Exhibit 10.2


             SERIES B CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT


         THIS SERIES B CONVERTIBLE PREFERRED STOCK PURCHASE AGREEMENT, dated 
this 5th day of May, 1997, is entered into by and between NOVALON 
PHARMACEUTICAL CORPORATION, a Delaware corporation (the "Corporation"), and 
CUBIST PHARMACEUTICALS, INC. (the "Investor").

         WHEREAS, the Corporation desires to issue and sell to the Investor, 
and the Investor desires to purchase from the Corporation, shares of the 
Series B Convertible Preferred Stock, $.001 par value per share, of the 
Corporation, upon the terms and subject to the conditions set forth herein.

         NOW, THEREFORE, in consideration of the mutual covenants and 
agreements herein contained, the parties hereto, intending to be legally 
bound, hereby agree as follows.

         SECTION 1. DEFINITIONS. The following terms as used herein shall 
have the meanings set forth below in this Section 1 or shall have the 
meanings ascribed thereto elsewhere in this Agreement as referred to below in 
this Section 1:

                  "Acquisition" shall have the meaning ascribed to such term in
         the Acquisition Option Agreement.

                  "Acquisition Option Agreement" shall mean that certain
         Acquisition Option Agreement, in substantially the form of Exhibit A
         hereto, among the Corporation, the Novalon Stockholders (as defined
         therein) and the Investor.

                  "Acquisition Option" shall have the meaning ascribed to such
         term in the Acquisition Option Agreement.

                  "Acquisition Option Period" shall have the meaning ascribed to
         such term in the Acquisition Option Agreement.

                  "Affiliate" shall mean, with regard to any Person, any other
         Person or entity that directly or indirectly controls, or is controlled
         by, or is under common control with, such Person.

                  "Agreement" and "this Agreement" shall mean this Series B
         Convertible Preferred Stock Purchase Agreement, dated May 5, 1997, by
         and among the Corporation and the Investor, as amended from time to
         time.





                  "Benefit Plan" shall mean any plan, fund, program, policy,
         arrangement or contract, whether formal or informal, which is in the
         nature of (i) an employee pension benefit plan (as defined in Section
         3(2) of ERISA) or (ii) an employee welfare benefit plan (as defined in
         Section 3(l) of ERISA).

                  "Closing" shall have the meaning provided therefor in Section 
         3 hereof.

                  "Closing Date" shall have the meaning provided therefor in
         Section 3 hereof.

                  "Code" shall mean the Internal Revenue Code of 1986, as
         amended.

                  "Common Stock" shall mean the Common Stock, $.001 par value
         per share, of the Corporation.

                  "Environmental Laws" shall mean any Federal, state or local
         law or ordinance or regulation pertaining to the protection of human
         health, safety or the environment, including, without limitation, the
         Occupational Safety and Health Act, 29 U.S.C. Sections 651 et seq., the
         Comprehensive Environmental Response, Compensation and Liability Act,
         42 U.S.C. Sections 9601, et seq., the Emergency Planning and Community
         Right-to-Know Act, 42 U.S.C. Sections 11001, et seq., and the Resource
         Conservation and Recovery Act, 42 U.S.C. Sections 6901, et seq.

                  "ERISA" shall mean the Employee Retirement Income Security Act
         of 1974, as amended.

                  "Hazardous Substances" shall include medical waste, biological
         waste, oil and petroleum products, asbestos, polychlorinated biphenyls,
         urea formaldehyde and any other materials classified as pollutants or
         contaminants or as hazardous or toxic or as a biohazard under any
         Environmental Laws.

                  "Investors' Rights Agreement" shall mean that certain
         Investors' Rights Agreement, in substantially the form of Exhibit B
         hereto, among the Corporation and the Investors (as defined therein).

                  "Management Stock Restriction Agreement" shall mean that
         certain Stock Restriction Agreement, in substantially the form of
         Exhibit C hereto, among the Corporation, the Management 

                                       2




         Stockholders (as defined therein), the Management Stockholder
         Transferees (as defined therein) and the Investors (as defined
         therein).

                  "Person" shall mean an individual, partnership, corporation,
         association, limited liability company, trust, joint venture,
         unincorporated organization, and any government, governmental
         department or agency or political subdivision thereof.

                  "Registration Rights Agreement" shall mean that certain
         Registration Rights Agreement, in substantially the form of Exhibit D
         hereto, among the Corporation and the Investors (as defined therein).

                  "Related Documents" shall mean, collectively, this Agreement,
         the Investors' Rights Agreement, the Management Stock Restriction
         Agreement, the Registration Rights Agreement, the Restated Certificate
         of Incorporation and the Acquisition Option Agreement.

                  "Restated Certificate of Incorporation" shall mean the
         Restated Certificate of Incorporation filed with the Secretary of State
         of Delaware on May 2, 1997, a copy of which is attached hereto as of
         Exhibit E, as amended and in effect from time to time.

                  "Returns" shall mean, collectively, all returns, declarations,
         reports, statements and other documents required to be filed in respect
         of Taxes.

                  "Securities Act"  shall mean the Securities Act of 1933, as 
         amended.

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

                  "Series B Preferred Stock" shall mean the Series B Convertible
         Preferred Stock, $.001 par value per share, of the Corporation.

                  "Subsidiaries" shall mean, collectively, all corporations,
         partnerships, limited liability companies or other Persons with respect
         to which the Corporation shall own, directly or indirectly, more that
         fifty percent (50%) of the issued and outstanding equity interests of
         such corporations, partnerships, limited liability companies or other
         Persons.

                                       3




                  "Taxes" shall mean all federal, state, local, foreign and
         other net income, gross income, gross receipts, sales, use, ad valorem,
         transfer, franchise, profits, license, lease, service, service use,
         withholding, payroll, employment, excise, severance, stamp, occupation,
         premium, property, windfall profits, customs duties, or other taxes,
         fees, assessments or other charges of any kind whatever, together with
         any interest and any penalties, additions to tax or additional amounts
         with respect thereto.

         SECTION 2.  THE SERIES B CONVERTIBLE PREFERRED STOCK.

         2.1. Series B Convertible Preferred Stock. Prior to the Closing 
Date, the Corporation will have duly authorized the issuance and sale to the 
Investor, at the Closing, of an aggregate of 333,333 shares (the "Series B 
Shares") of the Series B Preferred Stock, at a purchase price per share of 
$3.00. The Series B Shares shall have the powers, preferences, rights and 
other terms and conditions applicable to shares of Series B Preferred Stock, 
as set forth in Article IV of the Restated Certificate of Incorporation.

         2.2. Conversion Shares. Prior to the Closing Date, the Corporation 
will have duly authorized and reserved, and covenants to continue to reserve, 
free of preemptive rights and other preferential rights, a sufficient number 
of its authorized but unissued shares of Common Stock to satisfy the 
obligation of the Corporation to issue shares of Common Stock upon conversion 
of all Series B Shares. For purposes of this Agreement, any shares of Common 
Stock issuable upon conversion of the Series B Shares, and such shares when 
issued, are sometimes herein referred to as the "Conversion Shares".

         SECTION 3. SALE AND PURCHASE OF STOCK. The Corporation shall issue 
and sell to the Investor, and, subject to compliance with all of the terms 
and conditions hereof and in reliance on the representations, warranties and 
covenants set forth or referred to herein, the Investor shall purchase from 
the Corporation, the Series B Shares for the aggregate purchase price of 
$999,999. (the "Series B Purchase Price"). The closing of the sale and 
purchase of the Series B Shares (the "Closing") will occur on May 5, 1997 and 
will take place by facsimile transmission of executed copies of the documents 
contemplated hereby to the offices of Bingham, Dana & Gould LLP, 150 Federal 
Street, Boston, Massachusetts, at 10:00 a.m., local time, or at such other 
time as may be mutually agreed upon by the Investor and the Corporation. The 
date of the Closing is herein called the "Closing Date". At the Closing, the 
Corporation shall, unless otherwise requested, deliver to the Investor a 
single certificate evidencing the Series B Shares, against payment of the 
aggregate purchase price therefor by bank or certified check or wire transfer 
of immediately available funds to such account or accounts as the Corporation 
shall designate in writing.

                                       4




         SECTION 4. REPRESENTATIONS AND WARRANTIES OF THE CORPORATION. The 
Corporation represents and warrants to the Investor that, except as set forth 
in the Disclosure Schedule attached hereto as Schedule 4 (which Disclosure 
Schedule makes explicit reference to the particular representation or 
warranty as to which exception is taken, which in each case shall constitute 
the sole representation and warranty as to which such exception shall apply):

         4.1.     Organization, Qualifications and Corporate Power.

                  (a) The Corporation is a corporation duly incorporated, 
validly existing and in good standing under the laws of the State of Delaware 
and is duly licensed or qualified to transact business as a foreign 
corporation and is in good standing in each jurisdiction in which the nature 
of the business transacted by it or the character of the properties owned or 
leased by it requires such licensing or qualification. The Corporation has 
the corporate power and authority to own and hold its properties and to carry 
on its business as now conducted and as proposed to be conducted, to execute, 
deliver and perform this Agreement and each of the other Related Documents, 
to issue, sell and deliver the Series B Shares, and to issue and deliver the 
Conversion Shares upon conversion of the Series B Shares.

                  (b) The attached Schedule 4.1(b) contains a list of all 
Subsidiaries of the Corporation. The Corporation does not (i) own of record 
or beneficially, directly or indirectly, (A) any shares of capital stock or 
securities convertible into capital stock of any other corporation or (B) any 
participating interest in any partnership, joint venture or other 
non-corporate business enterprise or (ii) control, directly or indirectly, 
any other entity.

         4.2.     Authorization of Agreements, Etc.

                  (a) The execution and delivery by the Corporation of this 
Agreement and each of the other Related Documents, the performance by the 
Corporation of its obligations hereunder and thereunder, the issuance, sale 
and delivery of the Series B Shares and the issuance and delivery of the 
Conversion Shares have been duly authorized by all requisite corporate action 
and will not violate any provision of law, any order of any court or other 
agency of government, the Restated Certificate of Incorporation or the 
By-laws of the Corporation, as amended, or any provision of any indenture, 
agreement or other instrument to which the Corporation or any of its 
properties or assets is bound, or conflict with, result in a breach of or 
constitute (with due notice or lapse of time or both) a default under any 
such indenture, agreement or other instrument, or result in the creation or 
imposition of any lien, charge, restriction, claim or encumbrance of any 
nature whatsoever upon any of the properties or assets of the Corporation.

                                       5




                  (b) The Series B Shares have been duly authorized and, when 
issued in accordance with this Agreement, will be validly issued, fully paid 
and nonassessable shares of Series B Preferred Stock with no personal 
liability attaching to the ownership thereof and will be free and clear of 
all liens, charges, restrictions, claims and encumbrances imposed by or 
through the Corporation except as set forth in any of the other Related 
Documents. The Conversion Shares have been duly reserved for issuance upon 
conversion of the Series B Shares and, when so issued, will be duly 
authorized, validly issued, fully paid and nonassessable shares of Common 
Stock with no personal liability attaching to the ownership thereof and will 
be free and clear of all liens, charges, restrictions, claims and 
encumbrances imposed by or through the Corporation except as set forth in any 
of the other Related Documents. None of the issuance, sale or delivery of the 
Series B Shares or the issuance or delivery of the Conversion Shares is 
subject to any preemptive right of stockholders of the Corporation or to any 
right of first refusal or other right in favor of any Person.

         4.3. Validity. This Agreement has been duly executed and delivered 
by the Corporation and constitutes the legal, valid and binding obligation of 
the Corporation, enforceable in accordance with its terms. Each of the other 
Related Documents, when executed and delivered or filed, as the case may be, 
in accordance with this Agreement, will constitute the legal, valid and 
binding obligations of the Corporation, enforceable in accordance with their 
respective terms.

         4.4. Authorized Capital Stock. The authorized capital stock of the 
Corporation consists of (i) 700,000 shares of Preferred Stock, $.001 par 
value (the "Preferred Stock"), of which 200,000 have been designated as 
shares of Series A Preferred Stock and 500,000 have been designated as shares 
of Series B Preferred Stock, and (ii) 11,000,000 shares of Common Stock. 
Immediately prior to the Closing, 200,000 shares of Series A Preferred Stock 
and 2,140,000 shares of Common Stock will be validly issued and outstanding, 
fully paid and nonassessable with no personal liability attaching to the 
ownership thereof. The stockholders of record and holders of subscriptions, 
warrants, options, convertible securities, and other rights (contingent or 
other) to purchase or otherwise acquire equity securities of the Corporation, 
and the number of shares of Series A Preferred Stock or of Common Stock and 
the number of such subscriptions, warrants, options, convertible securities, 
and other such rights held by each, are as set forth in the attached Schedule 
4.4. The designations, powers, preferences, rights, qualifications, 
limitations and restrictions in respect of each class and series of 
authorized capital stock of the Corporation are as set forth in the 

                                       6




Restated Certificate of Incorporation, and all such designations, powers, 
preferences, rights, qualifications, limitations and restrictions are valid, 
binding and enforceable and in accordance with all applicable laws. As of the 
date hereof, each outstanding share of Series A Preferred Stock is 
convertible into one share of Common Stock. Except as provided for in the 
Restated Certificate of Incorporation or as set forth in the attached 
Schedule 4.4, (i) no Person owns of record or is known to the Corporation to 
own beneficially any share of capital stock of the Corporation, (ii) no 
subscription, warrant, option, convertible security, or other right 
(contingent or other) to purchase or otherwise acquire equity securities of 
the Corporation is authorized or outstanding and (iii) there is no commitment 
by the Corporation to issue shares, subscriptions, warrants, options, 
convertible securities, or other such rights or to distribute to holders of 
any of its equity securities any evidence of indebtedness or asset. Except as 
provided for in the Restated Certificate of Incorporation or as set forth in 
the attached Schedule 4.4, the Corporation has no obligation (contingent or 
other) to purchase, redeem or otherwise acquire any of its equity securities 
or any interest therein or to pay any dividend or make any other distribution 
in respect thereof. Except as set forth in any of the Related Documents, to 
the best of the Corporation's knowledge, there are no voting trusts or 
agreements, stockholders' agreements, pledge agreements, buy-sell agreements, 
rights of first refusal, preemptive rights or proxies relating to any 
securities of the Corporation (whether or not the Corporation is a party 
thereto). All of the outstanding securities of the Corporation were issued in 
compliance with all applicable Federal and state securities laws.

         4.5. Financial Statements, Etc. The Corporation has furnished to the 
Investor the audited balance sheet of the Corporation as of December 31, 1996 
and the related audited statements of income, stockholders equity and cash 
flows of the Corporation for the year ended December 31, 1996, and the 
unaudited balance sheet of the Corporation as of March 31, 1997 (the "Balance 
Sheet") and the related unaudited statements of income, stockholders' equity 
and cash flows of the Corporation for the three months ended March 31, 1997. 
All such financial statements have been prepared in accordance with generally 
accepted accounting principles consistently applied (except that such 
unaudited financial statements do not contain all of the required footnotes) 
and fairly present the financial position of the Corporation as of December 
31, 1996 and March 31, 1997, respectively, and the results of their 
operations and cash flows for the year ended December 31, 1996 and the three 
months ended March 31, 1997, respectively. Since the date of the Balance 
Sheet, (i) there has been no change in the assets, liabilities or financial 
condition of the Corporation from that reflected in the Balance Sheet except 
for changes in the ordinary course of business which in the aggregate have 
not been materially adverse and (ii) none of the business, prospects, 
financial condition, operations, property or affairs of the Corporation has 
been materially adversely affected by any occurrence or development, 
individually or in the aggregate, whether or not insured against.

         4.6. Events Subsequent to the Date of the Balance Sheet. Since the 
date of the Balance Sheet, the Corporation has not (i) issued any stock, bond 
or other corporate security except as otherwise contemplated hereby, (ii) 
borrowed any amount or incurred or become subject to any liability (absolute, 
accrued or

                                       7




contingent), except current liabilities incurred and liabilities under 
contracts entered into in the ordinary course of business, (iii) discharged 
or satisfied any lien or encumbrance or incurred or paid any obligation or 
liability (absolute, accrued or contingent) other than current liabilities 
shown on the Balance Sheet and current liabilities incurred since the date of 
the Balance Sheet in the ordinary course of business, (iv) declared or made 
any payment or distribution to stockholders or purchased or redeemed any 
share of its capital stock or other security, (v) mortgaged, pledged, 
encumbered or subjected to lien any of its assets, tangible or intangible, 
other than liens of current real property taxes not yet due and payable, (vi) 
sold, assigned or transferred any of its tangible assets except in the 
ordinary course of business, or canceled any debt or claim, (vii) sold, 
assigned, transferred or granted any exclusive license with respect to any 
patent, trademark, trade name, service mark, copyright, trade secret or other 
intangible asset, (viii) suffered any loss of property or waived any right of 
substantial value whether or not in the ordinary course of business, (ix) 
made any change in officer compensation except in the ordinary course of 
business and consistent with past practice, (x) made any material change in 
the manner of business or operations of the Corporation, (xi) entered into 
any transaction except in the ordinary course of business or as otherwise 
contemplated hereby or (xii) entered into any commitment (contingent or 
otherwise) to do any of the foregoing.

         4.7. Litigation; Compliance with Law. There is no (i) action, suit, 
claim, proceeding or investigation pending or, to the best of the 
Corporation's knowledge, threatened against or affecting the Corporation, at 
law or in equity, or before or by any Federal, state, municipal or other 
governmental department, commission, board, bureau, agency or 
instrumentality, domestic or foreign, (ii) arbitration proceeding relating to 
the Corporation pending under collective bargaining agreements or otherwise 
or (iii) governmental inquiry pending or, to the best of the Corporation's 
knowledge, threatened against or affecting the Corporation (including, 
without limitation, any inquiry as to the qualification of the Corporation to 
hold or receive any license, permit, or other authorization), and there is no 
basis for any of the foregoing. The Corporation has not received any opinion 
or memorandum or legal advice from legal counsel to the effect that it is 
exposed, from a legal standpoint, to any liability or disadvantage which may 
be material to its business, prospects, financial condition, operations, 
property or affairs. The Corporation is not in default with respect to any 
order, writ, injunction or decree known to or served upon the Corporation of 
any court or of any Federal, state, municipal or other governmental 
department, commission, board, bureau, agency or instrumentality, domestic or 
foreign. There is no action or suit by the Corporation pending or threatened 
against others. The Corporation has complied with all laws, rules, 
regulations and orders applicable to its business, operations, properties, 
assets, products and services, the Corporation has all necessary permits, 
licenses and other authorizations required to conduct its business as 
conducted and as proposed to be conducted, and the Corporation has been 
operating its business 

                                       8




pursuant to and in compliance with the terms of all such permits, licenses 
and other authorizations. There is no existing law, rule, regulation or 
order, and the Corporation after due inquiry is not aware of any proposed 
law, rule, regulation or order, whether Federal, state, county or local, 
which would prohibit or restrict the Corporation from, or otherwise 
materially adversely affect the Corporation in, conducting its business in 
any jurisdiction in which it is now conducting business or in which it 
proposes to conduct business.

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

         4.9. Patents, Trademarks Etc. Set forth in Schedule 4.9 attached 
hereto is a list and brief description of all domestic and foreign patents, 
patent rights, patent applications, trademarks, trademark applications, 
service marks, service mark applications, trade names and copyrights, and all 
applications for such which are in the process of being prepared, owned by or 
registered in the name of the Corporation, or of which the Corporation is a 
licensor or licensee or in which the Corporation has any right, and in each 
case a brief description of the nature of such right. The Corporation owns or 
possesses adequate licenses or other rights to use all patents, patent 
applications, trademarks, trademark applications, service 

                                       9




marks, service mark applications, trade names, copyrights, manufacturing 
processes, formulae, trade secrets, customer lists and know how 
(collectively, "Intellectual Property") necessary to the conduct of its 
business as conducted and as proposed to be conducted, and no claim is 
pending or, to the best of the Corporation's knowledge, threatened to the 
effect that the operations of the Corporation infringe upon or conflict with 
the asserted rights of any other Person under any Intellectual Property, and 
there is no basis for any such claim (whether or not pending or threatened). 
No claim is pending or threatened to the effect that any such Intellectual 
Property owned or licensed by the Corporation, or which the Corporation 
otherwise has the right to use, is invalid or unenforceable by the 
Corporation, and there is no basis for any such claim (whether or not pending 
or threatened). To the best of the Corporation's knowledge, all technical 
information developed by and belonging to the Corporation which has not been 
patented has been kept confidential. The Corporation has not granted or 
assigned to any other Person or entity any right to manufacture, have 
manufactured, assemble or sell the products or proposed products or to 
provide the services or proposed services of the Corporation.

         4.10. Title to Properties. The Corporation has good, clear and 
marketable title to all of its properties and assets, including, without 
limitation, those reflected on the Balance Sheet or acquired by it since the 
date of the Balance Sheet (other than properties and assets disposed of in 
the ordinary course of business since the date of the Balance Sheet), and all 
of the Corporation's properties and assets are free and clear of mortgages, 
pledges, security interests, liens, charges, claims, restrictions and other 
encumbrances (including, without limitation, easements and licenses), except 
for liens for or current taxes not yet due and payable and minor 
imperfections of title, if any, not material in nature or amount and not 
materially detracting from the value or impairing the use of the property 
subject thereto or impairing the operations or proposed operations of the 
Corporation, including without limitation, the ability of the Corporation to 
secure financing using such properties and assets as collateral. To the best 
of the Corporation's knowledge after due inquiry, there are no condemnation, 
environmental, zoning or other land use regulation proceedings, either 
instituted or planned to be instituted, which would adversely affect the use 
or operation of the Corporation's properties and assets for their respective 
intended uses and purposes, or the value of such properties, and the 
Corporation has not received notice of any special assessment proceedings 
which would affect such properties and assets.

         4.11. Leasehold Interests. Each lease or agreement to which the 
Corporation is a party under which it is a lessee of any property, real or 
personal, is a valid and subsisting agreement, duly authorized and entered 
into, without any default of the Corporation thereunder and, to the best of 
the Corporation's knowledge, without any default thereunder of any other 
party thereto. No event has occurred and is continuing which, with due notice 
or lapse of time or both, 

                                       10




would constitute a default or event of default by the Corporation under any 
such lease or agreement or, to the best of the Corporation's knowledge, by 
any other party thereto. The Corporation's possession of such property has 
not been disturbed and, to the best of the Corporation's knowledge after due 
inquiry, no claim has been asserted against the Corporation adverse to its 
rights in such leasehold interests.

         4.12. Insurance. Schedule 4.12 hereto lists all policies of fire, 
liability, workmen's compensation, life, property and casualty and other 
insurance owned or held by the Corporation. Such policies of insurance are 
maintained with financially sound and reputable insurance companies, funds or 
underwriters and are of the kinds and cover such risks and are in such 
amounts and with such deductibles and exclusions as are consistent with 
prudent business practice. All such policies (a) are in full force and 
effect, (b) are sufficient for compliance by the Corporation with all 
requirements of law and all agreements to which the Corporation is a party 
and (c) provide that they will remain in full force and effect through the 
respective dates set forth in such Schedule. The Corporation is not in 
default with respect to its obligations under any of such insurance policies 
and has not received any notification of cancellation of any such insurance 
policies.

         4.13. Taxes. The Corporation has filed all Returns required to be 
filed by it and has paid all Taxes shown to be due by such Returns, as well 
as all other Taxes, assessments and governmental charges which have become 
due or payable, including without limitation, all Taxes which it is obligated 
to withhold for amounts owing to employees, creditors and third parties. All 
Taxes with respect to which the Corporation has become obligated pursuant to 
elections made by it in accordance with generally accepted practice have been 
paid and adequate reserves have been established for all Taxes accrued but 
not yet payable. No issues have been raised (and are currently pending) by 
any taxing authority in connection with any of the Returns. No waivers of 
statutes of limitation with respect to any of the Returns have been given by 
or requested from the Corporation. All deficiencies asserted or assessments 
made as a result of any examinations have been fully paid, or are fully 
reflected as a liability in the financial statements of the Corporation, or 
are being contested and an adequate reserve therefor has been established and 
is fully reflected in the financial statements of the Corporation. There are 
no liens for Taxes (other than for current Taxes not yet due and payable) 
upon the assets of the Corporation. All material elections with respect to 
Taxes affecting the Corporation, as of the date hereof, are set forth in the 
financial statements of the Corporation, or are annexed hereto in a 
disclosure schedule. The Corporation has not agreed to make, nor is it 
required to make, any adjustment under Section 481(a) of the Code by reason 
of a change in accounting method or otherwise. The Corporation is not a party 
to any agreement, contract, arrangement or plan that has resulted or would 
result, separately or in the aggregate, in the payment of any "excess 
parachute payments" within the meaning of Section 28OG of the Code. The 
Corporation does not have and has not had a permanent establishment in any 
foreign country, as 

                                       11

  


defined in any applicable tax treaty or convention between the United States 
of America and such foreign country. Notwithstanding anything to the contrary 
contained in this Agreement, the provisions of this Section 4.13 shall 
survive until the applicable statutes of limitations with respect to any 
Taxes contemplated hereby shall have expired.

         4.14. Other Agreements. Except as set forth in the attached Schedule 
4.14(a), the Corporation is not a party to or otherwise bound by any written 
or oral agreement, instrument, commitment or restriction which individually 
or in the aggregate could materially adversely affect the business, 
prospects, financial condition, operations, property or affairs of the 
Corporation. Except as set forth in the attached Schedule 4.14(b), the 
Corporation is not a party to or otherwise bound by any written or oral:

                  (a) distributor, dealer, manufacturer's representative or 
sales agency agreement which is not terminable on less than ninety (90) days, 
notice without cost or other liability to the Corporation (except for 
agreements which, in the aggregate, are not material to the business of the 
Corporation);

                  (b) sales or service agreement which entitles any customer 
to a rebate or right of set-off, to return any product to the Corporation 
after acceptance thereof or to delay the acceptance thereof, or which varies 
in any material respect from the Corporation's standard form agreements;

                  (c) agreement with any labor union (and, to the best of the 
Corporation's knowledge, no organizational effort is being made with respect 
to any of its employees);

                  (d) agreement with any supplier containing any provision 
permitting any party other than the Corporation to renegotiate the price or 
other terms, or containing any payback or other similar provision, upon the 
occurrence of a failure by the Corporation to meet its obligations under the 
agreement when due or the occurrence of any other event;

                  (e) agreement for the future purchase of fixed assets or 
for the future purchase of materials, supplies or equipment in excess of its 
normal operating requirements;

                  (f) agreement for the employment of any officer, employee 
or other individual (whether of a legally binding nature or in the nature of 
informal understandings) on a full-time or consulting basis which is not 
terminable on notice without cost or other liability to the Corporation, 
except normal severance arrangements and accrued vacation pay;

                                       12




                  (g) bonus, pension, profit-sharing, retirement, 
hospitalization, insurance, stock purchase, stock option or other plan, 
agreement or understanding pursuant to which benefits are provided to any 
employee of the Corporation (other than group insurance plans applicable to 
employees generally);

                  (h) agreement relating to the borrowing of money or to the 
mortgaging or pledging of, or otherwise placing a lien or security interest 
on, any asset of the Corporation;

                  (i) guaranty of any obligation for borrowed money or 
otherwise;

                  (j) voting trust or agreement, stockholders' agreement, 
pledge agreement, buy-sell agreement or first refusal or preemptive rights 
agreement relating to any securities of the Corporation;

                  (k) agreement, or group of related agreements with the same 
party or any group of affiliated parties, under which the Corporation has 
advanced or agreed to advance money or has agreed to lease any property as 
lessee or lessor;

                  (l) agreement or obligation (contingent or otherwise) to 
issue, sell or otherwise distribute or to repurchase or otherwise acquire or 
retire any share of its capital stock or any of its other equity securities;

                  (m) assignment, license or other agreement with respect to 
any form of intangible property;

                  (n) agreement under which it has granted any Person any 
registration rights, other than the Registration Rights Agreement;

                  (o) agreement under which it has limited or restricted its 
right to compete with any Person in any respect;

                  (p) other agreement or group of related agreements with the 
same party involving more than $10,000 or continuing over a period of more 
than six months from the date or dates thereof (including renewals or 
extensions optional with another party), which agreement or group of 
agreements is not terminable by the Corporation without penalty upon notice 
of thirty (30) days or less, but excluding any agreement or group of 
agreements with a customer of the Corporation for the sale, lease or rental 
of the Corporation's products or services if such agreement or group of 
agreements was entered into by the Corporation in the ordinary course of 
business; or

                  (q) other agreement, instrument, commitment, plan or 
arrangement, a copy of which would be required to be filed with the 
Securities and 

                                       13




Exchange Commission (the "Commission") as an exhibit to a registration 
statement on Form S-1 if the Corporation were registering securities under 
the Securities Act.

         The Corporation and, to the best of the Corporation's knowledge 
after due inquiry, each other party thereto have in all material respects 
performed all the obligations required to be performed by them to date (or 
each non-performing party has received a valid, enforceable and irrevocable 
written waiver with respect to its non-performance), have received no notice 
of default and are not in default (with due notice or lapse of time or both) 
under any agreement, instrument, commitment, plan or arrangement to which the 
Corporation is a party or by which it or its property may be bound. The 
Corporation has no present expectation or intention of not fully performing 
all its obligations under each such agreement, instrument, commitment, plan 
or arrangement, and the Corporation has no knowledge of any breach or 
anticipated breach by the other party to any agreement, instrument, 
commitment, plan or arrangement to which the Corporation is a party. The 
Corporation is in full compliance with all of the terms and provisions of its 
Restated Certificate of Incorporation and By-laws, as amended.

         4.15. Loans and Advances. The Corporation does not have any 
outstanding loans or advances to any Person and is not obligated to make any 
such loans or advances, except, in each case, for advances to employees of 
the Corporation in respect of reimbursable business expenses anticipated to 
be incurred by them in connection with their performance of services for the 
Corporation.

         4.16. Assumptions, Guaranties, Etc. of Indebtedness of Other 
Persons. The Corporation has not assumed, guaranteed, endorsed or otherwise 
become directly or contingently liable on any indebtedness of any other 
Person (including, without limitation, liability by way of agreement, 
contingent or otherwise, to purchase, to provide funds for payment, to supply 
funds to or otherwise invest in the debtor, or otherwise to assure the 
creditor against loss), except for guaranties by endorsement of negotiable 
instruments for deposit or collection in the ordinary course of business.

         4.17. Significant Customers and Suppliers. No customer or supplier 
which was significant to the Corporation during the period covered by the 
financial statements referred to in Section 4.5 hereof or which has been 
significant to the Corporation thereafter, has terminated, materially reduced 
or threatened to terminate or materially reduce its purchases from or 
provision of products or services to the Corporation, as the case may be.

         4.18. Governmental Approvals. Subject to the accuracy of the 
representations and warranties of the Investor set forth in Section 5 of this 
Agreement, no registration or filing with, or consent or approval of or other 
action by, any Federal, state or other governmental agency or instrumentality 
is or will be necessary for the valid execution, delivery and performance by 
the Corporation of 

                                       14




this Agreement or any of the other Related Documents, the issuance, sale and 
delivery of the Series B Shares or, upon conversion thereof, the issuance and 
delivery of the Conversion Shares, other than (i) filings pursuant to state 
securities laws (all of which filings have been made by the Corporation, 
other than those which are required to be made after the Closing and which 
will be duly made on a timely basis) in connection with the sale of the 
Series B Shares and (ii) with respect to the Registration Rights Agreement, 
the registration of the shares covered thereby with the Commission and 
filings pursuant to state securities laws.

         4.19. Issuance Taxes. There are no transfer, issuance or similar 
taxes imposed by law in connection with the issuance, sale or delivery of the 
Series B Shares or the Conversion Shares to the Investor.

         4.20. Offering of the Series B Shares. Neither the Corporation nor 
any Person acting on behalf of the Corporation has offered the Series B 
Shares or any security of the Corporation similar to the Series B Shares for 
sale to, or solicited any offer to buy the Series B Shares or any such 
similar security from, or otherwise approached or negotiated with respect 
thereto with, any Person or Persons, and neither the Corporation nor any 
Person acting on its behalf has taken or will take any other action 
(including, without limitation, any offer, issuance or sale of any security 
of the Corporation under circumstances which might require the integration of 
such security with the Series B Shares under the Securities Act or the rules 
and regulations of the Commission thereunder or under any applicable State 
securities laws), in either case so as to subject the offering, issuance or 
sale of the Series B Shares to the registration provisions of the Securities 
Act.

         4.21. Brokers. The Corporation has no contract, arrangement or 
understanding with any broker, finder or similar agent with respect to the 
transactions contemplated by this Agreement.

         4.22. Officers. Set forth in Schedule 4.22 attached hereto is a list 
of the names of the officers of the Corporation, together with the title or 
job classification of each such individual and the total compensation 
anticipated to be paid to each such individual by the Corporation in 1997. 
None of such individuals has an employment agreement or understanding, 
whether oral or written, with the Corporation, which is not terminable on 
notice by the Corporation without cost or other liability to the Corporation.

         4.23. Transactions With Affiliates. Except as set forth in Schedule 
4.23, no director, officer, employee or stockholder of the Corporation, or 
member of the family of any such Person, or any corporation, partnership, 
trust or other entity in which any such Person, or any member of the family 
of any such Person, has a substantial interest or is an officer, director, 
trustee, partner or holder of more than 5% of the outstanding capital stock 
thereof, is a party to any transaction with the 

                                       15




Corporation, including any contract, agreement or other arrangement providing 
for the employment of, furnishing of services by, rental of real or personal 
property from or otherwise requiring payments to any such Person or firm.

         4.24. Employees. Each of the officers of the Corporation, each key 
employee or consultant and each other employee or consultant now employed by, 
or consulting for, the Corporation who has access to confidential information 
of the Corporation has executed a written confidentiality and nondisclosure 
agreement, and all of such agreements are in full force and effect. The 
Corporation has provided the Investor with copies of all of such written 
confidentiality and nondisclosure agreements. No officer or key employee or 
consultant of the Corporation has advised the Corporation (orally or in 
writing) that he intends to terminate his or her employment or consultancy, 
as the case may be, with the Corporation. The Corporation has complied in all 
material respects with all applicable laws relating to the employment of 
labor, including provisions relating to wages, hours, equal opportunity, 
collective bargaining and the payment of Social Security and other taxes, and 
with ERISA.

         4.25. U.S. Real Property Holding Corporation. The Corporation is not 
now and has never been a "United States real property holding corporation", 
as defined in Section 897(c)(2) of the Code and Section 1.897-2(b) of the 
Regulations promulgated by the Internal Revenue Service, and the Corporation 
has filed with the Internal Revenue Service all statements, if any, with its 
United States income tax returns which are required under Section 1.897-2(h) 
of such Regulations.

         4.26. Environmental Protection. The Corporation has not caused or 
allowed, or contracted with any party for, the generation, use, 
transportation, treatment, storage or disposal of any Hazardous Substances in 
connection with the operation of its business or otherwise. The Corporation, 
the operation of its business, and any real property that the Corporation 
owns, leases or otherwise occupies or uses (the "Premises") are in compliance 
with all applicable Environmental Laws and orders or directives of any 
governmental authorities having jurisdiction under such Environmental Laws, 
including, without limitation, any Environmental Laws or orders or directives 
with respect to any cleanup or remediation of any release or threat of 
release of Hazardous Substances. The Corporation has not received any 
citation, directive, letter or other communication, written or oral, or any 
notice of any proceeding, claim or lawsuit, from any Person arising out of 
the ownership or occupation of the Premises, or the conduct of its 
operations, and the Corporation is not aware of any basis therefor. The 
Corporation has obtained and is maintaining in full force and effect all 
necessary permits, licenses and approvals required by all Environmental Laws 
applicable to the Premises and the business operations conducted thereon 
(including operations conducted by tenants on the Premises), and is in 
compliance with all such permits, licenses and approvals. The Corporation has 
not caused or allowed a release, or a threat of release, of any Hazardous 
Substance 

                                       16




onto, at or near the Premises, and, to the best of the Corporation's 
knowledge, neither the Premises nor any property at or near the Premises has 
ever been subject to a release, or a threat of release, of any Hazardous 
Substance.

         4.27. ERISA. Except as listed in Schedule 4.27, neither the 
Corporation nor any entity required to be aggregated with the Corporation 
under Sections 4.14(b), (c), (m) or (n) of the Code sponsors, maintains, has 
any obligation to contribute to, has any liability under, or is otherwise a 
party to, any Benefit Plan. With respect to each Benefit Plan listed in 
Schedule 4.27, to the extent applicable:

                  (a) Each such Benefit Plan has been maintained and operated 
in all material respects in compliance with its terms and with all applicable 
provisions of ERISA, the Code and all regulations, rulings and other 
authority issued thereunder;

                  (b) All contributions required by law to have been made 
under each such Benefit Plan (without regard to any waivers granted under 
Section 412 of the Code) to any fund or trust established thereunder or in 
connection therewith have been made by the due date thereof;

                  (c) Each such Benefit Plan intended to qualify under 
Section 401(a) of the Code is the subject of a favorable unrevoked 
determination letter issued by the Internal Revenue Service as to its 
qualified status under the Code, which determination letter may still be 
relied upon as to such tax qualified status, and no circumstances have 
occurred that would adversely affect the tax qualified status of any such 
Benefit Plan;

                  (d) The actuarial present value of all accrued benefits 
under each such Benefit Plan subject to Title IV of ERISA did not, as of the 
latest valuation date of such Benefit Plan, exceed the then current value of 
the assets of such Benefit Plan allocable to such accrued benefits, all as 
based upon the actuarial assumptions and methods currently used for such 
Benefit Plan;

                  (e) None of such Benefit Plans that are "employee welfare 
benefit plans" as defined in Section 3(l) of ERISA provides for continuing 
benefits or coverage for any participant or beneficiary of a participant 
after such participant's termination of employment; and

                  (f) Neither the Corporation nor any trade or business 
(whether or not incorporated) under common control with the Corporation 
within the meaning of Section 4001 of ERISA has, or at any time has had, any 
obligation to contribute to any "multiemployer plan" as defined in Section 
3(37) of ERISA.

                                       17




         4.28. Foreign Corrupt Practices Act. The Corporation has not taken 
any action which would cause it to be in violation of the Foreign Corrupt 
Practices Act of 1977, as amended, or any rules and regulations thereunder. 
To the best of the Corporation's knowledge after due inquiry, there is not 
now, and there has never been, any employment by the Corporation of, or 
beneficial ownership in the Corporation by, any governmental or political 
official in any country in the world.

         4.29. Federal Reserve Regulations. The Corporation is not engaged in 
the business of extending credit for the purpose of purchasing or carrying 
margin securities (within the meaning of Regulation G of the Board of 
Governors of the Federal Reserve System), and no part of the proceeds of the 
Series B Shares will be used to purchase or carry any margin security or to 
extend credit to others for the purpose of purchasing or carrying any margin 
security or in any other manner which would involve a violation of any of the 
regulations of the Board of Governors of the Federal Reserve System.

         4.30. Indemnification of Directors and Officers. The By-Laws, as in 
effect on the date hereof, provide for the indemnification of officers and 
directors to the full extent permitted by the General Corporation Law of 
Delaware.

         4.31. Disclosure. Neither this Agreement, nor any Schedule or 
Exhibit to this Agreement, nor any of the financial statements delivered 
pursuant to Section 4.5 of this Agreement, nor the Business Plan of the 
Corporation dated November 25, 1996 (the "Business Plan"), contains an untrue 
statement of a material fact or omits a material fact necessary to make the 
statements contained herein or therein not misleading. None of the 
statements, documents, certificates or other items prepared or supplied by 
the Corporation with respect to the transactions contemplated hereby contains 
an untrue statement of a material fact or omits a material fact necessary to 
make the statements contained therein not misleading. There is no fact which 
the Corporation has not disclosed to the Investor and its counsel in writing 
and of which the Corporation is aware which materially and adversely affects 
or could materially and adversely affect the business, prospects, financial 
condition, operations, property or affairs of the Corporation.

         SECTION 5.  REPRESENTATIONS  AND WARRANTIES OF THE INVESTOR.  The 
Investor  represents and warrants to the Corporation that:

         5.1.     Organization, Authority, Binding Effect.

                  (a) It has full power and authority to enter into and 
perform this Agreement and the other Related Documents to which it is a 
party, in accordance with their respective terms. It is duly organized, 
validly existing and in good standing under the laws of its jurisdiction of 
organization and has the power and 

                                       18




authority to enter into this Agreement and the other Related Documents to 
which it is a party.

                  (b) The execution, delivery and performance by it of this 
Agreement and the other Related Documents to which it is a party, and the 
consummation by it of the transactions contemplated hereby and thereby, have 
been duly authorized by all requisite action of it, and each such agreement 
or document constitutes the valid and binding obligation of the Investor, 
enforceable in accordance with its terms, except as such enforceability may 
be limited by applicable bankruptcy, insolvency, reorganization, moratorium 
or other laws of general application relating to or affecting the enforcement 
of creditors' rights and by the discretionary nature of equitable remedies, 
and except as rights to indemnity and contribution may be limited by 
applicable law.

         5.2.     Investment Representations.

                  (a)      The Investor represents and warrants to the 
                  Corporation as follows:

                           (i) It is acquiring the Series B Shares and, in the
                  event it should acquire Conversion Shares upon conversion of
                  the Series B Shares, it will be acquiring such Conversion
                  Shares, for its own account, for investment and not with a
                  view to the distribution thereof within the meaning of the
                  Securities Act.

                           (ii) It is an "accredited investor" as such term is
                  defined in Rule 501 (a) promulgated under the Securities Act.

                           (iii) It agrees that the Corporation may place a
                  legend on the certificates delivered hereunder stating that
                  the Series B Shares and any Conversion Shares have not been
                  registered under the Securities Act, and, therefore, cannot be
                  offered, sold or transferred unless they are registered under
                  the Securities Act or an exemption from such registration is
                  available, and that the Corporation may place stop transfer
                  orders on the transfer books of the Corporation.

                           (iv) It further understands that the exemptions from
                  registration afforded by Rule 144 and Rule 144A (the
                  provisions of each of which are known to it) promulgated under
                  the Securities Act depend on the satisfaction of various
                  conditions, and that, if applicable, Rule 144 may afford the
                  basis for sales only in limited amounts.

                           (v) It has such knowledge and experience in business
                  and financial matters and with respect to investments in
                  securities of 

                                       19




                  privately-held companies so as to enable it to
                  understand and evaluate the risks of the Investor's investment
                  in the Series B Shares and the Conversion Shares and form an
                  investment decision with respect thereto. It has been afforded
                  the opportunity during the course of negotiating the
                  transactions contemplated by this Agreement to ask questions
                  of, and to secure such information from, the Corporation and
                  its officers and directors as it deemed necessary to evaluate
                  the merits of entering into such transactions.

                           (vi) It has adequate net worth and means of providing
                  for its current needs and contingencies to sustain a complete
                  loss of its investment in the Corporation.

                  (b) The Investor further represents and warrants to the 
Corporation that: (i) it is a Delaware corporation, (ii) it was not formed 
for the specific purpose of acquiring any of the Series B Shares or the 
Conversion Shares, (iii) it has assets in excess of $5,000,000 and (iv) its 
principal office is located in Cambridge, Massachusetts.

         5.3. Brokers. The Investor has not retained, utilized or been 
represented by any broker or finder in connection with the transactions 
contemplated by this Agreement.

         SECTION 6. CONDITIONS TO THE OBLIGATIONS OF THE INVESTOR. The 
obligation of the Investor to purchase and pay for the Series B Shares is 
subject to the satisfaction, on or before such Closing Date, of the following 
conditions (unless waived in writing by the Investor):

         6.1 Representations and Warranties to be True and Correct. The 
representations and warranties contained in Section 4 hereof shall be true, 
complete and correct on and as of the Closing Date with the same effect as 
though such representations and warranties had been made on and as of the 
Closing Date, and the President and Treasurer of the Corporation shall have 
certified to such effect to the Investor in writing.

         6.2 Performance. The Corporation shall have performed and complied 
with all agreements contained herein required to be performed or complied 
with by it prior to or at the Closing, and the President and Treasurer of the 
Corporation shall have certified to the Investor in writing to such effect 
and to the further effect that all of the conditions set forth in this 
Section 6 have been satisfied.

         6.3 Investors' Rights Agreement. The Corporation and the Investor 
shall have executed and delivered the Investors' Rights Agreement.

                                       20




         6.4 Stock Restriction Agreement. The Corporation, the Management 
Stockholders and the Investor shall have executed and delivered the Stock 
Restriction Agreement.

         6.5 Registration Rights Agreement. The Corporation and the Investor 
shall have executed and delivered the Registration Rights Agreement.

         6.6 Nondisclosure and Invention Assignment Agreements. Each of the 
Corporation's officers, key employees or consultants and employees and 
consultants having access to confidential information of the Corporation 
shall have executed and delivered to the Corporation a written nondisclosure 
and invention assignment agreement in form and substance satisfactory to the 
Investor, and copies thereof have been delivered to counsel for the Investor.

         6.7  Restated Certificate of Incorporation. The Restated Certificate 
of Incorporation shall have been duly executed and shall have been filed with 
the Secretary of State of Delaware and shall be in full force and effect.

         6.8  Preemptive Rights. All stockholders of the Corporation having 
any preemptive, first refusal or other right with respect to the issuance of 
the Series B Shares or Conversion Shares shall have irrevocably waived the 
same in writing.

         6.9  Opinion of Corporation's Counsel. The Corporation shall have 
delivered to the Investor an opinion from Jenner & Block, counsel to the 
Corporation, in form and substance satisfactory to the Investor and its 
counsel.

         6.10 Supporting Documents. The Corporation shall have delivered to 
the Investor and its counsel copies of the following documents:

                           (a) the Restated Certificate of 
                  Incorporation, certified as of a recent date by
                  the Secretary of State of the State of Delaware;

                           (b) a certificate of the Secretary of State of
                  Delaware, dated as of a recent date, as to the due
                  incorporation and good standing of the Corporation, the
                  payment of all excise taxes by the Corporation and listing all
                  documents of the Corporation on file with said Secretary;

                           (c) a certificate of the Secretary or an Assistant
                  Secretary of the Corporation, dated the Closing Date, and
                  certifying: (A) that attached thereto is a true and complete
                  copy of the By-laws of the Corporation as in effect on the
                  date of such certification; (B) that attached thereto is a
                  true and complete copy of all resolutions adopted by the Board
                  of Directors and/or stockholders of the Corporation

                                       21




                  authorizing the execution, delivery and performance of this
                  Agreement, the other Related Documents, the issuance, sale and
                  delivery of the Series B Shares, the reservation, issuance and
                  delivery of the Conversion Shares and that all such
                  resolutions are in full force and effect and are all the
                  resolutions adopted in connection with the transactions
                  contemplated by this Agreement and the other Related
                  Documents; (C) that the Restated Certificate of Incorporation
                  has not been amended since the date of the last amendment
                  referred to in the certificate delivered pursuant to clause
                  (b) above; and (D) to the incumbency and specimen signature of
                  each officer of the Corporation executing this Agreement, the
                  other Related Documents, the stock certificates representing
                  the Series B Shares and any certificate or instrument
                  furnished pursuant hereto, and a certification by another
                  officer of the Corporation as to the incumbency and signature
                  of the officer signing the certificate referred to in this
                  clause (c); and

                           (d) such additional supporting documents and other
                  information with respect to the operations and affairs of the
                  Corporation as the Investor or its counsel reasonably may
                  request.

         6.11 No Adverse Change. There shall not have been any material 
adverse change in the Corporation, its business, financial condition, 
operations or prospects.

         6.12 Litigation. No proceeding challenging this Agreement or any of 
the other Related Documents, or any of the transactions contemplated hereby 
or thereby, or seeking to prohibit, alter, prevent or materially delay the 
Closing, shall have been instituted before any court, arbitrator or 
governmental body, agency or official and shall be pending.

         6.13 Compliance with Laws; Governmental Consents and Approvals. The 
purchase of and payment for the Series B Shares by the Investor shall not be 
prohibited by any law or governmental order or regulation; and all necessary 
consents, approvals, licenses, permits, orders and authorizations of, or 
registrations, declarations and filings with, any governmental or 
administrative agency or of any other Person with respect to any of the 
transactions contemplated under this Agreement or any of the other Related 
Documents shall have been duly obtained or made and shall be in full force 
and effect.

         6.14 All Proceedings to be Satisfactory. All corporate and other 
proceedings to be taken by the Corporation in connection with the 
transactions contemplated hereby and all documents incident thereto shall be 
satisfactory in form and substance to the Investor and its counsel, and the 
Investor and their counsel shall have received all such counterpart originals 
or certified or other copies of such documents as they reasonably may request.

                                       22




         SECTION 7.  RESEARCH COLLABORATION.

         7.1      Collaboration.

                  (a) The Corporation and the Investor hereby agree (i) to 
engage in the Collaborative "BioKeys" Research Project and the 
"ElectroScreen" Research Project, all as described in Exhibit F attached 
hereto, (ii) to engage in the research activities described in Section 7.1(c) 
below and (iii) to engage in such other research activities as the parties 
may agree upon from time to time. For purposes hereof, the term 
"Collaboration" shall mean the collaboration and other research activities 
engaged in by the parties pursuant to this Section 7. The terms and 
conditions of the Collaboration and of all research activities of the parties 
pursuant to the Collaboration shall be governed by, to the extent applicable, 
the provisions of this Section 7, the provisions of Exhibit F attached hereto 
and such other provisions as the parties may agree upon in writing from and 
after the date hereof. The term of the Collaboration (the "Term") shall 
commence on the date hereof and end on February 5, 2001, provided that the 
Investor shall be entitled to terminate the Collaboration at any time from 
and after November 5, 1997 by giving the Corporation at least thirty (30) 
days prior written notice of termination. For purposes of this Agreement, (A) 
the term "Collaboration Termination Date" shall mean the earlier of (i) 
February 5, 2001 or (ii) the effective date of termination of the 
Collaboration pursuant to the provisions of this Section 7.1(a), (B) the term 
"Minimum Research Period" shall mean the period commencing on the date hereof 
and ending on the earlier of (i) the Collaboration Termination Date or (ii) 
May 5, 1998 (the "Acquisition Option Expiration Date"), and (C) the term 
"Remaining Research Period" shall mean the period commencing on May 5, 1998 
and ending on the Collaboration Termination Date.

                  (b) During the Minimum Research Period, the Corporation and 
the Investor shall engage in the research activities described in Exhibit F 
attached hereto. The respective tasks, activities and obligations of the 
parties during the Minimum Research Period are set forth in Exhibit F 
attached hereto.

                  (c) In the event that the Investor elects not to exercise 
the Acquisition Option, the Investor shall, within thirty (30) days after the 
Acquisition Option Expiration Date, deliver to the Corporation a schedule 
listing all of the research programs then being conducted by the Investor 
(the "Specified Research Programs"). During the Remaining Research Period, 
the Corporation and the Investor shall (i) continue the research activities 
described in Exhibit F, (ii) engage in such research, screening, target 
discovery and validation, and drug discovery and development activities as 
the Investor shall request, provided that such research, screening, target 
discovery and validation and drug discovery and development activities are 
related to, or involve, biological targets that are within the scope of 

                                       23




the Specified Research Programs and (iii) engage in such other research 
activities as the parties may agree from time to time. The respective tasks, 
activities and obligations of the parties in connection with any of the 
matters on which the parties are collaborating during the Remaining Research 
Period shall be mutually agreed upon by the parties.

         7.2      Funding.

                  (a) On the first day of each month during the Minimum 
Research Period and on the first day of the first month immediately after the 
Minimum Research Period, the Investor shall reimburse the Corporation for any 
payments made by the Corporation during the immediately preceding month in 
respect of (i) salary and fringe benefits payable by the Corporation to no 
more than two scientists and one technician employed by the Corporation and 
engaged solely in activities relating the Collaboration, and (ii) laboratory 
supplies for use solely in activities relating to the Collaboration; 
provided, however, that the amount of any monthly payment that the Investor 
shall be required to make to the Corporation pursuant to the foregoing 
provisions of this Section 7.2(a) shall in no event exceed $18,334 (it being 
understood that any expenses incurred or payments made by the Corporation in 
connection with the Collaboration in any month during the Minimum Research 
Period in excess of $18,334 shall be the Corporation's sole responsibility 
and the Investor shall have no obligation to reimburse the Corporation with 
respect to any such excess). In addition, the Investor shall reimburse the 
Corporation for up to a total of $30,000 of travel expenses incurred by the 
Corporation in connection with travel by officers or employees of the 
Corporation in the performance of tasks and duties pertaining to the 
Collaboration, provided that such travel expenses are incurred by the 
Corporation, and are submitted by the Corporation for reimbursement, in 
accordance with the Investor's policy on reimbursable travel expenses that is 
applicable to all officers and employees of the Investor.

                  (b) On the first day of each month during the Remaining 
Research Period and on the first day of the first month immediately after the 
Remaining Research Period, the Investor shall reimburse the Corporation for 
the direct costs incurred by the Corporation in connection with activities 
relating to the Collaboration, provided that such costs shall not exceed the 
amount budgeted for such costs by mutual agreement of the Investor and the 
Corporation (it being understood that any costs incurred by the Corporation 
in connection with the Collaboration activities that are in excess of the 
amount budgeted by the parties for such costs shall be the Corporation's sole 
responsibility and the Investor shall have no obligation to reimburse the 
Corporation with respect to any such excess).

                  (c) The Investor shall also pay to the Corporation seven 
percent (7%) of all revenue actually received by the Investor from third 
parties to the extent that such revenue is directly attributable to (i) the 
sale of a third party anti-

                                       24




bacterial or anti-fungal drug that was discovered or developed as a result of 
the use of the Licensed Technology (as defined in Section 7.5 hereof), (ii) 
drug development milestone payments actually received by the Investor on 
account of any anti-bacterial or anti-fungal drug candidate that was 
discovered or developed as a result of the use of the Licensed Technology, 
and (iii) any licensing fees actually received by the Investor with respect 
to any sublicense of the Licensed Technology.

         7.3 Obligations Following Termination of Collaboration. Except for 
the Investor's obligation, pursuant to Section 7.2(a) above, to make a 
payment to the Corporation on the first day of the first month immediately 
after the Minimum Research Period and except for any other payment 
obligations of the Investor in connection with the Collaboration which are 
agreed upon by the parties in writing after the date hereof and which by 
their own terms survive the Collaboration Termination Date, the Investor 
shall have no obligations or liabilities to the Corporation pursuant to this 
Section 7 (including, without limitation, the obligation to make payments to 
the Corporation in connection with the Collaboration) from and after the 
Collaboration Termination Date.

         7.4 Exclusivity.

                  (a) Until the later of (i) the expiration of the 
Acquisition Option Period or (ii) if the Acquisition Option is exercised, the 
closing of the Acquisition, the Corporation shall not engage in any research 
or screening activities or programs, any research collaboration, any drug 
discovery or drug development collaboration, partnership or alliance, any 
licensing transaction, or any other kind of transaction, involving all or any 
portion of the Corporation's intellectual property or know-how or the 
intellectual property or know-how of any Person; provided, however, that the 
foregoing provisions of this Section 7.4(a) shall not preclude the 
Corporation from engaging in (i) the Collaboration or (ii) any research or 
screening activities or programs set forth in Schedule 7.4(a) attached 
hereto, all of which are research or screening activities or programs in 
which the Corporation is currently involved as of the date of this Agreement. 
The restrictions set forth in this Section 7.4(a) may be waived, in any 
instance, by written consent of the Investor.

                  (b) During the period commencing upon the expiration of the 
restrictions set forth in Section 7.4(a) above and ending on the 
Collaboration Termination Date, the Corporation shall not engage in any 
research or screening activities or programs, any research collaborations, 
any drug discovery or drug development collaborations, partnerships or 
alliances, any licensing transactions, or any other kind of transactions, in 
the anti-bacterial and/or anti-fungal therapeutic area; provided, however, 
that the foregoing provisions of this Section 7.4(b) shall not preclude the 
Corporation from engaging in (i) the Collaboration, (ii) any research or 
screening activities or programs set forth in Schedule 7.4(b) attached 
hereto, all of which are research or screening activities or programs in 
which the Corporation is 

                                       25




currently involved as of the date of this Agreement or (iii) any research or 
screening activity or program so long as it (A) covers a finite number of 
specific biological targets for drug discovery and development, (B) provides 
for the Corporation to engage in active research, discovery and development 
activities with respect to all of such biological targets, (C) provides for 
the payment to the Corporation of commercially reasonable consideration and 
(D) does not preclude the Corporation from entering into similar arrangements 
with other parties (including the Investor) relating to other targets in the 
same or any different field or pathogen. The restrictions set forth in this 
Section 7.4(b) may be waived, in any instance, by written consent of the 
Investor.

                  (c) Until the later of (i) the expiration of the 
Acquisition Option Period or (ii) if the Acquisition Option is exercised, the 
closing of the Acquisition, the Corporation, subject to any applicable 
nondisclosure agreements between the Corporation and third parties, shall 
discuss and coordinate in advance with the Investor any contacts, meetings, 
discussions or negotiations that the Corporation proposes to make or in which 
the Corporation proposes to participate, to the extent that such proposed 
contacts, meetings, discussions or negotiations relate to any research or 
screening activities or programs, any research collaboration, any drug 
discovery or drug development collaboration, partnership or alliance, any 
licensing transaction, or any other kind of transaction, involving all or any 
portion of the Corporation's intellectual property or know-how or the 
intellectual property or know-how of any Person; provided, however, that the 
foregoing provisions of this Section 7.4(c) shall not apply to (i) the 
Collaboration or (ii) any research or screening activities or programs set 
forth in Schedules 7.4(a) or 7.4(b) attached hereto, all of which are 
research or screening activities or programs in which the Corporation is 
currently involved as of the date of this Agreement.

         7.5 License. Subject to the provisions of this Section 7.5 hereof, 
the Corporation hereby grants to the Investor a worldwide license (the 
"License") to use any and all inventions, technology, know-how and 
intellectual property of the Corporation (collectively, the "Licensed 
Technology") for purposes of (i) researching, screening for, discovering or 
developing anti-bacterial or anti-fungal drug candidates or anti-bacterial or 
anti-fungal drug discovery targets or (ii) selling, licensing, marketing or 
otherwise commercializing anti-bacterial or anti-fungal drugs discovered or 
developed using any portion of the Licensed Technology during the Term. 
Without limiting the generality of the definition of the term "Licensed 
Technology" set forth above, such term shall include any patent or patent 
applications of the Corporation and any inventions, technology or know-how 
disclosed in such patents or patent applications. The License shall be 
perpetual and irrevocable. The License shall be exclusive to the extent and 
for the period of time that the Corporation has agreed to abide by the 
exclusivity provisions of Section 7.4 above. The Investor shall have the 
right to sublicense the License and the Licensed Technology. Except for any 
payments made or required to be made by the Investor 

                                       26




to the Corporation pursuant to Section 7.2 above in connection with the 
Collaboration, the Investor shall not have to pay or otherwise owe to the 
Corporation any consideration of any kind in connection with the License.

         7.6 Collaborative Research Agreement. The parties hereby acknowledge 
that the foregoing provisions of this Section 7 do not address all of the 
matters with respect to the Collaboration that would customarily be addressed 
in a stand-alone collaborative research agreement. Accordingly, the parties 
hereby agree that, within sixty (60) days after the Closing Date, the parties 
shall negotiate and enter into a collaborative research agreement with 
respect to the Collaboration (the "Collaborative Agreement"), which 
Collaborative Agreement shall contain terms and provisions that are 
consistent with all of the provisions set forth above in this Section 7 and 
such other terms and provisions as are customary for research collaborations 
similar to the Collaboration. In the event that the parties fail to reach 
agreement with respect to the terms and conditions of the Collaborative 
Agreement, the respective Chief Executive Officers of the parties shall, 
within thirty (30) days after the expiration of such sixty (60) day period, 
meet and negotiate in good faith a resolution of the parties' differences. If 
the parties' respective Chief Executive Officers are unable to resolve the 
parties' differences, then such differences shall be submitted to binding 
arbitration as provided in Section 7.7 below. Upon execution and delivery by 
both parties of the Collaborative Agreement, the provisions of this Section 7 
shall terminate and be superseded by the provisions of the Collaborative 
Agreement. Nothing in this Section 7.6 shall be construed as limiting the 
enforceability, validity or binding effect of any of the other provisions of 
this Section 7.

         7.7 Arbitration. If the parties are unable to agree on the terms and 
conditions of the Collaborative Agreement contemplated by Section 7.6 above 
prior to or during the thirty (30) day period referred to in Section 7.6 
above, the dispute issues shall be submitted to binding arbitration. The 
parties shall select one arbitrator, provided that, if the parties cannot 
agree on the arbitrator, each party shall select an arbitrator, and these two 
arbitrators will then select a third arbitrator. The arbitrator or 
arbitrators shall be accredited by the American Arbitration Association and 
shall be individuals with relevant business experience in structuring and 
negotiating biotechnology research collaborations; provided, however, that 
the parties may mutually agree in writing to waive either or both of the 
foregoing requirements. The arbitration shall be held in Boston, 
Massachusetts or in such other city in the United States as the parties may 
mutually agree. The arbitration session will be held no later than thirty 
(30) days after the expiration of the thirty (30) day period referred to in 
Section 7.6 above. The arbitrator or arbitrators shall render a decision 
within ten (10) business days of the conclusion of the arbitration session. 
The arbitration proceeding shall be conducted in accordance with the rules of 
the American Arbitration Association. The decision of the arbitrator or 
arbitrators shall be final and binding on both parties. If the

                                       27




parties are able to agree on the appointment of a single arbitrator, then the 
cost of such arbitrator shall be shared equally by both parties. If the 
parties are unable to agree on the appointment of a single arbitrator, each 
party shall bear the cost of the arbitrator appointed by such party and the 
cost of the third arbitrator shall be shared equally by both parties. Each 
party shall be responsible for all costs incurred by it in preparing for and 
participating in the arbitration.

         7.8 Termination. The provisions of this Section 7 shall 
automatically terminate upon consummation of the Acquisition.

         SECTION 8. USE OF PROCEEDS. The Corporation shall use the proceeds 
from the sale of the Series B Shares solely for working capital in the 
ordinary course of its business as currently conducted by the Corporation.

         SECTION 9. RESTRICTIONS ON TRANSFER. The Series B Shares and the 
Conversion Shares shall be subject to the restrictions on transfer set forth 
in Section 4 of the Investors' Rights Agreement.

         SECTION 10. INDEMNIFICATION. The Corporation agrees to indemnify, 
defend and hold the Investor (and its directors, officers, employees, agents 
and affiliates and the directors, officers, employees and agents of such 
affiliates) harmless against any and all liabilities, losses, costs or 
damages, together with all reasonable costs and expenses related thereto 
(including reasonable legal and accounting fees and expenses), incurred or 
suffered by any such indemnified Person arising from, relating to, or in 
connection with the untruth, inaccuracy or breach of any statements, 
representations, warranties or covenants of the Corporation contained herein. 
The Investor agrees to indemnify, defend and hold the Corporation (and its 
directors, officers, employees, agents and affiliates and the directors, 
officers, employees and agents of such affiliates) harmless against any and 
all liabilities, losses, costs or damages, together with all reasonable costs 
and expenses related thereto (including reasonable legal and accounting fees 
and expenses), incurred or suffered by any such indemnified Person arising 
from, relating to, or in connection with the untruth, inaccuracy or breach of 
any statements, representations, warranties or covenants of the Investor 
contained herein. Indemnification pursuant to this Section 10 shall be in 
addition to any liability the Corporation or the Investor may otherwise have.

                                       28




         SECTION 11.  GENERAL.

         11.1 Election to Board of Directors. The Corporation shall use its 
best efforts to cause a representative of the Investor to be elected as a 
director of the Corporation within thirty days after the Closing Date.

         11.2 Expenses. Each party hereto will pay its own expenses in 
connection with the transactions contemplated hereby, whether or not such 
transactions shall be consummated; provided, however, that, at the Closing, 
the Investor shall reimburse the Corporation, up to a maximum aggregate 
amount of $10,000, for any amounts paid or payable by the Corporation in 
respect of the reasonable fees, expenses and disbursements of the 
Corporation's outside legal, accounting and tax advisors but only if and to 
the extent that (i) such reasonable fees, expenses and disbursements pertain 
to the transactions contemplated by this Agreement and the Related Documents 
and (ii) the Corporation provides the Investor with a copy of the invoices 
submitted to the Corporation by such advisors and such invoices are 
sufficiently detailed to adequately support the amount of such fees, expenses 
and disbursements.

         11.3 Survival of Agreements. All covenants, agreements, 
representations and warranties made herein or in any of the other Related 
Documents, or any certificate or instrument delivered to the Investor 
pursuant to or in connection with this Agreement or any of the other Related 
Documents, shall survive the execution and delivery of this Agreement and 
each of the other Related Documents, the issuance, sale and delivery of the 
Series B Shares and the issuance and delivery of the Conversion Shares, and 
all statements contained in any certificate or other instrument delivered by 
the Corporation hereunder or thereunder or in connection herewith or 
therewith shall be deemed to constitute representations and warranties made 
by the Corporation.

         11.4 Brokerage. Each party hereto will indemnify and hold harmless 
the others against and in respect of any claim for brokerage or other 
commissions relative to this Agreement or to the transactions contemplated 
hereby, based in any way on agreements, arrangements or understandings made 
or claimed to have been made by such party with any third party.

         11.5 Parties in Interest. All representations, covenants and 
agreements contained in this Agreement by or on behalf of any of the parties 
hereto shall bind and inure to the benefit of the respective successors and 
permitted assigns of the parties hereto whether so expressed or not. Without 
limiting the generality of the foregoing, all representations, covenants and 
agreements benefiting the Investor shall inure to the benefit of any and all 
subsequent holders from time to time of Series B Shares or Conversion Shares.

                                       29




         11.6 Assignment. This Agreement and the respective rights and 
obligations of the parties hereto may not be assigned or delegated, except to 
the extent otherwise consented to in writing by the Corporation and the 
Investor and except that, after the Closing, the Investor may assign all of 
its rights under this Agreement to any Person.

         11.7 Remedies. In case that any one or more of the covenants and/or 
agreements set forth in this Agreement shall have been breached by any party 
hereto, the party or parties entitled to the benefit of such covenants or 
agreements may proceed to protect and enforce its or their rights, either by 
suit in equity and/or action at law, including, but not limited to, an action 
for damages as a result of any such breach and/or an action for specific 
performance of any such covenant or agreement contained in this Agreement. 
The rights, powers and remedies of the parties to this Agreement are 
cumulative and not exclusive of any other right, power or remedy which such 
parties may have under any other agreement or law. No single or partial 
assertion or exercise of any right, power or remedy of a party hereunder 
shall preclude any other or further assertion or exercise thereof.

         11.8 Entire Agreement. This Agreement contains the entire agreement 
among the parties with respect to the subject matter hereof and supersedes 
all prior and contemporaneous arrangements or understandings with respect 
thereto.

         11.9 Notices. All notices, requests, consents and other 
communications hereunder to any party shall be deemed to be sufficient if 
contained in a written instrument delivered in person or duly sent by first 
class, registered, certified or overnight mail, postage prepaid, or 
telecopied with a confirmation copy by regular mail, addressed or telecopied, 
as the case may be, to such party at the address or telecopier number, as the 
case may be, set forth below or such other address or telecopier number, as 
the case may be, as may hereafter be designated in writing by the addressee 
to the addresser listing all parties:

         (i)  If to the Corporation to:

                                      Novalon Pharmaceutical Corporation
                                      214 West Cameron Avenue, Suite B
                                      Chapel Hill, N.C. 27516
                                      Attention: Dana M. Fowlkes, M.D., Ph.D.,
                                                 President & CEO
                                      Telecopier:(919) 968-9255

                                       30




                                      with a copy to:

                                      Jenner & Block
                                      12th Floor
                                      601 Thirteenth Street, N.W.
                                      Washington, D.C. 20005
                                      Attention:  D. Joe Smith
                                      Telecopier: (203) 639-6066

         (ii) If to the Investor, to:

                                      Cubist Pharmaceuticals, Inc.
                                      24 Emily Street
                                      Cambridge, MA 02139
                                      Attention:  Scott M. Rocklage, Ph.D.
                                      Telecopier: (617) 576-0232

                                      with a copy to:

                                      Bingham, Dana & Gould LLP
                                      150 Federal Street
                                      Boston, MA 02110-1726
                                      Attention:  Julio E. Vega, Esquire
                                      Telecopier: (617) 951-8736


Any notice or other communication pursuant to this Agreement shall be deemed 
to have been duly given or made and to have become effective (i) when 
delivered in hand to the party to which it was directed, (ii) if sent by 
telex, telecopier, facsimile machine or telegraph and properly addressed in 
accordance with the foregoing provisions of this Section 11.9, when received 
by the addressee, (iii) if sent by commercial courier guaranteeing next 
business day delivery, on the business day following the date of delivery to 
such courier, or (iii) if sent by first-class mail, postage prepaid, and 
properly addressed in accordance with the foregoing provisions of this 
Section 11.9, (A) when received by the addressee, or (B) on the third 
business day following the day of dispatch thereof, whichever of (A) or (B) 
shall be the earlier.

         11.10 Amendments and Waivers. Any provision of this Agreement may be 
amended, modified or terminated, and the observance of any provision of this 
Agreement may be waived (either generally or in a particular instance and 
either retrospectively or prospectively), with, but only with, the written 
consent of each of the parties hereto.

                                       31




         11.11 Severability. Any provision of this Agreement that is 
prohibited or unenforceable in any jurisdiction shall, as to such 
jurisdiction, be ineffective to the extent of such prohibition or 
unenforceability without invalidating the remaining provisions hereof, and 
any such prohibition or unenforceability in any jurisdiction shall not 
invalidate or render unenforceable such provision in any other jurisdiction.

         11.12 No Waiver of Future Breach. No failure or delay on the part of 
any party to this Agreement in exercising any right, power or remedy 
hereunder shall operate as a waiver thereof. No assent, express or implied, 
by any party hereto to any breach in or default of any agreement or condition 
herein contained on the part of any other party hereto shall constitute a 
waiver of or assent to any succeeding breach in or default of the same or any 
other agreement or condition hereof by such other party.

         11.13 No Implied Rights or Remedies; Third Party Beneficiaries. 
Except as otherwise expressly provided in this Agreement, nothing herein 
expressed or implied is intended or shall be construed to confer upon or to 
give any Person, firm or corporation, other than the Corporation and the 
Investor, any rights or remedies under or by reason of this Agreement. Except 
as otherwise expressly provided in this Agreement, there are no intended 
third party beneficiaries under or by reason of this Agreement.

         11.14 Headings. The headings of the various sections of this 
Agreement have been inserted for convenience of reference only and shall not 
be deemed to be a part of this Agreement.

         11.15 Nouns and Pronouns. Whenever the context may require, any 
pronouns used herein shall include the corresponding masculine, feminine or 
neuter forms, and the singular form of names and pronouns shall include the 
plural and vice-versa.




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                                       32




         11.16 Governing Law. This Agreement shall be governed by and construed
in accordance with the laws of the State of Delaware, excluding the choice of
law rules thereof.

         11.17 Counterparts. This Agreement may be executed in any number of
counterparts, and each such counterpart shall be deemed to be an original
instrument, but all such counterparts together shall constitute but one
agreement.


         IN WITNESS WHEREOF, the parties hereto have executed this Series B
Convertible Preferred Stock Purchase Agreement as of the date first above
written.


                                       CORPORATION:

                                       NOVALON PHARMACEUTICAL
                                       CORPORATION


                                       By: [signature appears here]
                                           ----------------------------
                                           Name: Dana M. Fowlkes, M.D., Ph.D.
                                           Title: President & CEO


                                       INVESTOR:

                                       CUBIST PHARMACEUTICALS, INC.


                                       By: [signature appears here]
                                           ------------------------
                                           Scott M. Rocklage,
                                           President

                                       33