The US Food and Drug Administration (FDA) approved GSK’s Hibsago (bepirovirsen) on October 20, 2026, for certain adults with long-lasting (chronic) hepatitis B infection who do not have cirrhosis, a form of severe liver scarring1. The approval came six days before the target decision date the agency had set, October 262. It is the first treatment of its kind for hepatitis B: an antisense oligonucleotide, a short man-made strand of genetic material that sticks to the virus’s genetic messages so they get broken down13.
What sets it apart is the goal. Today’s standard pills, called nucleoside or nucleotide analogues, keep the virus suppressed, and many patients take them for life3. Hibsago is a fixed six-month course meant to give some people a “functional cure”: the virus stays undetectable in the blood for at least 24 weeks after they stop all hepatitis B treatment34.
“For many people living with chronic hepatitis B, treatment can mean taking antiviral medication for years to keep the virus suppressed,” Wendy Carter, DO, acting director of the Office of Infectious Diseases in the FDA’s Center for Drug Evaluation and Research, said in the announcement.
That quote was reported by GI & Hepatology News1.
What the trials showed
The approval rests on two identical trials, B-Well 1 and B-Well 2. Both were randomized (patients assigned by chance), double-blind (neither patients nor doctors knew who got what) and placebo-controlled, meaning some patients got a dummy shot1. Together they enrolled 1,838 adults at centers in 29 countries1: 981 in B-Well 1 and 857 in B-Well 2, according to the trial registry56. Everyone was already on stable antiviral pills1.
Patients were assigned two to one to the drug or placebo for 24 weeks while staying on their pills. Those whose blood tests met set criteria could stop their pills at week 481. The main results:
- 24% of people on the drug (295 of 1,220) qualified to stop their antiviral pills, compared with none on placebo1.
- At week 72, 19% (233 of 1,220) reached functional cure, compared with none of the 614 people on placebo1.
- Rates were similar in each trial: 20% in B-Well 1 and 19% in B-Well 21.
- People who started with lower levels of the viral surface protein (HBsAg, 1,000 IU/mL or less) did better: 25% and 28% in the two trials, compared with 10% and 5% in those with higher levels1. Pooled, that lower-level group reached 26% (200 of 768), against none of 393 on placebo3.
For comparison, GSK says current pills alone typically produce a functional cure in fewer than 1% of patients after a year of treatment4. AJMC described the existing rate as about 1% of patients per year2.
How long it lasts
The approved label includes follow-up to week 96. Of the 233 people with a functional cure at week 72, 91% (211) still had it at week 96, which works out to 48 weeks without any hepatitis B therapy1. Among 84 people who stopped their pills but did not reach or keep a functional cure through week 96, one met the trial’s rules for restarting antivirals and three more restarted without meeting them1.
Who can get it
The approval is narrow. It covers adults without cirrhosis who have taken antiviral pills for at least six months, whose virus DNA is suppressed, and whose HBsAg level is 3,000 IU/mL or lower on an FDA-authorized test34. Alongside the approval, the FDA authorized a Roche blood test as a companion diagnostic to help find eligible patients and track treatment1.
That makes a measured antigen test a gate to treatment. Tatyana Kushner of Weill Cornell Medicine told GI & Hepatology News in July that this kind of quantitative test had not usually been done for most patients but would likely matter for finding those most likely to benefit1.
The drug is given as injections under the skin, twice a week for the first two weeks and then once a week through week 243. The first dose is given under a health professional’s supervision; patients or caregivers can give later doses after training1. Patients stay on their antiviral pills during the course and for at least 24 weeks afterward, and stopping them is then considered only if blood tests meet set criteria1. People who also take these pills for HIV must not stop them unless their HIV provider says so, the label states1.
What it does not show yet
Roughly four in five treated people in the trials did not reach a functional cure1. And the trial investigators said longer follow-up is still needed to know whether responses hold over several years1.
Safety is a real trade-off. The label carries a boxed warning, the FDA’s strongest, for liver flares during treatment and for thrombocytopenia, a drop in blood platelets3. According to coverage by Superpower, the flares are sharp rises in a liver enzyme, usually within the first 12 weeks, and the drug should not be used in people whose platelet counts are already low or who have cirrhosis7. Other warnings include worsening kidney function, serious inflammatory and immune reactions, and hepatitis flare-ups after stopping antiviral therapy3. The most common side effects were injection-site reactions, fever, tiredness and headache3. People who stop their pills need to be watched for at least a year for severe flares, Superpower reported7.
How it got here
Earlier, in a mid-stage trial called B-Clear with 457 participants, a 24-week course left 9-10% of people with the virus undetectable for 24 weeks after the drug stopped8. That trial also found people with low starting antigen levels were most likely to benefit, which shaped who was enrolled later8. The FDA granted the drug Fast Track status in February 20249, and in April 2026 accepted it for priority review and gave it Breakthrough Therapy designation, both meant to speed up promising drugs2.
Who is behind it
GSK sponsored both late-stage trials56. The drug was discovered by Ionis Pharmaceuticals and licensed to GSK in August 20199. Much of the enthusiasm comes from the companies: GSK calls the cure rates “unprecedented”4, and GSK chief scientific officer Tony Wood said patients “have the potential to achieve functional cure after a six-month treatment course”4. GSK’s announcement also quoted Norah Terrault of USC’s Keck medical center calling it “the start of a new era in treating people living with CHB”4. The sources do not say whether outside experts quoted in company materials have ties to GSK.
How it fits the field
Chronic hepatitis B can lead to cirrhosis and liver cancer, which together cause almost a million deaths a year, according to GSK9. Estimates of how many Americans have it differ by source. GSK put it at about 1.7 million4; AJMC, citing the CDC, said about 640,000 US adults2; and Ionis CEO Brett Monia said over one million2. Worldwide, GSK has cited nearly 300 million people9.
GSK says it is also studying the drug as a base for future combination or step-by-step regimens to reach a wider group of patients9.
