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( Mark One ) ANNUAL REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31 , 2020 OR TRANSITION REPORT PURSUANT TO SECTION 13 OR 15 ( d ) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM ΤΟ UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington , D.C. 20549 FORM 10 - K Delaware ( State or other jurisdiction of incorporation or organization ) 950 Tower Lane , Suite 1050 , Foster City , California ( Address of principal executive offices ) Commission File Number 001-38981 Mirum Pharmaceuticals , Inc. ( Exact name of Registrant as specified in its Charter ) Securities registered pursuant to Section 12 ( b ) of the Act : Title of each class Common stock , par value $ 0.0001 per share Large accelerated filer Non - accelerated filer ing growth company Registrant's telephone number , including area code : ( 650 ) 667-4085 83-1281555 ( I.R.S. Employer Identification No. ) 94404 ( Zip Code ) Trading Symbol ( s ) MIRM Securities registered pursuant to Section 12 ( g ) of the Act : None Indicate by check mark if the Registrant is a well - known seasoned issuer , as defined in Rule 405 of the Securities Act . YES NO Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15 ( d ) of the Act . YES NO Indicate by check mark whether the Registrant : ( 1 ) has filed all reports required to be filed by Section 13 or 15 ( d ) of the Securities Exchange Act of 1934 during the preceding 12 months ( or for such shorter period that the Registrant was required to file such reports ) , and ( 2 ) has been subject to such filing requirements for the past 90 days . YES NO Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S - T ( §232.405 of this chapter ) during the preceding 12 months ( or for such shorter period that the Registrant was required to submit such files ) . YES NO Name of each exchange on which registered Nasdaq Global Market Indicate by check mark whether the registrant is a large accelerated filer , an accelerated filer , a non - accelerated filer , smaller reporting company , or an emerging growth company . See the definitions of “ large accelerated filer , ” “ accelerated filer , ” “ smaller reporting company , ” and “ emerging growth company " in Rule 12b - 2 of the Exchange Act . X Accelerated filer Smaller reporting company П If an emerging growth company , indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13 ( a ) of the Exchange Act . Indicate by check mark whether the registrant has filed a report on and attestation to its management's assessment of the effectiveness of its internal control over financial reporting under Section 404 ( b ) of the Sarbanes - Oxley Act ( 15 U.S.C. 7262 ( b ) ) by the registered public accounting firm that prepared or issued its audit report . Indicate by check mark whether the Registrant is a shell company ( as defined in Rule 12b - 2 of the Exchange Act ) . YES NO The aggregate market value of the Registrant's common stock held by non - affiliates of the Registrant as of June 30 , 2020 , the last business day of the Registrant's most recently completed second fiscal quarter , was approximately $ 243.5 million , based on the closing price of the Registrant's common stock on the Nasdaq Global Market of $ 19.46 per share . The number of shares of Registrant's common stock , par value $ 0.0001 per share , outstanding as of March 5,2021 was 30,419,707 . DOCUMENTS INCORPORATED BY REFERENCE Portions of the Registrant's definitive proxy statement for its 2021 Annual Meeting of Stockholders , which the Registrant intends to file pursuant to Regulation 14A with the Securities and Exchange Commission not later than 120 days after the Registrant's fiscal year ended December 31 , 2020 , are incorporated by reference into Part III of this Annual Report on Form 10 - K .