SAN DIEGO (AP) -- Shares of Halozyme Therapeutics Inc. plunged Wednesday after the Food and Drug Administration raised questions about the safety of its drug ingredient that is being studied to help inject several medicines.
The company said its partner Baxter received a response letter from the FDA about their collaborative drug HyQ, which combines Baxter's immune globulin with Halozyme's recombinant human hyaluronidase, which helps with drug absorption. The FDA has safety concerns about possible long-term impact on patients' reproduction, development and fertility, according to Halozyme.
Halozyme shares plunged $4.72, or 55 percent, to $3.84 in after-hours trading.
In a similar announcement, ViroPharma International said the FDA halted testing of its experimental drug Cinryze for patients with a rare genetic disease that causes swelling. ViroPharma was testing a formulation of the drug in combination with Halozyme's hyaluronidase.
ViroPharma said it would move ahead with studies of its drug that do not include Halozyme's product.
"FDA stated that the issues are not specific to Cinryze and that ViroPharma could continue to evaluate subcutaneous administration of Cinryze," as a stand-alone therapy, the company said in a statement.
ViroPharma Inc. shares fell 67 cents, or 3 percent, to close at $21.04.
