Halozyme takes a second hit after safety fears scuttle PhII combo study

A year to the day after the FDA slapped a clinical hold on a mid-stage trial of an immune deficiency drug made up of ViroPharma's approved angioedema drug Cinryze and a product from Halozyme, investigators have decided to stop work on the program. And once again, San Diego-based Halozyme shares were hammered in the aftermath.

Back in the summer of 2012, Halozyme announced that the FDA had rejected Baxter's ($BAX) application for HyQ, a subcutaneous combination of Immune Globulin 10% and Halozyme's ($HALO) recombinant human hyaluronidase, rHuPH20, for patients with primary immunodeficiency disease. Regulators were concerned about evidence of non-neutralizing antibodies generated against recombinant human hyaluronidase and "the possible effects of these antibodies on reproduction, development and fertility." The FDA's CBER told investigators to stop dosing patients with rHuPH20 in the Baxter and ViroPharma ($VPHM) clinical studies.

Halozyme also cautioned that no adverse events had been detected. But that didn't save the program. Halozyme's shares were routed on the news today, plunging 18%.

Baxter and Viropharma were relying on Halozyme's rHuPH20 to improve delivery of their therapy. Halozyme often relies on other companies to in-license the product to improve the performance of protein therapies. Even after the trouble erupted in 2012, though, Pfizer ($PFE) came through with a similar pact at the end of the year, helping to reassure investors that the industry hadn't lost faith in Halozyme's product.  

"Given the profile of this clinical formulation and the time required to enable ViroPharma to move forward with this formulation, we support ViroPharma's business decision," said Halozyme CEO Gregory I. Frost. "We have accumulated a robust data set regarding the clinical use of rHuPH20 across many different programs and indications, and feel confident about the safety profile of the rHuPH20 platform that has emerged from this clinical use and its continued application in our other products and programs around the world."

- here's the press release