Initially, 28-29% of patients with chronic hepatitis B achieved undetectable virus levels after 24 weeks of treatment with GSK’s bepirovirsen, but this dropped to 9-10% of patients during a phase 2b trial.
GlaxoSmithKline’s end-of-study results from a phase 2b trial for their hepatitis B treatment bepirovirsen found its efficacy dropped more than 60% from the interim analysis to the end of study analysis.
However, GSK is continuing with phase 3 trials for the antisense oligonucleotide treatment, in hopes that it will still benefit patients with low baseline hep B surface antigen levels.
“Today’s results from the B-Clear study are a promising step forward for the approximately 300 million people living with chronic hepatitis B,” said Chris Corsico, senior vice president of Development at GSK.
In the B-Clear phase 2b trial, chronic hep B patients received a 300 mg weekly dose of bepirovirsen for 24 weeks.
Bepirovirsen is an antisense oligonucleotide that targets all HBV messenger RNAs, working to decrease levels of viral proteins.
Results demonstrated 9% of patients receiving stable nucleoside/nucleotide analogues (NA) treatment, and 10% of patients not on NA treatment, achieved a sustained clearance of hep B surface antigen levels and hep B virus (HBV) DNA levels.
These phase 2b trial findings follow more promising results reported in June 2022. The initial data showed 28-29% of participants had undetectable HBV levels after 243 weeks of bepirovirsen treatment.
GSK stated this drop in efficacy could be partially attributed to some participants relapsing after these first 24 weeks of treatments, meaning their hep B infection subsequently returned to detectable levels.
The biopharmaceutical company noted that even this 10% efficacy rate is tenfold higher than the current standard of care for patients living with chronic hepatitis B.
“We look forward to confirming these findings for bepirovirsen in our phase 3 study starting next year,” Corsico said, “as well as exploring potential sequential therapy options with the aim of helping more people living with [chronic hepatitis B] achieve functional cure.”
GSK is moving forward with trials due to positive results among an at-risk patient subgroup who could benefit the most from the therapy. Among participants with low baseline hep B surface antigen levels, 16% of those also taking NAs achieved clearance of detectable HBV, and 25% not taking NAs cleared the virus.
GSK maintains that larger and longer trials are needed to fully assess the safety and efficacy of bepirovirsen for chronic hepatitis B.