Rare disease company Mirum Pharmaceuticals Inc (Nasdaq:MIRM) on Monday announced a definitive agreement to acquire Bluejay Therapeutics, a privately held biotechnology company focused on viral and liver diseases.

This acquisition adds worldwide rights to brelovitug, a late-stage monoclonal antibody with Breakthrough Therapy and PRIME designations for chronic hepatitis delta virus (HDV), a rare liver disease with no FDA-approved therapies.

Brelovitug is being evaluated in the global AZURE Phase 3 programme, with top-line results expected in the second half of 2026 and potential BLA submission and launch in 2027. Phase 2 data demonstrated strong antiviral activity, 100% HDV RNA response, improved liver enzymes, and a favourable safety profile.

Under the terms of the deal, Mirum will pay USD250m in cash and USD370m in Mirum common stock, plus up to USD200m in potential sales-based milestones. The acquisition has board approval from both companies and is expected to close in Q1 2026, subject to regulatory and customary closing conditions.

A concurrent private placement of Mirum stock and pre-funded warrants is expected to raise approximately USD200m to support clinical development and commercialisation.

Mirum will evaluate strategic options for Bluejay's other investigational programmes following the acquisition.