ViroPharma Pursues Citizen Petition to Block FDA Approval of Generic Vancomycin

            by David Harper

The FDA recently posted ViroPharma, Inc.'s scientific supplement to its citizen petition asking FDA to stay approval of generic Vancocin (vancomycin hydrochloride).  Vancocin is ViroPharma's orally administered tricyclic glycopeptide antibiotic derived from Amycolatopsis orientalis that is approved for treatment of colitis caused by susceptible bacteria.  There are no unexpired patents or other exclusivities available for Vancocin.

ViroPharma filed its citizen petition March 17, 2006, asking FDA to stay approval of any ANDAs that reference Vancocin capsules based solely on in vitro bioequivalence testing.  This was in response to the FDA Office of Generic Drugs (OGD) announcement that in vivo clinical trials would not be required to establish bioequivalence of generic vancomycin hydrochloride capsules.

On May 31, 2006, ViroPharma submitted a first supplement to its petition, setting forth its legal arguments that OGD's new standard cannot be used in the review or approval of generic vancomycin.  These legal arguments included alleged OGD violations of the Freedom of Information Act, the Data Quality Act, and the Administrative Procedures Act with respect to implementation of its new in vitro test for Vancocin bioequivalence, as well as asserted legal problems with the test itself.

The recent scientific supplement to ViroPharma's petition sets forth scientific and clinical arguments regarding the asserted inadequacy of OGD's in vitro test.  Among its arguments, ViroPharma places special emphasis on the complexity of Vancocin and the life-threatening nature of the indications for which it is approved, and the need for comparative clinical trials to establish bioequivalence.