FDA approves Hibsago, first antisense drug for hepatitis B
The FDA approved GSK's Hibsago (bepirovirsen) on 20 October 2026 as an add-on for chronic hepatitis B; about 19% reached functional cure in trials.
The US Food and Drug Administration (FDA) approved GSK's Hibsago (bepirovirsen) on 20 October 2026 for chronic hepatitis B, a long-term liver infection. It is the first antisense oligonucleotide approved for the disease, according to Pharmacy Times, and in GSK's trials about one in five patients kept the virus controlled after stopping treatment. The label also carries the FDA's strongest warning, so the benefit comes with real risks.
What the FDA approved
Hibsago is an add-on to existing antiviral tablets, not a replacement. It is approved for adults without cirrhosis, the scarring of the liver, who have taken those antivirals for at least six months, have suppressed virus in the blood and have a surface antigen level (HBsAg, a blood marker of the virus) of 3,000 IU/ml or below. Pharmacy Times says the FDA also approved a Roche blood test as the companion diagnostic to pick and monitor patients. Treatment is a six-month course of weekly injections, and GSK says patients can self-inject after the first dose. In the trials the dose was 300 mg once a week for 24 weeks, and patients stopped their tablets at week 48. The FDA acted ahead of its 26 October target date, which BiopharmaWatch had listed.
How an antisense drug works
An antisense oligonucleotide is a short strand of genetic material designed to latch onto the instructions a virus uses to make a protein and stop them being read, a bit like cutting the pages out of a recipe so the dish cannot be made. Current tablets suppress the virus but rarely clear it, so most patients stay on them for life. GSK licensed bepirovirsen from Ionis Pharmaceuticals.
What the trials found
The figures come from two phase 3 trials, B-Well 1 and B-Well 2, which GSK funded. Both were double-blind, meaning neither patients nor doctors knew who got the drug, and patients were assigned two to one to bepirovirsen or placebo. "Functional cure" means surface antigen is lost and virus stays undetectable for at least 24 weeks after treatment ends. Pooled, 19% of Hibsago patients (233 of 1,220) reached it at week 72, against none of 614 on placebo. GSK says standard care alone usually manages under 1% after a year. Among patients with antigen at or below 1,000 IU/ml, 26% (200 of 768) reached it. These results cover 72 weeks, so lasting benefit is not yet known.
The safety warning
Pharmacy Times says the label has a boxed warning, the FDA's strongest, for serious liver reactions and low platelet counts that can cause life-threatening bleeding, and that regular blood tests are required before and during treatment. In pooled 72-week data, grade 3 or higher events occurred in 16% of Hibsago patients and 3% of placebo patients, and serious adverse events in 7% and 4%. The most common serious lab finding was raised liver enzymes, in 6%. GSK's release calls the safety profile acceptable and names injection-site redness, pain and a temporary rise in a liver enzyme as the most frequent events. It does not mention the boxed warning.
What it means for readers
GSK says chronic hepatitis B affects more than 240 million people worldwide and is the leading cause of liver cancer. A therapy that lets some patients stop treatment is therefore closely watched. This approval covers the US only. GSK says decisions in other regions are expected in the coming months, and it has been approved in Japan. We found no report of an Indian decision, and price and availability were not stated. Families should not change any treatment on this news. Eligibility depends on blood tests and liver health, and this is not medical advice.
What to watch next
Watch for GSK's regional decisions, which it expects in the coming months, and for any Indian regulatory filing. Longer follow-up on how long the cure lasts will also matter.
Key takeaways
- The FDA approved Hibsago on 20 October 2026 as the first antisense drug for chronic hepatitis B, for use alongside existing antivirals.
- In GSK-funded phase 3 trials, 19% of patients reached functional cure against none on placebo.
- The label carries a boxed warning for serious liver reactions and low platelet counts, and regular blood tests are required.
- No Indian decision has been reported, and the approval does not change treatment for patients elsewhere yet.
Sources
- [GSK: Hibsago (bepirovirsen) approved in the US for chronic hepatitis B](https://www.gsk.com/en-gb/media/press-releases/hibsago-bepirovirsen-approved-in-the-us-for-the-treatment-of-chronic-hepatitis-b-chb/)
- [Pharmacy Times: FDA approves bepirovirsen, first ASO for chronic hepatitis B](https://www.pharmacytimes.com/view/fda-approves-bepirovirsen-first-aso-for-chronic-hepatitis-b)
- [BiopharmaWatch: FDA calendar October 2026](https://www.biopharmawatch.com/blog/fda-calendar-october-2026)
Tags: Hepatitis B FDA GSK Antisense drugs Drug approval