Document:

<Page>

                                                                   EXHIBIT 10.16

As amended through December 17, 2002 and adjusted for stock splits in April and
October 2000

                        MILLENNIUM PHARMACEUTICALS, INC.

                           1996 EQUITY INCENTIVE PLAN

1.   PURPOSE.

     The purpose of this plan (the "Plan") is to secure for Millennium
Pharmaceuticals, Inc. (the "Company") and its shareholders the benefits arising
from capital stock ownership by employees, officers and directors of, and
consultants or advisors to, the Company and its parent and subsidiary
corporations who are expected to contribute to the Company's future growth and
success. Except where the context otherwise requires, the term "Company" shall
include the parent and all present and future subsidiaries of the Company as
defined in Sections 424(e) and 424(f) of the Internal Revenue Code of 1986, as
amended or replaced from time to time (the "Code").

2.   TYPE OF OPTIONS AND AWARDS; ADMINISTRATION.

     (a)  TYPES OF OPTIONS AND AWARDS. Options granted pursuant to the Plan
shall be authorized by action of the Board of Directors of the Company (or a
Committee designated by the Board of Directors) and may be either incentive
stock options ("Incentive Stock Options") meeting the requirements of Section
422 of the Code or non-statutory options which are not intended to meet the
requirements of Section 422 of the Code. Awards granted pursuant to the Plan
shall be authorized by action of the Board of Directors of the Company (or a
Committee designated by the Board of Directors) and shall meet the requirements
of Section 13 of the Plan.

     (b)  ADMINISTRATION. The Plan will be administered by the Board of
Directors of the Company, whose construction and interpretation of the terms and
provisions of the Plan shall be final and conclusive. The Board of Directors may
in its sole discretion (i) grant options to purchase shares of the Company's
Common Stock (as defined in Section 4 of the Plan), and issue shares upon
exercise of such options as provided in the Plan and (ii) make awards for the
purchase of shares of Common Stock pursuant to Section 13 of the Plan. The Board
shall have authority, subject to the express provisions of the Plan, to construe
the respective option agreements, awards and the Plan, to prescribe, amend and
rescind rules and regulations relating to the Plan, to determine the terms and
provisions of the respective option agreements and awards, which need not be
identical, and to make all other determinations in the judgment of the Board of
Directors necessary or desirable for the administration of the Plan. The Board
of Directors may correct any defect or supply any omission or reconcile any
inconsistency in the Plan or in any option agreement or award in the manner and
to the extent it shall deem expedient to carry the Plan into effect and it shall
be the sole and final judge of such expediency. No director or person acting
pursuant to authority delegated by the Board of Directors shall be liable for

<Page>

any action or determination made in good faith. The Board of Directors may, to
the full extent permitted by or consistent with applicable laws or regulations
(including, without limitation, applicable state law and Rule 16b-3 promulgated
under the Securities Exchange Act of 1934 (the "Exchange Act"), or any successor
rule ("Rule 16b-3")), delegate any or all of its powers under the Plan to a
committee (the "Committee") appointed by the Board of Directors, and if the
Committee is so appointed all references to the Board of Directors in the Plan
shall mean and relate to such Committee to the extent authority is so delegated
to such Committee.

     (c)  APPLICABILITY OF RULE 16b-3. Those provisions of the Plan which make
express reference to Rule 16b-3 shall apply only to such persons as are required
to file reports under Section 16(a) of the Exchange Act (a "Reporting Person").

3.   ELIGIBILITY.

     (a)  GENERAL. Options and awards may be granted or made to persons who are,
at the time of grant, employees, officers or directors (so long as such officers
and directors are also employees) of, or consultants or advisors to, the
Company; PROVIDED, that the class of individuals to whom Incentive Stock Options
may be granted shall be limited to all employees of the Company; and PROVIDED
FURTHER that non-employee directors of the Company are not eligible to receive
options or awards of restricted stock under the Plan. A person who has been
granted an option or award may, if he or she is otherwise eligible, be granted
additional options or awards if the Board of Directors shall so determine.
Subject to adjustment as provided in Section 16 below, the maximum number of
shares with respect to which options or restricted stock awards may be granted
to any person under the Plan shall not exceed 300,000 shares of Common Stock
during any calendar year during the term of the Plan. For the purpose of
calculating such maximum number, (a) an option or award shall continue to be
treated as outstanding notwithstanding its repricing, cancellation or expiration
and (b) the repricing of an outstanding option or award or the issuance of a new
option or award in substitution for a cancelled option or award shall be deemed
to constitute the grant of a new additional option or award, as the case may be,
separate from the original grant that is repriced or cancelled.

     (b)  GRANT OF OPTIONS TO DIRECTORS AND OFFICERS. The selection of a
director or an officer (as the terms "director" and "officer" are defined for
purposes of Rule 16b-3) as a participant, the timing of the option grant or
award, the exercise price of the option or the sale price of the award and the
number of shares for which an option or award may be granted to such director or
officer shall be determined either (i) by the Board of Directors, of which all
members shall be "disinterested persons" (as hereinafter defined), or (ii) by a
committee of two or more directors having full authority to act in the matter,
of which all members shall be "disinterested persons." For the purposes of the
Plan, a director shall be deemed to be "disinterested" only if such person
qualifies as a "disinterested person" within the meaning of Rule 16b-3, as such
term is interpreted from time to time.

                                       -2-
<Page>

4.   STOCK SUBJECT TO PLAN.

     Subject to adjustment as provided in Section 16 below, the total number of
shares which may be issued and sold under the Plan is 22,400,000 shares of
Common Stock, $.001 par value per share ("Common Stock"). If an option granted
under the Plan shall expire or terminate for any reason without having been
exercised in full, the unpurchased shares subject to such option shall again be
available for subsequent option grants or awards under the Plan.

5.   FORMS OF OPTION AGREEMENTS.

     As a condition to the grant of an option under the Plan, each recipient of
an option shall execute an option agreement in such form not inconsistent with
the Plan as may be approved by the Board of Directors. Such option agreements
may differ among recipients.

6.   PURCHASE PRICE UPON EXERCISE OF OPTIONS.

     (a)  GENERAL. The purchase price per share of Common Stock deliverable upon
the exercise of an option shall be determined by the Board of Directors,
PROVIDED, HOWEVER, that in the case of an Incentive Stock Option, the exercise
price shall not be less than 100% of the fair market value of such stock, as
determined by the Board of Directors, at the time of grant of such option, or
less than 110% of such fair market value in the case of options described in
Section 11(b).

     (b)  PAYMENT OF PURCHASE PRICE. Options granted under the Plan may provide
for the payment of the exercise price by delivery of cash or a check to the
order of the Company in an amount equal to the exercise price of such options,
or, to the extent provided in the applicable option agreement, (i) by delivery
to the Company of shares of Common Stock of the Company already owned by the
optionee having a fair market value equal in amount to the exercise price of the
options being exercised, (ii) by any other means (including without limitation
by delivery of a promissory note of the optionee payable on such terms as are
specified by the Board of Directors) which the Board of Directors determines are
consistent with the purpose of the Plan and with applicable laws and regulations
(including, without limitation, the provisions of Rule 16b-3 and Regulation T
promulgated by the Federal Reserve Board) or (iii) by any combination of such
methods of payment. The fair market value of any shares of the Company's Common
Stock or other non-cash consideration which may be delivered upon exercise of an
option shall be determined in such manner as may be prescribed by the Board of
Directors.

7.   OPTION PERIOD.

     Each option and all rights thereunder shall expire on such date as shall be
set forth in the applicable option agreement, except that such date, in the case
of an Incentive

                                       -3-
<Page>

Stock Option, shall in no case be later than ten years after the date on which
the option is granted.

8.   EXERCISE OF OPTIONS.

     Each option granted under the Plan shall be exercisable either in full or
in installments at such time or times and during such period as shall be set
forth in the agreement evidencing such option, subject to the provisions of the
Plan.

9.   NONTRANSFERABILITY OF OPTIONS.

     Incentive Stock Options, and all options granted to Reporting Persons,
shall not be assignable or transferable by the person to whom it is granted,
either voluntarily or by operation of law, except by will or the laws of descent
and distribution, and, during the life of the optionee, shall be exercisable
only by the optionee; provided, however, that non-statutory options granted to
Reporting Persons may be transferred pursuant to a qualified domestic relations
order (as defined in Rule 16b-3).

10.  EFFECT OF TERMINATION OF EMPLOYMENT OR OTHER RELATIONSHIP.

     The Board of Directors shall determine the period of time during which an
optionee may exercise an option following (i) the termination of the optionee's
employment or other relationship with the Company or (ii) the death or
disability of the optionee. Such periods shall be set forth in the agreement
evidencing such option.

11.  INCENTIVE STOCK OPTIONS.

     Options granted under the Plan which are intended to be Incentive Stock
Options shall be subject to the following additional terms and conditions:

     (a)  EXPRESS DESIGNATION. All Incentive Stock Options granted under the
Plan shall, at the time of grant, be specifically designated as such in the
option agreement covering such Incentive Stock Options.

     (b)  10% SHAREHOLDER. If any employee to whom an Incentive Stock Option is
to be granted under the Plan is, at the time of the grant of such option, the
owner of stock possessing more than 10% of the total combined voting power of
all classes of stock of the Company (after taking into account the attribution
of stock ownership rules of Section 424(d) of the Code), then the following
special provisions shall be applicable to the Incentive Stock Option granted to
such individual:

          (i)    The purchase price per share of the Common Stock subject to
such Incentive Stock Option shall not be less than 110% of the fair market value
of one share of Common Stock at the time of grant; and

                                       -4-
<Page>

          (ii)   The option exercise period shall not exceed five years from the
date of grant.

     (c)  DOLLAR LIMITATION. For so long as the Code shall so provide, options
granted to any employee under the Plan (and any other incentive stock option
plans of the Company) which are intended to constitute Incentive Stock Options
shall not constitute Incentive Stock Options to the extent that such options, in
the aggregate, become exercisable for the first time in any one calendar year
for shares of Common Stock with an aggregate fair market value (determined as of
the respective date or dates of grant) of more than $100,000.

     (d)  TERMINATION OF EMPLOYMENT, DEATH OR DISABILITY. No Incentive Stock
Option may be exercised unless, at the time of such exercise, the optionee is,
and has been continuously since the date of grant of his or her option, employed
by the Company, except that:

          (i)    an Incentive Stock Option may be exercised within the period of
three months after the date the optionee ceases to be an employee of the Company
(or within such lesser period as may be specified in the applicable option
agreement), PROVIDED, that the agreement with respect to such option may
designate a longer exercise period and that the exercise after such three-month
period shall be treated as the exercise of a non-statutory option under the
Plan;

          (ii)   if the optionee dies while in the employ of the Company, or
within three months after the optionee ceases to be such an employee, the
Incentive Stock Option may be exercised, by the person to whom it is transferred
by will or the laws of descent and distribution, within the period of one year
after the date of death (or within such lesser period as may be specified in the
applicable option agreement); and

          (iii)  if the optionee becomes disabled (within the meaning of Section
22(e)(3) of the Code or any successor provision thereto) while in the employ of
the Company, the Incentive Stock Option may be exercised within the period of
one year after the date the optionee ceases to be such an employee because of
such disability (or within such lesser period as may be specified in the
applicable option agreement).

For all purposes of the Plan and any option or award granted hereunder,
"employment" shall be defined in accordance with the provisions of Section
1.421-7(h) of the Income Tax Regulations (or any successor regulations).
Notwithstanding the foregoing provisions, no stock option may be exercised after
its expiration date.

12.  ADDITIONAL PROVISIONS.

     (a)  ADDITIONAL OPTION PROVISIONS. The Board of Directors may, in its sole
discretion, include additional provisions in any option granted under the Plan,
including without limitation restrictions on transfer, repurchase rights,
commitments to pay cash bonuses, to make, arrange for or guaranty loans or to
transfer other property to optionees

                                       -5-
<Page>

upon exercise of options, or such other provisions as shall be determined by the
Board of Directors; PROVIDED THAT such additional provisions shall not be
inconsistent with any other term or condition of the Plan.

     (b)  ACCELERATION, EXTENSION, ETC. The Board of Directors may, in its sole
discretion, (i) accelerate the date or dates on which all or any particular
option or options granted under the Plan may be exercised or (ii) extend the
dates during which all or any particular option or options granted under the
Plan may be exercised; provided, however, that no such extension shall be
permitted if it would cause the Plan to fail to comply with Section 422 of the
Code or with Rule 16b-3.

13.  AWARDS.

     A restricted stock award (an "award") shall consist of the sale and
issuance by the Company of shares of Common Stock, and the purchase by the
recipient of such shares, subject to the terms, conditions and restrictions
described in the document evidencing the award and in this Section 13 and
elsewhere in the Plan.

     (a)  EXECUTION OF RESTRICTED STOCK AWARD AGREEMENT. As a condition to an
award under the Plan, each recipient of an award shall execute an agreement in
such form, which may differ among recipients, as shall be specified by the Board
of Directors at the time of such award.

     (b)  PRICE. The Board of Directors shall determine the price at which
shares of Common Stock shall be sold to recipients of awards under the Plan. The
Board of Directors may, in its discretion, issue shares pursuant to awards
without the payment of any cash purchase price by the recipients or issue shares
pursuant to awards at a purchase price below the then fair market value of the
Common Stock. If a purchase price is required to be paid, it shall be paid in
cash or by check payable to the order of the Company at the time that the award
is accepted by the recipient, or by such other means as may be approved by the
Board of Directors.

     (c)  NUMBER OF SHARES. The award shall specify the number of shares of
Common Stock granted thereunder.

     (d)  RESTRICTIONS ON TRANSFER. In addition to such other terms, conditions
and restrictions upon awards as shall be imposed by the Board of Directors, all
shares issued pursuant to an award shall be subject to the following
restrictions:

          (1)    All shares of Common Stock subject to an award (including any
shares issued pursuant to paragraph (e) of this Section) shall be subject to
certain restrictions on disposition and obligations of resale to the Company as
provided in subparagraph (2) below for the period specified in the document
evidencing the award, and shall not be sold, assigned, transferred, pledged,
hypothecated or otherwise disposed of until such restrictions lapse. The period
during which such restrictions are applicable is referred to as the "Restricted
Period."

                                       -6-
<Page>

          (2)    In the event that a recipient's employment with the Company (or
consultancy or advisory relationship, as the case may be) is terminated within
the Restricted Period, whether such termination is voluntary or involuntary,
with or without cause, or because of the death or disability of the recipient,
the Company shall have the right and option for a period of three months
following such termination to buy for cash that number of the shares of Common
Stock purchased under the award as to which the restrictions on transfer and the
forfeiture provisions contained in the award have not then lapsed, at a price
equal to the price per share originally paid by the recipient. If such
termination occurs within the last three months of the applicable restrictions,
the restrictions and repurchase rights of the Company shall continue to apply
until the expiration of the Company's three month option period.

          (3)    Notwithstanding subparagraphs (1) and (2) above, the Board of
Directors may, in its discretion, either at the time that an award is made or at
any time thereafter, waive its right to repurchase shares of Common Stock upon
the occurrence of any of the events described in this paragraph (d) or remove or
modify any part or all of the restrictions. In addition, the Board of Directors
may, in its discretion, impose upon the recipient of an award at the time of
such award such other restrictions on any shares of Common Stock issued pursuant
to such award as the Board of Directors may deem advisable.

     (e)  ADDITIONAL SHARES. Any shares received by a recipient of an award as a
stock dividend on, or as a result of stock splits, combinations, exchanges of
shares, reorganizations, mergers, consolidations or otherwise with respect to,
shares of Common Stock received pursuant to such award shall have the same
status and shall bear the same restrictions, all on a proportionate basis, as
the shares initially purchased pursuant to such award.

     (f)  TRANSFERS IN BREACH OF AWARD. If any transfer of shares purchased
pursuant to an award is made or attempted contrary to the terms of the Plan and
of such award, the Board of Directors shall have the right to purchase for the
account of the Company those shares from the owner thereof or his or her
transferee at any time before or after the transfer at the price paid for such
shares by the person to whom they were awarded under the Plan. In addition to
any other legal or equitable remedies which it may have, the Company may enforce
its rights by specific performance to the extent permitted by law. The Company
may refuse for any purpose to recognize as a shareholder of the Company any
transferee who receives any shares contrary to the provisions of the Plan and
the applicable award or any recipient of an award who breaches his or her
obligation to resell shares as required by the provisions of the Plan and the
applicable award, and the Company may retain and/or recover all dividends on
such shares which were paid or payable subsequent to the date on which the
prohibited transfer or breach was made or attempted.

     (g)  ADDITIONAL AWARD PROVISIONS. The Board of Directors may, in its sole
discretion, include additional provisions in any award granted under the Plan,
including

                                       -7-
<Page>

without limitation commitments to pay cash bonuses, make, arrange for or
guarantee loans or transfer other property to recipients upon the grant of
awards, or such other provisions as shall be determined by the Board of
Directors.

14.  GENERAL RESTRICTIONS.

     (a)  INVESTMENT REPRESENTATIONS. The Company may require any person to whom
an option or award is granted, as a condition of exercising such option or
purchasing the shares subject to the award, to give written assurances in
substance and form satisfactory to the Company to the effect that such person is
acquiring the Common Stock subject to the option or award for his or her own
account for investment and not with any present intention of selling or
otherwise distributing the same, and to such other effects as the Company deems
necessary or appropriate in order to comply with federal and applicable state
securities laws.

     (b)  COMPLIANCE WITH SECURITIES LAWS. Each option and award shall be
subject to the requirement that if, at any time, counsel to the Company shall
determine that the listing, registration or qualification of the shares subject
to such option or award upon any securities exchange or under any state or
federal law, or the consent or approval of any governmental or regulatory body,
or that the disclosure of non-public information or the satisfaction of any
other condition is necessary as a condition of, or in connection with, the
issuance or purchase of shares thereunder, such option or award may not be
exercised, in whole or in part, unless such listing, registration,
qualification, consent or approval, or satisfaction of such condition shall have
been effected or obtained on conditions acceptable to the Board of Directors.
Nothing herein shall be deemed to require the Company to apply for or to obtain
such listing, registration or qualification, or to satisfy such condition.

15.  RIGHTS AS A SHAREHOLDER.

     The holder of an option or recipient of an award shall have no rights as a
shareholder with respect to any shares covered by the option or award
(including, without limitation, any rights to receive dividends or non-cash
distributions with respect to such shares) until the date of issue of a stock
certificate to him or her for such shares. No adjustment shall be made for
dividends or other rights for which the record date is prior to the date such
stock certificate is issued.

16.  ADJUSTMENT PROVISIONS FOR RECAPITALIZATIONS AND RELATED TRANSACTIONS.

     (a)  GENERAL. If, through or as a result of any merger, consolidation, sale
of all or substantially all of the assets of the Company, reorganization,
recapitalization, reclassification, stock dividend, stock split, reverse stock
split or other similar transaction, (i) the outstanding shares of Common Stock
are increased or decreased or are exchanged for a different number or kind of
shares or other securities of the Company, or (ii) additional shares or new or
different shares or other securities of the Company or other non-cash assets are
distributed with respect to such shares of Common Stock or other

                                       -8-
<Page>

securities, an appropriate and proportionate adjustment shall be made in (x) the
maximum number and kind of shares reserved for issuance under the Plan, (y) the
number and kind of shares or other securities subject to then outstanding
options under the Plan, and (z) the price for each share subject to any then
outstanding options under the Plan or repurchase rights of the Company, without
changing the aggregate purchase price as to which such options remain
exercisable, provided that no adjustment shall be made pursuant to this Section
16 if such adjustment would cause the Plan to fail to comply with Section 422 of
the Code or with Rule 16b-3.

     (b)  BOARD AUTHORITY TO MAKE ADJUSTMENTS. Any adjustments under this
Section 16 will be made by the Board of Directors, whose determination as to
what adjustments, if any, will be made and the extent thereof will be final,
binding and conclusive. No fractional shares will be issued under the Plan on
account of any such adjustments.

17.  MERGER, CONSOLIDATION, ASSET SALE, LIQUIDATION, ETC.

     (a)  GENERAL. In the event of a consolidation or merger in which
outstanding shares of Common Stock are exchanged for securities, cash or other
property of any other corporation or business entity or in the event of a
liquidation of the Company or sale of all or substantially all of the assets of
the Company, the Board of Directors of the Company, or the board of directors of
any corporation assuming the obligations of the Company, may, in its discretion,
take any one or more of the following actions, as to outstanding options and
awards: (i) provide that such options shall be assumed, or equivalent options
shall be substituted, by the acquiring or succeeding corporation (or an
affiliate thereof), PROVIDED that any such options substituted for Incentive
Stock Options shall meet the requirements of Section 424(a) of the Code, (ii)
upon written notice to the optionees, provide that all unexercised options will
terminate immediately prior to the consummation of such transaction unless
exercised by the optionee within a specified period following the date of such
notice, (iii) in the event of a merger under the terms of which holders of the
Common Stock of the Company will receive upon consummation thereof a cash
payment for each share surrendered in the merger (the "Merger Price"), make or
provide for a cash payment to the optionees equal to the difference between (A)
the Merger Price times the number of shares of Common Stock subject to such
outstanding options (to the extent then exercisable at prices not in excess of
the Merger Price) and (B) the aggregate exercise price of all such outstanding
options in exchange for the termination of such options, and (iv) provide that
all or any outstanding options shall become exercisable in full, any
restrictions on exercising outstanding options issued pursuant to the Plan prior
to any given date shall terminate and any restrictions on and rights of the
Company to repurchase shares covered by outstanding awards issued pursuant to
the Plan shall terminate.

     (b)  SUBSTITUTE OPTIONS. The Company may grant options under the Plan in
substitution for options held by employees of another corporation who become
employees of the Company, or a subsidiary of the Company, as the result of a
merger or consolidation of the employing corporation with the Company or a
subsidiary of the

                                       -9-
<Page>

Company, or as a result of the acquisition by the Company, or one of its
subsidiaries, of property or stock of the employing corporation. The Company may
direct that substitute options be granted on such terms and conditions as the
Board of Directors considers appropriate in the circumstances.

17A. CHANGE OF CONTROL.

     (a)  Change of Control occurs:

          (i)    when a person, entity or group (within the meaning of Section
13(d)(3) or 14(d)(2) of the Securities Exchange Act of 1934) acquires beneficial
ownership of the Company's capital stock equal to 50% or more of either (i) the
then-outstanding shares of the Company's common stock or (ii) the combined
voting power of the Company's then-outstanding securities to vote generally in
the election of directors;

          (ii)   upon the consummation by the Company of (i) a reorganization,
merger or consolidation, provided that, in each case, the persons who were the
Company's stockholders immediately prior to the reorganization, merger or
consolidation do not, immediately after, own more than 50% of the combined
voting power entitled to vote generally in the election of directors of the
reorganized, merged or consolidated company's then outstanding voting
securities, or (ii) a liquidation or dissolution of the Company or the sale of
all or substantially all of the Company's assets; or

          (iii)  when the Continuing Directors (as defined below) do not
constitute a majority of the Board of Directors (or, if applicable, the Board of
Directors of a successor corporation to the Company), where the term "Continuing
Director" means at any date a member of the Board of Directors (x) who was a
member of the Board of Directors on the date of the initial adoption of this
provision by the Board of Directors or (y) who was nominated or elected
subsequent to such date by at least a majority of the directors who were
Continuing Directors at the time of such nomination or election or whose
election to the Board of Directors was recommended or endorsed by at least a
majority of the directors who were Continuing Directors at the time of such
nomination or election. But, any individual whose initial assumption of office
occurred as a result of an actual or threatened election contest with respect to
the election or removal of directors or other actual or threatened solicitation
of proxies or consents, by or on behalf of a person other than the Board of
Directors, is excluded from clause (iii)(y) above.

     (b)  Notwithstanding any provision to the contrary in this Plan, if a
holder of an option or an award (a "Participant") voluntarily terminates his or
her employment with the Company for Good Reason or if the Company terminates the
Participant's employment without Cause during the period one month before
through twelve months after the date of a Change in Control, then, on the
Participant's termination date:

          (i)    all of the Participant's outstanding options and awards will
immediately vest in full and will remain exercisable until the earlier of (a)
the first

                                      -10-
<Page>

anniversary of the Participant's termination of employment or (b) the end of the
term of the option or award; and

          (ii)   any reacquisition or repurchase rights held by the Company with
respect to any of the Participant's options and awards will lapse.

     (c)  For purposes of this Section only:

          CAUSE means (1) the Participant's willful and continued failure to
substantially perform the Participant's material responsibilities to the Company
(except if the failure results from the Participant's incapacity caused by
physical or mental illness or disability); (2) the Participant's conviction of a
felony involving moral turpitude; or (3) the Participant's willful conduct which
materially injures the business of the Company, monetarily or otherwise. If a
Participant acts, or fails to act, in good faith and with the reasonable belief
that his or her act, or failure to act, was in the best interests of the
Company, then the act, or failure to act, will not be deemed willful for
purposes of this definition.

          COMPANY includes any successor entity.

          GOOD REASON means the occurrence, without the Participant's express
written consent, of:

          (1)    a reduction in the Participant's title, annual base salary or a
significant reduction in responsibilities as in effect immediately prior to, or
as increased after, the effective date of the Change of Control; or

          (2)    the relocation of the Participant's principal place of
employment to a location more than fifty miles from the Participant's principal
place of employment prior to the effective date of the Change of Control or a
relocation that increases the Participant's commuting distance to and from the
relocated place of employment to more than fifty miles.

     (d)  If the benefits to the Participant resulting from Sections 17A(b)(i)
and 17A(b)(ii) and any other benefits otherwise payable to a Participant
constitute a parachute payment ("Payment") within the meaning of Section 280G
(as amended or replaced) of the Code, and, except for this Section 17A(d), would
be subject to the excise tax imposed by Section 4999 (as amended or replaced) of
the Code (the "Excise Tax"), then the Payment will be the full amount or a
lesser amount (with cash payments reduced before Stock Award compensation),
whichever results in the Participant's receipt, on an after tax basis, of the
greater amount of the Payment whether or not all or some portion of the Payment
may be subject to the Excise Tax.

     Accountants selected by the Company will make, in writing and in good
faith, any determination required under this Section 17A(d), unless the Company
and the Participant otherwise agree in writing. The accountants may make
reasonable

                                      -11-
<Page>

assumptions and approximations in applying the Code to make their determination.
The Company and the Participants will furnish to the accountants any information
and documents that the accountants may reasonably request. The Company will pay
all reasonable costs the accountants may incur in providing this determination.

18.  NO SPECIAL EMPLOYMENT RIGHTS.

     Nothing contained in the Plan or in any option or award shall confer upon
any recipient of an award or optionee any right with respect to the continuation
of his or her employment by the Company or interfere in any way with the right
of the Company at any time to terminate such employment or to increase or
decrease the compensation of the optionee.

19.  OTHER EMPLOYEE BENEFITS.

     Except as to plans which by their terms include such amounts as
compensation, neither the amount of any compensation deemed to be received by an
employee as a result of the exercise of an option or the sale of shares received
upon such exercise nor the value of an award granted to an employee will
constitute compensation with respect to which any other employee benefits of
such employee are determined, including, without limitation, benefits under any
bonus, pension, profit-sharing, life insurance or salary continuation plan,
except as otherwise specifically determined by the Board of Directors.

20.  AMENDMENT OF THE PLAN.

     (a)  The Board of Directors may at any time, and from time to time, modify
or amend the Plan in any respect, except that if at any time the approval of the
shareholders of the Company is required as to such modification or amendment
under Section 422 of the Code or any successor provision with respect to
Incentive Stock Options or under Rule 16b-3 with respect to options held by or
awards made to Reporting Persons, the Board of Directors may not effect such
modification or amendment without such approval.

     (b)  The termination or any modification or amendment of the Plan shall
not, without the consent of an optionee or recipient of an award, affect his or
her rights under an option or award previously granted to him or her. With the
consent of the optionee or recipient of the award affected, the Board of
Directors may amend outstanding option agreements or awards in a manner not
inconsistent with the Plan. The Board of Directors shall have the right to amend
or modify (i) the terms and provisions of the Plan and of any outstanding
Incentive Stock Options granted under the Plan to the extent necessary to
qualify any or all such options for such favorable federal income tax treatment
(including deferral of taxation upon exercise) as may be afforded incentive
stock options under Section 422 of the Code and (ii) the terms and provisions of
the Plan and of any outstanding option or award to the extent necessary to
ensure the qualification of the Plan under Rule 16b-3 or any successor rule.

                                      -12-
<Page>

21.  WITHHOLDING.

     (a)  The Company shall have the right to deduct from payments of any kind
otherwise due to the optionee or recipient of an award any federal, state or
local taxes of any kind required by law to be withheld with respect to any
shares issued upon exercise of options under the Plan or the purchase of shares
subject to the award. Subject to the prior approval of the Company, which may be
withheld by the Company in its sole discretion, the optionee or recipient of an
award may elect to satisfy such obligations, in whole or in part, (i) by causing
the Company to withhold shares of Common Stock otherwise issuable pursuant to
the exercise of an option or the purchase of shares subject to an award or (ii)
by delivering to the Company shares of Common Stock already owned by the
optionee or award recipient. The shares so delivered or withheld shall have a
fair market value equal to such withholding obligation. The fair market value of
the shares used to satisfy such withholding obligation shall be determined by
the Company as of the date that the amount of tax to be withheld is to be
determined. An optionee or award recipient who has made an election pursuant to
this Section 21(a) may only satisfy his or her withholding obligation with
shares of Common Stock which are not subject to any repurchase, forfeiture,
unfulfilled vesting or other similar requirements.

     (b)  Notwithstanding the foregoing, in the case of a Reporting Person, no
election to use shares for the payment of withholding taxes shall be effective
unless made in compliance with any applicable requirements of Rule 16b-3.

     (c)  If the recipient of an award under the Plan elects, in accordance with
Section 83(b) of the Code, to recognize ordinary income in the year of
acquisition of any shares awarded under the Plan, the Company will require at
the time of such election an additional payment for withholding tax purposes
based on the difference, if any, between the purchase price of such shares and
the fair market value of such shares as of the date immediately preceding the
date of the award.

22.  CANCELLATION AND NEW GRANT OF OPTIONS, ETC.

     The Board of Directors shall have the authority to effect, at any time and
from time to time, with the consent of the affected optionees, (i) the
cancellation of any or all outstanding options under the Plan and the grant in
substitution therefor of new options under the Plan covering the same or
different numbers of shares of Common Stock and having an option exercise price
per share which may be lower or higher than the exercise price per share of the
cancelled options or (ii) the amendment of the terms of any and all outstanding
options under the Plan to provide an option exercise price per share which is
higher or lower than the then-current exercise price per share of such
outstanding options.

23.  EFFECTIVE DATE AND DURATION OF THE THE PLAN.

     (a)  EFFECTIVE DATE. The Plan shall become effective when adopted by the
Board of Directors, but no Incentive Stock Option granted under the Plan shall
become

                                      -13-
<Page>

exercisable unless and until the Plan shall have been approved by the Company's
shareholders. If such shareholder approval is not obtained within twelve months
after the date of the Board's adoption of the Plan, no options previously
granted under the Plan shall be deemed to be Incentive Stock Options and no
Incentive Stock Options shall be granted thereafter. Amendments to the Plan not
requiring shareholder approval shall become effective when adopted by the Board
of Directors; amendments requiring shareholder approval (as provided in Section
20) shall become effective when adopted by the Board of Directors, but no
Incentive Stock Option issued after the date of such amendment shall become
exercisable (to the extent that such amendment to the Plan was required to
enable the Company to grant such Incentive Stock Option to a particular
optionee) unless and until such amendment shall have been approved by the
Company's shareholders. If such shareholder approval is not obtained within
twelve months of the Board's adoption of such amendment, any Incentive Stock
Options granted on or after the date of such amendment shall terminate to the
extent that such amendment to the Plan was required to enable the Company to
grant such option to a particular optionee. Subject to this limitation, options
and awards may be granted under the Plan at any time after the effective date
and before the date fixed for termination of the Plan.

     (b)  TERMINATION. Unless sooner terminated in accordance with Section 17,
the Plan shall terminate, with respect to Incentive Stock Options, upon the
earlier of (i) the close of business on the day next preceding the tenth
anniversary of the date of its adoption by the Board of Directors, or (ii) the
date on which all shares available for issuance under the Plan shall have been
issued pursuant to the exercise or cancellation of options or the final vesting
of awards granted under the Plan. Unless sooner terminated in accordance with
Section 17, the Plan shall terminate with respect to options which are not
Incentive Stock Options and awards on the date specified in (ii) above. If the
date of termination is determined under (i) above, then options outstanding on
such date shall continue to have force and effect in accordance with the
provisions of the instruments evidencing such options.

24.  PROVISION FOR FOREIGN PARTICIPANTS.

     The Board of Directors may, without amending the Plan, modify awards or
options granted to participants who are foreign nationals or employed outside
the United States to recognize differences in laws, rules, regulations or
customs of such foreign jurisdictions with respect to tax, securities, currency,
employee benefit or other matters.

                                      -14-<Page>

                                                                   EXHIBIT 10.19

As amended through August 6, 2001 and
adjusted for stock splits in April and October 2000

                        MILLENNIUM PHARMACEUTICALS, INC.

                        1996 EMPLOYEE STOCK PURCHASE PLAN

     The purpose of this Plan is to provide eligible employees of Millennium
Pharmaceuticals, Inc. (the "Company") and certain of its subsidiaries with
opportunities to purchase shares of the Company's Common Stock (the "Common
Stock"). Two Million Six Hundred Thousand (2,600,000) shares of Common Stock in
the aggregate have been approved for this purpose.

     1.   ADMINISTRATION. The Plan will be administered by the Company's Board
of Directors (the "Board") or by a Committee appointed by the Board (the
"Committee"). The Board or the Committee has authority to make rules and
regulations for the administration of the Plan and its interpretation and
decisions with regard thereto shall be final and conclusive.

     2.   ELIGIBILITY. Participation in the Plan will neither be permitted nor
denied contrary to the requirements of Section 423 of the Internal Revenue Code
of 1986, as amended (the "Code"), and regulations promulgated thereunder. All
employees of the Company, including directors who are employees, and all
employees of any subsidiary of the Company (as defined in Section 424(f) of the
Code) designated by the Board or the Committee from time to time (a "Designated
Subsidiary"), are eligible to participate in any one or more of the offerings of
Options (as defined below) to purchase Common Stock under the Plan, provided
that:

          (a)  they are regularly employed by the Company or a Designated
     Subsidiary for more than 20 hours a week and for more than five months in a
     calendar year; and

          (b)  they are employees of the Company or a Designated Subsidiary on
     the first day of the applicable Plan Period (as defined below).

     No employee may be granted an option hereunder if such employee,
immediately after the option is granted, owns 5% or more of the total combined
voting power or value of the stock of the Company or any subsidiary. For
purposes of the preceding sentence, the attribution rules of Section 424(d) of
the Code shall apply in determining the stock ownership of an employee, and all
stock which the employee has a contractual right to purchase shall be treated as
stock owned by the employee.

<Page>

     3.   OFFERINGS. The Company will make one or more offerings ("Offerings")
to employees to purchase Common Stock under this Plan. The Board or the
Committee shall determine the commencement dates of each of the Offerings (the
"Offering Commencement Dates"). Each Offering Commencement Date will begin a
period (a "Plan Period") during which payroll deductions will be made and held
for the purchase of Common Stock at the end of the Plan Period. The Board or the
Committee shall choose a Plan Period of twelve (12) months or less for each of
the Offerings and may, at its discretion, choose a different Plan Period for
each Offering.

     4.   PARTICIPATION. An employee eligible on the Offering Commencement Date
of any Offering may participate in such Offering by completing and forwarding a
payroll deduction authorization form to the Controller of the Company at least
14 days prior to the applicable Offering Commencement Date. The form will
authorize a regular payroll deduction from the Compensation received by the
employee during the Plan Period. Unless an employee files a new form or
withdraws from the Plan, his deductions and purchases will continue at the same
rate for future Offerings under the Plan as long as the Plan remains in effect.
The term "Compensation" means the amount of money reportable on the employee's
Federal Income Tax Withholding Statement, excluding overtime, shift premium,
incentive or bonus awards, allowances and reimbursements for expenses such as
relocation allowances for travel expenses, income or gains on the exercise of
Company stock options or stock appreciation rights, and similar items, whether
or not shown on the employee's Federal Income Tax Withholding Statement, but
including, in the case of salespersons, sales commissions to the extent
determined by the Board or the Committee.

     5.   DEDUCTIONS.

          (a)  The Company will maintain payroll deduction accounts for all
participating employees. With respect to any Offering made under this Plan, an
employee may authorize a payroll deduction in any dollar amount up to a maximum
of 10% of the Compensation he or she receives during the Plan Period or such
shorter period during which deductions from payroll are made. Payroll deductions
may be at the rate of 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% of Compensation.

          (b)  No employee may be granted an Option which permits his rights to
purchase Common Stock under this Plan and any other stock purchase plan of the
Company and its subsidiaries, to accrue at a rate which exceeds $25,000 of the
fair market value of such Common Stock (determined at the Offering Commencement
Date of the Plan Period) for each calendar year in which the Option is
outstanding at any time.

                                        2
<Page>

     6.   DEDUCTION CHANGES. An employee may decrease or discontinue his payroll
deduction once during any Plan Period by filing a new payroll deduction
authorization form. However, an employee may not increase his payroll deduction
during a Plan Period. If an employee elects to discontinue his payroll
deductions during a Plan Period, but does not elect to withdraw his funds
pursuant to Section 8 hereof, funds deducted prior to his election to
discontinue will be applied to the purchase of Common Stock on the Exercise Date
(as defined below).

     7.   INTEREST. Interest will not be paid on any employee payroll deduction
accounts, except to the extent that the Board or its Committee, in its sole
discretion, elects to credit such accounts with interest at such per annum rate
as it may from time to time determine.

     8.   WITHDRAWAL OF FUNDS. An employee may on any one occasion during a Plan
Period and for any reason withdraw all or part of the balance accumulated in the
employee's payroll deduction account. Any such withdrawal must be effected prior
to the close of business on the last day of the Plan Period. If the employee
withdraws all of such balance, the employee shall thereby withdraw from
participation in the Offering and may not begin participation again during the
remainder of the Plan Period. Any employee withdrawing all or part of such
balance may participate in any subsequent Offering in accordance with terms and
conditions established by the Board or the Committee, except that, unless
otherwise permitted under Section 16 of the Securities Exchange Act of 1934, as
amended (the "Exchange Act"), and the rules promulgated thereunder, any employee
who is also a director and/or officer of the Company within the meaning of
Section 16 of the Exchange Act may not (a) withdraw less than all of the balance
accumulated in such employee's payroll deduction account or (b) participate
again for a period of at least six months as provided in Rule l6b-3(d)(2)(i) or
any successor provision under the Exchange Act.

     9.   PURCHASE OF SHARES.

          (a)  On the Offering Commencement Date of each Plan Period, the
Company will grant to each eligible employee who is then a participant in the
Plan an option (an "Option") to purchase on the last business day of such Plan
Period (the "Exercise Date"), at the Option Price hereinafter provided for, such
number of whole shares of Common Stock of the Company reserved for the purposes
of the Plan as does not exceed the number of shares determined by dividing 15%
of such employee's annualized Compensation for the immediately prior six-month
period by the price determined in accordance with the formula set forth in the
following paragraph but using the closing price on the Offering Commencement
Date of such Plan Period.

          (b)  The Option Price for each share purchased will be 85% of the
closing price of the Common Stock on (i) the first

                                        3
<Page>

business day of such Plan Period or (ii) the Exercise Date, whichever closing
price shall be less. Such closing price shall be (A) the closing price of the
Common Stock on any national securities exchange on which the Common Stock is
listed, or (B) the closing price of the Common Stock on the Nasdaq National
Market ("Nasdaq") or (C) the average of the closing bid and asked prices in the
over-the-counter market, whichever is applicable, as published in THE WALL
STREET JOURNAL. If no sales of Common Stock were made on such a day, the price
of the Common Stock for purposes of clauses (A) and (B) above shall be the
reported price for the next preceding day on which sales were made.

          (c)  Each employee who continues to be a participant in the Plan on
the Exercise Date shall be deemed to have exercised his Option at the Option
Price on such date and shall be deemed to have purchased from the Company the
number of full shares of Common Stock reserved for the purpose of the Plan that
his accumulated payroll deductions on such date will pay for pursuant to the
formula set forth above (but not in excess of the maximum number determined in
the manner set forth above).

          (d)  Any balance remaining in an employee's payroll deduction account
at the end of a Plan Period will be automatically refunded to the employee,
except that any balance which is less than the purchase price of one share of
Common Stock will be carried forward into the employee's payroll deduction
account for the following Offering, unless the employee elects not to
participate in the following Offering under the Plan, in which case the balance
in the employee's account shall be refunded.

     10.  ISSUANCE OF CERTIFICATES. Certificates representing shares of Common
Stock purchased under the Plan may be issued only in the name of the employee,
in the name of the employee and another person of legal age as joint tenants
with rights of survivorship, or (in the Company's sole discretion) in the street
name of a brokerage firm, bank or other nominee holder designated by the
employee.

     11.  RIGHTS ON RETIREMENT, DEATH OR TERMINATION OF EMPLOYMENT. In the event
of a participating employee's termination of employment prior to the last
business day of a Plan Period (whether as a result of the employee's voluntary
or involuntary termination, retirement, death or otherwise), no payroll
deduction shall be taken from any pay due and owing to the employee and the
balance in the employee's payroll deduction account shall be paid to the
employee or, in the event of the employee's death, (a) to a beneficiary
previously designated in a revocable notice signed by the employee (with any
spousal consent required under state law) or (b) in the absence of such a
designated beneficiary, to the executor or administrator of the employee's
estate or (c) if no such executor or administrator has been appointed to the
knowledge of the Company, to such other person(s) as the Company may, in its
discretion, designate. If,

                                        4
<Page>

prior to the last business day of the Plan Period, the Designated Subsidiary by
which an employee is employed shall cease to be a subsidiary of the Company, or
if the employee is transferred to a subsidiary of the Company that is not a
Designated Subsidiary, the employee shall be deemed to have terminated
employment for the purposes of this Plan.

     12.  OPTIONEES NOT STOCKHOLDERS. Neither the granting of an Option to an
employee nor the deductions from his pay shall constitute such employee a
stockholder of the shares of Common Stock covered by an Option under this Plan
until such shares have been purchased by and issued to him.

     13.  RIGHTS NOT TRANSFERABLE. Rights under this Plan are not transferable
by a participating employee other than by will or the laws of descent and
distribution, and are exercisable during the employee's lifetime only by the
employee.

     14.  APPLICATION OF FUNDS. All funds received or held by the Company under
this Plan may be combined with other corporate funds and may be used for any
corporate purpose.

     15.  ADJUSTMENT IN CASE OF CHANGES AFFECTING COMMON STOCK. In the event of
a subdivision of outstanding shares of Common Stock, or the payment of a
dividend in Common Stock, the number of shares approved for this Plan, and the
share limitation set forth in Section 9, shall be increased proportionately, and
such other adjustment shall be made as may be deemed equitable by the Board or
the Committee. In the event of any other change affecting the Common Stock, such
adjustment shall be made as may be deemed equitable by the Board or the
Committee to give proper effect to such event.

     16.  MERGER.

          (a)  If the Company shall at any time merge or consolidate with
another corporation and the holders of the capital stock of the Company
immediately prior to such merger or consolidation continue to hold at least 80%
by voting power of the capital stock of the surviving corporation ("Continuity
of Control"), the holder of each Option then outstanding will thereafter be
entitled to receive at the next Exercise Date upon the exercise of such Option
for each share as to which such Option shall be exercised the securities or
property which a holder of one share of the Common Stock was entitled to upon
and at the time of such merger, and the Board or the Committee shall take such
steps in connection with such merger as the Board or the Committee shall deem
necessary to assure that the provisions of Section 15 shall thereafter be
applicable, as nearly as reasonably may be, in relation to the said securities
or property as to which such holder of such Option might thereafter be entitled
to receive thereunder.

                                        5
<Page>

          (b)  In the event of a merger or consolidation of the Company with or
into another corporation which does not involve Continuity of Control, or of a
sale of all or substantially all of the assets of the Company while unexercised
Options remain outstanding under the Plan, (i) subject to the provisions of
clauses (ii) and (iii), after the effective date of such transaction, each
holder of an outstanding Option shall be entitled, upon exercise of such Option,
to receive in lieu of shares of Common Stock, shares of such stock or other
securities as the holders of shares of Common Stock received pursuant to the
terms of such transaction; or (ii) all outstanding Options may be cancelled by
the Board or the Committee as of a date prior to the effective date of any such
transaction and all payroll deductions shall be paid out to the participating
employees; or (iii) all outstanding Options may be cancelled by the Board or the
Committee as of the effective date of any such transaction, provided that notice
of such cancellation shall be given to each holder of an Option, and each holder
of an Option shall have the right to exercise such Option in full based on
payroll deductions then credited to his account as of a date determined by the
Board or the Committee, which date shall not be less than ten (10) days
preceding the effective date of such transaction.

     17.  AMENDMENT OF THE PLAN. The Board may at any time, and from time to
time, amend this Plan in any respect, except that (a) if the approval of any
such amendment by the stockholders of the Company is required by Section 423 of
the Code or by Rule 16b-3 under the Exchange Act, such amendment shall not be
effected without such approval, and (b) in no event may any amendment be made
which would cause the Plan to fail to comply with Section 16 of the Exchange Act
and the rules promulgated thereunder, as in effect from time to time, or Section
423 of the Code.

     18.  INSUFFICIENT SHARES. In the event that the total number of shares of
Common Stock specified in elections to be purchased under any Offering plus the
number of shares purchased under previous Offerings under this Plan exceeds the
maximum number of shares issuable under this Plan, the Board or the Committee
will allot the shares then available on a pro rata basis.

     19.  TERMINATION OF THE PLAN.  This Plan may be terminated at any time by
the Board. Upon termination of this Plan all amounts in the payroll deduction
accounts of participating employees shall be promptly refunded.

     20.  GOVERNMENTAL REGULATIONS.

          (a)  The Company's obligation to sell and deliver Common Stock under
this Plan is subject to listing on a national stock exchange or quotation on
Nasdaq and the approval of all governmental authorities required in connection
with the authorization, issuance or sale of such stock.

                                        6
<Page>

          (b)  The Plan shall be governed by the laws of the State of Delaware
except to the extent that such law is preempted by federal law.

          (c)  The Plan is intended to comply with the provisions of Rule 16b-3
promulgated under the Exchange Act. Any provision inconsistent with such Rule
shall to that extent be inoperative and shall not affect the validity of the
Plan.

     21.  ISSUANCE OF SHARES.  Shares may be issued upon exercise of an Option
from authorized but unissued Common Stock, from shares held in the treasury of
the Company, or from any other proper source.

     22.  NOTIFICATION UPON SALE OF SHARES. Each employee agrees, by entering
the Plan, to promptly give the Company notice of any disposition of shares
purchased under the Plan where such disposition occurs within two years after
the date of grant of the Option pursuant to which such shares were purchased.

     23.  EFFECTIVE DATE AND APPROVAL OF STOCKHOLDERS. The Plan shall take
effect upon the closing of the Company's initial public offering of Common Stock
pursuant to an effective registration statement under the Securities Act of
1933, as amended, subject to approval by the stockholders of the Company as
required by Rule 16b-3 under the Exchange Act and by Section 423 of the Code,
which approval must occur within twelve months of the adoption of the Plan by
the Board.
                                        7

Source: [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00047-of-00352.parquet"}, [{"source": "alea-institute/alea-institute/kl3m-data-edgar-agreements/train-00047-of-00352.parquet"}]]