Gilead Sciences, Inc. announced Week 48 results from the Pivotal Phase 3 clinical trial evaluating the first-in-class entry inhibitor Hepcludex® (bulevirtide) for the treatment of chronic hepatitis delta virus (HDV) infection. Findings from the study underscore the efficacy and safety of bulevirtide for the treatment of chronic HDV and are being presented in the International Liver Congress™ (ILC) 2022 Official Press Program. In addition, Week 48 data demonstrating the positive impact of bulevirtide on patient-reported outcomes (PROs) in people living with chronic HDV will also be presented.

Together, these data reinforce the clinical utility of bulevirtide as monotherapy for the treatment of chronic HDV. There are currently no other approved treatment options for HDV and people living with HDV typically have a poor prognosis. At Week 48, study participants treated with bulevirtide monotherapy at 2 mg or 10 mg once daily achieved a significantly greater combined virological and biochemical response (45% and 48%, respectively) when compared to participants who had not received antiviral treatment at this stage of the study (2%).

Combined response was defined as undetectable HDV RNA or a decrease by 2 log10 IU/mL from baseline and ALT normalization. Similarly, when the Week 48 data is considered alongside the integrated Week 24 analyses of the ongoing Phase 2 studies (MYR202 and MYR203) and the interim Week 24 Phase 3 MYR301 data presented at ILC 2021, combined response rates of bulevirtide increased from Week 24 to Week 48, highlighting an improved response of bulevirtide with prolonged treatment. The safety profile of bulevirtide at Week 48 is consistent with prior reports, with no participants having an adverse event (AE) leading to discontinuation of bulevirtide and no serious AEs attributed to bulevirtide treatment.

The safety profile at both Week 24 and again at Week 48 reassert the safety and tolerability profile of bulevirtide, which is an important factor for people living with chronic HDV. In an oral presentation, Gilead will also share an exploratory analysis of the Week 48 data from the Phase 3 MYR301 study, evaluating the impact of bulevirtide (2 mg once daily) on PROs in people living with chronic HDV. Participants treated with bulevirtide 2 mg (n=49) showed significant improvements from baseline at 48 weeks in almost all assessed health-related quality-of-life domains of the Hepatitis Quality of Life questionnaire.

Participants in the control group (n=51) remained largely unchanged, apart from significant improvements in health distress and hepatitis-specific health distress. Of note, participants receiving bulevirtide 2 mg reported significant improvements in performance of daily activities related to hepatitis, emotional impact of hepatitis and improvement in work compared with controls. Bulevirtide was granted Conditional Marketing Authorization by the European Commission and is an investigational agent in the U.S. and outside of the European Economic Area.

In these regions, health authorities have not established the safety and efficacy of bulevirtide. A Biologics License Application (BLA) was submitted in Fourth Quarter 2021 to the U.S. Food and Drug Administration (FDA) for bulevirtide for injection (2 mg) to treat adults with HDV and compensated liver disease. This Phase 3 data is included in the filing of bulevirtide to the FDA.

Bulevirtide has been granted Breakthrough Therapy and Orphan Drug designations by the FDA. In 2020 bulevirtide 2 mg was granted Conditional Marketing Authorization by the European Commission and PRIority MEdicines (PRIME) scheme eligibility by the European Medicines Agency as the first approved treatment in Europe for adults with chronic HDV and compensated liver disease. MYR301 is an ongoing Phase 3 clinical trial evaluating the long-term efficacy and safety of bulevirtide in 150 people living with chronic HDV randomly allocated to treatment with bulevirtide 2 mg once daily (n=49), 10 mg once daily (n=50) or no antiviral treatment (delayed treatment, n=51).

Primary efficacy and safety data will be assessed at Week 48. After Week 48, participants in the delayed treatment group of the study will be switched to bulevirtide 10 mg once daily for an additional 96 weeks. The total duration of treatment across all groups in the study is 144 weeks.

The primary endpoint, combined response, is defined as an undetectable HDV RNA (10 IU/ml decline from baseline and ALT normalization at Week 48. Secondary endpoints at Week 48 include undetectable HDV RNA (key secondary endpoint), ALT normalization, and a change from baseline in liver stiffness measured by transient elastography. Chronic HDV is the most severe form of viral hepatitis and can have mortality rates as high as 50% within five years in cirrhotic patients.

HDV occurs only as a co-infection in individuals who have hepatitis B virus (HBV). It is estimated that at least 12 million people worldwide are currently co-infected with HDV and HBV. HDV co-infection is associated with a faster progression to liver fibrosis, cirrhosis and hepatic decompensation and an increased risk of liver cancer and death.

In the U.S. and Europe, there are more than 230,000 people living with HDV; however, it remains underdiagnosed globally.