Mirum Pharmaceuticals, a biopharmaceutical company developing treatments for rare diseases, announced its acquisition of Bluejay Therapeutics, a biotechnology focused on viral and liver diseases, on December 8th, 2025. According to a company press release, Mirum will acquire all outstanding shares of Bluejay for $620 million in total upfront compensation, with an additional $200 million in compensation contingent on various tier-based milestones.
The acquisition grants Mirum worldwide rights to Bluejay’s brelovitug, a monoclonal antibody under investigation as a treatment for chronic hepatitis delta virus (HDV), a rare liver disease. Brelovitug, which targets the surface antigens (anti-HBsAg) on both the HDV virus and the hepatitis B virus, is designed to neutralize and remove hepatitis D and V virions and deplete HBsAg-containing subviral particles.
According to the release, in Phase II studies brelovitug achieved a 100% HDV RNA response, as well as improvements in liver enzyme levels and a favorable safety profile. It is now being evaluated in the AZURE Phase III clinical development program for HDV, with top-line data from the program expected in the second half of 2026. Brelovitug has previously received a Breakthrough Therapy designation from FDA and both Orphan and PRIME designations from EMA for HDV.
“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, Mirum Pharmaceuticals, in the release. “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.”
“Bluejay was founded to develop transformative therapies for people with viral and liver diseases and, working with regulatory agencies, such as the FDA and the European Medicines Agency, the Bluejay team developed brelovitug from clinical development candidate to global Phase 3 trial in four years,” said Keting Chu, Founder and CEO, Bluejay Therapeutics, in the release. “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.”
