Additional Data from Fidaxomicins Phase 3 Study for Clostridium difficile infection (CDI) Presented at IDSA Annual Meeting


Data Shows Faster Resolution of Diarrhea and Improved Outcome in Patients Requiring Concomitant Antibiotics

SAN DIEGO- October 31, 2009 – Optimer Pharmaceuticals, Inc. (NASDAQ: OPTR) today announced the presentation of new data from fidaxomicin’s North American phase 3 study at the 47th Annual Meeting of the Infectious Diseases Society of America (IDSA) in Philadelphia, PA.

Mark A. Miller, M.D., head of the Division of Infectious Diseases, Chair of the Infection Prevention and Control Unit at the Jewish General Hospital in Montreal, Quebec, Canada, presented results showing that fidaxomicin is associated with faster resolution of diarrhea. In patients with more pronounced diarrhea (ie. not resolving in the first 24 hours of therapy), fidaxomicin was associated with a faster time to resolution of diarrhea than vancomycin (79 hours vs. 105 hours, p=0.056). It is possible that decreasing the duration of diarrhea may have a direct impact on reducing the spread of CDI in healthcare facilities and lowering overall environmental spore contamination, thereby decreasing CDI rates and leading to earlier discharge of CDI patients from the hospital.

In another presentation, Kathleen M. Mullane, D.O., an investigator from the University of Chicago, Department of Medicine, Section of Infectious Diseases, in Illinois, presented data that indicated fidaxomicin may be a more effective therapy for CDI in patients requiring concomitant antibiotics. Treatment of CDI is often complicated by systemic infections requiring concomitant antibiotics. The analysis indicated that in patients receiving concomitant antibiotics, those treated with fidaxomicin versus vancomycin, had a significantly improved global cure rate (72% vs. 50%, p=0.022), lower CDI recurrence rate (40% vs. 23%, p=0.061), and higher clinical cure rate (87% vs. 77%, p=0.171).

“The faster time to resolution of diarrhea and improved outcomes for patients requiring concomitant antibiotics are important factors for physicians to consider when selecting a treatment for CDI,” said Michael N. Chang, Ph.D., President and CEO of Optimer Pharmaceuticals. “These additional factors along with the significantly lower recurrence rate and higher global cure rate suggest that fidaxomicin has the potential to be a best in class therapy for CDI.”
For a complete list of posters, please visit the Resources webpage on our web site at www.optimerpharma.com.

Fidaxomicin Clinical Study Design

629 adult subjects were enrolled in this multi-center, randomized, double-blind phase 3 clinical trial, which was the largest such trial for the treatment of CDI. Subjects with confirmed CDI received either 200 mg fidaxomicin dosed orally twice daily or 125 mg Vancocin dosed orally four times daily. This study was conducted in more than 100 clinical sites throughout North America. The objective of the study was to show that a 10-day course of fidaxomicin was at least as efficacious (non-inferior) and safe as a 10-day course of Vancocin (vancomycin hydrochloride capsules, USP) for the treatment of CDI.

The primary endpoint of the study was clinical cure defined as patients requiring no further CDI therapy two days after completion of study medication, as determined by the investigator. The secondary endpoint evaluated CDI recurrence up to four weeks post therapy with recurrence defined as the return of diarrhea associated with CDI confirmed by a positive toxin test. Global cure was defined as patients who were cured and did not have a recurrence.