Six years before the US, the European Medicines Agency (EMA) approved bulevirtide for the treatment of chronic hepatitis delta infections. On May 22, 2026, the FDA followed suit: with the approval of Hepcludex (manufacturer Gilead Sciences), there is now for the first time an FDA-approved therapy in the United States for the approximately 12 million people worldwide who are chronically infected with hepatitis delta virus (HDV).
What is hepatitis delta?
Hepatitis delta virus is a satellite virus: it can only replicate when the host is simultaneously infected with hepatitis B virus (HBV). HDV requires HBV's envelope proteins for its own replication. This limits the disease's epidemiology but makes it biologically more dangerous: simultaneous infection with HBV and HDV leads to more severe liver disease than HBV alone, with higher rates of liver cirrhosis and liver failure. Worldwide, approximately 12 million people are chronically coinfected with HDV and HBV, with particularly high burden in the Mediterranean region (especially Italy and Albania), Eastern Europe, and parts of Africa and Asia.
Until May 22, 2026, there was no approved therapy in the US. Patients were treated with interferon, which carries severe side effects and only works in some patients, or with supportive care. The situation was different in Europe.
Europe already had the therapy in 2020
The EMA granted Hepcludex conditional marketing approval for the EU on July 31, 2020, as the first therapy ever for chronic HDV infection. This was a conditional approval, which allows faster access to therapies addressing unmet medical need. In July 2023, this converted to a full, standard approval. European patients, if insured and living in countries with appropriate reimbursement policies, have had access to the therapy for six years.
Why did it take so long in the US? The FDA required data from the open-label Phase 3 trial MYR301 with a delayed treatment arm, running for over 144 weeks. The US review process followed a different timeline than the European one. Accelerated Approval is based on a surrogate endpoint: reduction in HDV viral load and normalization of the liver enzyme alanine aminotransferase (ALT), not on direct survival or remission data. A confirmatory study is still ongoing.
How bulevirtide works
Bulevirtide is an entry inhibitor, the first drug class of its kind for hepatitis. Gilead's drug blocks NTCP (sodium taurocholic cotransporter), a bile acid transport protein on liver cell surfaces. Both HBV and HDV use this protein to enter liver cells. Blocking entry prevents new cells from becoming infected. Patients inject Hepcludex once daily at 8.5 milligrams subcutaneously. The European approval uses a lower dose of 2 milligrams daily, based on different clinical protocols.
In comparison: What hepatitis C shows as a benchmark
Hepatitis C is the reference example for how pharmaceutical innovation can transform a chronic viral infection from incurable to curable within a decade. In 1998, interferon was the only therapy, effective in about 50 percent of patients and with significant side effects. Starting in 2013, direct-acting antivirals arrived on the market (sofosbuvir, ledipasvir, daclatasvir), achieving cure rates above 95 percent with good tolerability. The breakthrough took roughly ten years from first clinical signals to clinical routine. However, Gilead's price for sofosbuvir (Sovaldi) in the US at 84,000 dollars for a twelve-week course sparked public outrage and political pressure on the company. For hepatitis delta, access and price questions arise earlier than they did for hepatitis C.
Who is critically monitoring access
Gilead Sciences has conducted price negotiations with individual European countries following EMA approval of Hepcludex. The European AIDS Treatment Group (EATG), which monitors access to antiviral therapies for marginalized populations, hailed the FDA approval as progress but pointed out the problem of cost reimbursement in endemic regions: HDV disproportionately affects countries with low to middle per-capita income, where a patent-protected drug is difficult to access. The Hepatitis B Foundation, representing patient interests, has noted that many HDV patients go undiagnosed because physicians do not routinely test for HDV among patients with known hepatitis B. Without diagnosis, an approved therapy reaches no one.
Three conditions before bulevirtide reaches those affected
FDA approval is necessary but not sufficient. First, accelerated approval must be supported by a confirmatory study with clinical endpoints (liver cirrhosis, liver failure, survival). The MYR301 study is still ongoing, with results expected by 2027 at the earliest. Second, systematic HDV screening is needed: the WHO recommends testing all chronically HBV-infected individuals for HDV, which is not routine practice in many countries. The gap between incidence figures (roughly 12 million known cases) and actual diagnosis is substantial. Third, access in endemic regions of Africa and Asia, where financial capacity for expensive antivirals is limited, remains unsolved. The history of hepatitis C shows that accelerated approval and high efficacy alone do not resolve global health questions.