FORM 4
[ X ] Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).         
UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES
                                                                                  
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OMB Number: 3235-0287
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Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940
                      

1. Name and Address of Reporting Person *

GILMAN STEVEN C 		2. Issuer Name and Ticker or Trading Symbol

CUBIST PHARMACEUTICALS INC [ CBST ] 		5. Relationship of Reporting Person(s) to Issuer (Check all applicable)

_____ Director                      _____ 10% Owner
__ X __ Officer (give title below)      _____ Other (specify below)
EVP & Chief Scientific Officer
(Last)          (First)          (Middle)

65 HAYDEN AVENUE 		3. Date of Earliest Transaction (MM/DD/YYYY)

1/21/2015
(Street)

LEXINGTON, MA 02421
(City)        (State)        (Zip)
4. If Amendment, Date Original Filed (MM/DD/YYYY)

 
6. Individual or Joint/Group Filing (Check Applicable Line)

_ X _ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3) 		2. Trans. Date 2A. Deemed Execution Date, if any 3. Trans. Code
(Instr. 8) 		4. Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5) 		5. Amount of Securities Beneficially Owned Following Reported Transaction(s)
(Instr. 3 and 4) 		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V Amount (A) or (D) Price
Common Stock   1/21/2015     J (1) (2)    27680   D $102.00   0   D    
Common Stock   1/21/2015     J (1) (2)    2851   D $102.00   0   D    

Table II - Derivative Securities Beneficially Owned ( e.g. , puts, calls, warrants, options, convertible securities)
1. Title of Derivate Security
(Instr. 3) 		2. Conversion or Exercise Price of Derivative Security 3. Trans. Date 3A. Deemed Execution Date, if any 4. Trans. Code
(Instr. 8) 		5. Number of Derivative Securities Acquired (A) or Disposed of (D)
(Instr. 3, 4 and 5) 		6. Date Exercisable and Expiration Date 7. Title and Amount of Securities Underlying Derivative Security
(Instr. 3 and 4) 		8. Price of Derivative Security
(Instr. 5) 		9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4) 10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4) 11. Nature of Indirect Beneficial Ownership (Instr. 4)
Code V (A) (D) Date Exercisable Expiration Date Title Amount or Number of Shares
Stock Options (Right to Buy)   $16.76   1/21/2015     D         1000    8/15/2009   (3) 5/15/2019   Common Stock   1000   $0.00   0   D    
Stock Options (Right to Buy)   $21.56   1/21/2015     D         60000    8/14/2010   (4) 5/14/2020   Common Stock   60000   $0.00   0   D    
Stock Options (Right to Buy)   $25.23   1/21/2015     D         9375    1/15/2011   (5) 10/15/2020   Common Stock   9375   $0.00   0   D    
Restricted Stock Units     (6) 1/21/2015     D         3500    5/13/2012   (6)   (6) Common Stock   3500   $0.00   0   D    
Stock Options (Right to Buy)   $34.795   1/21/2015     D         21875    8/13/2011   (7) 5/13/2021   Common Stock   21875   $0.00   0   D    
Stock Options (Right to Buy)   $42.09   1/21/2015     D         75000    5/16/2012   (8) 2/16/2022   Common Stock   75000   $0.00   0   D    
Restricted Stock Units     (6) 1/21/2015     D         7500    2/16/2013   (6)   (6) Common Stock   7500   $0.00   0   D    
Stock Options (Right to Buy)   $41.60   1/21/2015     D         47851    5/15/2013   (9) 2/15/2023   Common Stock   47851   $0.00   0   D    
Restricted Stock Units     (6) 1/21/2015     D         5859    2/15/2014   (6)   (6) Common Stock   5859   $0.00   0   D    
Performance Restricted Stock Units     (10) 1/21/2015     D         7812    2/15/2016   (10)   (10) Common Stock   7812   $0.00   0   D    
Stock Options (Right to Buy)   $73.55   1/21/2015     D         31053    5/14/2014   (11) 2/14/2024   Common Stock   31053   $0.00   0   D    
Restricted Stock Units     (6) 1/21/2015     D         4552    2/14/2015   (6)   (6) Common Stock   4552   $0.00   0   D    
Performance Restricted Stock Units     (12) 1/21/2015     D         4046    2/14/2017   (12)   (12) Common Stock   4046   $0.00   0   D    

Explanation of Responses:
( 1)  On January 21, 2015, Mavec Corporation, a Delaware corporation ("Purchaser") and a wholly-owned subsidiary of Merck & Co., Inc., a New Jersey corporation ("Parent") merged with and into (the "Merger") Cubist Pharmaceuticals, Inc., a Delaware corporation ("Cubist"), without a meeting of the stockholders of Cubist in accordance with Section 251(h) of the General Corporation Law of the State of Delaware, with Cubist continuing as the surviving corporation and thereby becoming a wholly-owned subsidiary of Parent. The Merger took place pursuant to an Agreement and Plan of Merger (the "Merger Agreement"), dated December 8, 2014, among Parent, Purchaser and Cubist.
( 2)  Each outstanding share of Cubist common stock, par value $0.001 per share (the "Shares") (other than Shares held in the treasury of Cubist and each Share owned by Parent, Purchaser or any direct or indirect wholly owned Subsidiary of Parent or Purchaser, which Shares were cancelled and retired without any conversion thereof), including the Shares reported above, were automatically cancelled and converted in to the right to receive $102.00 per Share, net to the seller in cash, without interest, but subject to any required withholding of taxes.
( 3)  These options, which vest 6.25% quarterly over a four-year period, were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $85.24 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
( 4)  These options, which vest 6.25% quarterly over a four-year period, were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $80.44 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
( 5)  These options, which vest 6.25% quarterly over a four-year period, were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $76.77 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
( 6)  These restricted stock units, which vest 25% annually over a four-year period, were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $102.00 per Share. Each restricted stock unit represented a contingent right to receive one share of Cubist common stock for no consideration. The restricted stock units do not expire.
( 7)  These options, which vest 6.25% quarterly over a four-year period, were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $67.205 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
( 8)  These options, which vest 6.25% quarterly over a four-year period, were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $59.91 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
( 9)  These options, which vest 6.25% quarterly over a four-year period, were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $60.40 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
( 10)  These performance restricted stock units were granted in 2013. Shares are earned based on the achievement of certain performance conditions, which are set forth in the applicable performance unit agreement. Pursuant to the Merger Agreement, such performance conditions were deemed to be achieved such that 100% of the Shares subject to performance restricted stock units granted in 2013 were earned. These performance restricted stock units were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $102.00 per Share. Each performance restricted stock unit represents a contingent right to receive one share of Cubist common stock for no consideration. Performance restricted stock units do not expire.
( 11)  These options, which vest 6.25% quarterly over a four-year period, were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $28.45 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
( 12)  These performance restricted stock units were granted in 2014. Shares are earned based on the achievement of certain performance conditions, which are set forth in the applicable performance unit agreement. Pursuant to the Merger Agreement, such performance conditions were deemed to be achieved such that 83.33% of the maximum number of Shares deliverable under performance restricted stock units granted in 2014 were earned. These performance restricted stock units were cancelled pursuant to the Merger Agreement in exchange for a cash payment of $102.00 per Share. Each performance restricted stock unit represents a contingent right to receive one share of Cubist common stock for no consideration. Performance restricted stock units do not expire.

Reporting Owners
Reporting Owner Name / Address
Relationships
Director 10% Owner Officer Other
GILMAN STEVEN C
65 HAYDEN AVENUE
LEXINGTON, MA 02421

EVP & Chief Scientific Officer

Signatures
CUBIST PHARMACEUTICALS, INC. By: /s/ Joseph L. Farmer - Attorney in fact 1/21/2015
** Signature of Reporting Person Date


Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4(b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
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