FDA Approves Hibsago: First Antisense Drug for Hepatitis B

FDA approves Hibsago (bepirovirsen), GSK’s treatment for chronic hepatitis B, and the agency describes it as the first approved antisense oligonucleotide for the infection. The decision, announced on 20 October 2026, covers use with existing antiviral therapy in certain adults without cirrhosis. In the two supporting trials, 24% of patients on Hibsago met the criteria to stop their existing hepatitis B medicine, compared with none on placebo, and 19% still had undetectable hepatitis B surface antigen 24 weeks after stopping all treatment. The label carries a boxed warning for serious liver reactions and low platelet counts. This article is general information and not medical advice.

FDA approves Hibsago: key takeaways

• Hibsago (bepirovirsen) is approved with existing antiviral therapy for certain adults with chronic hepatitis B who do not have cirrhosis.
• To be eligible, patients must have taken antiviral therapy for at least six months, have suppressed virus levels and have hepatitis B surface antigen (HBsAg) of 3,000 IU/mL or less on an FDA-authorized test.
• In the trials, 24% of Hibsago patients met the criteria to stop their existing medicine versus none on placebo, and 19% kept viral control with undetectable HBsAg 24 weeks after stopping all treatment.
• The label has a boxed warning for serious liver reactions and low platelet counts that can raise the risk of life-threatening bleeding.
• The FDA does not say it is a cure for everyone; most eligible patients did not reach the stopping criteria.

Who is covered when FDA approves Hibsago

According to the FDA’s approval announcement, Hibsago is approved for use with existing antiviral therapy for chronic hepatitis B infection in certain adults without cirrhosis. Three conditions apply: the patient has taken hepatitis B antiviral therapy for at least six months, the virus is suppressed in the blood, and HBsAg is 3,000 IU/mL or less as measured by an FDA-authorized test. The agency also authorized the Roche Elecsys HBsAg II quant II RxDx assay to help select patients and to monitor them during treatment.

How Hibsago is given

Hibsago is injected under the skin for up to 24 weeks, alongside the patient’s existing hepatitis B medicine, per the FDA. The existing medicine continues for at least 24 weeks after the last Hibsago injection. Some patients may then be able to stop it if they meet certain health and laboratory requirements. Patients need regular blood tests and follow-up before and during treatment, and the agency warns of serious risks if the injection is not given correctly.

Trial evidence as FDA approves Hibsago

The FDA says two clinical trials compared Hibsago with placebo but does not name them or give enrolment. The numbers match the Phase III B-Well 1 and B-Well 2 trials, which GSK reported in May 2026; that link is our inference, not an FDA statement. In the GSK’s release on the Phase III B-Well results, the pooled primary analysis found functional cure in 19% of bepirovirsen patients (233 of 1,220) and 0% of placebo patients (0 of 614) at week 72, six months after stopping all treatment. In patients with HBsAg of 1,000 IU/mL or less, the rate was 26%. These are company-reported figures.

Two numbers that are easy to confuse

The 24% and 19% figures answer different questions. The 24% is the share of Hibsago patients who met the criteria to stop their existing medicine, a step that happens before treatment ends. The 19% is the share who still had controlled virus and undetectable HBsAg 24 weeks after stopping everything, often called functional cure. Neither number means a complete cure of the infection, and the large majority of patients did not reach either goal. By our subtraction, about four in five patients in the pooled trial analysis did not reach functional cure.

Safety when FDA approves Hibsago: boxed warning and other risks

The FDA highlights a boxed warning for serious liver reactions and for low platelet counts, which can raise the risk of potentially life-threatening bleeding. Other warnings include worsening kidney function and serious inflammatory reactions such as vasculitis. The most common adverse reactions, excluding laboratory abnormalities, were injection site reactions, fever, fatigue and headache. GSK’s trial release describes an acceptable safety profile and lists injection site redness, local pain and a temporary rise in a liver enzyme as the most frequent events.

Why FDA approves Hibsago as first-of-its-kind

This section is general background. An antisense oligonucleotide is a short piece of genetic material designed to bind a specific RNA message so that a protein is not made. The FDA says Hibsago targets the viral genetic instructions used to make viral copies and proteins, which lowers the amount of virus and HBsAg in the body. Existing hepatitis B medicines mainly suppress viral replication, so a drug aimed at reducing HBsAg is a different approach.

The hepatitis B burden as FDA approves Hibsago

The WHO hepatitis B fact sheet estimates that 240 million people were living with chronic hepatitis B in 2024, with about 1.1 million deaths a year, mostly from cirrhosis and liver cancer. It says 65 million people, or 27%, knew their status, and 10 million people, or 4.3%, were on antiviral treatment. It adds that most people who start treatment must continue it for life. That context shows why a regimen with a route to stopping treatment draws attention, and why the number of eligible patients will be limited by testing and treatment gaps.

What is not disclosed after FDA approves Hibsago

• Price, launch date and availability outside the United States.
• Enrolment and design details in the FDA announcement.
• Long-term durability of virus control after stopping treatment.
• Results in people with cirrhosis or higher HBsAg levels, who are outside the label.

Risks and caveats as FDA approves Hibsago

• Most patients in the trials did not meet the stopping criteria or functional cure.
• The boxed warning requires monitoring of liver tests and platelet counts.
• Trial figures in this article are from the FDA and GSK, and long-term data are not yet available.
• This is news reporting, not medical advice, and treatment choices belong with a liver specialist.

In our assessment, the Hibsago approval is an important step because it offers some patients a defined route toward stopping treatment, but the benefit is for a minority of eligible patients and comes with monitoring and safety demands. More in our pharmaceutical coverage.

What to watch next after FDA approves Hibsago

• Pricing, insurance coverage and launch timing.
• Real-world outcomes and safety reports.
• Regulatory decisions in other regions.

Frequently asked questions

What is Hibsago?

It is bepirovirsen, an antisense oligonucleotide from GSK, approved with existing antiviral therapy for certain adults with chronic hepatitis B without cirrhosis.

Is Hibsago a cure for hepatitis B?

No. In the trials, 19% had undetectable HBsAg and controlled virus 24 weeks after stopping all treatment, and most patients did not.

What is the boxed warning?

It covers serious liver reactions and low platelet counts, which can increase the risk of life-threatening bleeding.

How we reported this: we relied on the FDA’s announcement of 20 October 2026, GSK’s trial release and the WHO fact sheet. Our arithmetic, inference and general background are labelled. Last updated: 21 October 2026. This article is news reporting and not medical advice.