ViroPharma stock plunges on bad news for Vancocin; Sanofi patents invalidated

ViroPharma I (Nasdaq: VPHM)  saw its shares plunge 19% to $23.25 yesterday after it announced that the US Food and Drug Administration had denied the citizen petition the company filed on March 17, 2006 related to the FDA's proposed in vitro method for determining bioequivalence of Abbreviated New Drug Applications referencing its antibiotic Vancocin (vancomycin hydrochloride, USP) Capsules.

In the FDA's response to the citizen petition, the agency denied ViroPharma's citizen petition and also informed the company that a final guidance for vancomycin bioequivalence consistent with the FDA's citizen petition response is forthcoming.

The FDA also informed ViroPharma in the same correspondence that the recent supplemental NDA for Vancocin approved December 14, 2011 would not qualify for three additional years of exclusivity based on the agency's assertion that in order for an sNDA for an old antibiotic such as Vancocin to be eligible for a grant of exclusivity, it must be a significant new use or indication. FDA also indicated that it is approving three ANDA's for generic vancomycin capsules.