The approval follows two phase 3 clinical trials, published in the New England Journal of Medicine. The results showed that a six-month course of bepirovirsen achieved a functional cure response in 233 of 1,220 participants (19 percent), compared to none of the 614 participants on a placebo. In those patients, the virus stayed undetectable for at least 24 weeks after all treatment had stopped, 72 weeks into the trial.
Chronic hepatitis B is a liver infection that can lead to cancer, scarring, or organ failure, and is responsible for over a million deaths worldwide each year. Current treatment can mean taking antiviral medication for years to keep the virus suppressed.
Bepirovirsen is administered via weekly injections alongside existing pill treatments. For patients who respond, the virus is suppressed to undetectable levels, and control can be maintained even after bepirovirsen treatment ends. Lower levels of a key CHB protein at the start of treatment indicated a higher chance of success, and could be tested for before bepirovirsen is prescribed.
"Bepirovirsen offers patients the potential to achieve functional cure after a short period of treatment, a long-standing goal for patients and physicians alike," said Norah Terrault, a gastroenterologist from the Keck Medical Center at the University of Southern California. Tony Wood, Chief Scientific Officer at GSK, said US patients now have the potential to achieve functional cure after a six-month treatment course, with the added convenience of the option of self-administration after the first dose.
The approval comes with caveats. Some patients experienced serious side effects including liver inflammation, which the FDA says should be monitored via regular blood tests. Wendy Carter, the Acting Director at the FDA's Office of Infectious Diseases, said the approval represents an important advance for people living with the disease, providing a new treatment approach that gives some patients the possibility of maintaining control of the virus after all chronic HBV treatment has ended.
Traces of the virus remain in the body, and it is not yet proven whether the cure holds for years after treatment ends. Chari Cohen, President of the Hepatitis B Foundation, said the decision marks significant progress towards transforming how chronic hepatitis B is managed, pointing to the disease’s role in approximately 56 percent of global liver cancer cases. GSK says it wants to make the drug available to more patients worldwide.