SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, DC 20549

FORM 8-K

CURRENT REPORT

PURSUANT TO SECTION 13 OR 15(D) OF THE

SECURITIES EXCHANGE ACT OF 1934

Date of Report (Date of earliest event reported):  February 9, 2012

CUBIST PHARMACEUTICALS, INC.

(Exact Name of Registrant as Specified in Charter)

65 Hayden Avenue, Lexington, Massachusetts  02421

(Address of Principal Executive Offices) (Zip Code)

Registrant’s telephone number, including area code:  (781) 860-8660

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

o    Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

o    Soliciting material pursuant to Rule 14a-12(b) under the Exchange Act (17 CFR 240.14a-12(b))

o    Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

o    Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Item 8.01 Other Events.

On February 9, 2012, the registrant, Cubist Pharmaceuticals, Inc. (“Cubist”), issued a press release announcing that it had received a Paragraph IV Notice Letter from Hospira, Inc. (“Hospira”) notifying Cubist that Hospira had submitted an Abbreviated New Drug Application (“ANDA”) to the U.S. Food and Drug Administration for approval to market a generic version of CUBICIN® (daptomycin for injection).  In the press release, Cubist also announced that it plans to file a patent infringement lawsuit against Hospira in response to the ANDA filing.  A copy of the press release has been filed as Exhibit 99.1 to this Current Report on Form 8-K and is incorporated herein by reference.

Item 9.01 Financial Statements and Exhibits.

(d)          Exhibits.

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SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

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