The U.S. Food and Drug Administration approved GlaxoSmithKline’s antisense oligonucleotide Hibsago (bepirovirsen), a new therapy for some people with chronic hepatitis B that enabled a fraction of trial participants to stop long‑term antiviral treatment and achieve a functional cure.
Trial results and regulator's findings
The approval was based on data from two Phase 3 B‑WELL trials. In those studies, 24% of patients who received Hibsago satisfied criteria that allowed them to discontinue their regular antiviral medications, compared with 0% of participants given placebo. After 24 weeks off antivirals, 19% of treated patients had no detectable hepatitis B surface antigen (HBsAg) in the blood, a commonly used marker of a functional cure.
“Hibsago provides a new treatment approach that gives some patients the possibility of maintaining control of the virus after all chronic HBV treatment has ended. This approval represents an important advance for people living with this serious disease,” said Wendy Carter, acting director of the Office of Infectious Diseases in the FDA’s Center for Drug Evaluation and Research.
What a functional cure means
Regulators and researchers use the term functional cure to describe the sustained loss of HBsAg and maintained viral control without ongoing antiviral therapy, rather than complete eradication of the virus from the body. The B‑WELL trials measured whether patients could stop nucleos(t)ide antivirals and remain free of detectable viral proteins for a defined period.
- 24% of Hibsago recipients in the Phase 3 trials met criteria to discontinue antivirals; 0% in the placebo group did.
- 19% of treated patients had undetectable HBsAg after 24 weeks off antivirals, meeting a predefined measure of functional cure.
- The approval follows a competitive landscape of next‑generation hepatitis B therapies in development.
Industry context
The FDA action marks the first approval in a field where several companies are pursuing treatments intended to allow patients to stop lifelong antiviral regimens. Drug developers have tested approaches including antisense oligonucleotides, therapeutic vaccines, siRNA, and immune modulators. The approval gives physicians an additional therapeutic option for eligible patients with chronic hepatitis B and creates the first commercially available antisense treatment of this type in the United States.
GSK said the decision follows review of the B‑WELL program’s randomized data. The company and the FDA have not published all trial details in the material provided here; prescribing information and any FDA summaries will provide the full data set, including safety findings, eligibility criteria and recommended monitoring for patients who discontinue antivirals under the drug’s indication.
Health officials and clinicians will be watching postmarketing experience to better define which patients benefit most and to monitor long‑term durability of viral control after stopping antivirals.
