The US Food and Drug Administration approved Hibsago (bepirovirsen) on October 20, 2026 for certain adults with chronic hepatitis B1. It is given together with standard antiviral pills and is the first antisense oligonucleotide approved in the US to treat the infection1. The drug is made by GSK, which licensed it from Ionis Pharmaceuticals27.
What sets the drug apart is its goal. Current hepatitis B pills suppress the virus but are usually taken for years. Bepirovirsen is a fixed course meant to get some patients to a "functional cure", a state in which virus markers stay undetectable after all treatment stops15.
What happened
The FDA approved Hibsago for adults without cirrhosis who have taken hepatitis B antiviral therapy for at least six months, have suppressed virus levels in the blood, and have hepatitis B surface antigen (HBsAg) levels of 3,000 IU/mL or less1. The agency gave the application Fast Track, Breakthrough Therapy and Priority Review designations1.
The US decision follows Japan, where the Ministry of Health, Labour and Welfare approved bepirovirsen in August 2026, the drug's first approval anywhere8. GSK says reviews in other regions are ongoing. In China, where the regulator began its review in March, the drug holds Breakthrough designation and Priority Review, and in Japan it had received SENKU designation28.
"Hibsago provides a new treatment approach that gives some patients the possibility of maintaining control of the virus after all chronic HBV treatment has ended." Wendy Carter, DO, FDA Office of Infectious Diseases1
The evidence so far
The approval is based on two replicate phase 3 trials, B-Well 1 and B-Well 2, published in the New England Journal of Medicine and presented at the EASL Congress in 202634. The trials randomly assigned 1,838 adults with chronic hepatitis B without cirrhosis, all already on nucleoside or nucleotide analogue pills, to bepirovirsen or placebo in a 2:1 ratio34. They were double-blind and ran in 29 countries across Europe, the Asia-Pacific region and the Americas, with recruitment from December 2022 to May 202537. Bepirovirsen was given as weekly injections under the skin for 24 weeks3.
The main outcome was functional cure at week 72, defined as undetectable HBsAg and HBV DNA below the level that can be measured, sustained for at least 24 weeks after all treatment ended35.
| Group (baseline HBsAg) | Bepirovirsen | Placebo |
|---|---|---|
| B-Well 1 (3,000 IU/mL or less) | 20% (127 of 650) | 0% (0 of 328) |
| B-Well 2 (3,000 IU/mL or less) | 19% (106 of 570) | 0% (0 of 286) |
| Pooled (3,000 IU/mL or less) | 19% (233 of 1,220) | 0% (0 of 614) |
| Pooled (1,000 IU/mL or less) | 26% (200 of 768) | 0% |
The FDA also reported that 24% of people given Hibsago met the trial requirements to stop their existing antiviral medicine, compared with none on placebo1. According to GSK, 49% of treated participants reached HBsAg levels of 100 IU/mL or lower27.
For comparison, GSK says standard antiviral pills alone typically achieve functional cure in about 1% of patients after a year of treatment8. The trial's lead author explained why the field targets surface antigen loss rather than viral suppression alone:
"HBsAg loss is associated with better clinical outcomes than HBV DNA suppression alone, but it is rarely achieved with currently approved therapies." Jinlin Hou, lead author4
Safety and warnings
Side effects were more common with the drug. In the trials, 91% of bepirovirsen recipients had an adverse event, compared with 73% on placebo; serious adverse events occurred in 7% versus 4%, and grade 3 or higher events in 16% versus 3%45. The most common severe event was a rise in the liver enzyme ALT, and 24% of treated participants had ALT flares of at least three times the upper limit of normal34.
The label carries a boxed warning for serious liver reactions and for low platelet counts with a risk of bleeding1. The FDA also lists warnings for worsening kidney function and serious inflammatory reactions including vasculitis, and says patients need regular blood tests before and during treatment1. According to trade coverage of the label, the drug should not be used in people whose platelet counts are below 100 x 109/L, and platelets are monitored weekly6. Common side effects include injection-site reactions, fever, fatigue and headache1.
What it does not show yet
- Most patients did not reach functional cure. About four in five eligible trial participants did not meet the functional cure definition at week 723.
- Durability is open. In an NEJM editorial, Anna Lok of the University of Michigan noted that longer follow-up is needed to know whether the effect lasts3.
- Many patients are outside the label. People with cirrhosis or HBsAg above 3,000 IU/mL were not covered, and Lok wrote that other therapies are needed for them13.
- Hard outcomes were not measured. The trials tracked blood markers. GSK cites data linking loss of HBsAg to an 89% lower risk of liver cancer and 62% lower all-cause mortality8, but those figures do not come from the B-Well trials.
- Who was studied. Participants were mostly Asian men, with average ages around 49 to 50 years4.
"The B-Well trials represent a major step toward a functional cure for HBV infection, and bepirovirsen is an attractive option for selected patients." Anna Lok, MD, University of Michigan3
Who is behind it
GSK sponsored the application and holds the approval1. It licensed bepirovirsen from Ionis Pharmaceuticals and developed it with Ionis27. GSK has not disclosed a US price5. The analytics firm GlobalData projects sales of $926 million in 20347. The lead author of the NEJM paper was Jinlin Hou4. Claims about "unprecedented" cure rates appear in GSK's own release2 and are the company's wording.
What to watch next
Chronic hepatitis B affects about 1.7 million people in the US and more than 240 million worldwide, according to GSK, which links it to about 1.1 million deaths a year2. Points to follow:
