Mirum Pharmaceuticals Completes Enrollment in Phase 3 EXPAND Study of LIVMARLI® (maralixibat) in Additional Rare Cholestatic Liver Diseases

Key Terms

phase 3 medical

Phase 3 is the late-stage clinical testing step for a new drug or medical treatment, where the product is given to large groups of patients to confirm effectiveness, monitor side effects, and compare it to standard care. Successful Phase 3 results are often the final scientific hurdle before regulators decide on approval and market launch—like passing a final exam before graduation—and can sharply change a company's valuation and future revenue prospects.

randomized medical

Randomized means participants or units in a study are assigned to different groups by chance rather than by choice, like flipping a coin to decide who gets a new treatment and who gets a comparison. For investors, randomized designs matter because they reduce bias and make results more trustworthy, so outcomes from randomized studies carry more weight when assessing regulatory approval, commercial prospects, and the risk that trial results will change a company’s valuation.

double-blind medical

A double-blind process means that neither the people conducting an activity nor the people involved know certain key details, such as who is receiving a treatment or a placebo. This approach helps prevent bias from influencing the results, making the outcome more trustworthy. For investors, it ensures that decisions or judgments are based on unbiased information rather than preconceived opinions or expectations.

placebo-controlled medical

"Placebo-controlled" describes a testing method where one group receives the actual treatment or intervention, while another group receives a harmless, inactive version called a placebo. This approach helps determine whether the real treatment has genuine effects beyond psychological expectations. For investors, understanding this ensures confidence that reported benefits are real and not influenced by bias or false perceptions.

pruritus medical

Pruritus is the medical term for an unpleasant itch sensation that makes a person want to scratch, ranging from mild irritation to severe, persistent discomfort like an itch you can’t stop rubbing. For investors, it matters because it can be a key symptom or side effect in clinical trials, affect drug labeling and regulatory decisions, drive market demand for treatments, and signal safety or tolerability issues that influence a healthcare product’s commercial prospects.

serum bile acids medical

Molecules produced by the liver that help digest fats and are normally recycled in the gut, measured in a blood test to see how well the liver and bile system are working. For investors, abnormal serum bile acid levels act like an engine warning light for liver or digestive disease risk, influencing demand for diagnostics, treatments, veterinary products, and drug safety assessments that can affect companies’ revenues and regulatory prospects.

primary endpoint medical

The primary endpoint is the single main result a clinical study is designed to measure to decide if a treatment works, like the finish line in a race that tells you who won. Investors care because meeting or missing this goal drives regulatory decisions, future sales expectations and stock value — it turns trial data into a clear yes-or-no signal about a drug’s commercial prospects.

secondary endpoints medical

Secondary endpoints are the additional outcomes measured in a clinical study beyond the main goal; they can include effects on symptoms, quality of life, safety measures, or other health indicators. For investors, they matter because positive or negative secondary results can strengthen or weaken the overall story about a treatment’s benefits and risks—like seeing not only that a car reaches its destination (primary goal) but also how comfortable and efficient the ride was (secondary findings).

- Study designed to support potential label expansion into additional settings of cholestatic pruritus

- Topline data expected in Q4 2026

FOSTER CITY, Calif.--(BUSINESS WIRE)-- Mirum Pharmaceuticals, Inc. (Nasdaq: MIRM), a leading rare disease company, today announced completion of enrollment in EXPAND, a Phase 3 randomized, double-blind, placebo-controlled study evaluating LIVMARLI^® (maralixibat) for the treatment of cholestatic pruritus in patients aged 6 months or older with rare cholestatic liver diseases, including biliary atresia.

Cholestatic liver diseases are characterized by impaired bile flow, resulting in elevated serum bile acids, severe pruritus, and significantly reduced quality of life. While LIVMARLI is approved in the United States and European Union for the treatment of cholestatic pruritus associated with Alagille syndrome and progressive familial intrahepatic cholestasis (PFIC), patients with other rare cholestatic liver diseases continue to experience debilitating itch and treatment options remain limited.

“Completing enrollment in EXPAND marks an important milestone in our efforts to broaden the reach of LIVMARLI to additional patients living with cholestatic pruritus,” said Joanne Quan, M.D., Chief Medical Officer at Mirum Pharmaceuticals. “Itch due to cholestasis profoundly affects the daily lives of patients and their families. We aim to address the unmet medical needs of these patients by leveraging our established IBAT mechanism.”

The EXPAND study enrolled patients with cholestatic pruritus associated with a range of rare cholestatic liver diseases. In the 20-week placebo-controlled portion, patients are randomized to receive maralixibat 285 micrograms per kilogram (µg/kg) twice daily or placebo. The primary endpoint is change in pruritus severity from baseline to Week 20. Secondary endpoints include changes in serum bile acids and other markers of cholestatic liver disease.

“For the patients and families living with rare liver diseases, cholestatic pruritus isn’t just an itch—it can be relentless, exhausting, and life-altering,” said Dr. Mercedes Martinez, M.D., Professor of Pediatrics and Medicine at CUMC, Columbia University Vagelos College of Physicians and Surgeons. “Yet for many of these conditions, there are still no approved treatment options for pruritus. The EXPAND study marks an important milestone in exploring whether a targeted therapy like LIVMARLI can offer meaningful relief to patients who urgently need better treatment options.”

“Families affected by biliary atresia and other rare cholestatic conditions understand the relentless burden of itch,” said Jen Lau, MPH, Co-Founder and Executive Director of BARE, Inc. (Biliary Atresia Research and Education). “The completion of enrollment in EXPAND brings hope that more patients may soon have access to a much-needed treatment option.”

Topline data from the EXPAND study are expected in the fourth quarter of 2026.

About the EXPAND Phase 3 Study

EXPAND is a Phase 3, randomized, double-blind, placebo-controlled study evaluating the safety and efficacy of LIVMARLI^® (maralixibat) in children aged 6 months and older and adults with cholestatic pruritus associated with rare cholestatic liver diseases. These diseases include biliary atresia and other rare conditions for which LIVMARLI is not currently approved.

The primary endpoint is change in pruritus severity from baseline to Week 20. Secondary endpoints include changes in serum bile acids and other markers of cholestatic liver disease.

About LIVMARLI^® (maralixibat) oral solution and LIVMARLI^® (maralixibat) tablets

LIVMARLI® (maralixibat) is an orally administered, ileal bile acid transporter (IBAT) inhibitor approved by the U.S. Food and Drug Administration for two pediatric cholestatic liver diseases. It is approved for the treatment of cholestatic pruritus in patients with Alagille syndrome (ALGS) in the U.S. three months of age and older and in Europe for patients two months of age and older. It is also approved in the U.S. for the treatment of cholestatic pruritus in patients with progressive familial intrahepatic cholestasis (PFIC) 12 months of age and older and in Europe for the treatment of PFIC in patients three months of age and older. For more information for U.S. residents, please visit LIVMARLI.com.

LIVMARLI has received Breakthrough Therapy designation for ALGS and PFIC type 2 and orphan designation for the treatment of ALGS and PFIC. LIVMARLI is currently being evaluated in the Phase 3 EXPAND study in additional settings of cholestatic pruritus. To learn more about ongoing clinical trials with LIVMARLI, please visit Mirum’s clinical trials section on the company’s website.

IMPORTANT SAFETY INFORMATION

Limitation of Use: LIVMARLI is not for use in PFIC type 2 patients who have a severe defect in the bile salt export pump (BSEP) protein.

LIVMARLI can cause side effects, including:

Liver injury. Changes in certain liver tests are common in patients with ALGS and PFIC but can worsen during treatment. These changes may be a sign of liver injury. In PFIC, this can be serious or may lead to liver transplant or death. Your healthcare provider should do blood tests and physical exams before starting and during treatment to check your liver function. Tell your healthcare provider right away if you get any signs or symptoms of liver problems, including nausea or vomiting, skin or the white part of the eye turns yellow, dark or brown urine, pain on the right side of the stomach (abdomen), bloating in your stomach area, loss of appetite or bleeding or bruising more easily than normal.

Stomach and intestinal (gastrointestinal) problems. LIVMARLI can cause stomach and intestinal problems, including diarrhea and stomach pain. Your healthcare provider may advise you to monitor for new or worsening stomach problems including stomach pain, diarrhea, blood in your stool or vomiting. Tell your healthcare provider right away if you have any of these symptoms more often or more severely than normal for you.

A condition called Fat Soluble Vitamin (FSV) Deficiency caused by low levels of certain vitamins (vitamin A, D, E, and K) stored in body fat is common in patients with ALGS and PFIC but may worsen during treatment. Your healthcare provider should do blood tests before starting and during treatment and may monitor for bone fractures and bleeding which have been reported as common side effects.

US Prescribing Information
EU SmPC
Canadian Product Monograph

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, LIVMARLI^® (maralixibat) efficacy in additional patients living with cholestatic pruritus, Mirum’s leadership in rare disease, expectations regarding LIVMARLI^® (maralixibat) ongoing development, including the potential completion of and successful results from the EXPAND trial, the anticipated timing for data from the EXPAND study, and any potential regulatory submission. 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 associated with evaluating companies and assets for acquisition, including that the perceived benefits of the acquisition are not realized; 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, 2024, filed with the Securities and Exchange Commission on February 26, 2025, 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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Investor Contact:

Andrew McKibben

ir@mirumpharma.com

Media Contact:

Meredith Kiernan

Media@mirumpharma.com

Source: Mirum Pharmaceuticals, Inc.