Item 8.01 Other Events.

On July 6, 2009, the registrant, Cubist Pharmaceuticals, Inc., issued a press release announcing that it had begun dosing in CONSERV™-2, a Phase 2 clinical trial that will investigate ecallantide's effect on surgical blood loss volume in cardiac surgery patients who are on cardiopulmonary bypass and are at a high risk of bleeding. 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.

99.1 Press Release dated July 6, 2009

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