Halozyme Falls as ViroPharma Cancels Mid-Stage Drug Trial

Halozyme Therapeutics Inc., a developer of drug-delivery systems, fell the most in a year after its partner ViroPharma Inc. ended a mid-stage trial of a therapy for a genetic disease that causes severe swelling.

Halozyme dropped 14 percent to $7.32 at the close in New York, the biggest single-day decline since Aug. 2, 2012. ViroPharma lost 6.8 percent to $32, its greatest decline in three months. The trial’s cancellation was announced today by the companies in statements.

ViroPharma was running a clinical trial of a subcutaneous formulation of Cinryze, its drug to prevent the swelling attacks. Halozyme’s recombinant human hyaluronidase, or rHuPH20, was being combined with Cinryze for the subcutaneous treatment.

The treatment for hereditary angioedema was in the second of three phases of trials usually required before U.S. regulatory approval when some patients developed unexpected antibodies, Exton, Pennsylvania-based ViroPharma said. San Diego-based Halozyme said the companies hadn’t seen any adverse effects, and called the halt a precaution.

“We support ViroPharma’s business decision,” Halozyme Chief Executive Officer Gregory Frost said in a statement.

Frost said he was confident of the drug’s safety profile.

A trail of recombinant human hyaluronidase was halted a year ago, as well, before being restarted.