FDA rejects Dynavax's hepatitis B vaccine Heplisav-B; shares plummet

Shares in Dynavax Technologies fell as much as 71 percent Monday after the FDA issued a complete response letter regarding the company's filing for the hepatitis B vaccine Heplisav-B. Dynavax said the agency is seeking clarification regarding specific adverse events of special interest, a numerical imbalance in a small number of cardiac events in a single study of Heplisav-B, new analyses of the integrated safety database across different time periods and post-marketing commitments. 

Dynavax noted that the FDA indicated that it has not yet completed its review of responses received from the drugmaker early last month, including those related to specific adverse events of special interest, as well as the numerical imbalance in cardiac events. The drugmaker added that the agency did not request additional clinical studies or identify concerns regarding rare serious autoimmune events. 

CEO Eddie Gray remarked "the [complete response letter] is consistent with our opinion that Heplisav-B is approvable and we are seeking to meet with the FDA as soon as possible." However, the executive added that "the time and resources that will be required to gain approval leads us to consider that we may not be able to advance this programme on our own and we are moving swiftly to identify a potential pharmaceutical or financial partner." 

The FDA previously rejected Heplisav-B over safety issues in 2013 and later affirmed a need for additional safety data in the intended population. The agency accepted the drugmaker's resubmission seeking approval of Heplisav-B in March after the company completed a late-stage study assessing the safety of the vaccine in comparison to GlaxoSmithKline's Engerix-B. 

The FDA later cancelled an advisory panel meeting to consider Heplisav-B to permit it time to "review and resolve several outstanding issues." A report issued by TheStreet subsequently suggested that cancellation of the advisory panel meeting portended a high probably of rejection of the drug by the FDA. 

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