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                                                                  EXHIBIT 10.25

                                Variagenics, Inc.
                                60 Hampshire St.
                               Cambridge, MA 02139

                          EXECUTIVE RETENTION AGREEMENT

CONFIDENTIAL

November 15, 2001

Taylor Jackson Crouch
83 Belcher Drive
Sudbury, MA 01776

Dear Taylor:

         This letter agreement (the "Retention Agreement") shall confirm our
agreement with respect to additional compensation you will receive in
connection with your continued service as the President and Chief Executive
Officer of Variagenics, Inc. (the "Company") during the [_____________]
period which commenced on October 11, 2001 and terminates on [______] (the
"Retention Period"). To the extent the Retention Agreement augments or
differs from the terms of your Employment Agreement dated March 18, 1999 (the
"Employment Agreement") or any of your Stock Option Agreements dated
September 22, 1999, February 11, 2000 or January 3, 2001 (collectively, the
"Option Agreements"), the Employment Agreement and the Option Agreements are
hereby amended to such extent.

         In addition to the existing terms and conditions of your Employment
Agreement and Option Agreements, this Retention Agreement confirms that if
you resign your employment at any time during the Retention Period, so long
as you provide a minimum of two (2) weeks advance notice in writing, such
resignation shall be treated as a resignation for Good Reason, pursuant to
the Employment Agreement, and any cash payments due pursuant to Section
4(b)(i) of the Employment Agreement shall be paid in a lump sum upon the
termination of your employment with the Company. In addition, because of the
crucial role you have agreed to take on with respect to certain critical
objectives during the Retention Period, you shall receive the compensation
and benefits noted below, subject to the following conditions:

CASH BONUSES

         Apart from continuing to be paid at the rate of $13,541.67 per
semi-monthly pay period as long as you remain employed by the Company, you
will be eligible to receive a total cash bonus of up $162,500 (the "Bonus
Potential") if you attain the following objectives during the Retention
Period:

         (a) RECRUITMENT--If a new Chief Science Officer/Vice President,
         Research & Development is hired during the Retention Period, you shall
         receive a payment equal to twenty-five percent (25%) of the total Bonus
         Potential within thirty (30) days following


--------------------
Portions of this Exhibit were omitted and have been filed separately with the
Secretary of the Commission pursuant to the Company's application requesting
confidential treatment under Rule 24b-2 of the Securities Exchange Act of
1934.

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         the earlier of (i) the individual's first day of employment or (ii)
         the execution of an employment agreement between the Company and the
         individual;

         (b) STRATEGIC RELATIONSHIPS--If a letter of intent is executed with
         respect to a collaborative transaction with a pharmaceutical or biotech
         company [____________________________________________________________],
         you shall receive a payment equal to twelve and one-half percent
         (12.5%) of the total Bonus Potential within thirty (30) days following
         execution of such letter of intent. If a second such letter of intent
         is executed, you shall receive an additional payment equal to twelve
         and one-half percent (12.5%) of the total Bonus Potential within
         thirty (30) days following execution of such letter of intent;

         (c) [____________________________]--[_______________________________],
         you shall receive a payment equal to, you shall recieve a payment equal
         to twenty-five percent (25%) of the total Bonus Potential within thirty
         (30) days following execution of such letter of intent, provided,
         however, that [_______________________________________] during the
         Retention Period, this portion of the Bonus Potential shall be
         reallocated among the four (4) other cash bonus objectives on a pro
         rata basis; and

         (d) BUDGET--If you present to the Board of Directors a reasonably
         detailed written budget that demonstrably will [_____________________
         _____________] and confer with the Board of Directors regarding the
         same in the context of a Board Meeting, you shall receive a payment
         equal to twenty-five percent (25%) of the total Bonus Potential within
         thirty (30) days following such Board Meeting.

         Any cash payments shall be subject to customary federal, state and
local withholdings, and any Bonus Potential amounts actually earned during
the Retention Period that remain unpaid upon the expiration of the Retention
Period shall remain due and payable in accordance with the terms of preceding
paragraphs (a) - (d) in this Cash Bonuses section.

STOCK OPTIONS

         (a) EXISTING STOCK OPTIONS--Any stock options that were granted
         pursuant to the Option Agreements that have not vested as of the date
         of such resignation or termination shall vest and become exercisable
         upon the earlier of (i) [________________] or (ii) the date on which
         you resign your employment or the Company terminates your employment.
         To the extent permitted by law, such options shall remain exercisable
         for a period of one hundred eighty (180) days commencing on your final
         date of employment with the Company (so long as such exercise period
         does not exceed the expiration date of the particular options, as
         stated in the stock option agreement subject to which particular
         options were granted).

         (b) RETENTION STOCK OPTIONS--The Board of Directors, or their
         duly-authorized designees, shall grant you 175,500 stock options with
         an exercise price of $2.26 per share, subject to the terms of the
         Amended 1997 Employee, Director and Consultant


--------------------
Portions of this Exhibit were omitted and have been filed separately with the
Secretary of the Commission pursuant to the Company's application requesting
confidential treatment under Rule 24b-2 of the Securities Exchange Act of
1934.

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         Stock Option Plan and a stock option agreement on the form most
         recently approved by the Board of Directors, as qualified by this
         paragraph (the "Retention Options"). If you are still employed by the
         Company on March 31, 2002 or your employment has been terminated at the
         directive of the Board of Directors prior thereto, 87,750 of such
         stock options shall vest and become exercisable as of that date. The
         remaining 87,500 shall vest and become exercisable as follows,
         assuming you remain employed by the Company on each vesting date:
         (i) 21,938 on April 30, 2002; (ii) 21,938 on May 31, 2002; (iii) 21,937
         on June 30, 2002; and (iv) 21,937 on July 10, 2002. To the extent
         permitted by law, any such stock options shall remain exercisable for
         a period of one hundred eighty (180) days commencing on your final date
         of employment with the Company (so long as such exercise period does
         not exceed the expiration date of such options, as stated in the stock
         option agreement subject to which such options may be granted).

         (c) PERFORMANCE STOCK OPTIONS--If, at a time when you are still
         employed by the Company during the Retention Period, the Company (i)
         [________________________] or (ii) [______________________________] or
         [________________________], the Board of Directors, or their
         duly-authorized designees, shall grant you 115,500 stock options with
         an exercise price of $2.26 per share, subject to the terms of the
         Amended 1997 Employee, Director and Consultant Stock Option Plan and a
         stock option agreement on the form most recently approved by the Board
         of Directors, as qualified by this paragraph. All such performance
         stock options shall vest and become exercisable upon the grant date. To
         the extent permitted by law, any such stock options shall remain
         exercisable for a period of one hundred eighty (180) days commencing on
         your final date of employment with the Company (so long as such
         exercise period does not exceed the expiration date of such options,
         as stated in the stock option agreement subject to which such options
         may be granted).

                  For the purpose of determining the period for which the any of
         the aforementioned options may be exercised, the expiration date of
         such options shall be deemed to be the expiration date set forth in the
         relevant agreement governing such options but disregarding the
         provisions for early termination of the options for any reason other
         than termination for "cause" as defined in such option agreement. In
         addition, the one hundred eighty (180) day period commencing on your
         final date of employment with the Company shall supersede any provision
         in the relevant agreement governing such options setting forth an
         exercise period for the options of less than one hundred eighty (180)
         days after your final date of employment with the Company.

                  Pursuant to the terms of the Amended 1997 Employee, Director
         and Consultant Stock Option Plan, you will be permitted to exercise
         the options noted above by using a cashless exercise program.

                  All shares of the Company's stock owned by you shall be
         subject to any restrictions imposed by law, and, [__________________
         ___________________________________________________________].

--------------------
Portions of this Exhibit were omitted and have been filed separately with the
Secretary of the Commission pursuant to the Company's application requesting
confidential treatment under Rule 24b-2 of the Securities Exchange Act of
1934.

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NON-COMPETITION

         You hereby agree that the companies set forth on SCHEDULE A to this
Amended and Restated Retention Agreement, together with their respective
affiliates, successors and related entities, shall be the only entities to be
considered a Competing Business for purposes of Section 5 of the Employment
Agreement.

EXPENSES

         The Company shall reimburse you for up to $5,000 in legal fees
relating to the negotiation of this Retention Agreement, within thirty (30)
days following presentation of appropriate invoices to Martin Vogelbaum.

RELEASE AND WAIVER OF CLAIMS

         Your receipt of any cash, stock options or expense reimbursements
pursuant to the terms of the Retention Agreement is conditioned on your
execution of a full and complete release and waiver of claims with respect to
the Company, its directors, officers and shareholders (and its and their
successors and assigns) in a form satisfactory to (and provided by) the
Company upon the earlier of (i) [________________] or (ii) the date of the
termination of your employment with the Company for any reason. A current
example of a full and complete release is attached hereto as Exhibit A for
your review. Failure to execute and return such release and waiver of claims
to the Company within twenty-one (21) days of receipt, shall subject any
stock options granted hereunder to forfeiture and shall require you to repay
any cash payments provided hereunder upon the expiration of such twenty-one
(21) day period.

DISPUTE RESOLUTION

         To the extent that any disputes regarding this Retention Agreement
may arise, they shall be resolved in accordance with the terms of Section 10
of the Employment Agreement.

         We hope that you appreciate the unique nature of this arrangement
and we are pleased to recognize the important role we anticipate you will
play during the Retention Period. In order to accept this offer, you must
execute this letter where provided below and return it to Martin Vogelbaum,
by no later than November 15, 2001.


                                       VARIAGENICS, INC.

                                       By:  /s/ Martin A. Vogelbaum
                                          --------------------------------
                                          Martin A. Vogelbaum
                                          Director

ACCEPTED AND AGREED:

By:   /s/ Taylor J. Crouch
      --------------------
Date: 11/15/01
     --------------------

--------------------
Portions of this Exhibit were omitted and have been filed separately with the
Secretary of the Commission pursuant to the Company's application requesting
confidential treatment under Rule 24b-2 of the Securities Exchange Act of
1934.

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                                     RELEASE

         You hereby agree and acknowledge that by signing this Release, you
are waiving your right to assert any form of legal claim against Variagenics,
Inc. ("Variagenics" or the "Company")(1) whatsoever for any alleged action,
inaction or circumstance existing or arising from the beginning of time
through the date on which you sign this Release. Your waiver and release
herein is intended to bar any form of legal claim, charge, complaint or any
other form of action (jointly referred to as "Claims") against Variagenics
seeking any form of relief including, without limitation, equitable relief
(whether declaratory, injunctive or otherwise), the recovery of any damages
or any other form of monetary recovery whatsoever (including, without
limitation, back pay, front pay, compensatory damages, emotional distress
damages, punitive damages, attorneys fees and any other costs) against
Variagenics for any alleged action, inaction or circumstance existing or
arising through the date on which you sign this Release.

         Without limiting the foregoing general waiver and release, you
specifically waive and release Variagenics from any Claims arising from or
related to your employment relationship with the Company or the termination
thereof, including without limitation:

         (i)      Claims under any local, state, federal or foreign
                  discrimination, fair employment practices or other employment
                  related statute, regulation or executive order (as they may
                  have been amended through the date on which you sign this
                  Release) prohibiting discrimination or harassment based upon
                  any protected status including, without limitation, race,
                  religion, citizenship, national origin, age, gender, genetic
                  carrier status, marital status, disability, veteran status or
                  sexual orientation. Without limitation, specifically included
                  in this paragraph are any Claims arising under the federal Age
                  Discrimination in Employment Act, the Older Workers Benefit
                  Protection Act, the Civil Rights Acts of 1866 and 1871, Title
                  VII of the Civil Rights Act of 1964, the Civil Rights Act of
                  1991, the Equal Pay Act, the Immigration Reform and Control
                  Act, the Americans With Disabilities Act and any similar
                  local, state, federal or foreign statute or law.

         (ii)     Claims under any other local, state, federal or foreign
                  employment related statute, regulation or executive order (as
                  they may have been amended through the date on which you sign
                  this Release) relating to wages, hours or any other terms and


-------------------------------

(1)     For the purposes of this Section the parties agree that the phrase,
"Variagenics, Inc.," shall include Variagenics, Inc., its divisions,
affiliates, parents and subsidiaries, and its and their respective officers,
directors, employees, agents and assigns.

--------------------
Portions of this Exhibit were omitted and have been filed separately with the
Secretary of the Commission pursuant to the Company's application requesting
confidential treatment under Rule 24b-2 of the Securities Exchange Act of
1934.

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                  conditions of employment. Without limitation, specifically
                  included in this paragraph are any Claims arising under the
                  Fair Labor Standards Act, the Family and Medical Leave Act of
                  1993, the National Labor Relations Act, the Employee
                  Retirement Income Security Act of 1974, the Consolidated
                  Omnibus Budget Reconciliation Act of 1985 ("COBRA") and any
                  similar local, state, federal or foreign statute or law.

         (iii)    Claims under any local, state, federal or foreign common law
                  theory including, without limitation, wrongful discharge,
                  breach of express or implied contract, promissory estoppel,
                  unjust enrichment, breach of a covenant of good faith and fair
                  dealing, violation of public policy, defamation, interference
                  with contractual relations, intentional or negligent
                  infliction of emotional distress, invasion of privacy,
                  misrepresentation, deceit, fraud or negligence.

         (iv)     Claims under any local, state or federal securities law,
                  including, without limitation, the Securities Act of 1933, as
                  amended, the Securities Exchange Act of 1934, as amended, and
                  any Massachusetts, Delaware or other state or local securities
                  statutes and regulations.

         (v)      Any other Claim arising under local, state or federal law.

         You acknowledge and agree that but for providing this waiver and
release, you would not be receiving the consideration provided to you by the
Company through the Retention Agreement between you and the Company.

         Because you are more than forty (40) years of age, you have specific
rights under the Older Workers Benefits Protection Act ("OWBPA"), which
prohibits discrimination on the basis of age, and that the releases set forth
herein are intended to release any right that you may have to file a claim
against the Company alleging discrimination on the basis of age.

         It is the Company's desire and intent to make certain that you fully
understand the provisions and effects of this letter. To that end, you have
been encouraged and given the opportunity to consult with legal counsel for
the purpose of reviewing the terms of this Release. Consistent with the
provisions of OWBPA, your signature below confirms that the Company has
provided you with at least twenty-one (21) days in which to consider and
accept the terms of this

--------------------
Portions of this Exhibit were omitted and have been filed separately with the
Secretary of the Commission pursuant to the Company's application requesting
confidential treatment under Rule 24b-2 of the Securities Exchange Act of
1934.

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Release. In addition, you may rescind your assent to this Agreement if,
within seven (7) days after you sign this Agreement, you deliver a written
notice of rescission to the Company's Board of Directors. To be effective,
such rescission must be in writing and must be hand-delivered or post-marked
within the seven (7) day period and sent by certified mail to Variagenics in
care of Martin Vogelbaum.




Confirmed and Agreed:
                                       Variagenics, Inc.


__________________________________     By: _______________________________
Taylor J. Crouch

Dated: _____________________, 2002     Dated: ______________________, 2002

--------------------
Portions of this Exhibit were omitted and have been filed separately with the
Secretary of the Commission pursuant to the Company's application requesting
confidential treatment under Rule 24b-2 of the Securities Exchange Act of
1934.

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                                   Schedule A

                               COMPETING BUSINESSES

                                [________________]

                                    [_______]

                                    [_______]

                                [________________]

                                    [_______]

                                    [_______]

                                [________________]

                                    [_______]

                                    [_______]

                                    [_______]

                                    [_______]

--------------------
Portions of this Exhibit were omitted and have been filed separately with the
Secretary of the Commission pursuant to the Company's application requesting
confidential treatment under Rule 24b-2 of the Securities Exchange Act of
1934.

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