GSK preps filings for chronic hepatitis B drug bepirovirsen

GSK's antisense-based drug for chronic hepatitis B (CHB), bepirovirsen, has hit the mark in two phase 3 trials and will be filed for approval as a potential first-in-class treatment for the disease.

In the B-Well 1 and B-Well 2 studies, which enrolled 1,800 patients across 29 countries, bepirovirsen achieved a significantly higher functional cure rate than placebo – in other words, more patients were able to clear a biomarker called hepatitis B surface antigen (HBsAg) from their blood and have it remain undetectable for at least 24 weeks after stopping treatment.

CHB is a major health challenge, affecting over 250 million people worldwide, and is the leading cause of liver cancer, accounting for more than half (56%) of all cases. It is linked to around 1.1 million deaths a year.

While achieving a functional cure is not the same as eradicating the hepatitis B virus (HBV), it can allow the immune system to control the infection without further medication and is associated with a significant reduction in the risk of long-term liver complications, including liver cancer, as well as all-cause mortality.

The data from the two studies hasn't been revealed yet, but GSK said the antisense drug, which is given as a weekly subcutaneous injection over six months, achieved higher functional cure rates regardless of patients' HBsAg levels at enrolment, with an "acceptable" safety and tolerability profile.

"Bepirovirsen has the potential to transform treatment goals for people living with CHB by achieving significant functional cure rates – a first for the disease," said Tony Wood, GSK's chief scientific officer.

"Today's result supports our plans to progress bepirovirsen as a treatment and also continue its development as a backbone in future sequential therapies," he added, noting that the drug will now be filed for approval around the world within the next three months. It picked up a fast-track designation from the FDA in 2024.

GSK is also running a long-term extension to the phase 2 B-Clear study, called B-Sure, which will follow patients for around three years and is due to report results in 2029.

Analysts at William Blair have previously suggested that the market for a hepatitis B functional cure could be around the same size as for hepatitis C virus (HCV), which peaked at around $10 billion a year, but was a short-lived bonanza, with sales falling sharply as the pool of patients eligible for treatment grew smaller.

GSK has modelled peak sales of around £2 billion ($2.5 billion) for bepirovirsen if it reaches the market.