Cubist Pharmaceuticals Receives Two Sbir Grants for Lipopeptide Research; Company Could Receive Almost $500,000.

Business Editors/High-Tech Writers

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LEXINGTON, Mass.--(BUSINESS WIRE)--July 29, 2003

Cubist Pharmaceuticals, Inc. (Nasdaq: CBST) today announced that it has recently been awarded two Phase I Small Business Innovation Research (SBIR) grants that could total almost $500,000 should all funding be received from the National Institutes of Health (NIH). To date, Cubist has been awarded over $4.25 million in SBIR grants.

Both grants focus on Cubist's research on lipopeptides, a new class of compounds that may prove to be a source of additional antiinfective medicines. Cubist's lead investigational antibiotic Cidecin(R) (daptomycin for injection) is a member of this new class and a natural product of the fermentation of the bacterium Streptomyces roseosporus. The New Drug Application for CIDECIN is currently being reviewed by the U.S. Food & Drug Administration under priority review status with an action date of September 20, 2003.

The first SBIR grant, entitled "Modification of Daptomycin by Combinatorial Biosynthesis," will help support an ongoing project to rapidly manipulate the gene cluster responsible for the synthesis of daptomycin. The company is performing biosynthetic modification of the daptomycin molecule to determine if analogues can be identified with broad spectra of bactericidal (bacteria killing) activity and more potent activity against specific resistant species.

The second SBIR grant, entitled "Structure Activity Relationships Around Lipopeptides," will facilitate the exploration of the structure activity relationships around cyclic lipopeptide antibiotics. Cubist scientists will couple the use of more traditional methods of chemical synthesis of lipopeptides with biosynthetic techniques of swapping entire subunits responsible for the production of other lipopeptides in an attempt to create novel hybrid molecules with antibacterial activity.

Richard H. Baltz, Ph.D., Executive Director of Research at Cubist, commented on the grants: "Since the beginning of this year, our research efforts have focused on refining and advancing our natural product drug discovery technologies. We believe these government grants recognize the value of continuing these innovative programs, and we hope to continue to build our antiinfective franchise through the exploration of new molecular entities."

About Cubist

Cubist Pharmaceuticals, Inc. is a biopharmaceutical company focused on the research, development and commercialization of antiinfective drugs. Cubist has submitted a New Drug Application (NDA) to the U.S. Food & Drug Administration (FDA) for Cidecin(R) (daptomycin for injection) for the treatment of complicated skin and skin structure infections. The NDA for CIDECIN is currently being reviewed by the FDA under priority review status. Cubist's pipeline includes CAB-175, a next-generation parenteral cephalosporin antibiotic in Phase 1 trials, and an oral version of ceftriaxone (OCTX), a broad-spectrum cephalosporin antibiotic in pre-clinical development. Cubist is headquartered in Lexington, MA.

Cubist Safeharbor Statement

Statements contained herein that are not historical fact may be forward-looking statements within the meaning of Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934, that are subject to a variety of risks and uncertainties. There are a number of important factors that could cause actual results to differ materially from those projected or suggested in any forward-looking statements made by the Company. These factors include, but are not limited to: (i) the Company's ability to successfully complete product research and development, including pre-clinical and clinical studies and commercialization; (ii) the Company's ability to obtain required governmental approvals; (iii) the Company's ability to attract and/or maintain manufacturing, sales, distribution and marketing partners; (iv) the Company's ability to develop and commercialize its products before its competitors; and (v) the Company's ability to finance its operations. Additional factors that would cause actual results to differ materially from those projected or suggested in any forward-looking statements are contained in the Company's filings with the Securities and Exchange Commission, including those factors discussed under the caption "Risk Factors" in the Company's recent SEC filings.

Cidecin is a registered trademark of Cubist Pharmaceuticals, Inc.

Additional information can be found at the Company's web site at www.cubist.com