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                                                                 Exhibit 10.3.21

                               FIRST AMENDMENT TO
                              AMENDED AND RESTATED
                            ENERGY PURCHASE AGREEMENT

     This FIRST AMENDMENT TO AMENDED AND RESTATED ENERGY PURCHASE AGREEMENT
("Amendment"), is made and entered into on this third day of June, 2002 by and
between Sithe/Independence Power Partners, L.P. ("Independence") and
Consolidated Edison Company of New York, Inc. ("ConEd").

     WHEREAS, the September 1, 2000 Amended and Restated Energy Purchase
Agreement ("September 1 Agreement") contemplated that Independence and ConEd
would come to a mutual agreement on the amount of equivalent Installed Capacity
that Independence is obligated to sell and ConEd is obligated to purchase under
the September 1 Agreement, in the event that the Installed Capacity Requirements
in effect as of the date of the September 1 Agreement were replaced with new
Installed Capacity Requirements;

     WHEREAS, the New York Independent System Operator ("NYISO" or "ISO") has
implemented a new Installed Capacity Requirements system, effective November 1,
2001, based on a calculation of Unforced Capacity, as that term is defined in
and as such calculation is set forth in the NYISO's July 6, 2001 filing amending
the ISO Services Tariff in FERC Docket No. ER01-2536-000, and as such filing
was accepted for filing by the Federal Energy Regulatory Commission on September
4, 2001 in NEW YORK INDEPENDENT SYSTEM OPERATOR, INC., 96 FERC 61,251 (2001);

     WHEREAS, Independence and ConEd entered into a Letter Agreement dated
November 1, 2001 ("Letter Agreement") providing for the interim determination of
Installed Capacity rights and obligations under the NYISO's Installed Capacity
Requirements for the period November 1, 2001 through April 30, 2002, which the
parties intended to reconcile following a final agreement on these issues;

     WHEREAS, Independence and ConEd have now agreed on a methodology for
calculating Independence's monthly obligation to sell Installed Capacity under
the ISO's new Unforced Capacity requirements, including the methodology for
reconciling the interim payments for the purchase of Unforced Capacity under
Paragraph 3 of the Letter Agreement; and

     WHEREAS, Independence and ConEd do not otherwise seek to alter the terms of
the September 1 Agreement;

     NOW, THEREFORE, in consideration of the mutual promises and agreements
contained herein, Independence and ConEd, intending to be legally bound, agree
as follows:

     1.   Section 1.02(u) of the September 1 Agreement is deleted in its
entirety and replaced with the following:

          (u) "Purchased Capacity" means, for each Contract Year: (a)
          740 MW of Installed Capacity, determined in accordance with
          the Installed Capacity Requirements in effect as of the
          effective date of the September 1 Agreement, for the period
          from September 1, 2000 through

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          October 31, 2001; (b) beginning November 1, 2001 and for as
          long as the quantity of Installed Capacity is determined in
          accordance with the ISO's Unforced Capacity methodology (as
          implemented on November 1, 2001), the Negotiated UCAP
          Amount; or (c) if and to the extent that the NYISO adopts a
          new Installed Capacity Requirements methodology to replace
          the Unforced Capacity methodology implemented on November 1,
          2001, or otherwise materially changes or abandons the
          Unforced Capacity methodology, "Purchased Capacity" shall
          mean an amount of Installed Capacity equivalent to the
          amount of Installed Capacity under clause (a) (as reasonably
          determined by mutual agreement of the parties), it being the
          intent of the parties that the rights and obligations under
          clause (a) will not be materially altered.

     2.   New subsections 1.02(x) and (y) shall be added to the September 1
Agreement, as follows:

          (x)  "Negotiated  UCAP  Amount"  means an amount of Unforced
          Capacity determined according to the following formula:

          Negotiated UCAP Amount =        740 MW X (1 - State Average
                                          EFORd)+10 MW

          where: State Average EFORd =    New York Control Area average
                                          forced outage rate of
                                          generating resources used by
                                          the NYISO to determine Load
                                          Serving Entities' Installed
                                          Capacity Requirements, as
                                          such rate is determined by
                                          the NYISO for the applicable
                                          period

          As an example of how the Negotiated UCAP Amount would be
          calculated, the parties agree that the New York Control Area
          average forced outage rate applicable for the summer 2002
          Capability Period (as that term is defined in the ISO
          Services Tariff) is 9.68%, and therefore, the calculation
          for the Negotiated UCAP Amount for that summer 2002
          Capability Period is 740 MW X (1 - 9.68%) + 10 MW = 678.4
          MW.

          (y)  "Unforced  Capacity"  has the meaning  assigned to that
          term in the ISO Services Tariff.

     3.   Sections 1.02(e) and (k) (defining "Current Installed Capacity
Requirements" and "Future Installed Capacity Requirements") shall each be
deleted in their entirety and replaced with the words "Intentionally left
blank."

     4.   For purposes of clarification, the words "or Unforced Capacity,
whichever is relevant," are added to Section 3.02(a) of the September 1
Agreement, after the words "Installed Capacity."

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     5.   The parties agree that, for purposes of the reconciliation required in
Paragraph 3 of the Letter Agreement, the reconciliation amount is $112,800. As
of the execution of this Amendment and Independence's payment of this
reconciliation amount to ConEd, the parties will have fulfilled all of their
obligations under the Letter Agreement.

     6.   Except as set forth above, the capacity purchase and sale will be
governed by the terms of the September 1 Agreement, including but not limited to
the preservation of Independence's right to obtain Replacement Capacity for the
Purchased Capacity from a source other than the Independence Station, and Con
Edison's right to receive the Price Adjustment, calculated as set forth in
Section 3.02(d) of the September 1 Agreement, upon Independence's failure to
provide the Purchased Capacity (including Replacement Capacity). Furthermore,
except as amended hereby, the September 1 Agreement shall remain unchanged and
in full force and effect.

     7.   This Amendment constitutes the entire understanding between the
parties, and supersedes any and all previous understandings, oral or written,
with respect to the subject matter hereof. This Amendment may be executed in
counterparts, all of which shall constitute one and the same Agreement and each
of which shall be deemed to be an original. Any term used in this Amendment that
is not defined herein shall have the meaning that is in the September 1
Agreement.

     8.   This Amendment shall be governed by and construed and enforced in
accordance with the laws of the State of New York applicable to contracts made
and to be performed therein. The parties agree that all disputes between them
which arise under this Amendment and which are not settled, other than disputes
which are exclusively within the jurisdiction of FERC, shall be decided by a
court of competent jurisdiction in the State of New York and the parties submit
to the jurisdiction of the courts of the State of New York and the Federal
District Courts located in New York, New York.

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          IN WITNESS WHEREOF, the parties have executed this Amendment by their
authorized representatives as of the day and year first set forth above.

                        SITHE/INDEPENDENCE POWER PARTNERS, L.P.

                              By: Sithe/Independence, Inc., its general partner

                              By: /s/ Sandra Manilla
                                  ------------------------------------
                                  Name:  SANDRA MANILLA

                                  Title: Vice President & Treasurer

                        CONSOLIDATED EDISON COMPANY OF NEW YORK, INC.

                              By: /s/ Joseph P. Oates
                                  ------------------------------------
                                  Name:  Joseph P. Oates

                                  Title: Vice President, Energy Management

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                                                                    Exhibit 10.1

                          CUBIST PHARMACEUTICALS, INC.

                              AMENDED AND RESTATED
                           2000 EQUITY INCENTIVE PLAN

          This Amended and Restated Equity Incentive Plan amends and restates
the Company's 2000 Nonstatutory Stock Option Plan to read in its entirety as set
forth below. As part of this amendment and restatement, the name of the
Company's 2000 Nonstatutory Stock Option Plan has been changed to the Amended
and Restated 2000 Equity Incentive Plan.

          The options granted under this Amended and Restated 2000 Equity
Incentive Plan are NOT intended to be treated as "incentive stock options"
within the meaning of Section 422 of the Code.

          1.   DEFINITIONS. As used in this Amended and Restated 2000 Equity
Incentive Plan of Cubist Pharmaceuticals, Inc., the following terms shall have
the following meanings:

          1.1. ACCELERATE, ACCELERATED, and ACCELERATION, when used with respect
to an Option, means that as of the relevant time of reference such Option will
become exercisable with respect to some or all of the shares of Stock for which
it was not then otherwise exercisable by its terms and, when used with respect
to Restricted Stock, means that the Risk of Forfeiture otherwise applicable to
such Restricted Stock shall expire with respect to some or all of such
Restricted Stock.

          1.2  AWARD means the grant or sale pursuant to the Plan of Restricted
Stock, Stock Grants or Options.

          1.3. AWARD AGREEMENT means an agreement between the Company and the
recipient of an Award, setting forth the terms and conditions of an Option or of
a grant or sale of Restricted Stock or of a Stock Grant.

          1.4. BOARD means the Company's Board of Directors.

          1.5. CHANGE IN CORPORATE CONTROL means (1) the closing of (A) any
consolidation or merger of the Company in which the Company is not the
continuing or surviving corporation or pursuant to which Shares would be
converted into cash, securities or other property, other than a merger or
consolidation in which the holders of Stock immediately prior to the merger or
consolidation will have the same proportionate ownership of common

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stock of the surviving corporation immediately after the merger or consolidation
as before the merger or consolidation, or (B) any sale, lease, exchange, or
other transfer in a single transaction or a series of related transactions of
all or substantially all of the assets of the Company, or (2) the date on which
any "person" (as defined in Section 13(d) of the Exchange Act), other than the
Company or a Subsidiary or employee benefit plan or trust maintained by the
Company or any of its Subsidiaries shall become (together with its "affiliates"
and "associates," as defined in Rule 12b-2 under the Exchange Act) the
"beneficial owner" (as defined in Rule 13d-3 under the Exchange Act), directly
or indirectly, of 100% of the Stock outstanding at the time, with the prior
approval of the Board, or (3) a Hostile Change in Corporate Control.

          1.6.  CODE means the United States Internal Revenue Code of 1986, as
amended.

          1.7.  COMPANY means Cubist Pharmaceuticals, Inc., a Delaware
corporation.

          1.8.  COMPENSATION COMMITTEE means a committee comprised of two or
more Outside Directors, appointed by the Board, and vested by the Board with the
power and authority to administer the Plan in accordance with the provisions of
Section 5.

          1.9.  EXCHANGE ACT means the Securities Exchange Act of 1934, as
amended.

          1.10. FAIR MARKET VALUE means on any date (i) if the Stock is traded
on a stock exchange or on the Nasdaq National Market, the closing price on the
date in question or, if no trades were reported on such date, the closing price
on the most recent trading day preceding such date on which a trade occurred,
and (ii) if the Stock is not traded on a stock exchange or on the Nasdaq
National Market, the value of a Share on such date as determined by the Board or
the Compensation Committee.

          1.11. GRANT DATE means the date as of which an Option is granted, as
determined under Section 7.1.

          1.12. HOLDER means, with respect to any Award, (i) the person to whom
such Award shall have been granted under the Plan, or (ii) any transferee of
such Award to whom such Award shall have been transferred in accordance with the
provisions of Sections 7.7, 8.3(e) or8.3(f).

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          1.13. HOSTILE CHANGE IN CORPORATE CONTROL means the date on which any
"person" (as defined in Section 13(d) of the Exchange Act), other than the
Company or a Subsidiary or employee benefit plan or trust maintained by the
Company or any of its Subsidiaries shall become (together with its "affiliates"
and "associates," as defined in Rule 12b-2 under the Exchange Act) the
"beneficial owner" (as defined in Rule 13d-3 under the Exchange Act), directly
or indirectly, of more than 25% of the Stock outstanding at the time, without
the prior approval of the Board.

          1.14. INCENTIVE OPTION means an "incentive stock options" within the
meaning of Section 422 of the Code.

          1.15. INCUMBENT DIRECTORS means, in the case of a Hostile Change in
Corporate Control, those individuals who were members of the Company's Board of
Directors immediately prior to such Hostile Change in Corporate Control.

          1.16. OPTION means an option granted under the Plan to purchase
Shares.

          1.17. OPTION PRICE means the price paid by an Optionee for a Share
upon exercise of an Option.

          1.18. OPTIONEE means a person eligible to receive an Option, to whom
an Option shall have been granted under the Plan.

          1.19. OUTSIDE DIRECTOR shall mean a member of the Board who is not an
officer, employee or consultant of the Company or any Subsidiary.

          1.20. PLAN means this Amended and Restated 2000 Equity Incentive Plan
of the Company, as amended from time to time.

          1.21. RESTRICTED STOCK means an Award pursuant to Section 8 below of
shares of Stock subject to restrictions or other forfeiture conditions.

          1.22. RESTRICTION PERIOD means the period established by the
Compensation Committee and set forth in the applicable Award Agreement during
which the Risk of Forfeiture applicable to shares of Restricted Stock remains in
effect.

          1.23. RISK OF FORFEITURE means a limitation on the right of the Holder
to retain an Award of Restricted Stock, including a right for the Company to
reacquire the Shares at less than their then Fair Market Value, arising

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because of the occurrence or non-occurrence of specified events or conditions.

          1.24. RETIREMENT means, with respect to any Optionee that is an
employee of the Company, the voluntary retirement of such Optionee as an
employee of the Company at any time after age 65 or such earlier age as the
Compensation Committee shall determine.

          1.25. SECONDARY NIC means secondary national insurance contributions
as defined in the SSCBA.

          1.26. SECURITIES ACT means the United States Securities Act of 1933,
as amended.

          1.27. SHARES means shares of Stock.

          1.28. SSCBA means the Social Security Contributions and Benefit Act
1992 of the United Kingdom.

          1.29. STOCK means common stock, $.001 par value per share, of the
Company.

          1.30. STOCK EQUIVALENT means as of the date in question, any
securities of the Company exercisable, exchangeable or convertible into shares
of Stock.

          1.31. STOCK GRANT means an Award pursuant to Section 9 below of shares
of Stock not subject to restrictions or other forfeiture conditions.

          1.32. SUBSIDIARY means any corporation which qualifies as a subsidiary
of the Company under the definition of "subsidiary corporation" in Section
424(f) of the Code.

          1.33. UK OPTION means an Option granted to an employee of the UK
Subsidiary who is a resident of the United Kingdom or any Option giving rise to
the UK Subsidiary's liability for Secondary NIC.

          1.34. UK SUBSIDIARY means Cubist Pharmaceuticals (UK) Ltd., a company
organized under the laws of Wales and England.

          2.    PURPOSE. This Plan is intended to encourage ownership of Stock
by officers, employees and consultants to the Company and its Subsidiaries and
to provide additional incentives for them to promote the success of the

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                                       -5-

Company's business. The Plan is NOT intended to be an incentive stock option
plan within the meaning of Section 422 of the Code. None of the Options granted
hereunder will be Incentive Options.

          3.    TERM OF THE PLAN. Options may be granted hereunder at any time
in the period commencing upon the effectiveness of the Plan pursuant to Section
18 and ending on December 15, 2010.

          4.    STOCK SUBJECT TO tHE PLAN. Subject to the provisions of Section
13 of the Plan, at no time shall the number of Shares then outstanding which are
attributable to the exercise of Options granted under the Plan, PLUS the number
of Shares then issuable upon exercise of outstanding Options granted under the
Plan exceed 1,630,000 Shares, which aggregate number of Shares, automatically
and without further action, will increase, effective January 1, 2003, and each
January 1 thereafter during the term of the Plan until and including January 1,
2006, by an additional number of Shares equal to five percent (5%) of the total
number of Shares of Stock and Stock Equivalents issued and outstanding as of the
close of business on the immediately preceding December 31. The Shares of Stock
to be issued under the Plan, will be made available, at the discretion of the
Compensation Committee, from authorized but unissued Shares or Shares held by
the Company in its treasury. If any Option expires, terminates or is cancelled
for any reason without having been exercised in full, or if any Award of
Restricted Stock is forfeited by the recipient, the Shares not purchased by the
Optionee or forfeited by the recipient shall again be available for Awards to be
granted under the Plan.

          5.    ADMINISTRATION. Subject to the provisions set forth below in
this Section 5, the Plan shall be administered by the Compensation Committee.
Subject to the provisions of the Plan, the Compensation Committee shall have
complete authority, in its discretion, to make or to select the manner of making
all needful determinations with respect to each Award to be granted by the
Company in addition to any other determination allowed the Compensation
Committee under the Plan, including: (a) the officer, employee or consultant to
receive such Award; (b) whether the Award will be an Option, Restricted Stock or
Stock Grant, (c) the time of granting the Award; (d) the number of Shares
subject to the Award; (e) the Option Price of any Option or purchase price of
any Award of Restricted Stock; (f) the option period of any Option; (g) the
exercise date or dates or, if the Option is immediately exercisable in full on
its grant date or if the exercisability of the Option is accelerated by the
Compensation Committee in whole or in part at any time following its grant date,
the vesting schedule, if any, applicable to the Shares issuable upon the
exercise of the Option; (h) the Restriction

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Period and the terms of the Risk of Forfeiture applicable to an Award of
Restricted Stock; (i) the effect of termination of employment, consulting or
association with the Company on the subsequent exercisability of the Option or
the recipient's retention of any Award of Restricted Stock; and (j) whether the
Option or Restricted Stock may be transferred by the Holder to a third party. In
making such determinations, the Compensation Committee may take into account the
nature of the services rendered by the respective officers, employees and
consultants, their present and potential contributions to the success of the
Company and its Subsidiaries, and such other factors as the Compensation
Committee in its discretion shall deem relevant. Subject to the provisions of
the Plan, the Compensation Committee shall also have complete authority to
interpret the Plan, to prescribe, amend and rescind rules and regulations
relating to it, to determine the terms and provisions of the respective Award
Agreements (which need not be identical), and to make all other determinations
necessary or advisable for the administration of the Plan. The Compensation
Committee's determinations on the matters referred to in this Section 5 shall be
final, binding and conclusive on all persons having or claiming any interest
under the Plan or an Award made pursuant hereto. Notwithstanding anything
expressed or implied in the Plan to the contrary, (i) at any time and on any one
or more occasions, the Board may itself exercise any of the powers and
responsibilities assigned the Compensation Committee under the Plan and when so
acting shall have the benefit of all of the provisions of this Plan pertaining
to the Compensation Committee's exercise of its authorities hereunder, and (ii)
the Compensation Committee may delegate to the Chief Executive Officer of the
Company the authority to make Awards under the Plan to employees who are not
officers, and to consultants who are not officers, in accordance with guidelines
established by the Compensation Committee or the Board at any time and from time
to time.

          6.    ELIGIBILITY. An Award may be granted only to an employee,
officer or consultant of one or more of the Company and its Subsidiaries. In no
event shall the number of Shares covered by Options or other Awards granted
under the Plan to any one person in any one calendar year exceed 500,000, as may
be adjusted from time to time in accordance with Section 13.

          7.    OPTIONS.

          7.1.  TIME OF GRANTING OPTIONS. The granting of an Option shall take
place at the time specified by the Compensation Committee. Only if expressly so
provided in the applicable Award Agreement shall the Grant

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Date be the date on which an Award Agreement shall have been duly executed and
delivered by the Company and the Optionee.

          7.2.  OPTION PRICE. The Option Price under each Option shall be
determined by the Compensation Committee.

          7.3.  OPTION PERIOD. The option period under each Option shall be
determined by the Compensation Committee.

          7.4.  VESTING. An Option may be immediately exercisable or become
exercisable in such installments, cumulative or non-cumulative, as the
Compensation Committee may determine. Notwithstanding anything in this Section 7
or any applicable Award Agreement to the contrary, in the case of an Option not
otherwise immediately exercisable in full, the Compensation Committee may
Accelerate the exercisability of such Option in whole or in part at any time. In
the event that the Compensation Committee Accelerates the exercisability of any
Option in whole or in part at any time, the Compensation Committee may require
as a condition precedent to the effectiveness of any such Acceleration that the
holder of such Option shall enter into a written agreement with the Company
providing, among other things, that the Shares subject to such Option shall,
following their issuance upon exercise of such Option, be subject to a
repurchase option in favor of the Company upon such terms as the Compensation
Committee shall determine in its sole and absolute discretion.

          7.5.  UK OPTION. To the extent that it is lawful to do so, a UK Option
may be granted subject to a condition that any liability of the UK Subsidiary
(as employer of the relevant Optionee) to pay Secondary NIC in respect of the
exercise of such UK Option shall be the liability of the relevant Optionee and
payable by or recoverable from that Optionee in accordance with Section 12(c) of
this Plan, PROVIDED that the Compensation Committee may in its discretion at any
time or times release the Optionee from this liability or reduce his liability
hereunder unless an election in the form envisaged in Paragraph 3B(1) of
Schedule 1 to SSCBA has been entered into between the UK Subsidiary and that
Optionee and that election (or the legislation which provides for such an
election to be effective) does not allow for such an election to be subsequently
varied.

          7.6.  TERMINATION OF ASSOCIATION WITH THE COMPANY. Unless the
Compensation Committee shall provide otherwise with respect to any Option, if an
Optionee ceases to be an employee or consultant of the Company and its
Subsidiaries for any reason other than Retirement or death of such Optionee, any
Option held by such Optionee and/or any

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                                       -8-

subsequent Holder may be exercised by such Optionee and/or such subsequent
Holder at any time within 90 days after the termination of such relationship,
but only to the extent exercisable at termination and in no event after the
applicable option period. If an Optionee enters Retirement or dies, any Option
held by such Optionee and/or any subsequent Holder may be exercised by such
Optionee, such subsequent Holder and/or the executor or administrator of such
Optionee or such subsequent Holder at any time within the shorter of the
applicable option period or 12 months after the date of the Optionee's
Retirement or death, but only to the extent exercisable at the time of such
Optionee's Retirement or death. Options which are not exercisable at the time of
termination of employment or consultancy, as the case may be, between the
Company and the Optionee or which are so exercisable but are not exercised
within the time periods described above shall terminate. Notwithstanding the
foregoing, in the event that (i) the applicable Award Agreement with respect to
an Option shall contain specific provisions governing the effect that any such
termination shall have on the exercisability of such Option, or (ii) the Board,
shall at any time adopt specific provisions governing the effect that any such
termination shall have on the exercisability of such Option, then such
provisions shall, to the extent that they are inconsistent with the provisions
of this Section 7.6, control and be deemed to supersede the provisions of this
Section 7.6. For purposes of this Section 7.6, military or sick leave shall not
be deemed a termination of employment, PROVIDED that it does not exceed the
longer of 90 days or the period during which the absent Optionee's reemployment
rights, if any, are guaranteed by statute or by contract.

          7.7.  TRANSFERABILITY OF OPTIONS. Options shall not be transferable;
PROVIDED, HOWEVER, that Options shall be transferable by will or the laws of
descent and distribution; and PROVIDED, FURTHER, that Options may be transferred
to a third party if and to the extent authorized and permitted by the
Compensation Committee at the time of grant of such Options or at any time
thereafter. In granting its authorization and permission to any proposed
transfer of an Option to a third party, the Compensation Committee may impose
conditions or requirements that must be satisfied by the transferor or the third
party transferee prior to or in connection with such transfer, including,
without limitation, any conditions or requirements that may be necessary or
desirable, in the sole and absolute discretion of the Compensation Committee, to
ensure that such proposed transfer complies with applicable securities laws or
to prevent the Company, such transferor or such third party transferee from
violating or otherwise not be in compliance with applicable securities laws as a
result of such transfer. The Compensation Committee may at any time and from
time to time

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                                       -9-

delegate to one or more officers of the Company the authority to permit
transfers of Options to third parties pursuant to this Section 7.7, which
authorization shall be exercised by such officer or officers in accordance with
guidelines established by the Compensation Committee at any time and from time
to time. The restrictions on transferability set forth in this Section 7.7 shall
in no way preclude any Holder from effecting "cashless" exercises of an Option
pursuant to, and in accordance with, Section 7.8(b) hereof.

          7.8.  EXERCISE OF OPTION.

                (a)  An Option may be exercised only by giving written notice,
in the manner provided in Section 17 hereof, specifying the number of Shares as
to which the Option is being exercised, accompanied (except as otherwise
provided in paragraphs (b) and (c) of this Section 7.8) by full payment for such
Shares in the form of a check or bank draft payable to the order of the Company
or other Shares with a current Fair Market Value equal to the Option Price of
the Shares to be purchased. Receipt by the Company of such notice and payment
shall constitute the exercise of the Option or a part thereof. Upon receipt by
the Company of any such notice of exercise with respect to a UK Option, the
Company shall immediately deliver a copy thereof to the UK Subsidiary (as
employer of the relevant Optionee). Subject to the provisions of the Plan
(including, without limitation, Sections 10, 11 and 12) or any applicable Award
Agreement, within 30 days after receipt of such notice and payment, the Company
shall deliver or cause to be delivered to the Holder a certificate or
certificates for the number of Shares then being purchased by the Holder. Such
Shares shall be fully paid and nonassessable.

                (b)  In lieu of payment by check, bank draft or other Shares
accompanying the written notice of exercise as described in paragraph (a) of
this Section 7.8, a Holder may, unless prohibited by applicable law, elect to
effect payment by including with the written notice referred to in paragraph (a)
of this Section 7.8 irrevocable instructions to deliver for sale to a registered
securities broker acceptable to the Company that number of Shares subject to the
Option being exercised sufficient, after brokerage commissions, to cover the
aggregate exercise price of such Option and, if the Holder further elects, the
withholding obligations of the Optionee and/or such Holder pursuant to Section
12 with respect to such exercise, together with irrevocable instructions to such
broker to sell such Shares and to remit directly to the Company such aggregate
exercise price and, if the Holder has so elected, the amount of such withholding
obligation. The Company shall not be required to deliver to such securities
broker any stock certificate for

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such Shares until it has received from the broker such exercise price and, if
the Holder has so elected, the amount of such withholding obligation.

                (c)  The Compensation Committee shall have complete authority,
in its discretion, to permit the Holder, in lieu of payment by check, bank draft
or other Shares accompanying the written notice of exercise as described in
paragraph (a) of this Section 7.8, to effect payment by executing and delivering
to the Company a promissory note in the aggregate principal amount of the Option
Price of the Shares to be purchased. The promissory note shall be upon the terms
and conditions (including, without limitation, collateral security) acceptable
to the Compensation Committee.

                (d)  The right of the Holder to exercise an Option pursuant to
any provision of this Section 7.8, and the obligation of the Company to issue
Shares upon any exercise of an Option pursuant to this Section 7.8, is subject
to compliance with all of the other provisions of the Plan (including, without
limitation, Sections 10, 11 and 12) or any applicable Award Agreement.

          7.9   LIMITATION OF RIGHTS IN STOCK. A Holder shall not be deemed for
any purpose to be a stockholder of the Company with respect to any of the Shares
covered by an Option, except to the extent that the Option shall have been
exercised with respect thereto and, in addition, a certificate shall have been
issued therefor and delivered to the Holder or his agent.

          8.    RESTRICTED STOCK

          8.1.  PROVISION FOR GRANT. Shares of Restricted Stock may be issued
either alone or in addition to other Options granted under the Plan at such
price, if any, as the Compensation Committee may determine. The Compensation
Committee shall condition the grant of Restricted Stock upon the completion of
additional service, attainment of specified performance goals or such other
factors as the Compensation Committee may determine.

          8.2   AWARDS AND CERTIFICATES. The prospective recipient of a
Restricted Stock Award shall not have any rights with respect to such Award,
unless and until such recipient has executed an agreement evidencing the Award,
has delivered a fully executed copy thereof to the Company, and has otherwise
complied with the applicable terms and conditions of such Award.

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                                      -11-

          8.3   ADDITIONAL TERMS AND CONDITIONS. Grants of Restricted Stock may
be made under the following additional terms and conditions and such other terms
and conditions, not inconsistent with the terms of the Plan, as the Compensation
Committee may prescribe:

                (a)  PURCHASE PRICE. Shares of Restricted Stock shall be issued
          under the Plan for such consideration, in cash, promissory notes,
          other property or services, as is determined by the Compensation
          Committee. Any promissory note delivered in connection with the
          purchase of Restricted Stock shall be upon the terms and conditions
          (including, without limitation, collateral security) acceptable to the
          Compensation Committee.

                (b)  ACCEPTANCE OF AWARDS. Awards of Restricted Stock must be
          accepted within a period of 60 days (or such shorter period as the
          Compensation Committee may specify at grant) after the Award date, by
          executing an Award Agreement for Restricted Stock and paying whatever
          price (if any) is required pursuant to the terms of the Award.

                (c)  ISSUANCE OF CERTIFICATES. Subject to subsection (d) below,
          each Holder receiving an Award of Restricted Stock shall be issued a
          stock certificate in respect of the shares of Stock covered by such
          Award of Restricted Stock. Such certificate shall be registered in the
          name of such Holder, and, if applicable, shall bear an appropriate
          legend referring to the terms, conditions, and restrictions applicable
          to such Award substantially in the following form:

                     The transferability of this certificate and the shares
                     represented by this certificate are subject to the terms
                     and conditions of the Cubist Pharmaceuticals, Inc. Amended
                     and Restated 2000 Equity Incentive Plan and an Award
                     Agreement entered into by the registered owner and Cubist
                     Pharmaceuticals, Inc. Copies of such Plan and Agreement are
                     on file in the offices of Cubist Pharmaceuticals, Inc. at
                     65 Hayden Avenue, Lexington, Massachusetts 02421.

                (d)  ESCROW OF SHARES. The Compensation Committee may require
          that the stock certificates evidencing shares of Restricted Stock be
          held in custody by an officer of the Company, the designated escrow
          agent, until the restrictions thereon shall have lapsed, and

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                                      -12-

          that the Holder deliver a stock power, endorsed in blank, relating to
          the Stock covered by such Award.

                (e)  RESTRICTIONS AND RESTRICTION PERIOD. During the
          Restriction Period applicable to shares of Restricted Stock, such
          shares shall be subject to limitations on transferability and a Risk
          of Forfeiture arising on the basis of such conditions, related to the
          performance of service, Company or Subsidiary performance or
          otherwise, as the Compensation Committee may determine. Any such Risk
          of Forfeiture may be waived or terminated, in whole or in part, and/or
          the Restriction Period shortened, at any time by the Compensation
          Committee on such basis as it deems appropriate.

                (f)  TRANSFERABILITY. Upon any permitted transfer of shares of
          Restricted Stock without violating any restriction on transfer imposed
          pursuant to Section 8(e), such shares shall remain subject to any
          applicable terms, provisions, restrictions and limitations of such
          Restricted Stock, including any applicable restriction on transfer and
          Risk of Forfeiture.

                (g)  RIGHTS PENDING LAPSE OF RESTRICTIONS OR FORFEITURE OF
          AWARD. Except as provided in this subsection (g) and subsections (e)
          and (f) above, the Holder shall have, with respect to the shares of
          Restricted Stock, all of the rights of a stockholder of the Company,
          including the right to vote the shares, and the right to receive any
          cash dividends. The Compensation Committee, as determined at the time
          of Award, may permit or require the payment of cash dividends to be
          deferred and, if the Compensation Committee so determines, reinvested
          in additional Restricted Stock to the extent shares are available
          under Section 4.

                (h)  EFFECT OF TERMINATION OF EMPLOYMENT OR ASSOCIATION. Unless
          otherwise determined by the Compensation Committee (either at the time
          of grant of the Award or at any time thereafter) and subject to the
          applicable provisions of the Award Agreement and this Section 8, upon
          termination of a Holder's employment or
          other association with the Company and its Subsidiaries for any reason
          during the Restriction Period including on an entity ceasing to be a
          Subsidiary of the Company, all shares still subject to the Risk of
          Forfeiture shall be forfeited or otherwise subject to return to or
          repurchase by the Company on the terms specified in the Award
          Agreement; PROVIDED, HOWEVER, that military or sick leave or other
          bona fide leave shall not be deemed a termination of employment or

<Page>

                                      -13-

          other association, if it does not exceed the longer of 90 days or the
          period during which the absent optionee's reemployment rights, if any,
          are guaranteed by statute or by contract.

          8.4   LAPSE OF RESTRICTIONS. If and when the Restriction Period
expires without a prior forfeiture of the Restricted Stock subject to such
Restriction Period, the certificates for such shares shall be delivered to the
Holder promptly if not theretofore so delivered.

          9.    STOCK GRANTS

          In recognition of significant contributions to the success of the
Company or its Subsidiaries, in lieu of compensation otherwise already due and
in such other limited circumstances as the Compensation Committee deems
appropriate, shares of Stock may be issued either alone or in addition to other
Awards granted under the Plan at such price, if any, as the Compensation
Committee may determine. Stock Grant Awards shall be made without forfeiture
conditions of any kind and otherwise pursuant to such terms and conditions as
the Compensation Committee may determine.

          10.   RESTRICTIONS ON ISSUE OF SHARES.

                (a)  Notwithstanding any other provision of the Plan, if, at any
time, in the reasonable opinion of the Company the issuance of Shares covered by
an Award may constitute a violation of law, then the Company may delay such
issuance and the delivery of a certificate for such Shares until (i) approval
shall have been obtained from such governmental agencies, other than the
Securities and Exchange Commission, as may be required under any applicable law,
rule, or regulation; and (ii) in the case where such issuance would constitute a
violation of a law administered by or a regulation of the Securities and
Exchange Commission, one of the following conditions shall have been satisfied:

          (1)   the Shares are at the time of the issue of such Shares
effectively registered under the Securities Act; or

          (2)   the Company shall have determined, on such basis as it deems
appropriate (including an opinion of counsel or a no-action letter, each in form
and substance reasonably satisfactory to the Company) that the sale, transfer,
assignment, pledge, encumbrance or other disposition of such shares or such
beneficial interest, as the case may be, does not require registration under the
Securities Act or any applicable state securities laws.

<Page>

                                      -14-

The Company shall make all reasonable efforts to bring about the occurrence of
said events.

                (b)  If the Company shall deem it necessary or desirable to
register under the Securities Act or other applicable statutes any Shares with
respect to which an Award shall have been granted, or to qualify any such Shares
for exemption from the Securities Act or other applicable statutes, then the
Company shall take such action at its own expense. The Company may require from
each recipient of an Award, or each holder of Shares acquired pursuant to the
Plan, such information in writing for use in any registration statement,
prospectus, preliminary prospectus or offering circular as is reasonably
necessary for such purpose and may require reasonable indemnity to the Company
and its officers and directors from such holder against all losses, claims,
damage and liabilities arising from such use of the information so furnished and
caused by any untrue statement of any material fact therein or caused by the
omission to state a material fact required to be stated therein or necessary to
make the statements therein not misleading in the light of the circumstances
under which they were made.

                (c)  All certificates for shares of Stock or other securities
delivered under the Plan shall be subject to such stop-transfer orders and other
restrictions as the Compensation Committee may deem advisable under the rules,
regulations, and other requirements of any stock exchange upon which the Stock
is then listed, and any applicable federal or state securities law, and the
Compensation Committee may cause a legend or legends to be put on any such
certificates to make appropriate reference to such restrictions.

<Page>

                                      -15-

          11.   PURCHASE FOR INVESTMENT.

                (a)  Without limiting the generality of Section 10 hereof, if
the Shares to be issued pursuant to Awards granted under the Plan have not been
effectively registered under the Securities Act, the Company shall be under no
obligation to issue any Shares covered by any Award unless the Holder shall have
made such written representations and covenants to the Company (upon which the
Company believes it may reasonably rely) as the Company may deem necessary or
appropriate for purposes of ensuring that the issuance of such Shares will be
exempt from the registration requirements of the Securities Act and any
applicable state securities laws and otherwise in compliance with all applicable
laws, rules and regulations, including but not limited to written
representations that the Holder is acquiring the shares for his or her own
account for the purpose of investment and not with a view to, or for sale in
connection with, the distribution of any such Shares.

                (b)  Each Share to be issued pursuant to Awards granted pursuant
to this Plan may bear a reference to the investment representation made in
accordance with this Section 11 and to the fact that no registration statement
has been filed with the Securities and Exchange Commission in respect to such
Shares of Stock.

          12.   WITHHOLDING; NOTICE OF DISPOSITION OF STOCK PRIOR TO EXPIRATION
OF SPECIFIED HOLDING PERIOD.

                (a)  Whenever Shares are to be issued in satisfaction of an
Award granted hereunder, the Company shall have the right to require the
recipient of such Award and/or any subsequent Holder to remit to the Company an
amount sufficient to satisfy federal, state, local, employment or other tax
withholding requirements if, when and to the extent required by law (whether so
required to secure for the Company an otherwise available tax deduction or
otherwise) prior to the delivery of any certificate or certificates for such
Shares. The obligations of the Company under the Plan shall be conditional on
such payment and the Company shall, to the extent permitted by law, have the
right to deduct any such taxes from any payment of any kind otherwise due to the
recipient of an Award.

                (b)  The Compensation Committee may, at or after grant, permit
the recipient and/or subsequent Holder to satisfy any tax withholding
requirements pertaining to the issuance of Shares to satisfy an Award by
delivery to the Company of Shares (including, without limitation, Shares
retained from the exercise or grant of the Award that is creating the

<Page>

                                      -16-

tax obligation) having a value equal to the amount to be withheld. The value of
Shares to be so delivered shall be based on the Compensation Committee's
determination of the Fair Market Value of a Share on the date the amount of tax
to be withheld is to be determined.

                (c)  If a UK Option is exercised and the Optionee is required
under Section 7.5 hereof to either bear the cost of all or part of the Secondary
NIC or to enter into an election in the form envisaged in Paragraph 3B(1) of
Schedule 1 to SSCBA, then the Optionee shall by having delivered a notice of
exercise with respect to such UK Option be deemed to have granted to the UK
Subsidiary (as employer of the relevant Optionee) the irrevocable authority, as
agent of the Optionee and on his behalf, to sell or procure the sale of
sufficient Shares subject to such UK Option so that the net proceeds payable to
the UK Subsidiary are so far as possible equal to but not less than the amount
of the Secondary NIC which the Optionee is liable for and the UK Subsidiary
shall account to the Optionee for any balance. No Shares subject to any such UK
Option shall be issued to the Optionee until the UK Subsidiary has received
payment of the amount of Secondary NIC for which such Optionee is liable as a
result of the exercise of such UK Option.

          13.   ADJUSTMENT PROVISIONS.

          13.1  ADJUSTMENT FOR CORPORATE ACTIONS. All of the share numbers set
forth in the Plan reflect the capital structure of the Company as of March 5,
2002. If subsequent to such date the outstanding shares of Common Stock (or any
other securities covered by the Plan by reason of the prior application of this
Section) are increased, decreased, or exchanged for a different number or kind
of shares or other securities or property (including cash), or if subsequent to
such date additional shares or new or different shares or other securities or
property (including cash) are distributed with respect to or in exchange for
shares of Common Stock or other securities upon the merger, consolidation, sale
of all or substantially all the property or assets of the Company, sale of all
of the outstanding Common Stock of the Company, reorganization,
recapitalization, reclassification, stock dividend, stock split, reverse stock
split, or other distribution with respect to shares of Common Stock, or other
securities, (each of the foregoing events an "ADJUSTMENT EVENT") an appropriate
and proportionate adjustment will be made in (i) the maximum number and kind of
shares or other securities subject to the provisions of Section 4, (ii) the
numbers and kinds of shares or other securities or property (including cash)
subject to the then outstanding Options and Restricted Stock Awards, (iii) the
exercise price for each share or other unit of any other securities subject to
then outstanding

<Page>

                                      -17-

Options (without change in the aggregate purchase price as to which such Options
remain exercisable), and (iv) the repurchase price of each share of Restricted
Stock then subject to a Risk of Forfeiture in the form of a Company repurchase
right. Without limiting the generality of the foregoing provisions of this
Section 13.1, upon the occurrence of an Adjustment Event, Holders of Options
outstanding immediately prior to such Adjustment Event shall upon exercise of
such Options at any time following such Adjustment Event be entitled to receive
the shares of stock, other securities or property (including cash) that such
Holders would have received as a result of such Adjustment Event if such Holders
had exercised such Options immediately prior to such Adjustment Event. The
provisions of this Section 13.1 (including, without limitation, the immediately
preceding sentence) shall apply successively with respect to multiple Adjustment
Events that occur over time.

          13.2  CHANGE IN CORPORATE CONTROL. Subject to any provisions of then
outstanding Awards granting greater rights to the holders thereof, in the event
of a Change in Corporate Control (a) any then Restricted Stock shall Accelerate,
and (b) any then outstanding Options shall Accelerate. For the purposes of the
preceding sentence, (i) in the case of a Change in Corporate Control that is not
a Hostile Change in Corporate Control, the Board (and not the Compensation
Committee, notwithstanding the responsibilities assigned to the Compensation
Committee pursuant to Section 5) shall have the discretion to exclude any such
Change in Corporate Control from the application of the provisions of the
immediately preceding sentence, and (ii) in the case of a Hostile Change in
Corporate Control, a majority of the Incumbent Directors prior to such Hostile
Change in Corporate Control shall have the discretion to exclude any such Change
in Corporate Control from the application of the provisions of the immediately
preceding sentence. To the extent Options are not assumed, substituted or
replaced upon a Change in Corporate Control that is not a Hostile Change in
Corporate Control, the Board (and not the Compensation Committee,
notwithstanding the responsibilities assigned to the Compensation Committee
pursuant to Section 5) shall have the discretion to terminate such outstanding
Options to the extent not exercised prior to or simultaneously with such Change
in Corporate Control. Upon a Change in Corporate Control, each outstanding
Option will be appropriately adjusted simultaneously with such Change in
Corporate Control in accordance with Section 13.1.

          13.3  DISSOLUTION OR LIQUIDATION. Upon dissolution or liquidation of
the Company each outstanding Option shall terminate, but the Optionee (if at the
time in the employ of or otherwise associated with the Company or

<Page>

                                      -18-

any of its Subsidiaries) shall have the right, immediately prior to such
dissolution or liquidation, to exercise the Option to the extent exercisable on
the date of such dissolution or liquidation.

          13.4  RELATED MATTERS. Any adjustment in Awards made pursuant to this
Section 13 shall be determined and made, if at all, by the Compensation
Committee and shall include any correlative modification of terms, including of
Option Prices, Risks of Forfeiture and applicable repurchase prices for
Restricted Stock, which the Compensation Committee may deem necessary or
appropriate so as to ensure the rights of the Holders in their respective Awards
are not substantially diminished nor enlarged as a result of the adjustment and
corporate action other than as expressly contemplated in this Section 13. No
fraction of a share shall be purchasable or deliverable upon exercise, but in
the event any adjustment hereunder of the number of shares covered by an Award
shall cause such number to include a fraction of a share, such number of shares
shall be adjusted to the nearest smaller whole number of shares.

          14.   RESERVATION OF STOCK. The Company shall at all times during the
term of the Plan and, without duplication, of any outstanding Options reserve or
otherwise keep available such number of Shares as will be sufficient to satisfy
the requirements of the Plan (if not then terminated) and such outstanding
Options and shall pay all fees and expenses necessarily incurred by the Company
in connection therewith.

          15.   NO SPECIAL EMPLOYMENT OR OTHER RIGHTS. Any Stock issued pursuant
to Awards shall be subject to all restrictions upon the transfer thereof which
may be now or hereafter imposed by the Certificate of Incorporation, and the
By-laws of the Company, if any. Nothing contained in the Plan or in any Award
Agreement shall confer upon any recipient of an Award any right with respect to
the continuation of his or her employment or other association with the Company
(or any Subsidiary), or interfere in any way with the right of the Company (or
any Subsidiary), subject to the terms of any separate employment or consulting
agreement or provision of law or corporate articles or by-laws to the contrary,
at any time to terminate such employment, consulting or advisory relationship or
to increase or decrease the compensation of the recipient of an Award from the
rate in existence at the time of the grant of an Award.

          16.   TERMINATION AND AMENDMENT OF THE PLAN. The Board may at any time
terminate the Plan or make such modifications of the Plan as it shall deem
advisable. Any termination of the Plan shall not affect the terms of any Award
outstanding on the date of such termination. Unless the Board

<Page>

                                      -19-

otherwise expressly provides and except to the extent otherwise provided in the
next sentence, amendments of the Plan shall apply to all Awards outstanding on
the date of such amendments to the same extent as if such amendments had been in
effect at the time that each of such outstanding Awards were made or granted.
Notwithstanding the foregoing, no amendment of the Plan may, without the consent
of any recipient of an Award outstanding on the date of such amendment, (i)
reduce the number of shares of Stock subject to such Award, (ii) increase the
Option Price or the purchase price, as the case may be, of such Award, or (iii)
change the vesting schedule or the Risk of Forfeiture, as the case may be, of
such Award in a manner that adversely affects the rights of the recipient under
such Award. The Compensation Committee may amend the terms of any Award
theretofore granted, prospectively or retroactively, PROVIDED that the Award as
amended is consistent with the terms of the Plan, and PROVIDED, FURTHER, that no
such amendment of such Award may, without the consent of any recipient of such
Award hereunder, (x) reduce the number of shares of Stock subject to such Award,
(y) increase the Option Price or the purchase price, as the case may be, of such
Award, or (z) change the vesting schedule or the Risk of Forfeiture, as the case
may be, of such Award in a manner that adversely affects the rights of the
recipient under such Award.

          17.   NOTICES AND OTHER COMMUNICATIONS. All notices and other
communications required or permitted under the Plan shall be effective if in
writing and if delivered or sent by certified or registered mail, return receipt
requested (a) if to the Holder, at his or her residence address last filed with
the Company, and (b) if to the Company, at 65 Hayden Avenue, Lexington,
Massachusetts 02421, Attention: General Counsel or to such other persons or
addresses as the Holder or the Company may specify by a written notice to the
other from time to time. Copies of all notices sent to any Holder that is not
the recipient of an Award shall also be sent to the Holder in the manner set
forth in this Section 17.

          18.   EFFECTIVENESS. The Plan, originally called the 2000 Nonstatutory
Stock Option Plan, was originally adopted on December 15, 2000 by the Board. The
Plan was amended and restated by the Board on March 5, 2002, and the Plan, as so
amended and restated, was ratified and approved by the stockholders of the
Company on June 13, 2002.

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