GSK Announces Positive Phase 3 Results for Bepirovirsen in Chronic Hepatitis B, Paving the Way for Global Regulatory Submissions

GSK (GSK.US) announced today that bepirovirsen, an investigational antisense oligonucleotide (ASO) therapy developed in collaboration with Ionis Pharmaceuticals, 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 met their primary endpoints. Bepirovirsen demonstrated a statistically and clinically significant rate of functional cure. GSK plans to initiate global regulatory submissions in the first quarter of 2026.

Chronic hepatitis B is a major health challenge worldwide, affecting more than 250 million people and has become one of the leading causes of liver cancer. Currently, the standard treatment based on nucleos(t)ide analogues often requires long-term or even lifelong medication, but its functional cure rate remains low, typically only about 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 of bepirovirsen in chronic hepatitis B patients receiving nucleos(t)ide analog therapy with baseline HBsAg ≤3000 IU/ml. The primary endpoint is the proportion of patients with baseline HBsAg ≤3000 IU/ml achieving functional cure. A key secondary endpoint is the proportion of patients with baseline HBsAg ≤1000 IU/ml achieving functional cure. Functional cure is defined as HBsAg loss and undetectable HBV DNA for at least 24 weeks after the end of a finite course of treatment.

Analysis shows that the B-Well trial met its primary endpoint, with bepirovirsen demonstrating a statistically significant and clinically meaningful functional cure rate. Compared to standard treatment alone, the combination of bepirovirsen and standard treatment significantly improved the functional cure rate. Statistical significance was achieved across all endpoints, including in patients with baseline HBsAg ≤1000 IU/ml, where a stronger effect was observed. The trial also showed that bepirovirsen had good safety and tolerability, consistent with previous study results.

Bepirovirsen is an investigational ASO therapy with a triple mechanism of action, designed to identify and disrupt the genetic components (i.e., RNA) of the hepatitis B virus, potentially enabling the patient's immune system to regain control over the viral infection.