Ownership Submission
FORM 4
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

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934, Section 17(a) of the Public Utility Holding Company Act of 1935 or Section 30(h) of the Investment Company Act of 1940
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(Print or Type Responses)
1. Name and Address of Reporting Person *
PEREZ ROBERT J
  2. Issuer Name and Ticker or Trading Symbol
CUBIST PHARMACEUTICALS INC [CBST]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
__X__ Director _____ 10% Owner
__X__ Officer (give title below) _____ Other (specify below)
Chief Executive Officer
(Last)
(First)
(Middle)
65 HAYDEN AVENUE
3. Date of Earliest Transaction (Month/Day/Year)
01/21/2015
(Street)

LEXINGTON, MA 02421
4. If Amendment, Date Original Filed(Month/Day/Year)
6. Individual or Joint/Group Filing(Check Applicable Line)
_X_ Form filed by One Reporting Person
___ Form filed by More than One Reporting Person
(City)
(State)
(Zip)
Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1.Title of Security
(Instr. 3)
2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction 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 01/21/2015   J(1)(2)   47,325 D $ 102 0 D  
Common Stock 01/21/2015   J(1)(2)   5,012 D $ 102 0 I 401(k) Plan

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security
(Instr. 3)
2. Conversion or Exercise Price of Derivative Security 3. Transaction Date (Month/Day/Year) 3A. Deemed Execution Date, if any (Month/Day/Year) 4. Transaction 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
(Month/Day/Year)
7. Title and Amount of Underlying Securities
(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) $ 23.12 01/21/2015   D     25,000 11/15/2007(3) 08/15/2017 Common Stock 25,000 $ 0 0 D  
Stock Options (Right to Buy) $ 21.91 01/21/2015   D     50,000 12/14/2007(4) 09/14/2017 Common Stock 50,000 $ 0 0 D  
Stock Options (Right to Buy) $ 18.1 01/21/2015   D     40,000 05/15/2008(5) 02/15/2018 Common Stock 40,000 $ 0 0 D  
Stock Options (Right to Buy) $ 16.76 01/21/2015   D     62,500 08/15/2009(6) 05/15/2019 Common Stock 62,500 $ 0 0 D  
Stock Options (Right to Buy) $ 21.56 01/21/2015   D     75,000 08/14/2010(7) 05/14/2020 Common Stock 75,000 $ 0 0 D  
Restricted Stock Units (8) 01/21/2015   D     5,000 05/13/2012(8)   (8) Common Stock 5,000 $ 0 0 D  
Stock Options (Right to Buy) $ 34.795 01/21/2015   D     100,000 08/13/2011(9) 05/13/2021 Common Stock 100,000 $ 0 0 D  
Stock Options (Right to Buy) $ 42.09 01/21/2015   D     100,000 05/16/2012(10) 02/16/2022 Common Stock 100,000 $ 0 0 D  
Restricted Stock Units (8) 01/21/2015   D     10,000 02/16/2013(8)   (8) Common Stock 10,000 $ 0 0 D  
Stock Options (Right to Buy) $ 43.81 01/21/2015   D     25,000 11/15/2012(11) 08/15/2022 Common Stock 25,000 $ 0 0 D  
Restricted Stock Units (8) 01/21/2015   D     4,250 08/15/2013(8)   (8) Common Stock 4,250 $ 0 0 D  
Stock Options (Right to Buy) $ 41.6 01/21/2015   D     62,575 05/15/2013(12) 02/15/2023 Common Stock 62,575 $ 0 0 D  
Restricted Stock Units (8) 01/21/2015   D     7,662 02/15/2014(8)   (8) Common Stock 7,662 $ 0 0 D  
Performance Restricted Stock Units (13) 01/21/2015   D     10,216 02/15/2016(13)   (13) Common Stock 10,216 $ 0 0 D  
Stock Options (Right to Buy) $ 73.55 01/21/2015   D     57,599 05/14/2014(14) 02/14/2024 Common Stock 57,599 $ 0 0 D  
Restricted Stock Units (8) 01/21/2015   D     8,443 02/14/2015(8)   (8) Common Stock 8,443 $ 0 0 D  
Performance Restricted Stock Units (15) 01/21/2015   D     7,505 02/14/2017(15)   (15) Common Stock 7,505 $ 0 0 D  
Stock Options (Right to Buy) $ 66.68 01/21/2015   D     19,588 09/03/2014(16) 06/03/2024 Common Stock 19,588 $ 0 0 D  
Restricted Stock Units (8) 01/21/2015   D     2,624 06/03/2015(8)   (8) Common Stock 2,624 $ 0 0 D  
Performance Restricted Stock Units (17) 01/21/2015   D     2,624 06/03/2017(17)   (17) Common Stock 2,624 $ 0 0 D  
Restricted Stock Units (18) 01/21/2015   D     12,419 01/01/2016(18) 01/01/2025 Common Stock 12,419 $ 0 0 D  

Reporting Owners

Reporting Owner Name / Address Relationships
 Director  10% Owner  Officer  Other
PEREZ ROBERT J
65 HAYDEN AVENUE
LEXINGTON, MA 02421
  X     Chief Executive Officer  

Signatures

 CUBIST PHARMACEUTICALS, INC. By: /s/ Joseph L. Farmer - Attorney in fact   01/21/2015
**Signature of Reporting Person Date

Explanation of Responses:

* 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).
(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 $78.88 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 $80.09 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 $83.90 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
(6) 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.
(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 $80.44 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
(8) These restricted stock units, which vest 25% annually over a four-year period, with the first 25% vesting one year after the grant date, 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.
(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 $67.205 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
(10) 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.
(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 $58.19 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
(12) 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.
(13) 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.
(14) 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.
(15) 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.
(16) 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 $35.32 per Share, representing the difference between the exercise price of the options and $102.00 per Share.
(17) 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.
(18) These restricted stock units, which vest 6.25% quarterly 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.

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