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June 10 (Bloomberg) -- Dynavax Technologies Corp., a drugmaker seeking to bring its first product to market, tumbled 43 percent after U.S. regulators asked for a wider study to assess the safety of the company’s hepatitis B vaccine.

Dynavax closed at $1.40 in New York trading, its lowest price since April 2010. The Berkeley, California-based company has now lost 64 percent of market value in the past 12 months.

The Food and Drug Administration had rejected the vaccine, Heplisav, in February after determining Dynavax’s safety data was lacking. The agency now wants to see a study that goes beyond the 3,500 people Dynavax examined for adverse events in clinical trials, a process that may take months or even years.

“The silver lining here is instead of having restricted approval, when we get the safety database and if it all works out, we will have the full label,” Michael Ostrach, Dynavax’s chief business officer, said today in an interview.

The company is talking with the FDA and should be able to provide an update in “months to weeks” on the design of a trial to capture more safety data, he said.

Advisers to the FDA suggested at a November meeting that Dynavax should study 8,000 to 10,000 patients using the vaccine.

Targeting Patients

Dynavax planned to focus on smaller groups in need of new vaccine options because they don’t respond well to current vaccines, including those older than 40 and patients with chronic kidney disease, Ostrach said. The additional safety data will help make Heplisav available for a wider population of people 18 to 70 years old, the company said in a statement.

FDA staff determined in November, and an advisory panel agreed, that the vaccine worked as well in fewer doses as GlaxoSmithKline Plc’s Engerix-B. A panel of agency advisers later raised concerns that the product may have the potential to cause rare autoimmune diseases.

Hepatitis B, like HIV, is transmitted through the exchange of body fluids such as blood, saliva or semen, according to the Centers for Disease Control and Prevention. It attacks the liver, which removes toxins from the body, and can lead to scarring, cancer or organ failure.

To contact the reporter on this story: Anna Edney in Washington at

To contact the editor responsible for this story: Reg Gale at

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