Mirum Pharmaceuticals says Phase 3 AZURE-1 met primary endpoint in chronic HDV study

m. ET Mirum Pharmaceuticals, Inc. (Nasdaq: MIRM), a leading rare disease company, today announced the primary endpoint was met in the Phase 3 portion of the AZURE-1 study evaluating brelovitug, an investigational fully human monoclonal antibody that binds to hepatitis B surface antigen (HBsAg), for the treatment of chronic hepatitis delta virus (HDV). In addition, 48-week data from the Phase 2b portion of AZURE-1 demonstrated deepening viral suppression, with a greater proportion of patients achieving HDV RNA below the lower limit of quantification (LLOQ, <10 IU/mL) and target not detected (TND), and increased rates of alanine aminotransferase (ALT) normalization.

S. registration package for brelovitug. “These results demonstrate the potential of brelovitug as a well-tolerated, convenient, single agent to deliver both deep viral suppression and ALT normalization, with responses that continue to deepen through 48 weeks of treatment. , Executive Vice President of Clinical Development at Mirum.

, MPH, Professor of Medicine and Chief of the Division of GI and Liver at the Keck School of Medicine of USC, and an AZURE-1 investigator. “ALT is a marker of liver injury, so seeing virologic response alongside ALT normalization is encouraging in a long-term therapy. ” “Chronic hepatitis delta is a lifelong disease, and people living with it need treatment options that are effective, safe and tolerable enough to stay on over time. That’s especially true for patients with more advanced disease, who often have the fewest choices,” said Chari A.

Cohen, DrPH, MPH, President of the Hepatitis B Foundation. ” Phase 3 AZURE-1 Results: Brelovitug Met the Primary Endpoint at Week 24 The Phase 3 portion of the AZURE-1 study enrolled 153 treatment-naive patients randomized in a 2:2:1 ratio to receive brelovitug 300 mg self-administered once weekly (QW) by subcutaneous (SC) injection, brelovitug 900 mg administered once every four weeks (Q4W) by SC injection, or delayed treatment starting at Week 24. This global study enrolled a broad patient population including patients with advanced disease. 0001 for both comparisons).

The efficacy results by treatment arm at Week 24 are presented below in Phase 3 Key Efficacy Endpoints. Treatment with brelovitug was well tolerated across dose groups, with a safety profile consistent with previously reported AZURE-1 data. The safety profile summary is presented below in Phase 3 Summary of Safety Through Week 24. 0001 Virologic Response 86% 85% 0% (HDV RNA ≥2 log10 reduction or TND) HDV RNA LLOQ, <10 IU/mL 25% 26% 0% HDV RNA TND 17% 17% 0% ALT Normalization 63% 54% 0% Full analysis set; participants who were randomized to brelovitug treatment and received at least one dose of brelovitug after randomization or randomized to the delayed treatment arm.

P-values compare each treatment group against delayed treatment using a stratum-adjusted Miettinen Nurminen test. 8) 0 Grade 4 acute myocardial infarction. 48-Week Data from the Phase 2b Portion of AZURE-1: Deepening Viral Suppression and Increased Rates of ALT Normalization The Phase 2b portion of AZURE-1 included the first 53 patients enrolled in the study. Following the previously reported Week 24 primary analysis ( ), patients continued treatment in the open-label extension.

Between Week 24 and Week 48, viral suppression deepened and rates of ALT normalization increased. The Week 48 results are presented below in Phase 2b Key Efficacy Endpoints (Weeks 24 and 48). 024 Virologic Response 100% 95%(b) 75%(c) 95%(c) (HDV RNA ≥2 log10 reduction or TND) HDV RNA LLOQ, <10 IU/mL 45% 80% 10% 40% HDV RNA TND 35%(d) 40% 5% 25% ALT Normalization 45% 55% 40% 55% Full analysis set; participants receiving at least one post-baseline efficacy assessment. (a) One participant discontinued after first dose and did not provide on-treatment results.

(b) One participant considered a virologic responder at Week 24 was lost to follow-up due to relocation and had missing Week 48 data. This participant was considered a non-responder at Week 48. (c) One participant had Week 12 virologic response but was subsequently lost to follow-up. This participant was considered a non-responder at Week 24 and Week 48.

(d) One participant had a late Week 24 result (post-Week 24 analysis cutoff) that was TND. P-values compare each treatment group against delayed treatment using a stratum-adjusted Cochran-Mantel-Haenszel (CMH) test. Safety in the Phase 2b portion through Week 48 was consistent with previously reported results, with no new safety signals observed. The full results from the Phase 3 AZURE-1 study will be presented at an upcoming medical congress.

S. registration package, are expected in Q4 2026. S. S.

in Q4 2027. m. ET to share topline results from the Phase 3 AZURE-1 study of brelovitug in HDV, along with 48-week data from the Phase 2b portion of the study. Join the call using the following details: Conference Call Details: US/Toll-Free: +1 833 461 5787 International: +1 585 542 9983 Access Code: 979912911 You may also access the call via webcast by visiting the Investors section of Mirum’s corporate website.

The archived webcast will be available for replay. About Chronic Hepatitis Delta Virus (HDV) HDV, an infection that occurs in some people infected with the hepatitis B virus, is the most severe form of viral hepatitis due to the potential for rapid progression to liver cirrhosis, liver cancer, and liver-related death. HDV affects approximately 230,000 people in the United States and Europe. It is estimated that more than 50% of individuals with HDV will die of liver-related causes within 10 years of diagnosis.

There are currently no approved treatments for HDV in the United States and in most countries worldwide. About Brelovitug Brelovitug is an investigational, highly potent, pan-genotypic, fully human immunoglobulin G1 (IgG1) monoclonal antibody (mAb) that targets the surface antigen (anti-HBsAg) on both the hepatitis delta virus (HDV) and the hepatitis B virus (HBV). Brelovitug is designed to neutralize and remove hepatitis B and hepatitis D virions and deplete HBsAg-containing subviral particles. Brelovitug has FDA Breakthrough Therapy designation for the treatment of chronic HDV and PRIME and Orphan designations from the European Medicines Agency.

In April 2026, Mirum announced that in the Phase 2b portion of the AZURE-1 study, treatment with brelovitug demonstrated strong antiviral activity in HDV and achieved the primary combined endpoint of virologic response and alanine aminotransferase (ALT) normalization at Week 24 in both brelovitug dose arms as compared to the delayed treatment arm. Favorable safety and tolerability profiles were observed. Brelovitug is currently being evaluated in the global Phase 3 AZURE clinical program. Mirum owns worldwide rights to brelovitug.

About the AZURE Clinical Program The AZURE program is a global, registrational Phase 3 clinical development program evaluating brelovitug for the treatment of chronic hepatitis delta virus (HDV). The program includes multiple open-label studies designed to assess the primary endpoint of combined virologic response and ALT normalization. Together, the studies are intended to support regulatory filings in the United States and Europe. About AZURE-1 AZURE-1 is a Phase 2b/3 study evaluating brelovitug in chronic hepatitis delta virus (HDV).

The study has enrolled approximately 200 treatment-naive patients randomized in a 2:2:1 ratio to receive brelovitug 300 mg self-administered once weekly (QW) by subcutaneous (SC) injection, brelovitug 900 mg administered once every four weeks (Q4W) by SC injection, or 24-week delayed therapeutic start. Patients randomized to delayed treatment initiate brelovitug 300 mg once weekly upon completion of the treatment delay in the study. The Phase 2b portion of the study included the initial approximately 50 patients enrolled, with a prespecified safety and efficacy analysis conducted upon availability of 24-week data from that cohort.

The primary endpoint of the study is the proportion of patients achieving combined virologic response and ALT normalization at Week 24 and includes open-label extension periods of up to 96 weeks. About Mirum Pharmaceuticals Mirum Pharmaceuticals (NASDAQ: MIRM) is a leading rare disease company with a global footprint of approved products and a broad pipeline of investigational medicines. Purpose-built to bring forward breakthrough medicines for people with overlooked conditions, Mirum focuses on rare liver and rare genetic diseases, where it has built deep expertise and strong connections to patient communities.

The company’s commercial portfolio includes LIVMARLI(®) (maralixibat) for Alagille syndrome (ALGS) and progressive familial intrahepatic cholestasis (PFIC), ATEBRIOZ™ (zilurgisertib) for fibrodysplasia ossificans progressiva (FOP), CHOLBAM(®) (cholic acid) for bile-acid synthesis disorders and CTEXLI(®) (chenodiol) for cerebrotendinous xanthomatosis (CTX).

Mirum’s clinical-stage pipeline includes volixibat, an IBAT inhibitor in late-stage development for primary sclerosing cholangitis (PSC) and primary biliary cholangitis (PBC), brelovitug, a fully human monoclonal antibody in late-stage development for chronic hepatitis delta virus (HDV) and MRM-3379, a PDE4D inhibitor being evaluated for Fragile X syndrome (FXS). Mirum’s success is driven by a team dedicated to advancing high impact medicines through strategic development, disciplined execution and purposeful collaboration across the rare disease ecosystem.

Learn more at and follow Mirum on Facebook ( ), LinkedIn ( ), Instagram and X Forward-Looking Statements Statements contained in this press release regarding matters that are not historical facts are “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995.

Such forward-looking statements include statements regarding, among other things, the expected timing of topline data for the AZURE studies and potential BLA submission and commercial launch, the potential benefits of brelovitug, the relationship of antiviral activity as an important endpoint in HDV and the success or approval of any potential regulatory submission for brelovitug. Because such statements are subject to risks and uncertainties, actual results may differ materially from those expressed or implied by such forward-looking statements.

Words such as “anticipate,” “expected,” “will,” “could,” “would,” “potential,” “continue,” “plans,” “intended,” “believe,” and similar expressions are intended to identify forward-looking statements. These forward-looking statements are based upon Mirum’s current expectations and involve assumptions that may never materialize or may prove to be incorrect.

Actual results could differ materially from those anticipated in such forward-looking statements as a result of various risks and uncertainties, which include, without limitation, risks and uncertainties with the development of investigational medicines generally, including the failure of future studies to generate the same or similar data as prior studies and the potential that estimated prevalences are materially inaccurate; the risks and uncertainties associated with Mirum’s business in general, the impact of geopolitical and macroeconomic events, and the other risks described in Mirum’s Quarterly Report on Form 10-Q for the quarter ended June 30, 2026, filed with the Securities and Exchange Commission on August 5, 2026, and subsequent filings with the Securities and Exchange Commission, which are available at ( ).

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