ViroPharma Inc. (VPHM) recently announced the initiation of a mid-stage trial of VP 20621. The company is evaluating the candidate for the prevention of recurrence of clostridium difficile infection (CDI) in adults previously treated for the condition.
The phase II dose-ranging study is being conducted to evaluate the safety and tolerability of VP 20621 dosed orally for up to 14 days in adults previously treated for CDI; characterize the frequency and duration of stool colonization with VP 20621 strain of C. difficile; evaluate the efficacy of the candidate for prevention of recurrence of CDI; and select a dose regimen of VP 20621 to be used in future studies.
The study will enroll 240 CDI patients who have been previously treated with metronidazole or oral Vancocin (vancomycin). The patients will be randomized into four treatment groups with VP 20621 administered once daily for 14 days after completion of CDI antibiotic treatment. The study will be conducted over six months.
Vancocin, ViroPharma’s another drug for the treatment of antibiotic-associated pseudomembranous colitis, caused by clostridium difficile, is also marketed for the treatment of enterocolitis caused by staphylococcus aureus (including methicillin-resistant strains).
Vancocin, which is one of the primary revenue contributors at ViroPharma, is not protected by any patent. Vancocin generics are yet to hit the market with the FDA requiring generic companies to conduct a bioequivalence study to gain approval for their versions. We note that a proposed bioequivalence method for Vancocin is filed for approval with the FDA. If the method gets the regulatory body’s approval, the time required for a generic manufacturer to get a copycat version of Vancocin approved will be reduced and multiple generics may enter the market, thereby leading to significant sales erosion of the drug.
Moreover, Vancocin could face competition from Optimer Pharmaceuticals Inc.’s (OPTR) Dificid (fidaxomicin), which is currently under regulatory review in the US, with a decision expected by May 30, 2011.
We currently have a Neutral recommendation on ViroPharma, which is supported by a Zacks #3 Rank (short-term Hold rating).
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