The FDA has approved bepirovirsen (Hibsago) as a potential functional cure for adults with chronic hepatitis B who have no cirrhosis and are already taking antiviral therapy. The drug, an antisense oligonucleotide, is given as a 6-month course that can be self-administered after the first dose, alongside nucleos(t)ide analog therapy. Approval was based on the phase III B-Well 1 and B-Well 2 trials, which showed that nearly one in five patients achieved a functional cure—defined as sustained loss of hepatitis B surface antigen—compared with none in the placebo group.
Efficacy was higher in patients with lower baseline antigen levels. Among those with HBsAg of 1,000 IU/mL or less, a group that accounts for roughly 45% of diagnosed cases worldwide, the functional cure rate reached 26%. Investigator Norah Terrault of the Keck School of Medicine called the approval "the start of a new era," while FDA's Wendy Carter noted that the drug offers some patients the possibility of maintaining control of the virus after all chronic HBV treatment has ended.
The most common side effects include injection site reactions, fatigue, fever, and headache. The prescribing information carries a boxed warning about serious hepatic flares and low platelet counts, which can lead to life-threatening thrombocytopenia. Other warnings cover worsening kidney function, serious inflammatory reactions such as vasculitis, and risks from improper injection. Because of these risks, patients need regular blood tests, and the drug is not recommended for those with hepatitis D virus coinfection.