GSK said Tuesday its experimental hepatitis B drug Bepirovirsen met primary goals in two global phase 3 trials, showing higher functional cure rates than standard treatment and setting up regulatory filings in early 2026.
Phase 3 Trials Show Higher Functional Cure Rates
GSK said the late-stage B-Well 1 and B-Well 2 trials evaluated Bepirovirsen in more than 1,800 patients with chronic hepatitis B across 29 countries. The GSK Hepatitis B drug was tested alongside standard nucleos(t)ide analogue therapy.
Both studies met their primary endpoints, demonstrating statistically significant and clinically meaningful higher functional cure rates compared with standard of care alone. The effect was observed in patients with baseline hepatitis B surface antigen, or HBsAg, levels below 3,000 IU per milliliter.
A functional cure in the trials was defined as loss of HBsAg and undetectable hepatitis B virus DNA for at least 24 weeks after treatment ended. GSK said results were consistent across all ranked endpoints.
The strongest responses were seen in patients with HBsAg levels below 1,000 IU per milliliter, where the company said an even greater treatment effect was demonstrated.
Safety Profile Supports Regulatory Filing Plans
GSK said Bepirovirsen showed an acceptable safety and tolerability profile, consistent with findings from earlier studies. No new safety signals were reported in the phase 3 program.
The company said it plans to present detailed trial data at a future medical conference. Based on the results, GSK said it will begin regulatory submissions to health authorities, including the U.S. Food and Drug Administration, in the first quarter of this year.
If approved, Bepirovirsen could become the first finite, six-month treatment designed to achieve a functional cure for chronic hepatitis B, the company said.
“Bepirovirsen has the potential to transform treatment goals for people living with chronic hepatitis B by achieving significant functional cure rates, a first for the disease,” GSK Chief Scientific Officer Tony Wood said in a statement.
Wood said chronic hepatitis B affects more than 250 million people worldwide and accounts for about 56 percent of liver cancer cases globally.
“Today’s result supports our plans to progress Bepirovirsen as a treatment and to continue its development as a backbone for future sequential therapies,” he said.
Ionis Partnership and Broader GSK Hepatitis B Drug Strategy
Bepirovirsen is an antisense oligonucleotide licensed from Ionis Pharmaceuticals in 2019 for an upfront payment of $25 million. The GSK Hepatitis B drug is designed to reduce viral replication, suppress hepatitis B surface antigen, and help restore immune control of the virus.
Ionis CEO Brett Monia said the drug’s mechanism positions it well for treating chronic hepatitis B.
“Bepirovirsen is uniquely positioned to effectively treat chronic hepatitis B based on its potential to reduce viral replication, suppress hepatitis B surface antigen, and stimulate the immune system,” Monia said in a statement.
GSK has narrowed its hepatitis B pipeline in recent years. In 2025, the company dropped development of a therapeutic vaccine, GSK3528869, after disappointing trial results.
The company continues to advance other experimental hepatitis B treatments, including an siRNA therapy, GSK5637608; a PAPD5 and PAPD7 inhibitor, GSK3965193; and a TLR8 agonist, GSK5251738.
Analysts have long viewed a functional cure for chronic hepatitis B as a major unmet medical need. Current therapies typically require lifelong treatment and rarely eliminate the virus.
GSK said Bepirovirsen could serve as a foundation for future combination or sequential treatment strategies aimed at improving cure rates and reducing long-term disease burden.
