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FDA rejects ViroPharma's citizen petition for Vancocin, approves generic versions

Tuesday, April 10 2012 | Comments
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The Food and Drug Administration denied the citizen petition filed by ViroPharma Inc. in connection with the FDA's proposed in vitro method for determining bioequivalence of Abbreviated New Drug Applications (ANDAs) referencing Vancocin (vancomycin hydrochloride) capsules.

News of the FDA's decision pushed shares of ViroPharma down 21.6 percent.

Vancocin is indicated for the treatment of Clostridium difficile-associated diarrhea (CDAD) and for the treatment of enterocolitis caused by Staphylococcus aureus, including methicillin-resistant strains.

ViroPharma filed a petition in 2006 to protest the FDA's method for determining bioequivalence of the antibiotic. The company insists that the agency "is incorrect in interpreting its bioequivalence regulations in a manner that provides it with broad discretion to permit in vitro bioequivalence testing in the absence of a waiver of in vivo testing."

In addition, the FDA informed ViroPharma that the firm's recent supplemental New Drug Application (sNDA) for Vancocin, which was approved in December, would not qualify for three additional years of exclusivity. With the sNDA approval, Vancocin's label was updated to include clinical efficacy and safety findings related to the treatment of currently circulating strains of C. difficile, including the more lethal, epidemic BI/NAP1 strain. The updated label also contains an instruction to monitor renal function in all patients who are treated with the drug, an instruction not to prematurely discontinue treatment in elderly patients or switch them prematurely to other therapies and a specific dosing regimen for CDAD.

ViroPharma believed the new labeling for Vancocin would preclude the approval of generic versions of the antibiotic for three years.

Under FDA regulations, labeling changes based on new clinical investigations that are essential to the approval of an sNDA and to which the applicant has exclusive rights may be entitled to three years of exclusivity, and generic drug labeling cannot include information protected by such three-year exclusivity, ViroPharma explained. A company can seek approval of a generic product by omitting labeling protected by three-year exclusivity, but if such omissions render the generic drug less effective or less safe, the drug cannot be approved until the three-year exclusivity expires.

The FDA's decision not to grant additional exclusivity was based on its assertion that in order for an sNDA for an older antibiotic, such as Vancocin, to be eligible for a grant of exclusivity, it must represent a significant new use or indication.

As a result, the FDA approved three ANDAs for generic vancomycin capsules filed by Watson Laboratories Inc., Akorn Inc. and Strides Arcolab Ltd. Alvogen Inc. will market the Strides Arcolab product.

ViroPharma said it believes that the three-year exclusivity provisions for old antibiotics "were intended to incent 'clinically relevant new safety and efficacy information' concerning the appropriate use of old antibiotics, particularly where the label for such a product contained no such information, because new prescribing instructions for physicians based on data in modern microbial strains will result in better care for patients."

The firm plans to file a complaint in the U.S. District Court for the District of Columbia seeking an injunction to set aside the FDA's approval of ANDAs for generic versions of Vancocin.

Shares of ViroPharma closed at $22.44, down $6.17, in heavy trading on the Nasdaq.

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