Halozyme blitzed as FDA rejects Baxter drug, halts combo trial

Fretting over a possible safety issue, the FDA has rejected an application for an immune deficiency treatment that includes a main ingredient from Halozyme and ordered a halt to a separate trial that involves the same product. The news torpedoed Halozyme's shares ($HALO), which swiftly plummeted 56% on the news.

Regulators are demanding that Baxter ($BAX) and Halozyme produce pre-clinical data on HyQ after raising concerns about the "non-neutralizing antibodies" triggered by the biotech's recombinant human hyaluronidase. The FDA wants to see if rHuPH20 has an impact on reproduction, development and fertility. And until they get the issue resolved, a combo study of ViroPharma's ($VPHM) approved angioedema drug Cinryze is also on hold.

"Elevated anti-rHuPH20 antibody titers were detected in the registration trial, but have not been associated with any adverse events," Halozyme noted in a release on the Baxter application.

"With receipt of the CRL, we can directly address the questions raised by CBER," said Halozyme CEO Gregory I. Frost. "We look forward to collaborating with the agency to address their concerns."

- read the press release on the CRL
- here's the release on the ViroPharma study
- get the Bloomberg report