GSK has secured a landmark approval in Japan for Hibsago (bepirovirsen) — described as the first-ever regulatory approval of a “functional cure” for chronic hepatitis B, a persistent viral infection that can lead to liver damage and cancer.
A “functional cure” means the virus is durably controlled — suppressed to undetectable levels without ongoing therapy — even if it isn’t fully eradicated. That’s a high bar: standard nucleos(t)ide analogue (NA) treatments achieve functional cure in only about 1% of patients, and usually must be taken indefinitely.
How it works
Developed with Ionis Pharmaceuticals, Hibsago is an antisense oligonucleotide (ASO) that targets and suppresses the virus’s genetic material, and also acts to stimulate an immune response against hepatitis B. Japan’s Ministry of Health, Labour and Welfare (MHLW) approved it in August 2026 for Japanese adults with chronic hepatitis B who have had at least six months of prior NA treatment and meet defined viral-marker criteria.
The data and the stakes
In the Phase 3 B-Well program, 19% of patients achieved a functional cure response after six months of Hibsago, versus 0% on placebo. While 19% leaves room to grow, it is a dramatic step up from roughly 1% with existing therapy. Analysts at GlobalData project Hibsago could approach blockbuster status, nearing $926 million in global sales by 2034 — and it establishes functional cure as a real regulatory category for a disease affecting hundreds of millions worldwide.