Cubist Investor Relations

Building Long-term Shareholder Value

• Optimizing CUBICIN^® (daptomycin for injection)
• Expanding product portfolio
• Exercising strong financial discipline

Cubist Pharmaceuticals, Inc. (NASDAQ: CBST) is a biopharmaceutical company focused on the research, development and commercialization of products that address unmet medical needs in the acute care environment. Our historically successful IV antibiotic CUBICIN^® (daptomycin for injection) serves as the strategic and operational foundation for building shareholder value. Cubist anticipates that CUBICIN will achieve peak sales of > $1 billion annually in the U.S.

What's next for Cubist?

Cubist is moving forward confidently and successfully as an acute care-focused therapeutics company. We made marked progress over the past year as we continue to leverage the capabilities and infrastructure we have built. The steps we have taken have all been made with a focus on growing long term shareholder value.

As reported on April 14, 2011:

• Total net revenues for 1Q11 increased 13% to $162.5 million compared to $144.1 million in 1Q10. This increase in revenues was primarily attributable to Cubist's net sales of CUBICIN in the U.S., which increased 14% to $153.7 million in 1Q11, from $135.3 million in 1Q10.
• 1Q11 GAAP net income was $22.6 million, or $0.38 and $0.34 per basic and diluted share, respectively, as compared to $20.4 million, or $0.35 and $0.34 per basic and diluted share, respectively, for 1Q10. Cubist’s 1Q11 non-GAAP net income increased $5.7 million as compared to 1Q10 to $41.3 million, or $0.70 and $0.55 per basic and diluted share, respectively.
• As of March 31, 2011, Cubist had $915.8 million in cash, cash equivalents and investments.
• We continue to invest in our advancing clinical pipeline, and 2011 is a year in which we expect significant pipeline milestones.
  • CXA-201 -- A novel cephalosporin/tazobactam combination product (combination of CXA-101 and tazobactam) being developed for the treatment of infections due to drug-resistant Pseudomonas aeruginosa and other Gram-negative pathogens:
    • We expect to complete Phase 2 CXA-201 cIAI (complicated intra-abdominal infection trial) later this year
    • By year-end, we expect to initiate Phase 3 trials for CXA-201 in cUTI (complicated urinary tract infections) and cIAI
    • Remain on track with clinical plan, which, assuming success, will allow for an NDA filing for 2 indications by YE 2013
  • CB-183,315 -- A potent, oral, bactericidal lipopeptide being developed for the treatment of Clostridium difficile-associated diarrhea (CDAD):
    • Phase 2 dose-ranging trial continues to enroll and is on pace to complete later this year
    • Expect to make go/no-go decision on Phase 3 before year end
• Cubist is working on several pre-clinical programs, addressing areas of significant medical need. These include therapies to treat various serious bacterial infections, and agents to treat acute pain.