Organization and Description of Business	12 Months Ended
Dec. 31, 2021
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Organization and Description of Business	1. Organization and Description of Business Mirum Pharmaceuticals, Inc. (the “Company”) was incorporated in the State of Delaware on May 2, 2018, and is headquartered in Foster City, California. The Company is a biopharmaceutical company focused on the identification, acquisition, development and commercialization of novel therapies for debilitating rare diseases. The Company received U.S. Food and Drug Administration (“FDA”) approval for LIVMARLI® (maralixibat) oral solution (“Livmarli”), the first and only FDA-approved medication for the treatment of cholestatic pruritus in patients with Alagille syndrome (“ALGS”) one year of age and older, on September 29, 2021. The Company’s development pipeline consists of two clinical-stage product candidates, Livmarli and volixibat. The Company commenced significant operations in November 2018. The Company views its operations and manages its business as one operating segment. Liquidity The Company has a limited operating history, has incurred significant operating losses since its inception, and the revenue and income potential of the Company’s business and market are unproven. As of December 31, 2021, the Company had an accumulated deficit of $257.2 million and cash, cash equivalents, restricted cash equivalents and investments of $261.5 million. The Company believes that its unrestricted cash, cash equivalents and investments of $161.5 million as of December 31, 2021, provide sufficient capital resources to continue its operations for at least twelve months from the issuance date of the accompanying consolidated financial statements. The consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. The consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development activities. In December 2021, the Company completed the sale of the Rare Pediatric Disease Priority Review Voucher (“PRV”), for net proceeds of $108.0 million, after deducting commission costs. In addition, in January and February 2022, the Company sold 992,389 shares of common stock in an at-the-market offering pursuant to a Sales Agreement entered into with SVB Leerink LLC in August 2020, at a weighted-average price of $18.04 per share, resulting in net proceeds of $17.4 million.

Organization and Description of Business

12 Months Ended

Dec. 31, 2021

Organization Consolidation And Presentation Of Financial Statements [Abstract]

Organization and Description of Business

1. Organization and Description of Business

Mirum Pharmaceuticals, Inc. (the “Company”) was incorporated in the State of Delaware on May 2, 2018, and is headquartered in Foster City, California. The Company is a biopharmaceutical company focused on the identification, acquisition, development and commercialization of novel therapies for debilitating rare diseases.

The Company received U.S. Food and Drug Administration (“FDA”) approval for LIVMARLI® (maralixibat) oral solution (“Livmarli”), the first and only FDA-approved medication for the treatment of cholestatic pruritus in patients with Alagille syndrome (“ALGS”) one year of age and older, on September 29, 2021.

The Company’s development pipeline consists of two clinical-stage product candidates, Livmarli and volixibat. The Company commenced significant operations in November 2018.

The Company views its operations and manages its business as one operating segment.

Liquidity

The Company has a limited operating history, has incurred significant operating losses since its inception, and the revenue and income potential of the Company’s business and market are unproven. As of December 31, 2021, the Company had an accumulated deficit of $257.2 million and cash, cash equivalents, restricted cash equivalents and investments of $261.5 million. The Company believes that its unrestricted cash, cash equivalents and investments of $161.5 million as of December 31, 2021, provide sufficient capital resources to continue its operations for at least twelve months from the issuance date of the accompanying consolidated financial statements. The consolidated financial statements have been prepared on a going concern basis, which contemplates the realization of assets and satisfaction of liabilities in the normal course of business. The consolidated financial statements do not include any adjustments relating to the recoverability and classification of recorded asset amounts or the amounts and classification of liabilities that might result from the outcome of this uncertainty. Management expects to continue to incur additional substantial losses in the foreseeable future as a result of the Company’s research and development activities.

In December 2021, the Company completed the sale of the Rare Pediatric Disease Priority Review Voucher (“PRV”), for net proceeds of $108.0 million, after deducting commission costs. In addition, in January and February 2022, the Company sold 992,389 shares of common stock in an at-the-market offering pursuant to a Sales Agreement entered into with SVB Leerink LLC in August 2020, at a weighted-average price of $18.04 per share, resulting in net proceeds of $17.4 million.