FDA Advisory Committee Unanimously Recommends Approval of Cubist's SIVEXTRO™ (Tedizolid Phosphate) as Treatment for Serious Skin Infections

Lexington, Mass., March 31, 2014 – Cubist Pharmaceuticals, Inc. (NASDAQ: CBST) announced today that the U.S. Food and Drug Administration (FDA) Anti-Infective Drugs Advisory Committee (AIDAC) voted to recommend approval of Cubist's investigational antibiotic SIVEXTRO™ (tedizolid phosphate). In the unanimous 14 - 0 decision, the AIDAC found that substantial evidence of the safety and effectiveness of SIVEXTRO for the treatment of acute bacterial skin and skin structure infections (ABSSSI) was provided.

SIVEXTRO is a once daily oxazolidinone being developed for both intravenous (I.V.) and oral administration for the treatment of serious infections caused by certain Gram-positive bacteria, including those caused by methicillin-resistant Staphylococcus aureus (MRSA).  The Company's New Drug Application (NDA) submission to the FDA for SIVEXTRO is based on positive data from two global Phase 3 clinical studies, which met the primary and secondary endpoints defined by the FDA and European Medicines Agency (EMA).

"We are very pleased with the strong endorsement from AIDAC members, and recommendation of approval for tedizolid, now known in the U.S. as SIVEXTRO.  We are encouraged by the recognition that there is a need for more treatment options for patients to address serious skin infections," said Steven Gilman, Ph.D., Executive Vice President of Research and Development and Chief Scientific Officer of Cubist Pharmaceuticals. "We look forward to the FDA's final review of SIVEXTRO and decision."

The AIDAC recommendation is not binding on the FDA, but will help inform the FDA as it completes its Priority Review of the NDA for SIVEXTRO, which has an assigned action date of June 20, 2014.  More information about the AIDAC meeting is available on the FDA website here.

Additionally, the EMA recently accepted for review the Company's Marketing Authorization Application (MAA) for the investigational antibiotic, for which Cubist is seeking approval for the treatment of complicated skin and soft tissue infections (cSSTI). A decision from the European Commission (EC) is expected during the first half of 2015.

Tedizolid phosphate (formerly TR-701), now known in the U.S. as SIVEXTRO, is a novel oxazolidinone antibiotic drug candidate that is rapidly converted in vivo by phosphatases to the microbiologically active moiety TR-700. TR-700 acts by binding to the bacterial 50S ribosomal subunit thereby inhibiting protein synthesis. Tedizolid is being developed for both I.V. and oral administration in the potential treatment of ABSSSI, also referred to ascSSTI.  Tedizolid is also being investigated for potential use in nosocomial pneumonia (hospital-acquired bacterial pneumonia [HABP] and ventilator-associated bacterial pneumonia [VABP]).  Two Phase 3 studies, conducted in the U.S., Europe and other regions worldwide, in ABSSSI and cSSTI demonstrated that tedizolid 200 mg once daily for six days was statistically non-inferior to 10 days of linezolid 600 mg twice daily for the primary efficacy endpoints. Secondary endpoints were also met. In these studies, the adverse event rates were similar for both tedizolid and linezolid treated patients. Gastrointestinal adverse events (diarrhea, nausea and vomiting) were the most commonly reported in both treatment groups. 

About Serious Skin, Skin Structure and Soft Tissue Infections
Acute bacterial skin and skin structure infections (ABSSSI) are also referred to as complicated skin and soft tissue infections (cSSTI) (in Europe). These infections, which are a significant and growing problem throughout the world, involve deeper tissue or require surgical intervention (e.g., cellulitis, major cutaneous abscesses and infected wounds) or are associated with a significant underlying disease (e.g., diabetes or systemic immunosuppression) that complicates response to therapy. A variety of pathogens may be identified in ABSSSI/cSSTI but the two most common Gram-positive pathogens are Staphylococcus aureus and Streptococcus pyogenes. The significant increase in the incidence of methicillin-resistant Staphylococcus aureus (MRSA) healthcare-associated infections (HAIs), as well as community infections, has resulted in a need for therapies to address serious skin, skin structure and soft tissue infections that are effective against MRSA.

About MRSA
According to the U.S. Centers for Disease Control and Prevention (CDC) "Antibiotic resistance threats in the United States, 2013" report, each year more than two million Americans develop infections from antibiotic-resistant bacteria. One of the serious public health threats identified by the CDC is methicillin-resistant Staphylococcus aureus (MRSA), which continues to be a clinical and economic burden. Based on CDC data, there are approximately 80,000 severe MRSA infections and 11,000 deaths from MRSA in the U.S. per year.  The European Centre for Disease Prevention and Control (ECDC) estimates that more than four million European Union (EU) patients acquire healthcare acquired infections (HAIs) annually, resulting in 37,000 deaths and that a large proportion of these deaths are due to the most common multidrug-resistant bacteria, including MRSA. According to the ECDC, MRSA is still the most commonly identified antimicrobial-resistant pathogen in hospitals in many parts of the world, including Europe, the Americas, North Africa, the Middle East, and Asia.  Data from the Eurosurveillance journal estimates MRSA infections affect more than 150,000 patients annually in the EU. 

About Cubist's Commitment to Antibiotic R&D
Cubist has a growing commitment to global public health through its leadership in the R&D of antibiotics to treat serious and life-threatening infections caused by a broad range of increasingly resistant bacteria. The Company hopes to deliver at least four new antibiotics in support of the Infectious Diseases Society of America (IDSA) goal of 10 new antibiotics by 2020. Cubist expects to invest approximately $400M USD in 2014 on antibacterial R&D and approximately 75% of its employee base is focused on the research, development, commercialization and support of antibiotics.

About Cubist
Cubist Pharmaceuticals, Inc. is a global biopharmaceutical company focused on the research, development, and commercialization of pharmaceutical products that address significant unmet medical needs in the acute care environment. Cubist is headquartered in Lexington, Massachusetts, with a central international office located in Zurich, Switzerland. Additional information can be found at Cubist's web site at www.cubist.com.  Also, connect with Cubist on Twitter @cubistbiopharma and @cubistcareersLinkedIn, or YouTube.

Forward Looking Statements
This press release contains forward-looking statements. Any statements contained herein which do not describe historical facts, including but not limited to, statements regarding: positive results from Cubist's Phase 3 clinical studies of SIVEXTRO; the FDA's final review of and decision on our SIVEXTRO NDA submission, including that the AIDAC recommendation will help inform the FDA's review; the expected timing of the FDA's action date for our SIVEXTRO NDA submission and for the EC reaching a decision on our MAA for SIVEXTRO; the therapeutic potential of SIVEXTRO, including that we are developing SIVEXTRO for potential indications in ABSSSI/cSSTI, HABP and VABP; our aspirations to achieve a portion of the IDSA goal of 10 new antibiotics by 2020; and the level of our financial and personnel commitments towards antibiotic research, development and commercialization, are forward-looking statements which involve risks and uncertainties that could cause actual results to differ materially from those discussed in such forward-looking statements. Such risks and uncertainties include, among others: that the FDA's review and decision on our SIVEXTRO NDA submission may be affected by issues not discussed by the AIDAC and the FDA is not bound by and may not agree with the AIDAC's recommendation; regulatory developments in the U.S. and Europe, including the risk that the FDA, EMA, EC and other foreign regulatory authorities may not agree with our interpretation of the results from the clinical studies of SIVEXTRO, may not approve on a timely basis or at all, our marketing authorization applications for SIVEXTRO or may require additional data, analysis, information or further studies that may not be clinically feasible or financially practicable; the review of our marketing authorization applications may take longer than anticipated due to internal regulatory authority constraints; any marketing approval for SIVEXTRO may impose significant limitations on its use and additional post-marketing requirements; our ability to obtain adequate pricing and reimbursement levels for SIVEXTRO; our ability to successfully commercialize SIVEXTRO, including as a result of regulatory authorities' decisions regarding labeling and other matters, including adverse side effects, that could affect its availability or commercial potential; competitive risks from current and future therapeutic alternatives to SIVEXTRO; our ability to maintain and enforce intellectual property protection for SIVEXTRO; additional clinical trials of SIVEXTRO, including in HABP/VABP, may produce negative or inconclusive results or may not be initiated or conducted in a timely manner; technical difficulties or excessive costs relating to the manufacture or supply of SIVEXTRO, including our ability to work with our third party contract manufacturers that manufacture and supply SIVEXTRO on our behalf; our ability to work with, and the performance of our third party contract research organizations that help us conduct our clinical trials; we may encounter other unanticipated or unexpected risks with respect to the development or manufacture of SIVEXTRO; the fact that drug discovery and development is complex, time consuming, expensive and fraught with a high risk of failure; and those additional factors discussed in our most recent annual report on Form 10-K and quarterly report on Form 10-Q filed with the Securities and Exchange Commission. We caution investors not to place considerable reliance on the forward-looking statements contained in this press release. These forward-looking statements speak only as of the date of this document, and we undertake no obligation to update or revise any of these statements.