On Oct. 20, 2026, GSK announced that the U.S. Food and Drug Administration (FDA) has approved Hibsago (bepirovirsen) for the treatment of chronic hepatitis B (CHB) virus infection in combination with nucleos(t)ide analogue reverse transcriptase inhibitor (NrtI) therapy in adult patients without cirrhosis, receiving Nrtl therapy for at least 6 months, who have suppressed HBV deoxyribonucleic acid (DNA), and with hepatitis B virus (HBV) surface antigen (HBsAg) levels ≤3000 IU/ml, as determined by an FDA-authorised test. Bepirovirsen is a first-in-class antisense oligonucleotide (ASO) and offers unprecedented functional cure rates compared to current standard of care. The approval was granted under FDA Priority Review and Breakthrough Therapy Designation, recognizing significant improvement of bepirovirsen and nucleos(t)ide analog therapy over existing standard of care.

The approval was supported by results from the B-Well phase III trials showing functional cure rates of 19% in adults with ≤3000 IU/ml HBsAg, compared to current standard of care alone, which typically achieves less than 1% functional cure rate after one year of treatment. Functional cure occurs when HBV DNA and viral protein – HBsAg – are undetectable for at least 24 weeks after stopping all treatment, indicating the disease is controlled by the immune system without medication.

Quantitative surface antigen testing will support the diagnosis and identification of patients suitable for treatment with bepirovirsen who have baseline HBsAg levels ≤3000 IU/ml. Several tests are available, including a recently authorized FDA test. GSK continues to advance regulatory submissions for bepirovirsen across multiple geographies with key regulatory decisions anticipated in the coming months.

Pooled data from the B-Well phase III trials showed that six-month treatment with bepirovirsen achieved a clinically meaningful 19% functional cure response rate (233 of 1,220 vs. 0 of 614 in the placebo group). B-Well 1 and B-Well 2 each met the primary endpoint, demonstrating a statistically significant improvement in functional cure versus placebo in the overall study population (adults with ≤3000 IU/ml HBsAg level). In a key secondary endpoint, a functional cure rate of 26% (200 of 768 vs. 0 of 393 in the placebo group) was achieved in participants with ≤1000 IU/ml HBsAg level, a group that represents approximately 45% of diagnosed CHB cases globally.

Exploratory analyses also showed bepirovirsen reduced HBsAg to ≤100 IU/ml in 49% of participants (598 of 1220) in the overall study population, and in 62% of bepirovirsen recipients in the ≤1000 IU/ml (476 of 768) subgroup11 as of the week 72 visit. Medical literature has linked this low level of surface antigen with increased immune control and improved patient outcomes. The trials showed an acceptable safety and tolerability profile consistent with other studies of bepirovirsen. The three most frequently observed adverse events were injection site erythema, local pain and temporary rise in the blood level of a liver enzyme.

Bepirovirsen is an antisense oligonucleotide (ASO) designed to recognize and inhibit the production of the genetic components (i.e., RNA) of the hepatitis B virus that can lead to chronic disease, potentially allowing a person’s immune system to regain control. Bepirovirsen reduces the production of RNA and viral proteins associated with HBV, suppresses the level of hepatitis B surface antigen (HBsAg) in the blood, and may stimulate the immune system to increase the chances of a durable and sustained response.

GSK licensed bepirovirsen from Ionis and collaborated with them on its development. Bepirovirsen has been recognized by global regulatory authorities for its innovation and potential to address significant unmet need in hepatitis B, with Breakthrough Designation and Priority Review from the US FDA, Breakthrough Therapy and Priority Review designation in China and SENKU designation in Japan. Bepirovirsen is approved in Japan and the US.