Fidaxomicin, formerly known as OPT-80, PAR-101 or Difimicin, is a new class of antibiotics for the treatment of Clostridium difficile infection, or CDI, also known as Clostridium difficile-associated disease, or CDAD. We believe that Fidaxomicin offers advantages over current treatments due to its demonstrated activity against C. difficile, low rates of recurrence, evidence of low C. difficile resistance, minimal systemic exposure, limited disruption of normally occurring gastrointestinal bacteria and convenient dosing regimen. Our studies indicate that Fidaxomicin acts by inhibiting RNA polymerase, a bacterial enzyme, which results in the death of specific bacteria such as C. difficile.

Fidaxomicin has completed the first Phase 3 clinical trial in North America for the treatment of CDI. The Company reported top line data from this study in November 2008, showing that Fidaxomicin met both primary and secondary endpoints and that the drug had a higher global cure rate and lower recurrence rate than Vancocin® (oral vancomycin).  

The first Fidaxomicin Phase 3 clinical trial was a multi-center, randomized, double-blind clinical trial with 629 adult subjects enrolled. Subjects with confirmed CDI received either 200 mg Fidaxomicin dosed orally twice daily or 125 mg Vancocin, the only approved treatment for CDI in the US, 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) 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. 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, an exploratory endpoint, was defined as patients who were cured and did not have a recurrence.

A second Phase 3 clinical trial of the same design is currently ongoing in North America and Europe.  We anticipate reporting data in early 2010. If the second trial is as successful as the first trial, we intend to use these studies to support the filing of a new drug application, or NDA, for U.S. registration as soon as practical thereafter.

We are developing an oral suspension formulation which complements the existing tablet form of Fidaxomicin. This formulation is intended for use with intensive care unit and elderly patients. We plan to file an IND for potential label expansion.  We are also pursuing the development of Fidaxomicin for additional indications. We believe Fidaxomicin may be effective for the prevention of CDI.