Mirum Pharmaceuticals Acquires Bluejay Therapeutics for $620M to Advance Breakthrough HDV Treatment
Key Insights
Mirum Pharmaceuticals announced a $620 million acquisition of Bluejay Therapeutics (search) to gain worldwide rights to brelovitug, a monoclonal antibody with FDA Breakthrough Therapy designation for chronic hepatitis delta virus (search) (HDV (search)).
Brelovitug demonstrated 100% HDV (search) RNA response in Phase 2 studies and is currently in the global AZURE Phase 3 registrational program, with top-line results expected in the second half of 2026.
HDV (search) affects approximately 230,000 people in the United States and Europe, with more than 50% of patients dying from liver-related causes within 10 years of diagnosis.
Mirum Pharmaceuticals announced its entry into a definitive agreement to acquire Bluejay Therapeutics (search) for $620 million, gaining worldwide rights to brelovitug, a late-stage monoclonal antibody targeting chronic hepatitis delta virus (search) (HDV (search)). The transaction positions Mirum to address a significant unmet medical need in rare liver disease, with HDV representing the most severe form of viral hepatitis and having no FDA-approved treatments.
Strategic Acquisition Details
Under the agreement terms, Mirum will 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. The Mirum common stock issued to Bluejay security holders will be priced at $71.2085 per share. Concurrently, Mirum secured approximately $200 million in gross proceeds through a private placement with healthcare investors, with shares priced at $68.48 per share.
The transaction has received approval from both companies' boards of directors and is expected to close in the first quarter of 2026, subject to regulatory approval and customary closing conditions.
Brelovitug's Clinical Profile and Regulatory Status
Brelovitug is an investigational, highly potent, pan-genotypic, fully human immunoglobulin G1 (IgG1) monoclonal antibody that targets the surface antigen (anti-HBsAg) on both chronic hepatitis D virus and hepatitis B virus (search). The drug is designed to neutralize and remove hepatitis B and hepatitis D virions while depleting HBsAg-containing subviral particles.
The therapy has received FDA Breakthrough Therapy designation for HDV (search) treatment and PRIME and Orphan designations from the European Medicines Agency. In Phase 2 studies, brelovitug demonstrated strong antiviral activity, achieving 100% HDV RNA response along with improvements in liver enzyme levels and a favorable safety profile, with injection-site erythema being the most common adverse event.
AZURE Phase 3 Program and Timeline
The ongoing global AZURE Phase 3 registrational program is currently enrolling patients across multiple open-label studies designed to assess the primary endpoint of combined virologic and biochemical response. The program is structured to support regulatory filings in both the United States and Europe.
Top-line data from the AZURE program are expected in the second half of 2026, with potential BLA submission and commercial launch anticipated in 2027. This timeline would add a fourth potential registrational readout for Mirum over the next 18 months.
Disease Burden and Market Opportunity
HDV (search) represents a coinfection that occurs in people already infected with hepatitis B virus (search), affecting approximately 230,000 people in the United States and Europe. The disease carries a particularly severe prognosis, with nearly half of those affected progressing to liver-related death within 10 years of diagnosis due to rapid progression to fibrosis, cirrhosis, hepatic decompensation, and increased liver cancer (search) risk.
More than 50% of individuals with HDV (search) are estimated to die of liver-related causes within 10 years of diagnosis. Currently, no approved treatments exist for HDV in the United States and most countries worldwide, representing a significant unmet medical need.
Leadership Perspectives
"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, Chief Executive Officer of Mirum Pharmaceuticals. "Brelovitug in HDV (search) 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."
Keting Chu, Founder and CEO of Bluejay Therapeutics (search), noted the rapid development timeline: "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. Brelovitug has the potential to redefine HDV (search) 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."
Strategic Synergies
The acquisition is expected to be highly synergistic with Mirum's existing liver expertise and proven global commercial capabilities. Mirum's current commercial portfolio includes LIVMARLI (maralixibat) for Alagille syndrome (search) and progressive familial intrahepatic cholestasis (search), CHOLBAM (cholic acid) for bile-acid synthesis disorders, and CTEXLI (chenodiol) for cerebrotendinous xanthomatosis (search).
Beyond brelovitug for HDV (search), Mirum will evaluate strategic options for Bluejay's additional investigational programs after the transaction closes, including programs aimed at developing combination regimens for a functional cure of chronic hepatitis B.