE 2.13      Intellectual Property Rights

SCHEDULE 2.15      Capitalization

SCHEDULE 2.16      Listed Liabilities

SCHEDULE 2.19      Registration Rights

SCHEDULE 2.21      Transactions with Affiliates

SCHEDULE 2.22      Employees

SCHEDULE 2.25      Loans and Advances
</Table>

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

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                       PREFERRED STOCK PURCHASE AGREEMENT

                  THIS PREFERRED STOCK PURCHASE AGREEMENT (this "AGREEMENT") is
made as of December 27, 2000 by and among NeoGenesis Drug Discovery, Inc., a
corporation organized under the laws of Delaware (the "COMPANY") and the Persons
listed on EXHIBIT A hereto (individually, a "PURCHASER" and collectively, the
"PURCHASERS").

                  WHEREAS, the Company desires to issue and sell to the
Purchasers and the Purchasers desire to acquire on the terms and subject to the
conditions set forth in this Agreement up to an aggregate amount of Four Million
Six Hundred Twenty Three Thousand Four Hundred Eighty-Seven (4,623,487) shares
of the Company's Series D Convertible Preferred Stock, par value $0.001 per
share (the "SERIES D PREFERRED STOCK"); and

                  WHEREAS, the Company has sold (i) 1,250,000 shares of Series A
Convertible Preferred Stock, par value $0.001 per share (the "SERIES A PREFERRED
STOCK"; the holders of the Series A Preferred Stock being referred to herein as
the "SERIES A PURCHASERS"); (ii) 530,205 shares of Series B Convertible
Preferred Stock, par value $0.001 per share (the "SERIES B PREFERRED STOCK"; the
holders of the Series B Preferred Stock being referred to herein as the "SERIES
B PURCHASERS"); and (iii) 4,241,055 shares of Series C Convertible Preferred
Stock, par value $0.001 per share (the "SERIES C PREFERRED STOCK"; the holders
of the Series C Preferred Stock being referred to herein as the "SERIES C
PURCHASERS").

                  NOW, THEREFORE, in consideration of the premises and the
mutual covenants contained in this Agreement, the parties hereto agree as
follows:

                                   ARTICLE 1.

                  PURCHASE AND SALE OF SERIES D PREFERRED STOCK

     1.1.  AUTHORIZATION OF SERIES D PREFERRED STOCK. The Company has, or before
the Closing (as hereinafter defined) will have, authorized the issuance and sale
of up to Four Million Six Hundred Twenty Three Thousand Four Hundred
Eighty-Seven (4,623,487) shares (the "SHARES") of its Series D Preferred Stock,
having the rights, restrictions, privileges and preferences as set forth in the
Second Amended and Restated Certificate of Incorporation attached to this
Agreement as EXHIBIT B.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

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     1.2.  CLOSING. Subject to the terms and conditions set forth in this
Agreement, and in reliance on the representations and warranties set forth in
this Agreement, the Company agrees to issue and sell to the Purchasers at the
Closing (as hereinafter defined) and the Purchasers, severally but not jointly,
agree to purchase from the Company, that number of Shares set forth opposite
their respective names on EXHIBIT A under the caption "NUMBER OF SERIES D
SHARES" at a purchase price per Share of Four Dollars and Ninety-Seven and
Forty-Six One-Hundredths Cents ($4.9746). The total purchase price of the Shares
being acquired by each Purchaser is set forth opposite such Purchaser's name on
EXHIBIT A. The closing of the purchase and sale of the Shares (the "CLOSING")
shall take place at the offices of Wollmuth Maher & Deutsch LLP, 500 Fifth
Avenue, New York, New York at 10:00 on December 27, 2000 (the "CLOSING DATE") or
at such time and date thereafter as the Purchasers and the Company may agree. At
the Closing, the Company will deliver to each Purchaser certificates for the
number of Shares being purchased by such Purchaser registered in such
Purchaser's name (or its nominee), against delivery of a check or checks payable
to the order of the Company, or a transfer of funds to the account of the
Company by wire transfer, representing the purchase price set forth opposite
each such Purchaser's name on EXHIBIT A.

     1.3.  USE OF PROCEEDS. The Company agrees to use the net proceeds from the
sale of the Shares solely: (i) for working capital; (ii) to fund costs of
organizational development; and (iii) as otherwise approved by the Company's
Board of Directors.

                                   ARTICLE 2.

                  THE COMPANY'S REPRESENTATIONS AND WARRANTIES

                  In order to induce the Purchasers to enter into this Agreement
and to consummate the transactions contemplated hereby, the Company represents
and warrants as of the date hereof and as of the Closing as follows:

     2.1   INCORPORATION, STANDING AND QUALIFICATION OF THE COMPANY. The Company
is a corporation duly incorporated, validly existing and in good standing under
the laws of its jurisdiction of organization. The Company has requisite power
and authority to own, lease and operate its properties and to carry on its
business as now being conducted and as proposed to be conducted. The Company is
qualified as a foreign corporation and in good standing in the states listed on
SCHEDULE 2, except for such jurisdiction where the failure to do so qualify
would not have a material adverse impact on the Company. Except as set forth on
SCHEDULE 2.1, the nature of the Company's business and the ownership or lease of
its property do not require it to become qualified as a foreign corporation in
any other state or jurisdiction.

     2.2   SUBSIDIARIES. The Company does not (i) own of record or beneficially,
directly or indirectly, (A) any shares of capital stock of any other corporation
or (B) any participating interest in any partnership, joint venture or other
non-corporate business enterprise, or (ii) control, directly or indirectly, any
other entity.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       2

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     2.3   CORPORATE POWER AND AUTHORITY. The Company has the requisite power
and authority to execute and deliver this Agreement, the Shares, and the other
agreements and certificates contemplated hereby to which it is a party,
including the Investor Rights Agreement and the Right of First Refusal and
Co-Sale Agreement (collectively, the "RELATED AGREEMENTS"), to perform its
obligations hereunder and thereunder and to engage in the transactions
contemplated hereby and thereby. The Company has taken all requisite corporate
action to make all the provisions of this Agreement, the Shares and the Related
Agreements the valid and enforceable obligations they purport to be. This
Agreement is, and upon the execution and delivery thereof, the Shares and each
of the Related Agreements will be, legal, valid and binding obligations of the
Company, enforceable in accordance with their terms, subject to laws of general
application from time to time in effect that have an affect on creditors' rights
and the exercise of judicial discretion in accordance with general equitable
principles.

     2.4   CERTIFICATE OF INCORPORATION AND BY-LAWS. The Company has made
available to each of the Purchasers true, correct and complete copies of its
Second Amended and Restated Certificate of Incorporation and By-Laws, and all
amendments to and restatements of each as of the date hereof. Prior to the
Closing, the Company shall have properly filed amendments to the Second Amended
and Restated Certificate of Incorporation to permit the Company to fulfill its
obligations under this Agreement.

     2.5   LITIGATION; COMPLIANCE WITH LAWS; BANKRUPTCY.

           (a) LITIGATION. There is no action, suit, claim, litigation,
proceeding, investigation, arbitration or governmental inquiry, at law or in
equity, or before or by any Federal, state, municipal or other governmental
department, commission, board, bureau, agency or instrumentality, domestic or
foreign, or arbitration involving private parties (collectively, a "PROCEEDING")
pending or, to the best knowledge of the Company, threatened against the Company
or affecting any of its properties or assets, or, to the best knowledge of the
Company, against any officer, employee, consultant or holder of any of the
capital stock of the Company relating to the Company or its business, nor, to
the best knowledge of the Company, has there occurred any event nor does there
exist any condition on the basis of which it is reasonably likely that any such
Proceeding might properly be instituted. There are no Proceedings pending or, to
the Company's knowledge, threatened (or any basis therefor known to the Company)
which might call into question the validity of this Agreement, any of the
Shares, any of the Related Agreements or any action taken or to be taken
pursuant hereto or thereto. There is no Proceeding by the Company pending or
threatened against others.

           (b) COMPLIANCE WITH LAWS. The Company has complied with, and is not
in violation of or in default (with due notice or lapse of time or both) with
respect to, all laws, governmental rules, governmental regulations, governmental
orders, judgments, decrees, writs, injunctions and awards of any arbitration,
court or governmental authority applicable to it and its business, operations,
properties, assets, products and services, the violation or default of which
would have a material adverse impact on the Company, and the Company has all
necessary permits, licenses and other authorizations required to conduct its
business as currently conducted and as proposed to be conducted. There is no
existing law, governmental rule, governmental regulation or governmental order
applicable to or binding upon the Company, and the Company is not aware of any
proposed law, governmental rule, governmental regulation or governmental order,
whether Federal or state, which would prohibit or materially restrict the
Company from, or otherwise materially adversely affect the Company in,
conducting its business in any jurisdiction in which it is now conducting
business or has proposed to conduct business.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       3

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           (c) BANKRUPTCY. The Company has not admitted in writing its inability
to pay its debts generally as they become due, filed or consented to the filing
against it of a petition in bankruptcy or a petition to take advantage of any
insolvency act, made an assignment for the benefit of creditors, consented to
the appointment of a receiver for itself or for the whole or any substantial
part of its property, or had a petition in bankruptcy filed against it, been
adjudicated a bankrupt, or filed a petition or answer seeking reorganization or
arrangement under the Federal bankruptcy laws or any other law or statute of the
United States of America or any other jurisdiction.

     2.6   BURDENSOME AND CONFLICTING AGREEMENTS; VIOLATIONS OF CERTIFICATE OF
INCORPORATION PROVISIONS. The Company is not bound by any agreement or
instrument or subject to any Certificate of Incorporation or other corporate
restriction which materially and adversely affects the business, properties,
operations, condition or prospects, financial or otherwise of the Company. The
Company is not in violation or default (with due notice or lapse of time or
both) of its Certificate of Incorporation, By-laws or other corporate
restriction, or of any agreement or instrument to which it is a party or by
which it or any of its assets is bound, except for violations or defaults of any
agreement or instrument other than the Certificate of Incorporation or By-laws,
which, individually or in the aggregate, would not materially adversely affect
the business, properties, operations or condition, financial or otherwise, of
the Company. Neither the authorization, execution, delivery and performance of
this Agreement or the Related Agreements, nor the sale, issuance and delivery of
the Shares, nor the consummation of the transactions herein and therein
contemplated, nor the fulfillment of or compliance with the terms hereof and
thereof, will conflict with or result in a breach or default (with due notice or
lapse of time or both) of any of the terms of the Certificate of Incorporation
or By-laws or any other corporate restriction, or of any statute, law, rule or
regulation, or of any judgment, decree, writ, injunction, order or award of any
arbitrator, court or governmental authority, or of any agreement or instrument,
which is applicable to the Company or by which the Company or any of its assets
is bound, or constitute a default (with due notice or lapse of time or both)
thereunder, or result in the creation or imposition of any Lien upon any of the
assets of the Company.

     2.7   MATERIAL AGREEMENTS. Except as set forth in SCHEDULE 2.7, the Company
is not a party to any material written or oral contract, instrument, agreement,
commitment, obligation, plan or arrangement, or any other material agreement
which involve obligations of, or payments to, the Company in excess of $50,000
or which are otherwise strategic or scientific in nature (the "MATERIAL
AGREEMENTS"). Each of the Material Agreements is in full force and effect with
no default (without regard to notice or lapse of time or both) by the Company
or, to the best knowledge of the Company, by any other party thereto. There is
no threatened default or material failure of performance or observance of any
obligations or conditions contained in the Material Agreements by the Company,
or, to the best knowledge of the Company, by any other party thereto, and none
of the foregoing parties nor the Company has provided any notice of default or
of its intention to terminate these agreements.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       4

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     2.8   GOVERNMENTAL APPROVALS. Subject to the accuracy of the
representations and warranties of the Purchasers set forth in Article 3, no
registration or filing with, or consent or approval of or other action by, any
Federal, state or other governmental agency or instrumentality, domestic or
foreign, under laws and regulations thereof as now in effect is or will be
necessary for the valid execution, delivery and performance by the Company of
this Agreement, or any of the Related Agreements, the issuance, sale and
delivery of the Shares and the Conversion Shares, other than (i) filings
pursuant to federal and state securities laws (all of which filings have been
made by the Company or will be made within the period of time required by such
state securities laws) in connection with the sale of the Shares and (ii) with
respect to the Investor Rights Agreement, the registration of the shares covered
thereby with the Commission and filings pursuant to state securities laws, and
any other registration or filing, or consent or approval or other action as a
result of or associated with any purchase or sale of securities in accordance
therewith.

     2.9   TAX RETURNS AND PAYMENTS. The Company has accurately prepared and
timely filed all required tax returns and reports (other than those not required
to be filed by applicable law or regulation) and has paid, or adequately
provided for the payment of, all taxes, assessments and other governmental
charges imposed upon it or upon any of its assets, income or franchises, other
than any such charges that are currently payable without penalty or interest,
including, without limitation, all taxes which the Company is obligated to
withhold from amounts owing to employees, creditors and third parties. Adequate
reserves have been established for all taxes accrued but not yet payable. The
Federal income tax returns of the Company have never been audited by the
Internal Revenue Service or other taxing authority, domestic or foreign. No
deficiency assessment with respect to or proposed adjustment of the Company's
Federal, state, county or local taxes, domestic or foreign, is pending or, to
the Company's knowledge threatened. There is no tax lien, whether imposed by any
Federal, state, county or local taxing authority, outstanding against the
assets, properties or business of the Company.

     2.10  ISSUANCE TAXES. All taxes imposed by law in connection with the
issuance, sale and delivery of the Shares have been fully paid, and all laws
imposing such taxes have been fully complied with.

     2.11  ERISA. The Company does not make nor has it any present intention of
making any contributions to any employee pension benefit plans for its employees
which are or would be subject to the Employee Retirement Income Security Act of
1974, as amended.

     2.12  TITLE TO ASSETS. The Company has good and marketable title in fee to
its real property and good and merchantable title to all of its assets free of
any Liens except (i) mechanics liens not material to the Company or any property
to which such liens relate or liens for current taxes not yet due and payable,
and (ii) those encumbrances listed on SCHEDULE 2.12 hereto. The Company enjoys
peaceful and undisturbed possession under all leases (both capital and operating
leases) under which it is operating, and all said leases are valid and
subsisting and in full force and effect.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       5

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     2.13  INTELLECTUAL PROPERTY RIGHTS. The Company owns or has a valid right
to use the Intellectual Property Rights being used and proposed to be used to
conduct its business (i) as now conducted and (ii) as now proposed to be
conducted. A complete list of licenses, contract rights and registrations of
such Intellectual Property Rights is attached hereto as SCHEDULE 2.13. The
conduct of the Company's business as now operated and as now proposed to be
operated does not conflict with or infringe upon the Intellectual Property
Rights of others. Except as specified on SCHEDULE 2.13, the Company has no
obligation to compensate any Person for the use of any such Intellectual
Property Rights and the Company has not granted to or assigned to any Person any
license or other right to use any of the Intellectual Property Rights of the
Company or otherwise licensed from others the Intellectual Property Rights of
third parties, whether requiring the payment of royalties or not.

     The Company has taken all reasonable measures to protect and preserve the
security, confidentiality and value of its Intellectual Property Rights,
including its trade secrets and other confidential information. All employees
and consultants of the Company have executed the Company's standard form of
Invention and Non-Disclosure Agreement in the form attached hereto as EXHIBIT
C-1 and the Company's standard form of Non-Competition and Non-Solicitation
Agreement in the form of EXHIBIT C-2. To the Company's best knowledge, all trade
secrets and other confidential information of the Company are presently valid
and protectable and are not part of the public domain or knowledge, nor have
they been used, divulged or appropriated for the benefit of any Person other
than the Company or otherwise to the detriment of the Company. The Company is
the exclusive owner of all rights, titles and interests in its Intellectual
Property Rights purported to be owned by the Company, the exclusive licensee of
all rights, titles and interests in Intellectual Property purported to be
exclusively licensed to the Company and a licensee of all rights, titles and
interests in Intellectual Property purported to be licensed to the Company on a
non-exclusive basis, and all such Intellectual Property Rights are valid and in
full force and effect. Neither the Company nor any of its officers, employees or
consultants has received notice of, and there are no claims pending or, to the
Company's best knowledge, threatened that the Intellectual Property Rights owned
or licensed by the Company or the use or ownership thereof by the Company
infringes, violates or conflicts with any such right of any third party or are
invalid or unenforceable.

     2.14  PROPRIETARY INFORMATION OF THIRD PARTIES. To the Company's best
knowledge, no third party has claimed or, to the reasonable knowledge of the
Company, has reason to claim that any Person employed by or affiliated with the
Company has (a) violated or may be violating any of the terms or conditions of
his or her employment, non-competition, nondisclosure or inventions agreement
with such third party, (b) disclosed or may be disclosing or utilized or may be
utilizing any trade secret or proprietary information or documentation of such
third party or (c) interfered or may be interfering in the employment
relationship between such third party and any of its present or former
employees. No third party has requested information from the Company which
suggests that such a claim might be contemplated. To the reasonable knowledge of
the Company, no Person employed by or affiliated with the Company has employed
or proposes to employ any trade secret or any information or documentation
proprietary to any former employer, and to the reasonable knowledge of the
Company no Person employed by or affiliated with the Company has violated any
confidential relationship which such Person may have had with any third party,
in connection with the development, manufacture or sale of any product or
proposed product or the development or sale of any service or proposed service
of the Company, and the Company has no reason to believe there will be any such
employment or violation. To the Company's best knowledge, none of the execution
or delivery of this Agreement or any of the Related Agreements, or the carrying
on of the business of the Company as officers, employees or agents by any
officer, director or key employee of the Company, or the conduct or proposed
conduct of the business of the Company, will conflict with or result in a breach
of the terms, conditions or provisions of or constitute a default under any
non-competition, non-disclosure or inventions agreement under which any such
Person is obligated.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       6

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     2.15  CAPITALIZATION; STATUS OF CAPITAL STOCK. The Company has a total
authorized capitalization consisting of Thirty One Million Three Hundred Thirty
Three Thousand One Hundred Fourteen (31,333,114) shares, of which (i) Twenty
Million Four Hundred Ninety One Thousand Five Hundred Fifty Seven (20,491,557)
shares are designated as Common Stock, and (ii) Ten Million Eight Hundred Forty
One Thousand Five Hundred Fifty Seven (10,841,557) shares are designated as
preferred stock, $.001 par value per share, of which (A) One Million Two Hundred
Fifty Thousand (1,250,000) are designated Series A Convertible Preferred Stock,
(B) Five Hundred Thirty Thousand Two Hundred Five (530,205) are designated
Series B Convertible Preferred Stock, (C) Four Million Four Hundred Thirty Seven
Thousand Eight Hundred Sixty Five (4,437,865) are designated Series C
Convertible Preferred Stock and (D) Four Million Six Hundred Twenty Three
Thousand Four Hundred Eighty Seven (4,623,487) are designated Series D
Convertible Preferred Stock. Immediately prior to the Closing, the issued and
outstanding capital stock of the Company shall consist of 5,053,875 shares of
Common Stock, 1,250,000 shares of Series A Convertible Preferred Stock, 530,205
shares of Series B Convertible Preferred Stock and 4,241,055 shares of Series C
Convertible Preferred Stock. All the outstanding shares of capital stock of the
Company have been duly authorized, are validly issued and are fully paid and
non-assessable and no personal liability will attach to the ownership thereof. A
complete list of the capital stock of the Company which has been previously
issued and the names in which such capital stock is registered on the stock
transfer book of the Company is set forth in SCHEDULE 2.15. As of immediately
prior to the Closing, the designations, powers, preferences, rights,
qualifications, limitations and restrictions in respect of the authorized
capital stock of the Company will be as set forth in the Company's Certificate
of Incorporation, and, all such designations, powers, preferences, rights,
qualifications, limitations and restrictions will be valid, binding and
enforceable and in accordance with all applicable laws. The Shares, when issued
and delivered in accordance with the terms hereof, and the shares of Common
Stock when issued and delivered upon the conversion of the Shares (as adjusted
from time to time in accordance the Certificate of Incorporation, as amended,
the "CONVERSION SHARES"), will be duly authorized, validly issued, fully paid
and non-assessable and no personal liability will attach to the ownership
thereof and will be free and clear of all Liens or restrictions imposed by or
through the Company except as set forth in this Agreement and the Related
Agreements. The Conversion Shares have been duly reserved for issuance.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       7

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     Except for the Shares and as set forth on SCHEDULE 2.15, there are no
subscriptions, options, warrants or other rights (contingent or otherwise) to
purchase or otherwise acquire from the Company any shares of capital stock or
other securities of the Company authorized, issued or outstanding, nor is the
Company obligated in any other manner to issue shares of its capital stock,
subscriptions, warrants, options, convertible securities, or other such rights
or to distribute to holders of any of its equity securities any evidence of
Indebtedness or asset. As of the date hereof, 5,125,000 shares of Common Stock
are authorized for issuance pursuant to the Company's Stock Option Plan (the
"STOCK PLAN"), of which 4,112,750 options to purchase shares have been granted
on the date hereof, of which 3,583,875 are outstanding and unexercised and of
which 528,875 have been exercised into Common Stock. Except as set forth in
SCHEDULE 2.15, or contemplated by this Agreement or the Related Agreements, (i)
there are no restrictions on the transfer of shares of capital stock of the
Company other than those imposed by relevant state and Federal securities laws
and (ii) the Company is not aware of any agreements, understandings, proxies,
trusts or other collaborative arrangements concerning the voting, pledge or
purchase and sale of the capital stock of the Company. Except as set forth in
SCHEDULE 2.15 or the Related Agreements, no holder of any security of the
Company is entitled to preemptive, first refusal or similar statutory or
contractual rights, either arising pursuant to any agreement or instrument to
which the Company is a party, or which are otherwise binding upon the Company,
or to the best of the Company's knowledge, to which any other Person is a party.
Except as provided for in the Second Amended and Restated Certificate of
Incorporation or as set forth in the attached SCHEDULE 2.15, the Company has no
obligation (contingent or otherwise) to purchase, redeem or otherwise acquire
any of its equity securities or any interest therein or to pay any dividend or
make any other distribution in respect thereof. The offer and sale of all
capital stock and other securities of the Company issued before the Closing,
assuming the truth and accuracy of the representations and warranties made by
the purchasers of such stock and other securities, complied with or were exempt
from all applicable Federal and state securities laws and no such stockholder
has a right of rescission or damages with respect thereto.

     2.16  FINANCIAL STATEMENTS. Prior to the Closing, the Company has made
available to each Purchaser its audited financial statements for the years ended
December 31, 1998 and 1999 (the "AUDITED FINANCIAL STATEMENTS") and its
unaudited balance sheets for the quarter ended June 30, 2000 and September 30,
2000 (the "INTERIM FINANCIAL STATEMENTS" and, together with the Audited
Financial Statements, the "FINANCIAL STATEMENTS"). The Financial Statements have
been prepared in accordance with United States generally accepted accounting
principles applied on a consistent basis throughout the periods indicated,
except that the Interim Financial Statements are subject to normal year-end
adjustments (which are not expected to be material) and do not contain all
footnotes required by generally accepted accounting principles. The Financial
Statements fairly present the financial condition and operating results of the
Company as of the dates, and for the periods, indicated therein, subject to
normal year-end audit adjustments with respect to the Interim Financial
Statement which the Company does not expect to be material. Except as set forth
in the September Interim Financial Statement or SCHEDULE 2.16 hereto, the
Company has no material liabilities, contingent or otherwise, other than (i)
liabilities incurred in the ordinary course of business subsequent to the date
of last set of Financial Statements delivered to the Purchasers and (ii)
obligations under contracts and commitments incurred in the ordinary course of
business and not required under generally accepted accounting principles to be
reflected in the Financial Statements, which, in both cases, individually or in
the aggregate are not material to the financial condition or operating results
of the Company. Except as disclosed in the September Interim Financial Statement
or SCHEDULE 2.16 hereto, the Company has no indebtedness, liabilities, notes,
obligations (or series of related obligations), or commitments, of any nature,
absolute, accrued, contingent or otherwise, (hereafter referred to as the
"LISTED LIABILITIES") as of the date of this Agreement.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       8

<Page>

     2.17  SECURITIES LAWS. The Company has in all material respects complied
and will comply with all applicable Federal and state securities laws in
connection with the offer, issuance and sale of the Shares and Conversion Shares
hereunder. Neither the Company nor anyone authorized to act on its behalf has or
will sell, offer to sell or solicit offers to buy the Shares, Conversion Shares,
options or similar securities thereto, or solicit offers with respect thereto
from, or enter into any preliminary conversations or negotiations relating
thereto with, any Person, so as to bring the issuance and sale of the Shares,
Conversion Shares, options or similar securities under the registration
provisions of the Securities Act and applicable state securities laws
(including, without limitation, any offer, other issuance or sale of any
security of the Company under circumstances that might require the integration
of the offering of such security with the offering of the Shares or Conversion
Shares under the Securities Act or the rules and regulations thereunder).

     2.18  INSURANCE. The Company carries insurance with financially sound and
reputable insurance companies or associations, in such amounts and covering such
risks as are adequate and customary for the type and scope of its property and
business, but in any event in amounts sufficient to prevent the Company from
becoming a co-insurer.

     2.19  REGISTRATION RIGHTS. Other than pursuant to the terms of the Investor
Rights Agreement or as set forth on SCHEDULE 2.19 hereto, no Person has demand
or other rights to cause the Company to file any registration statement under
the Securities Act relating to any securities of the Company or any right to
participate in any such registration.

     2.20  NO BROKER. The Company has no contract, arrangement or understanding
with any broker, finder, agent, financial advisor or other intermediary with
respect to the transactions contemplated by this Agreement.

     2.21  TRANSACTIONS WITH AFFILIATES. Except as set forth in SCHEDULE 2.21,
neither the Company, nor to the Company's knowledge, any of the customers and
suppliers of the Company, is a party to or bound by any agreement with any
Affiliate of the Company. All of the agreements identified on SCHEDULE 2.21
hereto were entered into by the Company in good faith and, except as set forth
on SCHEDULE 2.21, are on terms no less favorable to the Company than those which
the Company could have obtained from non-Affiliates.

     2.22  EMPLOYEES. Set forth in SCHEDULE 2.22 is a list of the names of all
employees of the Company, together with the title or job classification of each
such person. Except as set forth in SCHEDULE 2.22, none of such persons has an
employment agreement or understanding, whether oral or written, with the Company
which is not terminable on notice by the Company without cost or other liability
to the Company (except for the Company's requirement to meet certain insurance
benefit obligations under COBRA). Except as set forth in SCHEDULE 2.22, no
employee of the Company has advised the Company (orally or in writing) that he
or she intends to terminate employment with the Company. The Company has
complied in all material respects with all applicable laws, domestic and
foreign, relating to the employment of labor, including provisions relating to
wages, hours, equal opportunity, collective bargaining and the payment of Social
Security and other taxes, and with ERISA.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       9

<Page>

     2.23  LABOR RELATIONS. To the Company's knowledge, no labor union or any
representative thereof has made any attempt to organize or represent employees
of the Company. There are no unfair labor practice charges, pending trials with
respect to unfair labor practice charges, pending grievance proceedings or
adverse decisions of any labor relations board against the Company or relating
to the Company's employees or consultants. The Company is not in violation of
any applicable statute, law or regulation relating to occupational safety and
health. Furthermore, to the best knowledge of the Company, relations with
employees and consultants of the Company are good and there is no reason to
believe that any labor difficulties will arise in the foreseeable future.

     2.24  ASSUMPTIONS OR GUARANTIES OF INDEBTEDNESS OF OTHER PERSONS. The
Company has not assumed, Guaranteed, endorsed or otherwise become directly or
contingently liable on (including, without limitation, liability by way of
agreement, contingent or otherwise, to purchase, to provide funds for payment,
to supply funds to or otherwise invest in any debtor or otherwise to assure any
creditor against loss) any Indebtedness of any other Person.

     2.25  LOANS AND ADVANCES. The Company has not made any loan or advance to
any Person except as set forth on SCHEDULE 2.25 hereto, nor, is the Company
obligated or committed to make any such loan or advance.

     2.26  DISCLOSURE. Neither this Agreement, nor any other agreement, document
or certificate delivered at the Closing by the Company or on behalf of the
Company by any of its officers or agents in connection with the transactions
contemplated hereby, including, without limitation, the Listed Liabilities,
contains any untrue statement of a material fact or omits to state a material
fact necessary in order to make the statements contained herein and therein, in
light of the circumstances under which they were made, not misleading. There is
no fact which materially and adversely affects, or which in the future may (so
far as the Company can reasonably foresee) materially and adversely affect, the
business, properties, operations or condition, financial or otherwise, of the
Company (except for general economic conditions and climate which are beyond the
control of the Company), which has not been set forth in this Agreement,
including the Schedules and Exhibits hereto. Without limiting the foregoing, the
Company does not have knowledge that there exists, or that there is pending or
planned, any patent, invention, device, application or principle or any statute,
rule, law, regulation, standard or code which would materially adversely affect
the business, operations, Intellectual Property Rights, or financial condition
of the Company.

     2.27  BOOKS AND RECORDS. The books of account, ledgers, order books,
records and documents of the Company accurately and completely reflect all
material information relating to the business of the Company, the nature,
acquisition, maintenance, location and collection of the assets of the Company,
and the nature of all transactions giving rise to the obligations or accounts
receivable of the Company.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       10

<Page>

     2.28  FOREIGN CORRUPT PRACTICES ACT. The Company is not engaged, nor has
any officer, director, employee or agent of the Company engaged, in any act or
practice which would constitute a violation of the Foreign Corrupt Practices Act
of 1977, or any rules or regulations promulgated thereunder. There is not now,
and there never has been, any employment by the Company, or beneficial ownership
in the Company by, any governmental or political official in any country in the
world.

     2.29  U.S. REAL PROPERTY HOLDING CORPORATION. The Company is not now nor
has ever been a "United States real property holding corporation", as defined in
Section 897(c)(2) of the Code and Section 1.897-2(b) of the Regulations
promulgated by the Internal Revenue Service.

     2.30  ENVIRONMENTAL MATTERS.

     (a)   The Company is in compliance with all limitations, restrictions,
conditions, standards, prohibitions, requirements, obligations, schedules and
timetables contained in any Applicable Environmental Laws, or in any plan,
order, decree, judgment, notice or demand letter issued, entered, promulgated or
approved thereunder, except to the extent that noncompliance would not have a
material adverse effect on the Company. For purposes of this Agreement, the term
"Applicable Environmental Laws" shall mean Comprehensive Environmental Response,
Compensation and Liability Act of 1980, 42 U.S.C. 9601 ET. SEQ. ("CERCLA");
Resource Conservation and Recovery Act of 1976, 42 U.S.C. 6901 ET. SEQ.
("RCRA"); Federal Water Pollution Control Act, 33 U.S.C. 1251 ET. SEQ.; and
Clean Air Act, 42 U.S.C. 7401 ET. SEQ. and any similar provisions of state or
local law in any jurisdictions where the properties of the Company are located,
and the regulations thereunder, and any other local, state and or federal laws
or regulations, whether currently in existence or hereafter enacted that govern.

     (b)   The Company is not aware of, nor has the Company received notice of,
any past present or future events, conditions, circumstances, activities,
practices, incidents, actions or plans which may interfere with or prevent
continued compliance, or which may give rise to any common law or legal
liability, or otherwise form the basis of any claim, action, suit, proceeding,
hearing or investigation, based on or related to the manufacture, processing,
distribution, use, treatment, storage, disposal, transport or handling, or the
emission, discharge, release or threatened release into the environment, of any
pollutant, contaminant, or hazardous or toxic material or waste.

     (c)   To the best knowledge of the Company, without having made any
independent investigation, no Hazardous Material has been incorporated in, used
on, stored on or under, released from, treated on, transported to or from, or
disposed of on or from any property owned or leased by the Company such that,
under Applicable Environmental Laws (i) any such Hazardous Material would be
required to be removed, cleaned-up or remediated before the property could be
altered, renovated, demolished or transferred, or (ii) the owner or lessee of
the property could be subjected to liability for the removal, clean-up or
remediation of such Hazardous Material; and the Company has not received any
notification from any governmental bodies or other third parties relating to
Hazardous Material on or affecting any property owned or leased by the Company
or relating to any potential or known liability under Applicable Environmental
Laws arising from the ownership or leasing of any property. For purposes of this
Agreement, "Hazardous Material" shall mean any substance which as of the date of
this Agreement shall be identified as "hazardous" or "toxic" or otherwise
regulated under CERCLA or RCRA or which has been or shall be determined at any
tine by any agency or court to be a hazardous or toxic substance under
Applicable Environmental Law. The term "Hazardous Material" shall also include,
without limitation, raw materials, building components, the products of any
manufacturing or other activities on the properties, wastes, petroleum, and
source, special nuclear or by-product material as defined by the Atomic Energy
Act of 1954,42 U.S.C. Sections 3011 ET. SEQ., as amended.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       11

<Page>

     (d)   To the best of the Company's knowledge and belief, without having any
independent investigation, the property owned or leased by the Company does not
contain: (i) asbestos in any form; (ii) urea formaldehyde foam insulation; (iii)
transformers or other equipment which contain dialectic fluid containing levels
of polychlorinated biphenyls; (iv) radon; or (v) except for chemicals, materials
and substances used in the ordinary course of the Company's business, any other
chemical, material or substance, the exposure to which is prohibited, limited or
regulated by a federal, state or local government agency, authority or body, or
which, even if not so regulated, to the best of the Company's knowledge and
belief after reasonable investigation, may or could pose a hazard to the health
and safety of the occupants of the property or the owners or occupants of
property adjacent to or in the vicinity of the property owned or leased by the
Company.

     2.31  ABSENCE OF CERTAIN DEVELOPMENTS. Except as provided in any disclosure
schedule or exhibit attached hereto, since December 31, 1999, the Company has
not:

     (a)   issued any stock, bonds or other corporate securities or any rights,
           options or warrants with respect thereto;

     (b)   borrowed any amount or incurred or become subject to any liabilities
           (absolute or contingent) except current liabilities incurred in the
           ordinary course of business;

     (c)   discharged or satisfied any Lien or encumbrance or paid any
           obligation or liability (absolute or contingent), other than current
           liabilities paid in the ordinary course of business;

     (d)   declared or made any payment or distribution of cash or other
           property to stockholders with respect to its stock, or purchased or
           redeemed, or made any agreements to purchase or redeem, any shares of
           its capital stock;

     (e)   mortgaged or pledged any of its assets, tangible or intangible, or
           subjected them to any Liens, except Liens for current property taxes
           not yet due and payable;

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       12

<Page>

     (f)   sold, assigned or transferred any other tangible assets, or cancelled
           any debts or claims;

     (g)   sold, assigned or transferred any patents, patent rights, trademarks,
           trade names, copyrights, trade secrets or other intangible assets or
           other Intellectual Property Rights, or disclosed any proprietary or
           confidential information to any Person not associated with the
           Company, unless such Person, prior to such disclosure executed and
           delivered a non-disclosure agreement in favor of the Company;

     (h)   suffered any substantial casualty losses or waived any rights of
           material value, whether or not in the ordinary course of business or
           covered by insurance, or otherwise suffered any material adverse
           effect to the Company's business or financial condition;

     (i)   suffered any labor trouble, or any event or condition of any
           character, materially adversely affecting the business or plans of
           the Company; or

     (j)   entered into any other transaction other than in the ordinary course
           of business, or entered into any other material transaction, whether
           or not in the ordinary course of business.

     2.32  OPERATING COMPANY STATUS. The Company is an entity that is primarily
engaged, directly or through a majority owned subsidiary or subsidiaries, in the
production or sale of a product or service other than the investment of capital
such that the Company meets the requirements for qualification as an "operating
company" as set forth in Title 29 of the Code of Federal Regulations at Reg.
Section 2510.3-101 (c)(l).

                                   ARTICLE 3.

                 THE PURCHASERS' REPRESENTATIONS AND WARRANTIES

                  Each Purchaser severally, but not jointly, represents and
warrants to the Company solely as to itself as follows:

     3.1   INVESTMENT REPRESENTATIONS. The Purchaser's present intention is to
acquire the Shares to be acquired by it for its own account and the Shares are
being and will be acquired by it for the purpose of investment and not with a
view to distribution or resale thereof. The acquisition by the Purchaser of the
Shares acquired by it shall constitute a confirmation of this representation by
such Purchaser. The Purchaser further represents that it understands and agrees
that, except as otherwise provided in the Related Agreements, all certificates
evidencing any of the Shares or Conversion Shares, whether upon initial issuance
or upon any transfer thereof, shall bear a legend, prominently stamped or
printed thereon, reading substantially as follows:

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       13

<Page>

     "The securities represented by this certificate have not been registered
     under the Securities Act of 1933 or any other securities laws. These
     securities have been acquired for investment and not with a view to
     distribution or resale. Such securities may not be offered for sale, sold,
     delivered after sale, transferred, pledged or hypothecated in the absence
     of an effective registration statement covering such securities under the
     Securities Act of 1933 and any other applicable securities laws, unless the
     holder shall have obtained an opinion of counsel reasonably satisfactory to
     the corporation that such registration is not required."

     3.2   ACCESS TO INFORMATION. The Purchaser acknowledges that such
Purchaser, during the course of this transaction and prior to the purchase of
any Shares, has had the opportunity to ask questions of and receive answers from
representatives of the Company concerning the terms and conditions of the
offering of the Shares, and to obtain additional information, documents, records
and books relative to the Company, its business, and an investment in the
Company.

     3.3   ACCREDITED INVESTOR STATUS. The Purchaser is an "accredited investor"
as that term is defined in Rule 501 of Regulation D promulgated under the
Securities Act.

     3.4   TRANSFER RESTRICTIONS IMPOSED BY SECURITIES LAWS. The Purchaser
understands that none of the Shares and Conversion Shares have been registered
under the Securities Act or any other applicable securities laws, and,
therefore, cannot be resold unless they are subsequently registered under the
Securities Act and other applicable securities laws or unless an exemption from
such registration is available. The Purchaser agrees not to resell or otherwise
dispose of all or any part of the Shares purchased by it or the Conversion
Shares, except as permitted by law, including, without limitation, any
regulations under the Securities Act and other applicable securities laws; the
Company does not have any present intention and is under no obligation to
register the Shares or Conversion Shares under the Securities Act and other
applicable securities laws, except as provided in the Related Agreements.

                                   ARTICLE 4.

                               CLOSING CONDITIONS

     4.1   CONDITIONS TO THE PURCHASERS' OBLIGATIONS. Each Purchaser's
obligation to purchase and pay for the Shares to be purchased by it at the
Closing is subject to the complete satisfaction by the Company, on or before
such Closing, of the following conditions:

     (a)   OPINION OF COMPANY'S COUNSEL. Each Purchaser shall each have received
           from Bingham Dana LLP, counsel for the Company, an opinion, dated the
           date of the Closing Date, in the form set forth in EXHIBIT D hereto
           with respect to the Closing.

     (b)   REPRESENTATIONS AND WARRANTIES; OFFICER'S CERTIFICATE. The Company's
           representations and warranties contained in Article 2 shall be true
           and correct on and as of the date of the Closing with the same effect
           as if made on and as of the date of the Closing. All agreements and
           conditions to be performed or satisfied by the Company hereunder on
           or before the date of the Closing shall have been duly performed or
           satisfied. The Company shall have delivered to each Purchaser a
           certificate, dated the date of the Closing and signed by the
           President of the Company, to such effect.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       14

<Page>

     (c)   CONSENTS AND APPROVALS. The Company shall have delivered to each
           Purchaser a certificate, dated the date of the Closing and signed by
           the President of the Company, listing any consents, waivers,
           approvals, authorizations, registrations, filings and notifications
           of the character referred to in Section 2.6 or 2.8 which are
           necessary, to which shall be attached evidence, satisfactory to each
           Purchaser, that the same have been obtained or made and are in full
           force and effect, or stating that none is necessary.

     (d)   CERTIFICATE OF INCORPORATION OF THE COMPANY. The Purchasers and their
           counsel shall have received a copy of the charter documents of the
           Company thereof, including the Second Amended and Restated
           Certificate of Incorporation and By-Laws amended as necessary to
           permit the Company to fulfill its obligations under this Agreement
           and certified as of a recent date by the Delaware Secretary of State.

     (e)   CLOSING DOCUMENTS. The Purchasers and their counsel shall have
           received such certificates as to the good standing of the Company and
           certificates of officers of the Company as counsel to the Purchasers
           may reasonably request.

     (f)   PROCEEDINGS AND DOCUMENTS. All corporate and other proceedings and
           all documents incident to the transactions contemplated by this
           Agreement and the other agreements contemplated hereby, including the
           Related Agreements, shall be satisfactory in form and substance to
           each Purchaser and its counsel, and each Purchaser and its counsel
           shall have received copies of all documents and records relating
           thereto.

     (g)   INVESTOR RIGHTS AGREEMENT. The Investor Rights Agreement, which shall
           be in the form attached hereto as EXHIBIT E, shall have become
           effective in accordance with its terms.

     (h)   RIGHT OF FIRST REFUSAL, CO-SALE AND WAIVER. The Right of First
           Refusal, Co-Sale and Waiver Agreement, which shall be in the form
           attached hereto as EXHIBIT F, shall have become effective in
           accordance with its terms.

     (i)   SERIES D CONVERTIBLE PREFERRED STOCK. Each Purchaser shall have
           received a stock certificate evidencing its ownership of the Shares
           in the amounts set forth in EXHIBIT A hereof, which Shares have been
           duly authorized and issued by the Company.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       15

<Page>

     (j)   COMPANY CERTIFIED RESOLUTIONS. At the Closing, the Purchasers shall
           have received certified corporate resolutions adopted by the Board of
           Directors or the stockholders of the Company authorizing the
           execution, delivery and performance of this Agreement and any other
           document or instrument executed in connection therewith, and the
           issuance, sale and delivery of the Shares and the Conversion Shares.

     (k)   BLUE SKY. All consents, permits, approvals, qualifications and/or
           registrations required to be obtained or effected under any
           applicable securities or "Blue Sky" laws of any jurisdiction shall
           have been obtained or effected.

     4.2   CONDITIONS TO THE COMPANY'S OBLIGATIONS. The Company's obligation to
issue the Shares to the Purchasers at the Closing is subject to the satisfaction
of the following conditions:

     (a)   REPRESENTATIONS AND WARRANTIES. The representations and warranties of
           each Purchaser contained in Article 3 shall be true, correct and
           complete in all material respects on and as of the date of the
           Closing with the same force and effect as if they had been made on
           and as of the date of the Closing.

     (b)   PAYMENT OF PURCHASE PRICE. Each Purchaser shall have - delivered to
           the Company and the Company shall have received payment in full of
           the purchase price relating to the number of Shares to be purchased
           by such Purchaser at the Closing.

                                   ARTICLE 5.

                                 INDEMNIFICATION

     5.1   COMPANY INDEMNIFICATION. The Company shall indemnify, defend and hold
each Purchaser and its officers, directors, partners, employees and agents and
each other Person which controls (within the meaning of the Securities Act) such
Purchaser or any of its partners harmless against all liability, loss or damage,
together with all reasonable costs and expenses related thereto (including legal
and accounting fees and expenses), arising from, relating to, or connected with
(i) the untruth, inaccuracy or breach of any representations, warranties or
covenants made by the Company and contained herein or in the Related Agreements
or (ii) the use, generation, storage, release, threatened release, discharge,
disposal or presence of Hazardous Materials on, under or about any properties
owned or leased by the Company by any Person during the period that the Company
was the legal or equitable owner of any properties owned or leased by the
Company or which occurred prior to such time and was otherwise actually known
by, or should have been known by, the Company. The obligation of the Company to
indemnify each Purchaser and its of officers, directors, partners, employees and
agents and each other Person which controls (within the meaning of the
Securities Act) such Purchaser or any of its partners shall specifically cover
and include, without limitation, all fines and penalties imposed by federal,
state or local authorities, costs of removing or neutralizing the Hazardous
Materials, injury to the property adjoining any properties owned or leased by
the Company, injury to persons living or working on or about any properties
owned or leased by the Company or adjoining or otherwise affecting property, and
all other indirect or consequential damages incurred by each Purchaser and its
officers, directors, partners, employees and agents and each other Person which
controls (within the meaning of the Securities Act) such Purchaser or any of its
partners.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       16

<Page>

     5.2   PURCHASERS' INDEMNIFICATION. Each of the Purchasers, severally but
not jointly, shall indemnify, defend and hold the Company and its officers,
directors, employees and agents and each other Person which controls (within
the meaning of the Securities Act) the Company harmless against all liability,
loss or damage, together with all reasonable costs and expenses related
thereto (including legal and accounting fees and expenses), arising from,
relating to, or connected with the untruth, inaccuracy or breach of any
representations or warranties of such Purchaser contained herein or in the
Related Agreements. Notwithstanding the preceding sentence, the aggregate
amount that may be recovered from any Purchaser by the Company or its of
officers, directors, employees, agents or other controlling Persons under this
Section 5.2 shall be limited to the total purchase price paid hereunder by
such Purchaser for the Series D Preferred Stock.

                                   ARTICLE 6.

                                   DEFINITIONS

     6.1   DEFINITIONS. Except as otherwise defined in this Agreement or as the
context may otherwise require, the following terms shall have the respective
meanings set forth below whenever used in this Agreement:

     "AFFILIATE" has the meaning ascribed to that term in Rule 12b-2 under the
Exchange Act, or any successor rule.

     "CLOSING" shall have the meaning assigned to that term in Section 1.2 of
this Agreement.

     "CLOSING DATE" shall have the meaning assigned to that term in Section 1.2
of this Agreement.

     "COMMISSION" shall mean the Securities and Exchange Commission and any
successor agency of the Federal government administering the Securities Act and
the Exchange Act.

     "CONVERSION SHARES" shall have the meaning assigned to that term in Section
2.15 of this Agreement.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       17

<Page>

     "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934, as amended,
and any similar or successor Federal statute, and the rules and regulations of
the Commission thereunder, all as the same shall be in effect at the time.

     "GUARANTEE" shall mean any obligation, contingent or otherwise, of any
Person guaranteeing or having the economic effect of guaranteeing any
Indebtedness of any other Person in any manner, whether directly or indirectly,
and including, without limitation, any obligation of such Person, direct or
indirect, (i) to purchase or pay (or advance or supply funds for the purchase or
payment of) such Indebtedness or to purchase (or to advance or supply funds for
the purchase of) any security for the payment of such Indebtedness, (ii) to
purchase property, securities or services for the purpose of assuring the owner
of such Indebtedness of the payment of such Indebtedness, or (iii) to maintain
working capital, equity capital or other financial statement condition of the
primary obligor so as to enable the primary obligor to pay such Indebtedness;
PROVIDED, HOWEVER, that the term "Guarantee" shall not include endorsements for
collection or deposit, in either case, in the ordinary course of business.

     "INDEBTEDNESS" shall mean, with respect to any Person, (i) all obligations
of such Person for borrowed money, or with respect to deposits or advances of
any kind (other than deposits, advances or excess payments accepted in
connection with the sale by such Person of products or services in the ordinary
course of business), (ii) all obligations of such Person evidenced by bonds,
debentures, notes or similar instruments, (iii) all obligations of such Person
upon which interest charges are customarily paid (other than obligations
accepted in connection with the purchase by such Person of products or services
in the ordinary course of business), (iv) all obligations of such Person under
conditional sale or other title retention agreements relating to property
purchased by such Person, (v) all obligations of such Person issued or assumed
as the deferred purchase price of property or services (other than accounts
payable to suppliers incurred in the ordinary course of business and paid when
due), (vi) all Indebtedness of others secured by (or for which the holder of
such Indebtedness has an existing right, contingent or otherwise, to be secured
by) any Lien or security interest on property owned or acquired by such Person
whether or not the obligations secured thereby have been assumed, (vii) all
obligations of such Person under leases required to be accounted for as capital
leases under generally accepted accounting principles, and (viii) all Guarantees
of such Person.

     "INTELLECTUAL PROPERTY RIGHTS" shall mean any and all, whether domestic or
foreign, patents, patent applications, patent rights, trade secrets,
confidential business information, formula, biological or chemical processes,
compounds, cell lines, fungi, yeast, laboratory notebooks, algorithms,
copyrights, mask works, claims of infringement against third parties, licenses,
permits, license rights to or of technologies (other than commercially available
off-the-self software purchased or licensed for less than a total cost of
$100,000 in the aggregate), contract rights with employees, consultants or third
parties, tradenames, trademarks, trademark applications, trademark rights,
inventions and discoveries, and other such rights generally classified as
intangible, intellectual property assets in accordance with generally accepted
accounting principles.

     "INVESTMENT" shall mean, with respect to any Person, any loan, advance or
extension of credit (other than in connection with the sale by such Person of
products or services in the ordinary course of business) by such Person to, and
any Guarantee or other contingent liability with respect to the capital stock.
Indebtedness or other obligations of, and any contributions to the capital of,
any other Person, as well as any ownership, purchase or other acquisition by
such Person of any interest in any capital stock or other securities of any such
other Person as well as any transfer or sale (other than in connection with the
sale by such Person of products or services in the ordinary course of business)
of property by such Person to any other Person other than upon full payment, in
cash, of not less than the agreed sale price or the fair value of such property,
whichever is higher.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       18
<Page>

     "LIEN" shall mean: (i) any interest in property (whether real, personal or
mixed and whether tangible or intangible) which secures an obligation owed to,
or a claim by, a Person other than the owner of such property, whether such
interest is based on the common law, statute or contract, including, without
limitation, any such interest arising from a lease, mortgage, charge, pledge,
security agreement, conditional sale, trust receipt or deposit in trust, or
arising from a consignment of bailment given for security purposes (other than a
trust receipt or deposit given in the ordinary course of business which does not
secure any obligation for borrowed money), (ii) any encumbrance upon such
property which does not secure such an obligation, and (iii) any exception to or
defect in the title to or ownership interest in such property, including,
without limitation, reservations, rights of entry, possibilities of reverter,
encroachments, easements, rights of way, restrictive covenants, licenses and
PROFITS A PRENDRE. For purposes of this Agreement, any Person shall be deemed to
be the owner of the leasehold or other interest in any property which it has
acquired or holds subject to a lease and the owner of any property which it has
acquired or holds subject to a conditional sale agreement or other similar
arrangement pursuant to which title to the property has been retained by or
vested in some other Person for security purposes.

     "PERSON" shall include any individual, a corporation, an association, a
partnership, a trust or estate, a government and any agency or political
subdivision thereof, or any other entity.

     "SECURITIES ACT" shall mean the Securities Act of 1933, as amended, and any
similar or successor Federal statute, and the rules and regulations of the
Commission thereunder, all as the same shall be in effect from time to time.

     "STOCK PLAN" shall have the meaning assigned to that term in Section 2.15
of this Agreement.

     "SUBSIDIARY" or "SUBSIDIARIES" shall mean any corporation, partnership,
trust or other entity of which the Company and/or any of its other Subsidiaries
directly or indirectly owns at the time a majority of the outstanding shares of
any class of equity security of such corporation, partnership, trust or other
entity.

     6.2   ACCOUNTING PRINCIPLES. The character or amount of any asset,
liability, capital account or reserve and of any item of income or expense
required to be determined pursuant to this Agreement, and any consolidation or
other accounting computation required to be made pursuant to this Agreement, and
the construction of any definition in this Agreement containing a financial
term, shall be determined or made, as the case may be, in accordance with
generally accepted accounting principles, to the extent applicable, unless such
principles are inconsistent with the express requirements of this Agreement.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       19
<Page>

     6.3   "DIRECTLY OR INDIRECTLY". If any provision in this Agreement refers
to any action taken or to be taken by any Person, or which such Person is
prohibited from taking, such provision shall be applicable whether such action
is taken directly or indirectly by such Person, whether or not expressly
specified in such provision.

                                   ARTICLE 7.

                                  MISCELLANEOUS

     7.1   NOTICES. All notices, requests, consents and other communications
hereunder shall be in writing, shall be addressed to the receiving party's
address set forth below or to such other address as a party may designate by
notice hereunder, and shall be either (i) delivered by hand, (ii) made by
telecopy or facsimile transmission, (iii) sent by overnight courier, or (iv)
sent by certified mail, return receipt requested, postage prepaid.

     If to a Purchaser:                 To its address set forth on EXHIBIT A;

     With a copy, in the case           Wollmuth Maher & Deutsch LLP
     of a notice to OrbiMed             500 Fifth Avenue, 12th Floor
     Advisors LLC, to:                  New York, NY 10110
                                        Attn: Kenneth G. Alberstadt, Esq.
                                        212-382-3300 (Telephone)
                                        212-382-0050 (Fax)

     If to the Company:                 NeoGenesis Drug Discovery, Inc.
                                        840 Memorial Drive
                                        Cambridge, MA 02139
                                        Attn: David Hunter, CFO
                                        617-868-1500 (Telephone)
                                        617-868-1515 (Fax)

     With a copy to:                    Bingham Dana LLP
                                        150 Federal Street
                                        Boston, MA 02110
                                        Attn: John J. Concannon III, Esq.
                                        617-951-8000 (Telephone)
                                        617-951-8736 (Fax)

All notices, requests, consents and other communications hereunder shall be
deemed to have been given (i) if by hand, at the time of the delivery thereof to
the receiving party at the address of such party set forth above, (ii) if made
by telecopy or facsimile transmission, at the time that receipt thereof has been
acknowledged by electronic confirmation or otherwise, (iii) if sent by overnight
courier, on the next business day (or if sent overseas, on the second business
day) following the day such notice is delivered to the courier service, or (iv)
if sent by registered or certified mail, on the 5th business day (or if sent
overseas, on the 10th business day) following the day such mailing is made.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       20
<Page>

     7.2   ENTIRE AGREEMENT. This Agreement, together with the Exhibits and
Schedules hereto, and the other agreements executed and delivered herewith
embody the entire agreement and understanding between the Purchasers and the
Company, and supersede all prior oral or written agreements and understandings
relating to the subject matter hereof. No statement, representation, warranty,
covenant or agreement of any kind not set forth in this Agreement, including the
Exhibits and Schedules hereto, shall affect, or be used to interpret, change or
restrict, the express terms and provisions of this Agreement.

     7.3   MODIFICATIONS AND AMENDMENTS. This Agreement may not be changed,
modified or discharged orally, nor may any waivers or consents be given orally
hereunder, and every such change, modification, discharge, waiver or consent
shall be in writing and signed by the Person against which enforcement thereof
is sought.

     7.4   WAIVERS AND CONSENTS. Any waiver or consent hereunder shall be
effective only in the specific instance and for the purpose for which it was
given, and shall not constitute a continuing waiver or consent. Notwithstanding
the consummation of the transactions contemplated hereby, no Purchaser waives or
relinquishes any right it may have or may acquire against the Company or any of
its Affiliates or agents in connection with the acquisition of Series D
Preferred Stock by such Purchaser, or the ownership thereof. All such rights
shall remain unimpaired by the execution of this Agreement and the consummation
of the transactions contemplated hereby.

     7.5   BINDING EFFECT, ASSIGNMENT. This Agreement shall be binding upon and
inure to the benefit of the Company, and the Purchasers and their respective
heirs, successors (including, without limitation, by sale or transfer of all or
substantially all assets, merger or consolidation) and assigns, except that the
Company shall not have the right to delegate its obligations hereunder or to
assign its rights hereunder or any interest herein except by a consent complying
with Section 7.3 above.

     7.6   GOVERNING LAW. This Agreement and the rights and obligations of the
parties hereunder shall be construed in accordance with and governed by the law
of the State of New York, without giving effect to the conflict of law
principles thereof.

     7.7   SEVERABILITY. In the event that any court of competent jurisdiction
shall determine that any provision, or any portion thereof, contained in this
Agreement shall be unenforceable in any respect, then such provision shall be
deemed limited to the extent that such court deems it enforceable, and as so
limited shall remain in fall force and effect. In the event that such court
shall deem any such provision, or portion thereof, wholly unenforceable, the
remaining provisions of this Agreement shall nevertheless remain in full force
and effect.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       21
<Page>

     7.8   INTERPRETATION. The parties hereto acknowledge and agree that: (i)
each party and its counsel, if so represented, reviewed and negotiated the
terms and provisions of this Agreement excluding Schedules and Exhibits and
have contributed to its revision; and (ii) the rule of construction to the
effect that any ambiguities are resolved against the drafting party shall not
be employed in the interpretation of this Agreement.

     7.9   HEADINGS AND CAPTIONS. The headings and captions of the various
subdivisions of this Agreement are for convenience of reference only and shall
in no way modify or affect the meaning or construction of any of the terms or
provisions hereof.

     7.10  NO WAIVER OF RIGHTS, POWERS AND REMEDIES. No failure or delay by a
party hereto in exercising any right, power or remedy under this Agreement, and
no course of dealing between the parties hereto, shall operate as a waiver of
any such right, power or remedy of the party. No single or partial exercise of
any right, power or remedy under this Agreement by a party hereto, nor any
abandonment or discontinuance of steps to enforce any such right, power or
remedy, shall preclude such party from any other or further exercise thereof or
the exercise of any other right, power or remedy hereunder. The election of any
remedy by a party hereto shall not constitute a waiver of the right of such
party to pursue other available remedies. No notice to or demand on a party not
expressly required under this Agreement shall entitle the party receiving such
notice or demand to any other or further notice or demand in similar or other
circumstances or constitute a waiver of the rights of the party giving such
notice or demand to any other or further action in any circumstances without
such notice or demand.

     7.11  RELIANCE. The parties hereto agree that, notwithstanding any access
to information by any party or any right of a party to this Agreement to
investigate the affairs of any other party to this Agreement, the party having
such access and right to investigate shall have the right to rely fully upon
the representations and warranties of the other party expressly contained in
this Agreement and on the accuracy of any Schedule, Exhibit or other document
attached hereto or referred to herein or delivered by such other party or
pursuant to this Agreement. Each of the Purchasers acknowledges that, based on
information provided by the Company, it has made its own analysis and decisions
regarding the transactions contemplated hereby and that it is not relying on
any of the other Purchasers in executing this Agreement or consummating the
transactions contemplated hereby.

     7.12  SURVIVAL. All representations and warranties made by the parties
hereto in this Agreement or in any other agreement, certificate or instrument
provided for or contemplated hereby, shall survive (i) the execution and
delivery hereof, (ii) any investigations made by or on behalf of the parties and
(iii) the Closing and shall remain in full force and effect thereafter so long
as any shares of Series D Preferred Stock remain outstanding.

     7.13  FURTHER ASSURANCES. From and after the date of this Agreement, upon
the request of any Purchaser or the Company, the Company and the Purchasers
shall execute and deliver such instruments, documents and other writings as may
be reasonably necessary or desirable to confirm and carry out and to effectuate
fully the intent and purposes of this Agreement.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       22
<Page>

     7.14  COSTS, EXPENSES AND TAXES. As a condition precedent to the Closing,
the Company agrees to pay at the Closing in connection with the preparation,
execution and delivery of this Agreement and the Related Agreements, the legal
fees of Wollmuth Maher & Deutsch LLP, special counsel for the Purchasers, not to
exceed $35,000 (unless any increase thereto is agreed to by the Company), plus
the expenses of such counsel. In addition, the Company shall pay its own
expenses in connection with the preparation, execution and delivery of this
Agreement and the Related Agreements and to pay any and all stamp, or other
similar taxes payable or determined to be payable in connection with the
execution and delivery of this Agreement, the issuance of the Shares and the
other instruments and documents to be delivered hereunder or thereunder, and
agrees to save the Purchasers harmless from and against any and all liabilities
with respect to or resulting from any delay in paying or omission to pay such
expenses and taxes. In the event that any of the Purchasers shall retain an
attorney or attorneys to collect, enforce, protect, maintain, preserve or
foreclose its interests with respect to this Agreement or the Related Agreements
or to protect the rights of any holder or holders with respect thereto, the
Company shall pay all of the reasonable costs and reasonable expenses of such
collection, enforcement or protection, including, without limitation, reasonable
attorneys' fees, and such Purchaser may take judgment for all such amounts.

     7.15  COUNTERPARTS. This Agreement may be executed in one or more
counterparts, and by different parties hereto on separate counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.

     7.16  USE OF DEFINITIONS; GENDER. Any definitions used herein defined in
the plural shall be deemed to include the singular as the context may require
and any definitions used herein defined in the singular shall be deemed to
include the plural as the context may require. Wherever reference is made
herein to the male, female or neuter genders, such reference shall be deemed to
include any of the other genders as the context may require.

     7.17  JURISDICTION AND SERVICE OF PROCESS. Any legal action or proceeding
with respect to this Agreement may be brought in the courts of the State of New
York or of the United States of America for the District of New York. By
execution and delivery of this Agreement, each of the parties hereto accepts for
itself and in respect of its property, generally and unconditionally, the
jurisdiction of the aforesaid courts. Each of the parties hereto irrevocably
consents to the service of process of any of the aforementioned courts in any
such action or proceeding by the mailing of copies thereof by certified mail,
postage prepaid, to the party at its address set forth in Section 7.1 hereof.

     7.18  PUBLICITY. No party shall issue any press releases or otherwise make
any public statement with respect to the transactions contemplated by this
Agreement without the prior written consent of the other party, except as may be
required by law.

     7.19  BROKERS OR FINDERS. The Company represents and warrants to each of
the Purchasers, and each of the Purchasers, as to itself, represents and
warrants to the Company, that no person or entity has or will have, as a result
of the transactions contemplated by this Agreement, any right, interest or valid
claim against or upon the Company or the Purchasers for any commission, fee or
other compensation as a finder or broker because of any act or omission by the
Company or the Purchasers or by any agent of the Company of the Purchasers.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       23
<Page>

                  IN WITNESS WHEREOF, the parties hereto have executed this
Agreement or caused this Agreement to be executed by their duly authorized
representatives, as of the date first written above.

                                      NEOGENESIS DRUG DISCOVERY, INC.

                                      By: /s/ SATISH JINDAL, Ph.D.
                                          ----------------------------------
                                           Name:  Satish Jindal, Ph.D.
                                           Title: President

                 Counterpart Signature Pages Begin on Next Page

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       24
<Page>

COUNTERPART SIGNATURE PAGE FOR PURCHASERS

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

 FREYA FANNING & CO
------------------------------------
Printed Name of Purchaser

 /s/  THOMAS B. HALLOWELL, GENERAL PARTNER
 ------------------------------------------
Signature of Purchaser

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  THEODORE G. JOHNSON
-------------------------------
Printed Name of Purchaser

 /s/  THEODORE G. JOHNSON
-------------------------------
Signature of Purchaser

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       25
<Page>

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  FINSBURY WORLDWIDE PHARMACEUTICAL TRUST PLC
---------------------------------------------
Printed Name of Purchaser

By: OrbiMed Advisors, LLC, its Investment Advisor

By: /s/ ERIC A. BITTELMAN
    -----------------------------------------
    Name:  Eric A. Bittelman
    Title: Chief Financial Officer

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  PW JUNIPER CROSSOVER FUND, L.L.C.
-------------------------------------------
Printed Name of Purchaser

By: OrbiMed Advisors, Inc., its Member

By: /s/ ERIC A. BITTELMAN
    ---------------------------------------
    Name:  Eric A. Bittelman
    Title: Chief Financial Officer

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       26
<Page>

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

 CADUCEUS PRIVATE INVESTMENTS, LP
---------------------------------
Printed Name of Purchaser

By: OrbiMed Capital, LLC, its General Partner

By: /s/ ERIC A. BITTELMAN
    ---------------------------------------
    Name:  Eric A. Bittelman
    Title: Chief Financial Officer

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  ORBIMED ASSOCIATES, LLC
-------------------------
Printed Name of Purchaser

By: OrbiMed Advisors, LLC, its Managing Member

By: /s/ ERIC A. BITTELMAN
    ------------------------------------------
    Name:  Eric A. Bittelman
    Title: Chief Financial Officer

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       27
<Page>

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

FORT WASHINGTON PRIVATE EQUITY INVESTORS II, L.P.
By:  Fort Washington Capital Partners, LLC, General Partner
BY:  FORT WASHINGTON INVESTMENT ADVISORS, INC., MANAGING MEMBER
Printed Name of Purchaser

By: /S/ WILLIAM F. LEDWIN
    ----------------------------------------
    Name:  William F. Ledwin
    Title: President

By: /S/ JOHN O'CONNOR
    -------------------------------------
    Name:  John O'Connor
    Title: Director of Private Equity

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

FORT WASHINGTON PRIVATE EQUITY INVESTORS III, L.P.
By:  Fort Washington Capital Partners, LLC, General Partner
BY:  FORT WASHINGTON INVESTMENT ADVISORS, INC., MANAGING MEMBER
Printed Name of Purchaser

By: /s/ WILLIAM F. LEDWIN
    ----------------------------------------
    Name:  William F. Ledwin
    Title: President

By: /s/ JOHN O'CONNOR
    -------------------------------------
    Name:  John O'Connor
    Title: Director of Private Equity

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       28
<Page>

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  GUY ROCHMAN M.D.
------------------------------------
Printed Name of Purchaser

/s/ GUY ROCHMAN M.D.
------------------------------------------
Signature of Purchaser

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  JUSTIN P. MORREALE
-----------------------------------------------------
Printed Name of Purchaser

 /s/ JUSTIN P. MORREALE
-----------------------------------------------------
Signature of Purchaser

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  DAVID L. ENGEL
-----------------------------------------------------
Printed Name of Purchaser

 /s/ DAVID L. ENGEL
-----------------------------------------------------
Signature of Purchaser

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       29
<Page>

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  VICTOR J. PACI
-------------------------------------------
Printed Name of Purchaser

 /s/ VICTOR J. PACI
-------------------------------------------
Signature of Purchaser

     The undersigned hereby agrees to become a party to that certain Preferred
Stock Purchase Agreement dated as of December 27, 2000 (the "AGREEMENT") among
NeoGenesis Drug Discovery, Inc. (the "COMPANY") and others set forth on the
signature pages thereto. From and after the undersigned's execution and delivery
and the Company's acceptance of this Counterpart Signature Page, the undersigned
shall be a party to the Agreement and the shares of Common Stock purchased by
the undersigned shall be deemed to be "Shares" for all purposes of the
Agreement.

  JOHN J. CONCANNON
----------------------------------------------
Printed Name of Purchaser

 /s/ JOHN J. CONCANNON
----------------------------------------------
Signature of Purchaser

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       30<Page>

                                                                    Exhibit 10.4

                            INVESTOR RIGHTS AGREEMENT

         INVESTOR RIGHTS AGREEMENT made as of December 27, 2000 by and among (i)
NeoGenesis Drug Discovery, Inc., a Delaware corporation (the "COMPANY"), (ii)
the holders of the Series A Convertible Preferred Stock, par value $0.001 per
share listed on Exhibit A-1 attached hereto (the "SERIES A PURCHASERS"), (iii)
the holders of the Series B Convertible Preferred Stock, par value $0.001 per
share listed on Exhibit A-2 attached hereto (the "SERIES B PURCHASERS"), (iv)
the holders of the Series C Convertible Preferred Stock, par value $0.001 per
share listed on Exhibit A-3 attached hereto (the "SERIES C PURCHASERS"), (v) the
Purchasers listed on Exhibit A-4 (the "SERIES D PURCHASERS") of that certain
Preferred Stock Purchase Agreement of even date herewith (the "SERIES D PURCHASE
AGREEMENT") and (vi) the holders of the Company's Common Stock, par value $0.001
per share (the "ADDITIONAL HOLDERS"). The Series A Purchasers, the Series B
Purchasers, the Series C Purchasers and the Series D Purchasers are collectively
referred to herein as the "Investors" or the "Purchasers."

         WHEREAS, the Company proposes to issue and sell an aggregate of up to
4,623,487 shares of Series D Convertible Preferred Stock, par value $.001 per
share (the "SERIES D STOCK"), to the Series D Purchasers pursuant to the Series
D Purchase Agreement;

         WHEREAS, in connection with the execution of the Series D Purchase
Agreement, the Series A Purchasers, the Series B Purchasers and the Series C
Purchasers have requested that the Company extend to them registration rights
and certain other rights and covenants as set forth herein; and

         WHEREAS, the Board of Directors of the Company has determined that it
is in the best interests of the Company that the Company enter into this
Agreement.

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

         GENERAL PROVISIONS

         1.1 SHARES SUBJECT TO THIS AGREEMENT. The Investors and the Company
expressly agree that the terms and restrictions of this Agreement shall apply to
all shares of capital stock which any of the Investors now owns or hereafter
acquires by any means, including without limitation by purchase, assignment or
operation of law, or as a result of any stock dividend, stock split,
reorganization, reclassification, whether voluntary or involuntary, or other
similar transaction, and to any shares of capital stock of any successor in
interest of the Company, whether by sale, merger, consolidation or other similar
transaction, or by purchase, assignment or operation of law (the "SHARES").

         1.2 NO PARTNERSHIP RELATIONSHIP. Notwithstanding, but not in limitation
of, any other provision of this Agreement, the parties understand and agree that
the creation, management and operation of the Company shall not create or imply
a general partnership between or among the Investors and shall not make any
Investor the agent or partner of any other Investor for any purpose.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       1
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         1.3 CERTAIN DEFINITIONS. As used in this Agreement, the following terms
shall have the following respective meanings:

         "AFFILIATE" has the meaning ascribed to that term in Rule 12b-2 under
the Exchange Act, or any successor rule.

         "COMMISSION" shall mean the Securities and Exchange Commission and any
successor agency of the Federal government administering the Securities Act and
the Exchange Act.

         "COMMON STOCK" shall mean (i) the common stock, $.001 par value per
share, of the Company, (ii) any other capital stock of the Company, however
designated, authorized on or after the date hereof, which shall neither be
limited to a fixed sum or percentage of par value in respect of the rights of
the holders thereof to participate in dividends nor entitled to a preference in
the distribution of assets upon the voluntary or involuntary liquidation,
dissolution or winding up of the Company; and (iii) any other securities into
which or for which any of the securities described in (i) or (ii) may be
converted or exchanged pursuant to a plan of recapitalization, reorganization,
merger, consolidation, sale of assets or other similar transaction.

         "EXCHANGE ACT" shall mean the Securities Exchange Act of 1934, as
amended, and any similar or successor Federal statute, and the rules and
regulations of the Commission thereunder, all as the same shall be in effect
from time to time.

         "INITIAL PUBLIC OFFERING" shall mean the first underwritten public
offering of Common Stock of the Company, offered on a firm commitment basis
pursuant to a registration statement filed with the Commission under the
Securities Act on Form S-1 or its then equivalent, in which (i) the aggregate
gross proceeds to the Company equals or exceeds $15,000,000 and (ii) the initial
public offering price per share equals or exceeds $15.00 (subject to appropriate
adjustment for stock splits, stock dividends, combinations and other similar
recapitalization events).

         "PERSON" means an individual, corporation, partnership, joint venture,
trust or unincorporated organization, or a government or any agency or political
subdivision thereof.

         "PREFERRED STOCK" means the Series A Stock, the Series B Stock, the
Series C Stock and the Series D Stock.

         "PREFERRED STOCK DIRECTOR" means a director designated by the holders
of a class of Preferred Stock in accordance with Article 4.

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    SEPARATELY WITH THE COMMISSION.

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         The terms "REGISTER", "REGISTERED" and "REGISTRATION" shall refer to a
registration effected by preparing and filing a registration statement in
compliance with the Securities Act and applicable rules and regulations
thereunder, and the declaration or ordering of the effectiveness of such
registration statement, or, as the context may require, under the Exchange Act
or applicable state securities laws.

         "REGISTRABLE SECURITIES" shall mean (i) shares of Preferred Stock; (ii)
shares of Common Stock or other securities issued or issuable pursuant to the
conversion of the Preferred Stock (the "Conversion Shares"); and (iii) any
shares of Common Stock or other securities issued or issuable with respect to
the Preferred Stock or the Conversion Shares by reason of any stock split, stock
dividend, recapitalization, reorganization, merger, consolidation, sale of
assets or similar event, excluding in any event securities which (a) have been
registered under the Securities Act pursuant to an effective registration
statement filed thereunder and disposed of in accordance with the registration
statement covering them or (b) are able to be publicly sold pursuant to Rule
144(k) under the Securities Act. Wherever reference is made in this Agreement to
a request or consent of holders of a certain percentage of Registrable
Securities, the determination of such percentage shall be calculated on the
basis of shares of Common Stock issued or issuable upon conversion of the
Preferred Stock even if such exercise has not been effected.

         "REGISTRABLE SERIES D SECURITIES" shall mean (i) shares of Series D
Preferred Stock; (ii) shares of Common Stock or other securities issued or
issuable pursuant to the conversion of the Series D Preferred Stock (the "Series
D Conversion Shares"); and (iii) any shares of Common Stock or other securities
issued or issuable with respect to the Series D Preferred Stock or the Series D
Conversion Shares by reason of any stock split, stock dividend,
recapitalization, reorganization, merger, consolidation, sale of assets or
similar event, excluding in any event securities which (a) have been registered
under the Securities Act pursuant to an effective registration statement filed
thereunder and disposed of in accordance with the registration statement
covering them or (b) are able to be publicly sold pursuant to Rule 144(k) under
the Securities Act. Wherever reference is made in this Agreement to a request or
consent of holders of a certain percentage of Registrable Series D Securities,
the determination of such percentage shall be calculated on the basis of shares
of Common Stock issued or issuable upon conversion of the Series D Preferred
Stock even if such exercise has not been effected.

         "REGISTRATION EXPENSES" shall mean the expenses so described in Section
3.7.

         "SECURITIES ACT" shall mean the Securities Act of 1933, as amended, and
any similar or successor Federal statute, and the rules and regulations of the
Commission thereunder, all as the same shall be in effect from time to time.

         "SERIES A STOCK" shall mean the Series A Convertible Preferred Stock,
par value $.001 per share of the Company.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       3
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         "SERIES B STOCK" shall mean the Series B Convertible Preferred Stock,
par value $.001 per share of the Company.

         "SERIES C STOCK" shall mean the Series C Convertible Preferred Stock,
par value $.001 per share of the Company.

         "SELLING EXPENSES" shall mean the expenses so described in Section 3.7.

         "SUBSIDIARY" or "SUBSIDIARIES" shall mean any corporation, partnership,
trust or other entity of which the Company and/or any of its other Subsidiaries
directly or indirectly owns at the time a majority of the outstanding shares of
any class of equity security of such corporation, partnership, trust or other
entity.

                  2.       PERCENTAGE MAINTENANCE RIGHTS

         2.1 NOTICE OF NEW ISSUANCE. Except with respect to "Exempt Issuances"
as defined in Section 2.3, in the event that the Company intends to issue any
(i) shares of Common Stock, (ii) warrants, options or other rights to purchase
Common Stock or Convertible Securities (collectively, "RIGHTS"), or (iii) any
debentures or other securities convertible into or exchangeable for shares of
Common Stock (collectively, "CONVERTIBLE SECURITIES"), the Company will deliver
to each of the holders of the Preferred Stock a notice (the "OFFER NOTICE") of
such intention, describing the Common Stock, Rights or Convertible Securities
(the "NEW ISSUANCE") and stating the price and other terms and conditions
thereof.

         2.2  RIGHT TO PURCHASE SHARES, RIGHTS OR CONVERTIBLE SECURITIES.
         (a)  EXERCISE OF RIGHT. Each of the holders of the Preferred Stock (the
"Holders") shall have 30 days from the date of the Offer Notice to agree to
purchase such number of shares of Common Stock, Rights or Convertible Securities
at the price and upon the terms specified in the Offer Notice by giving written
notice to the Company, such price to be paid in full in cash or by check at the
time of issuance of such securities to the Holders so that, after giving effect
to the issuance to the Holders and the conversion, exercise and exchange into or
for (whether directly or indirectly) shares of Common Stock of all such Rights
and Convertible Securities, each holder of Preferred Stock who exercises such
right will continue to maintain its same proportionate ownership of Common Stock
as of the date immediately preceding the New Issuance, treating each Holder, for
the purpose of such computation, as the holder of the number of shares of Common
Stock which would be issuable to it upon conversion, exercise and exchange of
all Rights and Convertible Securities held by it on the date immediately
preceding the New Issuance and assuming the like conversion, exercise and
exchange of all such securities held by other persons. The rights set forth in
this Article 2 shall be exercised by the Holders, if at all, by written notice
to the Company delivered not later than thirty (30) days after the receipt by
the Holders of the Offer Notice in accordance with the terms and conditions
stated therein, and such right shall expire at the end of the thirtieth day
after the day of the receipt by the Holders of the Offer Notice.

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    SEPARATELY WITH THE COMMISSION.

                                       4
<Page>

         (b) If any Holder fails to exercise its right hereunder to purchase its
proportionate ownership interest ("EQUITY PERCENTAGE") of a New Issuance (or
fails to pay the purchase price in respect of such New Issuance in full in cash
at the proposed time of closing), the Company shall so notify the other Holders
in a written notice (the "EXCESS SECURITIES NOTICE"). The Excess Securities
Notice shall be given by the Company promptly after it learns of the intention
of any Holder not to purchase all of its Equity Percentage of the New Issuance
or the failure of any Holder to pay such purchase price, but in no event later
than ten (10) days after the expiration of the 30-day period. The Holders who or
which have agreed to purchase their Equity Percentage of the New Issuance shall
have the right to purchase the portion not purchased by such Holder (the "EXCESS
SECURITIES"), on a pro rata basis, by giving notice within ten (10) days after
receipt of the Excess Securities Notice from the Company. The twenty (20) day
period during which (i) the Company must give the Excess Securities Notice to
the other Holders and (ii) each of the other Holders must give the Company
notice of its intention to purchase all or any portion of its pro rata share of
the its Excess Securities, is hereinafter referred to as the "Excess Securities
Period."

         2.3 EXEMPT ISSUANCES. The issuances referred to in Section 2.1 which
will not give the Holders the rights described in Section 2.2 (the "EXEMPT
ISSUANCES") are issuances in which shares of Common Stock or Rights or
Convertible Securities of the Company are issued or deemed issued (i) as a
dividend or distribution payable pro rata to all holders of Common Stock or
other securities of the Company and with respect to which the Preferred Stock
has been adjusted or paid; (ii) to employees, consultants, officers and
directors of the Company pursuant to the Company's Employee, Director and
Consultant Stock Option Plan or any other stock or option plan or other
arrangement (a "STOCK PLAN ISSUANCE") approved by the Company's Board of
Directors; (iii) in connection with the conversion or exercise of any options,
warrants or other rights to purchase Common Stock (A) existing on the date
hereof or (B) issued in accordance with the foregoing clause (ii); (iv) to
institutional lenders in connection with the establishment or maintenance by the
Company of credit facilities, approved in each case by a majority of the Board
of Directors of the Company, including at least one director designated by the
Series D Purchasers; (v) in connection with the conversion or exercise of any
options, warrants or other rights to purchase Common Stock issued in accordance
with the foregoing clause (iv); and (vi) in connection with any transaction
(e.g., an acquisition by the Company of another corporation, division or
product, a joint venture, technology licensing, distribution or other business
arrangement) with respect to which a majority of the Board of Directors,
including at least one director designated by the Series D Purchasers, has made
a good faith determination that the primary purpose of such transaction is the
advancement of the business interests of the Corporation as opposed to the
raising of funds.

         2.4 TERMINATION. The respective rights and obligations of the parties
under this Article 2 shall terminate upon the closing of the Company's Initial
Public Offering.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       5
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                  3.       TRANSFER OF REGISTRABLE SECURITIES;

                           REGISTRATION

         3.1 RESTRICTIVE LEGEND. Each certificate representing Registrable
Securities shall, except as otherwise provided in this Section 3.1 or in Section
3.2, be stamped or otherwise imprinted with a legend substantially in the
following form (in addition to any legend required under applicable state
securities laws):

                          "The securities represented by this certificate have
                  not been registered under the Securities Act of 1933 or any
                  other securities laws. These securities have been acquired for
                  investment and not with a view to distribution or resale. Such
                  securities may not be offered for sale, sold, delivered after
                  sale, transferred, pledged or hypothecated in the absence of
                  an effective registration statement covering such securities
                  under the Securities Act of 1933 and any other applicable
                  securities laws, unless the holder shall have obtained an
                  opinion of counsel reasonably satisfactory to the corporation
                  that such registration is not required."

         Upon request of a holder of such a certificate, the Company shall
remove the foregoing legend from the certificate or issue to such holder a new
certificate therefor free of any transfer legend, if there is an effective
registration statement covering the securities represented by such certificate
or, with such request, the Company shall have received either the opinion
referred to in Section 3.2(i) or the "no-action" letter referred to in Section
3.2(ii).

         3.2 NOTICE OF PROPOSED TRANSFER.

         (a) Prior to any proposed sale, pledge, hypothecation or other transfer
of any Registrable Securities (other than under the circumstances described in
Section 3.3, 3.4 or 3.5), the holder thereof shall give written notice to the
Company of its intention to effect such sale, pledge, hypothecation or other
transfer. Each such notice shall describe the manner of the proposed sale,
pledge, hypothecation or other transfer and, if requested by the Company shall
be accompanied by either (i) an opinion of counsel reasonably satisfactory to
the Company to the effect that the proposed sale, pledge, hypothecation or other
transfer may be effected without registration under the Securities Act or (ii) a
"no action" letter from the Commission to the effect that the distribution of
such securities without registration will not result in a recommendation by the
staff of the Commission that action be taken with respect thereto, whereupon the
holder of such stock shall be entitled to transfer such stock in accordance with
the terms of its notice; PROVIDED, HOWEVER, that no such opinion of counsel or
"no action" letter shall be required for a distribution to one or more partners
or members of the transferor (in the case of a transferor that is a partnership
or limited liability company), to a stockholder (in the case of a transferor
that is a corporation) or to a trust grantor (in the case of a transferor that
is a trust) in each case in respect of the beneficial interest of such partner,
stockholder or trust. Each certificate for Registrable Securities transferred as
above provided shall bear the appropriate restrictive legend set forth in
Section 3.1, except that such certificate shall not bear such legend if (i) such
transfer is in accordance with the provisions of Rule 144 (or any other rule
permitting public sale without registration under the Securities Act) or (ii)
the opinion of counsel or "no-action" letter referred to above is to the further
effect that the transferee and any subsequent transferee (other than an
Affiliate of the Company) would be entitled to transfer such securities in a
public sale without registration under the Securities Act or that such legend is
not required to establish compliance with any provisions of the Securities Act.
Notwithstanding any other provision hereof, the restrictions provided for in
this Section 3.2 shall not apply to securities which are not required to bear
the legend prescribed by Section 3.1 in accordance with the provisions of that
Section. If the Company does not accept an opinion of counsel required hereby
signed by the original holder's counsel (it being agreed that an opinion of
Wollmuth Maher & Deutsch LLP shall be considered satisfactory), the Company will
pay the reasonable fees and disbursements of other counsel in connection with
all opinions rendered by them pursuant to this Section 3.2.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       6
<Page>

         (b) No such opinion of counsel or "no action" letter from the
Commission, as set forth in Section 3.2(a) above, shall be required in the event
of a sale, pledge, hypothecation or other transfer of any Registrable Securities
to (i) any Affiliate of an Investor, including, without limitation, any venture
capital limited partnership now existing or hereafter formed which controls, is
controlled by or is under common control with such Investor; and (ii) any
successors or assigns of any of the foregoing persons, provided that the
transferee agrees in writing to be subject to this Agreement to the same extent
as if such transferee were originally a signatory.

         3.3 REQUIRED REGISTRATION.

         (a) At any time after the Initial Public Offering, one or more of the
holders of Registrable Securities constituting more than 50% of either (i) the
total shares of Registrable Securities then outstanding or (ii) the total
Registrable Series D Securities may request the Company to register for sale
under the Securities Act all or any portion of the shares of Registrable
Securities held by such requesting holder or holders for sale in the manner
specified in such notice; PROVIDED, HOWEVER, that the proposed offering price of
the Registrable Securities or Registrable Series D Securities held by such
holder or holders must be at least $5,000,000.

         (b) Following receipt of any notice under this Section 3.3, the Company
shall immediately notify all holders of Registrable Securities from whom notice
has not been received and such holders shall then be entitled within thirty (30)
days after receipt of such notice from the Company to request the Company to
include in the requested registration all or any portion of their shares of
Registrable Securities. The Company shall use its best efforts to register under
the Securities Act, for public sale in accordance with the method of disposition
specified in the notice from requesting holders described in paragraph (a)
above, within 180 days of its receipt of such notice, the number of shares of
Registrable Securities specified in such notice (and in all notices received by
the Company from other holders within thirty (30) days after the receipt of such
notice by such holders). The Company shall be obligated to register the
Registrable Securities pursuant to this Section 3.3 on two (2) occasions with
respect to demands pursuant to clause (i) of Section 3.3(a) and on two (2)
occasions with respect to demands pursuant to clause (ii) of Section 3.3(a)
only, provided, however, that such obligation shall be deemed satisfied only
when a registration statement covering all shares of Registrable Securities
specified in notices received as aforesaid (except to the extent reduced (but
not by more than 10%) by the managing underwriter, if any, pursuant to Section
3.3(d)), for sale in accordance with the method of disposition specified by the
requesting holders, shall have become effective and, if such method of
disposition is a firm commitment underwritten public offering, all such shares
shall have been sold pursuant thereto. Notwithstanding anything to the contrary
contained herein, no request may be made under this Section 3.3 after the
effective date of a registration statement filed by the Company covering a firm
commitment underwritten public offering and prior to the later to occur of the
completion of the period of distribution for such offering or 120 days after the
effective date of such registration statement.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       7
<Page>

         (c) If the holders requesting such registration intend to distribute
the Registrable Securities covered by their request by means of an underwriting,
they shall so advise the Company as a part of their request made pursuant to
this Section 3.3 and the Company shall include such information in the written
notice referred to in paragraph (b) above. The right of any holder to
registration pursuant to this Section 3.3 shall be conditioned upon such
holder's agreeing to participate in such underwriting and to permit inclusion of
such holder's Registrable Securities in the underwriting. If such method of
disposition is an underwritten public offering, the holders of at least a
majority in interest of the shares of Registrable Securities to be sold in such
offering may designate the managing underwriter of such offering, which managing
underwriter shall be reasonably acceptable to the Company. A holder may elect to
include in such underwriting all or a part of the Registrable Securities it
holds.

         (d) A registration statement filed pursuant to this Section 3.3 may,
subject to the following provisions, include (i) shares of Common Stock for sale
by the Company for its own account, and (ii) shares of Common Stock held by
persons who by virtue of agreements with the Company in compliance with the
provisions of Section 3.12 hereof are entitled to include such shares in such
registration (the "OTHER SHAREHOLDERS"), in each case for sale in accordance
with the method of disposition specified by the requesting holders; PROVIDED,
HOWEVER, that if the number of shares so included pursuant to clauses (i) and
(ii) above exceeds the number of Registrable Securities presented by the holders
requesting registration thereof, then such registration shall be deemed to be a
registration in accordance with Section 3.4. If such registration shall be
underwritten, the Company and such Other Shareholders proposing to distribute
their shares through such underwriting shall enter into an underwriting
agreement in customary form with the representative of the underwriter or
underwriters selected for such underwriting on terms no less favorable to such
Other Shareholders than the terms afforded the holders of Registrable
Securities. If and to the extent that the managing underwriter determines that
marketing factors require a limitation on the number of shares to be included in
such registration, then the shares of Common Stock held by Other Shareholders
(other than Registrable Securities) and shares of Common Stock to be sold by the
Company for its own account shall be excluded from such registration to the
extent so required by such managing underwriter, and unless the holders of such
shares and the Company have otherwise agreed in writing, such exclusion shall be
applied first to the shares held by the Other Shareholders to the extent
required by the managing underwriter, then to the shares of Common Stock of the
Company to be included for its own account to the extent required by the
managing underwriter. If the managing underwriter determines that marketing
factors require a limitation of the number of Registrable Securities to be
registered under this Section 3.3, then Registrable Securities shall be excluded
in such manner that the securities to be sold shall be allocated among the
selling holders pro rata based on their ownership of Registrable Securities,
provided that in the event such registration was initiated pursuant to clause
(ii) of Section 3.3(a), no Registrable Series D Securities shall be excluded
unless all other securities have first been excluded from such registration. In
any event all securities to be sold other than Registrable Securities will be
excluded prior to any exclusion of Registrable Securities. No Registrable
Securities or any other security excluded from the underwriting by reason of the
underwriter's marketing limitation shall be included in such registration. If
any holder of Registrable Securities or Other Shareholder who has requested
inclusion in such registration as provided above, disapproves of the terms of
the underwriting, such holder of securities may elect to withdraw therefrom by
written notice to the Company and the managing underwriter. The securities so
withdrawn shall also be withdrawn from registration. Except for registration
statements on Form S-4, S-8 or any comparable form or successor thereto, the
Company will not file with the Commission any other registration statement with
respect to its Common Stock, whether for its own account or that of other
stockholders, from the date of receipt of a notice from requesting holders
pursuant to this Section 3.3 until 120 days after the effective date of such
registration.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       8
<Page>

         3.4 INCIDENTAL REGISTRATION. If the Company at any time (other than
pursuant to Section 3.3 or Section 3.5) proposes to register any of its
securities under the Securities Act for sale to the public, whether for its own
account or for the account of other security holders or both (except with
respect to registration statements on Forms S-4, S-8 or any successor to such
forms or another form not available for registering the Registrable Securities
for sale to the public), each such time it will promptly give written notice to
all holders of the Registrable Securities of its intention so to do. Upon the
written request of any such holder, received by the Company within thirty (30)
days after the giving of any such notice by the Company, to register any or all
of its Registrable Securities, the Company will use commercially reasonable
efforts to cause the Registrable Securities as to which registration shall have
been so requested to be included in the securities to be covered by the
registration statement proposed to be filed by the Company, all to the extent
requisite to permit the sale or other disposition by the holder (in accordance
with its written request) of such Registrable Securities so registered. If the
registration of which the Company gives notice is for a registered public
offering involving an underwriting, the Company shall so advise the holders of
Registrable Securities as a part of the written notice given pursuant to this
Section 3.4. In such event the right of any holder of Registrable Securities to
registration pursuant to this Section 3.4 shall be conditioned upon such
holder's participation in such underwriting to the extent provided herein. All
holders of Registrable Securities proposing to distribute their securities
through such underwriting shall (together with the Company and the Other
Shareholders distributing their securities through such underwriting) enter into
an underwriting agreement in customary form with the underwriter or underwriters
selected for underwriting by the Company. Notwithstanding any other provision of
this Section 3.4, if the underwriter determines that marketing factors require a
limitation on the number of shares to be underwritten, the Company shall so
advise all holders of securities requesting registration of any limitations on
the number of shares to be underwritten, and the number of shares of securities
that are entitled to be included in the registration and underwriting shall be
allocated (i) first to the Company with respect to shares of Common Stock being
sold for its own account; and (ii) then, to holders of Registrable Securities
requesting registration in proportion, as nearly as practicable, to the
respective amounts of securities owned by them. Notwithstanding the foregoing
provisions, the Company may withdraw any registration statement referred to in
this Section 3.4 without thereby incurring any liability to the holders of
Registrable Securities. If any holder of Registrable Securities disapproves of
the terms of any such underwriting, it may elect to withdraw therefrom by
written notice to the Company and the underwriter. Any Registrable Securities or
other securities excluded or withdrawn from such underwriting shall be withdrawn
from such registration.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       9
<Page>

         3.5 REGISTRATION ON FORM S-3.

         (a) In addition to the rights provided in Sections 3.3 and 3.4, subject
to a limit of one (1) registration hereunder in any six (6) month period by
holders of Registrable Series D Securities and one (1) registration hereunder in
any six (6) month period by holders of other Registrable Securities, if at any
time (i) any holder or holders of the Registrable Securities request that the
Company file a registration statement on Form S-3 or any comparable or successor
form thereto for a public offering of all or any portion of the shares of
Registrable Securities held by such requesting holder or holders, the reasonably
anticipated aggregate price to the public of which would exceed $1,000,000, and
(ii) the Company is a registrant entitled to use Form S-3 or any comparable or
successor form thereto to register such shares, then the Company shall use its
best efforts to register under the Securities Act on Form S-3 or any comparable
or successor form thereto, for public sale in accordance with the method of
disposition specified in such notice, the number of shares of Registrable
Securities specified in such notice. Whenever the Company is required by this
Section 3.5 to use its best efforts to effect the registration of Registrable
Securities, each of the procedures and requirements of Section 3.3, including
but not limited to the requirement that the Company notify all holders of
Registrable Securities from whom notice has not been received and provide them
with the opportunity to participate in the offering, shall apply to such
registration, PROVIDED, HOWEVER, that except as provided above, there shall be
no limitation on the number of registrations on Form S-3 which may be requested
and obtained under this Section 3.5.

         (b) The Company shall use commercially reasonable efforts to qualify
for registration on Form S-3 or any comparable or successor form or forms; and
to that end the Company shall register (whether or not required by law to do so)
the Common Stock under the Exchange Act in accordance with the provisions of
that Act following the effective date of the first registration of any
securities of the Company on Form S-1 or any comparable or successor form.

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    SEPARATELY WITH THE COMMISSION.

                                       10
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         3.6 REGISTRATION PROCEDURES. If and whenever the Company is required by
the provisions of Section 3.3, 3.4 or 3.5 to endeavor to effect the registration
of any Registrable Securities under the Securities Act, the Company will, as
expeditiously as possible:

         (a) prepare and file with the Commission a registration statement
(which, in the case of an underwritten public offering pursuant to Section 3.3,
shall be on Form S-1 or other form of general applicability satisfactory to the
managing underwriter selected as therein provided) with respect to such
securities including executing an undertaking to file post-effective amendments
and use commercially reasonable efforts to cause such registration statement to
become and remain effective for the period of the distribution contemplated
thereby;

         (b) prepare and file with the Commission such amendments and
supplements to such registration statement and the prospectus used in connection
therewith as may be necessary to keep such registration statement effective for
the period specified herein and comply with the provisions of the Securities Act
with respect to the disposition of all Registrable Securities covered by such
registration statement in accordance with the sellers' intended method of
disposition set forth in such registration statement for such period;

         (c) furnish to each seller of Registrable Securities and to each
underwriter such number of copies of the registration statement and each such
amendment and supplement thereto (in each case including all exhibits) and the
prospectus included therein (including each preliminary prospectus) as such
persons reasonably may request in order to facilitate the public sale or other
disposition of the Registrable Securities covered by such registration
statement;

         (d) use commercially reasonable efforts to register or qualify the
Registrable Securities covered by such registration statement under the
securities or "blue sky" laws of such jurisdictions as the sellers of
Registrable Securities or, in the case of an underwritten public offering, the
managing underwriter reasonably shall request, PROVIDED, HOWEVER, that the
Company shall not for any such purpose be required to qualify generally to
transact business as a foreign corporation in any jurisdiction where it is not
so qualified or to consent to general service of process in any such
jurisdiction, unless the Company is already subject to service in such
jurisdiction;

         (e) use its best efforts to list the Registrable Securities covered by
such registration statement with any securities exchange on which the Common
Stock of the Company is then listed;

         (f) comply with all applicable rules and regulations under the
Securities Act and Exchange Act;

         (g) immediately notify each seller of Registrable Securities and each
underwriter under such registration statement, at any time when a prospectus
relating thereto is required to be delivered under the Securities Act, of the
happening of any event of which the Company has knowledge as a result of which
the prospectus contained in such registration statement, as then in effect,
includes an untrue statement of a material fact or omits to state a material
fact required to be stated therein or necessary to make the statements therein
not misleading in light of the circumstances then existing, and promptly prepare
and furnish to such seller a reasonable number of copies of a prospectus
supplemented or amended so that, as thereafter delivered to the purchasers of
such Registrable Securities, such prospectus shall not include an untrue
statement of a material fact or omit to state a material fact required to be
stated therein or necessary to make the statements therein not misleading in
light of the circumstances then existing;

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    SEPARATELY WITH THE COMMISSION.

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         (h) if the offering is underwritten and at the request of any seller of
Registrable Securities, use its best efforts to furnish on the date that
Registrable Securities are delivered to the underwriters for sale pursuant to
such registration: (i) an opinion dated such date of counsel representing the
Company for the purposes of such registration, addressed to the underwriters to
such effects as reasonably may be requested by counsel for the underwriters, and
(ii) a letter dated such date from the independent public accountants retained
by the Company, addressed to the underwriters in customary form in connection
with the proposed transaction;

         (i) make available for inspection by each seller of Registrable
Securities, any underwriter participating in any distribution pursuant to such
registration statement, and any attorney, accountant or other agent retained by
such seller or underwriter, reasonable access to all financial and other
records, pertinent corporate documents and properties of the Company, as such
parties may reasonably request, and cause the Company's officers, directors and
employees to supply all information reasonably requested by any such seller,
underwriter, attorney, accountant or agent in connection with such registration
statement;

         (j) cooperate with the selling holders of Registrable Securities and
the managing underwriter, if any, to facilitate the timely preparation and
delivery of certificates representing Registrable Securities to be sold, such
certificates to be in such denominations and registered in such names as such
holders or the managing underwriter may request at least two business days prior
to any sale of Registrable Securities;

         (k) permit any holder of Registrable Securities which holder, in the
sole and exclusive judgment, exercised in good faith, of such holder, might be
deemed to be a controlling person of the Company, to participate in good faith
in the preparation of such registration or comparable statement and to require
the insertion therein of material, furnished to the Company in writing, which in
the reasonable judgment of such holder and its counsel should be included; and

         (l) in the event of any underwritten public offering, enter into and
perform its obligations under an underwriting agreement, in usual and customary
form, with the managing underwriter of such offering.

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    SEPARATELY WITH THE COMMISSION.

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         For purposes of this Agreement, the period of distribution of
Registrable Securities in a firm commitment underwritten public offering shall
be deemed to extend until each underwriter has completed the distribution of all
securities purchased by it, and the period of distribution of Registrable
Securities in any other registration shall be deemed to extend until the earlier
of the sale of all Registrable Securities covered thereby or 120 days after the
effective date thereof, PROVIDED, HOWEVER, in the case of any registration of
Registrable Securities on Form S-3 or a comparable or successor form which are
intended to be offered on a continuous or delayed basis, such 120 day-period
shall be extended, if necessary, to keep the registration statement effective
until all such Registrable Securities are sold, provided that Rule 415, or any
successor rule under the Securities Act, permits an offering on a continuous or
delayed basis, and provided further that applicable rules under the Securities
Act governing the obligation to file a posteffective amendment, permit, in lieu
of filing a post-effective amendment which (y) includes any prospectus required
by Section 10(a)(3) of the Securities Act or (z) reflects facts or events
representing a material or fundamental change in the information set forth in
the registration statement, the incorporation by reference of information
required to be included in (y) and (z) above contained in periodic reports filed
pursuant to Section 13 or 15(d) of the Exchange Act in the registration
statement.

         In connection with each registration hereunder, the sellers of
Registrable Securities will furnish to the Company in writing such information
requested by the Company with respect to themselves and the proposed
distribution by them as shall be reasonably necessary in order to assure
compliance with Federal and applicable state securities laws.

         3.7 EXPENSES.

         (a) All expenses incurred by the Company in complying with Sections
3.3, 3.4 and 3.5, including, without limitation, all registration and filing
fees, printing expenses, fees and disbursements of counsel and independent
public accountants for the Company, fees and expenses (including counsel fees)
incurred in connection with complying with state securities or "blue sky" laws,
fees of the National Association of Securities Dealers, Inc., transfer taxes,
fees of transfer agents and registrars, costs of any insurance which might be
obtained by the Company with respect to the offering by the Company, and fees
and disbursements of one counsel selected by the holders of at least two-thirds
(2/3) of the Registrable Securities being sold, but excluding any Selling
Expenses, are called "Registration Expenses." All underwriting discounts and
selling commissions applicable to the sale of Registrable Securities are called
"Selling Expenses."

         (b) The Company will pay all Registration Expenses in connection with
each registration statement under Section 3.3, 3.4 or 3.5; provided, that, in
the event of a registration pursuant to Section 3.3 hereof which is withdrawn at
the request of the Investors other than (i) as a result of the Company's failure
to perform its obligations hereunder, (ii) as a result of a cutback by the
underwriter of such registration in the amount of Registrable Securities which
may be included in such registration by more than 10% or (iii) as a result of
information concerning a materially adverse change in the Company's business or
financial condition that is made known to the Investors after the date on which
such registration was requested, the Investors shall pay the Registration
Expenses with respect to such registration. In the event that a registration
pursuant to Section 3.3 hereof is withdrawn pursuant to clauses (i), (ii) or
(iii) of this Section 3.7(b), the Investors shall, immediately following such
withdrawal, be entitled to that number of registration requests pursuant to
Section 3.3 hereof to which they would have been entitled not taking into
account the withdrawn request. All Selling Expenses in connection with each
registration statement under Section 3.3, 3.4 or 3.5 shall be borne by the
participating sellers in proportion to the number of shares registered by each,
or by such participating sellers other than the Company (except to the extent
the Company shall be a seller) as they may agree.

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    SEPARATELY WITH THE COMMISSION.

                                       13
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         3.8 INDEMNIFICATION AND CONTRIBUTION.

         (a) In the event of a registration of any of the Registrable Securities
under the Securities Act pursuant to Section 3.3, 3.4 or 3.5, the Company will
indemnify and hold harmless each holder of Registrable Securities, its officers,
directors and partners, each underwriter of such Registrable Securities
thereunder and each other person, if any, who controls such holder or
underwriter within the meaning of the Securities Act (each, an "INDEMNITEE"),
against any losses, claims, damages or liabilities, joint or several, to which
such Indemnitee may become subject under the Securities Act or otherwise,
insofar as such losses, claims, damages or liabilities (or actions in respect
thereof) arise out of or are based upon (i) any untrue statement or alleged
untrue statement of any material fact contained in any prospectus, offering
circular or other document incident to such registration (including any related
notification, registration statement under which such Registrable Securities
were registered under the Securities Act pursuant to Section 3.3, 3.4 or 3.5,
any preliminary prospectus or final prospectus contained therein, or any
amendment or supplement thereof), (ii) any blue sky application or other
document executed by the Company specifically for that purpose or based upon
written information furnished by the Company filed in any state or other
jurisdiction in order to qualify any or all of the Registrable Securities under
the securities laws thereof (any such application, document or information
herein called a "BLUE SKY APPLICATION"), (iii) any omission or alleged omission
to state in any such registration statement, prospectus, amendment or supplement
or in any Blue Sky Applications executed or filed by the Company, a material
fact required to be stated therein or necessary to make the statements therein
not misleading, (iv) any violation by the Company or its agents of the
Securities Act or any rule or regulation promulgated under the Securities Act
applicable to the Company or its agents and relating to action or inaction
required of the Company in connection with such registration, or (v) any failure
to register or qualify the Registrable Securities in any state where the Company
or its agents has affirmatively undertaken or agreed in writing that the Company
(the undertaking of any underwriter chosen by the Company being attributed to
the Company) will undertake such registration or qualification (provided that in
such instance the Company shall not be so liable if it has used commercially
reasonable efforts to so register or qualify the Registrable Securities) and
will reimburse each Indemnitee for any legal or other expenses reasonably
incurred by them in connection with investigating or defending any such loss,
claim, damage, liability or action, promptly after being so incurred, PROVIDED,
HOWEVER, that the Company will not be liable to an Indemnitee if and to the
extent that any such loss, claim, damage or liability arises out of or is based
upon an untrue statement or alleged untrue statement or omission or alleged
omission so made in conformity with written information furnished by such
Indemnitee, in writing specifically for use in such registration statement or
prospectus.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       14
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         (b) In the event of a registration of any of the Registrable Securities
under the Securities Act pursuant to Section 3.3, 3.4 or 3.5, each seller of
such Registrable Securities thereunder, severally and not jointly, will
indemnify and hold harmless the Company, each person, if any, who controls the
Company within the meaning of the Securities Act, each officer of the Company
who signs the registration statement, each director of the Company, each other
seller of Registrable Securities, each underwriter and each person who controls
any underwriter within the meaning of the Securities Act, against all losses,
claims, damages or liabilities, joint or several, to which the Company or such
officer, director, other seller, underwriter or controlling person may become
subject under the Securities Act or otherwise, insofar as such losses, claims,
damages or liabilities (or actions in respect thereof) arise out of or are based
upon any untrue statement or alleged untrue statement of any material fact
contained in any prospectus offering circular or other document incident to such
registration (including any related notification, registration statement under
which such Registrable Securities were registered under the Securities Act
pursuant to Section 3.3, 3.4 or 3.5, any preliminary prospectus or final
prospectus contained therein, or any amendment or supplement thereof), or any
Blue Sky Application or arise out of or are based upon the omission or alleged
omission to state therein a material fact required to be stated therein or
necessary to make the statements therein not misleading, and will reimburse the
Company and each such officer, director, other seller, underwriter and
controlling person for any legal or other expenses reasonably incurred by them
in connection with investigating or defending any such loss, claim, damage,
liability or action, promptly after being so incurred, PROVIDED, HOWEVER, that
such seller will be liable hereunder in any such case if and only to the extent
that any such loss, claim, damage or liability arises out of or is based upon an
untrue statement or alleged untrue statement or omission or alleged omission
made in reliance upon and in conformity with information pertaining to such
seller, as such, furnished in writing to the Company by such seller specifically
for use in such registration statement or prospectus; and PROVIDED FURTHER,
HOWEVER, that the liability of each seller hereunder shall be limited to the
proportion of any such loss, claim, damage, liability or expense which is equal
to the proportion that the public offering price of the securities sold by such
seller under such registration statement bears to the total public offering
price of all securities sold thereunder, but not in any event to exceed the
proceeds received by such seller from the sale of Registrable Securities covered
by such registration statement. Not in limitation of the foregoing, it is
understood and agreed that the indemnification obligations of any seller
hereunder pursuant to any underwriting agreement entered into in connection
herewith shall be limited to the obligations contained in this subparagraph (b).

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       15
<Page>

         (c) Promptly after receipt by an indemnified party hereunder of notice
of the commencement of any action, such indemnified party shall, if a claim in
respect thereof is to be made against the indemnifying party hereunder, notify
the indemnifying party in writing thereof, but the omission so to notify the
indemnifying party shall not relieve it from any liability which it may have to
such indemnified party other than under this Section 3.8 and shall only relieve
it from any liability which it may have to such indemnified party under this
Section 3.8 if and to the extent the indemnifying party is prejudiced by such
omission. In case any such action shall be brought against any indemnified party
and it shall notify the indemnifying party of the commencement thereof, the
indemnifying party shall be entitled to participate in and, to the extent it
shall wish, to assume and undertake the defense thereof with counsel
satisfactory to such indemnified party, and, after notice from the indemnifying
party to such indemnified party of its election so to assume and undertake the
defense thereof, the indemnifying party shall not be liable to such indemnified
party under this Section 3.8 for any legal expenses subsequently incurred by
such indemnified party in connection with the defense thereof other than
reasonable costs of investigation and of liaison with counsel so selected,
PROVIDED, HOWEVER, that, if the defendants in any such action include both the
indemnified party and the indemnifying party and the indemnified party shall
have reasonably concluded that there may be reasonable defenses available to it
which are different from or additional to those available to the indemnifying
party or that the interests of the indemnified party reasonably may be deemed to
conflict with the interests of the indemnifying party, the indemnified party
shall have the right to select a separate counsel and to assume such legal
defenses and otherwise to participate in the defense of such action, with the
expenses and fees of such separate counsel and other expenses related to such
participation to be reimbursed by the indemnifying party as incurred. No
indemnifying party, in the defense of any such claim or action, shall, except
with the consent of each indemnified party, consent to entry of any judgment or
enter into any settlement which does not include as an unconditional term
thereof the giving by the claimant or plaintiff to such indemnified party of a
release from all liability in respect to such claim or action. Each indemnified
party shall furnish such information regarding itself or the claim in question
as an indemnifying party may reasonably request in writing and as shall be
reasonably required in connection with defense of such claim and litigation
resulting therefrom.

         (d) In order to provide for just and equitable contribution to joint
liability under the Securities Act in any case in which either (i) any holder of
Registrable Securities exercising rights under this Agreement, or any
controlling person of any such holder, makes a claim for indemnification
pursuant to this Section 3.8 but it is judicially determined (by the entry of a
final judgment or decree by a court of competent jurisdiction and the expiration
of time to appeal or the denial of the last right of appeal) that such
indemnification may not be enforced in such case notwithstanding the fact that
this Section 3.8 provides for indemnification in such case, or (ii) contribution
under the Securities Act may be required on the part of any such selling holder
or any such controlling person in circumstances for which indemnification is
provided under this Section 3.8; then, and in each such case, the Company and
such holder will contribute to the aggregate losses, claims, damages or
liabilities to which they may be subject (after contribution from others) in
such proportion so that such holder is responsible for the portion represented
by the percentage that the public offering price of its Registrable Securities
offered by the registration statement bears to the public offering price of all
securities offered by such registration statement, and the Company is
responsible for the remaining portion; PROVIDED, HOWEVER, that, in any such
case, (A) no such holder of Registrable Securities will be required to
contribute any amount in excess of the proceeds received from the sale of all
such Registrable Securities offered by it pursuant to such registration
statement; and (B) no person or entity guilty of fraudulent misrepresentation
(within the meaning of Section 11(f) of the Securities Act) will be entitled to
contribution from any person or entity who was not guilty of such fraudulent
misrepresentation.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       16
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         (e) The indemnities and obligations provided in this Section 3.8 shall
survive the transfer of any Registrable Securities by such holder.

         3.9 CHANGES IN COMMON STOCK. If, and as often as, there is any change
in the Common Stock by way of a stock split, stock dividend, combination or
reclassification, or through a merger, consolidation, reorganization or
recapitalization, or by any other means, appropriate adjustment shall be made in
the provisions hereof so that the rights and privileges granted hereby shall
continue with respect to the Common Stock as so changed.

         3.10 RULE 144 AND 144A REPORTING. With a view to making available the
benefits of certain rules and regulations of the Commission which may at any
time permit the sale of the Registrable Securities to the public without
registration, except as provided in paragraph (c) below, at all times after any
registration statement covering a public offering of securities of the Company
under the Securities Act shall have become effective, the Company agrees to:

         (a) use its best efforts to comply with all of the reporting
requirements of the Exchange Act (whether or not it shall be required to do so)
and shall comply with all other public information reporting requirements of the
Commission as a condition to the availability of an exemption from the
Securities Act for the sale of any of the Registrable Securities by any holder
of Registrable Securities (including any such exemption pursuant to Rule 144 or
Rule 144A thereof, as amended form time to time, or any successor rule thereto
or otherwise);

         (b) cooperate with each holder of Registrable Securities in supplying
such information as may be necessary for such holder of Registrable Securities
to complete and file any information reporting forms presently or hereafter
required by the Commission as a condition to the availability of an exemption
from the Securities Act (under Rule 144 or Rule 144A thereunder or otherwise)
for the sale of any of the Registrable Securities by any holder of Registrable
Securities; and

         (c) furnish to each holder of Registrable Securities forthwith upon
request a written statement by the Company as to its compliance with the
reporting requirements of such Rule 144 or Rule 144A (or any successor rule)
and, at any time after it has become subject to such reporting requirements, of
the Securities Act and the Exchange Act, a copy of the most recent annual or
quarterly report of the Company, and such other reports and documents so filed
by the Company as such holder may reasonably request in availing itself of any
rule or regulation of the Commission allowing such holder to sell any
Registrable Securities without registration.

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    SEPARATELY WITH THE COMMISSION.

                                       17
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3.11 "MARKET STAND-OFF" AGREEMENT. Each of the Investors agrees, severally and
not jointly, if requested by the Company and an underwriter of Common Stock (or
other securities) of the Company, not to sell or otherwise transfer or dispose
of any Common Stock (or other securities) of the Company held by such Purchaser
during a period not to exceed (i) one hundred and eighty (180) days following
the effective date of the first registration statement of the Company filed
under the Securities Act and (ii) ninety (90) days following the effective date
of any subsequent registration statement filed by the Company under the
Securities Act, and to enter into an agreement to such effect; PROVIDED that (y)
all persons including Shares in such offering and (z) all of the Company's
officers, directors and holders of at least 5% of the outstanding Common Stock
(or securities convertible into at least 5% of the Common Stock) also enter into
agreements to such effect.

         The Company may impose stop-transfer instructions with respect to the
shares (or securities) subject to the foregoing restriction until the end of
said period.

         3.12 LIMITATION ON SUBSEQUENT REGISTRATION RIGHTS. The Company shall
not, without the approval of the Board of Directors, including a majority of the
Preferred Stock Directors, grant to any third party any registration rights more
favorable than, or in any way conflicting with, any of those contained herein,
so long as any of the registration rights under this Agreement remains in
effect, provided, in any event, (i) any grant of demand or required registration
rights shall provide that the Purchasers have incidental or "piggyback"
registration rights with respect thereto in accordance with the provisions of
Section 3.4 hereof, and (ii) such rights shall not become effective prior to the
rights of the holders of Registrable Securities hereunder.

         3.13 ASSIGNMENT OF REGISTRATION RIGHTS. The rights to cause the Company
to register Registrable Securities pursuant to this Section 4 may be assigned
(but only with all related obligations) by a holder of Registrable Securities to
a transferee or assignee of such securities who is not engaged in a business
activity competitive with the Company (as reasonably determined by the Company's
Board of Directors) and who, after such assignment or transfer, holds at least
100,000 shares of Registrable Securities (subject to appropriate adjustment for
stock splits, stock dividends, combinations and similar recapitalization
events), provided the Company is, within a reasonable time after such transfer,
furnished with written notice of the name and address of such transferee or
assignee and the securities with respect to which such registration rights are
being assigned; and provided, further, that such assignment shall be effective
only if (i) immediately following such transfer the further disposition of such
securities by the transferee or assignee is restricted under the Act and (ii)
the transferee or assignee shall acknowledge in writing that the transferred or
assigned Registrable Securities shall remain subject to this Agreement. For the
purposes of determining the number of shares of Registrable Securities held by a
transferee or assignee, the holdings of transferees and assignees of a
partnership who are partners or retired partners of such partnership (including
spouses and ancestors, lineal descendants and siblings of such partners or
spouses who acquire Registrable Securities by gift, will or intestate
succession) shall be aggregated together and with the partnership; provided that
all assignees and transferees who would not qualify individually for assignment
of registration rights shall have a single attorney-in-fact for the purpose of
exercising any rights, receiving notices or taking any action under this
Section 3.

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    SEPARATELY WITH THE COMMISSION.

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         4.  BOARD OF DIRECTORS

         4.1 ELECTION OF DIRECTORS. From and after the date hereof, at any
annual or special stockholders meeting called for such purpose, and whenever the
stockholders of the Company act by written consent with respect to the election
of directors or at the request of any stockholder entitled to have taken any of
the actions specified below, each Investor and each Additional Holder agrees to
vote or otherwise give such Investor or Additional Holder's consent in respect
of all shares of capital stock of the Company (whether now or hereafter
acquired) owned by such Investor or Additional Holder or as to which such
Investor or Additional Holder is entitled to vote, and the Company shall take
all necessary and desirable actions within its control, in order to cause:

         (i) the authorized number of directors on the Board of Directors of the
     Company (the "Board") to be established at nine (9) directors as of the
     date hereof;

         (ii) subject to clause (iii) below, the election to the Board of (a)
     one director designated by the holders of the Series A Preferred Stock, (b)
     one director designated by the holders of the Series B Preferred Stock, (c)
     one director designated by the holders of the Series C Preferred Stock and
     (d) three (3) directors designated by the holders of the Series D
     Convertible Preferred Stock, which shall include (I) a designee of OrbiMed
     Advisors LLC ("OrbiMed"), initially Michael B. Sheffery, (II) a designee of
     one of the other Series D Purchasers and (III) an industry expert mutually
     acceptable to the directors designated pursuant to the preceding clauses
     (I) and (II) and a majority of the other directors then serving. The
     directors designated pursuant to this paragraph (ii) shall hold office,
     subject to their earlier removal in accordance with clause (iii) below,
     pursuant to the Bylaws of the Company and applicable corporate law, until
     their respective successors shall have been elected and shall have
     qualified;

         (iii) the removal from the Board (with or without cause) of any
     Preferred Stock Director upon the written request of a majority of the
     Preferred Stockholders entitled to designate such director;

         (iv) upon any vacancy in the Board as a result of any individual
     designated as provided in clause (ii) above ceasing to be a member of the
     Board, whether by resignation or otherwise, the election to the Board to
     fill such vacancy of an individual designated by the holder or holders of
     capital stock of the Company entitled to designate such Board seat pursuant
     to clause (ii) above;

         (v) the Board to maintain an Audit Committee and a Compensation
     Committee (which shall be responsible for, among other things, determining
     all executive salaries and other compensation), consisting solely of
     directors who are not employees of the Company;

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                                       19
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         (vi) the director designated by OrbiMed to act as a member of any
     committee of the Board, and, if such committee shall have in excess of
     three (3) members, to cause directors designated by the Series D Purchasers
     to constitute one-third of the members of such committee;

         (vii) directors designated by the Series D Purchasers to constitute
     one-third of the members of the board of directors of any subsidiary of the
     Company;

         (viii) a majority in interest of the Series D Purchasers to designate
     an individual to be granted observer status to attend but not to give their
     consent to vote at any meeting of the Board;

         (ix) the Company to compensate all non-employee directors equally, and
     in the same manner, except to the extent different levels of service are
     rendered to the Company;

         (x) the Company to hold meetings of the Board at least six times per
     calendar year; and

         (xi) the Company to indemnify all directors equally and to the fullest
     extent permitted by law and as set forth in the Company's Certificate of
     Incorporation and By-laws.

         4.2 TERMINATION. The provisions set forth in this Article 4 shall be of
no further force and effect upon the closing of the Company's Initial Public
Offering.

                  5.       AFFIRMATIVE COVENANTS OF THE COMPANY

         The Company covenants and agrees that, from the date of the Closing
under the Series D Purchase Agreement and thereafter so long as any Series D
Purchaser owns Registrable Securities, it will perform and observe the following
covenants and provisions, and will cause each Subsidiary, if and when such
Subsidiary exists, to perform and observe the following covenants and provisions
as applicable to such Subsidiary.

         5.1 FINANCIAL STATEMENTS; OTHER REPORTS. The Company and each
Subsidiary will maintain proper books of account and records in accordance with
generally accepted accounting principles applied on a consistent basis, and will
deliver to OrbiMed and any of its successors and assigns owning at least one
hundred thousand (100,000) shares of the Company's capital stock on a fully
diluted basis, treating all preferred stock on an as converted basis but
excluding any unexercised options, warrants or purchase rights (each, a "RIGHTS
HOLDER"):

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       20
<Page>

         (a) as soon as available and in any event within forty-five (45) days
after the end of each of the first three quarters of each fiscal year of the
Company, a consolidated balance sheet of the Company and its Subsidiaries as of
the end of such quarter and the related statements of income and stockholders'
equity and of cash flows of the Company for the period commencing at the end of
the previous fiscal year and ending with the end of such quarter, setting forth
in each case in comparative form the corresponding figures for the corresponding
period of the preceding fiscal year and the budget for such current year, all in
reasonable detail and prepared in accordance with generally accepted accounting
principles consistently applied, and duly certified (subject to year-end audit
adjustments) by the chief financial officer of the Company;

         (b) as soon as available and in any event within ninety (90) days after
the end of each fiscal year of the Company, a copy of the annual audit report
for such year for the Company, including therein a consolidated balance sheet of
the Company and its Subsidiaries as of the end of such fiscal year and
statements of income and stockholders' equity and of cash flows of the Company
for such fiscal year, setting forth in each case in comparative form the
corresponding figures for the preceding fiscal year, all duly certified by
independent public accountants of recognized standing acceptable to the Rights
Holders;

         (c) promptly upon receipt thereof, any written report submitted to the
Company by independent public accountants in connection with an annual or
interim audit of the books of the Company and its Subsidiaries made by such
accountants;

         (d) promptly after sending, making available, or filing the same, such
reports and financial statements as the Company shall send or make available to
the stockholders of the Company;

         (e) promptly after the commencement thereof, notice of all actions,
suits and proceedings before any court or governmental department, commission,
board, bureau, agency or instrumentality, domestic or foreign, affecting the
Company or its Subsidiaries, any technology or patent rights which it has or
they have, or any other assets of the Company or its Subsidiaries or any key
employee or officer (in their capacity as such);

         (f) promptly after the occurrence thereof and in any event within five
(5) business days after it becomes aware of each occurrence, notice of any
material adverse change in the business, assets, properties, management,
operations or financial condition of the Company or its Subsidiaries;

         (g) promptly upon becoming available: (i) copies of all financial
statements, minutes, reports, press releases, notices, proxy statements and
other documents sent by the Company to its Stockholders or released to the
public and copies of all regular and periodic reports, if any, filed by the
Company with the Commission or any securities exchange or self-regulatory
organization; and (ii) any other financial or other information available to
management of the Company that any of the Purchasers shall have reasonably
requested on a timely basis; and

         (h) by the 15th day of the 2001 fiscal year, and at least 45 days prior
to the beginning of each subsequent fiscal year, of the Company, an operating
plan with monthly and quarterly breakdowns (the "Budget") for each fiscal year,
which the Company shall be required to prepare and submit to the Board. The
Budget shall be deemed accepted as the Budget for such fiscal year only when it
has been approved by the Board. The Budget shall be reviewed by the Company
periodically and all changes therein, and all material deviations therefrom,
shall be reviewed by the Board on at least a quarterly basis.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       21
<Page>

         Neither the foregoing provisions of this Section nor any other
provision of this Agreement shall be in limitation of any rights which a
Purchaser may have with respect to the books and records of the Company and its
Subsidiaries, or to inspect their properties or discuss their affairs, finances
and accounts, under the laws of the jurisdictions in which they are
incorporated.

         5.2 INSPECTION AND OTHER INFORMATION. Each Rights Holder and such
agents, advisors and counsel as such Rights Holder may designate, may, at its
expense, visit and inspect any of the properties of the Company and each
Subsidiary, examine the books of account of the Company and each Subsidiary,
take extracts therefrom and discuss the affairs, finances and accounts of the
Company and each Subsidiary with its officers and employees and public
accountants (and by this provision the Company and each Subsidiary hereby
authorizes said accountants to discuss with such Rights Holder and such persons
its finances and accounts), at reasonable times and with reasonable prior notice
during normal business hours. All such visits and inspections shall be conducted
in a manner which will not unreasonably interfere with the normal business
operations of the Company and each Subsidiary. The Company and each Subsidiary
will furnish to each such Rights Holder such other information as it from time
to time may reasonably request.

         5.3 INDEPENDENT ACCOUNTANTS. The Company will retain Arthur Andersen
LLP or such other independent public accountants of recognized national standing
approved by the Company's Board of Directors who shall certify the Company's
consolidated financial statements at the end of each fiscal year. In the event
the services of the independent public accountants, so selected, or any firm of
independent public accountants hereafter employed by the Company are terminated,
the Company will promptly thereafter notify the Rights Holders and will request
the firm of independent public accountants whose services are terminated to
deliver to the Rights Holders a letter of such firm setting forth the reasons
for the termination of their services. In the event of such termination, the
Company will promptly thereafter engage another such firm of independent public
accountants. In its notice to the Rights Holders, the Company shall state
whether the change of accountants was recommended or approved by the Board of
Directors or any committee thereof.

         5.4 MAINTENANCE OF INSURANCE. The Company and each Subsidiary will
maintain insurance with financially sound and reputable insurance companies or
associations in such amounts and covering such risks as is usually carried by
companies engaged in similar businesses and owning similar properties in the
same general areas in which the Company operates, including, without limitation,
directors' and officers' liability insurance.

         5.5 EMPLOYEE AGREEMENTS. The Company shall and shall cause its
subsidiaries (if any) to obtain an employee agreement covering nondisclosure of
confidential information and assignment of inventions in the form of Exhibit C-1
attached to the Series D Purchase Agreement and a non-competition agreement in
the form of Exhibit C-2 attached to the Series D Purchase Agreement from each of
its existing and future officers, employees and consultants.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       22
<Page>

         5.7 PRESERVATION OF CORPORATE EXISTENCE. The Company and each
Subsidiary will preserve and maintain its corporate existence, rights,
franchises and privileges in the jurisdiction of its incorporation, and qualify
and remain qualified, as a foreign corporation in each jurisdiction in which
such qualification is necessary or desirable in view of its business and
operations or the ownership of its properties. The Company and each Subsidiary
shall preserve and maintain all licenses and other rights to use patents,
processes, licenses, trademarks, trade names, inventions. Intellectual Property
Rights or copyrights owned or possessed by it and necessary to the conduct of
its business.

         5.8 COMPLIANCE WITH LAWS. The Company will comply, and cause each of
its Subsidiaries to comply, with all applicable laws, rules, regulations and
orders of any governmental authority, noncompliance with which could materially
adversely affect its business or condition, financial or otherwise.

         5.9 COMPENSATION. SCHEDULE 1 hereto lists each officer and key employee
of the Company and sets forth each such officers and key employee's current
compensation and anticipated compensation during 2001. For purposes hereof
"compensation" shall include base salary, bonuses, car allowances and other cash
benefits, and stock option and other equity incentive awards.

         5.10 NEW DEVELOPMENTS. The Company and each Subsidiary will cause all
technological developments, patentable or unpatentable inventions, discoveries
or improvements by their officers, employees or consultants to be documented in
accordance with appropriate professional standards and cause all officers,
employees and consultants to file and execute United States and foreign patent
or copyright applications relating to and protecting such developments on behalf
of the Company or such Subsidiary or take such other actions as may be necessary
to confirm the Company's or such Subsidiary's sole ownership of such
intellectual property and to adequately protect such intellectual property.

         5.11 MEETINGS OF DIRECTORS AND COMMITTEES; EXPENSES OF DIRECTORS. The
Company shall hold meetings of the Company's Board of Directors not less
frequently than six times during any calendar year. The Company shall promptly
reimburse in full each director of the Company for all of his or her reasonable
out-of-pocket expenses incurred in attending each meeting of the Board of
Directors of the Company or any committee thereof or in connection with any
special project. Except for meetings held in either Boston or New York City and
on not less than 30 days' written notice to all directors, no action shall be
taken at any meeting unless at least two Series D Preferred Stock Directors (or
such lesser number are then in office) are present at such meeting.

         5.12 PROMPT PAYMENT OF TAXES, ETC. The Company and each Subsidiary will
promptly pay and discharge, or cause to be paid and discharged, when due and
payable, all lawful taxes, assessments and governmental charges or levies
imposed upon the income, profits, property or business of the Company or any
Subsidiary; PROVIDED, HOWEVER, that any such tax, assessment, charge or levy
need not be paid if the validity thereof shall currently be contested in good
faith by appropriate proceedings and if the Company or such Subsidiary shall
have set aside on its books adequate reserves with respect thereto, and
provided, further, that the Company and each Subsidiary will pay all such taxes,
assessments, charges or levies forthwith upon the commencement of proceedings to
foreclose any Lien which may have attached as security therefor. The Company and
each Subsidiary will promptly pay or cause to be paid when due, or in
conformance with customary trade terms, all other Indebtedness incident to
operations of the Company and each Subsidiary.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       23
<Page>

         5.13 MAINTENANCE OF PROPERTIES AND LEASES. The Company will keep its
properties and those of its Subsidiaries in good repair, working order and
condition, reasonable wear and tear excepted, and from time to time make all
needful and proper repairs, renewals, replacements, additions and improvements
thereto; and the Company and its Subsidiaries will at all times comply with each
provision of all leases to which any of them is a party or under which any of
them occupies property if the breach of such provision might have a material
adverse effect on the condition, financial or otherwise, or operations of the
Company or such Subsidiary.

         5.14 COMPLIANCE WITH AGREEMENTS. The Company and all of its
Subsidiaries shall duly comply with all of the provisions of the contracts,
obligations, agreements, plans, arrangements and commitments to which any of
them is a party or by which any of them is bound.

         5.15 AVAILABILITY OF COMMON STOCK. The Company will, from time to time,
in accordance with the laws of the State of Delaware, increase the authorized
amount of Common Stock if at any time the number of shares of Common Stock
remaining unissued and available for issuance shall be insufficient to permit
conversion of all then outstanding shares of Preferred Stock.

         5.16 STOCK DISPOSITIONS. The Company shall cause each person who has
been or in the future is granted any options to acquire shares of capital stock
of the Company to enter into a stock option agreement with the Company in the
form of Exhibit B hereto.

         5.17 WAIVERS UNDER EXISTING STOCKHOLDER AGREEMENT. The Company shall
(i) on or prior to January 31, 2001, cause each of its securityholders (other
than securityholders holding no more than 10,000 shares of Common Stock,
determined on a fully exercised and converted basis) that are party to the
Company's Stockholder Agreement dated as of March 13, 1997 (the "Stockholder
Agreement") to execute a waiver of such securityholder's rights under Sections
1.a, 2.b, 3 and 4.c of the Stockholder Agreement in the form attached hereto as
Exhibit C, (ii) use its best efforts to cause all securityholders that are party
to the Stockholder Agreement to execute such a waiver as soon as is practicable
and (iii) not permit any additional securityholders to become parties to the
Stockholder Agreement on or after the date hereof.

         5.18 TERMINATION OF AFFIRMATIVE COVENANTS. The covenants set forth in
this Article 5 shall be of no further force or effect upon the closing of the
Company's Initial Public Offering.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       24
<Page>

                  6.       NEGATIVE COVENANTS

         Without limiting any other covenants or provisions hereof, the Company
covenants and agrees that it will comply with and observe the following negative
covenants and provisions, and will cause each Subsidiary to comply with and
observe such of the following covenants and provisions as are applicable to such
Subsidiary, if and when such Subsidiary exists, and will not, without first
having obtained the affirmative vote or written consent of the holders of at
least a majority of the outstanding shares of Series D Preferred Stock, do any
of the actions set forth in the following covenants and provisions:

         6.1 BUSINESS. The Company will not engage in any business other than
the business of research, development, production and marketing of
pharmaceutical products.

         6.2 MERGER AND SALE OF ASSETS; LIQUIDATION AND DISSOLUTION. The Company
will not merge or consolidate with any other Person or sell, assign, lease or
otherwise dispose of all or substantially all of its assets, in one transaction
or in a series of transactions, nor dissolve or liquidate the Company.

         6.3 AMENDMENTS TO CHARTER AND BY-LAWS. The Company will not amend,
alter or repeal any provision of, or add any provision to, its Certificate of
Incorporation or By-laws or otherwise alter or change the preferences, rights,
privileges or powers of, or the restrictions provided for the benefit of, the
Preferred Stock.

         6.4 DISTRIBUTIONS; SECTION 305. Neither the Company nor any Subsidiary
will purchase, redeem, retire, or otherwise acquire for value any shares of its
capital stock (or rights, options or warrants to purchase such shares) now or
hereafter outstanding, return any capital to its stockholders (such transactions
being hereinafter referred to as "DISTRIBUTIONS"), and neither the Company nor
any Subsidiary shall declare or pay any dividends or make any distribution of
assets to its stockholders as such, except for (i) dividends on the Preferred
Stock paid out of earnings; or (ii) repurchases of shares of Common Stock held
by employees, consultants, directors, or officers of the Company that are
subject to stock repurchase agreements under which the Company has the right to
repurchase such shares in the event of termination of employment.

         6.5 DEALINGS WITH AFFILIATES. Except for existing agreements described
in SCHEDULE 2.21 to the Series D Purchase Agreement, neither the Company nor any
Subsidiary will enter into any transaction or agreement other than
indemnification and employment transactions in the ordinary course of the
Company's business with any employee, officer or director or any member of their
families, or any corporation or other entity in which any one or more of such
persons holds, directly or indirectly, five percent (5%) or more of any class of
capital stock, or with any other Affiliate of the Company, except agreements and
transactions on terms no less favorable to the Company or any Subsidiary than it
would obtain in a transaction between unrelated parties, and then only if such
agreements or transactions are approved by the disinterested members of the
Board of Directors.

         6.6 TRANSFERS OF TECHNOLOGY. Neither the Company nor any Subsidiary
will transfer any ownership or interest in, or material rights relating to, any
of its Intellectual Property Rights to any Person, except as approved by the
Board of Directors.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       25
<Page>

         6.7 RESTRICTIVE AGREEMENTS PROHIBITED. Neither the Company nor any of
its Subsidiaries shall become a party to any agreement which by its terms
restricts the Company's performance of its obligations pursuant to the terms of
this Agreement, the Series D Purchase Agreement, or the provisions relating to
the Series D Stock included in the Second Amended and Restated Certificate of
Incorporation, including, but not limited to, registration rights and the
payment of dividends on, the redemption, voting or conversion of the Series D
Stock, PROVIDED, HOWEVER, that nothing in this Section 6.7 shall prohibit any
amendment of or waiver of any provision of this Agreement or any of the
foregoing agreements or the Second Amended and Restated Certificate of
Incorporation, if such amendment or waiver is in accordance with the applicable
provisions of this Agreement and other applicable law.

         6.8 MERGERS, SALE OF ASSETS, ETC. OF SUBSIDIARIES. The Company shall
not permit any Subsidiary to consolidate or merge into or with or sell or
transfer all or substantially all its assets, except that any Subsidiary may (i)
consolidate or merge into or with or sell or transfer assets to any other
Subsidiary, or (ii) merge into or sell or transfer assets to the Company.

         6.9 MAINTENANCE OF OWNERSHIP OF SUBSIDIARIES. The Company shall not
sell or otherwise transfer any shares of capital stock of any Subsidiary, except
to the Company or another Subsidiary, or permit any Subsidiary to issue, sell or
otherwise transfer any shares of its capital stock or the capital stock of any
Subsidiary, except to the Company or another Subsidiary.

         6.10 SECURITIES OF OTHER PERSONS. Except for short-term investments in
highly rated instruments, money market funds, bank certificates of deposit or
similar low risk securities, neither the Company nor any Subsidiary shall
purchase any stock or other securities of any Person, unless such Person is
wholly-owned.

         6.11 U.S. REAL PROPERTY HOLDING CORPORATION. The Company will not be a
"United States real property holding corporation," as defined in Section
897(c)(2) of the Code and Section 1.897-2(b) of the Regulations promulgated by
the Internal Revenue Service and upon written request, will provide to any
holder of Registrable Securities a statement to the effect informing such holder
whether such interest constitutes a U.S. real property interest.

         6.12 STOCK AND OPTION AGREEMENTS. The Company will not issue Common
Stock or stock options to its officers, directors, employees or others who
render services to the Company except (A) pursuant to the Company's Employee,
Director and Consultant Stock Option Plan in an aggregate amount not exceeding
5,125,000 shares of Common Stock (including all previously issued options) or
such greater number of shares of Common Stock as approved by the Board of
Directors, or (B) pursuant to any other stock option plan approved by the Board
of Directors. The Company will not amend or modify the Company's Employee,
Director and Consultant Stock Option Plan, or otherwise enact a new stock option
plan without the approval of the Board of Directors.

         6.13 TERMINATION OF NEGATIVE COVENANTS. The covenants set forth in this
Article 6 shall be of no further force or effect upon the closing of the
Company's Initial Public Offering.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       26
<Page>

                  7.       MISCELLANEOUS

         7.1 NOTICES. All notices, requests, consents and other communications
hereunder shall be in writing, shall be addressed to the receiving party's
address set forth below or to such other address as a party may designate by
notice hereunder, and shall be either (i) delivered by hand, (ii) made by
telecopy or facsimile transmission, (iii) sent by overnight courier, or (iv)
sent by registered or certified mail, return receipt requested, postage prepaid.

    If to the Company:         NeoGenesis Drug Discovery, Inc.
                                          840 Memorial Drive
                                          Cambridge, MA 02139
                                          Attn: David Hunter, CFO
                                          617-868-1500 (Telephone)
                                          617-868-1515 (Fax)

                      With a copy to:     Bingham Dana LLP
                                          150 Federal Street
                                          Boston, MA 02110
                                          Attn: John J. Concannon III, Esq.
                                          617-951-8000 (Telephone)
                                          617-951-8736 (Fax)

            If to the Purchasers:      To the addresses set forth on Exhibit A

                      With a copy, in the case of a notice to OrbiMed, to:

                                          Wollmuth Maher & Deutsch LLP
                                          500 Fifth Avenue, 12th Floor
                                          New York, New York 10110
                                          Attn: Kenneth G. Alberstadt, Esq.
                                          (212) 382-3300 (Telephone)
                                          (212) 382-0050 (Fax)

         All notices, requests, consents and other communications hereunder
shall be deemed to have been given either (i) if by hand, at the time of the
delivery thereof to the receiving party at the address of such party set forth
above, (ii) if made by telecopy or facsimile transmission, at the time that
receipt thereof has been acknowledged by electronic confirmation or otherwise,
(iii) if sent by overnight courier, on the next business day following the day
such notice is delivered to the courier service, or (iv) if sent by registered
or certified mail, on the fifth business day following the day such mailing is
made.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       27
<Page>

         7.2 ENTIRE AGREEMENT; EFFECTIVENESS. This Agreement embodies the entire
agreement and understanding between the parties hereto with respect to the
subject matter hereof and supersedes all prior oral or written agreements and
understandings relating to the subject matter hereof. No statement,
representation, warranty, covenant or agreement of any kind not expressly set
forth in this Agreement shall affect, or be used to interpret, change or
restrict, the express terms and provisions of this Agreement. This Agreement
shall become effective upon its execution by the Company, each of the Series D
Purchasers (other than any investment funds managed by or affiliated with [Fort
Washington], which shall be entitled to become a party hereto upon the closing
of their respective investments in the Series D Stock) and additional
stockholders representing, together with the Series D Purchasers who have then
executed this Agreement, at least a majority of the voting power of the
outstanding capital stock of the Company determined on a fully diluted basis.
The Company shall use its best efforts to cause all of the other stockholders
intended to become parties hereto, to execute this Agreement as soon as
practicable thereafter.

         7.3 MODIFICATIONS AND AMENDMENTS. This Agreement may not be amended or
modified, and no provision hereof may be waived, without the written consent of
the Company and the holders of at least a majority of the outstanding shares of
Preferred Stock (including the holders of at least a majority of the outstanding
shares of Series D Preferred Stock). Any waiver or consent hereunder shall be
effective only in the specific instance and for the purpose for which it was
given, and shall not constitute a continuing waiver or consent.

         7.4 ASSIGNMENT. The rights and obligations under this Agreement may not
be assigned by the Company without the prior written consent of at least a
majority of the holders of Registrable Securities, unless specifically permitted
by the terms hereof.

         7.5 BENEFIT. All statements, representations, warranties, covenants and
agreements in this Agreement shall be binding on the parties hereto and shall
inure to the benefit of the respective successors and permitted assigns of each
party hereto. Nothing in this Agreement shall be construed to create any rights
or obligations except among the parties hereto, and no person or entity shall be
regarded as a third-party beneficiary of this Agreement.

         7.6 GOVERNING LAW. This Agreement and the rights and obligations of the
parties hereunder shall be construed in accordance with and governed by the law
of the State of Delaware, without giving effect to the conflict of law
principles thereof.

         7.7 JURISDICTION AND SERVICE OF PROCESS. Any legal action or proceeding
with respect to this Agreement shall be brought in the courts of the State of
New York or of the United States of America for the District of New York. By
execution and delivery of this Agreement, each of the parties hereto accepts for
itself and in respect of its property, generally and unconditionally, the
jurisdiction of the aforesaid courts. Each of the parties hereto irrevocably
consents to the service of process of any of the aforementioned courts in any
such action or proceeding by the mailing of copies thereof by certified mail,
postage prepaid, to the party at its address set forth in Section 7.1 hereof.

         7.8 SEVERABILITY. In the event that any court of competent jurisdiction
shall determine that any provision, or any portion thereof, contained in this
Agreement shall be unenforceable in any respect, then such provision shall be
deemed limited to the extent that such court deems it enforceable, and as so
limited shall remain in full force and effect. In the event that such court
shall deem any such provision, or portion thereof, wholly unenforceable, the
remaining provisions of this Agreement shall nevertheless remain in full force
and effect.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       28
<Page>

         7.9 INTERPRETATION. The parties hereto acknowledge and agree that: (i)
each party and its counsel reviewed and negotiated the terms and provisions of
this Agreement and have contributed to its revision; (ii) the rule of
construction to the effect that any ambiguities are resolved against the
drafting party shall not be employed in the interpretation of this Agreement;
and (iii) the terms and provisions of this Agreement shall be construed fairly
as to all parties hereto and not in favor of or against any party, regardless of
which party was generally responsible for the preparation of this Agreement.

         7.10 HEADINGS AND CAPTIONS. The headings and captions of the various
subdivisions of this Agreement are for convenience of reference only and shall
in no way modify or affect the meaning or construction of any of the terms or
provisions hereof.

         7.11 ENFORCEMENT. Each of the parties hereto acknowledges and agrees
that the rights acquired by each party hereunder are unique and that irreparable
damage would occur in the event that any of the provisions of this Agreement to
be performed by the other parties were not performed in accordance with their
specific terms or were otherwise breached. Accordingly, in addition to any other
remedy to which the parties hereto are entitled at law or in equity, each party
hereto shall be entitled to an injunction or injunctions to prevent breaches of
this Agreement by any other party and to enforce specifically the terms and
provisions hereof in any federal or state court to which the parties have agreed
hereunder to submit to jurisdiction.

         7.12 NO WAIVER OF RIGHTS, POWERS AND REMEDIES. No failure or delay by a
party hereto in exercising any right, power or remedy under this Agreement, and
no course of dealing among the parties hereto, shall operate as a waiver of any
such right, power or remedy of the party. No single or partial exercise of any
right, power or remedy under this Agreement by a party hereto, nor any
abandonment or discontinuance of steps to enforce any such right, power or
remedy, shall preclude such party from any other or further exercise thereof or
the exercise of any other right, power or remedy hereunder. The election of any
remedy by a party hereto shall not constitute a waiver of the right of such
party to pursue other available remedies. No notice to or demand on a party not
expressly required under this Agreement shall entitle the party receiving such
notice or demand to any other or further notice or demand in similar or other
circumstances or constitute a waiver of the rights of the party giving such
notice or demand to any other or further action in any circumstances without
such notice or demand.

         7.13 COUNTERPARTS. This Agreement may be executed in one or more
counterparts, and by different parties hereto on separate counterparts, each of
which shall be deemed an original, but all of which together shall constitute
one and the same instrument.

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       29
<Page>

         IN WITNESS WHEREOF, the parties hereto have executed this Agreement or
caused this Agreement to be executed by their duly authorized representatives;
as of the date first written above.

                            NEOGENESIS DRUG DISCOVERY, INC.

                            By:    /s/ Satish Jindal, Ph.D.
                                 -----------------------------------------------
                                  Name:  Satish Jindal, Ph.D.
                                  Title:  President

                            SERIES A STOCKHOLDERS:

                              /s/ Allen H. Michels
                            ----------------------------------------------------
                            Allen H. Michels

                            TGJ TRUST

                              /s/ Theodore G. Johnson
                            ----------------------------------------------------
                            By:  Theodore G. Johnson, its Trustee

                              /s/ Christopher J. Ainley
                            ----------------------------------------------------
                            Christopher J. Ainley

                            Tenants in the Entirety:

                              /s/ Claude E. Wintner
                            ----------------------------------------------------
                            Claude E. Wintner

                              /s/ Martha C. Wintner
                            ----------------------------------------------------
                            Martha C. Wintner

                            Tenants in Common:

                              /s/ Mark Birnbaum
                            ----------------------------------------------------
                            Mark Birnbaum

                              /s/ Evelyn Birnbaum
                            ----------------------------------------------------
                            Evelyn Birnbaum

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       30
<Page>

                            SERIES B STOCKHOLDERS:

                              /s/ Theodore G. Johnson
                            ----------------------------------------------------
                            Theodore G. Johnson

                            TGJ TRUST

                              /s/ Theodore G. Johnson
                            ----------------------------------------------------
                            Theodore G. Johnson, its Trustee

                              /s/ Christopher J. Ainley
                            ----------------------------------------------------
                            Christopher J. Ainley

                              /s/ James Wade
                            ----------------------------------------------------
                            James Wade

                              /s/ Charles A. Sanders
                            ----------------------------------------------------
                            Charles A. Sanders

                              /s/ Jiro Abe
                            ----------------------------------------------------
                            Jiro Abe

                            FREYA FANNING & CO.

                            By:  /s/ Thomas B. Hallowell
                               -------------------------------------------------
                                 Name: Thomas B. Hallowell
                                 Its:  General Partner

                            ----------------------------------------------------
                            Peter B. Loring

                            SERIES C STOCKHOLDERS:

                            FREYA FANNING & CO.

                            By:  /s/ Thomas B. Hallowell
                               -------------------------------------------------
                                 Name:  Thomas B. Hallowell
                                 Its:   General Partner

                              /s/ Jason T. Kuplen
                            ----------------------------------------------------
                            Jason T. Kuplen

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       31
<Page>

                              /s/ Robert A. Gough, Jr.
                            ----------------------------------------------------
                            Robert A. Gough, Jr.

                            NEOGENESIS DRUG DISCOVERY, INC.
                            SERIES D PREFERRED INVESTMENT TRUST

                            By:
                               -------------------------------------------------
                                 Name:
                                 Its:

                            Morash Family L.P.

                              /s/ Richard Morash
                            ----------------------------------------------------
                            By:  Richard Morash
                            Its: General Partner

                            CONSTANTIN VON WENTZEL TRUST

                            By:
                               -------------------------------------------------
                                 Name:
                                 Its:

                              /s/ Thomas B. Hallowell
                            ----------------------------------------------------
                            Thomas B. Hallowell

                              /s/ Theodore G. Johnson
                            ----------------------------------------------------
                            Theodore G. Johnson

                              /s/ David L. Engel
                            ----------------------------------------------------
                            David L. Engel

                              /s/ Justin P. Morreale
                            ----------------------------------------------------
                            Justin P. Morreale

                              /s/ Victor J. Paci
                            ----------------------------------------------------
                            Victor J. Paci

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       32
<Page>

                            SERIES D PURCHASERS:

                            CADUCEUS PRIVATE INVESTMENTS, LP
                            By OrbiMed Capital, LLC, its General Partner

                            By:  /s/ Eric A. Bittelman
                               -------------------------------------------------
                                 Name:  Eric A. Bittelman
                                 Title: Chief Financial Officer

                            ORBIMED ASSOCIATES, LLC
                            By OrbiMed Advisors LLC, its Managing Member

                            By:  /s/ Eric A. Bittelman
                               -------------------------------------------------
                                 Name:  Eric A. Bittelman
                                 Title: Chief Financial Officer

                            PW JUNIPER CROSSOVER FUND, L.L.C.
                            By PW Juniper Management, L.L.C., its
                            Investment Advisor

                            By OrbiMed Advisors, Inc., a Member

                            By:  /s/ ERIC A. BITTELMAN
                               -------------------------------------------------
                                 Name:  Eric A. Bittelman
                                 Title: Chief Financial Officer

                            FINSBURY WORLDWIDE PHARMACEUTICAL TRUST PLC
                            By OrbiMed Advisors, LLC, its Investment Advisor

                            By:  /s/ Eric A. Bittelman
                               -------------------------------------------------
                                 Name:  Eric A. Bittelman
                                 Title: Chief Financial Officer

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       33
<Page>

                            FORT WASHINGTON PRIVATE EQUITY INVESTORS II, L.P.
                            By:  Fort Washington Capital Partners, LLC,
                            General Partner

                            By:    Fort Washington Investment Advisors, Inc.,
                                   Managing Member

                            By:  /s/ William F.  Ledwin
                               -------------------------------------------------
                                 Name:  William F. Ledwin
                                 Title: President

                            By:  /s/ John O"Connor
                               -------------------------------------------------
                                 Name:  John O'Connor
                                 Title: Director of Private Equity

                            FORT WASHINGTON PRIVATE EQUITY INVESTORS III, L.P.
                            By:  Fort Washington Capital Partners, LLC,
                            General Partner

                            By:    Fort Washington Investment Advisors, Inc.,
                                   Managing Member

                            By:  /s/ William F.  Ledwin
                               -------------------------------------------------
                                 Name:  William F. Ledwin
                                 Title: President

                            By:  /s/ John O"Connor
                               -------------------------------------------------
                                 Name:  John O'Connor
                                 Title: Director of Private Equity

                            ORBIMED ADVISORS LLC

                            By:  /s/ Eric A. Bittelman
                               -------------------------------------------------
                                 Name:  Eric A. Bittelman
                                 Title: Chief Financial Officer

                            FREYA FANNING & CO.

                            By:  /s/ Thomas B Hallowell
                               -------------------------------------------------
                                 Name:  Thomas B Hallowell
                                 Title: General Partner

                              /s/ Theodore G. Johnson
                            ----------------------------------------------------
                            Theodore G. Johnson

                              /s/ Guy M. Rochman
                            ----------------------------------------------------
                            Guy M. Rochman

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       34
<Page>

                              /s/ Justin P. Morreale
                            ----------------------------------------------------
                            Justin P. Morreale

                              /s/ David L. Engel
                            ----------------------------------------------------
                            David L. Engel

                              /s/ Victor J. Paci
                            ----------------------------------------------------
                            Victor J. Paci

                              /s/ John J. Concannon III
                            ----------------------------------------------------
                            John J. Concannon III

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                                35
<Page>

                            COMMON STOCKHOLDERS:

                              /s/ Allen H. Michels
                            ----------------------------------------------------
                            Allen H. Michels

                              /s/ Satish Jindal
                            ----------------------------------------------------
                            Satish Jindal

                              /s/ Richard Young
                            ----------------------------------------------------
                            Richard Young

                              /s/ Seth N. Birnbaum
                            ----------------------------------------------------
                            Seth N. Birnbaum

                              /s/ Krishna Khalghatgi
                            ----------------------------------------------------
                            Krishna Khalghatgi

                              /s/ Edward Wintner
                            ----------------------------------------------------
                            Edward Wintner

                              /s/ Gerald Shipps
                            ----------------------------------------------------
                            Gerald Shipps

                              /s/ William H. Lee
                            ----------------------------------------------------
                            William H. Lee

                            Wolverine Limited Partnership

                            By:  /s/ Theodore G. Johnson
                               -------------------------------------------------
                            Name:  Theodore G. Johnson
                            Title: General Partner

                            ----------------------------------------------------
                            Cheryl Stuntz

                            ----------------------------------------------------
                            Jennifer Mosier

                            The Key Trust

                            By:  /s/ Thomas B. Hallowell
                               -------------------------------------------------
                                 Name:  Thomas B. Hallowell
                                 Title: Trustee

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       36
<Page>

                              /s/ Kathleen Amy Kipp
                            ----------------------------------------------------
                            Kathleen Amy Kipp

                              /s/ Tomas Revesz
                            ----------------------------------------------------
                            Tomas Revesz

                              /s/ Blair Kreppein
                            ----------------------------------------------------
                            Blair Kreppein

                             /s/ David Rezendes
                            ----------------------------------------------------
                            David Rezendes

                              /s/ Jean-Paul Orminati
                            ----------------------------------------------------
                            Jean-Paul Orminati

                              /s/ Doris A. Pensky
                            ----------------------------------------------------
                            Doris A. Pensky

                              /s/ Benjamin E. Birnbaum
                            ----------------------------------------------------
                            Benjamin E. Birnbaum

                            ----------------------------------------------------
                            Daniela Homuth-Trombino

                            /s/ Ciamac Moallemi
                            ----------------------------------------------------
                            Ciamac Moallemi

                              /s/ Huw M. Nash, Ph.D.
                            ----------------------------------------------------
                            Huw M. Nash, Ph.D.

                              /s/ Stephen F. Anderson
                            ----------------------------------------------------
                            Stephen F. Anderson

                              /s/ Kristin E. Rosner
                            ----------------------------------------------------
                            Kristin E. Rosner

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       37
<Page>

                              /s/ Nehal Patel
                            ----------------------------------------------------
                            Nehal Patel

                              /s/ Andrew N. Tyler
                            ----------------------------------------------------
                            Andrew N. Tyler

                              /s/ Janine M. Kayser
                            ----------------------------------------------------
                            Janine M. Kayser

* = CONFIDENTIAL TREATMENT REQUESTED: MATERIAL HAS BEEN OMITTED AND FILED
    SEPARATELY WITH THE COMMISSION.

                                       38

<PAGE>

                                 AMENDMENT #1 TO
                            INVESTOR RIGHTS AGREEMENT

         This Amendment #1 (this "Amendment") is dated as of November 14, 2001
and is the first amendment to the Investor Rights Agreement, dated as of
December 27, 2000 (the "Investor Rights Agreement"), by and among NeoGenesis
Drug Discovery, Inc. a Delaware Corporation (the "Company"), and the Investors
as such term is defined therein.

         WHEREAS, the Company intends to make an initial public offering ("IPO")
of shares of its common stock, $.001 par value per share;

         WHEREAS, the Investors and the Company desire to amend the Investors
Rights Agreement to facilitate the IPO and agree that this Amendment will be
mutually beneficial;

         NOW, THEREFORE, in consideration of the premises and the mutual
promises herein contained, the parties hereto hereby agree as follows:

         1. AMENDMENT OF SECTION 1.3. Effective of the date first written above,
Section 1.3 is hereby amended by deleting of the definition of "Initial Public
Offering" and replacing in its entirety, the following:

         "INITIAL PUBLIC OFFERING" shall mean the first underwritten public
offering of Common Stock of the Company, offered on a firm commitment basis
pursuant to a registration statement filed with the Commission under the
Securities Act on Form S-1 or its then equivalent, in which (i) the aggregate
gross proceeds to the Company equals or exceeds $15,000,000 and (ii) the initial
public offering price per share equals or exceeds $9.95 (subject to appropriate
adjustment for stock splits, stock dividends, combinations and other similar
recapitalization events).

         2. AMENDMENT OF SECTION 2. Effective as of the date first written
above, Section 2.3 of the Investors Rights Agreement is hereby amended by adding
at the end of such section: "and (vii) in an Initial Public Offering."

         3. CONFIRMATION OF TERMS. In all other respects, the terms of the
Investor Rights Agreement are hereby confirmed and ratified.

         4. COUNTERPARTS. This Amendment may be executed in one or more
counterparts, each of which shall be deemed an original and all of which, taken
together, shall constitute one and the same Amendment.

                  [remainder of page intentionally left blank]

<PAGE>

         IN WITNESS WHEREOF, the parties hereto have duly executed this
Amendment as of the date first written above.

                       NEOGENESIS DRUG DISCOVERY, INC.

                       By:  /s/ SATISH JINDAL
                          -------------------------------------------------
                            Satish Jindal, Ph.D.
                            Chief Executive Officer

                       INVESTORS:

                       CADUCEUS PRIVATE INVESTMENTS, LP
                       By OrbiMed Capital, LLC, its General Partner

                       By: /s/ MICHAEL B. SHEFFERY
                          --------------------------------------------------
                       Name:  Michael B. Sheffery
                       Title:

                       ORBIMED ASSOCIATES, LLC
                       By OrbiMed Advisors LLC, its Managing Member

                       By: /s/ MICHAEL B. SHEFFERY
                          --------------------------------------------------
                       Name:  Michael B. Sheffery
                       Title:

                       PW JUNIPER CROSSOVER FUND, L.L.C.
                       By PW Juniper Management, L.L.C., its Investment Advisor

                       By OrbiMed Advisors, Inc., a Member

                       By: /s/ MICHAEL B. SHEFFERY
                          --------------------------------------------------
                       Name:  Michael B. Sheffery
                       Title:

                       FINSBURY WORLDWIDE PHARMACEUTICAL TRUST PLC
                       By OrbiMed Advisors, LLC, its Investment Advisor

                       By: /s/ MICHAEL B. SHEFFERY
                          --------------------------------------------------
                       Name:  Michael B. Sheffery
                       Title:

                       FREYA FANNING & CO.

                       By: /s/ THOMAS B. HALLOWELL
                          --------------------------------------------------
                       Name:  Thomas B. Hallowell
                       Title: General Partner

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