Dynavax Technologies Corp (DVAX)

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The Food and Drug Administration put a "clinical hold" on testing of Dynavax Technologies Corp.'s Heplisav product, intended as a vaccine for hepatitis B.

Berkeley-based Dynavax (NASDAQ: DVAX) is testing the vaccine with partner Merck & Co. (NYSE: MRK), based in Whitehouse Station, N.J.

The FDA stopped the testing because of "a serious adverse event" in a person who received the vaccine outside of the United States. One patient developed Wegener's granulomatosis, a disease that inflames the blood vessels. The diagnosis is a preliminary one, the company said. Clinical trials cannot continue until the FDA gives its OK.

Heplisav is being tested outside the United States in a Phase III trial. All the patients in that test have already been injected with the drug and will be monitored. People in a Phase II trial of the vaccine in Canada won't get any more injections.

Over seven years of testing, about 2,500 people have been injected with Heplisav in 10 clinical trials. This is the first report of Wegener's granulomatosis in any test subject.