FDA Approves Hibsago (Bepirovirsen) for Chronic Hepatitis B

The six-month injectable from GSK and Ionis is the first FDA-approved antisense treatment for hepatitis B, and the first therapy that can give some adults a functional cure, letting them stop all treatment while keeping the virus in check.

On October 20, 2026, the FDA approved Hibsago (bepirovirsen), a first-of-its-kind treatment for chronic hepatitis B (CHB). Developed by Ionis and licensed to GSK, it is the first antisense oligonucleotide approved for the disease, and it offers something no existing hepatitis B drug can: the chance of a functional cure.

What Is Bepirovirsen and How Does It Work?

Bepirovirsen is an antisense oligonucleotide (ASO), a short strand of synthetic genetic material that binds to the virus's RNA and blocks it from making viral proteins. That brings down hepatitis B surface antigen (HBsAg), a protein that signals active infection, and may also give the immune system room to fight back. It is given as a subcutaneous injection for up to 24 weeks, with the option of self-administration after the first dose.

Unlike the nucleos(t)ide analogues (NrtIs) that most patients take indefinitely to suppress the virus, bepirovirsen is a time-limited, roughly six-month course. The FDA approved it in combination with NrtI therapy for adults without cirrhosis who have been on an NrtI for at least six months, have suppressed HBV DNA, and have HBsAg at or below 3,000 IU/mL. The agency also authorized a Roche companion diagnostic test to identify eligible patients.

Why a “Functional Cure” Matters

Chronic hepatitis B affects about 1.7 million people in the U.S. and more than 240 million worldwide, and it is a leading cause of liver cancer. Existing antivirals keep the virus suppressed but rarely clear it, so most patients face lifelong treatment. A functional cure — undetectable HBsAg and HBV DNA for at least 24 weeks after stopping all therapy — has long been the goal, because it lets patients stop daily medication and leaves their own immune system to keep the infection down.

What the Trials Showed

Approval was based on two pivotal Phase 3 trials, B-Well 1 and B-Well 2, which are global, randomized, double-blind, placebo-controlled studies run across 29 countries in NrtI-treated adults. Pooled across the trials, 19% of patients (233 of 1,220) with baseline HBsAg at or below 3,000 IU/mL achieved a functional cure, versus 0% on placebo. Among patients with lower baseline HBsAg (at or below 1,000 IU/mL), the rate rose to 26%. According to the FDA, 24% of bepirovirsen-treated patients met the criteria to stop their existing NrtI therapy altogether. The results were published in the New England Journal of Medicine.

For context, current standard-of-care antivirals produce a functional cure in fewer than 1% of patients after a year, a benchmark Ionis cited in calling the results “unprecedented.”

Safety and Warnings

Bepirovirsen's label carries two boxed warnings. The first is for on-treatment hepatic flares: sharp rises in the liver enzyme ALT, usually within the first 12 weeks, as HBsAg falls. The second is for thrombocytopenia, a drop in platelets that can be sudden and serious; the drug is contraindicated in patients whose platelet count is below 100 ×10⁹/L, and counts must be monitored at least weekly. It is also contraindicated in patients with cirrhosis. The most common adverse reactions were injection site reactions, fever, fatigue, and headache. Patients who stop their NrtI must be monitored for at least a year for severe hepatitis flares.

From the Experts

“This approval offers a new treatment approach that gives some patients the possibility of maintaining control of the virus,” said Wendy Carter, DO, acting director of the FDA’s Office of Infectious Diseases.

Ionis CEO Brett Monia, Ph.D., described bepirovirsen as a medicine “offering the potential to achieve unprecedented functional cure rates after a six-month treatment course,” while GSK Chief Scientific Officer Tony Wood said U.S. patients “have the potential to achieve functional cure after a six-month treatment course” for the first time.

Norah Terrault, MD, MPH, chief of gastroenterology and hepatology at USC’s Keck Medical Center, said “This is the start of a new era in treating people living with CHB.”