Biopharmaceutical company GSK plc (LON:GSK) (NYSE:GSK) announced on Tuesday that the US Food and Drug Administration (FDA) has accepted its New Drug Application for bepirovirsen for priority review in adults with chronic hepatitis B.

The investigational antisense oligonucleotide has also been granted Breakthrough Therapy Designation, building on its earlier Fast Track status and indicating potential advantages over existing treatments.

The regulatory submission is supported by Phase III B-Well trials, in which bepirovirsen demonstrated statistically significant and clinically meaningful functional cure rates compared with standard of care alone. The therapy showed higher response rates across endpoints, particularly among patients with lower baseline hepatitis B surface antigen levels, alongside an acceptable safety and tolerability profile.

Chronic hepatitis B affects more than 250 million people globally and approximately 1.7 million in the United States, with current treatments typically requiring lifelong use and delivering low cure rates. Achieving a functional cure significantly reduces the risk of long-term complications, including liver cancer.

The FDA has set a Prescription Drug User Fee Act target action date of 26 October 2026. Bepirovirsen, licensed from Ionis Pharmaceuticals Inc (Nasdaq:IONS), remains investigational and has not yet been approved for use globally.