GSK has secured Japanese approval for (Hibsago) bepirovirsen, an antisense oligonucleotide (ASO) licensed from Ionis Pharmaceuticals, as a functional cure regimen for chronic hepatitis B (CHB) in adults previously treated with nucleos(t)ide analogues for at least six months and meeting viral marker thresholds, making it the first asset globally to achieve this label. The approval rests on the Phase III B-Well 1 and B-Well 2 trials, where bepirovirsen delivered significantly higher functional cure rates than placebo in patients with baseline HBsAg no greater than 3,000 IU/mL, with stronger effect below 1,000 IU/mL.

Bepirovirsen acts by suppressing hepatitis B virus (HBV) DNA replication, lowering circulating HBsAg, and stimulating durable immune response, addressing a disease affecting over 240 million people worldwide with no finite-course cure under standard lifelong antiviral therapy. At an estimated global CHB population of 75 million in China and 1.7 million in the US, even a 20% to 35% functional cure rate in selected low-HBsAg subgroups represents a multi-billion-dollar commercial opportunity, though uptake will hinge on diagnostic stratification and payer willingness to fund a short-course oligonucleotide against cheap generic nucleos(t)ides.