Gilead Sciences Inc. (NASDAQ: GILD) announced the U.S. Food and Drug Administration granted accelerated approval for Hepcludex (bulevirtide-gmod) 8.5 mg to treat adults with chronic hepatitis delta virus infection. The drug represents the first FDA-approved treatment for HDV in the United States.

The FDA based its accelerated approval on reductions in HDV RNA and normalization of alanine aminotransferase levels, supported primarily by data from the Phase 3 MYR301 study. At week 48, the study demonstrated statistically significant improvement versus the control group in combined virologic and biochemical response. The approval notes that improvement in disease-related clinical outcomes has not been established, and continued approval may depend on verification of clinical benefit in a confirmatory trial.

Chronic HDV affects an estimated 40,000 to 80,000 people in the United States, representing 2% to 4% of individuals with chronic hepatitis B virus. HDV occurs only as a co-infection in individuals who have HBV and is associated with rapid disease progression, liver failure, and increased mortality compared with HBV alone.

The MYR301 study evaluated Hepcludex efficacy and safety in adults with chronic HDV, with treatment administered for up to 144 weeks followed by 96 weeks of off-treatment follow-up. The drug met its primary endpoint at week 48 and demonstrated sustained efficacy through up to 144 weeks of treatment.

Hepcludex is administered as an 8.5 mg once-daily subcutaneous injection. The most common adverse reactions in clinical trials were injection site reactions, headache, abdominal pain, fatigue and pruritus. The drug carries a boxed warning for severe acute exacerbations of hepatitis D and B that may occur after discontinuation.

Bulevirtide 2 mg is approved for HDV treatment in the European Economic Area and other countries globally.