Optimer Pharmaceuticals Completes New Drug Application for Fidaxomicin

Optimer Pharmaceuticals, Inc.announced that it has completed the submission of its New Drug Application (NDA) to the U.S. Food and Drug Administration (FDA) for fidaxomicin to treat patients with Clostridium difficile infection (CDI) and to prevent recurrences of CDI. It is the most common cause of diarrhea in the hospital, and according to the CDC contributes to 15,000-30,000 deaths each year, a number that surpasses Methicillin-resistant Staphylococcus aureus (MRSA). Pedro Lichtinger, President and CEO of Optimer said, This NDA filing is one of the most significant achievements in the history of Optimer. This submission is the culmination of many years of dedicated work by the Optimer team, as well as the efforts of our clinical trial investigators and advisors to bring this much needed therapy to CDI patients. We believe fidaxomicin represents a major advance in CDI treatment, and every step we move closer to the possibility of it reaching patients is meaningful to those who are impacted by the disease.

Optimer has also requested priority review, which if granted could lead to an approval decision from the FDA in the second quarter of 2011. Fidaxomicin received Fast Track designation from the FDA in 2003 for the treatment of CDI, which allowed the Company to initiate a rolling NDA submission.

In August 2010, the Company’s Marketing Authorization Application (MAA) filing for fidaxomicin was accepted for review by the European Medicines Agency.

About Fidaxomicin

Fidaxomicin is the first in a new class of antibiotics called macrocycles, which inhibit the bacterial enzyme RNA polymerase, resulting in the rapid killing of C. difficile. The narrow-spectrum profile of fidaxomicin eradicates C. difficile selectively with minimal disruption to the normal intestinal flora, while the alternative antibiotics used to treat CDI, metronidazole and vancomycin, have been shown to disrupt the gut flora. Fidaxomicin facilitates the return of normal physiological conditions in the colon which may be responsible for reducing CDI recurrence. Optimer has filed applications in the U.S. and the EU for marketing authorization for fidaxomicin for the treatment of CDI and for the prevention of recurrences.

About Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing hospital specialty products to treat serious infections and address unmet medical needs. Optimer has two anti-infective product candidates in development, Fidaxomicin and Pruvel™ (prulifloxacin). Fidaxomicin is a narrow spectrum antibiotic being developed for the treatment of Clostridium difficile infection (CDI). The Company has submitted an NDA to the FDA, and filed a MAA with the EMA (Europe) for fidaxomicin. Pruvel™ is a prodrug in the fluoroquinolone class of antibiotics being developed as a treatment for infectious diarrhea. Additional information can be found at http://www.optimerpharma.com.