GSK (NYSE: GSK) has reported pivotal Phase III data showing that bepirovirsen, its antisense oligonucleotide (ASO) for chronic hepatitis B, achieved functional cure in 19% of treated patients versus 0% on standard of care alone. The result indicate that bepirovirsen is on course to become the first therapy capable of delivering meaningful functional cure rates if gaining market approval, in a disease affecting more than 240 million people worldwide. Bepirovirsen is currently under FDA Priority Review following NDA acceptance in April 2026, with a PDUFA date of October 26, 2026.
Pooled results from the randomized, double-blind, placebo-controlled B-Well 1 and B-Well 2 trials enrolled 1,834 nucleos(t)ide analogue (NUC)-treated adults with chronic hepatitis B and baseline hepatitis B surface antigen (HBsAg) ≤3,000 IU/mL across 29 countries. Both arms received background standard of care; the treatment arm added six months of bepirovirsen. The primary endpoint — functional cure, defined as undetectable HBsAg and HBV DNA below the limit of quantification for at least 24 weeks after stopping all treatment — was assessed at week 72. In the overall population, 19% of bepirovirsen recipients (233 of 1,220) achieved functional cure versus 0% on placebo (p < 0.001 in both trials). In patients with baseline HBsAg ≤ 1,000 IU/mL, a group representing roughly 45% of diagnosed chronic hepatitis B cases globally, the functional cure rate reached 26% (200 of 768 versus 0 of 393; p < 0.001). An exploratory analysis found that 49% of bepirovirsen recipients achieved quantitative HBsAg of ≤100 IU/mL one year after end of treatment, a threshold associated in the medical literature with increased immune control.
The safety profile was consistent with prior bepirovirsen studies; the three most common adverse events were injection site erythema, local pain, and a transient rise in liver enzyme levels.