Cubist Pharmaceuticals Announces Second Quarter 2009 Earnings Call

LEXINGTON, Mass. -- Cubist Pharmaceuticals, Inc. (NASDAQ: CBST) today announced that it will issue its second quarter 2009 financial results at 4:00 p.m. ET on Thursday, July 16th, 2009, one day earlier than previously indicated. In connection with this announcement, Cubist will host a conference call and live audio webcast (with slides) at 5:00 p.m. ET that same day to discuss its second quarter financial results, business activities, and financial outlook.

As always, the quarterly earnings call will be available via phone and webcast. The phone call dial-in information is listed below. To access the webcast, please log on to the Cubist website at cubist.com at least 15 minutes prior to the start of the call to ensure adequate time for any software downloads that may be required.

A replay of the webcast and teleconference will be available on Cubist's website beginning approximately three hours after the call.

**************CONFERENCE CALL & WEBCAST INFORMATION****************

Cubist Pharmaceuticals to announce Q209 Financial Results

Thursday, July 16th, 2009

Earnings Conference Call & Webcast at 5:00 pm ET

Cubist will host a conference call and live audio webcast to discuss its second quarter 2009

financial results, business activities and financial outlook.

Participant Dial-In Numbers:

Live Participant Dial In (Toll Free): 877-407-8289

Live Participant Dial In (International): 201-689-8341

Dial-In # for Replay Access: (Toll Free) 877-660-6853 (International) 201-612-7415

Replay Passcodes (both required for playback):

Acct #: 351 Conference ID: 326755

For more information: http://www.investorcalendar.com/IC/CEPage.asp?ID=146838

CALL WILL ALSO BE BROADCAST LIVE, LISTEN ONLY, VIA THE WEB AT: www.cubist.comReplay will be available for 30 days at www.cubist.com

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About Cubist

Cubist Pharmaceuticals, Inc. is a biopharmaceutical company focused on the research, development, and commercialization of pharmaceutical products that address unmet medical needs in the acute care environment. In the U.S., Cubist markets CUBICIN(R) (daptomycin for injection), the first antibiotic in a new class of anti-infectives called lipopeptides. In July 2008, Cubist began promoting MERREM(R) I.V. (meropenem for injection) in the United States. MERREM is an established broad spectrum antibiotic developed by AstraZeneca. The Cubist product pipeline includes ecallantide, a recombinant human protein in Phase 2 clinical trials -- CONSERV(TM)-1 and CONSERV(TM)-2 -- for the reduction of blood loss during cardiothoracic surgery, and two Phase 1 programs that address unmet medical needs, one in CDAD (Clostridium difficile-associated diarrhea) and the other in multi-drug resistant (MDR) Gram-negative infections. In addition, the Company, in collaboration with Alnylam Pharmaceuticals, Inc. (Cambridge, MA), has a pre-IND and a Phase 2 program underway in novel treatments for respiratory syncytial virus infections using Alnylam's RNA-interference technology. Cubist is headquartered in Lexington, MA. Additional information can be found at Cubist's web site at www.cubist.com.

Cubist and CUBICIN are registered trademarks of Cubist Pharmaceuticals, Inc.

AstraZeneca and MERREM are registered trademarks of the AstraZeneca group of companies.

Contact: Cubist Pharmaceuticals, Inc. Eileen C. McIntyre, 781-860-8533 Senior Director, Corporate Communications eileen.mcintyre@cubist.com or Weber Shandwick Tara Murphy, 617-520-7045 tmurphy@webershandwick.com