Bluejay Therapeutics, acquired by Mirum Pharmaceuticals in 2026, was developing brelovitug, a fully human monoclonal antibody with Breakthrough Therapy and PRIME designations for chronic hepatitis delta virus (HDV). 

At the time of acquisition, brelovitug was being evaluated in the AZURE Phase 3 registrational program for HDV, the most severe form of viral hepatitis. HDV occurs in people already infected with hepatitis B; nearly half of those affected progress to liver-related death within 10 years of diagnosis due to rapid progression to fibrosis, cirrhosis, hepatic decompensation and an increased risk of liver cancer.

Background

Founded in 2021

Acquired by Mirum Pharmaceuticals in 2026 (Nasdaq: MIRM)

Therapeutic Focus: Viral and Liver Diseases

RiverVest Fund V Investment 

$20 million Series A in 2021 (co-led)

$41 million Series B in 2022

$182 million Series C in 2024