Mirum Pharmaceuticals, Inc. (Nasdaq: MIRM), a leading rare disease company, today announced that the primary endpoint was met in the Phase 3 AZURE-4 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). AZURE-4 is the second of two Phase 3 studies that will form the basis of Mirum’s U.S. registration package for brelovitug. Mirum also highlighted brelovitug data presented at the American Association for the Study of Liver Diseases’ (AASLD) The Liver Meeting®. Across three presentations, the data demonstrated deepening viral suppression, increased rates of alanine aminotransferase (ALT) normalization, and improvements in liver stiffness with longer brelovitug treatment, including in patients with advanced cirrhosis.

“AZURE-4 marks the second U.S. registrational Phase 3 study in which brelovitug met the primary endpoint of combined virologic response and ALT normalization, demonstrating consistent efficacy in patients with substantial disease burden, including higher baseline viral loads and ALT levels,” said Nancy Shulman, M.D., Executive Vice President of Clinical Development at Mirum. “Together with the favorable safety and tolerability profiles observed across both AZURE studies and the deepening responses observed with longer-term treatment in our Phase 2 studies, we believe these results support the potential of brelovitug as a potent, single-agent treatment for chronic HDV and our planned Biologics License Application (BLA) submission in the first half of 2027.”

“Hepatitis delta is the most severe form of viral hepatitis, and many patients are living with advanced liver disease, including cirrhosis,” said Tatyana Kushner, M.D., MSCE, Associate Professor of Medicine, Division of Gastroenterology and Hepatology at Weill Cornell Medicine. “New 2026 AASLD expert opinion (EXPO) recommendations recognize that all adults with HDV viremia and compensated liver disease, including compensated cirrhosis, should be considered for HDV-specific antiviral therapy. The improvements in viral suppression, ALT normalization, and liver stiffness observed with brelovitug treatment are encouraging for patients facing significant risk of disease progression.”

Phase 3 AZURE-4 Results: Brelovitug Met the Primary Endpoint at Week 24

The AZURE-4 study enrolled 113 treatment-naïve patients randomized 2:1:1 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 12. The global study population had substantial disease burden: 53% had cirrhosis, approximately half had baseline HDV RNA levels >6 log10 IU/mL, and mean baseline ALT was 122 U/L.

At Week 24, brelovitug met the primary endpoint, with 59% of patients receiving 300 mg QW and 44% receiving 900 mg Q4W achieving the combined endpoint of virologic response and ALT normalization, compared with 0% in the delayed-treatment arm (p≤0.0001 for both comparisons).

The table below summarizes key efficacy findings from the Phase 3 AZURE-1 and AZURE-4 studies and longer-term Phase 2 data presented at The Liver Meeting, highlighting deepening antiviral and ALT responses with longer-term brelovitug treatment.

Summary of Phase 3 and Phase 2 Key Efficacy Endpoints

No patients in the delayed-treatment arms of the AZURE-1 or AZURE-4 Phase 3 studies achieved the primary endpoint.

 

24 Weeks

48 Weeks

108 Weeks

 

AZURE-1

Phase 3† 

AZURE-4

Phase 3

AZURE-1

Phase 2b† 

BJT-778-001

Phase 2a†, 2

Patients with cirrhosis

 

300 mg

(n=59)

900 mg

(n=65)

300 mg

(n=58)

900 mg

(n=27)

300 mg

(n=20)

900 mg

(n=20)

900 mg

(n=15)

Combined Endpoint

56%1

p <0.0001

45%

p <0.0001

59%1

p <0.0001

44%

p=0.0001

55%

55%

100%

(Virologic Response* + ALT Normalization)

Virologic Response*

86%

85%

95%

96%

95%

95%

100%

(HDV RNA ≥2 log10 reduction including TND)

HDV RNA LLOQ, <10 IU/mL

25%

26%

31%

22%

80%

40%

87%

HDV RNA TND**

17%

17%

14%

11%

40%

25%

73%

ALT Normalization

63%

54%

60%

44%

55%

55%

100%

Full analysis set: participants randomized to brelovitug who received at least one dose of brelovitug after randomization, or participants randomized to the delayed-treatment arm.

P-values compare each brelovitug treatment group with delayed treatment using a stratum-adjusted Miettinen-Nurminen test.

Participants without evaluable data at a given time point are classified as non-responders.

† Data presented at AASLD’s The Liver Meeting 2026.

1 Prespecified primary endpoint in the Phase 3 AZURE-1 and AZURE-4 studies.

2 Patients initially receiving other dosing regimens crossed over to brelovitug 900 mg Q4W at Week 48 for the open-label extension.

* Virologic response is defined as ≥2 log10 reduction in HDV RNA from baseline, HDV RNA below the lower limit of quantification (LLOQ, <10 IU/mL), or undetectable HDV RNA (TND).

** TND: Target not detected, defined as no detectable HDV RNA using an RT-qPCR assay (Victorian Infectious Diseases Reference Laboratory; Melbourne, Australia), with a limit of detection of 5 IU/mL.

In the Phase 3 AZURE-4 study, brelovitug was well tolerated across dose groups, with no new safety signals observed. The most common adverse event was flu-like illness, reported in 17.2% and 18.5% of participants receiving 300 mg QW and 900 mg Q4W, respectively, with the majority occurring following the first dose. Low rates of injection site reactions were reported in 1.7% and 7.4% of participants, respectively.

Full results from the Phase 3 AZURE-4 study will be presented at an upcoming medical congress. Detailed analyses presented at The Liver Meeting are available in the Publications & Presentations section of Mirum’s website.

Mirum plans to submit a BLA to the U.S. Food and Drug Administration (FDA) in the first half of 2027, with a potential U.S. commercial launch in Q4 2027, if approved.

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 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 Orphan Drug Designation for the treatment of active hepatitis delta virus infection. Brelovitug also has PRIME and Orphan designations from the European Medicines Agency.

In September 2026, Mirum announced that the Phase 3 AZURE-1 study met its primary combined endpoint of virologic response and ALT normalization at Week 24, with brelovitug demonstrating a favorable safety and tolerability profile. 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-4

AZURE-4 is a Phase 3 study evaluating brelovitug in chronic hepatitis delta virus (HDV). The study enrolled 113 treatment-naïve patients randomized in a 2:1:1 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 12-week delayed therapeutic start. Patients randomized to delayed treatment initiate brelovitug 300 mg QW upon completion of the 12-week treatment-delay period.

The primary endpoint is the proportion of patients achieving a combined virologic response and ALT normalization at Week 24 in the 300 mg QW arm. The study includes an open-label extension period 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 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, the expected benefits of data from the AZURE clinical program, including the AZURE-4 study meeting its primary endpoint, expected submission and timing of the potential BLA submission and U.S. commercial launch of brelovitug, the potential benefits of brelovitug, the relationship of antiviral activity and ALT normalization as an important endpoint in HDV, the estimated prevalence of patients suffering with 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,” “should,” 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 pharmaceutical development and commercialization 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 September 30, 2026, filed with the Securities and Exchange Commission on November 3, 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.

Mirum, the Mirum logo and LIVMARLI are trademarks of Mirum Pharmaceuticals, Inc. and ATEBRIOZ is a trademark of Incyte Holdings Corporation.

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