The US Food and Drug Administration approved GSK's Hibsago (bepirovirsen) on 20 October 2026 for certain adults with chronic hepatitis B. It is given for six months alongside standard antiviral tablets. In two Phase III trials, 19% of treated patients had no detectable virus or surface antigen six months after stopping all treatment.
GSK describes that result as a "functional cure". Bepirovirsen is an antisense oligonucleotide, a short strand of genetic material designed to block the virus's RNA. Japan approved it in August 2026, making the US the second country to do so. In Europe, the medicine is still under review by the European Medicines Agency (EMA), and it is not yet available to patients in Ireland.
- Approval: FDA approval of Hibsago (bepirovirsen) on 20 October 2026, under priority review and Breakthrough Therapy Designation.
- Who it is for: adults without cirrhosis who have taken nucleos(t)ide analogue antivirals for at least six months, have suppressed HBV DNA and have surface antigen (HBsAg) of 3,000 IU/mL or lower.
- Main result: 233 of 1,220 bepirovirsen patients (19%) met the primary endpoint, against 0 of 614 on placebo.
- Safety: the US label carries a boxed warning for liver enzyme flares during treatment and for low platelet counts.
- Europe and Ireland: EMA review under way since March 2026; no EU decision and no Irish reimbursement process yet.
1. What the FDA approved
The FDA lists Hibsago as its 47th novel drug approval of 2026. According to the US prescribing information, it must be used together with existing nucleos(t)ide analogue therapy. Patients need an HBsAg level of 3,000 IU/mL or lower, measured with an FDA-authorised test, before starting.
Treatment is a course of injections under the skin. Each dose is 300 mg, given as two 150 mg injections. Doses are twice a week in weeks 1 and 2, then once a week from week 3 to week 24. GSK says patients can choose to inject themselves after the first dose. The company has not disclosed a US list price in its announcement.
2. What the B-Well trials showed
The approval rests on two identical Phase III trials, B-Well 1 and B-Well 2. They randomised 1,838 adults in 29 countries, who were assigned two to one to bepirovirsen or placebo on top of their usual antivirals. After 24 weeks, the injections stopped. Patients who met set criteria at week 48 then also stopped their antiviral tablets.
The primary endpoint was measured at week 72. It required HBV DNA below the level of quantification and HBsAg not detected, 24 weeks after stopping all hepatitis B treatment, with no rescue medication. The table shows the results from the label.
| Group | Bepirovirsen | Placebo |
|---|---|---|
| B-Well 1, HBsAg 3,000 IU/mL or lower | 127 of 650 (20%) | 0 of 328 |
| B-Well 2, HBsAg 3,000 IU/mL or lower | 106 of 570 (19%) | 0 of 286 |
| Pooled, HBsAg 1,000 IU/mL or lower | 200 of 768 (26%) | 0 of 393 |
Response was lower in people with higher starting HBsAg, those who were HBeAg positive and those aged 65 or over. Durability data are encouraging but limited. Of the 233 responders at week 72, 211 (91%) were still off all hepatitis B treatment with the same result at week 96. The full results were published in the New England Journal of Medicine in 2026.
3. "Functional cure" and the safety warnings
The FDA label does not use the phrase "functional cure". It describes the endpoint in laboratory terms. GSK uses the phrase, defining it as HBV DNA and HBsAg being undetectable for at least 24 weeks after stopping all treatment. GSK says current antivirals alone typically achieve this in less than 1% of patients after a year. Most people on those drugs stay on them for life.
The label carries a boxed warning. Liver enzyme (ALT) flares of more than 20 to 40 times the upper limit of normal can occur during treatment, usually between weeks 5 and 10. Platelet counts can also fall suddenly, which can be life-threatening. Liver tests and platelets must be checked before and during treatment. The most common side effects were injection site reactions, fever, tiredness and headache. In the pooled trials, 3% of patients on bepirovirsen stopped because of adverse events, compared with less than 1% on placebo. Anyone with questions about their own hepatitis B treatment should speak to their doctor.
4. The Irish and European angle
GSK filed for EU approval earlier this year. The EMA accepted the application for review on 27 March 2026. No opinion from the EMA's medicines committee (CHMP) had been published by 2 November 2026, and bepirovirsen was not among the new medicines recommended at the committee's 12 to 15 October meeting. GSK says it expects "key regulatory decisions" in several regions in the coming months, without naming dates.
For patients in Ireland, the route is EU marketing authorisation first. The company would then apply to the HSE for reimbursement, which involves an assessment by the National Centre for Pharmacoeconomics (NCPE). A search of the NCPE website on 2 November 2026 returned no entry for bepirovirsen, so that process has not publicly started. Neither B-Well trial listed a site in Ireland on ClinicalTrials.gov, although both had sites in the UK, France, Germany, Spain and Italy.
The Health Protection Surveillance Centre recorded 572 hepatitis B notifications in Ireland in 2025, a provisional figure equal to 11 per 100,000 people. Of these, 544 were chronic cases. HPSC notes that notifications do not measure how many people are living with the infection.
GSK has three sites in Ireland, according to the company. Its headquarters at Citywest, Dublin, runs the commercial business. An office at Cork Airport Business Park houses global support staff for R&D, pharma and vaccines. A laboratory in Carrigtohill, Co Cork, gives analytical support to GSK manufacturing sites. GSK has not said whether any Irish site has a role in bepirovirsen. See our GSK company page and bepirovirsen trials page for more.
Frequently Asked Questions
What does "functional cure" mean for hepatitis B?
It means the virus's DNA and its surface protein, HBsAg, cannot be detected in the blood for at least 24 weeks after all treatment stops. The virus is not removed from the body completely, but the immune system keeps it under control without medicine.
Who is Hibsago approved for in the US?
Adults without cirrhosis who have taken nucleos(t)ide analogue antivirals for at least six months, have suppressed HBV DNA and have HBsAg of 3,000 IU/mL or lower. It is not recommended for people who also have hepatitis D.
Can patients in Ireland get bepirovirsen?
Not yet. It has no EU marketing authorisation, and no HSE reimbursement assessment has started. The EMA review has been running since March 2026.
Outlook
The next milestone for Irish and European patients is a CHMP opinion, followed by a European Commission decision. GSK says it is advancing submissions in other regions too. After any EU approval, the speed of access in Ireland will depend on GSK's pricing submission and the NCPE assessment. Our FDA approvals tracker follows new US decisions as they happen.
Sources
- US Food and Drug Administration, Novel Drug Therapy Approvals for 2026, Hibsago entry dated 20 October 2026
- GSK, Hibsago (bepirovirsen) approved in the US for the treatment of chronic hepatitis B (CHB), 20 October 2026
- GSK, Hibsago US Prescribing Information, revised October 2026
- GSK, Bepirovirsen accepted for review by the European Medicines Agency, 27 March 2026
- European Medicines Agency, Meeting highlights from the CHMP, 12 to 15 October 2026
- Hou J, Lim SG, Buti M, et al., Phase 3 results of bepirovirsen treatment for chronic hepatitis B virus infection, N Engl J Med, 2026
- ClinicalTrials.gov, B-Well 1 (NCT05630807) and B-Well 2 (NCT05630820), accessed 2 November 2026
- HSE Health Protection Surveillance Centre, Epidemiology of hepatitis B in Ireland: trends up to 2025, June 2026
- GSK, GSK in Ireland, accessed 2 November 2026
- National Centre for Pharmacoeconomics, ncpe.ie, searched 2 November 2026
Cover image: AI-generated illustration of the Hibsago carton and prefilled syringe. It is not a photograph of the real product or its packaging.
