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Merck's hepatitis B vaccine trial on hold

Published on 28/03/08 at 11:41am

US regulators have placed a 'clinical hold' on one of the trials for Merck's hepatitis B vaccine Heplisav, raising questions about its commercial chances.

The FDA's decision came after one patient in a phase III study outside the US was diagnosed with Wegener's granulomatosis, a serious but unusual condition in which the blood vessels are inflamed.

A clinical hold is an order to delay a proposed clinical trial or suspend an ongoing one and has been slapped on the two investigational new drug applications for Heplisav.

Merck is developing the vaccine in collaboration with Dynavax Technologies, but their development schedule has now been thrown into question.

A spokeswoman for Dynavax told Pharmafocus: "We don't know what it means for the future of the vaccine. The clinical hold prevents us from moving forward into some US studies which are in the critical path."

The order appears to be more evidence of the regulator taking a harder line on drug safety and critics may see the FDA's move as an overreaction, given that it was one patient suffering from a rare, possible pre-existing, condition.

Around 2,500 individuals have been vaccinated with more than 5,000 doses of Heplisav in ten clinical trials over the past seven years, with no previous reports of Wegener's granulomatosis occurring.

The Dynavax spokeswoman declined to comment on the FDA's decision, but said all patients in the same study will continue to be monitored. "The phase 3 study was completely dosed and results are expected mid-year," she said.

The Canadian trial that has been placed on hold is a phase II study in end-stage renal disease subjects and the only one in which Heplisav injections were being administered actively.

Dynavax said data from this suspended trial is expected to be released, but the clinical hold means no additional clinical trials with Heplisav can be started until the issue has been resolved.

In a statement, Merck said the two companies, "along with additional collaborators, including clinical investigators and leading experts" are in the process of evaluating the medical history of the patient suffering from Wegener's granulomatosis "to understand better the timing and onset of the disease symptoms, including whether it was a pre-existing condition or was related to vaccine administration".

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