GSK Wins Japan Approval for Hibsago in Hepatitis B

LONDON, UK, Aug 24, 2026

GSK’s Bepirovirsen Delivers Functional Cure Results

The Japanese approval was supported by results from the global B-Well Phase 3 trials, which evaluated the efficacy, safety, pharmacokinetic profile and durability of bepirovirsen in adults with chronic hepatitis B receiving nucleos(t)ide analogue therapy. Pooled results showed that six months of treatment with bepirovirsen achieved a 19% functional cure rate, representing 233 of 1,220 participants with baseline hepatitis B surface antigen (HBsAg) levels of ≤3,000 IU/mL, compared with no functional cures among 614 participants receiving placebo. The difference was statistically significant, with p<0.001 in both trials. In a key secondary analysis involving participants with baseline HBsAg levels of ≤1,000 IU/mL, the functional cure rate reached 26%, compared with zero in the placebo group. Exploratory analyses further showed that 49% of participants in the overall study population reduced HBsAg to ≤100 IU/mL by the Week 72 assessment, while the proportion reached 62% among those with baseline HBsAg ≤1,000 IU/mL. GSK reported an acceptable safety and tolerability profile, with injection-site erythema, local pain and temporary liver enzyme elevations among the most frequently observed adverse events.

Antisense Oligonucleotide Targets HBV Viral Components

Bepirovirsen is an antisense oligonucleotide (ASO) designed to target hepatitis B virus RNA and reduce the production of viral components, including HBV proteins and hepatitis B surface antigen (HBsAg). By lowering viral protein production and stimulating immune responses, the treatment is intended to help the immune system regain control of chronic HBV infection. A functional cure is defined in the B-Well program as undetectable HBsAg and HBV DNA for at least 24 weeks after stopping treatment, indicating that the infection remains controlled without continued antiviral medication. This treatment goal is particularly important because many people living with chronic hepatitis B currently require long-term or lifelong antiviral therapy to maintain viral suppression. GSK stated that Hibsago could potentially allow eligible patients to move beyond continuous therapy following a six-month treatment course, although the approved indication and treatment requirements in Japan determine its clinical use.

Japan Approval Advances Global Hepatitis B Strategy

The approval is significant for GSK’s hepatology strategy as the company continues regulatory submissions for bepirovirsen across multiple geographic markets, including the United States. Chronic hepatitis B remains a major global health challenge and a leading cause of liver cancer, with the disease affecting more than 240 million people worldwide according to the information provided by GSK. In Japan, nearly one million people are living with chronic hepatitis B, while the disease contributes to thousands of deaths annually. The Japanese government has also implemented nationwide screening and treatment initiatives to improve identification and management of viral hepatitis. Hibsago’s approval therefore introduces a new treatment approach focused on achieving functional cure rather than long-term viral suppression alone. GSK licensed bepirovirsen from Ionis and collaborated with the company during its development. The therapy has received regulatory recognition in several regions, including FDA Fast Track and Breakthrough Therapy designations, as well as regulatory designations in China and Japan. The Japanese decision marks an important milestone for GSK and chronic hepatitis B treatment development, while further regulatory decisions remain pending in other markets. Bepirovirsen’s Phase 3 results and its first global approval position the therapy as a significant addition to GSK’s hepatology portfolio, with ongoing development focused on expanding its potential role in functional cure strategies for chronic hepatitis B.

Source: GSK press release