Foster City, California, U.S., September 28, 2026
Mirum Pharmaceuticals has announced a major clinical-development milestone for brelovitug, an investigational fully human monoclonal antibody being developed for chronic hepatitis delta virus (HDV) infection. The company reported that the Phase 3 portion of the global AZURE-1 study met its primary endpoint at Week 24 in both brelovitug treatment groups. The primary endpoint measured a combined virologic response and alanine aminotransferase (ALT) normalization). Mirum also reported 48-week data from the Phase 2b portion of AZURE-1 showing continued viral suppression and increased rates of ALT normalization. The findings support continued late-stage development of brelovitug as Mirum works toward potential regulatory submissions.
Brelovitug Meets Primary Phase 3 Endpoint
The Phase 3 portion of AZURE-1 enrolled 153 treatment-naive patients with chronic HDV. Participants were randomized to receive brelovitug 300 mg once weekly, brelovitug 900 mg once every four weeks, or delayed treatment beginning at Week 24. At Week 24, 56% of patients receiving 300 mg once weekly and 45% receiving 900 mg every four weeks achieved the combined primary endpoint, compared with 0% in the delayed-treatment group. Both treatment comparisons achieved statistical significance, with p-values below 0.0001. Additional measurements showed that 86% of patients in the weekly-dose group and 85% in the every-four-week group achieved the study’s defined virologic response. HDV RNA fell below the lower limit of quantification in 25% and 26% of patients, respectively, while 17% in each treatment group achieved target-not-detected status. ALT normalization was observed in 63% of patients receiving weekly brelovitug and 54% receiving the every-four-week regimen. These results provide separate measures of antiviral activity and improvement in a biochemical marker of liver injury.
Investigational Antibody Targets HDV Infection
Brelovitug is a fully human monoclonal antibody designed to bind hepatitis B surface antigen (HBsAg). HDV depends on hepatitis B virus surface proteins during its lifecycle, making HBsAg an important target for therapeutic intervention. Mirum is developing brelovitug as a potential treatment for chronic hepatitis delta, a serious viral liver disease that can progress to cirrhosis, liver cancer and liver failure. The AZURE-1 program is particularly important because chronic HDV has historically had limited treatment options. However, the therapeutic landscape changed in May 2026 when the U.S. FDA approved Hepcludex (bulevirtide) as the first FDA-approved treatment for chronic HDV in adults without cirrhosis or with compensated cirrhosis. Brelovitug remains investigational and is not FDA-approved, so its Phase 3 results will need to be reviewed in the context of regulatory requirements and the broader evolving HDV treatment landscape.
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Mirum Prepares for Further Phase 3 Data
The Phase 3 AZURE-1 findings build on earlier Phase 2b results. In that portion of the study, the primary combined endpoint was achieved by 45% of patients receiving 300 mg weekly and 35% receiving 900 mg every four weeks at Week 24, compared with 0% in the delayed-treatment arm. At Week 48, both treatment groups reached a 55% rate for the combined endpoint, while measures of viral suppression and ALT normalization generally increased with continued treatment. Mirum reported that brelovitug was well tolerated across the Phase 3 dose groups, with no new safety signals observed through Week 24. The company is continuing the global AZURE clinical program, with topline results from the second pivotal study, AZURE-4, expected in the fourth quarter of 2026. Mirum plans to use AZURE-1 and AZURE-4 as the basis for a potential U.S. regulatory submission, with the company targeting a Biologics License Application (BLA) submission in the first half of 2027.
The Phase 3 AZURE-1 results mark an important milestone for Mirum’s rare-disease pipeline and demonstrate continued clinical development of brelovitug for chronic HDV. Full Phase 3 results are expected to be presented at a future medical congress, providing additional information on efficacy and safety as the program advances toward potential regulatory review.
Source: Mirum Pharmaceuticals press release
