• Seven oral and poster presentations highlighted during meeting

• Phase 3 MARCH PFIC data selected as one of highest scoring abstracts and presented during the plenary session

• RISE study evaluating LIVMARLI in infants with ALGS and PFIC included among highest scoring posters

Mirum Pharmaceuticals, Inc. (Nasdaq: MIRM) today announced data presented during the 55^th European Society for Pediatric, Gastroenterology, Hepatology, and Nutrition (ESPGHAN) Annual Meeting. Among the data presented were four oral and three poster presentations featuring analyses from LIVMARLI® (maralixibat) oral solution clinical studies.

“We are thrilled to present data further underscoring LIVMARLI’s potential to help patients with ALGS and PFIC, two debilitating cholestatic diseases affecting children,” said Pam Vig, PhD, head of research and development at Mirum. “Further analyses from the MARCH-PFIC study continue to highlight LIVMARLI’s potential to benefit patients across a broad range of PFIC types. In ALGS, the data continue to support LIVMARLI’s safety and efficacy profile, including in infants under 12 months of age as well as in the real-world setting. We are proud to present data across multiple parameters, including improvements in pruritus, serum bile acids, and also in xanthomas which can be painful, disfiguring and debilitating for many patients.”

A summary of data from the oral presentations at ESPGHAN, featuring LIVMARLI, are enclosed:

Abstract 477 – H-O027: Efficacy and safety of maralixibat in patients with progressive familial intrahepatic cholestasis (MARCH-PFIC): A randomized placebo-controlled Phase 3 study

Thursday, May 18, 2023 - 11:45am-1:15pm CET - Plenary Session, Highest Scoring Abstracts, Hall A

Presented at 1:02pm CET by Professor Richard J. Thompson, King’s College, London

The MARCH-PFIC study is the largest Phase 3 trial conducted in children with PFIC including PFIC types that had not been previously studied. The data showed that the primary and secondary endpoints were met with LIVMARLI demonstrating significant and rapid improvements in pruritus and serum bile acids (sBAs) across all PFIC types. Data from the All-PFIC cohort showed significant improvements in bilirubin and weight z-scores as well as a trend in height z-score improvement. No new safety signals were observed.

Abstract 468- H-O029: Maralixibat improves cholestatic pruritus and bile acids in children with FIC1: Data from the MARCH-PFIC trial

Friday, May 19, 2023 - 12:00-1:00pm CET - Parallel Session: Hepatology-Abstract Session 02, Hall G

Presented at 12:00pm CET by Professor Richard J. Thompson, King’s College, London

The analysis evaluated LIVMARLI’s benefit in patients with FIC1 (n=13), assessing improvements in pruritus and serum bile acids. Data showed that patients treated with LIVMARLI experienced improvements in pruritus (p=0.0186) and a greater proportion of LIVMARLI-treated patients met the clinically meaningful improvement criteria for pruritus. Additionally, the data demonstrated statistically significant improvements in sBA levels (p=0.0305). Treatment with LIVMARLI in patients with FIC1 also showed numerical improvements in total and direct bilirubin. No new safety signals were observed.

Abstract 472 – H-O010: Maralixibat improves xanthomas and hypercholesterolemia in children with Alagille syndrome: an integrated analysis from two clinical trials

Friday, May 19, 2023 - 12:00-1:00pm CET - Parallel Session: Hepatology-Abstract Session 02, Hall G

Presented at 12:36pm CET by Dr. Brett Hoskins, The Johns Hopkins Hospital School of Medicine, Baltimore, Maryland

Xanthomas are known to be a burdensome, debilitating, and disfiguring symptom of Alagille syndrome, occurring in 24-42% of these patients. They are thought to be caused by impaired bile acid excretion from the liver, resulting from an accumulation of precursors in bile acid synthesis like cholesterol. They can also be an indication for liver transplant in approximately half of liver transplant recipients with ALGS. IBAT inhibition associated with LIVMARLI has been shown to pharmacologically reduce serum bile acid levels, which could impact the presence of xanthomas and cholesterol. The analysis evaluated the impact of LIVMARLI on xanthomas using data from ALGS studies. Xanthoma responders were defined as an individual who dropped their Clinician Xanthoma Score (CXS) by ≥1 point from baseline (on a scale of 0-4 with 0 being no evidence of xanthomas and 4 being disabling (causing interference with function because of excess size or number). Consistent with its mechanism of action, LIVMARLI was shown to reduce xanthomas, hypercholesterolemia, and sBAs. The analysis also concluded that earlier treatment may help prevent the development of severe xanthomas.

Abstract 463 – H-O008: Real-world safety experience in patients with Alagille syndrome treated with maralixibat

Friday, May 19, 2023 – 12:00-1:00pm CET - Parallel Session: Hepatology-Abstracts 02, Hall G

Presented at 12:45pm CET by Dr. Regino P. Gonzalez-Peralta, AdventHealth for Children and AdventHealth Transplant Institute, Orlando, Florida

The analysis evaluated real-world safety observations for patients with ALGS who were treated with LIVMARLI while enrolled in the expanded access program. The data showed that LIVMARLI was well-tolerated in a real-world setting with lower rates of adverse events than described in clinical trials. There were no serious adverse events related to the use of LIVMARLI and no reports of GI bleeding, fat-soluble vitamin deficiency events or fractures. Treatment-related GI adverse events were mild and observed in only three patients; there were no discontinuations due to GI adverse events.

Mirum also had data presented in three poster sessions. The full oral presentations and posters can be found within the Publications and Presentations section on Mirum’s website.

About LIVMARLI® (maralixibat) oral solution

LIVMARLI® (maralixibat) oral solution is an orally administered, once-daily, ileal bile acid transporter (IBAT) inhibitor approved by the U.S. Food and Drug Administration for the treatment of cholestatic pruritus in patients with Alagille syndrome (ALGS) 3 months of age and older. LIVMARLI is also approved by the European Commission for the treatment of cholestatic pruritus in patients with ALGS two months and older. It is the only approved medication to treat cholestatic pruritus associated with Alagille syndrome. For more information for U.S. residents, please visit LIVMARLI.com.

Mirum has also submitted LIVMARLI for approval in the U.S. (in cholestatic pruritus in PFIC patients three months of age and older) and in Europe (in PFIC for patients two months of age and older).

LIVMARLI is currently being evaluated in late-stage clinical studies in other rare cholestatic liver diseases including biliary atresia. LIVMARLI has received Breakthrough Therapy designation for ALGS and PFIC type 2 and orphan designation for ALGS, PFIC and biliary atresia. To learn more about ongoing clinical trials with LIVMARLI, please visit Mirum’s clinical trials section on the company’s website.

IMPORTANT SAFETY INFORMATION

LIVMARLI can cause side effects, including:

Changes in liver tests. Changes in certain liver tests are common in patients with Alagille syndrome and can worsen during treatment with LIVMARLI. These changes may be a sign of liver injury and can be serious. Your healthcare provider should do blood tests 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) or loss of appetite.

Stomach and intestinal (gastrointestinal) problems. LIVMARLI can cause stomach and intestinal problems, including diarrhea, stomach pain, and vomiting during treatment. 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. FSV deficiency is common in patients with Alagille syndrome but may worsen during treatment. Your healthcare provider should do blood tests before starting and during treatment.

Other common side effects reported during treatment were gastrointestinal bleeding and bone fractures.

US Prescribing Information

EU SmPC

About Mirum Pharmaceuticals, Inc.

Mirum Pharmaceuticals, Inc. is a biopharmaceutical company dedicated to transforming the treatment of rare liver diseases. Mirum’s approved medication is LIVMARLI^® (maralixibat) oral solution which is approved in the U.S. for the treatment of cholestatic pruritus in patients with Alagille syndrome three months of age and older, and in Europe for the same indication in patients two months of age and older.

Mirum has also submitted LIVMARLI for approval in the U.S. (in cholestatic pruritus in PFIC patients three months of age and older) and in Europe (in PFIC for patients two months of age and older).

Mirum’s late-stage pipeline includes two investigational treatments for debilitating liver diseases affecting children and adults. LIVMARLI, an oral ileal bile acid transporter (IBAT) inhibitor, is currently being evaluated in clinical trials for pediatric liver diseases and includes the EMBARK Phase 2b clinical trial for patients with biliary atresia. In addition, Mirum has an expanded access program open across multiple countries for eligible patients with ALGS and PFIC.

Mirum’s second investigational treatment, volixibat, an oral IBAT inhibitor, is being evaluated in two potentially registrational studies including the VISTAS Phase 2b clinical trial for adults with primary sclerosing cholangitis and the VANTAGE Phase 2b clinical trial for adults with primary biliary cholangitis.

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Forward-Looking Statements

This press release includes forward-looking statements pertaining to the Company’s planned participation at a scientific conference, including data presentation title and synopsis, which may include discussion of the Company’s clinical and research data, including the discovery, development, and commercialization of our product candidates and technologies, the therapeutic potential of Company products, the continuation of our clinical trials, and any potential future collaborations. 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 “will,” “goal,” “potential” 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 associated with Mirum’s business in general, the impact of the COVID-19 pandemic, and the other risks described in Mirum’s filings with the Securities and Exchange Commission. 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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