Dynavax shares fall after issuing FDA response

Shares of Dynavax Technologies Corp. fell Thursday as the biotechnology company responded to a Food and Drug Administration request for more information on a halted study of the developing hepatitis B vaccine Heplisav.

The stock lost 2 cents, or 1.7 percent, to $1.13. Shares have traded between 98 cents and $6.55 over the last 52 weeks.

The FDA placed a hold on clinical trials for the drug in March because of safety concerns after a patient taking Heplisav was diagnosed with a rare disease that causes blood vessels to inflame. In its response to the agency, Berkeley, Calif.-based Dynavax confirmed the incident, but also said the condition had been found in one of the patients taking U.K.-based GlaxoSmithKline's Engerix-B.

The study is comparing the drugs. Whitehouse Station, N.J.-based Merck & Co. is Dynavax's partner on Heplisav. Its stock fell 1 cent to $31.12 in afternoon trading.

"The response submitted to the FDA contained a thorough review of both clinical and preclinical safety data for Heplisav," Dynavax said, in a filing with the Securities and Exchange Commission on Thursday. "

Still, safety results show that the profiles for Heplisav and the already-approved Engerix-B are similar, Dynavax said. The incidence of adverse events was 81.9 percent for Heplisav patients, compared with 81.4 percent for Engerix-B patients.

The FDA will now evaluate the company's response and make a decision on whether to allow the study to continue.