Mirum Pharmaceuticals enters into definitive Agreement to acquire Bluejay Therapeutics, expanding global leadership in Rare Disease, including HDV
Mirum Pharmaceuticals, Inc., a leading rare disease company, 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 3 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 2 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 3 program is currently enrolling patients, with top-line data expected in 2H 2026 and potential BLA submission and launch in 2027.
Under the terms of the definitive agreement, Mirum has agreed to acquire all outstanding shares of Bluejay for $250 million in cash and $370 million in Mirum common stock, plus potential tiered sales-based milestone payments of up to $200 million in cash.
The transaction with Bluejay has been approved by the Boards of Directors of both companies and is expected to close in the first quarter of 2026, subject to regulatory approval and other customary closing conditions.
Beyond brelovitug for HDV, Mirum will evaluate strategic options for Bluejay’s additional investigational programs after close.
About Brelovitug
Brelovitug is an investigational, highly potent, pan-genotypic, fully human immunoglobulin G1 (IgG1) monoclonal antibody (mAb) that targets the surface antigen (anti-HBsAg) on both the chronic hepatitis D virus (HDV) and the hepatitis B virus (HBV). Brelovitug is designed to neutralize and remove hepatitis B and hepatitis D virions and deplete HBsAg-containing subviral particles. Brelovitug has FDA Breakthrough Therapy designation for the treatment of HDV and PRIME and Orphan designations from the European Medicines Agency. Following the anticipated close of the Bluejay acquisition, Mirum Pharmaceuticals, Inc. will own worldwide rights to brelovitug.
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