Mirum Pharmaceuticals Inc., a rare disease company, has agreed 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 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. 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.

“This acquisition fits squarely with what we do best – advancing high-impact medicines for patients with rare diseases through disciplined development, regulatory innovation, and commercial excellence,” said Chris Peetz, CEO of Mirum Pharmaceuticals. “Brelovitug in HDV leverages our deep expertise in rare liver disease and builds on the relationships we’ve established with key providers through the volixibat and LIVMARLI programs. The Bluejay team has done commendable work advancing brelovitug to this stage and we look forward to building on that progress to bring this important new treatment to people living with HDV.”

Keting Chu, Founder and CEO of Bluejay Therapeutics, said, “Brelovitug has the potential to redefine HDV treatment, and Mirum’s rare disease leadership, commitment to rare liver communities and commercialization expertise make it the right company to carry this program forward globally.”

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 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.

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