Mirum Pharmaceuticals agreed to acquire Bluejay Therapeutics to secure brelovitug, a monoclonal antibody in late‑stage testing for chronic hepatitis D virus (HDV). The transaction calls for $620 million in cash and stock plus up to $200 million in sales milestones; Mirum also announced a related private placement expected to raise about $200 million. Bluejay’s phase 2 readout showed complete HDV RNA responses in that study and the phase 3 program is underway with top‑line data expected next year. Mirum said the acquisition leverages its rare‑liver expertise and could support an FDA submission and commercial launch in 2027.