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                                                                     Exhibit 4.4

                            SERIES B PREFERRED STOCK
                               PURCHASE AGREEMENT

                                  BY AND AMONG

                    THE PURCHASERS LISTED ON EXHIBIT A HERETO

                                       AND

                                 CELLOMICS, INC.

                          DATED AS OF FEBRUARY 23, 2000


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                                TABLE OF CONTENTS

















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                                LIST OF EXHIBITS

                                                                       PAGE NO.
                                                                       -------
EXHIBIT A    -    Schedule of Purchasers

EXHIBIT B    -    Amended and Restated Certificate of Incorporation

EXHIBIT C    -    Schedule of Exceptions

EXHIBIT D    -    Form of Proprietary Information Agreement

EXHIBIT E    -    Form of Opinion of Counsel

EXHIBIT F    -    Amended and Restated Shareholders' Agreement

EXHIBIT G    -    Form of Management Rights Letter

EXHIBIT H    -    Form of Key Employee Agreement


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                            SERIES B PREFERRED STOCK
                               PURCHASE AGREEMENT

         THIS SERIES B PREFERRED STOCK PURCHASE AGREEMENT (this "Agreement") is
made and entered into as of the 23rd day of February, 2000, by and among
CELLOMICS, INC. (the "Company"), a Delaware corporation having offices at 635
William Pitt Way, Pittsburgh, Pennsylvania 15238, and EACH OF THE PARTIES LISTED
ON THE SCHEDULE OF PURCHASERS ATTACHED HERETO AS EXHIBIT A (the "Schedule of
Purchasers"). The parties listed on the Schedule of Purchasers are hereinafter
referred to collectively as the "Purchasers".

         WHEREAS, the Company desires to issue and sell, and the Purchasers
desire to purchase, certain securities of the Company;

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants and conditions herein contained, the Company and the Purchasers,
severally and not jointly, hereby agree as follows:

         The Company has, or before the Closing (as defined in Section 2.1
hereof) will have, authorized the issuance and sale of up to Seven Hundred
Thousand (700,000) shares of Series B Preferred Stock, par value $.01 per share
of the Company (the "Series B Preferred"), having the rights, restrictions,
privileges and preferences as set forth in the Amended and Restated Certificate
of Incorporation of the Company (the "Amended and Restated Certificate"), the
form of which is attached to this Agreement as Exhibit B.

         Upon and subject to the terms and conditions of this Agreement and in
reliance upon the representations, warranties and agreements contained herein,
at the Closing the Company will issue and sell to each Purchaser, and each
Purchaser will purchase from the Company at the Closing, that number of shares
of Series B Preferred set forth opposite such Purchaser's name on the Schedule
of Purchasers for the Closing (all such shares being collectively referred to as
the "Shares").

         Certain capitalized terms used in this Agreement shall have the
respective meanings ascribed to them in Section 10 hereof.

         Subject to the terms and provisions of this Agreement, the closing (the
"Closing") of the purchase and sale of Shares hereunder shall be in the amounts
set forth on the Schedule of Purchasers. The Closing shall be by and among the
Company and the Purchasers specified on the Schedule of Purchasers and shall be
held on the date (the "Closing Date") of, and immediately following, (a) the
final execution and delivery of at least one counterpart of this Agreement by
the Company and each of the Purchasers and (b) the satisfaction or waiver of all
conditions to the obligations of the parties to consummate the transactions
contemplated hereby, or such other date as shall have been agreed to by the
Company and the Purchasers.

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         The place of the Closing (including the place of delivery to the
Purchasers by the Company of the certificates evidencing all Shares being
purchased at the Closing and the place of payment to the Company by the
Purchasers of the purchase price therefor) shall be at the offices of Kirkland &
Ellis, 200 East Randolph Drive, Chicago, Illinois 60601, or such other place as
shall have been agreed to by the Company and the Purchasers.

         At the Closing, each Purchaser will pay to the Company by wire transfer
or by conversion of a Bridge Note as set forth on the Schedule of Purchasers,
the amount set forth opposite such Purchaser's name under the column labeled
"Total Investment" on the Schedule of Purchasers; and the Company will deliver
to each Purchaser a certificate or certificates registered in the Purchaser's
name (or in such name or names as otherwise designated by such Purchaser)
representing the number of Shares to be purchased at the Closing as set forth
opposite such Purchaser's name under the column labeled "Series B Preferred
Shares" on the Schedule of Purchasers.

         Except as expressly set forth (with reference to a paragraph in this
Section 3) on the Schedule of Exceptions attached hereto as Exhibit C (the
"Schedule of Exceptions"), the Company hereby represents and warrants to the
Purchasers as follows:

                  (a) The Company is a corporation duly organized, validly
         existing and in good standing under the laws of the State of Delaware
         and is qualified, licensed or domesticated as a foreign corporation in
         each jurisdiction wherein the nature of its activities or properties
         owned or leased by it makes such qualification, licensing or
         domestication necessary. The Schedule of Exceptions sets forth the
         jurisdictions in which the Company is qualified, licensed or
         domesticated as a foreign corporation. The Company has all requisite
         power, governmental licenses, authorization consents and approvals to
         own the properties owned by it and to conduct the business as it is
         being conducted by it and as contemplated by the Company's business
         plan (the "Business Plan"), a true and correct copy of which has been
         given to the Purchasers. The Schedule of Exceptions sets forth all
         jurisdictions in which the Company owns or leases property or engages
         in material activity.

                  (b) Prior to the Closing, the Company shall have properly
         filed and recorded the Amended and Restated Certificate with the
         Secretary of the State of Delaware. The Company is not in material
         breach of any of the provisions of the Amended and Restated Certificate
         or its By-Laws.

         The Company has all requisite corporate power to enter into this
Agreement and each of the Financing Documents and will have on the Closing Date
all requisite corporate power to sell the Shares to be sold on the Closing Date
and to carry out and perform its obligations under the terms of this Agreement
and each of the Financing Documents.

         The Company has no Subsidiaries and, except as set forth in the
Schedule of Exceptions, does not own of record or beneficially any capital stock
or equity interest or investment in any corporation, partnership, association or
business entity.

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         The Schedule of Exceptions contains a true and correct list of all
securities of the Company (including the amounts thereof) outstanding
immediately prior to the Closing, and the holders of any interest in such
securities. Immediately prior to the Closing, the Company's authorized capital
stock will consist of (a) Six Million (6,000,000) shares of Common Stock, par
value $.01 per share of the Company (the "Common Stock"), of which One Million
One Hundred Eighty-Four Thousand Three Hundred Nineteen (1,184,319) shares will
be issued and outstanding, (b) Two Million Twenty-Four Thousand Five Hundred
(2,024,500) shares of Series A Preferred Stock, par value $.01 per share of the
Company (the "Series A Preferred"), of which One Million Nine Hundred Sixty-Six
Thousand Six Hundred Eighteen (1,966,618) shares will be issued and outstanding,
and (c) Seven Hundred Thousand (700,000) shares of Series B Preferred, none of
which will be issued and outstanding. Upon consummation of the Closing, all
issued and outstanding shares of capital stock of the Company will have been
duly authorized and validly issued, will be fully paid and nonassessable, will
be owned of record and beneficially by the shareholders and in the amounts set
forth in the Schedule of Exceptions, and will have been offered, issued, sold
and delivered by the Company in compliance with applicable federal and state
securities laws. Except as set forth in the Schedule of Exceptions, the Amended
and Restated Certificate and the Shareholders' Agreement, there are no
outstanding pre-emptive or other preferential rights, conversion rights or other
rights, options, warrants or agreements granted or issued by or binding upon the
Company for the purchase or acquisition of any shares of its capital stock. No
holder of Common Stock or Series A Preferred has granted (to the best of the
Company's belief) any option or other right to purchase from such shareholder
any interest in any share of Common Stock or Series A Preferred. The Company
holds no shares of its capital stock in its treasury.

         All action on the part of the Company and its directors and
shareholders necessary for the authorization, execution, delivery and
performance by the Company of this Agreement and each of the Financing Documents
and for the consummation of the transactions contemplated herein and therein,
and for the authorization, issuance and delivery of the Shares and the
Conversion Shares has been taken or will be taken prior to the Closing. This
Agreement and each of the Financing Documents is, or upon execution will be, a
valid and binding obligation of the Company, enforceable in accordance with
their respective terms, subject to applicable bankruptcy, insolvency,
reorganization and moratorium laws and other laws of general application
affecting enforcement of creditors' rights generally. The execution and delivery
by the Company of this Agreement and each of the Financing Documents, and
compliance herewith and therewith, and the offer, issuance and sale of the
Shares and the Conversion Shares will not, with or without notice or the passage
of time or both, result in any violation of and will not conflict with, or
result in a breach of any of the terms of, or constitute a default under any
provision of, (i) any state or federal law to which the Company is subject, (ii)
the Amended and Restated Certificate or By-Laws, as amended, or (iii) any
mortgage, indenture, agreement, instrument, judgment, decree, order, rule or
regulation or other restriction to which the Company is a party or by which it
or any of its property is bound, or may be affected, or result in the creation
of any mortgage, pledge, lien, encumbrance or charge upon any of the properties
or assets of the Company pursuant to any such term or give any other person or
entity the right to accelerate the time for performance of any obligation of the
Company, except, with respect to clause (iii) only, for any such violations,
conflicts, breaches, defaults or other occurrences which would not have a
material adverse effect upon the condition, financial or otherwise, or the

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operations of the Company. No shareholder has any pre-emptive rights or rights
of first refusal by reason of or in connection with the issuance of the Shares
or the Conversion Shares. The Shares, when issued in compliance with the
provisions of this Agreement, will be validly issued, fully paid and
nonassessable, and will be free of any liens or encumbrances. The Conversion
Shares have been duly and validly reserved (and are in addition to any other
shares reserved for any other purpose) and are not subject to any pre-emptive
rights or rights of first refusal and, upon issuance, will be validly issued,
fully paid and nonassessable.

         The Schedule of Exceptions sets forth a true and correct list of all
contracts, obligations, commitments, agreements, plans and the like, whether
written or oral, and all administrative, judicial and similar orders to which
the Company is a party or by which it or any of its properties is bound,
including, without limitation, the following:

                  (a) Any employment, bonus or consulting agreement, pension,
         profit sharing, deferred compensation, stock bonus, retirement, stock
         option, stock purchase, phantom stock or similar plan, or agreement
         evidencing rights to purchase securities or phantom stock of the
         Company or any agreement among shareholders of the Company;

                  (b) Any loan or other agreement, note, indenture or instrument
         relating to, or evidencing, indebtedness for borrowed money, or
         mortgaging, pledging or granting or creating a lien or security
         interest or other encumbrance on any property of the Company or any
         agreement or instrument evidencing any guaranty by the Company of
         payment or performance by any other party;

                  (c) Any agreement with any dealer, sales representative,
         broker or other distributor, jobber, advertiser or sales agency;

                  (d) Any agreement with any labor union or collective
         bargaining organization or any other labor agreement;

                  (e) Any contract for the furnishing, purchase or lease of
         machinery, equipment, goods or services (including, without limitation,
         any agreement with processors and subcontractors);

                  (f) Any indenture, agreement or other document (including
         private placement brochures) relating to the future sale or repurchase
         of securities, excluding, however, this Agreement and the Financing
         Documents;

                  (g) Any agreement to register under the Securities Act any of
         the securities of the Company;

                  (h) Any joint venture contract or arrangement or other
         agreement involving a sharing of profits or expenses;

                  (i) Any agreement (other than distributorship agreements or
         similar agreements providing for the distribution of Company's products
         with dealers,

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         distributors and sales representatives of the Company) limiting the
         freedom of the Company to compete in any line of business or in any
         geographic area or with any party; and

                  (j) Any agreement providing for disposition of any line of
         business, assets or securities of the Company, or any agreement with
         respect to the acquisition of any line of business, assets or shares of
         any other business, any agreement of merger or consolidation or letter
         of intent with respect to the foregoing.

         Notwithstanding anything to the contrary herein, the Schedule of
Exceptions may exclude any contract which (i) the Company and/or each Subsidiary
has entered into in the ordinary course of business and (ii) either (1)
obligates the Company and/or each Subsidiary to make payments only, which
payments in the aggregate do not exceed $50,000 or (2) relates only to the
non-disclosure of confidential information. The Company has complied with all
material provisions of each such contract and commitment. No event has occurred
and no condition exists which with notice or the passage of time or both would
constitute a default by the Company or, to the Company's knowledge, by any other
party thereto, under any such contract or commitment. To the Company's
knowledge, no party to such contract or commitment has threatened to terminate
or has any intention of terminating its obligations thereunder.

         Copies of the audited balance sheet of the Company dated December 31,
1997 and copies of the unaudited balance sheets of the Company dated December
31, 1998 and December 31, 1999 (the unaudited balance sheet dated December 31,
1999 being referred to herein as the "Balance Sheet") and the related statements
of operations and accumulated deficit and cash flows for the years then ended
(collectively, the "Financial Statements") attached as annexes to the Schedule
of Exceptions present fairly, in all material respects, the financial position
of the Company as of such dates, have been prepared in accordance with U.S.
generally accepted accounting principles, consistently applied, except for those
changes promulgated and required by accounting authority, and show all material
liabilities, absolute or contingent, of the Company required to be recorded
thereon in accordance with U.S. generally accepted accounting principles as of
the dates thereof.

         The Company does not have, and does not know of, any liabilities (fixed
or contingent, including without limitation any tax liabilities due or to become
due), which, either individually or in the aggregate, are material and not
disclosed on the Balance Sheet.

         Since the date of the Balance Sheet, there has not been:

                  (a) Any change in the condition, assets, liabilities,
         prospects or business of the Company from that shown on the Balance
         Sheet or as described in the Business Plan which, either individually
         or in the aggregate, has been or is reasonably likely to be a material
         adverse change;

                  (b) Any damage to, or destruction or loss of, any of the
         properties or assets of the Company (whether or not covered by
         insurance) materially adversely affecting the business or plans of the
         Company or the Technology;

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                  (c) Any declaration, setting aside or payment or other
         distribution in respect of any of the Company's capital stock, or any
         direct or indirect redemption, purchase or other acquisition of any of
         such stock (or any warrant, option or other right with respect to such
         stock) by the Company or any repayment of Company debt held by any
         Related Party or by an Affiliate;

                  (d) Any labor organizational activity, collective bargaining
         activity, labor dispute or labor trouble;

                  (e) Any event or condition of any character, which, either
         individually or in the aggregate, materially adversely affects the
         business, operations or plans of the Company;

                  (f) Any action taken or entered into by the Company involving
         any transaction other than in the usual and ordinary course of
         business, except this Agreement;

                  (g) Any disclosure to any person of any material trade
         secrets, except for disclosures made to persons subject to valid and
         enforceable confidentiality agreements; or

                  (h) Any disposition of assets, except for sales of inventory
         in the ordinary course of business.

The Company has filed or will file within the time prescribed by law (including
extensions of time approved by any appropriate taxing authority) all tax returns
and reports required to be filed with the United States Internal Revenue Service
and with the Commonwealth of Pennsylvania, and (except to the extent that the
failure to file would not have a material adverse effect on the condition or
operations of the Company) with all other jurisdictions where such filing is
required by law; and the Company has paid, or made adequate provision in the
Balance Sheet for the payment of, all taxes, interest, penalties, assessments or
deficiencies due in connection therewith. The Company has never had any tax
deficiency proposed or assessed against it and the Company has executed no
waiver of any statute of limitations on the assessment or collection of any tax
or governmental charge. None of the Company's federal income tax returns nor any
state income, sales or franchise tax returns has ever been audited by
governmental authorities. No tax audit, action, suit, proceeding, investigation
or claim is now pending nor, to the best of the Company's knowledge, threatened
against the Company, and no issue or question has been raised (and is currently
pending) by any taxing authority in connection with any of the Company's tax
returns or reports.

         The Company has withheld or collected from each payment made to each of
its employees, the amount of all taxes (including, but not limited to, federal
income taxes, Federal Insurance Contribution Act taxes and Federal Unemployment
Tax Act taxes) required to be withheld or collected therefrom, and has paid the
same to the proper tax receiving officers or authorized depositories.

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         Except as set forth in the Schedule of Exceptions, there is no loan,
lease or other continuing transaction between the Company, any Related Party
and/or any Affiliate.

         There is neither pending nor, to the Company's knowledge and belief,
threatened any action, suit, proceeding or claim, whether or not purportedly on
behalf of the Company, to which the Company or any employee of the Company, in
such capacity, is or may be named as a party or to which the Company's property
is or may be subject. To the best of the Company's knowledge and belief, there
is no basis for any such action, suit, proceeding or claim, in which an
unfavorable outcome, ruling or finding in any such matter or for all such
matters, taken as a whole, might have a material adverse effect on the
condition, financial or otherwise, operations or prospects of the Company or on
the Technology. The Company has no knowledge of any unasserted claim, the
assertion of which is likely and which, if asserted, will seek damages, an
injunction or other legal, equitable, monetary or nonmonetary relief which if
granted would have a material adverse effect on the condition, financial or
otherwise, operations or prospects of the Company.

         Except as set forth in the Schedule of Exceptions, no consent, approval
or authorization of, or designation, declaration or filing with, any
governmental authority on the part of the Company, including qualification under
applicable state securities laws of the offer and sale of the Shares and of the
issuance of the Conversion Shares is required in connection with the valid
execution and delivery of this Agreement, the offer, sale or issuance of the
Shares, the conversion of the Shares into Common Stock or the issuance of the
Conversion Shares, or the consummation of any other transaction contemplated on
the Closing Date by this Agreement or any of the Financing Documents, except the
filing of the Amended and Restated Certificate with the Secretary of the State
of Delaware, which filing has been made and is effective as of the date hereof.
Any such consent, approval, authorization, declaration or filing set forth in
the Schedule of Exceptions has been obtained or made and is effective as of the
Closing Date.

         The Company has good and marketable title to all its properties and
assets, free from all mortgages, pledges, liens, security interests, conditional
sale agreements, encumbrances or charges.

         Set forth on the Schedule of Exceptions is a correct and complete list
of all leases (including, with respect to each lease, the material provisions of
such lease, including the term, the amount of rent called for and a description
of the leased property) under which the Company is a lessee, other than personal
property requiring rental payments of less than $25,000 per year. The Company
enjoys peaceful and undisturbed possession under all such leases, all of such
leases are valid and subsisting and none of them is in default in any respect,
and no event has occurred and no condition exists which with notice or the
passage of time or both would constitute such a default.

                  (a) All (i) franchises, permits, licenses and other similar
         authority, (ii) patents, patent applications, patent rights, service
         marks, trademarks, trademark applications, trademark rights, trade
         names, trade name rights and copyrights (whether registered or not),
         and (iii) know-how, technology and trade secrets, which are or may be
         usable now

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         or in the future for the conduct of the Company's business as now
         conducted or as planned to be conducted are owned by the Company or the
         Company has all rights to use such technology set forth in (i), (ii) or
         (iii) above. The documents and instruments evidencing such ownership
         and rights are listed in the Schedule of Exceptions.

                  (b) The Company has all franchises, permits, licenses and
         other similar authority, necessary for the conduct of its business as
         now being conducted by it and believes it can obtain any similar
         authority necessary for the conduct of its business as planned to be
         conducted, and it is not in violation, nor will the transactions
         contemplated by this Agreement cause a violation of the terms or
         provisions of any such franchise, permit, license or other similar
         authority.

                  (c) Section 3.16(c) of the Schedule of Exceptions lists all
         patents, patent applications, patent rights, trademarks, trademark
         applications, trademark rights, trade names, trade name rights, service
         marks and copyrights (whether registered or not) owned or possessed by
         the Company (collectively, the "Listed Rights"). The Listed Rights
         comprise all the patents, patent applications, patent rights,
         trademarks, trademark applications, trademark rights, trade names,
         trade name rights, service marks and copyrights (whether registered or
         not) necessary to the conduct of the Company's business as now being
         conducted, and the Company believes that the Company can obtain any
         such rights necessary for the conduct of its business as planned to be
         conducted. The Company has and possesses the know-how, technology and
         trade secrets not included in the Listed Rights (such know-how,
         technology and trade secrets being collectively called the
         "Intellectual Property") which they believe to be necessary (i) to
         conduct the Company's business as now being conducted and (ii) with
         additional know-how, technology and trade secrets which the Company
         plans to develop, for the conduct of its business as planned to be
         conducted. (The Listed Rights and the Intellectual Property
         collectively constitute the "Technology".) There is neither pending,
         nor, to the best of the Company's knowledge and belief, threatened, any
         claim or litigation against the Company contesting the validity or
         right to use any of the Listed Rights or any of the Intellectual
         Property, nor is the Company aware of any basis therefor, and the
         Company has not received any notice of infringement upon or conflict
         with any asserted right of others. To the best of the Company's
         knowledge and belief, no person, corporation or other entity is
         infringing or violating the Listed Rights or any of the Intellectual
         Property. Except as described in the Schedule of Exceptions, the
         Company does not have any obligation to compensate others for the use
         of any Listed Right or any Intellectual Property, nor has the Company
         granted any license or other right to use, in any manner, any of the
         Listed Rights or Intellectual Property, whether or not requiring the
         payment of royalties.

         All taxes imposed by any state in connection with the issuance, sale
and delivery of the Shares shall have been fully paid, and all laws imposing
such taxes shall have been fully complied with, prior to the Closing Date.

         Within the past six (6) months, the Company has not, either directly or
through any agent, offered any of the Shares or any security or securities
similar to the Shares for sale to, or

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solicited any offers to buy the Shares or any part thereof or any such similar
security or securities from, or otherwise approached or negotiated in respect
thereof with, any party or parties other than the Purchasers or institutional or
other sophisticated investors, each of which was offered all or a portion of the
Shares at a private sale for investment. Each offer described on the Schedule of
Exceptions with respect to this Section 3.18 was an offer to an institutional or
sophisticated investor relating to a private sale for investment, and such
offers do not, individually or collectively, affect the exemption of the offer,
sale and issuance of the Shares and the Conversion Shares from the registration
requirements of the Securities Act and all state securities laws.

         Subject in part to the truth and accuracy of the Purchasers'
representations set forth in this Agreement, the offer, sale and issuance of the
Shares and the Conversion Shares as contemplated by this Agreement are exempt
from the registration requirements of the Securities Act, and all applicable
state securities laws, and neither the Company nor anyone acting on its behalf
will take any action hereafter that would cause the loss of such exemption.

         The Company is not in violation of any term of the Amended and Restated
Certificate or By-Laws. Neither the Company nor any of its property is in
violation of any term of any mortgage, indenture, contract, agreement,
instrument, judgment, decree, order, statute, rule or regulation to which the
Company or any of such property is subject, a violation of which would
materially adversely affect the Company's condition, financial or otherwise, or
operations or the Technology.

                  (a) No employee of the Company and no Related Party is, or is
         now expected to be, in violation of any term of any employment
         contract, patent disclosure agreement, non-competition agreement, or
         any other contract or agreement with any prior employer or any other
         person, corporation, or other entity or any restrictive covenant in
         such an agreement, or any obligation imposed by common law or
         otherwise, relating to the right of any such employee or Related Party
         to be employed by the Company because of the nature of the business
         conducted or to be conducted by the Company or relating to the use of
         trade secrets or proprietary information of others because of the
         nature of the business conducted or to be conducted by the Company, and
         the continued employment of the Company's employees and/or Related
         Parties does not subject the Company or the Purchasers to any liability
         for any such violation.

                  (b) Each of the Company's present or former employees who has
         had access to proprietary information of the Company has executed a
         Proprietary Information and Property Agreement substantially in the
         form attached as Exhibit D hereto (each a "Proprietary Information
         Agreement"). To the best of the Company's knowledge and belief, no
         employee or former employee of the Company is, or to the best of the
         Company's knowledge and belief now is expected to be, in violation of
         the terms of the Proprietary Information Agreement entered into by such
         employee or former employee, or of any other obligation relating to the
         use of confidential or proprietary information of the Company. Each of
         such Proprietary Information Agreements remains in full force and
         effect.

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                  (c) Section 3.20(c) of the Schedule of Exceptions describes
         all employment agreements to which the Company is a party. Each of such
         employment agreements remains in full force and effect.

                  (d) To the best knowledge of the Company, no officer or key
         employee of the Company has any present intent of terminating such
         officer's or key employee's employment with the Company.

                  (e) The Company is in material compliance with all laws
         regarding employment, wages, hours, equal opportunity, collective
         bargaining and payment of Social Security and other taxes. The Company
         is in material compliance with all applicable foreign, federal, state
         and local laws and regulations regarding occupational safety and health
         standards and has received no complaints from any foreign, federal,
         state or local agency or regulatory body alleging violations of any
         such laws and regulations.

                  (f) Except as set forth on the Schedule of Exceptions hereto,
         the employment of all persons and officers employed by the Company is
         terminable at will without any penalty or severance obligation of any
         kind on the part of the employer. All sums due for employee
         compensation and benefits and all vacation time owing to any employees
         of the Company have been duly and adequately accrued on the accounting
         records of the Company. All employees of the Company are either United
         States citizens or resident aliens specifically authorized to engage in
         employment in the United States in accordance with all applicable laws.

                  (g) The Company has not experienced, nor does it know of any
         basis for, any strike, labor troubles or strife, work stoppages or slow
         downs. The Company has not experienced, nor does it know or have
         reasonable grounds to know of, any union or collective bargaining
         organization efforts or negotiations, or requests for negotiations, for
         any representation or any labor contract relating to any employees of
         the Company.

         The Company has no knowledge and does not believe that (i) there is
pending or threatened any claim or litigation against or affecting the Company
contesting its right to manufacture, sell or use any product or service
presently manufactured, sold or used or planned to be manufactured, sold or used
by the Company, (ii) there exists, or there is pending or planned, any statute,
rule, law, regulation, standard or code which would materially adversely affect
the condition, financial or otherwise, or the operations of the Company, or
(iii) there is any other existing fact which in the future could reasonably be
expected to materially adversely affect the Company's condition, financial or
otherwise, or operations. The Company currently intends to engage in the
business of the general type described in the Business Plan (the "Business").

         The Company will use the proceeds of the offering (a) as set forth in
the Statement of Sources and Uses contained in the Schedule of Exceptions and
(b) for expenses incurred in connection with the transactions contemplated
hereby. The Company will not use the proceeds of the offering for any other
purpose. None of the transactions contemplated in this Agreement

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(including, without limitation, the use of the proceeds from the sale of the
Shares or the Conversion Shares) will violate or result in a violation of
Section 7 of the Exchange Act, including, without limitation, Regulations G, T
and X of the Board of Governors of the Federal Reserve System, 12 C.F.R.,
Chapter 11. The Company does not own or intend to carry or purchase any "margin
security" within the meaning of said Regulation G, including margin securities
originally issued by it. None of the proceeds from the sale of the Shares or the
Conversion Shares will be used to purchase or carry (or refinance any borrowing
the proceeds of which were used to purchase or carry) any "security" within the
meaning of the Securities Act.

                  (a) The Company does not have or make contributions to any
         pension plans, defined benefit plans or defined contribution plans for
         its employees which are subject to the Employee Retirement Income
         Security Act of 1974, as amended ("ERISA"). With respect to such plans,
         if any, listed on the Schedule of Exceptions, the Company is in
         compliance with the applicable provisions of ERISA. The Company has not
         incurred any unremedied accumulated funding deficiency within the
         meaning of ERISA or any unsatisfied liability to the Pension Benefit
         Guaranty Corporation established under ERISA in connection with any
         employee pension plan established or maintained by the Company under
         the jurisdiction of ERISA. No Reportable Event or Prohibited
         Transaction (as defined in Section 4043 of ERISA) has occurred with
         respect to any plan administered by the Company.

                  (b) The Company's employment practices and policies are in
         full compliance with (i) all applicable laws of the United States and
         each applicable jurisdiction relating to equal employment opportunity,
         and any rules, regulations, administrative orders and Executive Orders
         relating thereto; and (ii) the applicable terms, relating to equal
         opportunity, of any contract, agreement or grant the Company has with,
         from or relating (by way of subcontract or otherwise) to any other
         contract, agreement or grant of, any federal or state governmental
         unit, except, with respect to each of clause (i) and (ii), for any
         failures to be in compliance which would not have a material adverse
         effect on the condition, financial or otherwise, or the operations of
         the Company. The Company has not been the subject of any charge of
         unfair labor practices, employment discrimination made against it by
         the National Labor Relations Board, the United States Equal Employment
         Opportunity Commission or any other governmental unit, nor is it
         presently subject to any formal or informal proceedings before, or
         investigations by, such Commission or governmental unit. To the
         Company's knowledge, neither the Company, nor any employees of the
         Company, nor any Related Parties are presently under investigation by
         any commission or governmental agency for purposes of security
         clearance or otherwise.

                  (c) Neither the Company nor any property owned or occupied by
         the Company is in violation of any Federal or State Environmental Law
         of any sort or in violation of any Federal or State "OSHA" law, except
         for such violations which, either individually or in the aggregate,
         would not have a material adverse effect on the condition, financial or
         otherwise, or the operations of the Company. The Schedule of Exceptions
         contains a list of all environmental permits held by the Company.
         Without limiting the generality of the foregoing:

                                       14
<PAGE>   15

                           (i) ENVIRONMENTAL PERMITS. The Company has obtained
                  all environmental, health and safety permits and governmental
                  authorizations (collectively, the "Environmental Permits")
                  necessary for the construction of their facilities or the
                  conduct of their operations, and all such Environmental
                  Permits are in good standing and the Company is in compliance
                  with all terms and conditions of the Environmental Permits,
                  except for such failures to be in compliance which, either
                  individually or in the aggregate, would not have a material
                  adverse effect on the condition, financial or otherwise, or
                  the operations of the Company. No notice to, approval of or
                  authorization or consent from any governmental or regulatory
                  authority is necessary for the transfer of or modification to
                  any Environmental Permit and the consummation of the
                  transactions contemplated by this Agreement will not violate,
                  alter, impair or invalidate, in any respect, any Environmental
                  Permit.

                           (ii) ENVIRONMENTAL CLAIMS. There is no Environmental
                  Claim pending, threatened or, to the best of the Company's
                  knowledge, likely to be threatened (i) against the Company,
                  (ii) against any person or entity whose liability for any
                  Environmental Claim the Company has or may have retained or
                  assumed either contractually or by operation of law, or (iii)
                  against any real or personal property or operations which are
                  now or have been previously owned, leased, operated or
                  managed, in whole or in part, by the Company.

                           (iii) RELEASES. There have been no Releases of any
                  Hazardous Materials that would be likely to form the basis of
                  any Environmental Claim against the Company or against any
                  person or entity whose liability for any Environmental Claim
                  the Company has or may have retained or assumed either
                  contractually or by operation of law.

                           (iv) ENVIRONMENTAL ASSESSMENTS. There are no
                  environmental reports, audits, investigations or assessments
                  of the Company, or any real or personal property or operations
                  which are now or have been previously owned, leased, operated
                  or managed, in whole or in part, by the Company.

                           (v) ENVIRONMENTAL DISCLOSURE. To the best knowledge
                  of the Company upon diligent review, the Company has disclosed
                  to the Purchasers all relevant facts with respect to potential
                  or actual environmental liabilities of the Company.

                  (d) The Company has not violated any law or any governmental
         law, rule, order or regulation or requirement which violation through
         the date hereof has had or would reasonably be expected to have a
         material adverse effect upon the financial condition, operating
         results, assets, operations or business prospects of the Company or the
         Technology and the Company has not received notice of any such
         violation.

                                       15
<PAGE>   16

         The Schedule of Exceptions contains a true and complete list, including
the names of the parties thereto and summary description of the terms thereof,
of all debt instruments, loan agreements, indentures or guaranties, whether
written or oral, other than obligations which may be terminated without payment
or penalty by the Company upon not more than thirty (30) days' notice and
obligations which are otherwise disclosed in this Agreement. All of the
aforesaid items were entered into in the ordinary course of business, are valid
and binding, in full force and effect and are enforceable in accordance with
their respective terms and there exists no breach or default, or any event which
with notice or lapse of time or both, would constitute a breach or default by
any party thereto, except for such breaches or defaults which, either
individually or in the aggregate, would not have a material adverse effect on
the condition, financial or otherwise, or the operations of the Company. All of
the Company's Indebtedness is disclosed on the Balance Sheet.

         All facilities, machinery, equipment, fixtures, vehicles and other
properties owned, leased or used by the Company are in good operating condition
and repair, are reasonably fit and usable for the purposes for which they are
being used, are adequate and sufficient for the Company's business and conform
in all material respects with all applicable ordinances, regulations and laws.

         The Company has not been refused any insurance coverage sought or
applied for, and the Company has no reason to believe that it will be unable to
obtain one or more policies of insurance issued by insurers of recognized
responsibility, insuring the Company and its properties and business against
such losses and risks, and in such amounts, as are customary in the case of
corporations of established reputation engaged in the same or similar business
and similarly situated. The Schedule of Exceptions sets forth each insurance
policy (specifying the insurer, the amount of coverage, the type of insurance,
the policy number, the expiration date, the annual premium, loss payees and any
pending claims thereunder) maintained by the Company relating to its respective
properties, assets, business or personnel (which policies include directors' and
officers' liability insurance in the amount of at least $1,000,000), and each
inspection report or recommendation, if any, during the last three years as to
the conditions of the properties and assets owned, leased, occupied or operated
by it or the conduct of its business. The Company is not in default with respect
to any provision contained in any insurance policy, and the Company has not
failed to give any notice or present any presently existing claims under any
insurance policy in due and timely fashion, except for such defaults or failures
to give notice as would not result in termination or denial of coverage under
such policy.

         Other than under this Agreement or as listed in the Schedule of
Exceptions, the Company has not agreed to register under the Securities Act any
of its authorized or outstanding securities.

         The Company has never filed, has never been required to file and is not
currently required to file any reports, statements, forms or documents with the
Commission.

         Neither the Company, nor, to the best knowledge and belief of the
Company, any of its respective officers, directors, employees, agents or other
representatives of the Company or any other business entity or enterprise with
which the Company is or has been affiliated or associated, has, directly or
indirectly, made or authorized any payment, contribution or gift of

                                       16
<PAGE>   17

money, property, or services, whether or not in contravention of applicable law,
(a) as a kickback or bribe to any person or (b) to any political organization,
or the holder of or any aspirant to any elective or appointive public office
except for personal political contributions not involving the direct or indirect
use of funds of the Company.

         The Company qualifies as a "Qualified Small Business" within the
meaning of Section 1202(d) of Internal Revenue Code of 1986, as amended (the
"Code"). Upon issuance, the Shares will qualify as "qualified small business
stock" within the meaning of Section 1202 of the Code. Without limiting the
generality of the foregoing: (i) the Company is a domestic C corporation, (ii)
the Company has not made any purchases of its own stock described in Code
Section 1202(c)(3)(B), and (iii) the Company's (or any predecessor's) aggregate
gross assets, as defined by Code Section 1202(d)(2), at no time between August
10, 1993 and through the Closing have exceeded or will exceed $50,000,000,
taking into account the assets of any corporation required to be aggregated with
the Company in accordance with Code Section 1202(d)(3).

         The merger of BioDx, Inc., a Pennsylvania corporation and the
predecessor-in-interest to the Company ("BioDx"), with and into the Company (the
"Reincorporation Merger") was duly and validly authorized by all requisite
corporate action and has been validly effected in accordance with applicable
law. The Company has succeeded to all of BioDx's rights and obligations pursuant
to the provisions of applicable law as a result of the Reincorporation Merger.
Without limiting the generality of the foregoing, the Company has succeeded to
all of BioDx's rights as against third parties under the contracts to which
BioDx was a party at the time of the Reincorporation Merger, and the
Reincorporation Merger has not, and will not, with or without notice or the
passage of time or both, result in any violation of, conflict with, breach any
terms of, constitute a default under, or give any third party any right to
terminate or modify, any such contract.

         This Agreement, the Schedule of Exceptions, the Balance Sheet, the
Financial Statements, the factual statements contained in the Business Plan, and
any other written statement furnished to the Purchasers or their counsel in
connection with the offer and sale of the Shares (other than the Company's
offering memorandum, as to which the Company makes no representations and
warranties and as to which the Company undertakes no obligation to update or
otherwise revise the information contained therein), taken as a whole, do not
contain any untrue statement of a material fact or omit to state a material fact
necessary in order to make the statements contained therein or herein not
misleading in the light of the circumstances under which they were made. There
is no fact which the Company has not disclosed to the Purchasers in writing that
materially adversely affects or, so far as the Company can now reasonably
foresee, will materially adversely affect the properties, business, prospects,
profits or condition (financial or otherwise) of the Company or the ability of
the Company to perform this Agreement and the Financing Documents or the other
actions contemplated hereby. The forecasts, projections, estimates and other
forward-looking matters furnished to the Purchasers (including those set forth
in the Business Plan) were prepared on the basis of the Company's best
estimates, which include certain assumptions. The Company does not have any
reason to believe that any assumptions or statements of opinion contained in
such forecasts, projections, estimates or other forward-looking matters are
unreasonable or false.

                                       17
<PAGE>   18

         Each of the Purchasers represents and warrants to the Company, as to
itself only, as follows:

                  (a) AUTHORIZATION. It has full power and authority to enter
         into this Agreement, the Financing Documents and all other documents
         and instruments executed by it in connection with the transactions
         contemplated hereby and thereby, and each such agreement, document or
         instrument constitutes its valid and legally binding obligation,
         enforceable against it in accordance with its terms, subject to
         applicable bankruptcy, insolvency, reorganization and moratorium laws
         and other laws of general application affecting enforcement of
         creditors' rights generally.

                  (b) ACCREDITED INVESTOR. It is an "accredited investor" within
         the meaning of Commission Rule 501 of Regulation D, as presently in
         effect.

                  (c) EXPERIENCE. It is experienced in evaluating and investing
         in companies such as the Company.

                  (d) INVESTMENT. It is acquiring the Shares for investment for
         its own account and not with the view to, or for resale in connection
         with, any distribution thereof. It understands that the Shares and the
         Conversion Shares have not been registered under the Securities Act by
         reason of an exemption from the registration provisions of the
         Securities Act which depends upon, among other things, the bona fide
         nature of its investment intent as expressed herein.

                  (e) RULE 144. It understands that the Shares it is purchasing
         are characterized as "restricted securities" under the federal
         securities laws inasmuch as they are being acquired from the Company in
         a transaction not involving a public offering and that under such laws
         and applicable regulations such securities may be resold without
         registration under the Securities Act only in certain limited
         circumstances. It acknowledges that the Shares and the Conversion
         Shares must be held indefinitely unless they are subsequently
         registered under the Securities Act or an exemption from such
         registration is available. It has been advised or is aware of the
         provisions of Rule 144 promulgated under the Securities Act, which
         permits limited resale of shares purchased in a private placement
         subject to the satisfaction of certain conditions (which conditions
         cannot presently be satisfied).

                  (f) ACCESS TO DATA. It has had an opportunity to discuss the
         Company's business, management and financial affairs with the Company's
         management, and it has been furnished with copies of documents which it
         has requested.

                  (g) NO RELIANCE ON CERTAIN TYPES OF ADVICE. It is not relying
         on the Company for advice with respect to tax considerations, the
         suitability of his, her or its investment in the Company or legal or
         economic considerations.

                                       18
<PAGE>   19

                  (h) MARKETABILITY. It understands that the Company is closely
         held and that there is no public market for resale of the Shares. It
         understands that it is possible that a market for the Shares will not
         ever develop. As a consequence, it understands that it may not be able
         to liquidate its investment in the Shares, even in the event of an
         emergency. It also understands that, for the foregoing reasons, the
         Shares may not be readily accepted as collateral for a loan.

                  (i) ADDRESSES. The address set forth in Exhibit A attached
         hereto is the Purchaser's true and correct residence and/or principal
         place of business as of the date hereof.

         By their execution of this Agreement, the Bridge Investors acknowledge
and confirm that at and upon the Closing, the principal of and interest accrued
on the Bridge Notes through the Closing Date will convert into Shares and the
Bridge Warrants will be issued. In addition, the Bridge Investors agree that
effective upon such conversion of the Bridge Notes into Shares and such issuance
of the Bridge Warrants (a) the Bridge Loan Subscription Agreements shall
terminate and be of no further force and effect, (b) the Bridge Notes shall be
deemed canceled and shall be of no further force and effect, and (c) neither the
Bridge Investors nor the Company shall have any further rights, obligations or
liabilities under the Bridge Loan Subscription Agreements or the Bridge Notes.
The Bridge Investors hereby waive any rights to receive notice of, and any
rights of first refusal, pre-emptive rights and other similar rights that they
may have under the Bridge Notes or the Bridge Loan Subscription Agreements with
respect to, the issuance of the Shares to the Purchasers pursuant to this
Agreement. The Company acknowledges and agrees to the provisions of this Section
4.2.

         The obligation of the Purchasers to purchase the Shares to be purchased
by them at the Closing is subject to the fulfillment to their satisfaction on or
prior to the Closing Date of each of the following conditions:

         The representations and warranties made by the Company in Section 3
hereof shall be true and correct in all respects when made, and shall be true
and correct in all respects on the Closing Date and with respect thereto, after
giving effect to the sale and issuance of the Shares at the Closing.

         All covenants, agreements and conditions contained in this Agreement
(including those in Section 2.1) to be performed or complied with by the Company
on or prior to the Closing Date shall have been so performed or complied with in
all material respects.

         The Company shall have executed and delivered to the Purchasers a
certificate of the President of the Company, dated the Closing Date, certifying
to the fulfillment of the conditions specified in Sections 5.1 and 5.2 of this
Agreement and such other matters as the Purchasers may reasonably request.

         The Purchasers shall have received an opinion of counsel from Sweeney
Metz Fox McGrann & Schermer, L.L.C., counsel to the Company, addressed to them,
dated the Closing Date, to the effect and in substantially the form set forth in
Exhibit E.

                                       19
<PAGE>   20

         The Company shall have delivered to the Purchasers a certificate of
recent date from the Secretary of State of the State of Delaware with respect to
the Company's due incorporation, good standing, legal corporate existence, due
authorization to conduct business and the payment of all franchise taxes, and,
certificates from the Secretary of State in each jurisdiction in which the
Company is required to be qualified to do business with respect to the Company's
good standing and due authorization to conduct business therein and payment of
all qualification fees.

         At the time of the Closing, the purchase of the Shares to be purchased
by the Purchasers hereunder shall be legally permitted by all laws and
regulations to which it and the Company are subject.

         All authorizations, approvals, or permits of any governmental authority
or regulatory body that are required in connection with the lawful issuance and
sale of the Shares pursuant to this Agreement, the conversion of the Shares into
Common Stock and the issuance of such Common Stock upon such conversion shall
have been duly obtained and shall be effective on and as of the Closing Date,
including, if necessary, permits from applicable state securities authorities,
qualifying the offer and sale of the Shares and the Conversion Shares.

         The Amended and Restated Certificate shall have been filed with the
Secretary of the State of Delaware, duly amending the Certificate of
Incorporation of the Company.

         All corporate and other proceedings in connection with the transactions
contemplated hereby and all documents and instruments incident to such
transactions shall be reasonably satisfactory in substance and form to the
Purchasers and special counsel for the Purchasers.

         The By-Laws of the Company shall provide that (a) a majority of the
Directors constituting the Board shall constitute a quorum for the transaction
of any business at a meeting of the Board, and (b) the Board of Directors shall
meet at least four (4) times per year.

         The Company, the Purchasers, the holders of the Company's shares of
Common Stock (the "Common Shareholders"), the holders of the Company's shares of
Series A Preferred (the "Series A Preferred Shareholders"), and the other
parties named therein shall have executed and delivered an Amended and Restated
Shareholders' Agreement (as further amended from time to time, the
"Shareholders' Agreement") to the effect and in substantially the form set forth
in Exhibit F hereto.

         The Company shall have executed and delivered to each Purchaser who
requests the same a Management Rights Letter (collectively, the "Management
Rights Letters") to the effect and in substantially the form set forth in
Exhibit G hereto.

         Alan Mendelson, Dr. Arnold Oronsky, Dr. Lansing Taylor, John Boles and
James Sharp shall have been elected to the Board of Directors, and the Company
shall have agreed and obligated itself, either in the Amended and Restated
Certificate or in the Company's Bylaws, to indemnify its officers and directors
to the fullest extent permitted by Delaware law.

                                       20
<PAGE>   21

         The Bridge Notes shall have been surrendered to the Company for
conversion into Shares at the Closing, as further described in Section 4.2.

         The Bridge Warrants shall have been issued at the Closing, as further
described in Section 4.2.

         The Company shall have delivered to the Purchaser certified copies of
the resolutions of the Common Shareholders and Series A Preferred Shareholders
and the Company's Board of Directors approving the transactions contemplated by
this Agreement.

         Each Purchaser shall be satisfied in its sole discretion with the
results of its legal, accounting, business, environmental and other due
diligence review of the Business.

         The Company's obligation to sell the Shares to be purchased at the
Closing is subject to the fulfillment to its satisfaction on or prior to the
Closing Date of each of the following conditions:

         The representations made by the Purchasers pursuant to Section 4.1
hereof shall be true and correct when made and shall be true and correct on the
Closing Date.

         All covenants, agreements and conditions contained in this Agreement to
be performed or complied with by each and every Purchaser on or prior to the
Closing Date shall have been so performed or complied with in all material
respects.

         At the time of the Closing, the conditions set forth in Sections 5.6
and 5.7 shall have occurred and the purchase of the Shares to be purchased by
the Purchasers hereunder shall be legally permitted by all laws and regulations
to which the Purchasers and the Company are subject.

         The Amended and Restated Certificate shall have been accepted for
filing by the Secretary of State of the State of Delaware.

         The Company, the Purchasers, the Common Shareholders, the Series A
Preferred Shareholders and the other parties named therein shall have executed
and delivered the Shareholders' Agreement.

         The Company hereby covenants and agrees, so long as any Shares or any
Conversion Shares remain outstanding, or as otherwise provided in this Article
7:

         The Company will furnish the following reports to the Purchasers:

                  (a) As soon as practicable after the end of each fiscal year
         of the Company, and in any event within ninety (90) days thereafter, a
         consolidated (and consolidating) balance sheet of the Company and its
         Subsidiaries, if any, as at the end of such fiscal year, and
         consolidated (and consolidating) statements of operations, accumulated
         earnings and cash flows of the Company and its Subsidiaries, if any,
         for such year,

                                       21
<PAGE>   22

         prepared in accordance with generally accepted accounting principles
         consistently applied and setting forth in each case in comparative form
         the figures for the previous fiscal year, all in reasonable detail
         audited (without scope limitations imposed by the Company) and
         certified by independent public accountants of recognized national
         standing selected by the Company and satisfactory to the Purchasers.

                  (b) As soon as practicable after the end of the first, second
         and third quarterly accounting periods in each fiscal year of the
         Company, and in any event within forty-five (45) days thereafter, a
         consolidated (and consolidating) balance sheet of the Company and its
         Subsidiaries, if any, as of the end of each such quarterly period, and
         consolidated (and consolidating) statements of operations, accumulated
         earnings and cash flows of the Company and its Subsidiaries, if any,
         for such period and for the current fiscal year to date, prepared in
         accordance with generally accepted accounting principles consistently
         applied and setting forth in comparative form the figures for the
         corresponding periods of the previous fiscal year, subject to changes
         resulting from year-end audit adjustments, and setting forth any events
         which could reasonably be expected to have an adverse effect upon the
         Company's or any Subsidiary's finances or the results of its
         operations, all in reasonable detail and certified by the principal
         financial or accounting officer of the Company.

                  (c) From the date the Company becomes subject to the reporting
         requirements of the Exchange Act, and in lieu of the financial
         information and certificate required pursuant to Sections 7.1(a), (b),
         (d) and (e), respectively, but within the time periods required for the
         furnishing thereof, copies of its reports filed on Form 10-K, Form
         10-Q, Form 8-K or any successor form or forms.

                  (d) Subject to Section 7.1(c), each set of financial
         statements delivered to the Purchasers pursuant to this Section 7.1
         will be accompanied by a certificate of the Chief Financial Officer of
         the Company setting forth:

                           (i) Covenant Compliance - any information required in
                  order to establish whether the Company and its Subsidiaries
                  were in compliance with the requirements of this Section 7
                  during the period covered by the income statement then being
                  furnished; and

                           (ii) Event of Default - that the signers have
                  reviewed the relevant terms of this Agreement and have made,
                  or caused to be made, under their supervision, a review of the
                  transactions and conditions of the Company and its
                  Subsidiaries, if any, from the beginning of the accounting
                  period covered by the income statements being delivered
                  therewith to the date of the certificate and that such review
                  has not disclosed the existence during such period of any
                  condition or event which constitutes a breach or default under
                  this Agreement, the Amended and Restated Certificate or any of
                  the Financing Documents or, if any such condition or event
                  existed or exists, specifying the nature and period of
                  existence thereof and what action the Company has taken or
                  proposes to take with respect thereto.

                                       22
<PAGE>   23

                  (e) Subject to Section 7.1(c), as soon as available (but in
         any event sixty (60) days or more before the commencement of each
         fiscal year) the Company's budget and its operating plan for such
         fiscal year (the "Annual Plan") as approved by the Board indicating,
         among other things, quarterly income statements, balance sheets and
         cash flow statements for the next fiscal year, plans for incurring
         indebtedness and projections regarding other sources of funds; any
         material changes in such financial plan shall be submitted as promptly
         as practicable after such changes have been approved by the Board.

         The Company will, for any Purchaser who (together with members of such
Purchaser's Group) agrees pursuant to this Agreement to purchase in the
aggregate, at the Closing, 200,000 or more Shares (such amount to be adjusted
for stock splits, combinations and other similar events affecting the Series B
Preferred):

                  (a) Permit such Purchaser (or its designated representative),
         at its own expense, to visit and inspect any of the properties of the
         Company, including its books of account, and to discuss its affairs,
         finances and accounts with the Company's officers and its independent
         public accountants, all at such reasonable times and as often as any
         such party may reasonably request. Any such Purchaser shall give not
         less than two (2) business days' notice of any such visitation or
         inspection and such visitation or inspection shall be performed in a
         reasonable manner and with due regard to the proprietary and
         confidential nature of any information received by it.

                  (b) Deliver the reports and data described below to such
         Purchaser:

                           (i) As soon as practicable after the end of each
                  fiscal month and in any event within thirty (30) days
                  thereafter, a consolidated balance sheet of the Company and
                  its Subsidiaries, if any, as at the end of such month, and
                  consolidated statements of operations, accumulated earnings
                  and cash flows of the Company and its Subsidiaries, if any,
                  for each month, prepared in accordance with generally accepted
                  accounting principles consistently applied, together with
                  comparison of such statements to the Annual Plan then in
                  effect and to the financial statements for the comparable
                  period in the prior fiscal year, and certified, subject to
                  changes resulting from year-end audit adjustments, by the
                  principal financial or accounting officer of the Company;

                           (ii) As soon as available, information and data on
                  any material adverse changes in or any event or condition
                  which materially adversely affects or could materially
                  adversely affect the business, operations, properties or plans
                  of the Company;

                           (iii) Immediately upon becoming aware of any
                  condition or event which constitutes a breach or violation of
                  this Agreement, the Amended and Restated Certificate, the
                  Financing Documents or any agreement contemplated hereby or
                  thereby, written notice specifying the nature and period of
                  existence

                                       23
<PAGE>   24

                  thereof and what action the Company is taking or proposes to
                  take with respect thereto; and

                           (iv) With reasonable promptness, such other
                  information and data with respect to the Company as any such
                  party may from time to time reasonably request.

                  (c) Hold meetings of its Directors at least quarterly and, if
         such Purchaser does not have a representative affiliated with such
         Purchaser on the Board of Directors, permit such Purchaser to send a
         representative (without voting rights) to each meeting of the Board of
         Directors of the Company and all committees of such Board; provided,
         however, that the Purchasers shall receive notice no less favorable
         than notice given to outside directors and the presence of any of the
         Purchasers' representatives shall not be necessary to conduct any
         meeting of the Board. The Company shall give such Purchaser notice of
         each such meeting in the form and manner such notice is given to the
         Company's directors.

                  (d) The Company's obligations under this Section 7.2 shall
         terminate at such time as a Qualified Public Offering has closed and
         any agreement of the type described in Section 9.15 hereof is no longer
         in effect with respect to any Purchaser or when the Company first
         becomes subject to the periodic reporting requirements of the Exchange
         Act, whichever event shall first occur.

         The Company 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, provided, however, that any such tax, assessment, charge or levy need
not be paid if the validity thereof shall at the time be contested in good faith
by appropriate proceedings, and provided, further, that unless otherwise
approved by the Board, the Company 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. Unless otherwise approved by the
Board, the Company will promptly pay or cause to be paid when due, or in
conformance with customary trade terms, all other obligations incident to its
operations.

         The Company will keep its properties in good repair, working order and
condition, reasonable wear and tear excepted, and from time to time make all
needful and proper, or legally required, repairs, renewals, replacements,
additions and improvements thereto; and the Company will at all times comply
with each provision of all leases to which it is a party or under which it
occupies, or has possession of, property if the breach of such provision might
have a material adverse effect on the condition, financial or otherwise, or
operations of the Company.

         The Company will keep its assets which are of an insurable character
insured by financially sound and reputable insurers against loss or damage by
fire, extended coverage and explosion in amounts sufficient to prevent the
Company from becoming a co-insurer and not in any event less than 80% of the
insurable value of the property insured. The Company will maintain for itself,
with financially sound and reputable insurers, insurance against other hazards

                                       24
<PAGE>   25

and risks and liability to persons and property to the extent and in the manner
customary for companies in similar businesses similarly situated. After the
Closing Date, the Company will continue to maintain directors' and officers'
liability insurance in the amount of at least $1,000,000, if such coverage is
available at commercially reasonable rates, at all times after the Closing Date.
After the Closing Date, the Company will continue to maintain insurance on the
life of Dr. Lansing Taylor in the amount of $2,000,000, naming the Company as
the owner and beneficiary thereof, at all times after the Closing Date. The
Company shall give immediate written notice to insurers of loss or damage to the
property and shall promptly file proof of loss with insurers.

         The Company will keep true records and books of account in which full,
true and correct entries will be made of all dealings or transactions in
relation to its business and affairs in accordance with generally accepted
accounting principles applied on a consistent basis.

         The Company shall duly observe and conform to all valid requirements of
governmental authorities relating to the conduct of its businesses or to its
property or assets. Without limiting the generality of the foregoing, the
Company will:

                  (a) Comply with all minimum funding requirements applicable to
         any pension plans, employee benefit plans or employee contribution
         plans which are subject to ERISA or to the Code, and comply in all
         other respects with the provisions of ERISA and the provisions of the
         Code applicable to such plans;

                  (b) Comply with all applicable material laws of the United
         States and of each applicable jurisdiction relating to equal employment
         opportunity, any rules, regulations, administrative orders and
         Executive Orders relating thereto and the applicable material terms,
         relating to equal employment opportunity, of any contract, agreement or
         grant the Company has with, from or relating (by way of subcontract or
         otherwise) to any other contract, agreement or grant of, any federal or
         state governmental unit; and keep all records required to be kept, and
         file all reports, affirmative action plans and forms required to be
         filed, pursuant to any such applicable law or the terms of any such
         government contract; and

                  (c) So conduct its business that neither the Company nor any
         property owned or occupied by the Company is in violation of any
         Federal or State Environmental Law of any sort or in violation of any
         Federal or State "OSHA" Law.

         The Company shall maintain in full force and effect its corporate
existence, rights, government approvals and franchises and all licenses and
other rights to use patents, processes, licenses, trademarks, trade names or
copyrights owned or possessed by it and deemed by the Company to be necessary to
the conduct of its business.

         The Company will, from time to time, in accordance with the laws of the
state of its incorporation, 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

                                       25
<PAGE>   26

permit the payment of dividends on the Series B Preferred for a period of five
(5) years in the form of Common Stock and the conversion to Common Stock of all
the then outstanding Shares.

                  (a) The Company and each person hereafter employed by it with
         access to confidential information will enter into a Proprietary
         Information Agreement to the effect and in substantially the form of
         Exhibit D hereto or as otherwise approved by the Board.

                  (b) The Company will require all persons now or hereafter
         employed by the Company and designated as a "key person" by the
         Company's Board of Directors to execute an Employment Agreement in
         favor of the Company to the effect and in substantially the form of
         Exhibit H hereto or as otherwise approved by the Board, as a condition
         precedent to the employment of such individuals.

                  (c) The Company will cause all technological developments,
         inventions, discoveries or improvements made by employees of the
         Company to be fully documented in engineering notebooks in accordance
         with the prevailing industrial professional standards, and where
         possible and appropriate, cause all employees to file and prosecute
         United States and foreign patent applications relating to and
         protecting such developments.

         So long as the holders of the Series B Preferred retain the right to
elect one or more directors to the Board, the Company will maintain and preserve
in full force and effect the indemnification provisions described in Section
5.13.

         So long as any Shares or Conversion Shares are held by any Purchaser or
any transferee who is not a corporation, the Company will use its best efforts
to cause the Shares and, upon issuance, the Conversion Shares to qualify as
qualified small business stock within the meaning of Section 1202 of the Code,
provided that this Section 7.12 shall not require the Company to limit its gross
assets (within the meanings of Code Section 1202(d)(3)) to an amount that does
not exceed $50,000,000.

         The Company will use the proceeds from the sale of the Shares and the
Conversion Shares for the purposes described in Section 3.22 hereof.

         The Company agrees to reimburse each of the directors elected to the
Company's Board of Directors and, if an affiliate of a Purchaser is not serving
as a director on the Board of Directors, a representative of such Purchaser
entitled to attend meetings of the Board of Directors and committees thereof
pursuant to Section 7.2(c) hereof for their reasonable out-of-pocket travel and
lodging expenses in connection with attending Board of Directors' meetings and
performing their respective obligations and responsibilities as directors of the
Company.

         The Company will make any filings necessary to perfect in a timely
fashion exemptions from (i) the registration and prospectus delivery
requirements of the Securities Act and (ii) the registration or qualification
requirements of all applicable securities or blue sky laws of any state or other
jurisdiction, for the issuance of the Shares and the Conversion Shares to the
Purchasers.

                                       26
<PAGE>   27

         Not later than thirty (30) days after the Closing Date, the Company
will deliver to the Purchasers audited balance sheets of the Company dated
December 31, 1998 and December 31, 1999, respectively, and the related
statements of operations and accumulated deficit and cash flows for the years
then ended, together with the unqualified report thereon of
PricewaterhouseCoopers LLP. Such financial statements shall (i) present fairly,
in all material respects, the financial position of the Company as of such
dates, (ii) have been prepared in accordance with U.S. generally accepted
accounting principles, consistently-applied, except for those changes
promulgated by accounting authority, and (iii) show all material liabilities,
absolute or contingent, of the Company required to be recorded thereon in
accordance with U.S. generally accepted accounting principles as of the dates
thereof.

         The Company will cause any Subsidiary which it may now have and/or
which it may organize or acquire in the future and which the Company controls to
comply fully with all the terms and provisions of Sections 7.3, 7.4, 7.5, 7.6,
7.7, 7.8 and 7.10 to the same extent as if such Subsidiary or Subsidiaries were
the "Company" herein.

         The Company will use its reasonable best efforts to negotiate and
deliver to the Purchasers a side letter agreement with Carl Zeiss Holding Co.,
Inc. ("Zeiss"), a Delaware corporation, pursuant to which Zeiss will agree to
the special registration provisions set forth in Section 9.16 hereof with
respect to the securities owned by Zeiss as to which Zeiss is entitled to
registration rights pursuant to that certain Letter Agreement dated January 15,
1998 by and among the Company and Zeiss.

         The Company agrees that, so long as any Shares remain outstanding, the
Company (and each of its Subsidiaries, if any, unless the context otherwise
requires) will not do any of the following after the Closing Date without the
approval of a majority of the Board, which approval must include the approval of
each director elected to the Board by the holders of Series B Preferred (and, if
the holders of Series B Preferred have not designated their representative to be
elected to the Board, such approval must also include the approval of the
holders of a majority of the Series B Preferred outstanding):

         Make any substantial change in the character of its business.

         Become subject to, or permit any of its Subsidiaries which it controls
to become subject to, any agreement or instrument, which by its terms would
(under any circumstances) restrict the Company's right to perform any of its
obligations pursuant to the terms of this Agreement or any agreement
contemplated hereby, the Amended and Restated Certificate, the Financing
Documents, or the Company's By-laws (including, without limitation, all
obligations relating to payment of dividends on and making redemptions of the
Series B Preferred and conversions of the Series B Preferred).

         Hereafter issue, sell, grant or award any Equity Security or any option
to acquire any Equity Security to directors, officers, employees, consultants or
advisors to the Company, except for Equity Securities which are "Reserved
Employee Shares" within the meaning of Section 3(d)(i)(5)(C) of Article III,
Part B of the Amended and Restated Certificate.

                                       27
<PAGE>   28

         Create, incur, issue, assume, guarantee or otherwise become or remain
directly or indirectly liable for, or permit any Subsidiary to create, incur,
issue, assume, guarantee or otherwise become or remain directly or indirectly
liable for, any Indebtedness for borrowed money in excess of $1,000,000 in any
one fiscal year; provided that this Section 8.4 shall not apply to any
Indebtedness incurred pursuant to the Backstop Letter referred to in Section
3.11 of the Schedule of Exceptions.

         Enter into, or permit any Subsidiary which it controls to enter into,
any transaction with any Related Party or any of its or any Subsidiary's
Affiliates, except as otherwise expressly contemplated by this Agreement or
referred to in Section 3.11 hereto.

         Neither the Shares nor the Conversion Shares shall be transferable,
except upon the conditions specified in this Section 9, which conditions are
intended to insure compliance with the provisions of the Securities Act or, in
the case of Section 9.15 hereof, to assist in an orderly distribution of the
Company's securities. Each Purchaser will cause any proposed transferee of
Shares or Conversion Shares held by such Purchaser to agree to take and hold
those securities subject to the provisions and upon the conditions specified in
this Section 9.

         As used in this Section 9, the following terms shall have the following
respective meanings:

         "RESTRICTED SECURITIES" shall mean the securities of the Company
required to bear or bearing the legend set forth in Section 9.3 hereof.

         "REGISTRABLE SECURITIES" shall mean, from time to time, (i) the
Conversion Shares, less any Conversion Shares theretofore sold to the public,
and (ii) any shares of Common Stock issued as dividends on the Shares.

         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 effectiveness of such registration statement.

         "REGISTRATION EXPENSES" shall mean all expenses incurred by the Company
in compliance with Sections 9.5, 9.6 and 9.7 hereof, including, without
limitation, all registration and filing fees, printing expenses, fees and
disbursements of counsel for the Company, fees and expenses (not to exceed
$20,000) of one special counsel for all Holders chosen by the Holders of a
majority of the securities included in such registration, blue sky fees and
expenses, and the expense of any special audits incident to or required by any
such registration (but excluding the compensation of regular employees of the
Company, which shall be paid in any event by the Company).

         "SELLING EXPENSES" shall mean all underwriting discounts and selling
commissions applicable to the sale of Registrable Securities, and all fees and
disbursements of counsel for any Holder (other than the fees and expenses of one
special counsel for all Holders included within the definition of Registration
Expenses).

                                       28
<PAGE>   29

         "HOLDER" shall mean any holder of outstanding Shares, Conversion Shares
or Registrable Securities which have not been sold to the public.

         "INITIATING HOLDERS" shall mean any Purchaser (or their assignees under
Section 9.14 hereof) who in the aggregate are Holders of more than fifty percent
(50%) of the Registrable Securities, and, after any other Holder or Holders have
joined in a request by Initiating Holders, shall include such other Holder or
Holders.

         "TERMINATION DATE" shall mean, as to all Holders, the date that is five
(5) years after the closing of an Initial Public Offering, provided that as of
such date the Company is subject to and is in compliance with the periodic
reporting requirements of the Exchange Act and shares of the Common Stock are
actively traded on the Nasdaq National Market or other national securities
exchange. In addition, "Termination Date" as to a particular Holder shall mean
such date as of which (i) the Company is subject to and in compliance with the
periodic reporting requirements of the Exchange Act, (ii) shares of the Common
Stock are traded as described above, and (iii) such Holder is able, within the
ninety (90) day period immediately following such date, to transfer all of such
Holder's Registrable Securities in compliance with Rule 144 promulgated by the
Commission under the Securities Act.

         "OTHER SHAREHOLDERS" shall have the meaning set forth in Section
9.5(b).

         Each certificate representing (i) the Shares, or (ii) the Conversion
Shares, or (iii) any other securities issued in respect of the Shares or the
Conversion Shares upon any stock split, stock dividend, recapitalization,
merger, consolidation or similar event, shall (unless otherwise permitted or
unless the securities evidenced by such certificate shall have been registered
under the Securities Act) be stamped or otherwise imprinted with a legend
substantially in the following form (in addition to any legend required under
applicable state securities laws):

THESE SECURITIES HAVE NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS
AMENDED, OR ANY STATE SECURITIES LAWS. THEY MAY NOT BE SOLD OR OFFERED FOR SALE
IN THE ABSENCE OF AN EFFECTIVE REGISTRATION STATEMENT AS TO THE SECURITIES UNDER
SAID ACT AND ANY APPLICABLE STATE SECURITIES LAW OR THE AVAILABILITY OF AN
EXEMPTION FROM REGISTRATION UNDER SAID ACT AND ANY APPLICABLE STATE SECURITIES
LAWS.

         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 with such request, the
Company shall have received either the opinion referred to in Section 9.4(a)(i)
or the "no-action" letter referred to in Section 9.4(a)(ii), to the effect that
any transfer by such holder of the securities evidenced by such certificate will
not violate the Securities Act and applicable state securities laws.

                  (a) The holder of Restricted Securities by acceptance thereof
         agrees to comply in all respects with the provisions of this Section
         9.4. Prior to any proposed transfer of

                                       29
<PAGE>   30

         any Restricted Securities (other than under circumstances described in
         Sections 9.5, 9.6 and 9.7 hereof and other than to a member of such
         holder's Group, as defined below), the holder thereof shall give
         written notice (or oral notice in the case of transactions in
         compliance with Rule 144) to the Company of such holder's intention to
         effect such transfer. Each such notice shall describe the manner and
         circumstances of the proposed transfer in sufficient detail, and shall
         be accompanied (except in transactions in compliance with Rule 144) by
         either (i) a written opinion of Kirkland & Ellis or other legal counsel
         (including counsel for the holder who also may be an employee of the
         holder) who shall be reasonably satisfactory to the Company, addressed
         to the Company and reasonably satisfactory in form and substance to the
         Company's counsel, to the effect that the proposed transfer of the
         Restricted Securities may be effected without registration under the
         Securities Act and applicable state securities laws, 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, provided, that in the case of a transfer of
         Restricted Securities to a member of a holder's Group (as such term is
         defined in the Shareholders' Agreement), no such opinion of counsel or
         no-action letter shall be necessary, provided that the transferee
         agrees in writing to be subject to the restrictions on transfer of the
         Restricted Securities to the same extent as if such transferee were
         originally a party signatory to this Agreement. Upon receipt by the
         Company of such notices and accompanying opinion or "no-action" letter,
         if required, the holder of such Restricted Securities shall be entitled
         to transfer such Restricted Securities in accordance with the terms of
         the notice delivered by the holder to the Company. Each certificate
         evidencing the Restricted Securities transferred as above provided
         shall bear the appropriate restrictive legend set forth in Section 9.3
         above, except that such certificate need not bear such restrictive
         legend if such legend is no longer required if the opinion of counsel
         or "no-action" letter referred to above is to the further effect that
         such legend is not required in order to establish compliance with any
         provisions of the Securities Act or applicable state securities laws or
         if the transaction is made, to the Company's reasonable satisfaction,
         in compliance with Rule 144. Notwithstanding anything to the contrary
         contained in this Section 9.4(a), no holder of Restricted Securities
         will transfer any of such Restricted Securities to any member of such
         holder's Group that is not an "accredited investor" (within the meaning
         of Commission Rule 501 of Regulation D) at the time of such transfer,
         except under the circumstances described in Sections 9.5, 9.6 and 9.7
         hereof and except in transactions in compliance with Rule 144.

                  (b) With a view to making available the benefits of certain
         rules and regulations of the Commission and applicable state securities
         laws which may permit the sale of the Restricted Securities without
         registration, the Company agrees to (i) make available to the holder of
         Restricted Securities and any proposed transferee current financial and
         other information about the Company and an adequate opportunity for the
         proposed transferee to visit the Company's offices and discuss its
         affairs with management and (ii) use its best efforts to otherwise
         cooperate with such holder and such transferee, all as may be
         reasonably required by such holder or proposed transferee.

                                       30
<PAGE>   31

                  (a) REQUEST FOR REGISTRATION. If at any time after January 1,
         2001, the Company shall receive from Initiating Holders a written
         request that the Company effect a registration with respect to all or a
         part of the Registrable Securities, the Company will, without limiting
         any other rights under this Section 9:

                           (i) promptly give written notice of the proposed
                  registration to all other Holders; and

                           (ii) as soon as practicable, use its diligent best
                  efforts to effect such registration (including, without
                  limitation, the execution of an undertaking to file
                  post-effective amendments, appropriate qualification under
                  applicable blue sky or other state securities laws and
                  appropriate compliance with applicable regulations issued
                  under the Securities Act) as may be so requested and as would
                  permit or facilitate the sale and distribution of all or such
                  portion of such Registrable Securities as are specified in
                  such request, together with all or such portion of the
                  Registrable Securities of any Holder or Holders joining in
                  such request as are specified in a written request given by
                  such Holder or Holders within fifteen (15) days after receipt
                  of such written notice from the Company; provided that the
                  Company shall not be obligated to effect, or to take any
                  action to effect, any such registration pursuant to this
                  Section 9.5:

                                    (A) after the Company has effected one (1)
                           such registration pursuant to this Section 9.5(a) and
                           such registration has been declared or ordered
                           effective and the sales of such Registrable
                           Securities shall have closed; or

                                    (B) if the request for registration does not
                           request the registration of Registrable Securities
                           with a proposed public offering price of $10,000,000
                           or more.

         Subject to Section 9.5(a)(ii), the Company shall file a registration
statement covering the Registrable Securities so requested to be registered as
soon as practicable after receipt of the request or requests of the Initiating
Holders.

         The registration statement filed pursuant to the request of the
Initiating Holders may, subject to the provisions of Section 9.5(b) below,
include other securities of the Company which are held by officers or directors
of the Company or which are held by parties who, by virtue of agreements with
the Company, are entitled to include their securities in any such registration.

         (b) UNDERWRITING. If the Initiating Holders 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 9.5 and the Company shall include such information in the written
notice referred to in subsection 9.5(a)(i) above. The right of any Holder to
registration pursuant to this Section 9.5 shall be conditioned upon such
Holder's participation in such underwriting and the inclusion of such Holder's
Registrable Securities in the

                                       31
<PAGE>   32

underwriting (unless otherwise mutually agreed by a majority in interest of the
Initiating Holders and such Holder) to the extent provided herein.

         If officers or directors of the Company holding other securities of the
Company shall request inclusion in any registration pursuant to this Section
9.5, or if holders of securities of the Company who are entitled, by contract
with the Company, to have securities included in such registration (the "Other
Shareholders") request such inclusion, the Initiating Holders shall, on behalf
of all Holders, offer to include the securities of such officers, directors and
Other Shareholders in the underwriting and may condition such offer on their
acceptance of all applicable provisions of this Section 9. The Company shall
(together with all Holders, officers, directors and Other Shareholders proposing
to distribute their securities through such underwriting) enter into an
underwriting agreement in customary form with the representative of the
underwriter or underwriters selected for such underwriting by a majority in
interest of the Initiating Holders and reasonably acceptable to the Company.

         Notwithstanding any other provision of this Section 9.5, if the
representative of the underwriter or underwriters advises the Initiating Holders
in writing that marketing factors make it advisable to impose a limitation on
the number of shares to be underwritten, the securities of the Company (other
than Registrable Securities) held by officers or directors of the Company and by
Other Shareholders shall be excluded from such registration to the extent so
required by such limitation and if a limitation of the number of shares is still
required, the Initiating Holders shall so advise all Holders of Registrable
Securities requesting registration, and the number of shares of Registrable
Securities that may be included in the registration and underwriting on behalf
of such Holders shall be reduced as required, such reduction to be allocated
among such Holders in proportion, as nearly as practicable, to the respective
amounts of Registrable Securities held by such persons at the time of filing the
Registration Statement.

         If any Holder of Registrable Securities, officer, director or Other
Shareholder above disapproves of the terms of the underwriting, such party may
elect to withdraw therefrom by written notice to the Company, the underwriter
and the Initiating Holders. The securities so withdrawn shall also be withdrawn
from registration.

         If the underwriter has not limited the number of Registrable Securities
or other securities to be underwritten, the Company may include its securities
for its own account in such registration if the underwriter so agrees and if the
number of Registrable Securities and other securities which would otherwise have
been included in such registration and underwriting will not thereby be limited.

         (c) TERMINATION. The Company's obligations under this Section 9.5 shall
terminate, as to any Holder, on the first Termination Date applicable to such
Holder.

                  (a) NOTICE OF REGISTRATION. If the Company shall determine to
         register any of its securities either for its own account or the
         account of a security holder or holders exercising their respective
         demand registration rights, other than a registration relating solely
         to employee benefit plans, or a registration relating solely to a
         Commission Rule

                                       32
<PAGE>   33

         145 transaction, or a registration on any registration form which does
         not permit secondary sales, the Company will:

                           (i) promptly give to each Holder written notice
                  thereof (which shall include a list of the jurisdictions in
                  which the Company intends to attempt to qualify such
                  securities under the applicable blue sky or other state
                  securities laws); and

                           (ii) include in such registration (and any related
                  qualification under blue sky laws or other compliance), and in
                  any underwriting involved therein, all the Registrable
                  Securities specified in a written request or requests, made by
                  any Holder within fifteen (15) days after receipt of the
                  written notice from the Company described in clause (i) above,
                  except as set forth in subsection 9.6(b) below.

                  (b) UNDERWRITING. 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 as part of the
         written notice given pursuant to subsection 9.6(a)(i). In such event,
         the right of any Holder to registration pursuant to Section 9.6 shall
         be conditioned upon such Holder's participation in such underwriting
         and the inclusion of such Holder's Registrable Securities in the
         underwriting to the extent provided herein. All Holders proposing to
         distribute their securities through such underwriting shall (together
         with the Company, directors and officers 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 9.6, if the
underwriter determines that marketing factors require a limitation on the number
of shares to be underwritten, the underwriter may (subject to the allocation
priority set forth below) exclude from such registration and underwriting some
or all of the Registrable Securities which would otherwise be underwritten
pursuant hereto. The Company shall so advise all holders of securities
requesting registration, and the number of shares of securities that are
entitled to be included in the registration and underwriting shall be allocated
in the following manner: (i) securities (other than Registrable Securities) held
by officers or directors of the Company and by Other Shareholders shall be
excluded from such registration to the extent so required by such limitation,
and (ii) if a limitation of the number of shares to be underwritten is still
required, the Company shall so advise all Holders of Registrable Securities
requesting registration, and the number of shares of Registrable Securities that
may be included in the registration and underwriting on behalf of such Holders
shall be reduced as required, such reduction to be allocated among such Holders
in proportion, as nearly as practicable, to the respective amounts of
Registrable Securities held by such persons at the time of filing the
registration statement.

         If any Holder of Registrable Securities or any officer, director or
Other Shareholder disapproves of the terms of any such underwriting, such party
may elect to withdraw therefrom by written notice to the Company and the
underwriter. Any Registrable Securities or other

                                       33
<PAGE>   34

securities excluded or withdrawn from such underwriting shall be withdrawn from
such registration.

         (c) TERMINATION. The Company's obligations under this Section 9.6 shall
terminate, as to any Holder, on the first Termination Date applicable to such
Holder.

         The Company shall use its reasonable best efforts to qualify for the
use of Form S-3 or any comparable or successor form or forms of the Commission;
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 the Exchange Act following the effective date of the first registration, if
any, of any securities of the Company on Form S-1. After the Company has
qualified for the use of Form S-3, in addition to the rights contained in the
foregoing provisions of this Section 9, the Holders of Registrable Securities
shall have the right to request registrations on Form S-3 (by written request
stating the number of shares of Registrable Securities to be disposed of and the
intended method of disposition of such shares by such Holder or Holders),
subject only to the following:

                           (i) No request made under this Section 9.7 shall
                  require a registration statement requested therein to become
                  effective (a) prior to ninety (90) days after the effective
                  date of a registration statement filed by the Company covering
                  a firm commitment underwritten public offering of Common Stock
                  or (b) prior to the effective date of a registration statement
                  referred to in (a) above if the Company shall theretofore have
                  given written notice of such registration statement to the
                  Holders of Registrable Securities pursuant to subsection
                  9.5(a) or 9.6(a) and shall have thereafter pursued the
                  preparation, filing and effectiveness of such registration
                  statement with diligence;

                           (ii) The Company shall not be required to effect a
                  registration pursuant to this Section 9.7 unless the
                  Registrable Securities requested to be registered pursuant to
                  this Section 9.7 have a proposed public offering price of
                  $500,000 or more; and

                           (iii) The Company shall not be required to effect
                  more than two (2) registrations pursuant to this Section 9.7.

         The Company shall give notice to all Holders of Registrable Securities
of the receipt of a request for registration pursuant to this Section 9.7 and
shall provide a reasonable opportunity for other Holders to participate in the
registration, and, if the intended method of disposition specified as aforesaid
is an underwritten public offering, participation by the Company and other
holders of Common Stock shall be on the basis set forth in Section 9.5(b) above.
Subject to the foregoing, the Company will use its best efforts to effect
promptly the registration of all shares of Registrable Securities on Form S-3 to
the extent requested by the Holder or Holders thereof for purposes of
disposition.

         The Company's Obligations under this Section 9.7 shall terminate, as to
any Holder, on the first Termination Date applicable to such Holder.

                                       34
<PAGE>   35

         The Company shall bear all Registration Expenses incurred in connection
with any registration, qualification and compliance by the Company pursuant to
Sections 9.5, 9.6 and 9.7 hereof. Notwithstanding the foregoing, the Company
shall not be required to pay for any expenses of any registration proceeding
begun pursuant to Section 9.5 if the registration request is subsequently
withdrawn at the request of the Holders of a majority of the Registrable
Securities to be registered (in which case all participating holders shall bear
such expenses pro rata on the basis of the number of their shares so
registered); provided, however, that (i) the Company shall be required to pay
for any expenses of any registration proceeding begun pursuant to Section 9.5 if
the registration request is subsequently withdrawn at the request of the Holders
of a majority of the Registrable Securities to be registered, if at or prior to
the time of such withdrawal, the Holders shall have learned of a material
adverse change in the condition, business, or prospects of the Company that was
not known to the Holders at the time of their request and have withdrawn the
request with reasonable promptness following disclosure to the Holders by the
Company of such material adverse change, and (ii) in addition to its obligations
under clause (i) of this provision, the Company shall be required to pay for the
expenses of not more than one additional registration proceeding begun pursuant
to Section 9.5 if the registration request is subsequently withdrawn, at the
request of the Holders of a majority of the Registrable Securities to be
registered, for any other reason. All Selling Expenses shall be borne by the
holders of the securities so registered pro rata on the basis of the number of
their shares so registered.

         In the case of each registration effected by the Company pursuant to
this Section 9, the Company will keep each Holder advised in writing as to the
initiation of each registration and as to the completion thereof. Except as
provided in Section 9.7, at its expense, the Company will:

                  (a) keep such registration effective for a period of one
         hundred twenty (120) days or until the Holder or Holders have completed
         the distribution described in the registration statement relating
         thereto, whichever first occurs, provided, however, that such one
         hundred twenty (120) day period shall be extended for a period of time
         equal to the period the Holder refrains from selling any securities
         included in such registration in accordance with the provisions of
         Section 9.15 hereof;

                  (b) furnish such number of prospectuses and other documents
         incident thereto as a Holder from time to time may reasonably request;

                  (c) Use its best efforts to register or qualify the
         Registrable Securities under the securities or blue-sky laws of such
         jurisdictions as any Holder may request; provided, however, that the
         Company shall not be obligated to register or qualify such Registrable
         Securities in any particular jurisdiction in which the Company would be
         required to execute a general consent to service of process in order to
         effect such registration, qualification or compliance, unless the
         Company is already subject to service in such jurisdiction and except
         as may be required by the Securities Act or applicable rules or
         regulations thereunder; and

                                       35
<PAGE>   36

                  (d) Use its best efforts to cause the Common Stock to be
         listed on a national securities exchange or the Nasdaq National Market.

                  (a) The Company, with respect to each registration,
         qualification and compliance effected pursuant to this Section 9, will
         indemnify and hold harmless each Holder, each of its officers,
         directors and partners, and each party controlling such Holder, and
         each underwriter, if any, and each party who controls any underwriter,
         against all claims, losses, damages and liabilities (or actions in
         respect thereof) arising out of or based on any untrue statement (or
         alleged untrue statement) of a material fact contained in any
         prospectus, offering circular or other document (including any related
         registration statement, notification or the like) incident to any such
         registration, qualification or compliance, or based on any omission (or
         alleged omission) to state therein a material fact required to be
         stated therein or necessary to make the statements therein not
         misleading, or any violation by the Company of the Securities Act or
         any rule or regulation thereunder applicable to the Company and
         relating to action or inaction required of the Company in connection
         with any such registration, qualification or compliance, and will
         reimburse each such Holder, each of its officers, directors and
         partners, and each party controlling such Holder, each such underwriter
         and each party who controls any such underwriter, for any legal and any
         other expenses incurred in connection with investigating or defending
         any such claim, loss, damage, liability or action, provided that the
         Company will not be liable in any such case to the extent that any such
         claim, loss, damage, liability or expense arises out of or is based on
         any untrue statement or omission based solely upon written information
         furnished to the Company by such Holder or underwriter, as the case may
         be, and stated to be specifically for use therein.

                  (b) Each Holder and Other Shareholder will, if Registrable
         Securities held by such party are included in the securities as to
         which such registration, qualification or compliance is being effected,
         indemnify and hold harmless the Company, each of its directors and
         officers and each underwriter, if any, of the Company's securities
         covered by such a registration statement, each party who controls the
         Company or such underwriter, each other such Holder and Other
         Shareholder and each of their respective officers, directors and
         partners, and each party controlling such Holder or Other Shareholder,
         against all claims, losses, damages and liabilities (or actions in
         respect thereof) arising out of or based on any untrue statement (or
         alleged untrue statement) of a material fact contained in any such
         registration statement, prospectus, offering circular or other
         document, or any 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
         such Holders, Other Shareholders, directors, officers, partners,
         parties, underwriters or control persons for any legal or any other
         expenses reasonably incurred in connection with investigating or
         defending any such claim, loss, damage, liability or action, in each
         case to the extent, but only to the extent, that such untrue statement
         (or alleged untrue statement) or omission (or alleged omission) is made
         in such registration statement, prospectus, offering circular or other
         document solely in reliance upon and in conformity with written
         information furnished to the Company by such Holder or Other
         Shareholder and stated to be specifically for use

                                       36
<PAGE>   37

         therein; provided, however, that the obligations of such Holders and
         Other Shareholders hereunder shall be limited to an amount equal to the
         proceeds to each such Holder or Other Shareholder of securities sold as
         contemplated herein.

                  (c) Each party entitled to indemnification under this Section
         9.10 (the "Indemnified Party") shall give notice to the party required
         to provide indemnification (the "Indemnifying Party") promptly after
         such Indemnified Party has actual knowledge of any claim as to which
         indemnity may be sought, and shall permit the Indemnifying Party to
         assume the defense of any such claim or any litigation resulting
         therefrom, provided that counsel for the Indemnifying Party, who shall
         conduct the defense of such claim or any litigation resulting
         therefrom, shall be approved by the Indemnified Party (whose approval
         shall not unreasonably be withheld), and the Indemnified Party may
         participate in such defense at such party's expense (unless the
         Indemnified Party shall have been advised by counsel that actual or
         potential differing interests or defenses exist or may exist between
         the Indemnifying Party and the Indemnified Party, in which case such
         expense shall be paid by the Indemnifying Party), and provided further
         that the failure of any Indemnified Party to give notice as provided
         herein shall not relieve the Indemnifying Party of its obligations
         under this Section 9. No Indemnifying Party, in the defense of any such
         claim or litigation, shall, except with the consent of each Indemnified
         Party, consent to entry of any judgment or enter into any settlement
         which (i) 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 litigation, (ii)
         includes equitable or other non-monetary relief, (iii) involves
         admission of criminal or quasi-criminal activity, or (iv) any admission
         or implication of bad faith, unfair dealing, self-dealing, dishonesty
         or any similar claim which could reasonably be expected to be
         detrimental to or injure such Indemnified Party's reputation or future
         business prospects.

                  (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 Restricted Securities exercising rights under this
         Agreement, or any controlling person of any such holder, makes a claim
         for indemnification pursuant to this Section 9.10 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
         9.10 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 9.10; 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 Restricted 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 will be required to
         contribute any amount in excess of the public offering price of all
         such Restricted Securities offered by it pursuant to such registration
         statement; and (B) no

                                       37
<PAGE>   38

         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.

         Each Holder of Registrable Securities, and each Other Shareholder
holding securities included in any registration, shall furnish to the Company
such information regarding such Holder or Other Shareholder as the Company may
reasonably request in writing and as shall be reasonably required in connection
with any registration, qualification or compliance referred to in this Section
9.

         From and after the date of this Agreement, the Company shall not enter
into any agreement, or amend any existing agreement, with any holder or
prospective holder of any securities of the Company giving such holder or
prospective holder the right to require the Company to initiate any registration
of any securities of the Company; provided that this Section 9.12 shall not
limit the right of the Company to enter into any agreements, or amend any
existing agreement, with any holder or prospective holder of any securities of
the Company giving such holder or prospective holder the right to require the
Company, upon any registration of any of its securities, to include, among the
securities which the Company is then registering, securities owned by such
holder and provided further that the Board may waive the requirement that the
Company not enter into any agreement, or amend any existing agreement, giving a
holder of any securities of the Company the right to require the Company to
initiate registration of any securities of the Company, provided that, if such
registration rights are more favorable than those granted to the Holders
pursuant to this Section 9, then the terms of this Section 9 shall
simultaneously be amended so as to include herein for the benefit of the Holders
such more favorable terms. In addition, any right given by the Company to any
holder or prospective holder of the Company's securities in connection with the
registration of securities shall be conditioned such that it shall be (i)
consistent with the provisions of this Section 9 and with the rights of the
Holders provided in this Agreement, and (ii) require the inclusion of
Registrable Securities (within the meaning of this Agreement) in any
registration required by any such holder or prospective holder on the same basis
as securities of Other Shareholders are required to be included in registrations
effected pursuant to Sections 9.5 and 9.6 of this Agreement.

         With a view to making available the benefits of certain rules and
regulations of the Commission which may permit the sale of the Restricted
Securities to the public without registration, the Company agrees to:

                  (a) Make and keep public information available, as those terms
         are understood and defined in Rule 144 under the Securities Act, at all
         times from and after ninety (90) days following the effective date of
         the first registration under the Securities Act filed by the Company
         for an offering of its securities to the general public;

                  (b) Use its best efforts to file with the Commission in a
         timely manner all reports and other documents required of the Company
         under the Securities Act and the Exchange Act at any time after it has
         become subject to such reporting requirements; and

                                       38
<PAGE>   39

                  (c) So long as a Purchaser owns any Restricted Securities,
         furnish to the Purchasers forthwith upon request a written statement by
         the Company as to its compliance with the reporting requirements of
         Rule 144 (at any time from and after ninety (90) days following the
         effective date of the first registration statement in connection with
         an offering of its Securities to the general public), and of the
         Securities Act and the Exchange Act (at any time after it has become
         subject to such reporting requirements), a copy of the most recent
         annual or quarterly report of the Company, and such other reports and
         documents so filed as a Purchaser may reasonably request in availing
         itself of any rule or regulation of the Commission allowing a Purchaser
         to sell any such securities without registration.

         The rights to cause the Company to register securities granted by the
Company under this Section 9 may be assigned by any Holder to a transferee or
assignee of at least 50,000 shares of Registrable Securities (as adjusted for
stock splits, combinations and other similar events affecting the Registrable
Securities), provided that the Company is given written notice at the time of or
within a reasonable time after said transfer, stating the name and address of
said transferee or assignee and identifying the securities with respect to which
such registration rights are being assigned, and provided further that the
transferee or assignee of such rights agrees to be bound by the provision of
this Section 9. No Holder of Registrable Securities shall have any rights under
this Section 9 unless such Holder shall have executed this Agreement or an
instrument in which it agrees to be bound by the terms of this Section 9.

         Each Purchaser agrees, if requested by the Company and an underwriter
of the Company's Common Stock (or other securities), not to sell or otherwise
transfer or dispose of any Common Stock (or other securities) of the Company
held by it during the one hundred eighty (180) day period following the
effective date of a registration statement of the Company filed under the
Securities Act, provided that:

                  (a) such agreement only applies to the first such registration
         statement of the Company including securities to be sold on its behalf
         to the public in an underwritten offering; and

                  (b) all Holders, Other Shareholders and officers and directors
         of the Company enter into similar agreements.

         Such agreement shall be in writing in a form satisfactory to the
Company and such underwriter. The Company may impose stop-transfer instructions
with respect to the shares (or securities) subject to the foregoing restriction
until the end of said one hundred eighty (180) day period.

         The Company, each Purchaser that has registration rights under the
Series A Purchase Agreement (in its capacity as a holder of Series A Preferred)
and each Purchaser (in its capacity as a holder of Series B Preferred) hereby
agree that in the event the Company shall determine to register any of its
securities for its own account, the second paragraph of Section 9.6(b) hereof
and the second paragraph of Section 9.6(b) of the Series A Purchase Agreement
shall each be interpreted such that:

                                       39
<PAGE>   40

                  (a) the words "Registrable Securities" in each such paragraph
         shall include Registrable Securities (as defined in the Series A
         Purchase Agreement) and Registrable Securities (as defined herein); and

                  (b) the words "Holders" in each such paragraph shall include
         Holders (as defined in the Series A Purchase Agreement) and Holders (as
         defined herein).

The intent of this Section 9.16 is to provide and ensure that in the event of a
Company-initiated registration under Section 9.6 in which the underwriters
advise the Company that marketing factors make it advisable to impose a
limitation on the number of shares underwritten, any cutbacks on the number of
shares held by the holders of Series A Preferred and the holders of Series B
Preferred included in the offering shall be pro rata among such persons.

         As used in this Agreement or in the Financing Documents, capitalized
terms shall have the respective meanings set forth in this Agreement (including,
without limitation, in Section 9.2 hereof) or set forth below or in the Section
of this Agreement referred to below:

         AFFILIATE shall mean, as to any entity or person, any natural person,
corporation, business trust, association, company, partnership, joint venture or
other entity or government agency or political subdivision which directly or
indirectly controls, is controlled by or is under common control with such
entity or person.

         AMENDED AND RESTATED CERTIFICATE - Section 1.1.

         ANNUAL PLAN - Section 7.1(e).

         BALANCE SHEET - Section 3.7.

         BRIDGE INVESTORS shall mean Axiom Venture Partners II Limited
Partnership, InterWest Partners VI, LP, InterWest Investors VI, LP, Delphi
Ventures III, L.P., Delphi BioInvestments III, L.P., Oxford Bioscience Partners
II, L.P., Oxford Bioscience Partners (Bermuda) II Limited Partnership and Oxford
Bioscience Partners (GS-Adjunct) II, L.P., together. Each of the Bridge
Investors is also a Purchaser for purposes of this Agreement.

         BRIDGE LOAN SUBSCRIPTION AGREEMENTS shall mean the several Subscription
Agreements dated as of November 29, 1999 and November 30, 1999 between the
Company and each Bridge Investor, as any of the same may have been amended from
time to time.

         BRIDGE NOTES shall mean, collectively,

                  (i) that certain convertible demand note dated November 30,
         1999, in the original principal amount of $550,000.00, from the Company
         to Axiom Venture Partners II Limited Partnership,

                                       40
<PAGE>   41

                  (ii) that certain convertible demand note dated November 30,
         1999, in the original principal amount of $22,799.00, from the Company
         to InterWest Investors VI, LP,

                  (iii) that certain convertible demand note dated November 30,
         1999, in the original principal amount of $727,201.00, from the Company
         to InterWest Partners VI, LP,

                  (iv) that certain convertible demand note dated November 30,
         1999, in the original principal amount of $294,694.00, from the Company
         to Delphi Ventures III, L.P.,

                  (v) that certain convertible demand note dated November 30,
         1999, in the original principal amount of $5,306.00, from the Company
         to Delphi BioInvestments III, L.P.,

                  (vi) that certain convertible demand note dated December 1,
         1999, in the original principal amount of $73,235.00, from the Company
         to Oxford Bioscience Partners II, L.P.,

                  (vii) that certain convertible demand note dated December 1,
         1999, in the original principal amount of $54,883.40, from the Company
         to Oxford Bioscience Partners (Bermuda) II Limited Partnership, and

                  (viii) that certain convertible demand note dated December 1,
         1999, in the original principal amount of $71,881.60, from the Company
         to Oxford Bioscience Partners (GS-Adjunct) II, L.P.

         BRIDGE WARRANTS shall mean the warrants to be issued to the Bridge
Investors upon consummation of the transactions contemplated by this Agreement,
which warrants will entitle each Bridge Investor to purchase the number of
shares of Common Stock set forth opposite its name below for a price per share
equal to $12.07:

          Axiom Venture Partners II Limited Partnership                   25,056
          ----------------------------------------------------------------------
          InterWest Investors VI, LP                                       1,039
          ----------------------------------------------------------------------
          InterWest Partners VI, LP                                       33,129
          ----------------------------------------------------------------------
          Delphi Ventures III, L.P.                                       13,425
          ----------------------------------------------------------------------
          Delphi BioInvestments III, L.P.                                    242
          ----------------------------------------------------------------------
          Oxford Bioscience Partners II, L.P.                              3,335
          ----------------------------------------------------------------------
          Oxford Bioscience Partners (Bermuda) II, Limited Partnership     2,500
          ----------------------------------------------------------------------
          Oxford Bioscience Partners (GS-Adjunct) II, L.P.                 3,274

         BUSINESS - Section 3.21.

         BUSINESS PLAN - Section 3.1.

                                       41
<PAGE>   42

         BOARD shall mean the entire Board of Directors of the Company.

         CLOSING - Section 2.1.

         CLOSING DATE - Section 2.1.

         CODE - Section 3.30.

         COMMISSION shall mean the Securities and Exchange Commission or any
other federal agency at the time administering the Securities Act.

         COMMON SHAREHOLDERS - Section 5.11.

         COMMON STOCK - Section 3.4.

         CONVERSION SHARES shall mean at any time, shares of Common Stock (i)
issued and then outstanding upon the conversion of the Series B Preferred
purchased under this Agreement, (ii) issuable upon the conversion of the Series
B Preferred purchased under this Agreement, and (iii) issued and then
outstanding or issuable in respect of the Common Stock referred to in clause (i)
of this definition upon any stock split, stock dividend, recapitalization or
similar event.

         EMPLOYMENT AGREEMENT - Section 3.20.

         ENVIRONMENTAL CLAIM shall mean any and all administrative, regulatory
or judicial actions, suits, demands, demand letters, directives, claims, liens,
investigations, proceedings or notices of compliance or violation (written or
oral) by any person or entity (including any governmental authority) alleging
potential liability (including, without limitation, potential liability for
enforcement, investigatory costs, cleanup costs, governmental response costs,
removal costs, remedial costs, natural resources damages, property damages,
personal injuries, or penalties) arising out of, based on or resulting from (a)
the presence, or Release or threatened Release into the environment, of any
Hazardous Material at any location, whether owned, operated, leased or managed
by the Company or its Subsidiaries; or (b) circumstances forming the basis of
any violation, or alleged violation, of any Environmental Law; or (c) any and
all claims by any third party seeking damages, contribution, indemnification,
cost recovery, compensation or injunctive relief resulting from the presence or
Release of any Hazardous Materials.

         ENVIRONMENTAL LAWS shall mean all laws or orders relating to the
regulation or protection of human health, safety or the environment (including,
without limitation, ambient air, soil, surface water, ground water, wetlands,
land or subsurface strata), including, without limitation, laws and regulations
relating to Releases or threatened Releases of Hazardous Materials, or otherwise
relating to the manufacture, processing, distribution, use, treatment, storage,
disposal, transport, recycling or handling of Hazardous Materials.

         ENVIRONMENTAL PERMITS - Section 3.23.

                                       42
<PAGE>   43

         EQUITY SECURITIES shall mean any stock or similar security, including
without limitation securities containing equity features and securities
containing profit participation features, or any security convertible or
exchangeable, with or without consideration, into any stock or similar security,
or any security carrying any warrant or right to subscribe to or purchase any
stock or similar security, or any such warrant or right.

         ERISA - Section 3.23.

         EXCHANGE ACT shall mean the Securities Exchange Act of 1934, as
amended, and any regulations issued pursuant thereto.

         FINANCING DOCUMENTS shall mean collectively, the Shareholders'
Agreement, the Management Rights Letters and all other documents set forth in
any other schedules or exhibits hereto, under which, upon its execution thereof,
the Company or any Subsidiary shall have an obligation to any Purchaser, all in
the respective forms thereof as executed and as amended from time to time.

         FINANCIAL STATEMENTS - Section 3.7.

         GROUP shall mean:

                           (i) in the case of any Purchaser who is an
                  individual, such Purchaser or any Affiliate of such Purchaser;

                           (ii) in the case of any Purchaser which is a
                  pass-through entity, (A) such pass-through entity and any of
                  its partners, members or other equity owners, (B) any
                  corporation or other business organization to which such
                  pass-through entity shall sell all or substantially all of its
                  assets or with which it shall be merged or consolidated and
                  (C) any Affiliate of such pass-through entity; and

                           (iii) in the case of any Purchaser which is a
                  corporation, (A) any such corporation, its parent and any of
                  such corporation's or parent's subsidiaries, (B) any
                  corporation or other business organization to which such
                  corporation shall sell all or substantially all of its assets
                  or with which it shall be merged, and (C) any Affiliate of
                  such corporation.

         HAZARDOUS MATERIALS shall mean (a) any petroleum or petroleum products,
radioactive materials, asbestos in any form that is or could become friable,
above ground or underground storage tanks and compressors or other equipment
that contain polychlorinated biphenyls ("PCBs"); and (b) any chemicals,
materials or substances which are now defined as or included in the definition
of "hazardous substances," "hazardous wastes," "hazardous materials," "extremely
hazardous wastes," "restricted hazardous wastes," "toxic substances," "toxic
pollutants," "pollutants," "contaminants" or words of similar import, under any
Environmental Law; and (c) any other chemical, material, substance or waste,
exposure to which is now prohibited, limited or regulated under any
Environmental Law.

                                       43
<PAGE>   44

         HOLDER - Section 9.2.

         INDEBTEDNESS shall mean any obligation of the Company, contingent or
otherwise, which under generally accepted accounting principles is required to
be shown on the balance sheet of the Company as a liability. Any obligation
secured by a lien or security interest on, or payable out of the proceeds of or
production from, property of the Company shall be deemed to be Indebtedness even
though such obligation is not assumed by the Company.

         INITIAL PUBLIC OFFERING shall mean the first underwritten public
offering pursuant to an effective registration statement under the Securities
Act covering the offering and sale of Common Stock for the account of the
Company, on a firm commitment basis.

         MANAGEMENT RIGHTS LETTERS - Section 5.12.

         PERSON shall include all natural persons, corporations, business
trusts, associations, companies, partnerships, joint ventures and other entities
and governments and agencies and political subdivisions.

         PROPRIETARY INFORMATION AGREEMENT - Section 3.20.

         QUALIFIED PUBLIC OFFERING - shall mean the first underwritten public
offering following the date hereof pursuant to an effective registration
statement under the Securities Act covering the offering and sale of Common
Stock for the account of the Company, on a firm commitment basis in which (i)
the aggregate gross proceeds to Company equal or exceed Twenty Million Dollars
($20,000,000), and (ii) the public offering price per share of Common Stock
equals or exceeds an amount equal to two and one-half (2.5) times the initial
Series B Conversion Price (as defined in the Amended and Restated Certificate)
of the Series B Preferred.

         REINCORPORATION MERGER - Section 3.31

         RELATED PARTY shall mean any officer, director, employee or consultant
of the Company or any Subsidiary or any holder of 5% or more of any class of
capital stock of the Company or any Subsidiary or any member of the immediate
family of any such officer, director, employee, consultant or shareholder or any
entity controlled by any such officer, director, employee, consultant or
shareholder or a member of the immediate family of any such officer, director,
employee, consultant or shareholder.

         RELEASE shall mean any release, spill, emission, leaking, injection,
deposit, disposal, discharge, dispersal, leaching or migration into the
atmosphere, soil, surface water, ground water or property.

         RESTRICTED SECURITIES - Section 9.2.

         SECURITIES ACT shall mean the Securities Act of 1933, as amended, and
regulations issued pursuant thereto.

                                       44
<PAGE>   45

         SERIES A PREFERRED - Section 3.4.

         SERIES A PREFERRED SHAREHOLDERS - 5.11.

         SERIES A PURCHASE AGREEMENT shall mean the Series A Preferred Stock and
Warrant Purchase Agreement dated as of January 21, 1998 by and among the Company
and each of the parties listed on the Schedule of Purchasers attached thereto.

         SERIES B PREFERRED - Section 1.1

         SHAREHOLDERS' AGREEMENT - Section 5.11.

         SHARES - Section 1.2.

         SUBSIDIARY shall mean any corporation, partnership, joint venture,
association or other business entity at least 50% of the outstanding voting
stock or voting interests of which is at the time owned or controlled, directly
or indirectly, by the Company or by one or more of such Subsidiary entities or
both.

         TECHNOLOGY - Section 3.16.

         This Agreement shall be governed by, and construed and enforced in
accordance with, the laws of the State of Delaware.

         The representations, warranties, covenants and agreements made herein
shall survive any investigation made by any Purchaser and shall survive the
Closing for the periods set forth in this Section 11.2. The covenants and
agreements made herein and all claims and causes of actions with respect thereto
shall survive forever. The representations and warranties made herein and all
claims and causes of action with respect thereto shall terminate upon the
earlier to occur of (a) the three (3) year anniversary of the Closing Date and
(b) the one (1) year anniversary of the date the Company completes a Qualified
Public Offering; provided that the representations and warranties of the Company
set forth in Section 3.1 (Organization and Standing; Articles and By-Laws),
Section 3.2 (Corporate Power), Section 3.4 (Capitalization), Section 3.5
(Authorization), Section 3.18 (Offering), 3.19 (Compliance with other
Instruments), Section 3.27 (Registration Rights) and Section 11.8 and the
representations and warranties of each Purchaser set forth in Section 4.1 shall
survive forever; it being understood that in the event notice of any claim for
breach of any representation or warranty shall have been given within the
applicable survival period, the representations and warranties that are the
subject of such claim shall survive until the time as such claim is finally
resolved.

         Except as otherwise expressly provided herein, the provisions hereof
shall inure to the benefit of, and be binding upon, the successors, assigns,
heirs, executors and administrators of the parties hereto; provided, however,
that the Company may not assign its rights hereunder. Without limiting the
generality of the foregoing, all representations, covenants and agreements

                                       45
<PAGE>   46

benefitting the Purchasers shall inure to the benefit of any and all subsequent
holders from time to time of the Shares or the Conversion Shares.

         This Agreement (including the Schedules and Exhibits hereto, which are
an integral part of this Agreement) and the other documents delivered pursuant
hereto constitute the full and entire understanding and agreement between the
parties with regard to the subjects hereof and thereof. Except as otherwise
expressly provided herein, neither this Agreement nor any term hereof may be
amended, waived, discharged or terminated, except by a written instrument signed
by the Company and the holders of greater than fifty percent (50%) of the
Conversion Shares which have not been sold to the public, but in no event shall
this paragraph be amended without the approval of the holders of at least
seventy-five percent (75%) of such Conversion Shares, nor shall any other
provision of this Agreement that specifies a requirement for a consent, vote or
approval of the Purchasers or of the holders of Shares or Conversion Shares be
amended without the approval of the percentage of Purchasers or holders
specified in such provision, or the obligation of any Purchaser hereunder
increased except upon the written consent of such Purchaser.

                  (a) All notices and other communications required or permitted
         hereunder shall be in writing and shall be mailed by first-class,
         registered or certified mail, postage prepaid, or delivered either by
         hand or by messenger, or sent via telex, telecopier, computer mail or
         other electronic means, addressed (a) if to a Purchaser, at the address
         shown on the Schedule of Purchasers, or at such other address as such
         Purchaser shall have furnished to the Company in writing, or (b) if to
         any other holder of any Shares or any Conversion Shares at such address
         as such holder shall have furnished to the Company in writing, or,
         until any such holder so furnishes an address to the Company, then to
         and at the address of the last holder thereof who has so furnished an
         address to the Company, or (c) if to the Company, 635 William Pitt Way,
         Pittsburgh, Pennsylvania 15328, Attn: President or at such other
         address as the Company shall have furnished to the Purchasers and each
         such other holder in writing.

                  (b) Any notice or other communications so addressed and
         mailed, postage prepaid, by registered or certified mail (in each case,
         with return receipt requested) shall be deemed to be given when so
         mailed. Any notice so addressed and otherwise delivered shall be deemed
         to be given when actually received by the addressee.

         No delay or omission to exercise any right, power or remedy accruing to
any of the parties hereto, upon any breach or default of any of the other
parties hereto under this Agreement, shall impair any such right, power or
remedy of such party nor shall it be construed to be a waiver of any such breach
or default, or an acquiescence therein, or of or in any similar breach or
default thereafter occurring; nor shall any waiver of any single breach or
default be deemed a waiver of any other breach or default theretofore or
thereafter occurring. Any waiver, permit, consent or approval of any kind or
character on the part of any party hereto of any breach or default under this
Agreement, or any waiver on the part of any party hereto of any provisions or
conditions of this Agreement must be made in writing and shall be effective only
to the extent specifically set forth in such writing. All remedies, either under
this Agreement or by law or otherwise afforded to any party hereto, shall be
cumulative and not alternative.

                                       46
<PAGE>   47

         In case any provision of this Agreement shall be invalid, illegal or
unenforceable, the validity, legality and enforceability of the remaining
provisions shall not in any way be affected or impaired thereby.

                  (a) The Company represents and warrants that it has retained
         no finder or broker or other person or firm in connection with the
         transactions contemplated by this Agreement. The Company accepts sole
         responsibility for and agrees to pay all agent's fees to any broker,
         finder or other person or firm in connection with the transactions
         contemplated herein, other than those which a Purchaser has agreed to
         pay pursuant to Section 11.8(b). In addition, the Company hereby agrees
         to indemnify and to hold the Purchasers harmless of and from any
         liability for any commission or compensation in the nature of an
         agent's fee to any broker, finder or other person or firm (and the
         costs and expenses of defending against such liability or asserted
         liability) arising from any act by the Company or any of its employees
         or representatives.

                  (b) Each Purchaser represents and warrants as to itself only
         that it has retained no finder or broker in connection with the
         transactions contemplated by this Agreement. Each Purchaser accepts
         sole responsibility for and agrees to pay all agent's fees to any
         broker, finder or other person or firm hired by such Purchaser in
         connection with the transactions contemplated herein, other than those
         which the Company has agreed to pay pursuant to Section 11.8(a). In
         addition, each Purchaser hereby agrees to indemnify and to hold the
         Company harmless of and from any liability for any commission or
         compensation in the nature of an agent's fee to any broker, finder or
         other person or firm (and the costs and expenses of defending against
         such liability or asserted liability) arising from any act by such
         Purchaser or any of its employees or representatives, other than those
         which the Company has agreed to pay pursuant to Section 11.8(a).

         The Company shall bear its own expenses and legal fees incurred on its
behalf with respect to this Agreement and the transactions contemplated hereby.
On the Closing Date (or if no closing shall take place, within thirty (30) days
of receiving any statement or invoice therefor), the Company will pay the
reasonable legal fees and out-of-pocket expenses of Kirkland & Ellis, special
counsel to the Purchasers, up to an aggregate of $40,000 with respect to this
Agreement and the transactions contemplated hereby.

         The titles of the Sections and subsections of this Agreement are for
convenience or reference only and are not to be considered in construing this
Agreement.

         This Agreement may be executed in counterparts, each of which when so
executed and delivered shall constitute a complete and original instrument but
all of which together shall constitute one and the same agreement, and it shall
not be necessary when making proof of this Agreement or any counterpart thereof
to account for any other counterpart.

                     [The remainder of this page is intentionally left blank;
signature page follows.]

                                       47
<PAGE>   48

         IN WITNESS WHEREOF, the parties have caused this Agreement to be duly
executed and delivered by their proper and duly authorized officers as of the
day and year first written above.

                                     CELLOMICS, INC.

                                     By:__________________________________
                                     Name:________________________________
                                     Title:_______________________________


                                     AXIOM VENTURE PARTNERS II
                                     LIMITED PARTNERSHIP

                                     By:__________________________________
                                        Axiom Venture Associates II Limited
                                        Liability Company, its General Partner

                                     By:__________________________________
                                        A General Partner


                                     HAROLD N. CHEFITZ

                                     _____________________________________

                                     DELPHI VENTURES III, L.P.

                                     By: Delphi Management Partners III, L.L.C.,
                                         General Partner

                                     By:__________________________________
                                        Managing Member

                                       48
<PAGE>   49
                                     DELPHI BIOINVESTMENTS III, L.P.

                                     By: Delphi Management Partners III, L.L.C.,
                                         General Partner

                                     By:__________________________________
                                        Managing Member

                                     INTERWEST INVESTORS VI, L.P.

                                     By: InterWest Management Partners VI, LLC


                                     By:__________________________________
                                     Name:________________________________
                                     Title:_______________________________


                                     INTERWEST PARTNERS VI, LP

                                     By: InterWest Management Partners VI, LLC


                                     By:__________________________________
                                     Name:________________________________
                                     Title:_______________________________


                                     KOMASTA PROPERTIES, LTD.


                                     By:__________________________________
                                     Name:________________________________
                                     Title:_______________________________



                                     OXFORD BIOSCIENCE PARTNERS II L.P.

                                     By: OBP Management II L.P.
                                         Its General Partner


                                     By:__________________________________
                                        Alan G. Walton - General Partner

                                       49
<PAGE>   50


                                     OXFORD BIOSCIENCE PARTNERS
                                     (BERMUDA) II LIMITED PARTNERSHIP

                                     By: OBP Management (Bermuda) II Limited
                                         Partnership

                                     By:__________________________________
                                        Alan G. Walton - General Partner


                                     OXFORD BIOSCIENCE PARTNERS
                                     (GS-ADJUNCT) II, L.P.

                                     By: OBP Management II L.P.


                                     By:__________________________________
                                        Alan G. Walton - General Partner


                                     VECTOR LATER-STAGE EQUITY FUND II
                                     (QP), L.P.

                                     By: Vector Fund Management II, L.L.C.
                                         Its General Partner


                                     By:__________________________________
                                        Its Managing Director

                                     VECTOR LATER-STAGE EQUITY FUND II, L.P.

                                     By: Vector Fund Management II, L.L.C.
                                         Its General Partner


                                     By:__________________________________
                                        Its Managing Director

                                       50
<PAGE>   51

                                    EXHIBIT A
                             SCHEDULE OF PURCHASERS

<TABLE>
<CAPTION>
                 NAME AND ADDRESS                              TOTAL                        SERIES B
                 ----------------                           INVESTMENT                 PREFERRED SHARES
                                                            ----------                 ----------------
<S>                                                       <C>                          <C>
Axiom Venture Partners II Limited Partnership             $812,805.92(1)                    67,341
CityPlace II - 17th Floor
Hartford, CT  06103
Harold N. Chefitz                                          $29,812.90(2)                     2,470
Boles Knop & Company
The Windsor House
Two West Washington Street
Middleburg, VA 20118
InterWest Partners VI, LP                                 $1,283,789.42(3)                  106,362
3000 Sand Hill Road
Bldg 3, Suite 255
Menlo Park, CA  94025-7112
InterWest Investors VI, LP                                 $40,241.33(4)                     3,334
3000 Sand Hill Road
Bldg 3, Suite 255
Menlo Park, CA  94025-7112
Delphi Ventures III, L.P.                                  $694,471.57(5)                    57,537
3000 Sand Hill Road
Bldg 1, Suite 135
Menlo Park, CA  94025
Delphi BioInvestments III, L.P.                            $12,492.44(6)                     1,035
300 Sand Hill Road
Bldg 1, Suite 135
Menlo Park, CA  94025
Komasta Properties, Ltd.                                   $501,049.84(7)                    41,512
111 Alozorov Street
Tel Aviv, Israel
Oxford Bioscience II, L.P.                                 $402,063.76(8)                    33,311
315 Post Rd West, Suite 2
Westport, CT  06880-4739
Oxford Bioscience Partners (Bermuda) II Limited            $301,303.38(9)                    24,963
Partnership
315 Post Rd West, Suite 2
Westport, CT  06880-4739
Oxford Bioscience Partners (GS-Adjunct) II, L.P.          $394,628.64(10)                    32,695
315 Post Rd West, Suite 2
Westport, CT 06880-4739
Vector Later-Stage Equity Fund II (QP), L.P.             $2,924,995.50(11)                  242,336
c/o Vector Fund Management, L.P.
1751 Lake Cook Road
Deerfield, IL 60015
Vector Later-Stage Equity Fund II, L.P.                   $975,002.55(12)                    80,779
c/o Vector Fund Management, L.P.
1751 Lake Cook Road
Deerfield, IL 60015

TOTALS                                                     $8,372,657.25                    693,675
</TABLE>

----------------------
Notes:

(1)      $562,800.01 conversion of Bridge Note and $250,005.91 in cash.
(2)      All in cash.
(3)      $744,127.65 by conversion of Bridge Note and $539,661.77 in cash.
(4)      $23,319.19 by conversion of Bridge Note and $16,922.14 in cash.
(5)      $301,544.79 by conversion of Bridge Note and $392,926.78 in cash.
(6)      $5,419.42 by conversion of Bridge Note and $7,073.02 in cash.
(7)      All in cash.
(8)      $74,918.48 by conversion of Bridge Note and $327,145.28 in cash.
(9)      $56,137.54 by conversion of Bridge Note and $245,165.84 in cash.
(10)     $73,530.43 by conversion of Bridge Note and $321,098.21 in cash.
(11)     All in cash.
(12)     All in cash.

                                       51