GSK (NYSE:GSK) and partner Ionis Pharmaceuticals (NASDAQ:IONS) announced on Tuesday, April 28, 2026, that the U.S. Food and Drug Administration (FDA) has accepted the New Drug Application (NDA) for bepirovirsen and granted it Priority Review.
The investigational antisense oligonucleotide (ASO) is being evaluated as a potential "functional cure" for adults with chronic hepatitis B (CHB).
The FDA also awarded bepirovirsen Breakthrough Therapy designation, a status reserved for medicines that show preliminary clinical evidence of substantial improvement over existing treatments for serious conditions.
The agency has set a Prescription Drug User Fee Act (PDUFA) target action date of October 26, 2026.
Currently, over one million people in the U.S. and 250 million worldwide live with CHB, many of whom require lifelong antiviral therapy that rarely achieves a functional cure—defined as undetectable viral DNA and surface antigens (HBsAg) for at least 24 weeks after stopping treatment.
Bepirovirsen is designed to reduce viral replication, suppress HBsAg, and stimulate the immune system to allow for long-term control without medication.
The application is supported by positive results from the Phase 3 B-Well 1 and B-Well 2 trials, which showed significantly higher functional cure rates when bepirovirsen was added to the standard of care.
Full data from these studies will be presented at the EASL 2026 Congress in May.
Under the terms of their 2019 agreement, Ionis is eligible for further regulatory and sales milestone payments from GSK, as well as tiered royalties between 10% and 12% on net sales.
Bepirovirsen is also undergoing regulatory review in Europe, China, and Japan, having already received Breakthrough and SENKU designations in the latter two markets.