The First Functional Cure for Hepatitis B Clears One Patient in Five
Bepirovirsen is the first therapy to offer people with chronic hepatitis B a shot at functional cure after a six-month course. It works in about one in five, and only in a narrow, already-treated population.
On October 20, 2026, the Food and Drug Administration approved Hibsago (bepirovirsen), used with existing antiviral therapy, for chronic hepatitis B in certain adults without cirrhosis. It is the first antisense oligonucleotide cleared for the infection, and the first therapy approved for chronic hepatitis B on the strength of a functional-cure endpoint rather than lifelong viral suppression. In two replicate Phase 3 trials, about one patient in five met the bar. Placebo produced zero cures. The label is written for an already-treated, low-antigen slice of a disease that still kills more than a million people a year.
A 19% cure, measured off all treatment
Functional cure here is a strict endpoint: HBV DNA below the lower limit of quantification plus loss of hepatitis B surface antigen (HBsAg), held for at least 24 weeks after every treatment stops. Investigators read it at week 72, six months after patients discontinued nucleoside/nucleotide analogue (NA) therapy at week 48.
In B-Well 1, 127 of 650 patients on bepirovirsen (20%) met it, against 0 of 328 on placebo. In B-Well 2, 106 of 570 (19%) versus 0 of 286. Pooled, 233 of 1,220 (19%) versus 0 of 614. Those results in the New England Journal of Medicine are why the approval is historic and why it is not a population solution. GSK cites standard-of-care functional cure rates under 1% after a year of NA therapy. A jump from that floor to 19% matters, with 81% still leaving uncured.
The effect clustered where antigen was already low. In patients with HBsAg of 1,000 IU/mL or less, functional cure was 200 of 768 (26%) versus 0 of 393 placebo. GSK says that subgroup is about 45% of diagnosed chronic HBV cases globally. Exploratory data showed HBsAg of 100 IU/mL or less by week 72 in 49% of the overall population (598 of 1,220) and 62% of the 1,000-or-less group (476 of 768). Antigen knockdown is not the registrational endpoint. Turning that drop into a durable off-treatment cure still fails more often than it succeeds.
Eligibility does most of the work
The indication is a filter. Adults must be without cirrhosis, on NA therapy for at least six months, with suppressed HBV DNA and HBsAg of 3,000 IU/mL or less by an FDA-authorized test. A companion diagnostic, Roche's Elecsys HBsAg II quant II RxDx, was authorized to select and monitor patients. Chronic hepatitis B affects about 1.7 million people in the United States and more than 240 million worldwide, causes roughly 1.1 million deaths a year, and is the leading cause of liver cancer globally (about 56% of cases, per the Hepatitis B Foundation as quoted in GSK's release). Many patients need lifelong antivirals. Most of that population will not meet this label on day one.
Dosing is 300 mg subcutaneously once a week for 24 weeks, with existing NA therapy continued for at least 24 weeks after the last injection. Some patients may then stop that medicine if they meet lab criteria. All but the first dose can be self-administered. Treatment is finite, which is the point. The calendar is still 24 weekly shots, another half year of antivirals, and an off-treatment watch.
The boxed warning is not boilerplate
The FDA boxed warning covers serious liver reactions and low platelet counts, which can cause life-threatening bleeding. Warnings also cover worsening kidney function, inflammatory reactions such as vasculitis, and risks with improper injection. Patients need regular blood tests, including weekly or bi-weekly checks of liver enzymes and platelets.
In the pooled NEJM analysis, adverse events occurred in 91% of bepirovirsen patients versus 73% on placebo. Serious events were 7% versus 4%. Grade 3 or higher events were 16% versus 3%. ALT increases were the most common grade-3 event (6%). Excluding lab abnormalities, the most common side effects were injection site reactions, fever, fatigue, and headache. Cirrhosis is outside the indication. The patients with more advanced liver disease are not the patients this approval covers.
A GSK franchise without a list price
Bepirovirsen was licensed from and co-developed with Ionis Pharmaceuticals; approval was granted to GSK plc. The FDA had already assigned Fast Track and Breakthrough Therapy designations along with Priority Review. The drug was approved in Japan in August 2026 and remains under review in China and Europe.
GSK has not disclosed a U.S. list price; it will be disclosed after payer discussions. Jefferies, as reported by BioPharma Dive, has estimated around $3 billion in peak annual sales. The approval supports GSK's goal of 40 billion pounds in annual revenue by 2031 as it offsets patent expirations. Those estimates now sit next to a 19% cure rate, a diagnostic gate, and a boxed warning. How small the cured fraction is, how selected the eligible pool is, and how much monitoring a chance to stop therapy requires will decide whether this landmark becomes a franchise.