FDA Calls For Tough Warning on Genentech's Xolair Asthma Drug

Genentech's asthma drug Xolair should carry the strongest warning possible about the drug's risk of a serious reaction known as anaphylaxis, U.S. health regulators said Wednesday.

The Food and Drug Administration said anaphylaxis -- a severe allergic reaction -- could occur as late as 24 hours after patients take any amount of the drug, also known as omalizumab. The agency added that doctors and patients should be prepared to treat the reaction, which can cause breathing problems, fainting and hives.

In a statement, the South San Francisco-based biotech said it was still discussing the request for a so-called black box warning with the FDA. "The updated wording and its placement in the label is not yet final," the company said.

Genentech is majority-owned by Swiss drugmaker Roche Holding.

Reports of the reaction to Xolair were seen in clinical trials before the drug was approved in 2003 to treat patients with allergy-related asthma, the FDA said. About one in a thousand patients experienced it.

Continued reports of the problem after that prompted the agency's call for the tough warning given "their life-threatening potential, frequency, and the possibility for the delayed onset of anaphylaxis," the agency added.