Document:

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                                                                    Exhibit 10.6

March 18, 1999

Mr. Taylor Jackson Crouch
83 Belcher Drive
Sudbury,MA 01776

tel/fax: (978) 440-9585

Dear Taylor:

This letter agreement (the "Agreement") affirms the terms and conditions of your
employment by VARIAGENICS, INC.. ("VARIAGENICS" or the "Company"). This
Agreement will be effective on your first day of employment with the Company
("Effective Date") and, together with an Invention and Non-Disclosure Agreement
and a Stock Option Agreement (or, at your discretion, a Stock Restriction)
Agreement, will constitute the entire agreement as to your employment by
VARIAGENICS, and supersedes any prior agreements or understandings, either
written or oral.

1.    Position

(a)   Your initial position within the Company will be President and Chief
      Business Officer. The Board of Directors will determine the duties of this
      position. Initially your role and responsibilities will include:

      (i)   Together with the President and Chief Technical Officer, you will be
            responsible for managing all of the operations of the Company.
      (ii)  You will be primarily responsible as the line manager for the
            Business Development, Corporate Development, Finance, and
            Administrative functions of the Company.
      (iii) You will be a member of the Board of Directors.

(b)   Your responsibilities, position, and location are subject to change at the
      discretion of the Company, but will continue to be consistent with the
      position of President.

(c)   Notwithstanding the foregoing, your responsibilities during your first
      year with the Company will not include engaging in any activities relating
      to products or services that are similar to those that were provided or
      marketed by your previous employer, Parexel International Corporation, and
      you agree not to engage in any such activities.

(d)   During your employment with the Company, you will devote your full
      business time and energies to the business and affairs of the Company, and
      not undertake any other employment or accept financial remuneration from
      any person or entity in the biotechnology industry, without express
      written consent of the Board of Directors.

2.    Compensation/Benefits

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Mr. Taylor Jackson Crouch
March 18, 1999
Page 2

(a)   Your salary will initially be $250,000 which will be reviewed at least
      annually by the Compensation Committee of the Board of Directors.

(b)   You will be eligible for performance-based bonuses at the sole discretion
      of the Compensation Committee and the Board of Directors. The target
      levels for variable compensation and options in the first year will be 30%
      of salary and 50,000 options, respectively.

(c)   You will receive options to purchase the Company's Common Stock at
      $0.64/share subject to a Stock Option Agreement (or a Stock Restriction
      Agreement which will include a buyback provision) in an amount equal to 3%
      of the then fully diluted shares of the Company upon completion of the
      first financing round of at least $10MM after the date of this letter, or,
      if no financing is completed prior to September 1, 1999, 3% of the fully
      diluted shares of the Company as of that date, whichever comes first. Of
      this amount, 35% will be vested as of six (6) months after the Effective
      Date, and 1/42 of the remainder will vest monthly for 42 months after that
      date or until your employment with the Company is terminated. Such shares
      will become fully vested in the event of acquisition of the Company or
      merger of the Company into a larger entity.

(d)   As of the Effective Date of this Agreement, you initially will be eligible
      to participate in all of the benefits offered to employees of the Company
      as outlined in the attached materials. Currently, the Company provides
      benefits including: (i) comprehensive health insurance, (ii) dental
      insurance, (iii) life insurance, (iv) short term disability insurance, (v)
      long term disability insurance, (vi) free parking near the Company or a T
      pass. The Company will provide you with four (4) weeks of paid vacation
      leave each year commencing with your Start Date. In addition, you will be
      entitled to six (6) paid Company holidays per year and four (4) paid
      floating holidays per year The Company retains the right to change, add or
      cease any particular benefit at any time with or without advance notice,
      but you will be afforded the same benefits while employed as other senior
      executives at the Company.

(e)   The Company shall reimburse you for all reasonable and necessary expenses
      incurred or paid by you in connection with, or related to, the performance
      of services to the Company under this Agreement, in accordance with
      Company policies in effect from time to time.

3.    Term

(a)   Your employment shall have an Initial Term ("Initial Term") of four years,
      beginning on the Effective Date, and ending, unless terminated earlier as
      specified below in Section 4.

(b)   This Agreement shall be automatically extended for an additional one (1)
      year term at the expiration of the Initial Term unless either party
      provides no less than thirty (30) days advance written notice of its
      intent not to extend.

4.    Early Termination and Compensation Upon Early Termination

                                      -2-
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Mr. Taylor Jackson Crouch
March 18, 1999
Page 3

(a)   If for any reason, other than for Cause as defined herein, or your
      inability, because of a physical or mental condition , to perform the
      essential functions of your position, within six (6) months of the
      Effective Date of the Agreement, you are unable to continue working for
      the Company, the Company will continue to pay you an amount equal to your
      full salary (with applicable withholdings and deductions) and will provide
      you with equivalent benefits (excluding vacation and
      transportation/parking), for a period of six (6) months from your last day
      of employment, provided that you comply with the non-competition and
      non-solicitation covenants set forth in paragraph 5, the anti-piracy
      covenants set forth in paragraph 6, and with your obligations under your
      Invention and Non-Disclosure Agreement.

(b)   You shall have the right to terminate the employment relationship at any
      time during the Initial Term of this Agreement, and during any subsequent
      extensions thereof, by providing the Company with thirty (30) days advance
      written notice of your intention to terminate, with or without "Good
      Reason" (which shall mean the breach of any material term of this
      Agreement by the Company, which breach is not cured within twenty (20)
      business days after written notice by you to the Company), and with or
      without advance notice.

      (i)   If you voluntarily leave the Company without Good Reason at any
            time, you will have no right to future compensation and no
            compensation shall be due to you for any period beyond the effective
            date of termination.
      (ii)  If, after six (6) months following the Effective Date, you
            voluntarily leave the Company with Good Reason at any time, the
            Company will continue to pay you an amount equal to your full salary
            (with applicable withholdings and deductions) and will provide you
            with equivalent benefits (excluding vacation and
            transportation/parking), for a period of nine (9) months from your
            last day of employment, provided that you comply with the
            non-competition and non-solicitation covenants set forth in
            paragraph 5, the anti-piracy covenants set forth in paragraph 6, and
            with your obligations under your Invention and NonDisclosure
            Agreement.

(c)   The Company shall have the right to terminate the employment relationship
      at any time during the Initial Term of this Agreement, and during any
      subsequent extensions thereof, with or without cause and with or without
      advance notice.

      (i)   If your employment is terminated by the Company without Cause any
            time after six (6) months following the Effective Date, the Company
            will continue to pay you an amount equal to your full salary (with
            applicable withholdings and deductions) and will provide you with
            equivalent benefits, excluding parking or transportation, for a
            period of nine (9) months from the date it informs you of its
            intention to terminate your employment, provided that you comply
            with the non-competition and non-solicitation covenants set forth in
            paragraph 5, the anti-

                                      -3-
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Mr. Taylor Jackson Crouch
March 18, 1999
Page 4

            piracy covenants set forth in paragraph 6, and your obligations
            under your Invention and Non-Disclosure Agreement.
      (ii)  If your employment is terminated by the Company without Cause during
            the first six (6) months, 35% of the stock options described in
            section 2(c) will become immediately vested.
      (iii) If your employment is terminated by the Company for Cause at any
            time, no compensation shall be due to you for any period beyond the
            effective date of termination. "Cause" shall mean any of the
            following: (A) the breach of any term of this Agreement; (B) the
            commission of any crime or embezzlement or other acts of dishonesty
            against the financial or business interest of the Company; (C) the
            commission of any act of dishonesty in your relations with the
            Company or in your representation of the Company to third parties,
            including regulatory authorities; (D) the use or possession of
            illegal drugs; (E) the willful refusal to perform your duties (which
            is not cured within ten (10) days subsequent to written notice by
            the Company); (F) and any other conduct or circumstance that
            constitutes cause as that term has been defined by Massachusetts
            common law. If your employment is terminated by the Company for
            Cause pursuant to this paragraph, you will remain subject to the
            non-competition and non-solicitation covenants set forth in
            paragraph 5 and the anti-piracy covenants set forth in paragraph 6.

(d)   This agreement shall terminate upon the Employee's death.

5.    Non-competition/Non-solicitation

The provisions contained in this paragraph will apply during the entire term of
your employment, and in the event that your employment is terminated early
pursuant to paragraph 4, these provisions will apply for a period of nine (9)
months following this early termination.

(a)   During your employment and for a period of nine (9) months thereafter, you
      shall not: (i) be associated as an employee, agent, advisor, servant,
      owner, partner, consultant, independent contractor or representative, or
      in any other capacity whatsoever with any person, partnership,
      corporation, business organization or other entity (without the prior
      written consent of the Company) which directly competes with the Company's
      business (a "Competing Business") which is defined as any business that
      provides pharmacogenomics and/or pharmacogenetics services as a core
      service area of that business; (ii) own any interest in a Competing
      Business, provided, however, the foregoing shall not prohibit you from
      owning not more than one per cent (1%) of the outstanding shares of a
      public company traded on a national stock exchange; or (iii) assist others
      to open or operate a Competing Business.

(b)   The foregoing restrictions are necessary for the protection of the
      business and goodwill of the Company and are considered by the Employee to
      be reasonable for such purpose. The Employee agrees that any breach of
      this Agreement is likely to cause the Company substantial and irrevocable
      damage and therefore, in the event of any such breach, the

                                      -4-
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Mr. Taylor Jackson Crouch
March 18, 1999
Page 5

      Employee agrees that the Company, in addition to such other remedies which
      may be available, shall be entitled to specific performance and other
      injunctive relief.

(c)   Should you violate any provision of paragraph 5(a), the Company, in
      addition to all other legal remedies, will have no obligation to continue
      any payments, salary or benefits pursuant to paragraph 4 or otherwise.

6.    Anti-Piracy of Employees

(a)   During your employment and for a period of twelve (12) months commencing
      on your last day of employment pursuant to this Agreement, you shall not,
      directly or indirectly, entice, solicit or encourage any Company employee
      to leave the employ of the Company, and shall not directly or indirectly
      be involved in the recruitment of any Company employee to become
      associated with any other entity.

(b)   Should you violate any provision of paragraph 6(a), the Company, in
      addition to all other legal remedies, will have no obligation to continue
      any payments, salary or benefits pursuant to paragraph 4 or otherwise.

(c)   The foregoing restrictions are necessary for the protection of the
      business and goodwill of the Company and are considered by the Employee to
      be reasonable for such purpose. The Employee agrees that any breach of
      this Agreement is likely to cause the Company substantial and irrevocable
      damage and therefore, in the event of any such breach, the Employee agrees
      that the Company, in addition to such other remedies which may be
      available, shall be entitled to specific performance and other injunctive
      relief.

7.    Workplace

The Company considers the safety and quality of the workplace to be very
important. You are expected to be familiar with and abide by the Company's
safety policies. You are expected to contribute to creating a working
environment that is both conducive to fostering the business objectives of the
Company and in which respect for the rights and dignity of all individuals is
maintained.

8.    Assignment

The Company shall have the right to assign this Agreement in the event the
Company is acquired (whether through stock or asset sale) by another company or
entity or otherwise merges, reorganizes, or reconstitutes itself into another
entity and this Agreement in such event shall remain in full force and effect.

9.    Choice of Law; Enforceability

You acknowledge that the Company's business is based out of and directed from
the Commonwealth of Massachusetts. You also acknowledge that during the course
of your

                                      -5-
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Mr. Taylor Jackson Crouch
March 18, 1999
Page 6

employment with the Company you will have substantial contacts with
Massachusetts. This Agreement shall be deemed to have been made in the
Commonwealth of Massachusetts, shall take effect as an instrument under seal
within Massachusetts, and the validity, interpretation and performance of this
Agreement shall be governed by, and construed in accordance with, the internal
law of Massachusetts, without giving effect to conflict of law principles. Both
parties agree that any action, demand, claim, or counterclaim relating to the
terms and provisions of this Agreement, to your employment by the Company, or to
any matter of dispute between you and the Company shall be commenced only in
Massachusetts in a court of competent jurisdiction.

10.   Miscellaneous

(a)   Should your employment be terminated pursuant to the provisions of
      paragraph 4(c)(ii)(C) or should the Company allege that you have violated
      paragraph 6(b) and for that reason terminate the payments, salary or
      benefits referenced therein, and should you dispute any such action, you
      may submit such dispute for binding arbitration before the American
      Arbitration Association. Such dispute shall be decided by a panel of three
      arbitrators, sitting in Boston, Massachusetts, and the proceedings shall
      be conducted pursuant to the Rules of the American Arbitration
      Association. Nothing herein shall abridge any right of the Company to seek
      injunctive or other relief for a violation of the provisions of paragraph
      6(b).

(b)   You acknowledge and agree that should you be promoted or reassigned to a
      function other than your present functions, the terms of this Agreement
      and the other agreements incorporated herein shall continue to apply with
      full force.

(c)   Should any provision or term of this Agreement be held to be invalid,
      illegal, or unenforceable, in whole or part, such invalidity, illegality,
      or unenforceability shall not affect the validity, legality, or
      enforceability of any other provision of this Agreement, and to the extent
      permissible by law, the parties agree that a court shall have the power to
      amend such specific provision so that it can be enforced to the fullest
      extent permissible by law.

(d)   No amendment, waiver, or revocation of this Agreement of any kind shall be
      effective unless supported by a written instrument executed by you and an
      authorized officer of the Company.

(e)   This offer of employment is conditioned upon execution of an Invention and
      Non-disclosure Agreement substantially in the form attached, and whose
      terms are expressly incorporated herein.

(f)   You hereby acknowledge that you have had an adequate opportunity to review
      these terms and conditions and to reflect upon and consider the terms and
      conditions of this Agreement. You further acknowledge that you fully
      understand its terms and have voluntarily executed this Agreement.

                                      -6-
<PAGE>

Mr. Taylor Jackson Crouch
March 18, 1999
Page 7

Kindly acknowledge your acceptance of this Agreement by signing both copies of
this letter where indicated and returning one to my attention.

VARIAGENICS, INC.

Date:      5/18/99                             By: /s/ Fred D. Ledley, M.D.
     ------------------                            -----------------------------
                                                   Fred D. Ledley, M.D.
                                                   President & CEO

By employee                                    By: /s/ Taylor Jackson Crouch
                                                   -----------------------------
                                                   Taylor Jackson Crouch

Date:       3/19/99
     ------------------

                                      -7-
<PAGE>

                                VARIAGENICS, INC.

                     Invention and Non-Disclosure Agreement

This Agreement is made between VARIAGENICS, INC., a Delaware corporation
(hereinafter referred to collectively with its affiliates and subsidiaries as
the "Company"), and Mr. Taylor Jackson Crouch (the "Employee"). In consideration
of the employment or the continued employment of the Employee by the Company,
the Company and the Employee agree as follows:

1.    Proprietary Information.

(a)   The Employee agrees that all information, whether or not in writing, of a
      private, secret or confidential nature concerning the Company's business,
      business relationships or financial affairs (collectively, "Proprietary
      Information") is and shall be the exclusive property of the Company. By
      way of illustration, but not limitation, Proprietary Information may
      include inventions, products, processes, methods, techniques, formulas,
      compositions, compounds, projects, developments, plans, research data,
      clinical data, financial data, personnel data, computer programs, customer
      and supplier lists, and contacts at or knowledge of customers or
      prospective customers of the Company. The Employee will not disclose any
      Proprietary Information to any person or entity other than employees of
      the Company or use the same for any purposes (other than in the
      performance of his/her duties as an employee of the Company) without
      written approval by an officer of the Company, either during or after
      his/her employment with the Company, unless and until such Proprietary
      Information has become public knowledge without fault by the Employee.

(b)   The Employee agrees that all files, letters, memoranda, reports, records,
      data, sketches, drawings, laboratory notebooks, program listings, or other
      written, photographic, or other tangible material containing Proprietary
      Information, whether created by the Employee or others, which shall come
      into his/her custody or possession, shall be and are the exclusive
      property of the Company to be used by the Employee only in the performance
      of his/her duties for the Company. All such materials or copies thereof
      and all tangible property of the Company in the custody or possession of
      the Employee shall be delivered to the Company, upon the earlier of: (i) a
      request by the Company or (ii) termination of his/her employment. After
      such delivery, the Employee shall not retain any such materials or copies
      thereof or any such tangible property.

(c)   The Employee agrees that his/her obligation not to disclose or to use
      information and materials of the types set forth in paragraphs (a) and (b)
      above, and his/her obligation to return materials and tangible property,
      set forth in paragraph (b) above, also extends to such types of
      information, materials and tangible property of customers of the Company
      or suppliers to the Company or other third parties who may have disclosed
      or entrusted the same to the Company or to the Employee.

<PAGE>

2.    Developments.

(a)   The Employee will make full and prompt disclosure to the Company of all
      inventions, improvements, discoveries, methods, developments, software,
      and works of authorship, whether patentable or not, which are created,
      made, conceived or reduced to practice by him/her or under his/her
      direction or jointly with others during his/her employment by the Company,
      whether or not during normal working hours or on the premises of the
      Company (all of which are collectively referred to in this Agreement as
      "Developments").

(b)   The Employee agrees to assign and does hereby assign to the Company (or
      any person or entity designated by the Company) all his/her right, title
      and interest in and to all Developments and all related patents, patent
      applications, copyrights and copyright applications. However, this
      paragraph 2(b) shall not apply to Developments which do not relate to the
      present or planned business or research and development of the Company and
      which are made and conceived by the Employee not during normal working
      hours, not on the Company's premises and not using the Company's tools,
      devices, equipment or Proprietary Information. The Employee understands
      that, to the extent this Agreement shall be construed in accordance with
      the laws of any state which precludes a requirement in an employee
      agreement to assign certain classes of inventions made by an employee,
      this paragraph 2(b) shall be interpreted not to apply to any invention
      which a court rules and/or the Company agrees falls within such classes.
      The Employee also hereby waives all claims to moral rights in any
      Developments.

(c)   The Employee agrees to cooperate fully with the Company, both during and
      after his/her employment with the Company, with respect to the
      procurement, maintenance and enforcement of copyrights, patents and other
      intellectual property rights (both in the United States and foreign
      countries) relating to Developments. The Employee shall sign all papers,
      including, without limitation, copyright applications, patent
      applications, declarations, oaths, formal assignments, assignments of
      priority rights, and powers of attorney, which the Company may deem
      necessary or desirable in order to protect its rights and interests in any
      Development. The Employee further agrees that if the Company is unable,
      after reasonable effort, to secure the signature of the Employee on any
      such papers, any executive officer of the Company shall be entitled to
      execute any such papers as the agent and the attorney-in-fact of the
      Employee, and the Employee hereby irrevocably designates and appoints each
      executive officer of the Company as his/her agent and attorney-in-fact to
      execute any such papers on his/her behalf, and to take any and all actions
      as the Company may deem necessary or desirable in order to protect its
      rights and interests in any Development, under the conditions described in
      this sentence.

(d)   Any publications, texts, or other creative writing endeavors unrelated to
      the Company's Business shall be outside the field of this Agreement and
      the provisions of section 2(b)

(e)   Business concepts, models plans, relationships, and other related assets
      developed by the Employee prior to this Agreement related to the topic of
      off-balance sheet drug

                                      -2-
<PAGE>

      development and the management and financing thereof, hereinafter referred
      to as "Off Balance Sheet Drug Development Plans" shall be outside the
      field of this Agreement and the provisions of section 2(b).

3.    Other Agreements.

The Employee hereby represents that, except as the Employee has disclosed in
Exhibit 1 to this Agreement or in writing to the Company, the Employee is not
bound by the terms of any agreement with any previous employer or other party to
refrain from using or disclosing any trade secret or confidential or proprietary
information in the course of his/her employment with the Company or to refrain
from competing, directly or indirectly, with the business of such previous
employer or any other party, or which would restrict his/her ability to accept
employment or perform work for the Company. The Employee further represents that
his/her performance of all the terms of this Agreement and as an employee of the
Company does not and will not breach any agreement to keep in confidence
proprietary information, knowledge or data acquired by the Employee in
confidence or in trust prior to his/her employment with the Company, and the
Employee will not disclose to the Company or induce the Company to use any
confidential or proprietary information or material belonging to any previous
employer or others.

4.    United States Government Obligations.

The Employee acknowledges that the Company from time to time may have agreements
with the other persons or with the United States Government, or agencies
thereof, which impose obligations or restrictions on the Company regarding
inventions made during the course of work under such agreements or regarding the
confidential nature of such work. The Employee agrees to be bound by all such
obligations and restrictions which are made known to the Employee and to take
all action necessary to discharge the obligations of the Company under such
agreements.

5.    Employment Status.

The Employee understand that this Agreement does not constitute a contract of
employment and does not imply that his/her employment will continue for any
period of time.

6.    Miscellaneous.

(a)   The invalidity or unenforceability of any provision of this Agreement
      shall not affect the validity or enforceability of any other provision of
      this Agreement.

(b)   This Agreement supersedes all prior agreements, written or oral, between
      the Employee and the Company relating to the subject matter of this
      Agreement. This Agreement may not be modified, changed or discharged in
      whole or in part, except by an agreement in writing signed by the Employee
      and the Company. The Employee agrees that any change or changes in his/her
      duties, salary or compensation after the signing of this Agreement shall
      not affect the validity or scope of this Agreement.

                                      -3-
<PAGE>

(c)   No delay or omission by the Company in exercising any right under this
      Agreement will operate as a waiver of that or any other right. A waiver or
      consent given by the Company on any one occasion is effective only in that
      instance and will not be construed as a bar to or waiver of any right on
      any other occasion.

(d)   The Employee expressly consents to be bound by the provisions of this
      Agreement for the benefit of the Company or any subsidiary or affiliate
      thereof to whose employ the Employee may be transferred without the
      necessity that this Agreement be re-signed at the time of such transfer.

(e)   The restrictions contained in this Agreement are necessary for the
      protection of the business and goodwill of the Company and are considered
      by the Employee to be reasonable for such purpose. The Employee agrees
      that any breach of this Agreement is likely to cause the Company
      substantial and irrevocable damage and therefore, in the event of any such
      breach, the Employee agrees that the Company, in addition to such other
      remedies which may be available, shall be entitled to specific performance
      and other injunctive relief.

(f)   This Agreement is governed by and will be construed as a sealed instrument
      under and in accordance with the laws of the Commonwealth of
      Massachusetts. Any action, suit, or other legal proceeding which is
      commenced to resolve any matter arising under or relating to any provision
      of this Agreement shall be commenced only in a court of the Commonwealth
      of Massachusetts (or, if appropriate, a federal court located within
      Massachusetts), and the Company and the Employee each consents to the
      jurisdiction of such a court.

THE EMPLOYEE ACKNOWLEDGES THAT HE/SHE HAS CAREFULLY READ THIS AGREEMENT AND
UNDERSTANDS AND AGREES TO ALL OF THE PROVISIONS IN THIS AGREEMENT.

WITNESS:

VARIAGENICS, INC.

Date:         3/18/99                    By:  /s/ Fred D. Ledley, M.D.
     -----------------------                  ------------------------
                                              Fred D. Ledley, M.D.
                                              President & CEO

By Employee:

Date:         3/19/99                     By: /s/ Taylor Jackson Crouch
     ------------------------                 -------------------------
                                              Taylor Jackson Crouch

                                      -4-
<PAGE>

                     Invention and Non-Disclosure Agreement

                                Other Agreements

Pursuant to section 3 of this Agreement, the following is a list of pertinent
agreements between the Employee and previous employers or other parties:

                  |_|   None
                  |X|   As shown below

Employment agreement with Parexel dated February 28, 1995

By:  VARIAGENICS, INC.:                   By:  Employee:

/s/ Fred D. Ledley, M.D.                  /s/ Taylor Jackson Crouch
----------------------------              ------------------------------

Dated:  3/19/99                           Dated:  3/19/99
      ----------------------                     -----------------------

                                      -5-<PAGE>

                                                                 Exhibit 10.7

January 27, 1998

Ms. Anne L. Bailey
Vice President, Development
VARIAGENICS, INC.
30 Spring Mill Drive
Malvern, PA 19355

Tel: (610) 889-9300
Fax: (610) 889-9304

Dear Anne:

This letter agreement (the "Agreement") affirms the terms and conditions of your
continued employment by VARIAGENICS, INC. ("VARIAGENICS" or the "Company") after
the Interim Period as defined in the Terms and Conditions sheet dated September
10, 1997 (the "Terms and Conditions Sheet").

This Agreement will be effective March 15, 1997 and will constitute the entire
agreement as to your employment by VARIAGENICS, and supersedes any prior
agreements or understandings, either written or oral, between us, including the
Terms and Conditions Sheet (except for paragraph 6 thereof), and except for the
"Invention and Non-Disclosure Agreement" dated September 10, 1997, which shall
remain in full force.

1.    Position

(a)   The Company agrees to continue your employment in the position of Vice
      President, Development reporting to the President and CEO. The President
      and CEO will determine the duties of this position. Initially your
      responsibilities will include leading teams to:

      (i)   Transfer technologies and know-how for variance detection from the
            Malvern facility to the Company's Cambridge headquarters.
      (ii)  Develop and implement high-throughput, quality-controlled process
            for variance detection.
      (iii) Develop and implement plan for diagnostic product development
            through corporate alliances or affiliated companies with Business
            Development.
      (iv)  Develop and implement advanced, high-throughput methods for genetic
            variance detection and diagnostics as well as quality control
            procedures required for clinical trials and commercialization of
            diagnostic and therapeutic products.

(b)   Your responsibilities, position, and location are subject to change at the
      discretion of the Company, but will continue to be consistent with the
      position of Vice President of the Company.

<PAGE>

January 27, 1998
Anne Bailey
Page 2

(c)   During your employment with the Company, you will devote your full
      business time and energies to the business and affairs of the Company, and
      not undertake any other employment or accept financial remuneration from
      any person or entity in the biotechnology industry, without express
      written consent by the President and CEO. You may continue to receive
      remuneration from Avitech Diagnostics based on your historical contractual
      relationships with that company.

(d)   Within six (6) months of the start of this Agreement, you will assume
      residence in the Boston, Massachusetts area.

2.    Compensation/Benefits

(a)   Your initial salary shall be $145,000.00 on an annualized basis, which
      will be reviewed by the Company from time to time, but at least once each
      year. The Company may increase or decrease the salary at any time at its
      sole discretion after providing at least 10 days written notice of its
      intent, and providing that any decrease in salary is commensurate with
      decreases offered to other employees at the level of Vice President. In
      addition, you will be eligible to receive bonuses of up to $14,500 for
      achieving milestones that will be agreed upon with the President and CEO.

(b)   The Company will also provide you with three (3) weeks of paid vacation
      leave each year accrued on a monthly basis. All such amounts must be used
      in the calendar year in which they were accrued and may not be carried
      over into the following year. The Company will also make reasonable
      accommodations to allow up to one (1) week of unpaid vacation per year. In
      addition, you will be entitled to six (6) paid Company holidays per year
      and four (4) paid floating holidays per year.

(c)   You will be entitled to participate in all employee fringe benefit
      programs generally offered to other management employees, including
      without limitation, medical, dental and life insurance plans. Currently,
      the Company provides benefits including: (i) comprehensive health
      insurance, (ii) dental insurance, (iii) life insurance, (iv) short term
      disability insurance, (v) long term disability insurance, (vi)
      participation in the Company's 401K plan, and (vii) free parking near the
      Company or a T pass. The Company retains the right to change, add or cease
      any particular benefit at any time with or without advance notice, but you
      will be afforded the same benefits while employed as other senior
      executives at comparable levels with the Company.

(d)   You will be provided with an option to purchase 32,000 shares of common
      stock at $0.64 per share with the Company subject to all the terms and
      restrictions contained in a "Stock Option Agreement" that provides for the
      vesting of 1/60 of the total number of shares each month for 60 months
      substantially in the form of the "Stock Option Agreement" attached as
      Exhibit A.

<PAGE>

January 27, 1998
Anne Bailey
Page 3

(e)   The Company will reimburse your relocation/moving expenses up to $15,000
      in connection with the presentation of actual and appropriate receipts to
      the Company.

(f)   The Company will assume certain severance/stay bonuses on behalf of
      Avitech Diagnostics as described in the final Purchase and Sale documents
      and paragraph 6 of the Terms and Conditions Sheet.

3.    Term

Your employment shall have an Initial Term ("Initial Term") of one year,
beginning March 15, 1998, and ending March 14, 1999, unless terminated earlier
as specified below in Section 4. This Agreement shall be automatically extended
for an additional one (1) year term at the expiration of the Initial Term unless
either party provides no less than thirty (30) days advance written notice of
its intent not to extend.

4.    Early Termination and Compensation Upon Early Termination

(a)   You shall have the right to terminate the employment relationship at any
      time during the Initial Term of this Agreement, and during any subsequent
      extensions thereof, with or without "Good Reason" (which shall mean the
      breach of any material term of this Agreement by the Company, which breach
      is not cured within ten (10) days subject to written notice by you to the
      Company), and with or without advance notice.

      (i)   If you voluntarily leave the Company without Good Reason at any
            time, you will have no right to future compensation and no
            compensation shall be due to you for any period beyond the effective
            date of termination.

      (ii)  If you voluntarily leave the Company with Good Reason at any time,
            the Company will continue to pay you an amount equal to your full
            salary (with applicable withholdings and deductions) and will
            provide you with equivalent benefits, excluding parking or
            transportation, for a period of six (6) months from your last day of
            employment, provided that you comply with the non-competition and
            non-solicitation covenants set forth in paragraph 5.

(b)   The Company shall have the right to terminate the employment relationship
      at any time during the Initial Term of this Agreement, and during any
      subsequent extensions thereof, with or without cause and with or without
      advance notice.

      (i)   If your employment is terminated by the Company without Cause during
            the Initial Term, the Company will continue to pay you an amount
            equal to your full salary (with applicable withholdings and
            deductions) and will provide you with

<PAGE>

January 27, 1998
Anne Bailey
Page 4

            equivalent benefits, excluding parking or transportation, for a
            period of six (6) months from the date it informs you of its
            intention to terminate your employment, or through the remainder of
            the Initial Term, whichever is longer, provided that you comply with
            the non-competition and non-solicitation covenants set forth in
            paragraph 5.

      (ii)  If your employment is terminated by the Company without Cause after
            the Initial Term and during a subsequent extension thereof, the
            Company will continue to pay you an amount equal to your full salary
            (with applicable withholdings and deductions) and will provide you
            with equivalent benefits, excluding parking or transportation, for a
            period of six (6) months from the date it informs you of its
            intention to terminate your employment, provided that you comply
            with the non-competition and non-solicitation covenants set forth in
            paragraph 5.

      (iii) If your employment is terminated by the Company for Cause at any
            time, no compensation shall be due to you for any period beyond the
            effective date of termination. "Cause" shall mean the breach of the
            terms of this Agreement (which breach is not cured within ten (10)
            days subsequent to written notice by the Company), commission of any
            crime or embezzlement or other acts of dishonesty against the
            financial or business interests of the Company, the use or
            possession of illegal drugs, the willful refusal to perform your
            duties (which is not cured within ten (10) days subsequent to
            written notice by the Company), and any other conduct or
            circumstance that constitutes cause as that term has been defined by
            Massachusetts common law.

5.    Non-competition / Non-solicitation

The non-competition and non-solicitation provisions contained in this paragraph
will apply during the entire term of your employment (including the Initial Term
and any subsequent extensions thereof), and in the event that your employment is
terminated early pursuant to paragraph 4, these provisions will apply for the
Initial Term or a period of six (6) months following this early termination,
whichever is longer.

(a)   During the applicable time period described above, in the continental
      United States, you shall not: (i) be associated as an employee, agent,
      servant, owner, partner, consultant, independent contractor or
      representative, or in any other capacity whatsoever with any person,
      partnership, corporation, business organization or other entity (without
      the prior written consent of the Company) which directly or indirectly
      competes with the Company's business (a "Competing Business"); (ii)
      canvass, solicit or accept any business from any of the Company's current
      or former clients; (iii) own any substantial interest in a Competing
      Business; or (iv) assist others to open or operate a Competing Business.

<PAGE>

January 27, 1998
Anne Bailey
Page 5

(b)   Should you violate any provision of paragraph 5(a), the Company will have
      no obligation to continue any payments, salary or benefits pursuant to
      paragraph 4 or otherwise.

6.    Anti-Piracy of Employees

(a)   For a period of twelve (12) months commencing on the later of your last
      day of employment pursuant to this Agreement, you shall not, directly or
      indirectly, entice, solicit or encourage any Company employee to leave the
      employ of the Company, and shall not directly or indirectly, be involved
      in the recruitment of any Company employee.

(b)   Should you violate any provision of paragraph 6(a), the Company will have
      no obligation to continue any payments, salary or benefits pursuant to
      paragraph 4 or otherwise.

7.    Workplace

The Company considers the safety and quality of the workplace to be very
important. You are expected to be familiar with and abide by the Company's
safety policies. You are expected to contribute to creating a working
environment that is both conducive to fostering the business objectives of the
Company and in which respect for the rights and dignity of all individuals is
maintained.

8.    Choice of Law; Enforceability

You acknowledge that the Company's business is based out of and directed from
the Commonwealth of Massachusetts. You also acknowledge that during the course
of your employment with the Company you will have substantial contacts with
Massachusetts. This Agreement shall be deemed to have been made in the
Commonwealth of Massachusetts, shall take effect as an instrument under seal
within Massachusetts, and the validity, interpretation and performance of this
Agreement shall be governed by, and construed in accordance with, the internal
law of Massachusetts, without giving effect to conflict of law principles. Both
parties agree that any action, demand, claim or counterclaim relating to the
terms and provisions of this Agreement, or to its breach or its formation, shall
be commenced in Massachusetts in a court of competent jurisdiction. Both parties
further acknowledge that venue shall exclusively lie in Massachusetts and that
material witnesses and documents would be located in Massachusetts.

9.    Miscellaneous

(a)   You acknowledge and agree that should you be promoted or reassigned to
      functions other than your present functions, the terms of this Agreement
      and the other agreements incorporated herein shall continue to apply with
      full force.

<PAGE>

January 27, 1998
Anne Bailey
Page 6

(b)   Should any provision or term of this Agreement be held to be invalid,
      illegal or unenforceable, in whole or part, such invalidity, illegality,
      or unenforceability shall not affect the validity, legality or
      enforceability of any other provision of this Agreement, and to the extent
      permissible by law, the parties agree that a court shall have the power to
      amend such specific provision so that it can be enforced to the fullest
      extent permissible by law.

(c)   No amendment, waiver or revocation of this Agreement of any kind shall be
      effective unless supported by a written instrument executed by you and an
      authorized officer of the Company.

(d)   You hereby acknowledge that you have had adequate opportunity to review
      these terms and conditions and to reflect upon and consider the terms and
      conditions of this Agreement. You further acknowledge that you fully
      understand its terms and have voluntarily executed this Agreement.

Kindly acknowledge your acceptance of this Agreement by signing both copies of
this letter where indicated and returning one to my attention.

WITNESS: VARIAGENICS, INC.

Date:       2/5/98                        By: /s/  Fred D. Ledley, M.D.
      ------------------------                ---------------------------
                                          Fred D. Ledley, M.D.
                                          President & CEO

By Employee:

Date:       2/5/98                        By: /s/  Anne Bailey
     -------------------------                ---------------------------
                                          Anne L. Bailey

<PAGE>

                                VARIAGENICS, INC.

                                  ATTACHMENT A

                     INVENTION AND NON-DISCLOSURE AGREEMENT

This Agreement is made between VARIAGENICS, INC., a Delaware corporation
(hereinafter referred to collectively with its subsidiaries as the "Company"),
Anne Bailey (the "Employee").

In consideration of the employment or the continued employment of the Employee
by the Company, the Company and the Employee agree as follows:

1.    Proprietary Information.

(a)   The Employee agrees that all information, whether or not in writing, of a
      private, secret or confidential nature concerning the Company's business,
      business relationships or financial affairs (collectively, "Proprietary
      Information") is and shall be the exclusive property of the Company. By
      way of illustration, but not limitation, Proprietary Information may
      include inventions, products, processes, methods, techniques, formulas,
      compositions, compounds, projects, developments, plans, research data,
      clinical data, financial data, personnel data, computer programs, customer
      and supplier lists, and contacts at or knowledge of customers or
      prospective customers of the Company. The Employee will not disclose any
      Proprietary Information to any person or entity other than employees of
      the Company or use the same for any purposes (other than in the
      performance of his/her duties as an employee of the Company) without
      written approval by an officer of the Company, either during or after
      his/her employment with the Company, unless and until such Proprietary
      Information has become public knowledge without fault by the Employee.

(b)   The Employee agrees that all files, letters, memoranda, reports, records,
      data, sketches, drawings, laboratory notebooks, program listings, or other
      written, photographic, or other tangible material containing Proprietary
      Information, whether created by the Employee or others, which shall come
      into his/her custody or possession, shall be and are the exclusive
      property of the Company to be used by the Employee only in the performance
      of his/her duties for the Company. All such materials or copies thereof
      and all tangible property of the Company in the custody or possession of
      the Employee shall be delivered to the Company, upon the earlier of: (i) a
      request by the Company or (ii) termination of his/her employment. After
      such delivery, the Employee shall not retain any such materials or copies
      thereof or any such tangible property.

(c)   The Employee agrees that his/her obligation not to disclose or to use
      information and materials of the types set forth in paragraphs (a) and (b)
      above, and his/her obligation to return materials and tangible property,
      set forth in paragraph (b) above, also extends to such types of
      information, materials and tangible property of customers of the Company

                                       1
<PAGE>

      or suppliers to the Company or other third parties who may have disclosed
      or entrusted the same to the Company or to the Employee.

2.    Developments.

(a)   The Employee will make full and prompt disclosure to the Company of all
      inventions, improvements, discoveries, methods, developments, software,
      and works of authorship, whether patentable or not, which are created,
      made, conceived or reduced to practice by him/her or under his/her
      direction or jointly with others during his/her employment by the Company,
      whether or not during normal working hours or on the premises of the
      Company (all of which are collectively referred to in this Agreement as
      "Developments").

(b)   The Employee agrees to assign and does hereby assign to the Company (or
      any person or entity designated by the Company) all his/her right, title
      and interest in and to all Developments and all related patents, patent
      applications, copyrights and copyright applications. However, this
      paragraph 2(b) shall not apply to Developments which do not relate to the
      present or planned business or research and development of the Company and
      which are made and conceived by the Employee not during normal working
      hours, not on the Company's premises and not using the Company's tools,
      devices, equipment or Proprietary Information. The Employee understands
      that, to the extent this Agreement shall be construed in accordance with
      the laws of any state which precludes a requirement in an employee
      agreement to assign certain classes of inventions made by an employee,
      this paragraph 2(b) shall be interpreted not to apply to any invention
      which a court rules and/or the Company agrees falls within such classes.
      The Employee also hereby waives all claims to moral rights in any
      Developments.

(c)   The Employee agrees to cooperate fully with the Company, both during and
      after his/her employment with the Company, with respect to the
      procurement, maintenance and enforcement of copyrights, patents and other
      intellectual property rights (both in the United States and foreign
      countries) relating to Developments. The Employee shall sign all papers,
      including, without limitation, copyright applications, patent
      applications, declarations, oaths, formal assignments, assignments of
      priority rights, and powers of attorney, which the Company may deem
      necessary or desirable in order to protect its rights and interests in any
      Development. The Employee further agrees that if the Company is unable,
      after reasonable effort, to secure the signature of the Employee on any
      such papers, any executive officer of the Company shall be entitled to
      execute any such papers as the agent and the attorney-in-fact of the
      Employee, and the Employee hereby irrevocably designates and appoints each
      executive officer of the Company as his/her agent and attorney-in-fact to
      execute any such papers on his/her behalf, and to take any and all actions
      as the Company may deem necessary or desirable in order to protect its
      rights and interests in any Development, under the conditions described in
      this sentence.

3.    Other Agreements.

                                       2
<PAGE>

The Employee hereby represents that, except as the Employee has disclosed in
Exhibit A to this Agreement or in writing to the Company, the Employee is not
bound by the terms of any agreement with any previous employer or other party to
refrain from using or disclosing any trade secret or confidential or proprietary
information in the course of his/her employment with the Company or to refrain
from competing, directly or indirectly, with the business of such previous
employer or any other party. The Employee further represents that his/her
performance of all the terms of this Agreement and as an employee of the Company
does not and will not breach any agreement to keep in confidence proprietary
information, knowledge or data acquired by the Employee in confidence or in
trust prior to his/her employment with the Company, and the Employee will not
disclose to the Company or induce the Company to use any confidential or
proprietary information or material belonging to any previous employer or
others.

4.    United States Government Obligations.

The Employee acknowledges that the Company from time to time may have agreements
with the other persons or with the United States Government, or agencies
thereof, which impose obligations or restrictions on the Company regarding
inventions made during the course of work under such agreements or regarding the
confidential nature of such work. The Employee agrees to be bound by all such
obligations and restrictions which are made known to the Employee and to take
all action necessary to discharge the obligations of the Company under such
agreements.

5.    No Employment Contract.

The Employee understand that this Agreement does not constitute a contract of
employment and does not imply that his/her employment will continue for any
period of time.

6.    Miscellaneous.

(a)   The invalidity or unenforceability of any provision of this Agreement
      shall not affect the validity or enforceability of any other provision of
      this Agreement.

(b)   This Agreement supersedes all prior agreements, written or oral, between
      the Employee and the Company relating to the subject matter of this
      Agreement. This Agreement may not be modified, changed or discharged in
      whole or in part, except by an agreement in writing signed by the Employee
      and the Company. The Employee agrees that any change or changes in his/her
      duties, salary or compensation after the signing of this Agreement shall
      not affect the validity or scope of this Agreement.

(c)   This Agreement will be binding upon the Employee's heirs, executors and
      administrators and will inure to the benefit of the Company and its
      successors and assigns.

(d)   No delay or omission by the Company in exercising any right under this
      Agreement will operate as a waiver of that or any other right. A waiver or
      consent given by the Company on any one occasion is effective only in that
      instance and will not be construed as a bar to or waiver of any right on
      any other occasion.

                                       3
<PAGE>

(e)   The Employee expressly consents to be bound by the provisions of this
      Agreement for the benefit of the Company or any subsidiary or affiliate
      thereof to whose employ the Employee may be transferred without the
      necessity that this Agreement be re-signed at the time of such transfer.

(f)   The restrictions contained in this Agreement are necessary for the
      protection of the business and goodwill of the Company and are considered
      by the Employee to be reasonable for such purpose. The Employee agrees
      that any breach of this Agreement is likely to cause the Company
      substantial and irrevocable damage and therefore, in the event of any such
      breach, the Employee agrees that the Company, in addition to such other
      remedies which may be available, shall be entitled to specific performance
      and other injunctive relief.

(g)   This Agreement is governed by and will be construed as a sealed instrument
      under and in accordance with the laws of the Commonwealth of
      Massachusetts. Any action, suit, or other legal proceeding which is
      commenced to resolve any matter arising under or relating to any provision
      of this Agreement shall be commenced only in a court of the Commonwealth
      of Massachusetts (or, if appropriate, a federal court located within
      Massachusetts), and the Company and the Employee each consents to the
      jurisdiction of such a court.

THE EMPLOYEE ACKNOWLEDGES THAT HE/SHE HAS CAREFULLY READ THIS AGREEMENT AND
UNDERSTANDS ANT) AGREES TO ALL OF THE PROVISIONS IN THIS AGREEMENT.

WITNESS: VARIAGENICS, INC.

Date:       9/15/97                       By: /s/  Fred D. Ledley, M.D.
      ------------------------                ---------------------------
                                          Fred D. Ledley, M.D.
                                          President

By Employee:

Date:       9/15/97                       By: /s/  Anne Bailey
     -------------------------                ---------------------------
                                          Anne L. Bailey

                                       4
<PAGE>

                                VARIAGENICS, INC.

                     INVENTION AND NON-DISCLOSURE AGREEMENT

                                    EXHIBIT A

                                OTHER AGREEMENTS

Pursuant to section 3 of this Agreement, the following is a list of pertinent
agreements between the Employee and previous employers or other parties:

      None
      As shown below

            1. FMC Corporation: Expires 2/17/2000 - Confidentiality regarding at
            Biochem GEI products.

By VARIAGENICS, INC.                         By Employee:

By: /s/ Fred D. Ledley, M.D.      9/15/97    By: /s/  Anne Bailey,      9/15/97
    ---------------------------   --------       -------------------    -------
Fred D. Ledley, M.D.              Date       Anne L. Bailey               Date
President

                                       5

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