Optimer Pharmaceuticals Completes Enrollment in Second Fidaxomicin Phase 3 Clinical Trial in Patients With Clostridium difficile

Optimer Pharmaceuticals Completes Enrollment in Second Fidaxomicin Phase 3 Clinical Trial in Patients With Clostridium difficile Infection

SAN DIEGO, Nov. 12 /PRNewswire-FirstCall/ -- Optimer Pharmaceuticals, Inc. (Nasdaq: OPTR) today announced that it has completed enrollment in the second of two pivotal Phase 3 clinical trials evaluating the safety and efficacy of fidaxomicin (OPT-80) for the treatment of Clostridium difficile infection, or CDI.

"Completing enrollment in the second Phase 3 trial is a major milestone in the development of fidaxomicin. The two fidaxomicin trials combined represent the largest CDI database in the world, and will be an important tool for the medical community in understanding the epidemiology of this infection," said Michael N. Chang, Ph.D., President and CEO of Optimer. "We will complete the analysis of the data from this trial and we expect to report top-line results in the first quarter of 2010."

The Company previously reported positive data from the first Phase 3 trial which showed that fidaxomicin met its primary endpoint of non-inferiority of clinical cure compared to Vancocin®. In addition, patients treated with fidaxomicin in the first Phase 3 trial experienced a reduction in CDI recurrence compared to Vancocin (p=0.004) and had a higher global cure (cure with no recurrence within four weeks) compared to Vancocin (p=0.006). If the results of this second study are also positive, the Company expects to use these studies as a basis for a New Drug Application filing in 2010.

Fidaxomicin Clinical Study Design

The second Phase 3 trial is a multi-center, randomized, double-blind clinical trial comparing the safety and efficacy of fidaxomicin (200 mg q12h) to that of oral vancomycin (125 mg q6h) in subjects suffering from CDI. This study, which enrolled 536 adult subjects providing 90% power to assess the primary endpoint of clinical cure, was conducted in approximately 100 clinical sites throughout North America and Europe. The study is designed to evaluate safety and compare the response to treatment by subjects during and after a 10-day course of therapy for cure, which is the primary endpoint. If cured, subjects are followed for a subsequent four-week period to evaluate recurrence, which is a secondary endpoint. Global cure, defined as cure with no recurrence, is also a secondary endpoint.

About Clostridium Difficile Infection

CDI has become a significant problem in hospitals, long-term care facilities and in the community. It is a serious illness caused by 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. CDI typically develops from the use of broad-spectrum antibiotics that disrupt normal gastrointestinal (gut) flora, allowing C. difficile bacteria to flourish.

Current therapeutic options for CDI include the off-label use of metronidazole or oral vancomycin, the only FDA approved treatment for CDI. However, approximately 20% to 30% of CDI patients who initially respond to these treatments experience a clinical recurrence following cessation of antibiotic administration.

Primary risk factors for CDI include broad-spectrum antibiotic use, advanced age (over 65), emerging hyper-virulent strains (BI/NAP1/027, 078, 001) of C. difficile, and previous exposure to CDI that lead to recurrence. Higher incidence, increased treatment failures, and recurrence with standard therapies have resulted in greater awareness and concern of CDI among medical professionals and public health officials.

About Fidaxomicin

Fidaxomicin is the first in a new class of antibiotics called macrocyclics, which inhibit the bacterial enzyme RNA polymerase, resulting in the death of Clostridium difficile. The narrow spectrum profile of fidaxomicin may eradicate Clostridium difficile selectively with minimal disruption to the normal intestinal flora. This may facilitate the return of the normal physiological conditions in the colon and reduce the probability of CDI recurrence.

About Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc. is a biopharmaceutical company focused on discovering, developing and commercializing innovative anti-infective products to treat serious infections and address unmet medical needs. Optimer has two late-stage anti-infective product candidates under development. Fidaxomicin, formerly known as OPT-80, is the only antibiotic therapy currently in Phase 3 worldwide clinical development for Clostridium difficile infection. Pruvel(TM) (prulifloxacin) is an antibiotic which has completed two Phase 3 clinical trials for the treatment of infectious diarrhea in travelers. Additional information can be found at http://www.optimerpharma.com.

Forward-looking Statements

Statements included in this press release that are not a description of historical facts are forward-looking statements, including without limitation all statements related to the ability of fidaxomicin to treat CDI and address current treatment limitations, expected regulatory filings and announcements of clinical data. Words such as "believes," "anticipates," "plans," "expects," "intend," "will," "goal" and similar expressions are intended to identify forward-looking statements. The inclusion of forward-looking statements should not be regarded as a representation by Optimer that any of its plans will be achieved. Actual results may differ materially from those set forth in this release due to the risks and uncertainties inherent in Optimer's business including, without limitation, risks relating to: the timing, progress and likelihood of success of its product research and development programs and clinical trials, the timing and status of its preclinical and clinical development of potential drugs, the process of preparing and submitting regulatory filings with the FDA and other risks detailed in Optimer's filings with the Securities and Exchange Commission.