Clinical hold on Heplisav by FDA

USA-based Dynavax Technologies and drug major Merck & Co say that the Food and Drug Administration has placed a clinical hold on the two Investigational New Drug applications for Heplisav, an investigational hepatitis B vaccine being jointly developed for use in adults by the firms.

The FDA took the action because of a serious adverse event that occurred in one subject who received Heplisav in a Phase III study being conducted outside the USA. The subject was preliminarily diagnosed as having Wegener's granulomatosis, an uncommon disease in which the blood vessels are inflamed. All subjects in this trial have received all doses per the study protocol and will continue to be monitored. Administration of vaccine has been suspended in the only study of the product in which injections were being administered actively, a fully-enrolled Phase II trial in end-stage renal disease subjects being conducted in Canada. A total of around 2,500 individuals have been vaccinated with more than 5,000 doses of Heolisav in 10 clinical trials spanning about seven years. There were no prior reports of Wegener's granulomatosis in these trials. No additional clinical trials with Heplisav will be initiated until the clinical hold has been resolved.

The news caused Dynavax' shares to plunge 43% in after-hours trading, though just 12.3% to $5.22 in regular trading on March 17.