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Orphan Drug Status for ViroPharma's Maribavir

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ViroPharma Inc. (VPHM) recently received ‘orphan drug designation’ in the EU for its pipeline candidate, maribavir, for the treatment of cytomegaloviral (:CMV) in patients suffering from impaired cell mediated immunity.

We note that maribavir was granted the same designation in the US in May 2011 for the treatment of clinically significant CMV and disease in at-risk patients.

We remind investors that ViroPharma was previously developing maribavir as an anti-CMV agent to prevent CMV disease in transplant patients. However, results from phase III studies showed that maribavir failed to meet its efficacy endpoints at a lower dose.

Nevertheless, studies are ongoing as ViroPharma expects that higher doses might provide clinical activity based on overall safety profile of maribavir and limited data from cases in which open-label maribavir was used as CMV treatment.

The company also discontinued a study evaluating maribavir in liver transplant patients.

ViroPharma initiated two phase II studies in 2012 to evaluate maribavir at different doses for the treatment of CMV infections in transplant recipients. The studies are being conducted in Europe and the US.

The study conducted in Europe focuses on hematopoietic stem cell or solid organ transplant recipients who carry CMV viremia but do not have CMV organ disease, whereas the study in the US focuses on patients who have resistant or refractory CMV viremia with or without CMV organ disease.

We note that ViroPharma acquired global rights to maribavir (excluding Japan) in 2003 from GlaxoSmithKline (GSK).

We note that Roche’s (RHHBY) Valcyte is approved for the prevention of CMV disease in patients who have undergone a heart, kidney, or kidney-pancreas transplant.

ViroPharma currently carries a Zacks Rank #3 (Hold). Right now, Salix Pharmaceuticals (SLXP) looks attractive with a Zacks Rank #1 (Strong Buy).

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