FDA approves Hibsago for certain adults with chronic hepatitis B

Across the pooled B-Well Phase III trials, 19% of adults treated with Hibsago met GSK's functional-cure measure 24 weeks after stopping treatment, compared with 0 of 614 placebo recipients, the company said. The FDA approved Hibsago with existing antiviral therapy for adults with chronic HBV without cirrhosis who have been on antiviral treatment at least 6 months, have suppressed HBV DNA, and have HBsAg of 3,000 IU/mL or less on an FDA-authorized test, the agency said.

Why it matters

The FDA said many people with chronic hepatitis B take antiviral medication for years to keep the virus suppressed. Its approval adds an option to existing treatment for adults who meet a defined set of liver, treatment-history, and blood-test criteria. The FDA also authorized the Roche Elecsys HBsAg II quant II RxDx assay to help select patients and monitor them during treatment.

Approval scope and date

The FDA announced the approval on October 20, 2026. Hibsago is the first FDA-approved antisense oligonucleotide for chronic hepatitis B, the agency said. The approved population is adults without cirrhosis who have received antiviral therapy for at least 6 months, have suppressed HBV in their blood, and have HBsAg levels of 3,000 IU/mL or less, as measured by an FDA-authorized test.

The FDA approved Hibsago for use with existing antiviral therapy. It did not describe the injection as a replacement for ongoing treatment at the start of the course. Patients take Hibsago with their existing hepatitis B medicine and continue that medicine for at least 24 weeks after the last Hibsago injection. Some patients may then stop their existing medicine if they meet health and lab-test requirements, according to the FDA.

B-Well trial results

GSK said the approval was supported by B-Well 1 and B-Well 2, randomized, double-blind, placebo-controlled Phase III trials conducted in 29 countries. The studies evaluated efficacy, safety, pharmacokinetics, and durability of functional cure in adults with chronic hepatitis B who were receiving nucleos(t)ide analogue treatment and had baseline HBsAg of 3,000 IU/mL or less.

Across the pooled trials, 233 of 1,220 adults who received bepirovirsen met the functional-cure measure, compared with 0 of 614 participants who received placebo, GSK said. The company said the primary measure required the result to persist for at least 24 weeks after all treatment stopped. In the subgroup with baseline HBsAg of 1,000 IU/mL or less, GSK reported a 26% response rate, or 200 of 768 participants, compared with 0 of 393 in the placebo group. GSK described this as a key ranked secondary measure.

The FDA separately reported that 24% of patients who received Hibsago met requirements to stop their existing medicine, compared with none who received placebo. That measure is distinct from the post-treatment result: 19% of Hibsago recipients still had the virus under control and had no detectable HBsAg in their blood 24 weeks after stopping all hepatitis B treatment, the FDA said.

How treatment is given

The FDA said Hibsago is injected under the skin for up to 24 weeks. Patients continue their existing hepatitis B medicine during the course and for at least 24 weeks after the last injection. The FDA said some patients may be able to stop that medicine after the additional period if they meet health and lab-test requirements. GSK said the six-month course allows self-administration after the first dose.

The FDA authorized the Roche Elecsys HBsAg II quant II RxDx assay as a companion diagnostic. The agency said the test helps identify patients for treatment in accordance with the approved drug labeling and supports monitoring through the course of treatment.

Safety and follow-up

Hibsago has a boxed warning for serious liver reactions and low platelet counts, which can increase the risk of potentially life-threatening bleeding, the FDA said. The agency also listed warnings for worsening kidney function, serious inflammatory adverse reactions such as vasculitis, and serious risks if the injection is not administered properly. Patients need regular blood tests and follow-up with a health care provider before and during treatment to monitor these risks.

The most common side effects, excluding laboratory abnormalities, are injection site reactions, fever, fatigue, and headache, according to the FDA. GSK reported that the most frequently observed adverse events in the trials were injection-site erythema, local pain, and a temporary rise in a liver enzyme.

GSK said it continues regulatory submissions for bepirovirsen in other geographies, with decisions anticipated in the coming months. The company licensed bepirovirsen from Ionis and collaborated with Ionis on development.