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ViroPharma Incorporated recently announced that the US Food and Drug Administration (FDA) has advised the company and its partner, Halozyme Therapeutics (HALO - Snapshot Report), to put the phase II study evaluating the combination subcutaneous Cinryze (C1 esterase inhibitor [human]) and recombinant human hyaluronidase enzyme (rHuPH20) on temporary clinical hold.

The Center for Biologics Evaluation and Research (CBER) division of the FDA informed the companies that the US regulatory body is assessing the potential risk of the long-term effect of anti-rHuPH20 non-neutralizing antibodies associated with the use of Halozyme's rHuPH20. The FDA detected some risks pertaining to rHuPH20 in a separate study without Cinryze.

Halozyme informed ViroPharma that it must first provide results from additional pre-clinical studies to the CBER before they can resume the on-hold combination study. The US regulatory body also mentioned that the problem does not specify Cinryze and ViroPharma can continue evaluating subcutaneous administration of Cinryze without rHuPH20.

ViroPharma has decided to inform the European regulatory authorities of the FDA’s action. The company has also decided to postpone its enrollment process in Europe for the phase II combination study of Cinryze and rHuPH20, until the FDA confirms the safety of the latter.

Following the FDA’s decision, ViroPharma is set to commence a phase II study, evaluating the safety and efficacy of two different doses of the subcutaneous administration of Cinryze as a stand-alone therapy. The US regulatory body cleared ViroPharma’s Investigational New Drug (IND) application for the stand-alone therapy of Cinryze in 2011.

ViroPharma recently announced positive results from an open label prophylaxis study of Cinryze in patients suffering from hereditary angioedema (HAE).

We note that Cinryze is approved both in the US and Europe. In the US the drug is approved as intravenous (IV) administration for routine prophylaxis against angioedema attacks in adolescent and adult patients with HAE. In Europe it is approved for routine prevention, pre-procedure prevention and acute treatment of angioedema attacks in adolescent and adult patients with HAE.

Our Take

We currently have a Neutral recommendation on ViroPharma. The stock carries a Zacks #3 Rank (Hold rating) in the short run.

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