Exhibit
10.49  RESTRICTED STOCK UNIT AGREEMENT  CUBIST PHARMACEUTICALS, INC.  This
Restricted Stock Unit Agreement (the Agreement) governs the Award of
restricted stock units (RSUs) to employees (Participants) of Cubist
Pharmaceuticals, Inc. (the Company). 
The details of any RSU Award made to a Participant will be set forth in
aletter from the
Participants manager or other written communication from the Company (a
Notice).  In consideration of the premises and the mutual
covenants contained in this Agreement and for other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged,
the Company and the Participant agree as follows:  1.             Relationship to the Plan.  The Participant specifically understands and
agrees that the Award is being issued under the Companys Amended and Restated
Equity Incentive Plan (the Plan), a copy of which the Participant
acknowledges he or she has read and understands and by which Plan he or she
agrees to be bound.  The provisions of the
Plan are incorporated into this Agreement by reference.  Any terms used and not defined in this
Agreement have the meanings ascribed to such terms in the Plan.  2.             Grant of Award.Participants will be notified of their RSU Award through a Notice.  The Notice will contain, among other things,
the number of RSUs in the Award and the grant date of the Award.  The Award represents a contingent entitlement
of the Participant to receive shares of the Companys common stock, par value
$.001 per share (Common Stock).  3.             Vesting of Award.  Subject
to the terms and conditions set forth in this Agreement and the Plan, including
the potential impact of a Change
in Corporate Control upon the vesting
of the Award, the Award will vest annually on a pro rata basis over four years
from the grant date, provided that the Participant remains continuously
employed by the Company or a Subsidiary through the applicable vesting date.  On each
vesting date, the Participant will be entitled to receive such number of shares
of Common Stock equivalent to the number of RSUs that vest on the vesting date,
provided that the Participant is employed by the Company or a Subsidiary on
such vesting date.  Such shares of Common
Stock shall thereafter be delivered by the Company to the Participant in
accordance with this Agreement and the Plan and as required to comply with Section 409A
of the Code.  Notwithstanding the
foregoing, if the Participant is as of the vesting date a specified employee
(as defined under Section 409A of the Code) then such delivery of shares
of Common Stock, if required by Section 409A of the Code, will be made six
months after the date of a Separation from Service (as defined in Section 409A
of the Code).  4.             Forfeiture of the Award.  Except as otherwise set forth in this
Agreement or the Plan, if the Participant ceases to be employed for any reason
by the Company or a Subsidiary prior to a vesting date, then as of the date on
which the Participants employment terminates, all unvested RSUs subject to an
RSU Award shall immediately be forfeited to the Company.  5.             Prohibitions on Transfer and
Sale.Except as permitted by the Plan, an Award
shall not be assigned, pledged or transferred in any way (whether by operation
of law or otherwise) and shall not be subject to execution, attachment or
similar process.  Any attempted transfer,
assignment, pledge or other disposition of an Award or of any rights granted under
this Agreement that is contrary to the provisions of the Plan or this Section 4,
or the levy of any attachment or similar process upon an Award shall be null
and void.  Except as permitted by the
Plan, the shares of Common Stock to be issued pursuant to this Agreement shall
be issued, during the Participants lifetime, only to the Participant (or, in
the event of legal incapacity or incompetence, to the Participants guardian or
representative).


6.             Securities Law Compliance.  The Participantspecifically acknowledges and agrees
that any sales of shares of Common Stock issued hereunder shall be sold in accordance
with the requirements of the Securities Act of 1933, as amended.  7.             Rights as a Stockholder.  The Participant shall have no right as a
stockholder, including voting and dividend rights, until the Award vests in
accordance with Section 3 of this Agreement.  8.             Tax Liability of the Participant
and Payment of Taxes.  (a) The
Participant acknowledges and agrees that any income or other taxes due from the
Participant with respect to an Award or the shares of Common Stock to be issued
pursuant to this Agreement or otherwise sold shall be the Participants
responsibility.  (b) 
The Participant agrees that the Participant will owe taxes on each vesting date
on the portion of an Award that vests on the vesting date and, unless the
Participant elects to pay such taxes in cash in accordance with the procedure
described in Section 8(c), the Company shall beentitled to have the broker designated by the
Company sell on the Participants behalf a whole number of shares of Common
Stock from those shares issuable to you on each vesting date to generate cash
proceeds sufficient to satisfy the tax withholding obligations (including U.S.
federal, state and local taxes and any non-U.S. taxes or social contributions)
that the Company determines are or may be required in connection with such
event (referred to as Sell to Cover Taxes).  In the event of a Sell to
Cover Taxes, the Participant will be responsible for all brokers fees and
other costs of sale.  In addition, the broker will be instructed by the
Company to sell a sufficient number of whole shares of Common Stock to generate
cash proceeds equal to the tax withholding obligations described above. 
Neither the Company nor the broker used by the Company will guarantee any
particular sale price for the sale of such shares.  (c) 
In lieu of a Sell to Cover Taxes, the Participant may elect to pay the tax
withholding obligations described on Section 8(b) in cash if the
Participant completes the RSU tax election form (cash payment) to be
distributed to recipients of RSU Awards, returns the form to the Company
designated broker at least thirty (30) days prior to each vesting date, and
complies with all of the other instructions on the form.  9.             Participant Acknowledgements and
Authorizations.  The
Participant acknowledges the following:  (a)           The Company is not by the Plan, this
Agreement or an Award obligated to continue the Participants employment
relationship or consulting relationship with the Company or any Subsidiary.  (b)           The grant of an Award is considered a
one-time benefit and does not create a contractual or other right to receive
any other award under the Plan, benefits in lieu of such awards or any other
benefits in the future.  (c)           The Plan is a voluntary program of
the Company and future awards, if any, will be at the sole discretion of the
Company, including, but not limited to, the timing of any award, the amount of any
award, vesting provisions and purchase price, if any.  (d)           The value of an Award is an
extraordinary item of compensation outside of the scope of the Participants
employment.  As such, an Award is not
part of normal or expected compensation for purposes of calculating any
severance, resignation, redundancy, end of service payments, bonuses, long-term
service awards, pension or retirement benefits or similar payments.  The  2


future value of the
shares of Common Stock underlying the Award is unknown and cannot be predicted
with certainty.  (e)           The
Participant authorizes the Company to use and disclose to any agent
administering the Plan or providing recordkeeping services with respect to the
Plan with such information and data as the Company shall request in order to
facilitate the grant of an Award, the administration of an Award and the
administration of the Plan, and the Participant waives any data privacy rights
he or she may have with respect to such information or the sharing of such
information.  10.           Notices.  Any notices required or permitted by the
terms of this Agreement or the Plan shall be given by recognized courier
service, facsimile, registered or certified mail, return receipt requested,
addressed as follows:  If to the Company:  Cubist
Pharmaceuticals, Inc. 65 Hayden Avenue Lexington, MA 02421 Attn: General Counsel Fax: 
781-860-1407 Tel: 781-860-8660  If to the Participant at the
address set forth in the Companys records, or to such other address or
addresses of which notice in the same manner has previously been given.  Any such notice shall be deemed to have been
given on the earliest of receipt, one business day following delivery by the
sender to a recognized overnight courier service, or three business days
following mailing by registered or certified mail.  11.           Benefit of Agreement.  Subject to the provisions of the Plan and the
other provisions hereof, this Agreement shall be for the benefit of and shall
be binding upon the heirs, executors, administrators, successors and assigns of
the parties hereto.  12.           Governing Law.  This Agreement shall be construed and
enforced in accordance with the laws of the State of Delaware, without giving effect to the conflict of law
principles thereof.  For the purpose of
litigating any dispute that arises under this Agreement, whether at law or in
equity, the parties hereby consent to exclusive jurisdiction in the
Commonwealth of Massachusettsand
agree that such litigation shall be conducted in the state courts of
Massachusetts or the federal courts of the United States for the District of
Massachusetts.  13.           Severability.  If any provision of this Agreement is held to
be invalid or unenforceable by a court of competent jurisdiction, then such
provision or provisions shall be modified to the extent necessary to make such
provision valid and enforceable, and to the extent that this is impossible,
then such provision shall be deemed to be excised from this Agreement, and the
validity, legality and enforceability of the rest of this Agreement shall not
be affected thereby.  14.           Entire Agreement.  This Agreement, together with the Plan,
constitutes the entire agreement and understanding between the parties hereto
with respect to the subject matter hereof and supersedes all prior oral or
written agreements and understandings relating to the subject matter
hereof.  No statement, representation,
warranty, covenant or agreement not expressly set forth in this Agreement shall
affect or be used to interpret, change or restrict the express terms and
provisions of this Agreement provided, however, in any event, this Agreement
shall be subject to and governed by the Plan.  3


15.           Modifications and Amendments;
Waivers and Consents.  The terms and
provisions of this Agreement may be modified or amended as provided in the
Plan.  Except as provided in the Plan,
the terms and provisions of this Agreement may be waived, or consent for the
departure therefrom granted, only by written document executed by the party
entitled to the benefits of such terms or provisions.  No such waiver or consent shall be deemed to
be or shall constitute a waiver or consent with respect to any other terms or
provisions of this Agreement, whether or not similar.  Each such waiver or consent shall be
effective only in the specific instance and for the purpose for which it was
given, and shall not constitute a continuing waiver or consent.  16.           Company Signature; Participant
Electronic Acknowledgment.  An
authorized representative has signed the Agreement below.  By acknowledging your acceptance of the terms
of this Agreement through an electronic acknowledgment system established by
the Company or its agents, you agree to be bound by all of the terms of this
Agreement and the Plan.  The Award will
not become effective, and you will therefore have not rights to or in the
Award, until you acknowledge your acceptance of the terms of this Agreement in
the manner required by the Company.   CUBIST
  PHARMACEUTICALS, INC.By:Name:Title:  4