The FDA approved GSK and Ionis’s bepirovirsen for a narrow group of adults with chronic hepatitis B; 19% of treated trial patients still had the virus controlled, with hepatitis B surface antigen undetectable, 24 weeks after stopping all therapy. Price, monitoring burden and ex-US filings now decide its reach.
PHARMA REGULATION · HEPATOLOGY · OCTOBER 22, 2026 · UNITED STATES
The FDA on October 20th approved Hibsago (bepirovirsen), a GSK injection licensed from Ionis Pharmaceuticals, for a defined group of adults with chronic hepatitis B. It is the first antisense oligonucleotide (ASO) the FDA has approved for the disease, and it may let some patients keep the virus controlled after stopping all hepatitis B therapy.
The label is narrow. Hibsago is indicated, alongside nucleos(t)ide analog reverse transcriptase inhibitor (NrtI) therapy, for adults without cirrhosis who have taken NrtI therapy for at least six months, have suppressed hepatitis B virus (HBV) DNA and have hepatitis B surface antigen (HBsAg) levels of 3,000 IU/mL or less on an FDA-authorized test. Alongside the approval, the FDA authorized Roche’s Elecsys HBsAg II quant II RxDx assay as a companion diagnostic, used to help select patients for treatment and to monitor them during it. Patients receive subcutaneous injections for up to 24 weeks, then stay on their existing antiviral for at least 24 more weeks; only those meeting health and laboratory criteria may then stop. GSK says patients have the option of self-administering after the first dose. The FDA granted Fast Track, Breakthrough Therapy and Priority Review.
What the trials showed
Approval rests on two placebo-controlled phase III trials, B-Well 1 and B-Well 2, which enrolled 1,838 patients at sites that included Argentina, Brazil, Mexico and Panama. According to the FDA, 24% of Hibsago recipients qualified to stop their existing medicine, against none on placebo. Twenty-four weeks after stopping all treatment, 19% still had the virus under control and no detectable HBsAg. GSK’s pooled count, in patients with baseline HBsAg of 3,000 IU/mL or less, is 233 of 1,220 versus 0 of 614 on placebo. Among patients starting at 1,000 IU/mL or less, the rate rose to 26% (200 of 768 versus 0 of 393).
19%
of Hibsago recipients (233 of 1,220) had the virus controlled and HBsAg undetectable 24 weeks after stopping all hepatitis B treatment, versus 0 of 614 on placebo: an absolute gain of about 19 percentage points.
GSK calls this endpoint “functional cure”: undetectable HBV DNA and HBsAg for at least 24 weeks off all treatment. Roughly four in five treated patients did not reach it. The company says standard care alone typically achieves less than 1% after a year. The comparison matters because, as WHO notes, current HBV antivirals “are not curative and need to be taken for life”.
The commercial test: monitoring and price
Hibsago carries a boxed warning for serious liver reactions (on-treatment hepatic flares) and low platelet counts, which can raise the risk of potentially life-threatening bleeding, plus warnings for worsening kidney function, serious inflammatory reactions such as vasculitis, and risks from improper injection. GSK’s safety information calls for monitoring platelet counts at least weekly during treatment. Jefferies analysts have flagged that monitoring burden as a brake on uptake outside specialty centers, while keeping a peak-sales estimate of £2.2bn (about $2.95bn). BMO Capital Markets is more cautious, projecting risk-unadjusted peak sales of $659m.
GSK has not disclosed a US list price; it has said the price will be disclosed once pricing and reimbursement discussions with payers are complete, and that it expects the drug to be available to US patients before year-end. The first public price benchmark is Japan, which approved the drug first in August and set a national health insurance price of ¥183,015 per 150 mg syringe. For payers, the comparator is cheap generic suppression: WHO puts the global annual cost of tenofovir-based treatment at about $34–300 per person, with the lowest prices for generics. Ionis is eligible for tiered royalties of 10–12% on net sales.
The addressable pool is also contested. GSK cites a modelling study estimating about 1.7m Americans with chronic hepatitis B; the Centers for Disease Control and Prevention (CDC) estimates about 640,000 adults, roughly half of whom may not know they are infected. Only diagnosed, treated, virally suppressed patients without cirrhosis and with low HBsAg qualify.
What to Watch
- The US list price and payer criteria, including whether plans require specialist prescribing or the companion HBsAg test before approving coverage.
- Durability: whether functional responders stay off therapy beyond 24 weeks, given the label’s call for continued monitoring, including kidney function for at least a year, after NrtI therapy stops.
- Ex-US decisions: GSK expects “key regulatory decisions” in the coming months, with reviews under way in China and Europe; it has not disclosed Latin American filings.
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For Latin America the stakes are real but distant. WHO’s 2026 global hepatitis report estimates 5.0m people with chronic HBV across the Region of the Americas (a 0.5% prevalence), a region that also includes the US and Canada; only about 23% of them had been diagnosed by the end of 2024. Local investigators already have trial experience with the drug. Whether public systems used to cheap generic suppression will pay for a six-month course that produced a functional cure in about one trial patient in five is the question GSK will have to answer market by market.
Why this is relevant
Patients
A minority of eligible adults may be able to stop lifelong antivirals, in exchange for at least weekly platelet checks and boxed-warning risks during treatment.
Industry
The first ASO approval in hepatitis B returns Ionis’s RNA-targeted platform to infectious disease, where its first product, fomivirsen, was approved in 1998 for a viral eye infection, and gives developers of finite-duration hepatitis B regimens an FDA precedent built on sustained off-treatment viral control with HBsAg loss, the endpoint GSK calls functional cure.
Payers
A finite 24-week course with an undisclosed price must be weighed against low-cost generic suppression and an intensive monitoring bill.
Regulators
The FDA tied use to an authorized quantitative HBsAg test, making test access part of the launch, not an afterthought.
Sources: FDA: FDA Approves First-of-Its-Kind Chronic Hepatitis B Treatment · GSK: Hibsago (bepirovirsen) approved in the US for the treatment of chronic hepatitis B (CHB) · GSK: Hibsago (bepirovirsen) approved in Japan · Ionis: Ionis partner GSK announces Hibsago approved in the U.S. · ClinicalTrials.gov: B-Well 1 (NCT05630807) · ClinicalTrials.gov: B-Well 2 (NCT05630820) · BioPharma Dive: GSK, Ionis win US approval for first-of-its-kind hepatitis B drug · Fierce Pharma: GSK brings promise of ‘functional cure’ to hepatitis B finish line · BioSpace: GSK, Ionis win FDA nod for hepatitis B functional cure · Healthle: Hibsago NHI price (Japan) · Pink Sheet: Japan Grants Global-First Price To GSK’s Novel HBV Drug Bepirovirsen · WHO: Global hepatitis report 2026 · CDC: Hepatitis B Basics
THE HEALTHSIGNALS BRIEF
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