Nov. 16 (Bloomberg) -- Dynavax Technologies Corp. tumbled the most in four years after its hepatitis B vaccine Heplisav failed to win the backing of U.S. regulatory advisers as the drugmaker seeks to bring its first product to market.
Dynavax fell 50 percent to $2.33 at 9:34 a.m. New York time, after dropping as low as $2.26 for its biggest intraday decline since Oct. 22, 2008. While Heplisav works to treat the contagious liver disease, Dynavax didn’t provide adequate safety data to support approval, Food and Drug Administration advisers voted yesterday.
Dynavax, based in Berkeley, California, billed the drug as a way to protect healthy adults 18 to 70 years old. Panel members that called Heplisav promising cited the small number of patients Dynavax studied given the vaccine’s potential to cause rare autoimmune diseases.
“Since we have vaccines that maybe aren’t as optimal as we want but are effective, that is too flimsy,” Edgar Marcuse, a panel member and associate medical director at Seattle Children’s Hospital, said during the meeting in Silver Spring, Maryland.
Dynavax shares had risen 39 percent this year through Nov. 14. Regular trading was halted yesterday for the meeting. The FDA, set to make a decision on the vaccine by Feb. 24, isn’t required to follow the advisory panel’s guidance.
If approved, Heplisav is expected to generate $775 million in peak worldwide sales in 2020, Katherine Xu, an analyst with William Blair & Co. in New York, said in an e-mail. Dynavax reported $22 million in revenue in 2011.
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.
The Dynavax vaccine worked as well after two doses as three doses of GlaxoSmithKline Plc’s Engerix-B vaccine to protect patients against the virus, FDA staff said in a Nov. 13 report. The advisory panel yesterday voted 13-1 that Heplisav works and split 8-5 with one abstention that the safety data was inadequate.
Dynavax studied 2,400 patients and suggested a study once Heplisav is on the market would need to look at 30,000 people using the vaccine to detect whether it may be linked to rare illnesses. Two main trials on the vaccine weren’t set up to detect rare adverse events, according to the Nov. 13 report.
Agency staff recommended evaluation of Heplisav after the drug is on the market because some patients experienced autoimmune diseases.
One woman experienced Wegener’s granulomatosis, a rare disease in which blood vessels are inflamed and another woman developed Guillain-Barre syndrome, a disorder in which the body’s immune system attacks the nerves. The woman with Guillain-Barre syndrome also received an influenza vaccine that was thought to have caused the disorder rather than Heplisav.
The FDA put a hold on two clinical trials in March 2008 after a patient given the vaccine was diagnosed with Wegener’s granulomatosis. U.S. regulators allowed testing to resume in September 2009.
In a final-phase study of about 2,400 patients ages 18 to 55, 95 percent of those who took two doses of Heplisav were protected from hepatitis B, compared with 81 percent of those who took three doses of Glaxo’s Engerix-B, FDA staff said in the report.
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