JERSEY CITY, N.J., Nov. 1, 2012 /PRNewswire/ -- Optimer Pharmaceuticals, Inc. (NASDAQ: OPTR) today announced that the first patient has been dosed in its DEFLECT-1, Phase 3b clinical trial of DIFICID® (fidaxomicin) tablets for the prevention of Clostridium difficile-associated diarrhea (CDAD) in patients undergoing hematopoietic stem cell transplant (HSCT), often referred to as bone marrow transplantation. CDAD can be a serious complication of HSCT. (Logo: http://photos.prnewswire.com/prnh/20090413/LA97352LOGO) Patients undergoing HSCT present with multiple risk factors including immune suppression and the use of prophylactic antibiotics which make them susceptible to CDAD; it is estimated that up to 30% of patients undergoing the procedure will develop CDAD. HSCT patients with CDAD generally have longer hospital stays, increased average costs and are at increased risk of death. "By nature of the procedure, patients undergoing HSCT have weakened immune systems and are often receiving antibiotics, both of which are significant risk factors for the development of CDAD," said Sherwood L. Gorbach M.D., Optimer's Chief Scientific Officer and Senior Vice President of R&D. "Consequently, the prevalence of CDAD in these patients is high and we believe that DIFICID has potential to prevent CDAD in this high-risk population. We hope that this trial will provide us data supporting this hypothesis." This multi-center study will utilize a randomized, double-blind design to evaluate the safety and efficacy of DIFICID as prophylaxis in individuals undergoing HSCT. It will enroll an estimated 340 patients into two arms, one of which will receive 200 milligrams of DIFICID daily for thirty days and the other of which will receive a placebo, since the efficacy of CDAD prophylaxis has not been previously determined. By using an innovative "adaptive design," a blinded interim analysis will be conducted after 170 evaluable subjects have completed treatment and the 30 day post-treatment follow up to re-estimate the sample size based on accumulated data. The primary endpoint is the incidence of CDAD from the first dose of study drug through the 30-day follow-up period after the last day of drug. The objective is to achieve a 60% improvement in the CDAD incidence rate in the DIFICID group over the placebo group. Initial data from the trial is expected in the first half of 2014.