Japan Reviews GSK’s Bepirovirsen for Hepatitis B

GSK plc has announced that Japan’s Ministry of Health, Labour and Welfare (MHLW) has accepted for review a new drug application for bepirovirsen, an investigational antisense oligonucleotide (ASO) designed to treat adults living with chronic hepatitis B (CHB).

Chronic hepatitis B remains a major global health burden, affecting more than 250 million people worldwide and nearly one million individuals in Japan alone. Despite the availability of nucleos(t)ide analogue therapies, which suppress viral replication, most patients require lifelong treatment. Functional cure rates under current standard of care remain low—typically around 1%. A functional cure is defined as sustained, undetectable levels of hepatitis B virus (HBV) DNA and hepatitis B surface antigen (HBsAg) in the blood for at least 24 weeks after stopping therapy, allowing the immune system to control the virus without ongoing medication.

Achieving functional cure is associated with a substantially reduced risk of long-term complications, including cirrhosis and liver cancer. Globally, chronic hepatitis B is estimated to account for approximately 56% of liver cancer cases, underscoring the urgent need for more effective therapies.

The Japanese regulatory submission is supported by positive data from the Phase III B-Well 1 and B-Well 2 trials. In these studies, bepirovirsen combined with standard of care demonstrated statistically significant and clinically meaningful improvements in functional cure rates compared with standard therapy alone. Benefits were observed across all ranked endpoints, with particularly strong effects in patients who had lower baseline HBsAg levels. The drug also showed an acceptable safety and tolerability profile consistent with earlier-stage studies.

Bepirovirsen received SENKU designation in Japan in August 2024, a status granted to innovative medicines targeting serious diseases with high unmet need. The designation is intended to accelerate regulatory review and facilitate earlier patient access.

Clinical data from the Phase III programme are expected to be presented at a scientific congress and submitted for peer-reviewed publication in 2026. If approved, bepirovirsen could represent a significant step forward in the pursuit of functional cures for chronic hepatitis B in Japan.