Mirum acquires Bluejay Therapeutics to expand rare liver disease pipeline

Agreed in December 2025, the transaction is valued at up to $820m and brings the late-stage monoclonal antibody brelovitug, a candidate for chronic hepatitis delta virus (HDV), into Mirum’s global portfolio.

With this deal closure, Mirum secures worldwide rights to the fully human antibody, currently in trials for HDV, a condition lacking approved therapies in the US.

Brelovitug has received breakthrough therapy designation from the US Food and Drug Administration (FDA) and prime designation from the European Medicines Agency.

According to the agreement, Mirum acquired all outstanding shares of Bluejay Therapeutics through a combination of cash and Mirum common stock, along with possible tiered sales-based milestone payments.

Simultaneously, Mirum completed private placement financings with commitments from existing and new healthcare investors, raising nearly $268.5m.

These proceeds are allocated for commercialisation activities and clinical development of brelovitug in HDV while strategic options for Bluejay’s other pipeline programmes are under consideration.

Brelovitug is an investigational immunoglobulin G1 (IgG1) antibody targeting hepatitis B Surface Antigen (HBsAg) on both hepatitis B virus (HBV) and HDV, showing potent pan-genotypic activity.

Mirum Pharmaceuticals CEO Chris Peetz said: “With the acquisition now complete, our focus shifts to execution – adding the talented Bluejay team to Mirum as we complete the AZURE Phase III programme and prepare for potential registrations and launches.

“This programme fits squarely within our core strengths in rare disease and builds on our deep expertise in rare liver conditions. We believe Mirum’s global development and commercial synergies position us well to deliver for patients living with HDV.”

The AZURE global Phase III registrational programme of brelovitug comprises multiple open-label trials assessing biochemical and virologic response endpoints to support regulatory filings in Europe and the US, targeting a potential biologics licence application (BLA) submission and la

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