GSK plc (LSE: GSK) (NYSE: GSK) has received US Food and Drug Administration approval for Hibsago (bepirovirsen), a first-in-class antisense oligonucleotide for treating chronic hepatitis B in eligible adults alongside existing antiviral therapy. The approval follows priority review and Breakthrough Therapy Designation and addresses a condition affecting approximately 1.7 million people in the US.

Approval was supported by pooled Phase III B-WELL trial results showing a functional cure rate of 19% among patients with baseline hepatitis B surface antigen levels of up to 3,000 IU/ml, compared with none in the placebo group. Among patients with levels of up to 1,000 IU/ml, the functional cure rate reached 26%. Functional cure was defined as undetectable viral DNA and surface antigen for at least 24 weeks after all treatment stopped.

The six-month treatment demonstrated an acceptable safety and tolerability profile, with the most common adverse events including injection-site redness, local pain and temporary increases in liver enzyme levels. Eligible patients must meet specified clinical criteria, including the absence of cirrhosis and suppressed viral DNA.

GSK licensed bepirovirsen from Ionis Pharmaceuticals and collaborated on its development. The company continues to pursue regulatory submissions in other markets, with further decisions expected in the coming months.