Mirum Pharmaceuticals (Nasdaq: MIRM) reported that brelovitug met its primary endpoint in the Phase IIb portion of the AZURE-1 study in chronic hepatitis delta virus, with the composite of virologic response and ALT normalization achieved in 45% of patients receiving the 300 mg weekly dose versus 0% in the delayed-treatment arm — results that carry particular weight given the absence of any FDA-approved therapy for this indication.
The AZURE-1 study is a Phase IIb/III randomized, open-label trial enrolling approximately 200 treatment-naive patients with chronic HDV, with a prespecified interim analysis conducted on the initial 53 patients at Week 24.
Across both active arms, virologic response — defined as at least a 2 log10 reduction in HDV RNA from baseline or undetectable virus — was 100% in the 300 mg once-weekly cohort (n=20) and 75% in the 900 mg once-every-four-weeks cohort (n=20), compared with 0% in the delayed-treatment arm (n=12). The primary composite endpoint, which added ALT normalization to the virologic criterion, was met in 45% and 35% of patients in the two active arms respectively (p=0.003 and p=0.024 versus control). No treatment-related serious adverse events or discontinuations were recorded in either active arm, and Grade 3 or higher events related to treatment were absent.
Brelovitug is a fully human IgG1 monoclonal antibody that targets hepatitis B surface antigen, neutralizing HDV and HBV virions while also depleting HBsAg-containing subviral particles. That mechanism is distinct from bulevirtide (Hepcludex, Gilead Sciences), the only globally approved HDV therapy, which blocks viral entry by inhibiting the NTCP hepatocyte receptor. Bulevirtide holds EMA marketing authorization but received an FDA Complete Response Letter, leaving the US market without an approved option. Cross-trial comparisons are limited by differences in patient populations, endpoints, and follow-up duration, but the 100% virologic response rate in the weekly dosing arm, and the less-frequent dosing schedule relative to bulevirtide's daily injection, are features that will draw scrutiny as Phase III data mature.