Mirum to Acquire Bluejay and Its Late-Stage HDV Candidate for Up to US$820M

Mirum Pharmaceuticals has signed a definitive agreement to acquire Bluejay Therapeutics, a private biotech firm specialising in viral and liver diseases. The transaction brings into Mirum’s portfolio worldwide rights to brelovitug (BJT-778) — a fully human monoclonal antibody being developed for chronic Hepatitis D virus infection (HDV), the most severe form of viral hepatitis, currently without approved therapies. 

Under the terms of the deal, Mirum will pay US$250 million in cash and US$370 million in stock upfront. Bluejay’s shareholders may receive an additional up to US$200 million in sales-based milestones, bringing total deal value to as much as US$820 million. The acquisition adds a potentially transformative late-stage asset to Mirum’s rare-disease pipeline and leverages Bluejay’s positive Phase 2 data, which demonstrated full virologic response and liver enzyme improvement over 48 weeks of treatment. 

Mirum expects top-line Phase 3 results from brelovitug in the second half of 2026. If successful, the company may pursue regulatory approval and market launch in 2027, positioning brelovitug as a first-in-class therapy for HDV.  This acquisition aligns with Mirum’s broader strategy to lead in rare liver diseases.