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                                                                 EXHIBIT 10.15



                                VARIAGENICS, INC.

                        2000 EMPLOYEE STOCK PURCHASE PLAN

         The following constitute the provisions of the 2000 Employee Stock
Purchase Plan (the "Plan") of Variagenics, Inc. (the "Company").

         1. PURPOSE. The purpose of the Plan is to provide Employees of the
Company and its Designated Subsidiaries with an opportunity to purchase Common
Stock of the Company. It is the intention of the Company to have the Plan
qualify as an "Employee Stock Purchase Plan" under Section 423 of the Internal
Revenue Code of 1986, as amended. The provisions of the Plan shall, accordingly,
be construed so as to extend and limit participation in a manner consistent with
the requirements of that section of the Code.

         2. DEFINITIONS.

         (a) "BOARD" shall mean the Board of Directors of the Company, or a
committee of the Board of Directors named by the Board to administer the Plan.

         (b) "CODE" shall mean the Internal Revenue Code of 1986, as amended.

         (c) "COMMON STOCK" shall mean the Common Stock, $.01 par value, of the
Company.

         (d) "COMPANY" shall mean Variagenics, Inc., a Delaware corporation.

         (e) "COMPENSATION" shall mean all compensation that is taxable income
for federal income tax purposes, including, payments for overtime, shift
premium, incentive compensation, incentive payments, bonuses, commissions and
other compensation.

         (f) "CONTINUOUS STATUS AS AN EMPLOYEE" shall mean the absence of any
interruption or termination of service as an Employee. Continuous Status as an
Employee shall not be considered interrupted in the case of a leave of absence
agreed to in writing by the Company, provided that such leave is for a period of
not more than 90 days or reemployment upon the expiration of such leave is
guaranteed by contract or statute.

         (g) "CONTRIBUTIONS" shall mean all amounts credited to the account of a
participant pursuant to the Plan.

         (h) "DESIGNATED SUBSIDIARIES" shall mean the Subsidiaries which have
been designated by the Board from time to time in its sole discretion as
eligible to participate in the Plan.

         (i) "EMPLOYEE" shall mean any person, including an officer, who is
customarily employed for at least 20 hours per week and more than five months in
a calendar year by the Company or one of its Designated Subsidiaries.

         (j) "EXERCISE DATE" shall mean the last day of each Offering Period of
the Plan.

         (k) "OFFERING DATE" shall mean the first business day of each Offering
Period of the Plan, except that in the case of an individual who becomes an
eligible Employee after the first business day of




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an Offering Period but on or prior to the first business day of the fourth
calendar month within such Offering Period, the term "Offering Date" shall mean
the first business day of such fourth calendar month coinciding with or next
succeeding the day on which that individual becomes an eligible Employee and
with respect to the first Offering Period, the term "Offering Date" shall mean
either the first business day of the Offering Period or October 1, 2000 as set
forth in Section 3(a) of the Plan .

         Options granted after the first business day of an Offering Period will
be subject to the same terms as the options granted on the first business day of
such Offering Period except that they will have a different grant date (thus,
potentially, a different exercise price) and, because they expire at the same
time as the options granted on the first business day of such Offering Period, a
shorter term.

         (l) "OFFERING PERIOD" shall mean a period of six months commencing on
January 31 and July 31 of each calendar year, other than the first Offering
Period as set forth in Section 4.

         (m) "PLAN" shall mean this Variagenics, Inc. 2000 Employee Stock
Purchase Plan.

         (n) "SUBSIDIARY" shall mean a corporation, domestic or foreign, of
which not less than 50% of the voting shares are held by the Company or a
Subsidiary, whether or not such corporation now exists or is hereafter organized
or acquired by the Company or a Subsidiary.

         3. ELIGIBILITY.

         (a) Any person who has been continuously employed as an Employee for
three (3) months as of the Offering Date of a given Offering Period shall be
eligible to participate in such Offering Period under the Plan, provided that
such person was not eligible to participate in such Offering Period as of any
prior Offering Date, and further, subject to the requirements of paragraph 5(a)
and the limitations imposed by Section 423(b) of the Code. Notwithstanding the
foregoing, any person who is employed as an Employee on the date of the
commencement of the first Offering Period shall be eligible to participate in
the first Offering Period under the Plan and any person who becomes employed as
an Employee before October 1, 2000 and was not previously eligible to
participate in such Offering Period, shall be eligible to participate in the
first Offering Period as of October 1, 2000.

         (b) Any provisions of the Plan to the contrary notwithstanding, no
Employee shall be granted an option under the Plan (i) if, immediately after the
grant, such Employee (or any other person whose stock would be attributed to
such Employee pursuant to Section 424(d) of the Code) would own stock and/or
hold outstanding options to purchase stock possessing five percent (5%) or more
of the total combined voting power or value of all classes of stock of the
Company or of any Subsidiary of the Company, (ii) which permits his or her
rights to purchase stock under all employee stock purchase plans (described in
Section 423 of the Code) of the Company and its Subsidiaries to accrue at a rate
which exceeds $25,000 of fair market value of such stock (determined at the time
such option is granted) for each calendar year in which such option is
outstanding at any time, or (iii) to purchase more than 2,000 shares of Common
Stock in any one Offering Period. Any option granted under the Plan shall be
deemed to be modified to the extent necessary to satisfy this paragraph (b).

         4. OFFERING PERIODS. The Plan shall be implemented by a series of
Offering Periods, with a new Offering Period commencing on January 31 and July
31 of each year (or at such other time or times as may be determined by the
Board of Directors). Notwithstanding the foregoing, the initial Offering Period
shall commence at a time to be determined by the Board and shall continue until
January 31, 2001. The Plan shall continue until terminated in accordance with
paragraph 19 hereof. The Board of Directors of the Company shall have the power
to change the duration and/or the frequency of Offering Periods


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with respect to future offerings without stockholder approval if such change is
announced at least 15 days prior to the scheduled beginning of the first
Offering Period to be affected.

         5. PARTICIPATION.

         (a) An eligible Employee may become a participant in the Plan by
completing an Enrollment Form provided by the Company and filing it with the
Company prior to the applicable Offering Date, unless a later time for filing
the Enrollment Form is set by the Board for all eligible Employees with respect
to a given Offering Period. The Enrollment Form and their submission may be
electronic, as directed by the Company. The Enrollment Form shall set forth the
percentage of the participant's Compensation (which shall be not less than 1%
and not more than 10%) to be paid as Contributions pursuant to the Plan.

         (b) Payroll deductions shall commence on the first payroll following
the Offering Date, unless a later time is set by the Board with respect to a
given Offering Period, and shall end on the last payroll paid on or prior to the
Exercise Date of the Offering Periods to which the Enrollment Form is
applicable, unless sooner terminated by the participant as provided in paragraph
10.

         6. METHOD OF PAYMENT OF CONTRIBUTIONS.

         (a) The participant shall elect to have payroll deductions made on each
payday during the Offering Period in an amount not less than 1% and not more
than 10% of such participant's Compensation on each such payday; provided that
the aggregate of such payroll deductions during the Offering Period shall not
exceed 10% of the participant's aggregate Compensation during said Offering
Period. All payroll deductions made by a participant shall be credited to his or
her account under the Plan. A participant may not make any additional payments
into such account.

         (b) A participant may discontinue his or her participation in the Plan
as provided in paragraph 10, or, on one occasion only during the Offering
Period, may decrease, but may not increase, the rate of his or her Contributions
during the Offering Period by completing and filing with the Company a new
Enrollment Form authorizing a change in the deduction rate. The change in rate
shall be effective as of the beginning of the next payroll period following the
date of the filing of such new Enrollment Form, if the Enrollment Form is
completed at least ten (10) business days prior to such date, and, if not, as of
the beginning of the next succeeding payroll period.

         (c) Notwithstanding the foregoing, to the extent necessary to comply
with Section 423(b)(8) of the Code and paragraph 3(b) hereof, a participant's
payroll deductions may be decreased to 0% at such time and for so long as the
aggregate of all payroll deductions accumulated with respect to the current
Offering Period and any other Offering Period ending within the current calendar
year equals $21,250. Payroll deductions shall recommence at the rate provided in
such participant's Enrollment Form at the beginning of the first Offering Period
which is scheduled to end in the following calendar year, unless terminated by
the participant as provided in paragraph 10.

         7. GRANT OF OPTION.

         (a) On the Offering Date of each Offering Period, each eligible
Employee participating in such Offering Period shall be granted an option to
purchase on the Exercise Date of such Offering Period a number of shares of the
Common Stock determined by dividing such Employee's Contributions accumulated
prior to such Exercise Date and retained in the participant's account as of the
Exercise Date by the lower of (i) 85% of the fair market value of a share of
Common Stock on the Offering Date, or (ii) 85% of the fair market value of a
share of the Common Stock on the Exercise Date; provided


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however, that such purchase shall be subject to the limitations set forth in
Sections 3(b) and 12 hereof. The fair market value of a share of the Common
Stock shall be determined as provided in Section 7(b) herein.

         (b) The option price per share of the shares offered in a given
Offering Period shall be the lower of (i) 85% of the fair market value of a
share of the Common Stock on the Offering Date, or (ii) 85% of the fair market
value of a share of the Common Stock on the Exercise Date. The fair market value
of the Common Stock on a given date shall be determined by the Board based on
the closing sale price of the Common Stock for such date (or, in the event that
the Common Stock is not traded on such date, on the immediately preceding
trading date), as reported by the National Association of Securities Dealers
Automated Quotation (Nasdaq) National Market or, if such price is not reported,
the mean of the bid and asked prices per share of the Common Stock as reported
by Nasdaq or, in the event the Common Stock is listed on a stock exchange, the
fair market value per share shall be the closing sale price on such exchange on
such date (or, in the event that the Common Stock is not traded on such date, on
the immediately preceding trading date), as reported in THE WALL STREET JOURNAL.
NOTWITHSTANDING THE FOREGOING, IF THE FIRST OFFERING DATE COINCIDES WITH THE
EFFECTIVE DATE OF A REGISTRATION STATEMENT ON FORM S-1 FOR THE INITIAL PUBLIC
OFFERING OF THE COMMON STOCK, THE FAIR MARKET VALUE OF A SHARE OF THE COMMON
STOCK SHALL BE THE PRICE TO THE PUBLIC AS SET FORTH IN THE FINAL PROSPECTUS
FILED WITH THE SECURITIES AND EXCHANGE COMMISSION PURSUANT TO RULE 424 UNDER THE
SECURITIES ACT OF 1933, AS AMENDED.

         8. EXERCISE OF OPTION. Unless a participant withdraws from the Plan as
provided in paragraph 10, his or her option for the purchase of shares will be
exercised automatically on the Exercise Date of the Offering Period, and the
maximum number of full shares subject to option will be purchased for him or her
at the applicable option price with the accumulated Contributions in his or her
account. If a fractional number of shares results, then such number shall be
rounded down to the next whole number and any unapplied cash shall be carried
forward to the next Exercise Date, unless the participant requests a cash
payment. The shares purchased upon exercise of an option hereunder shall be
deemed to be transferred to the participant on the Exercise Date. During a
participant's lifetime, a participant's option to purchase shares hereunder is
exercisable only by him or her.

         9. DELIVERY. Upon the written request of a participant, certificates
representing the shares purchased upon exercise of an option will be issued as
promptly as practicable after the Exercise Date of each Offering Period to
participants who wish to hold their shares in certificate form. Any cash
remaining in a participant's account under the Plan after a purchase by him or
her of shares at the termination of each Offering Period shall be carried
forward to the next Exercise Date unless the participant requests a cash
payment.

         10. WITHDRAWAL; TERMINATION OF EMPLOYMENT.

         (a) A participant may withdraw all but not less than all the
Contributions credited to his or her account under the Plan at any time prior to
the Exercise Date of the Offering Period by giving written notice to the
Company. All of the participant's Contributions credited to his or her account
will be paid to him or her promptly after receipt of his or her notice of
withdrawal and his or her option for the current period will be automatically
terminated, and no further Contributions for the purchase of shares will be made
during the Offering Period.

         (b) Upon termination of the participant's Continuous Status as an
Employee prior to the Exercise Date of the Offering Period for any reason,
including retirement or death, the Contributions credited to his or her account
will be returned to him or her or, in the case of his or her death, to the


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person or persons entitled thereto under paragraph 14 hereof, and his or her
option will be automatically terminated.

         (c) In the event an Employee fails to remain in Continuous Status as an
Employee for at least 20 hours per week during the Offering Period in which the
Employee is a participant, he or she will be deemed to have elected to withdraw
from the Plan and the Contributions credited to his or her account will be
returned to him or her and his or her option terminated.

         (d) A participant's withdrawal from an Offering Period will not have
any effect upon his or her eligibility to participate in a succeeding offering
or in any similar plan which may hereafter be adopted by the Company.

         11. INTEREST. No interest shall accrue on the Contributions of a
participant in the Plan.

         12. STOCK.

         (a) The maximum number of shares of Common Stock which shall be made
available for sale under the Plan shall be 400,000 shares, subject to adjustment
upon changes in capitalization of the Company as provided in paragraph 18. If
the total number of shares which would otherwise be subject to options granted
pursuant to Section 7(a) hereof on the Offering Date of an Offering Period
exceeds the number of shares then available under the Plan (after deduction of
all shares for which options have been exercised or are then outstanding), the
Company shall make a pro rata allocation of the shares remaining available for
option grants in as uniform a manner as shall be practicable and as it shall
determine to be equitable. Any amounts remaining in an Employee's account not
applied to the purchase of stock pursuant to this Section 12 shall be refunded
on or promptly after the Exercise Date. In such event, the Company shall give
written notice of such reduction of the number of shares subject to the option
to each Employee affected thereby and shall similarly reduce the rate of
Contributions, if necessary.

         (b) The participant will have no interest or voting right in shares
covered by his or her option until such option has been exercised.

         13. ADMINISTRATION. The Board shall supervise and administer the Plan
and shall have full power to adopt, amend and rescind any rules deemed desirable
and appropriate for the administration of the Plan and not inconsistent with the
Plan, to construe and interpret the Plan, and to make all other determinations
necessary or advisable for the administration of the Plan.

         14. DESIGNATION OF BENEFICIARY.

         (a) A participant may file a written designation of a beneficiary who
is to receive any shares and cash, if any, from the participant's account under
the Plan in the event of such participant's death subsequent to the end of the
Offering Period but prior to delivery to him or her of such shares and cash. In
addition, a participant may file a written designation of a beneficiary who is
to receive any cash from the participant's account under the Plan in the event
of such participant's death prior to the Exercise Date of the Offering Period.
If a participant is married and the designated beneficiary is not the spouse,
spousal consent shall be required for such designation to be effective.

         (b) Such designation of beneficiary may be changed by the participant
(and his or her spouse, if any) at any time by written notice. In the event of
the death of a participant and in the absence of a beneficiary validly
designated under the Plan who is living at the time of such participant's death,
the Company shall deliver such shares and/or cash to the executor or
administrator of the estate of the participant, or if no such executor or
administrator has been appointed (to the knowledge of the


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Company), the Company, in its discretion, may deliver such shares and/or cash to
the spouse or to any one or more dependents or relatives of the participant, or
if no spouse, dependent or relative is known to the Company, then to such other
person as the Company may designate.

         15. TRANSFERABILITY. Neither Contributions credited to a participant's
account nor any rights with regard to the exercise of an option or to receive
shares under the Plan may be assigned, transferred, pledged or otherwise
disposed of in any way (other than by will, the laws of descent and distribution
or as provided in paragraph 14 hereof) by the participant. Any such attempt at
assignment, transfer, pledge or other disposition shall be without effect,
except that the Company may treat such act as an election to withdraw funds in
accordance with paragraph 10 hereof.

         16. USE OF FUNDS. All Contributions received or held by the Company
under the Plan may be used by the Company for any corporate purpose, and the
Company shall not be obligated to segregate such Contributions.

         17. REPORTS. Individual accounts will be maintained for each
participant in the Plan. Statements of account will be given to participating
Employees promptly following the Exercise Date, which statements will set forth
the amounts of Contributions, the per share purchase price, the number of shares
purchased and the remaining cash balance, if any.

         18. ADJUSTMENTS UPON CHANGES IN CAPITALIZATION. Subject to any required
action by the stockholders of the Company, the number of shares of Common Stock
covered by unexercised options under the Plan and the number of shares of Common
Stock which have been authorized for issuance under the Plan but are not yet
subject to options (collectively, the "Reserves"), the maximum number of shares
of Common Stock that may be purchased by a Participant in an Offering Period, as
well as the price per share of Common Stock covered by each unexercised option
under the Plan, shall be proportionately adjusted for any increase or decrease
in the number of issued shares of Common Stock resulting from a stock split,
reverse stock split, stock dividend, combination or reclassification of the
Common Stock, or any other increase or decrease in the number of shares of
Common Stock effected without receipt of consideration by the Company; provided,
however, that conversion of any convertible securities of the Company shall not
be deemed to have been "effected without receipt of consideration." Such
adjustment shall be made by the Board, whose determination in that respect shall
be final, binding and conclusive. Except as expressly provided herein, no issue
by the Company of shares of stock of any class, or securities convertible into
shares of stock of any class, shall affect, and no adjustment by reason thereof
shall be made with respect to, the number or price of shares of Common Stock
subject to an option.

         In the event of the proposed dissolution or liquidation of the Company,
an Offering Period then in progress will terminate immediately prior to the
consummation of such proposed action, unless otherwise provided by the Board. In
the event of a proposed sale of all or substantially all of the assets of the
Company, or the merger of the Company with or into another corporation, each
option outstanding under the Plan shall be assumed or an equivalent option shall
be substituted by such successor corporation or a parent or subsidiary of such
successor corporation, unless the Board determines, in the exercise of its sole
discretion and in lieu of such assumption or substitution, to shorten the
Offering Period then in progress by setting a new Exercise Date (the "New
Exercise Date"). If the Board shortens the Offering Period then in progress in
lieu of assumption or substitution in the event of a merger or sale of assets,
the Board shall notify each participant in writing, at least ten days prior to
the New Exercise Date, that the Exercise Date for his or her option has been
changed to the New Exercise Date and that his or her option will be exercised
automatically on the New Exercise Date, unless prior to such date he or she has
withdrawn from the Offering Period as provided in paragraph 10 hereof. For
purposes of this paragraph, an option granted under the Plan shall be deemed to
be assumed if, following the sale of assets or merger, the option confers


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the right to purchase, for each share of Common Stock subject to the option
immediately prior to the sale of assets or merger, the consideration (whether
stock, cash or other securities or property) received in the sale of assets or
merger by holders of Common Stock for each share of Common Stock held on the
effective date of the transaction (and if such holders were offered a choice of
consideration, the type of consideration chosen by the holders of a majority of
the outstanding shares of Common Stock); provided, however, that if such
consideration received in the sale of assets or merger was not solely common
stock of the successor corporation or its parent (as defined in Section 424(e)
of the Code), the Board may, with the consent of the successor corporation,
provide for the consideration to be received upon exercise of the option to be
solely common stock of the successor corporation or its parent equal in fair
market value to the per share consideration received by holders of Common Stock
in the sale of assets or merger.

         The Board may, if it so determines in the exercise of its sole
discretion, also make provision for adjusting the Reserves, as well as the price
per share of Common Stock covered by each outstanding option, in the event that
the Company effects one or more reorganizations, recapitalizations, rights
offerings or other increases or reductions of shares of its outstanding Common
Stock, and in the event of the Company being consolidated with or merged into
any other corporation.

         19. AMENDMENT OR TERMINATION. The Board may at any time terminate or
amend the Plan. Except as provided in paragraph 18 hereof, no such termination
may affect options previously granted, nor may an amendment make any change in
any option theretofore granted which adversely affects the rights of any
participant. In addition, to the extent necessary to comply with Section 423 of
the Code (or any successor rule or provision or any applicable law or
regulation), the Company shall obtain stockholder approval in such a manner and
to such a degree as so required.

         20. NOTICES. All notices or other communications by a participant to
the Company under or in connection with the Plan shall be deemed to have been
duly given when received in the form specified by the Company at the location,
or by the person, designated by the Company for the receipt thereof.

         21. CONDITIONS UPON ISSUANCE OF SHARES. Shares shall not be issued with
respect to an option unless the exercise of such option and the issuance and
delivery of such shares pursuant thereto shall comply with all applicable
provisions of law, domestic or foreign, including, without limitation, the
Securities Act of 1933, as amended, the Securities Exchange Act of 1934, as
amended, the rules and regulations promulgated thereunder, and the requirements
of any stock exchange upon which the shares may then be listed, and shall be
further subject to the approval of counsel for the Company with respect to such
compliance.

         As a condition to the exercise of an option, the Company may require
the person exercising such option to represent and warrant at the time of any
such exercise that the shares are being purchased only for investment and
without any present intention to sell or distribute such shares if, in the
opinion of counsel for the Company, such a representation is required by any of
the aforementioned applicable provisions of law.

         22. RIGHT TO TERMINATE EMPLOYMENT. Nothing in the Plan or in any
agreement entered into pursuant to the Plan shall confer upon any Employee or
other optionee the right to continue in the employment of the Company or any
Subsidiary, or affect any right which the Company or any Subsidiary may have to
terminate the employment of such Employee or other optionee.

         23. RIGHTS AS A STOCKHOLDER. Neither the granting of an option nor a
deduction from payroll shall constitute an Employee the owner of shares covered
by an option. No optionee shall have any right as a stockholder unless and until
an option has been exercised, and the shares underlying the option have been
registered in the Company's share register.


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         24. TERM OF PLAN. The Plan became effective upon its adoption by the
Board of Directors on May 15, 2000 and shall continue in effect for a term of
ten years unless sooner terminated under paragraph 19 hereof.

         25. APPLICABLE LAW. This Plan shall be governed in accordance with the
laws of the State of Delaware, applied without giving effect to any
conflict-of-law principles.


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