Dynavax stock rocketed up more than 70 percent in midday trading Monday after an FDA panel voted in favor of the company's primary drug under development.
The majority of an FDA advisory committee voted "yes" when asked whether data support the safety of Dynavax's Heplisav.
"[The] panel vote is a major win for Dynavax," J.P. Morgan analyst Anupam Rama wrote in a note. "We now believe that Heplisav has a high probability of approval by the August 10th [FDA review deadline]."
The immunotherapy company is developing Heplisav as a hepatitis B vaccine treatment for adults. Heplisav could become the standard treatment for the viral liver infection, Rama said, because Dynavax's drug has an easier dosing schedule than competitor GlaxoSmithKline's Engerix-B.
The shares rose as high as $17.20 at one point Monday, an 86 percent pop, and were last up 74 percent to $16.15.
Two previous FDA reviews of Heplisav rejected the vaccine, citing unresolved safety concerns.
Heplisav aims to boost patients' immune systems in response to hepatitis B, an incurable disease which can lead to liver cancer and death.
While the FDA committee's review said Heplisav's treatments were effective, the FDA does not need to follow the advice of its committees. Dynavax's outlook remains positive, in Rama's view, and the FDA often goes along with its committees' recommendations.