Optimer Pharmaceuticals, Inc announced positive top-line results from the second of two pivotal phase-3 trials evaluating the safety and efficacy of fidaxomicin (OPT-80) in patients with Clostridium difficile Infection (CDI). This study was conducted in approximately 100 clinical sites throughout North America and Europe. The company plans to use data from this study to support submission of a New Drug Application (NDA) to the US Food and Drug Administration (FDA) in the second half of 2010.

The trial met the primary endpoint of non-inferiority with 91.7 per cent of patients treated with fidaxomicin (per protocol population) achieving clinical cure vs. 90.6 per cent for Vancocin, the only US FDA-approved therapy for CDI. Importantly, fidaxomicin also had significantly lower recurrence rates and higher global cure rates (defined as cure with no recurrence within four weeks of completing therapy) compared to Vancocin. Only 12.8 per cent of patients treated with fidaxomicin experienced a recurrence vs. 25.3 per cent of patients treated with Vancocin (p = 0.002). Additionally, 79.6 per cent of patients treated with fidaxomicin achieved a global cure versus 65.5 per cent of patients treated with Vancocin (p < 0.001). As in the first phase-3 trial, fidaxomicin was well-tolerated in the study.

"The robust results from our second phase-3 trial of fidaxomicin confirm the results of our first phase-3 trial showing that fidaxomicin has the potential to be a first-in-class drug for the treatment of Clostridium difficile infection. There are currently limited treatment options for this disease and we believe there is a need for innovative alternatives," said Michael N Chang, Optimer's chief executive officer. "A higher global cure demonstrates the potential for fidaxomicin to improve patient outcomes, reduce repeat visits to the hospital and reduce person-to-person transmission, which may result in a lower cost burden to the healthcare system."

"The growing incidence of CDI in hospitals, long-term care facilities, and in the community, which we believe is caused in part by the use of broad-spectrum antibiotics and an aging population, create a need for new CDI therapies," said Sherwood L Gorbach, Optimer's chief medical officer. "These results show that a single, effective antibiotic can provide a high cure rate and simultaneously, a low recurrence rate. We believe fidaxomicin demonstrates a clinically significant difference and offers substantial benefits to CDI patients and the medical community."

The Per Protocol (Microbiologically Evaluable) Population is the patient group with CDI confirmed by diarrhea with a positive toxin assay, that met all inclusion/exclusion criteria, and that received at least three days of therapy if deemed a failure or at least 8 days of therapy if deemed a cure. The Modified Intent-to-Treat Population is the patient group with CDI confirmed by diarrhea with a positive toxin assay and received at least one dose of study medication.

The second fidaxomicin phase-3 trial (Protocol 101.1.C.004) and the first fidaxomicin phase-3 trial (Protocol 101.1.C.003) are the two largest comparative studies ever conducted against Vancocin in CDI. Additional data from this study will be presented at medical conferences in the near future.

In November 2008, the company 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 also experienced a reduction in CDI recurrence compared to Vancocin (p=0.004) and had a higher global cure compared to Vancocin (p=0.006). The first phase-3 study was conducted at sites throughout North America.

Fidaxomicin is the first in a new class of antibiotics called macrocycles, which inhibit the bacterial enzyme RNA polymerase, resulting in the death of C. difficile.

Optimer Pharmaceuticals is a biopharmaceutical company focused on discovering, developing and commercializing innovative anti-infective products to treat serious infections and address unmet medical needs.