GSK's Breakthrough Hepatitis B Therapy Meets Primary Endpoints in Phase 3 Trials, Regulatory Filing Imminent

GlaxoSmithKline PLC (GSK.US) announced today that bepirovirsen, an investigational antisense oligonucleotide (ASO) therapy developed in collaboration with Ionis Pharmaceuticals, has achieved positive results in two pivotal Phase 3 clinical trials, B-Well 1 and B-Well 2, for the treatment of chronic hepatitis B (HBV). Both trials successfully met their primary endpoints. Bepirovirsen demonstrated a statistically significant and clinically meaningful functional cure rate. GSK plans to initiate global regulatory submissions in the first quarter of 2026. Chronic hepatitis B represents a major global health challenge, affecting over 250 million people and has become a leading cause of liver cancer. Currently, standard treatments based on nucleos(t)ide analogues often require long-term, sometimes lifelong, medication, yet the functional cure rate remains low, typically around only 1%. B-Well 1 and B-Well 2 are global, multicenter, randomized, double-blind, placebo-controlled trials designed to evaluate the efficacy, safety, pharmacokinetic profile, and durability of functional cure with bepirovirsen in chronic hepatitis B patients receiving nucleos(t)ide analogue therapy with baseline HBsAg ≤3000 IU/ml. The primary endpoint was the proportion of patients with baseline HBsAg ≤3000 IU/ml achieving a functional cure. A key secondary endpoint was the proportion of patients with baseline HBsAg ≤1000 IU/ml achieving a functional cure. Functional cure was defined as HBsAg loss and undetectable HBV DNA for at least 24 weeks after the end of a finite treatment course. Analysis showed that the B-Well trials met the primary endpoint, with bepirovirsen demonstrating a statistically significant and clinically meaningful functional cure rate. Compared to standard therapy alone, bepirovirsen combined with standard therapy significantly increased the functional cure rate. Statistical significance was achieved across all endpoints, including in patients with baseline HBsAg ≤1000 IU/ml, where an even stronger effect was observed. The trials also indicated that bepirovirsen had a favorable safety and tolerability profile, consistent with previous study results. Bepirovirsen is an investigational ASO therapy with a triple mechanism of action, designed to recognize and destroy the genetic components (i.e., RNA) of the hepatitis B virus, potentially enabling a patient's immune system to regain control over the viral infection.