Optimer Pharmaceuticals and Astellas Receive Positive Opinion from CHMP for European Approval of DIFICID™

SAN DIEGO, Sept. 23, 2011 /PRNewswire/ -- Optimer Pharmaceuticals, Inc. (NASDAQ: OPTR) today announced that the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) has adopted a positive opinion for DIFICLIR™ (fidaxomicin) tablets for the treatment of adults suffering with a Clostridium difficile infection (CDI), also known as C. difficile-associated diarrhea (CDAD).

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DIFICLIR, which is known as DIFICID™ in the United States (US), was approved by the US FDA in May 2011 for the treatment of CDAD in adults 18 years of age and older. Astellas is Optimer's exclusive licensee to develop and commercialize DIFICLIR in Europe and certain other countries in the Middle East, Africa and the Commonwealth of Independent States.

The CHMP positive opinion is based on Phase 3 clinical studies that were conducted to compare the safety and efficacy of 400mg/day fidaxomicin with 500mg/day oral vancomycin for 10 days in subjects with CDI. The first Phase 3 study was carried out in 629 subjects in North America (US and Canada). The second Phase 3 study was carried out in 535 subjects in North America and Europe. The results of the studies showed that the proportion of subjects in which clinical cure was achieved at the end of 10 days of treatment were similar for both treatments; thus fidaxomicin met its primary endpoint of non-inferiority to vancomycin. Furthermore in both trials, fidaxomicin had a significantly lower rate of recurrence of CDI compared to vancomycin at 30 days after completion of treatment.

"A positive CHMP opinion is an important milestone for Optimer and is a key step to making fidaxomicin more widely available to patients around the globe for this serious disease," said Pedro Lichtinger, President and CEO of Optimer.

The European Commission generally follows the recommendations of the CHMP and delivers its final decision within three months of the CHMP opinion.

Important Safety Information for DIFICID

• DIFICID should not be used for systemic infections
• Only use DIFICID for infection proven or strongly suspected to be caused by C. difficile. Prescribing DIFICID in the absence of a proven or strongly suspected C. difficile infection is unlikely to provide benefit to the patient and increases the risk of the development of drug resistant bacteria
• The most common adverse reactions are nausea (11%), vomiting (7%), abdominal pain (6%), gastrointestinal hemorrhage (4%), anemia (2%), and neutropenia (2%)

About CDAD

Clostridium difficile-associated diarrhea (CDAD) has become a significant medical problem in hospitals, long-term care facilities and in the community. CDAD is a serious illness resulting from infection of the inner lining of the colon by C. difficile bacteria, which produce toxins that cause inflammation of the colon, severe diarrhea and, in the most serious cases, death. Patients typically develop CDAD from the use of broad-spectrum antibiotics that disrupt normal gastrointestinal (gut) flora, possibly allowing C. difficile bacteria to flourish. Older patients in particular are at risk for CDAD, potentially because of a weakened immune system or the presence of underlying disease. Approximately two-thirds of CDAD patients are 65 years of age or older.

About Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing innovative hospital specialty products that have a positive impact on society. Optimer developed and is commercializing DIFICID™ (fidaxomicin) tablets, an FDA-approved antibacterial drug for the treatment of adult patients 18 years of age and older with Clostridium difficile-associated diarrhea (CDAD). Optimer's clinical pipeline includes Pruvel™, a product in the fluoroquinolone class of antibiotics that has completed Phase 3 trials as a treatment for infectious diarrhea. Additional information can be found at http://www.optimerpharma.com.

Forward-Looking Statements

Statements included in this release that are not a description of historical facts are forward-looking statements, including without limitation statements related to the potential regulatory approval of DIFICLIR in the EU, whether the EMA and other regulatory authorities will follow the opinion of the CHMP, the expected timing of a decision on the DIFICLIR MAA filing and the potential availability of DIFICLIR to European CDI patients.  Words such as "believes," "would," "anticipates," "plans," "expects," "may," "intend," "will," and similar expressions are intended to identify forward-looking statements. The inclusion of forward-looking statements should not be regarded as a representation by Astellas or Optimer that any of their plans will be achieved. Actual results may differ materially from those set forth in this release due to the risks and uncertainties inherent in Astellas' and Optimer's businesses including, without limitation, risks relating to: whether regulatory authorities will review or approve  applications for marketing approval within anticipated timelines or at all, Astellas' ability to successfully commercialize DIFICLIR, if approved, whether DIFICLIR will receive reimbursement from government authorities and other healthcare payors, and other risks detailed in Optimer's filings with the U.S. Securities and Exchange Commission.

Contacts
Optimer Pharmaceuticals, Inc.
David Walsey, Vice President, Investor Relations and Corporate Communications
858-909-0736

Canale Communications, Inc.
Jason I. Spark, Senior Vice President
619-849-6005

SOURCE Optimer Pharmaceuticals, Inc.

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