GSK (LSE:GSK) said the US Food and Drug Administration has accepted for priority review a New Drug Application for bepirovirsen and has granted the antisense candidate Breakthrough Therapy Designation.
The regulatory filing is supported by positive Phase III B‑Well 1 and B‑Well 2 results that showed statistically significant and clinically meaningful functional cure rates when bepirovirsen was added to standard of care, with an acceptable safety and tolerability profile consistent with previous studies.
Breakthrough Therapy Designation builds on an earlier Fast Track designation awarded in February 2024 and is intended to secure more intensive FDA guidance on the asset's development programme. The FDA has assigned 26 October as the Prescription Drug User Fee Act goal date.
Chronic hepatitis B affects more than 250 million people worldwide and an estimated 1.7 million in the United States, and current nucleos(t)ide analogue therapy typically achieves functional cure in roughly 1% of patients.
B‑Well 1 and B‑Well 2 were global, randomised, double‑blind, placebo‑controlled Phase III trials across 29 countries that enrolled participants on nucleos(t)ide analogue therapy with baseline HBsAg ≤3000 IU/ml and used functional cure-undetectable HBsAg for at least 24 weeks after stopping treatment-as the primary endpoint, with a ranked secondary endpoint for HBsAg ≤1000 IU/ml.
Bepirovirsen is an antisense oligonucleotide licensed from Ionis Pharmaceuticals designed to reduce HBV RNA and surface antigen, inhibit viral replication and stimulate immune responses as a route to durable functional cure.
GSK plans to present the B‑Well data at the European Association for the Study of the Liver Congress and to submit the results for peer‑reviewed publication in 2026, and bepirovirsen is not approved anywhere in the world.
