GSK and Ionis present pivotal data showing 19% functional cure for chronic hepatitis B

GSK (NYSE:GSK) and partner Ionis Pharmaceuticals (NASDAQ:IONS) announced positive data from two pivotal Phase 3 trials evaluating bepirovirsen, an investigational antisense oligonucleotide designed to treat chronic hepatitis B.

The pooled results from the late-stage programs demonstrate a significant improvement over the current global standard of care, which typically forces patients onto lifelong management routines.

The findings from the B-Well 1 and B-Well 2 trials were simultaneously published in the New England Journal of Medicine and presented at the European Association for the Study of the Liver congress.

The data reveal that a finite six-month treatment course with bepirovirsen achieved a 19% functional cure rate in the overall study population, which consisted of adults with baseline hepatitis B surface antigen levels at or below 3,000 international units per milliliter.

This compared to a 0% response rate in the placebo arm, meeting the primary confirmatory endpoints of both studies with high statistical significance.

A functional cure is defined as reducing the virus to undetectable levels in the bloodstream for at least six months after all medical therapies have stopped, allowing the patient's native immune system to keep the infection in check.

Under current nucleotide treatments, fewer than 1% of patients achieve this milestone.

The efficacy rate expanded further in a key secondary endpoint analyzing patients with lower baseline viral activity.

Within the group matching baseline levels at or below 1,000 units per milliliter—a segment accounting for roughly 45% of chronic hepatitis B cases globally—the functional cure rate climbed to 26%.

Long-term durability metrics also tracked positively during the clinical program.

An exploratory analysis found that 49% of bepirovirsen recipients managed to sustain ultra-low surface antigen levels one year post-treatment, a benchmark historically linked in medical literature to enhanced immune control and better overall clinical survival rates.

Furthermore, at week 72 of the study, 23% of the overall treated group and 31% of the lower baseline viral group maintained viral DNA below the lower limit of quantification.

The security and safety analysis from the pooled global trials indicated an acceptable tolerability profile, in line with prior mid-stage clinical studies for the compound.

The three most common side effects reported by trial participants included injection site redness, localized pain, and a temporary elevation in liver enzyme levels, which resolved without major clinical intervention.

GSK holds the operational license for bepirovirsen following a collaborative development and commercial agreement signed with Ionis.