<PAGE>
                                                                    Exhibit 10.8


                              EMPLOYMENT AGREEMENT
                              (for David S. Barlow)

     THIS EMPLOYMENT AGREEMENT (this "Agreement") is dated as of February 7,
2003 (the "Effective Date"), by and between Biostream, Inc., a Massachusetts
corporation having its principal place of business at 160 Second Street,
Cambridge, Massachusetts 02142 (the "Employer"), and David S. Barlow (the
"Employee").

                                   WITNESSETH:

     WHEREAS, the Employer is engaged in the business of developing and
marketing imaging pharmaceuticals which detect human disease; and

     WHEREAS, the Employee possesses the experience necessary in administration
and general and active supervision and direction of the daily operations of a
biopharmaceutical business in order to fulfill the responsibilities as Chairman
and Chief Executive Officer of the Employer; and

     WHEREAS, the Employer desires to employ the Employee, and the Employee
desires to be employed by the Employer, all in accordance with the terms and
provisions of this Agreement.

     NOW, THEREFORE, in consideration of the covenants and promises hereinafter
contained, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the Employer and the Employee
represent, covenant and agree as follows:

     1. Employment. The Employer hereby employs the Employee to serve as
Chairman and Chief Executive Officer of the Employer in accordance with the
terms and provisions of this Agreement, and the Employee hereby accepts such
employment with the Employer. Employee also shall serve as a member of the Board
of Directors of the Employer.

     2. Term. The term of this Agreement shall commence on the Effective Date
and shall continue until this Agreement is terminated as hereinafter provided.

     3. Compensation. As compensation for all services rendered by the Employee
to the Employer pursuant to this Agreement, the Employer shall pay to the
Employee the following amounts during the term of this Agreement:

            (a) Base Compensation. The Employer shall pay to the Employee base
compensation at no less than the rate set forth on Schedule A attached hereto
and herein incorporated by reference (the "Base Compensation"). The Base
Compensation shall be payable pursuant to the Employer's standard payroll
practices, except as otherwise noted on Schedule A. The Base Compensation shall
be reviewed by the compensation committee of the Board of the Employer annually
and increases in the Base Compensation, if any, shall be evidenced by the
updating and initialing of Schedule A by both parties hereto.

<PAGE>

            (b) Incentive Bonus. In addition to the Base Compensation, the
Employee shall be eligible to receive an annual fiscal year incentive bonus with
a maximum annual amount equal to seventy-five percent (75%) of the then current
Base Compensation (the "Incentive Bonus"). Payment of the Incentive Bonus shall
be subject to the discretion of the Board and will be based upon accomplishment
of goals provided to the Employee by the Board from time to time and based upon
revenue growth, profitability and achievement of specific corporate milestones.
The Board may elect to award the Incentive Bonus to the Employee in cash or in
the Employer's capital stock (at its then-current fair market value), but a
capital stock bonus requires the consent of the Employee.

            (c) Signing Bonus. Upon execution of this Agreement, the Employee
shall be entitled to receive from the Company an amount equal to $21,153.85 (the
"Signing Bonus"). The Signing Bonus shall be paid in one lump sum on the date
that the Company commences payment of Base Compensation to the Employee pursuant
to Schedule A attached hereto, such bonus payment to be made subject to the
Employer's standard payroll practices.

     4. Vacation and Employee Benefits.

            (a) Vacation. The Employee shall be entitled to an annual paid
vacation equal to four weeks annually. Vacation shall be taken at such times so
as not to interfere with the proper operation of the Employer's business.

            (b) Benefits Generally. The Employee shall be entitled to receive
and participate in such employee benefits as the Employer shall from time to
time determine to provide to its executives generally. At a minimum, the
Employee shall receive medical and dental insurance at the Employer's expense.

            (c) Indemnification Rights. The Employee shall be entitled to
indemnification, including advance reimbursement of expenses, to the fullest
extent permitted by applicable law, and shall be entitled to receive an
indemnification agreement with terms equivalent to any indemnification agreement
that the Employer executes with any of its officers or directors.

            (d) Registration Rights. The Employee shall be entitled to the
benefit of any so-called "piggy-back" registration rights and related provisions
that the Employer has granted or grants to any third party on the same basis as
the most favorable provisions received by any such third party.

            (e) Participation Rights. The Employee shall be entitled to rights
equivalent to the Employer's outside investors with respect to rights to
purchase additional equity securities issued by the Employer in order to
maintain the Employee's percentage interest in the Employer's equity securities.

                                       2
<PAGE>

     5. Stock Incentives.

            (a) Options. Subject to the vesting provisions described below, the
Employee shall be entitled to purchase, simultaneously with the execution of
this Agreement, 3,285,000 shares (the "Restricted Shares") of the Employer's
common stock at a per share price equal to $0.10 per share, which is the fair
market value of such common stock as most recently determined by the Board for
purposes of incentive stock option grants. The Employee shall pay the par value
of the restricted shares ($.01 per share) in cash and shall also execute a 50%
recourse, non-interest bearing, balloon promissory note for the balance of the
purchase price in the form attached as Exhibit A hereto. The Company represents
to the Employee that the current fully diluted capitalization of the Company is
accurately set forth in the spreadsheet set forth as Exhibit B hereto, and that
the Company is under no obligation, actual or contingent, to issue any
securities other than those set forth in Exhibit B, including the notes thereto.

            (b) Vesting. 20% of the restricted shares shall be vested upon
purchase and the remainder shall be "unvested shares." An additional 5% of the
restricted shares shall vest on each quarterly (three-month) anniversary of the
Effective Date, provided that the Employee is still employed by the Employer on
such date or is then receiving a Severance Package (as defined in Section 15
below). In the event of a Change of Control (as defined below), all of the
unvested restricted shares immediately shall vest, provided that the Employee is
still employed by the Employer on the date of such Change of Control, or is then
receiving a Severance Package.

            (c) Restrictions. All restricted shares shall be subject to the
terms and conditions of a restricted stock agreement in the form attached hereto
as Exhibit C.

            (d) Change of Control. For purposes of this Agreement "Change of
Control" shall mean the occurrence of one or more of the following events:

(i) any "person" (as such term is used in Sections 13(d) and 14(d)(2) of the
Securities Exchange Act of 1934, as amended (the "Exchange Act")) becomes a
"beneficial owner" (as such term is defined in Rule 13d-3 promulgated under the
Exchange Act) (other than the Employer, any trustee or other fiduciary holding
securities under an employee benefit plan of the Employer, or any corporation
owned, directly or indirectly, by the stockholders of the Employer, in
substantially the same proportions as their ownership of stock of the Employer),
or any or group of persons acting in concert becomes a beneficial owner,
directly or indirectly, of securities of the Employer, representing more than
fifty percent (50%) of the combined voting power or fully diluted equity
interest of the Employer's then outstanding equity securities, except as a
result of a financing transaction where all proceeds are received directly by
the Company that is not intended as a sale of the business of the Employer; or

(ii) the stockholders of the Employer approve a merger or consolidation of the
Employer with any other corporation or other entity, other than (A) a merger or
consolidation which would result in the equity securities of the Employer
outstanding immediately prior thereto continuing to represent (either by
remaining outstanding or by being converted into equity securities of the

                                       3
<PAGE>

surviving entity) fifty percent (50%) or more of the outstanding equity interest
of the Employer or such surviving entity outstanding immediately after such
merger or consolidation or (B) a merger or consolidation effected to implement a
recapitalization of the Employer (or similar transaction) in which no "person"
(as hereinabove defined) other than Employee acquires more than fifty percent
(50%) of the equity interest of the Employer's then outstanding securities; or

(iii) the stockholders of the Employer approve a plan of complete liquidation of
the Employer or an agreement for the sale or disposition by the Employer of all
or substantially all of the Employer's assets.

      6. Description of Duties. During the term of this Agreement, the Employee
shall be the Chairman and Chief Executive Officer of the Employer and shall:

            (a) Devote on a full time basis all necessary time, best efforts,
professional skills, attention and energies to the fulfillment of the duties
customarily associated with such position and the accomplishment of the goals
provided by the Board of Directors of the Employer to the Employee from time to
time; and

            (b) Act in accordance herewith, and in all accounts be responsible
and responsive to, the Board of Directors of Employer.

      7. General Services. During the term of this Agreement, the Employee
shall:

            (a) Observe the Employer's policies and standards of conduct, as
well as customary standards of business conduct, including any standards
prescribed by law or regulation;

            (b) Perform his duties hereunder in a manner that preserves and
protects the Employer's business reputation; and

            (c) Do all things and render such services as may be necessary or
beneficial in carrying out any of the foregoing.

      8. Non-Disclosure of Proprietary or Confidential Information and
Confidential Communications. For the purposes of this Section 8, the term
"Employer" shall include, and the protections granted the Employer hereunder
shall extend to, ATP Therapeutics, Inc., Biostream Therapeutics, Inc. (f/k/a
Zebra Pharmaceuticals, Inc.), and any other entities now or hereinafter
affiliated, acquired or created by Biostream, Inc. The Employee recognizes and
acknowledges that the marketing plans and business strategy, the names and
addresses of the Employer's customers, the particular needs and application of
such customers for diagnostic imaging techniques, the names and addresses of the
Employer's suppliers, the Employer's purchasing history with its suppliers, the
names and other pertinent data concerning the persons employed by the Employer's
suppliers who are responsible for supplying the Employer with products and
services, the Employer's proprietary computer software programs, trade secrets
and any other confidential and proprietary information concerning the business
or affairs of the Employer (including but not limited to marketing and business
plans and strategies, research protocols,

                                        4
<PAGE>

procedures data, results, and cost information) (hereinafter collectively
referred to as the Confidential Information) constitute a valuable, proprietary,
special and unique asset of the Employer's business. The Employee further
recognizes and acknowledges that any communications, whether written, oral or
otherwise, that the Employer or any of the Employer's employees has with the
Employer's existing or prospective customers and clients and affiliated research
institutions and scientists are extremely confidential (hereinafter the
"Confidential Communications"). The term Confidential Information shall exclude
any information that has been made public through no fault of the Employee.

     The Employee shall not, for any reason whatsoever, during or after the
termination of his employment with the Employer, use, disclose or allow access
to, for his own benefit or for that of another, the Confidential Information or
the Confidential Communications (or any part thereof) to any person, firm,
corporation, association or other entity for any reason or for any purpose
whatsoever.

     In the event of a breach or threatened breach by the Employee of the
provisions of this Section, the Employer shall be entitled to an injunction
restraining the Employee from so using, disclosing or allowing access to, in
whole or in part, the Confidential Information and the Confidential
Communications or from rendering any services to any person, firm, corporation,
association or other entity to whom the Confidential Information or the
Confidential Communications, in whole or in part, have been disclosed or are
threatened to be disclosed. Nothing herein shall be construed as prohibiting the
Employer from pursuing any other remedies available to the Employer for such
breach or threatened breach, including, but not limited to, the recovery of
damages and reasonable attorneys' fees from the Employee.

     Upon termination of this Agreement by either party for any reason, the
Employee shall return to the Employer any of the Confidential Information,
Confidential Communications, charts, company literature, reports, Employer
credit cards or other proprietary materials of the Employer then in the
Employee's possession and all other materials of the Employer which the Board of
Directors of the Employer requests the Employee to so return.

     This Section shall in all respects survive any termination of this
Agreement and shall remain in full force and effect thereafter. In the event
that any provision of this Section 8 shall conflict with any term or condition
of any other confidentiality agreement between the Employer and the Employee,
then the more restrictive provision shall be deemed to apply in order to
accomplish the purposes of this Section 8 and such other agreements, that being
to protect the Employer's Confidential Information and Confidential
Communications.

     In the event of the Employee's breach of this Section 8, the Employee shall
immediately and irrevocably forfeit future payments under the Severance Package
as hereinafter defined in Section 15. Nothing in this paragraph shall be
construed to limit or cap the Employer's damages in the event of a breach of
this Section 8.

     9. Covenant Not to Compete; Non-solicitation of Employees and Customers.
For the purposes of this Section 9, the term "Employer" shall include, and the
protections granted the Employer hereunder shall extend to, ATP Therapeutics,
Inc., Biostream Therapeutics, Inc. (f/k/a

                                       5
<PAGE>

Zebra Pharmaceuticals, Inc.), and any other entities now or hereinafter
affiliated, acquired or created by Biostream, Inc. The Employee agrees that
while employed by the Employer and for a continuous period of one (1) year
following the date of the termination of his employment with the Employer either
voluntarily without "Good Reason" or involuntarily by the Company for "cause"
(the "Restricted Period"), he shall not (without the express prior written
consent of the Board of Directors of the Employer), directly or indirectly,
compete with the Employer. In construing the foregoing prohibition, the Employee
shall be deemed to be competing with the Employer if he shall become
self-employed in, or accept employment with, consult with, render services to or
become associated with, own, manage, operate, join, control, or participate in
the ownership, management, operation, or control of, or be connected in any
material manner with, or directly or indirectly enter into the employment of, or
make a substantial investment in, any corporation, partnership, proprietorship
or other type of business organization or entity which engages in, any business
(a "Competing Business") involving the sale, distribution, development or
research concerning diagnostic imaging of the human cardio-vascular system or
other lines of the Employer which directly and materially competes with the
product lines in or with which the Employer is then currently involved.

     The Employee further agrees that, during his employment with the Employer
and during the Restricted Period, he shall not solicit any of the Employer's
employees, existing customers or prospective customers (of which the Employee is
then currently aware), affiliated research institutions or scientists, on behalf
of himself or any Competing Business.

     This Section 9 shall in all respects survive any termination of this
Agreement and shall remain in full force and effect during the Restricted
Period.

     In the event of the Employee's breach of this Section 9 during the
Restricted Period, the Employee shall immediately and irrevocably forfeit future
payments to the Employee under the Severance Package as hereinafter defined in
Section 15.

     10. Assignment of Rights. Any and all information, data, inventions,
discoveries, materials, notebooks and other work product which the Employee
conceives, develops or acquires during his employment with the Employer, which
directly or indirectly relates to work performed for the Employer, shall be the
sole and exclusive property of the Employer. The Employee shall promptly execute
any and all documents necessary and take such further actions as the Employer
may deem necessary to assign any and all of the Employee's right, title and
interest in such property to the Employer.

     11. Intellectual Property. For the purposes of this Section 11, the term
"Employer" shall include, and the protections granted the Employer hereunder
shall extend to, ATP Therapeutics, Inc., Biostream Therapeutics, Inc. (f/k/a
Zebra Pharmaceuticals, Inc.), and any other entities now or hereinafter
affiliated, acquired or created by Biostream, Inc. During the Employee's
employment at the Employer, the Employee shall promptly assist with and execute
any and all applications, assignments or other documents which an officer or
director of the Employer shall deem necessary or useful in order to obtain and
maintain patent, trademark or other intellectual property protection for the
Employer's products or services. After the termination date of his employment
with the Employer, the Employee shall use reasonable

                                       6
<PAGE>

efforts to assist the Employer on intellectual property matters as they relate
to his employment, and the Employer shall reasonably compensate the Executive
for his time and expense.

     12. Documents, Records, etc. All documents, records, data, apparatus,
equipment and other physical property, whether or not pertaining to Confidential
Information, which are furnished to the Employee by the Employer or are produced
by the Employee in connection with the Employee's employment will be and remain
the sole property of the Employer. The Employee will return to the Employer all
such materials and property as and when requested by the Employer. In any event,
and whether or not the Employer so specifically requests, the Employee will
return all such materials and property immediately upon termination of the
Employee's employment for any reason. The Employee will not retain any such
material or property or any copies thereof after such termination.

     13. Third-Party Agreements and Rights. The Employee hereby confirms that he
is not bound by the terms of any agreement with any previous employer or other
party which restricts in any way the Employee's use or disclosure of information
or the Employee's engagement in any business. The Employee represents to the
Employer that the Employee's execution of this Agreement, the Employee's
employment with the Employer and the performance of the Employee's proposed
duties for the Employer will not violate any obligations the Employee may have
to any such previous employer or other party. In the Employee's work for the
Employer, the Employee will not disclose or make use of any information in
violation of any agreements with or rights of any such previous employer or
other party, and the Employee will not bring to the premises of the Employer any
copies or other tangible embodiments of nonpublic information belonging to or
obtained from any such previous employer or other party.

     14. Restricted Activities. During the term of this Agreement, the Employee
shall not engage in any business activities or ventures outside of the business
activities of the Employer without the express prior written consent of the
Employer's Board; provided, however, that nothing in this Agreement shall be
construed as preventing the Employee from:

         (a) investing the Employee's assets in any company or other entity in a
manner not prohibited by Section 9 and in such form or manner as shall not
require any material activities on the Employee's part in connection with the
operations or affairs of the companies or other entities in which such
investments are made; or

         (b) engaging in religious, charitable or other community or non-profit
activities that do not impair the Employee's ability to fulfill the Employee's
duties and responsibilities under this Agreement.

     15. Termination.

         A. Termination Without Cause.

                (a) Notwithstanding anything herein to the contrary, this
Agreement may be terminated by either the Employer (by act of its Board) or the
Employee, at any time, without cause; provided, however, that the party desirous
of terminating this Agreement shall

                                       7
<PAGE>

give the other party prior written notice of such termination. In either event,
the Employer may determine the Employee's final day of employment hereunder. The
date specified in any notice of termination as the Employee's final day of
employment shall be referred to herein as the Termination Date.

                  (b) In the event that the Employer (by act of its Board)
terminates this Agreement without cause pursuant to this subsection (A) of
Section 15, or the Employee voluntarily resigns for Good Reason (defined below),
then the Employee shall be entitled to receive severance pay equal the Base
Compensation rate as of the Termination Date in equal monthly installments for a
period of twelve (12) months (the "Post-Termination Period") from the
Termination Date (the "Severance Package"). The Employer also agrees to make
available to the Employee, as part of the Severance Package, continuation of
group health plan benefits to the extent authorized by and consistent with 29
U.S.C. Section 1161 et seq. (commonly known as "COBRA"), and any other benefits
the Employee is receiving as of the Termination Date with the cost of the
regular premium for such benefits shared in the same relative proportion by the
Employer and the Employee as in effect on the Termination Date.

                  (c) For purposes of this Agreement, "Good Reason" shall mean:

                        (i) a reduction of the Employee's salary or insurance
benefits other than a reduction approved by the Employee in writing; or

                        (ii) a significant change in the Employee's title,
responsibilities and/or duties which constitutes, when compared to the
Employee's title, responsibilities and/or duties as of the Effective Date, a
demotion; or

                        (iii) the relocation of the offices at which the
Employee is principally employed as of the Effective Date to a location more
than fifty (50) miles from such office, which relocation is not approved by the
Executive.

                  (d) In the event of the Employee's voluntary termination, then
the Employee shall, at the request of the Board of the Employer, continue as an
employee of the Employer for an additional thirty (30) day period after the
Termination Date for the purpose of assisting the Employer in locating and
training a suitable replacement for the Employee. During such additional period,
the Employee shall be entitled to full compensation and benefits and the
Employee shall continue to be bound by all of the terms contained herein. Any
such extended term shall extend the Post-Termination Period by an equal number
of days.

            B. Termination With Cause.

                  (a) The Employer (by act of its Board) may terminate this
Agreement immediately for "cause" by giving written notice to the Employee. As
used herein, the term "cause" shall mean the Employee's: (i) addiction to
illegal drugs; (ii) willful failure or refusal to perform his duties hereunder
after written notice from the Board and an opportunity to cure; (iii) knowing
acts of dishonesty which materially adversely affect the Employer; (iv)
indictment for a felony or crime involving moral turpitude, fraud, embezzlement
or misrepresentation. In the

                                       8
<PAGE>

event that this Agreement is terminated pursuant to this subsection (B), the
Employee forfeits and shall not be entitled to the Severance Package, or other
benefits or bonus of any kind whatsoever for any period after the Termination
Date set forth in the notice given by the Employer to the Employee.

            C. Disability.

                  (a) If the Employee shall be disabled so as to be unable to
perform the essential functions of the Employee's then existing position or
positions under this Agreement, the Employer may remove the Employee from any
responsibilities and/or reassign the Employee to another position with the
Employer during the period of such disability. If the period of disability
extends for more than six (6) months, the Employer may terminate the Employee's
employment without further liability on the part of the Employer, except that
the Employee shall be entitled to the Severance Package. The Employer may elect,
at its sole discretion, to purchase a disability insurance package for the
Employee. In the event that the Employer so elects to purchase a disability
insurance package and the Employee subsequently becomes entitled to payments of
the disability insurance benefit, any payments pursuant to the Severance
Package, as defined in this Section 15, or payments of salary by the Employer
will be reduced by the amount of the disability insurance benefit payments
received by the Employee.

                  (b) If any question shall arise as to whether during any
period the Employee is disabled so as to be unable to perform the essential
functions of the Employee's then existing position or positions, the Employee
may, and at the request of the Employer shall, submit to the Employer a
certification in reasonable detail by a physician selected by the Employer, to
whom the Employee or the Employee's guardian has no reasonable objection, as to
whether the Employee is so disabled or how long such disability is expected to
continue, and such certification shall, for the purposes of this Agreement, be
conclusive of the issue. The Employee shall cooperate with any reasonable
request of the physician in connection with such certification. If such question
shall arise and the Employee shall fail to submit such certification, the
Employer's determination of such issue shall be binding on the Employee. Nothing
in this Section 15(c) shall be construed to waive the Employee's rights, if any,
under existing law including, without limitation, the Family and Medical Leave
Act of 1993,29 U.S.C. 2601, et seq. and the Americans with Disabilities Act, 42
U.S.C. 12101 et seq.

     D. Death or Retirement. The Employee's employment under this Agreement will
be deemed to have terminated without further liability on the part of the
Employer if the Employee dies or retires.

     E. Certain Termination Benefits. Unless otherwise specifically provided in
this Agreement or otherwise required by law, all compensation and benefits
payable to the Employee under this Agreement shall terminate on the date of
termination of the Employee's employment under this Agreement.

     F. No Right to Continuing Employment. The Employee agrees that nothing
contained in this Agreement shall be construed to give the Employee a right to
continuing employment beyond the Termination Date.

                                       9
<PAGE>

     16. Litigation and Regulatory Cooperation. During and after the Employee's
employment, the Employee shall cooperate fully with the Employer in the defense
or prosecution of any claims or actions now in existence or which may be brought
in the future against or on behalf of the Employer which relate to events or
occurrences that transpired while the Employee was employed by the Employer. The
Employee's full cooperation in connection with such claims or actions shall
include, but not be limited to, being available to meet with counsel to prepare
for discovery or trial and to act as a witness on behalf of the Employer at
mutually convenient times. During and after the Employee's employment, the
Employee also shall cooperate fully with the Employer in connection with any
investigation or review of any federal, state or local regulatory authority as
any such investigation or review relates to events or occurrences that
transpired while the Employee was employed by the Employer. The Employer shall
reimburse the Employee for any reasonable out-of-pocket expenses incurred in
connection with the Employee's performance of obligations pursuant to this
Section 16.

     17. Injunction. The Employee agrees that it would be difficult to measure
any damages caused to the Employer which might result from any breach by the
Employee of the promises set forth in Section 8, and that in any event money
damages would be an inadequate remedy for any such breach. Accordingly, the
Employee agrees that if the Employee breaches, or proposes to breach, any
portion of this Agreement, the Employer shall be entitled, in addition to all
other remedies that it may have, to an injunction or other appropriate
preliminary equitable relief to restrain any such breach without showing or
proving any actual damage to the Employer.

     18. No Assignment. The Employee acknowledges that the services to be
rendered by him pursuant to this Agreement are unique. Accordingly, the Employee
shall not assign any of his rights or delegate any of his duties or obligations
under this Agreement.

     19. Severability. Subject only to the reformation of time, geographical and
occupational limitations as set forth in Section 20 hereof, all of the terms and
provisions contained in this Agreement are severable and, in the event that any
portion or provision of this Agreement (including, without limitation, any
portion or provision of any section of this Agreement) shall to any extent be
deemed unenforceable or invalid by a court of competent jurisdiction, then the
remainder of this Agreement, or the application of such portion or provision in
circumstances other than those as to which it is so declared unenforceable or
invalid, shall not be affected thereby, and each portion and provision of this
Agreement shall be valid and enforceable to the fullest extent permitted by law.

     20. Reformation of Time Geographical and Occupational Limitations. In the
event that any provision in this Agreement is held to be unenforceable by a
court of competent jurisdiction because it exceeds the maximum time,
geographical or occupational limitations permitted by applicable law, then such
provision(s) shall be and hereby are reformed to the maximum time, geographical
and occupational limitations as may be permitted by applicable law.

                                       10
<PAGE>

      21. Specific Performance. Both parties recognize that the services to be
rendered under this Agreement by the Employee are special, unique and of an
extraordinary character, and that in the event of breach by the Employee of the
terms or conditions of this Agreement to be performed by him, the Employer shall
be entitled, if it so elects, to institute and prosecute proceedings in any
court of competent jurisdiction, either at law or in equity, to obtain damages
for any breach of this Agreement to enforce the specific performance thereof by
the Employee, or to enjoin the Employee from engaging in such activity, but
nothing contained herein shall be construed to prevent such other remedy in the
courts, in case of any breach of this Agreement by the Employee, as the Employer
may elect to invoke.

      22. Massachusetts Law: Choice of Forum. This Agreement shall be governed,
construed and interpreted by, and in accordance with, the laws of the
Commonwealth of Massachusetts, without reference to its principles of conflicts
of laws. Any actions concerning enforcement of this Agreement or in any way
relating to the subject matter of this Agreement shall be litigated only in
Massachusetts state or federal courts of proper jurisdiction and venue. Each
party hereto expressly agrees to submit to such jurisdiction and venue for the
purposes of this Agreement. Notwithstanding the foregoing, the Employer may seek
to enforce the Employee's covenants described in Sections 6, 7, 8 and 9 hereof
in any jurisdiction and venue in which the Employee then resides, breaches or
threatens to breach such covenants.

      23. Entire Agreement. This Agreement constitutes the entire agreement of
the parties hereto, and replaces all prior agreements, promises, representations
and understandings between the Employer and the Employee whatsoever concerning
the limited subject matter hereof (other than the Stock Plan and any related
Stock Option Agreement entered into between the Employer and the Employee).
There are no other agreements, conditions or representations, oral or written,
express or implied, which form the basis for this Agreement.

      24. Assignment; Successors and Assigns, Etc. Neither the Employer nor the
Employee may make any assignment of this Agreement or any interest herein, by
operation of law or otherwise, without the prior written consent of the other
party; provided, however, that the Employer may assign its rights under this
Agreement without the consent of the Employee in the event that the Employer
shall effect a reorganization, consolidate with or merge into any other
corporation, partnership, organization or other entity, or transfer all or
substantially all of its properties or assets to any other corporation,
partnership, organization or other entity. This Agreement shall inure to the
benefit of and be binding upon the Employer and the Employee, their respective
successors, executors, administrators, heirs and permitted assigns.

      25. Modification. No waiver or modification of this Agreement or of any
covenant, condition, or limitation contained herein shall be valid unless in a
writing of subsequent date hereto and duly executed by the party to be charged
therewith and no evidence of any waiver or modification shall be offered or
received in evidence in any proceeding, arbitration, or litigation between the
parties hereto arising out of or affecting this Agreement, or the rights or
obligations of the parties hereunder, unless such waiver or modification is in
writing, duly executed as aforesaid. The parties further agree that the
provisions of this Section may not be waived except as herein set forth.

                                       11

<PAGE>

      26. Section Headings. The section headings contained in this Agreement are
for convenience only, and shall in no manner be construed as part of this
Agreement.

      27. Waiver of Breach. The waiver by either party of a breach or violation
of any provision of this Agreement shall not operate as, or be construed to be,
a waiver of any subsequent breach thereof.

      28. Notices. Any and all notices required or permitted to be given under
this Agreement shall be sufficient if furnished in writing, sent by certified or
registered mail, return receipt requested to the party's address set forth in
the Prologue of this Agreement, or to such other address as such party may
specify in writing.

      29. Counterparts. This Agreement may be executed in any number of
counterparts, each of which when so executed and delivered shall be taken to be
an original; but such counterparts shall together constitute one and the same
document.

                                       12

<PAGE>

      IN WITNESS WHEREOF, the parties have executed this Agreement on the day
and year here above first written.

BIOSTREAM, INC.

By: /s/ John W. Babich
    ------------------------
Name: John W. Babich, Ph.D.
Title: President

/s/ David S. Barlow
----------------------------
David S. Barlow

                                       13

<PAGE>

                                   SCHEDULE A
            (As Amended from time to time pursuant to Paragraph 3(a))

                                Base Compensation

<TABLE>
<CAPTION>
Annual Rate of Base
    Compensation         Agreed to by Employee      Agreed to by Employer
--------------------     ---------------------      ---------------------
<S>                      <C>                        <C>
$220,000.00
</TABLE>

The Employee agrees that payment of his Base Compensation by the Employer shall
be deferred until the first to occur of the following events: (1) the Employer
has received a cumulative total of at least $2.3 million in cash (comprised of
net cash flow from operations, gross proceeds from debt or equity financings or
the gross proceeds of any other cash-generating activities) or (2) a Change of
Control has occurred. Immediately following the occurrence of either of such
events, all deferred Base Compensation shall be paid to the Employee in cash.

(Must be initialed by both parties each time amended to be effective.)

Exhibit A - Form of Promissory Note
Exhibit B - Capitalization Spreadsheet
Exhibit C - Form of Restricted Stock Agreement
Exhibit D - Form of Stock Pledge Agreement

                                       14