FDA approved Hibsago (bepirovirsen) injection on October 20 for certain adults with chronic hepatitis B, to be taken alongside their existing antiviral treatment. Some patients may later qualify to stop all hepatitis B treatment, but the approval has defined eligibility and monitoring requirements.
Who qualifies
The approval covers certain adults without cirrhosis who have been taking hepatitis B antiviral medicine for at least six months, have suppressed virus levels in their blood and have hepatitis B surface antigen levels of 3,000 IU/mL or less, determined by an FDA-authorized test.
FDA also authorized a Roche companion diagnostic test to help select and monitor patients. Hibsago is the first FDA-approved antisense oligonucleotide for chronic hepatitis B: it targets genetic instructions the virus uses to make copies of itself and viral proteins. FDA granted the drug approval to GSK plc.
What the trials measured
Two clinical trials compared Hibsago with placebo. Patients receive injections under the skin for up to 24 weeks while continuing their existing hepatitis B medicine. They continue that medicine for at least 24 weeks after their last injection.
Across the trials, 24% of patients receiving Hibsago met the requirements to stop their existing medicine, compared with none receiving placebo. Twenty-four weeks after stopping all hepatitis B treatment, 19% of patients who received Hibsago still had the virus under control and had no detectable hepatitis B surface antigen.
Those are specific trial endpoints. FDA says stopping existing medicine depends on meeting health and laboratory requirements; it is not an automatic step for everyone receiving the injection.
The safety limits
Hibsago has a boxed warning for serious liver reactions and low platelet counts, which can increase the risk of potentially life-threatening bleeding. Other warnings cover worsening kidney function, serious inflammatory reactions such as vasculitis, and risks from incorrect administration.
FDA says patients need regular blood tests and healthcare-provider follow-up before and during treatment. The most common side effects, apart from laboratory abnormalities, include injection-site reactions, fever, fatigue and headache. The announcement does not give a price or commercial availability date.