Dynavax tumbles as FDA asks for more Heplisav data

NEW YORK (AP) -- Shares of Dynavax Technologies Corp. fell by more than a third after the company said the Food and Drug Administration won't approve its hepatitis B vaccine Heplisav unless Dynavax provides more information showing the drug is safe.

Dynavax said the FDA is concerned about the possibility of "rare autoimmune events" in patients. The company has asked the FDA to approve Heplisav, its most advanced drug, in patients aged 18 to 70, but the FDA prefers a narrower marketing approval. The agency also wants more information about the manufacturing and quality of Heplisav.

The Berkley, Calif., company said it expects to meet with the FDA within six weeks. Dynavax said it does not know how long it will take to satisfy the agency's concerns, but said it would be willing to discuss a more limited approval for Heplisav.

Shares of Dynavax lost $1.07, or 36 percent, to $1.90 in morning trading. That was the lowest price for Dynavax shares since October 2011.

Heplisav is designed is given in two doses instead of three for traditional vaccines, and Dynavax says it provides protection faster than other drugs. Hepatitis B is a chronic liver infection that is spread through the blood or bodily fluids of infected people. It can cause liver inflammation and jaundice. A vaccine is available and treatment can manage the virus.

In November an FDA advisory panel questioned the safety of Heplisav and said there was no enough data to show the drug is safe. Shares of Dynavax had fallen 34.6 percent since then.

Dynavax is also studying treatments for autoimmune and inflammatory disease and respiratory illnesses. It does not have any products on the market.