-Primary endpoint (virologic response and ALT normalization) achieved in both dose arms at Week 24

-Favorable safety and tolerability profiles observed

- Full results to be presented in a late-breaking poster presentation at EASL 2026

-Topline Phase 3 data from AZURE-1 and AZURE-4 expected in H2 2026

FOSTER CITY, Calif.--(BUSINESS WIRE)--Apr. 27, 2026-- Mirum Pharmaceuticals, Inc. (Nasdaq: MIRM), a leading rare disease company, today announced the primary endpoint was met in the Phase 2b portion of the AZURE-1 study evaluating brelovitug, an investigational monoclonal antibody designed to bind hepatitis B surface antigen (HBsAg), for the treatment of chronic hepatitis delta virus (HDV).

The Phase 2b portion of the AZURE-1 study included the first 53 patients evaluated at Week 24 of treatment.

At Week 24, treatment with brelovitug demonstrated robust antiviral activity across both dose groups. 100% of patients in the 300 mg once weekly (QW) arm and 75% of patients in the 900 mg once every four weeks (Q4W) arm achieved virologic response (≥2 log10 reduction in HDV RNA from baseline or undetectable HDV RNA [<LLOQ, TND]), as compared to 0% in the delayed treatment arm.

Consistent with these antiviral effects, the primary composite endpoint of virologic response and alanine aminotransferase (ALT) normalization was achieved in 45% and 35% of patients in the 300 mg QW and 900 mg Q4W arms, respectively, as compared to 0% of patients in the delayed treatment arm. After 24 weeks of treatment, further reductions in ALT and HDV RNA levels have been observed. These results support the potential of brelovitug as a single agent therapy to treat HDV. The efficacy results by treatment arm in the Phase 2b portion of AZURE-1 at Week 24 are presented below in Key Efficacy Endpoints.

Treatment with brelovitug was well tolerated across dose groups. The safety profile summary is presented below in Summary of Safety.

“These results reinforce the potential for brelovitug as a well-tolerated, convenient, single agent therapy to address a critical unmet need in HDV,” said Nancy Shulman, M.D., Executive Vice President of Clinical Development at Mirum. “We observed robust antiviral activity, including 100% virologic response in the 300 mg arm at Week 24. We look forward to the Phase 3 results later this year.”

“Chronic hepatitis delta remains the most aggressive form of viral hepatitis, and new therapeutic approaches are urgently needed,” said Tatyana Kushner, M.D., MSCE, Associate Professor of Medicine, Division of Gastroenterology and Hepatology at Weill Cornell Medicine. “These results demonstrate strong antiviral activity along with improvement in liver markers, which are key indicators of clinical benefit for patients with HDV.”

“People living with chronic hepatitis delta face a severe disease burden with limited treatment options,” said Chari A. Cohen, DrPH, MPH, President of the Hepatitis B Foundation. “Advances like those seen with brelovitug represent important progress towards improving outcomes for this underserved community.”

The full results from the Phase 2b portion of the AZURE-1 study will be presented in a late-breaking poster presentation at the European Association for the Study of the Liver (EASL) Congress, May 27-30, 2026. Topline data from the Phase 3 AZURE-1 and AZURE-4 studies are expected in H2 2026, with potential BLA submission and commercial launch in the U.S. in 2027.

Key Efficacy Endpoints

Summary of Safety

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 chronic 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 infection and PRIME and Orphan designations from the European Medicines Agency.

In the previously reported 778-001 Phase 2 study, brelovitug demonstrated strong antiviral activity in HDV, achieving a 100% virologic response, along with improvements in liver enzyme levels and a favorable safety profile at Week 48. 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 and biochemical response. Together, the studies are intended to support regulatory filings in the United States and Europe.

About AZURE-1

AZURE-1 is a Phase2b/3 study evaluating brelovitug in chronic hepatitis delta virus (HDV). The study has enrolled approximately 200 treatment-naïve patients randomized in a 2:2:1 ratio to receive brelovitug 300 mg once weekly, brelovitug 900 mg once every four weeks, 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 combines deep rare disease expertise with strong connections to patient communities.

The company’s commercial portfolio includes LIVMARLI® (maralixibat) for Alagille syndrome (ALGS) and progressive familial intrahepatic cholestasis (PFIC), 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 www.mirumpharma.com 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, expected timing of topline data for the AZURE studies and potential BLA submission and commercial launch, the potential benefits of brelovitug, and 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 associated with the development of acquired product candidates, including the failure of any expected synergies to be realized; risk and uncertainties arising from the integration of an acquired company, its employees and its assets with Mirum’s business; 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 Annual Report for the year ended December 31, 2025, filed with the Securities and Exchange Commission on February 25, 2026, and subsequent filings with the Securities and Exchange Commission, which are available at www.sec.gov . All forward-looking statements contained in this press release speak only as of the date on which they were made and are based on management’s assumptions and estimates as of such date. Mirum undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made, except as required by law.

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Source: Mirum Pharmaceuticals, Inc.