FDA accelerated approval of Hepcludex significant milestone for US HDV market

FDA Grants Accelerated Approval to Gilead's Hepcludex for HDV

Gilead Sciences has received accelerated approval from the US FDA for Hepcludex (bulevirtide-gmod) for adults with chronic hepatitis delta virus (HDV) without cirrhosis or with compensated cirrhosis. This marks Hepcludex as the first and only approved treatment for HDV patients in the US. The approval, granted in May 2026, follows a prior complete response letter in 2022 regarding manufacturing concerns, despite the drug holding breakthrough therapy and orphan drug designations. The approval was supported by data from the pivotal Phase III MYR301 trial, which demonstrated significant reductions in HDV RNA and normalization of ALT at Week 48.

• Hepcludex's accelerated approval by the FDA in May 2026 establishes it as the first and only treatment for chronic hepatitis delta virus (HDV) in the US. This is a critical development for patients facing a severe and rapidly progressive liver disease with previously no approved therapeutic options, positioning Gilead Sciences as a leading player in the HDV market.
• The approval was primarily based on positive results from the pivotal Phase III MYR301 trial (NCT03852719). In this study, Hepcludex demonstrated a statistically significant improvement at Week 48, meeting its primary endpoint by achieving reductions in HDV RNA and normalization of alanine aminotransferase (ALT) levels in 150 adult patients with chronic HDV.
• Hepcludex previously received conditional marketing authorization from the European Commission in 2020 and is also approved in Australia, Canada, and Israel. Despite an initial complete response letter from the FDA in 2022 due to manufacturing and delivery concerns, the drug's breakthrough therapy and orphan drug designations underscored its potential to address a significant unmet medical need.

Addressing the Critical Unmet Need in Chronic HDV

Current treatment options for chronic HDV remain severely limited, with pegylated interferon-alpha (PegIFNα) representing the only established therapeutic option for the past three decades. This approach is characterized by suboptimal response rates, poor tolerability, and significant limitations that leave most patients without adequate treatment options.

• Low efficacy rates: PegIFNα achieves sustained HDV-RNA clearance in less than 25% of patients, with only 25-40% experiencing HDV RNA suppression after 1-2 years of treatment, representing unsatisfactory therapeutic outcomes for the majority of patients

• Poor tolerability and safety profile: PegIFNα treatment is associated with significant side effects and poor tolerability, limiting its clinical utility and patient adherence to therapy

• High relapse rates: Late HDV RNA relapses have been documented during long-term follow-up with PegIFNα treatment, undermining the durability of any initial therapeutic response

• Lack of targeted antiviral agents: The absence of approved drugs that interfere with specific steps of HDV replication creates barriers to understanding viral molecular biology and developing novel targeted medications

• Inability to achieve functional cure: Current strategies fail to achieve HBsAg loss, which most closely resembles HDV cure, leaving patients without the possibility of achieving sustained viral clearance

• Diagnostic challenges: Limited access to standardized diagnostic assays, particularly in resource-limited countries, contributes to widespread underdiagnosis and delayed treatment initiation

• Complex co-infection management: Treatment requires concurrent anti-HBV agents to prevent HBV rebounds following removal of viral interference, adding complexity to therapeutic regimens and potential drug interactions

The Pivotal MYR301 Trial: Design and Key Endpoints

Recent clinical trials for chronic hepatitis delta virus (HDV) in patients without cirrhosis or with compensated cirrhosis have employed diverse study designs to evaluate novel therapeutic approaches. The most significant trials include the MYR202 bulevirtide study, peginterferon alfa-2a combination trials, and lonafarnib dose-finding studies, each with distinct primary endpoints focused on virological response.

Hepcludex's Impact on the Evolving HDV Treatment Landscape

The treatment landscape for chronic HDV has been fundamentally transformed since bulevirtide's conditional approval by the European Medicines Agency in 2020, marking the first targeted therapy for this indication. This novel HDV entry inhibitor, administered at 2 mg daily, has demonstrated consistent efficacy across diverse patient populations, including those with compensated cirrhosis and clinically significant portal hypertension. Mathematical modeling studies have revealed that bulevirtide achieves near-complete (~100%) blockade of HDV entry into hepatocytes, targeting two distinct HDV-infected cell populations with fast (median 13 days) and slow (median 44 days) clearance kinetics, where the slow-clearing population represents approximately 1% of total infected cells.

Recent real-world evidence from a multicenter Italian cohort (2023-2024) involving 108 consecutive patients has validated bulevirtide's clinical effectiveness outside controlled trial settings. This study demonstrated virological response in 54.6% of patients at 6 months, with 36 patients achieving undetectable HDV RNA levels. Among responders, significant improvements were observed in hepatic function markers, with ALT levels decreasing from 67.0 U/mL to 31.5 U/mL (p=0.001) and median HDV RNA declining from 29,800 IU/mL to undetectable levels (p<0.001). Notably, treatment response appears consistent across HDV GT1 subgenotypes based on data from 218 participants in the MYR clinical trial program, suggesting broad applicability regardless of viral genotype.

The safety profile of bulevirtide has proven favorable across all studied populations, with adverse events remaining mild and infrequent. In the Italian real-world cohort, only 5.6% of patients experienced pruritus, 1.9% had injection-site reactions, and 0.9% reported flu-like syndrome, with no treatment discontinuations due to adverse events. Even in challenging patient populations with compensated cirrhosis and portal hypertension, 48-week monotherapy was well-tolerated with no decompensating events or hepatocellular carcinoma development, and asymptomatic increases in bile acids. The emergence of a documented functional cure case following three years of monotherapy, with sustained virological and biochemical responses maintained through 72 weeks post-treatment, suggests potential for durable remission in select patients.

A New Era for Hepatitis Delta Treatment in the US

The accelerated approval of Hepcludex (bulevirtide-gmod) by the US FDA represents a landmark achievement in the fight against chronic hepatitis delta virus (HDV). For decades, patients afflicted with this aggressive form of viral hepatitis faced a grim prognosis, often progressing rapidly to cirrhosis, liver failure, and hepatocellular carcinoma, with only limited and poorly tolerated off-label treatment options like pegylated interferon-alpha. This new approval fundamentally shifts the treatment landscape, offering the first and only FDA-approved therapy specifically designed to target HDV.

Bulevirtide's mechanism as a first-in-class entry inhibitor, blocking the virus's ability to infect liver cells, has demonstrated significant reductions in HDV RNA and normalization of ALT in clinical trials. This provides a much-needed specific antiviral agent for a disease that has long been considered incurable. However, the journey towards a complete cure for HDV continues. While bulevirtide shows impressive efficacy in suppressing viral replication and improving liver biochemistry, several critical questions remain:

• Optimal Treatment Duration: Studies indicate sustained responses with longer therapy, but the precise duration required to achieve a durable off-therapy response is still under investigation.

• HBsAg Loss: Bulevirtide monotherapy typically does not lead to the loss of hepatitis B surface antigen (HBsAg), which is considered the closest marker for an HDV cure. This highlights the ongoing need for combination strategies, potentially involving novel HBV-targeting agents, to achieve this more comprehensive outcome.

• Decompensated Cirrhosis: While real-world evidence hints at potential benefits in patients with decompensated cirrhosis, the current approval is limited to compensated disease. Further controlled studies are essential to fully understand the safety and efficacy profile in this vulnerable population, especially given observations of elevated bile acids.

This approval not only offers immediate relief for patients but also invigorates the broader research community, paving the way for future combination therapies and a deeper understanding of HDV pathogenesis. It underscores the potential for targeted therapies to transform outcomes in rare, severe liver diseases.