Two DIFICID Phase 3 trial data in C. difficile presented at DDW conference

Optimer Pharmaceuticals, Inc. (NASDAQ: OPTR) today announced the presentation of two abstracts at the 2011 Digestive Disease Week (DDW) conference highlighting additional analyses of data from Phase 3 trials of DIFICID™ (fidaxomicin), an investigational product for the treatment of Clostridium difficile infection (CDI).

The first analysis aimed to identify risk factors associated with early recurrence (a relapse within the first two weeks after end of therapy) compared to late recurrence (a relapse during the third and fourth weeks after end of therapy). Data presented by Kathleen Mullane, PharmD, D.O., Associate Professor of Medicine at The University of Chicago Department of Medicine, demonstrated that the majority of recurrences occurred within two weeks of completing initial therapy (129/190, 67.9%). Treatment with DIFICID was associated with a 66% reduction of early recurrence compared with vancomycin (7.4% vs 19.3%, p<0.001), and late recurrence was the same in both treatment arms. In addition, elevated white blood cell counts and low albumin levels at the end of treatment and exposure to concomitant antibiotics during the follow-up period were associated with a higher risk of late recurrence.  The study titled "Risk of Recurrence and Time to Recurrence Following Treatment of Clostridium difficile Infection: Patient Characteristics and the Differential Effect of Fidaxomicin vs. Vancomycin," was presented on May 7.

"As many as 30 percent of patients initially treated for CDI will experience recurrent disease, or the persistence of CDI symptoms following initial treatment. This can cause significant loss of work productivity, keep people from their daily lives and, in some cases, cause repeated hospitalizations," said Dr. Mullane. "The data from this study demonstrate that patients treated with fidaxomicin were significantly less likely to suffer a relapse of the initial infection within the first two weeks after completing therapy. The data also suggest that late recurrence is likely due to a reinfection from the environment, particularly in patients with risk factors such as elevated white blood cells and low albumin levels at the end of therapy and exposure to concomitant antibiotics."

The second poster presented today demonstrates that DIFICID is minimally absorbed with plasma levels in the low ng/mL range while maintaining high fecal concentration that are well in excess of the MIC90 versus C. difficile. The analysis measured the concentration of DIFICID and its metabolite, OP-1118, in the plasma and feces of patients treated with the drug in the Phase 3 clinical studies. Plasma concentrations were in the low nanogram per milliliter (ng/mL) range for both DIFICID and its metabolite at day 1 and at End-of-Therapy.  By contrast with the plasma concentrations, fecal concentrations were more than 10,000 times higher as fecal levels exceeded 1,000 micrograms/gram (ug/g) for DIFICID and 800 ug/g for its metabolite.  The DIFICID fecal levels were more than 1,000 times the minimum inhibitory concentration for C. difficile of 0.25 ug/mL and consistent with a high level of activity toward the target organism at the intended site of action in the colon.  The poster presentation is titled "High Fecal and Low Plasma Levels of Fidaxomicin and Metabolite OP-1118 in Patients with C. difficile infection:  Combined Results of Two Phase 3 Trials."

"Following oral administration, DIFICID has minimal systemic exposure, even in patients with CDI," said Pam Sears, Ph.D., Executive Director of Biology and Pre-Clinical Science at Optimer.  "These data show that DIFICID tends to stay in the site of infection for this disease."