FDA approves hepatitis B drug that lets some patients stop pills

The US Food and Drug Administration approved Hibsago (bepirovirsen) on 20 October 2026 for some adults with chronic hepatitis B. It is the first antisense medicine licensed for the infection, and it is meant to be used for a fixed course of up to 24 weeks alongside the antiviral tablets people already take.

The goal is different from current care. Today most people with chronic hepatitis B take nucleoside or nucleotide analogue tablets, such as tenofovir or entecavir, for years and often for life. Those tablets keep the virus suppressed but rarely clear it. Bepirovirsen aims for a "functional cure": the virus stays undetectable and the surface antigen, a protein that marks ongoing infection, disappears from the blood even after all treatment stops.

In two phase 3 trials, about one in five people treated with bepirovirsen reached that goal. Nobody on placebo did. The approval comes with a boxed warning, though, and the drug is not yet licensed in the UK or the EU.

What the FDA approved

According to the FDA announcement, Hibsago is approved for adults without cirrhosis who:

• have taken hepatitis B antiviral therapy for at least six months
• have suppressed levels of the virus in their blood
• have hepatitis B surface antigen (HBsAg) levels of 3,000 IU/mL or less, measured with an FDA-authorised test

The FDA also authorised a Roche blood test, the Elecsys HBsAg II quant II RxDx assay, as a companion diagnostic. It helps doctors pick suitable patients and track them during treatment.

GSK, which licensed bepirovirsen from Ionis Pharmaceuticals, holds the approval. The FDA granted Fast Track, Breakthrough Therapy and Priority Review designations along the way. GSK says the drug is also approved in Japan.

Why hepatitis B is hard to clear

Hepatitis B becomes chronic when the immune system fails to clear the virus. GSK cites estimates that more than 240 million people live with chronic infection worldwide and that the disease causes about 1.1 million deaths a year. It is the leading cause of liver cancer globally.

The virus is hard to remove because it keeps a stable copy of its DNA inside the nucleus of infected liver cells. Antiviral tablets stop new virus being made, but they do not touch that reservoir. When people stop the tablets, the virus usually comes back. That is why most patients stay on treatment indefinitely, with regular blood tests and liver scans.

The surface antigen is a useful marker here. Infected cells keep releasing it even when the tablets have pushed the virus itself down to undetectable levels. Losing it is linked with better long-term outcomes, which is why researchers made HBsAg loss the core of the functional cure definition.

How bepirovirsen works

Bepirovirsen is an antisense oligonucleotide, a short synthetic strand of genetic material. It is designed to recognise the RNA the hepatitis B virus uses to make copies of itself and its proteins. By blocking that RNA, it lowers the amount of virus and surface antigen in the body.

GSK says the drug may also help the immune system regain control of the infection. That matters because functional cure depends on the body keeping the virus in check once treatment ends.

It is given as an injection under the skin. GSK says patients can choose to inject it themselves after the first dose.

The B-Well trials

The approval rests on two near-identical phase 3 trials, B-Well 1 and B-Well 2. Results were published in the New England Journal of Medicine.

What the trials found

The NEJM abstract reports a functional cure in:

GSK's pooled figure is 19% (233 of 1,220 against 0 of 614). The FDA describes the same result in plainer terms. Across both trials, 24% of people on Hibsago met the requirements to stop their existing medicine, against none on placebo. Twenty-four weeks after stopping all treatment, 19% still had the virus under control with no detectable HBsAg.

The effect was larger in people who started with lower antigen levels. In a ranked secondary analysis of people with baseline HBsAg of 1,000 IU/mL or less, 26% reached a functional cure (200 of 768 against 0 of 393). GSK estimates that this group makes up about 45% of diagnosed chronic hepatitis B cases worldwide.

How to read a 19% cure rate

A one-in-five chance can sound modest. Two points help put it in context.

First, the comparison is stark. On placebo, nobody reached a functional cure. GSK says current tablet treatment alone typically gives a functional cure rate below 1% after a year.

Second, a functional cure is not the same as eradication. The virus's DNA can persist in liver cells, so people who reach a functional cure still need follow-up. The trials have so far reported outcomes six months after treatment stopped. Longer follow-up will show how durable the response is and whether it lowers the risk of cirrhosis and liver cancer, which is the long-term aim.

Four in five people in the trials did not reach a functional cure. For them, the practical outcome is continuing their tablets.

Safety and the boxed warning

The FDA label carries a boxed warning, its strongest, for serious liver reactions and for low platelet counts, which can raise the risk of potentially life-threatening bleeding. There are also warnings for worsening kidney function, serious inflammatory reactions such as vasculitis, and risks if the injection is not given properly. Patients need regular blood tests before and during treatment.

In the pooled NEJM data at 72 weeks:

• adverse events occurred in 91% on bepirovirsen and 73% on placebo
• serious adverse events occurred in 7% and 4%
• grade 3 or worse events during treatment occurred in 16% and 3%
• the most common grade 3 event with bepirovirsen was a rise in the liver enzyme ALT, in 6% of patients

The FDA lists injection site reactions, fever, fatigue and headache as the most common side effects outside lab changes. A rise in liver enzymes during treatment is not always harmful in hepatitis B, since it can reflect the immune system attacking infected cells. That is one reason for close monitoring.

Who might benefit

The label narrows the field. Bepirovirsen is for people who are already on antiviral tablets with the virus suppressed, who do not have cirrhosis, and whose HBsAg levels are relatively low.

A quantitative HBsAg blood test is needed to check eligibility. Many people with chronic hepatitis B worldwide are not diagnosed or not on treatment at all, and they would not qualify without first starting standard care.

UK and EU access

Bepirovirsen is not licensed in the UK or the EU at the time of writing.

GSK says further regulatory decisions are expected "in the coming months". No UK or EU price has been published. In the UK, chronic hepatitis B care is largely run through specialist hepatology services, and NHS use would normally follow an MHRA licence and NICE appraisal.

What happens next

Several questions remain:

Anyone on hepatitis B treatment should keep taking their tablets and ask their specialist whether they might qualify once it is licensed locally.

This article explains published research and isn't medical advice. Talk to your own doctor or specialist team before changing any treatment.