New C. diff Drug OK'd by FDA Panel

April 5, 2011 – The FDA should approve Optimer's fidaxomicin for the treatment of the C. diff superbug, an expert advisory panel today unanimously agreed.

C. diff (Clostridium difficile) infects as many as 3 million Americans every year, making it the top bacterial cause of severe diarrhea in the nation. Only one other drug, vancomycin, is FDA approved for treating the difficult-to-eradicate bug.

Although metronidazole is often used as an "off-label" C. diff treatment, it often fails. "Off-label" refers to the practice of prescribing drugs for a purpose not specifically approved by the FDA. Fidaxomicin is designed to attack only C. diff, and may have less harmful effects on helpful gut bacteria.

While the panel voted 13-0 in favor of approving fidaxomicin, it split in a 6-6 vote, with one abstention, over whether the FDA should let Optimer claim that the drug prevents C. diff recurrence.

Recurrence is one of the worst things about C. diff. Even after successful treatment, up to 20% to 30% of patients see their C. diff infections come back. Many of these patients have recurrent attacks over the course of months or even years.

Recurrence usually happens within 60 days of the initial treatment. Optimer's clinical trials showed that fidaxomicin cut recurrences over 31 days.

The panel vote -- and the desperate need for new C. diff treatments -- makes rapid FDA approval appear likely. But the FDA and Optimer will have to wrangle about the exact claims that can be made about how well the drug prevents C. diff recurrence.