Mirum Pharma to acquire Bluejay Therapeutics

US rare disease drug developer Mirum Pharmaceuticals (Nasdaq: MIRM) today announced its entry into a definitive agreement to acquire Bluejay Therapeutics, a privately held biotechnology company focused on viral and liver diseases.

The transaction would add worldwide rights to brelovitug, a late-stage, fully human monoclonal antibody with Breakthrough Therapy and PRIME designations for chronic hepatitis delta virus (HDV) to Mirum’s portfolio of rare liver programs. This acquisition is expected to advance Mirum’s leadership in rare disease, build on its deep expertise in rare liver disorders and add a fourth potential registrational readout for the company over the next 18 months.

Brelovitug is being evaluated in the AZURE Phase III registrational program for HDV, the most severe form of viral hepatitis. HDV occurs in people already infected with hepatitis B; nearly half of those affected progress to liver-related death within 10 years of diagnosis due to rapid progression to fibrosis, cirrhosis, hepatic decompensation and an increased risk of liver cancer. In Phase II studies, brelovitug demonstrated strong antiviral activity in HDV, achieving 100% HDV RNA response, along with improvements in liver enzyme levels and a favorable safety profile, with the most common adverse event being injection-site erythema. The ongoing global AZURE Phase III program is currently enrolling patients, with top-line data expected in second-half 2026 and potential biologics license application (BLA) submission and launch in 2027.