The first US hepatitis D drug comes with a boxed warning and an 8-year wait for proof

The FDA approved Hepcludex (bulevirtide-gmod) on 22 May for chronic hepatitis delta virus infection in adults without cirrhosis or with compensated cirrhosis — the first time the agency has approved any drug specifically for the condition [s1] [s2]. The approval letter lists an "Initial U.S. Approval" year of 2026 on the drug's own label [s2].

It arrives with two qualifications that shape what the approval actually means for patients: it rests on a surrogate marker rather than a proven reduction in liver disease, and FDA turned down the company's request for a reward that regulatory approvals of this kind often carry.

What the approval is based on

Hepcludex was cleared under FDA's accelerated approval pathway, based on participants achieving a decline in hepatitis D virus (HDV) RNA and normalization of alanine aminotransferase (ALT), a liver enzyme — not on a demonstrated reduction in cirrhosis, liver failure, liver cancer or death [s2]. The label states plainly: "An improvement in disease-related clinical outcomes has not been established. Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s)" [s2].

That confirmatory trial is not a new study Gilead has yet to design — it is a postmarketing requirement FDA attached directly to the approval. The company must complete an observational study comparing liver-related outcomes — cirrhosis, hepatic decompensation, liver transplantation, liver cancer and liver-related death — in Hepcludex-treated patients against a historical control group who received standard care without it, with up to five years of follow-up [s1]. Per the timetable Gilead submitted to FDA, the study is not due to complete until February 2033, with a final report due June 2034 — eight years after the drug reaches patients [s1].

The efficacy data behind the surrogate marker

The approval draws on Trial MYR301, a Phase 3, randomized, open-label study of 100 participants with chronic HDV infection, comparing immediate treatment with a 48-week delayed-treatment control arm [s2]. At Week 48, the primary endpoint — a "combined response" of virologic decline plus ALT normalization — was met by 48% of the Hepcludex group versus 2% of the delayed-treatment group, a 46-percentage-point difference (96% CI: 31% to 61%; p<0.0001) [s2]. Undetectable HDV RNA was reached by 20% of the Hepcludex group at Week 48, rising to 36% at Week 96 and 50% at Week 144 among those on continuous treatment [s2]. Response varied by hepatitis B genotype: among the HBV genotype-D participants who made up 86% of the trial population, 87% showed a virologic response by the relevant measure, versus 50% of the smaller genotype-A subgroup [s2].

Treatment is a self-administered daily subcutaneous injection of 8.5 mg, and the label states the optimal duration is unknown — meaning Hepcludex is intended to continue indefinitely as long as it appears to be working, not as a fixed course [s2].

The boxed warning

Hepcludex carries a boxed warning — FDA's strongest label alert — for severe acute exacerbations of both hepatitis D and hepatitis B that can occur after the drug is stopped, particularly in patients with cirrhosis, who face increased risk of more severe flares or progression to liver decompensation [s2]. The label instructs clinicians to monitor liver function, including HBV DNA and HDV RNA levels, for at least six months after discontinuation, and notes that resuming antiviral therapy may be necessary [s2]. Common adverse reactions in the pivotal trial, each occurring in at least 10% of Hepcludex recipients, were injection site reactions, headache, abdominal pain, fatigue and itching [s2].

The voucher FDA declined to grant

Gilead had requested a tropical disease priority review voucher for the application — a separate incentive FDA can award for treatments of certain neglected diseases, which manufacturers can later redeem to speed review of a different drug or sell to another company. FDA's approval letter denies that request outright: hepatitis D virus infection "has not been designated as a tropical disease under section 524(a)(3) of the FD&C Act," the agency wrote, citing its own separate Federal Register notice, published the same day, declining to add hepatitis delta virus disease to the tropical disease list [s1].

FDA also determined that Hepcludex's application did not need to go before an outside advisory committee, stating there were "no controversial issues that would have benefited from advisory committee discussion" [s1]. And because the drug carries orphan drug designation, Gilead is exempt from the usual requirement to study the drug in children as a condition of approval [s1].

Why the surrogate-marker structure matters

Accelerated approval exists precisely for situations like this one: a serious disease with no approved treatment, a plausible biological marker of benefit, and a company willing to commit to further study after the drug is already on the market. Hepatitis D is considered the most severe form of viral hepatitis, and until this approval, U.S. patients with the condition had no FDA-approved drug option at all [s2].

The tradeoff is that "approved" and "proven to help patients live longer or avoid liver failure" are not, at this point, the same claim. FDA's own label draws that line explicitly. Whether Hepcludex earns a full, traditional approval — or has that approval reconsidered — will not be settled by evidence in hand this year. It depends on a five-year observational study that, on the timeline Gilead has proposed to FDA, will not produce a final report until the middle of the next decade [s1].

What to watch

Whether Gilead's 180-day progress reports on the confirmatory study, due to FDA starting six months after approval, show enrollment proceeding on schedule. Whether real-world use outside the trial population — which was 82% White, with a mean age of 41 and no participants over 65 studied for pharmacokinetics — surfaces safety or efficacy signals the pivotal trial's demographics did not capture [s2]. And whether other manufacturers pursuing hepatitis D treatments now have a regulatory template, including the tropical-disease-designation question FDA closed off in this decision, that shapes how they structure their own applications.

Sources

• [s1] U.S. Food and Drug Administration, Center for Drug Evaluation and Research, approval letter for BLA 761468 (Hepcludex/bulevirtide-gmod), 22 May 2026. https://www.accessdata.fda.gov/drugsatfda_docs/appletter/2026/761468Orig1s000ltr.pdf
• [s2] U.S. Food and Drug Administration / Gilead Sciences, Inc., HEPCLUDEX (bulevirtide-gmod) full prescribing information, revised May 2026. https://www.accessdata.fda.gov/drugsatfda_docs/label/2026/761468Orig1s000lbl.pdf
• [s3] U.S. Food and Drug Administration, "Novel Drug Approvals for 2026." https://www.fda.gov/drugs/novel-drug-approvals-fda/novel-drug-approvals-2026