The U.S. Food and Drug Administration approved GSK plc's Hibsago (bepirovirsen) on Oct. 20 for certain adults with chronic hepatitis B, giving some patients a chance to discontinue antiviral medicine.
Across two trials, 24% of patients given Hibsago met the criteria to stop their existing antiviral, while no placebo recipients did. At 24 weeks after all treatment ended, 19% of Hibsago recipients still had the virus under control and no detectable hepatitis B surface antigen, a marker of infection.
The approval applies to adults without cirrhosis who have taken hepatitis B antivirals for at least six months. Their blood virus levels must already be suppressed, and an FDA-authorized test must show hepatitis B surface antigen at 3,000 IU/mL or less.
Hibsago is added to ongoing treatment. Patients receive injections for up to 24 weeks and remain on their existing antiviral during that course and for at least 24 weeks after the last injection. Clinical and laboratory results determine whether they can then stop the antiviral.
The agency authorized the Elecsys HBsAg II quant II RxDx assay from Roche to help select patients and monitor treatment. Hibsago is the first antisense oligonucleotide the agency has approved for chronic hepatitis B. It interferes with genetic instructions the virus uses to replicate and produce proteins.
Chronic hepatitis B can lead to cirrhosis and increase the risk of liver cancer. Keeping the virus suppressed can require years of antiviral medicine, the FDA said. Fever, fatigue, headaches and reactions around the injection site were among the most common side effects apart from abnormal laboratory results.
Hibsago carries a boxed warning for serious liver reactions and low platelet counts, which can cause dangerous bleeding. The FDA also warned of worsening kidney function, serious inflammatory reactions and risks from improper injection. Patients need blood tests and medical follow-up before and during treatment.
