Cubist Pharmaceuticals, Inc. (NASDAQ: CBST) today announced that the U.S. Food and Drug Administration (FDA) has designated two of the company’s Phase 3 antibiotic candidates, CXA-201 (ceftolozane/tazobactam) and CB-315, as Qualified Infectious Disease Products (QIDP). The QIDP designations will enable Cubist to benefit from certain incentives for the development of new antibiotics, including priority review, eligibility for fast-track status, and if CXA-201 or CB-315 are ultimately approved by the FDA, a five year extension of Hatch-Waxman exclusivity. These incentives are provided under the Generating Antibiotic Incentives Now Act (GAIN Act), which received strong bipartisan support in Congress and was signed into law by President Obama in July 2012 as part of the FDA Safety and Innovation Act (FDASIA), the fifth authorization of the Prescription Drug User Fee Act. CXA-201 is currently being studied in pivotal Phase 3 trials as a first-line intravenous therapy for the treatment of complicated intra-abdominal infections and complicated urinary tract infections caused by Gram-negative bacterial infections, including those caused by multi-drug resistant Pseudomonas aeruginosa. The FDA’s QIDP designation applies to CXA-201’s treatment of complicated intra-abdominal infections. CB-315 is currently being investigated in Phase 3 trials as an oral therapy for Clostridium difficile-associated diarrhea, or CDAD. “We are delighted that both of our Phase 3 antibiotic candidates, ceftolozane/tazobactam and CB-315, have received QIDP designation under the GAIN Act,” said Cubist’s Chief Scientific Officer Steve Gilman. “With antibiotic resistance rates on the rise and many companies having already left antibiotic R&D altogether, we believe the provisions of the bipartisan GAIN Act are a critical first step in our country’s efforts to spur meaningful investment into this space.” About The GAIN Act The GAIN Act, Title VIII (Sections 801 through 806) of the FDASIA, provides pharmaceutical and biotechnology companies with incentives to develop new antibacterial and antifungal drugs for the treatment of life-threatening infectious diseases caused by drug resistant pathogens. Qualifying pathogens are defined by the GAIN Act to include multi-drug resistant Gram-negative bacteria, including Pseudomonas, Acinetobacter, Klebsiella, and Escherichia coli species; resistant Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin-resistant Staphylococcus aureus and vancomycin-resistant Enterococcus; multi-drug resistant tuberculosis; and Clostridium difficile. About Gram-negative bacteria The diseases caused by Gram-negative bacteria include intra-abdominal infections, urinary tract infections, pneumonia, peritonitis, septicemia, neonatal meningitis, and burn and wound infections. In the US in 2003, Gram-negative bacteria were associated with many of the most frequent types of hospital-acquired infections including 71% of urinary tract infections, 65% of pneumonia episodes, 34% of surgical site infections, and 24% of bloodstream infections. Important Gram-negative bacteria include Pseudomonas, Escherichia coli, Klebsiella, and Acinetobacter. About CDAD CDAD is a disease caused by an overgrowth of, and toxin production by C. difficile, a Gram-positive bacterium naturally found in the lower gastrointestinal tract. This overgrowth is caused by the use of antibiotics for the treatment of common community and hospital acquired infections. Many antibiotics cure the underlying infection but, as a consequence, disrupt the natural balance of intestinal bacteria which allows C. difficile to overgrow. The overgrown C. difficile bacteria produce enterotoxin and cytotoxin, two proteins that can lead to potentially life-threatening severe diarrhea and sepsis (blood infection). CDAD rates and severity are increasing, due in part to the spread of a new strain with increased virulence and greater resistance to fluoroquinolones, a standard of care treatment. According to an article in the October 2008 issue of the New England Journal of Medicine, during the mid- and late-1990s, the reported incidence of C. difficile infections in acute care hospitals in the United States remained stable at 30 to 40 cases per 100,000. However in 2001, this number rose to almost 50, with subsequent increases to the point that the number of cases that were reported in 2005 (84 per 100,000) was nearly three times the 1996 rate (31 per 100,000). About Cubist Cubist Pharmaceuticals, Inc. is a 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, Mass. Additional information can be found at Cubist’s web site at www.cubist.com. Cubist Safe Harbor Statement This press release includes forward-looking statements, including, without limitation, statements regarding: (i) the anticipated favorable impact resulting from the FDA’s designating CXA-201 and CB-315 as a QIDP, including the five year extension of Hatch-Waxman exclusivity if CXA-201 or CB-315 is ultimately approved by the FDA and (ii) the clinical development of CXA-201. Each forward-looking statement is subject to risks and uncertainties that could cause actual results to differ materially from those expressed or implied by such statement. Applicable risks and uncertainties include, among others: clinical trials of CXA-201 and CB-315 may not be successful or initiated or conducted in a timely manner and the timing of initiation and conduct of subsequent trials is dependent on our ability to successfully work with regulatory authorities, including the FDA on the design of the trials, among other things; we plan to rely, to a significant extent, on third party clinical research organizations, or CROs, to help us conduct clinical trials so the success and timing of these trials is dependent our ability to work with such CROs and their performance; technical difficulties or excessive costs relating to the manufacture or supply of CXA-201 and CB-315; we plan to rely, to a significant extent, on third party contract manufacturers and suppliers to manufacture and supply CXA-201 and CB-315 on our behalf so our ability to obtain adequate supplies of CXA-201 and CB-315 is dependent on our ability to work with such third parties and on their performance; we may encounter other unanticipated or unexpected risks with respect to the development or manufacture of CXA-201 and CB-315; and those additional factors discussed in Item 1A of our quarterly report on Form 10-Q for the period ended September 30, 2012 under the caption "Risk Factors" as filed with the Securities and Exchange Commission on November 5, 2012. 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.