Mirum Pharmaceuticals Announces Enrollment Completion in Phase 2b EMBARK Biliary Atresia Study

• Topline data are expected in second half of 2023.
• EMBARK will be the first completed randomized study of an IBAT inhibitor for the treatment of biliary atresia.

Mirum Pharmaceuticals, Inc. (Nasdaq: MIRM) today announced it has completed enrollment of its Phase 2b EMBARK study for pediatric patients with biliary atresia, the most common indication for pediatric liver transplant. The EMBARK study is a global, double-blind, randomized, placebo-controlled, 26-week trial evaluating the efficacy and safety of LIVMARLI® (maralixibat) oral solution in infants with biliary atresia who have previously undergone a hepatoportoenterostomy (HPE), more commonly known as a Kasai procedure. Topline results are expected to be announced in the second half of 2023.

“We are pleased to have fully enrolled our EMBARK study with LIVMARLI as there is an urgent need for new therapies in biliary atresia. We are looking forward to reporting topline data later this year,” said Lara Longpre, chief development officer at Mirum. “Further, these topline data will represent the first randomized data showing the effects of IBAT inhibition in patients with biliary atresia and an important step forward for a potential new treatment for patients in this difficult setting.”

About the EMBARK Study

The Phase 2 EMBARK study is evaluating LIVMARLI® (maralixibat) oral solution in patients with biliary atresia following a hepatoportoenterostomy (HPE), or Kasai procedure. EMBARK is a double-blind, placebo-controlled study assessing changes in total bilirubin and serum bile acids, both of which are leading indicators of efficacy on key markers of disease progression. Secondary endpoints also include bilirubin normalization, biomarkers of liver injury and safety. Following the 26-week placebo-controlled portion of the study, a long-term open label period will commence during which all patients will receive LIVMARLI up to Week 104.

About Biliary Atresia

Biliary atresia (BA) is a rare liver disorder in which there is a blockage or absence of large bile ducts that lead to bile accumulation in the liver and ultimately results in progressive cholestasis and liver damage. BA occurs in infants and is estimated to affect one in every 10,000-15,000 live births in the United States. While the underlying causes of BA are not completely understood, BA may occur in some patients due to a malformation of bile ducts during fetal development, and in others, inflammation around the time of birth may lead to the distribution of bile ducts. As a result of BA, bile acids are not able to adequately drain the liver. The rapid progression of BA necessitates surgical intervention within the first months of life. Biliary atresia is the most common reason for liver transplants in children.

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) three months of age and older and is the only FDA-approved medication to treat cholestatic pruritus associated with Alagille syndrome. LIVMARLI is also approved in Europe for the treatment of cholestatic pruritus in patients with ALGS two months of age and older. For more information, please visit LIVMARLI.com.

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

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, Mirum’s plans with respect to its clinical programs and the potential regulatory approval process of LIVMARLI in biliary atresia and LIVMARLI’s potential effect on patients with biliary atresia when optimally dosed. 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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