SCHEDULE 13D/A 0001193125-19-204056 0001720320 XXXXXXXX LIVE 6 Common Stock, par value $0.0001 per share 08/18/2025 false 0001759425 604749101 MIRUM PHARMACEUTICALS, INC.

989 E Hillsdale Blvd., Suite 300 FOSTER CITY CA 94404

Steve R. Bailey (206) 621-7200 601 Union Street, Suite 3200 Seattle WA 98101 0001720320 N Frazier Life Sciences IX, L.P. b WC N DE 0.00 3566912.00 0.00 3566912.00 3566912.00 N 7.1 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001782789 N FHMLS IX, L.P. b AF N DE 0.00 3566912.00 0.00 3566912.00 3566912.00 N 7.1 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001782791 N FHMLS IX, L.L.C. b AF N DE 0.00 3566912.00 0.00 3566912.00 3566912.00 N 7.1 OO The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001790879 N Frazier Life Sciences X, L.P. b WC N DE 0.00 168308.00 0.00 168308.00 168308.00 N 0.3 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001790880 N FHMLS X, L.P. b AF N DE 0.00 168308.00 0.00 168308.00 168308.00 N 0.3 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001790811 N FHMLS X, L.L.C. b AF N DE 0.00 168308.00 0.00 168308.00 168308.00 N 0.3 OO The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001863769 N Frazier Life Sciences Public Fund, L.P. b WC N DE 0.00 1574374.00 0.00 1574374.00 1574374.00 N 3.1 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001879466 N FHMLSP, L.P. b AF N DE 0.00 1574374.00 0.00 1574374.00 1574374.00 N 3.1 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001879465 N FHMLSP, L.L.C. b AF N DE 0.00 1574374.00 0.00 1574374.00 1574374.00 N 3.1 OO The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001913804 N Frazier Life Sciences Public Overage Fund, L.P. b WC N DE 0.00 940573.00 0.00 940573.00 940573.00 N 1.9 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001963247 N FHMLSP Overage, L.P. b AF N DE 0.00 940573.00 0.00 940573.00 940573.00 N 1.9 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001963248 N FHMLSP Overage, L.L.C. b AF N DE 0.00 940573.00 0.00 940573.00 940573.00 N 1.9 OO The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001911592 N Frazier Life Sciences XI, L.P. b WC N DE 0.00 544954.00 0.00 544954.00 544954.00 N 1.1 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001911580 N FHMLS XI, L.P. b AF N DE 0.00 544954.00 0.00 544954.00 544954.00 N 1.1 PN The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001911623 N FHMLS XI, L.L.C. b AF N DE 0.00 544954.00 0.00 544954.00 544954.00 N 1.1 OO The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001341382 N James N. Topper b AF N X1 0.00 3735220.00 0.00 3735220.00 3735220.00 N 7.4 IN The Aggregate Amount represents (i) 3,566,912 shares of Common Stock held directly by Frazier Life Sciences IX, L.P., and (ii) 163,643 shares of Common Stock held directly by Frazier Life Sciences X, L.P. The Percent of Class is calculated based on 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025. 0001365617 N Patrick J. Heron b AF N X1 82482.00 3735220.00 82482.00 3735220.00 3735220.00 N 7.6 IN The Aggregate Amount represents (i) 5,703 shares of Common Stock held directly by the Reporting Person, (ii) 76,779 shares of Common Stock that are issuable upon the exercise of options held directly by the Reporting Person, (iii) 3,566,912 shares of Common Stock held directly by Frazier Life Sciences IX, L.P., and (iv) 163,643 shares of Common Stock held directly by Frazier Life Sciences X, L.P. The Percent of Class is calculated based on (i) 50,237,647 shares of Common Stock outstanding on August 1, 2025 as set forth in the Issuer's Quarterly Report on Form 10-Q filed with the SEC on August 6, 2025 and (ii) 76,779 shares of Common Stock that are issuable upon the exercise of options held directly by the Reporting Person. 0001397906 N Albert Cha b AF N X1 0.00 0.00 0.00 0.00 0.00 N 0.0 IN 0001865123 N James Brush b AF N X1 0.00 0.00 0.00 0.00 0.00 N 0.0 IN 0001702527 N Daniel Estes b AF N X1 0.00 0.00 0.00 0.00 0.00 N 0.0 IN Common Stock, par value $0.0001 per share MIRUM PHARMACEUTICALS, INC. 989 E Hillsdale Blvd., Suite 300 FOSTER CITY CA 94404 This Amendment No. 6 ("Amendment No. 6") to Schedule 13D amends the statement on Schedule 13D filed on July 26 2019 (the "Original Schedule 13D") as amended on April 29, 2020, December 18, 2020, August 16, 2022, April 14, 2023 and September 5, 2023 (the "Prior Amendments", and together with the Original Schedule 13D and this Amendment No. 6, the "Schedule 13D"). Except as otherwise specified in this Amendment No. 6, all items in the Original Schedule 13D, as amended by the Prior Amendments, are unchanged. All capitalized terms used in this Amendment No. 6 and not otherwise defined herein have the meanings ascribed to such terms in the Original Schedule 13D, as amended by the Prior Amendments. The information contained in Rows 7, 8, 9, 10, 11, and 13 of each Reporting Person's cover page to this Schedule 13D (including the footnotes thereto) is incorporated by reference into this Item 5. FLSPF directly holds 1,574,374 shares of Common Stock of the Issuer (the "FLSPF Shares"). FHMLSP, L.P. is the general partner of FLSPF and the general partner of FHMLSP, L.P. is FHMLSP, L.L.C., which is managed by an investment committee of four that acts by majority vote. Accordingly, no members of such committee are attributed beneficial ownership of the securities directly held by FLSPF, and this Schedule 13D corrects any previous attribution to, and overstatement of beneficial ownership by, such members as reflected in any prior Statements. FLSPOF directly holds 940,573 shares of Common Stock of the Issuer (the "FLSPOF Shares"). FHMLSP Overage, L.P. is the general partner of FLSPOF and the general partner of FHMLSP Overage, L.P. is FHMLSP Overage, L.L.C., which is managed by an investment committee of four that acts by majority vote. Accordingly, no members of such committee are attributed beneficial ownership of the securities directly held by FLSPOF, and this Schedule 13D corrects any previous attribution to, and overstatement of beneficial ownership by, such members as reflected in any prior Statements. FLS IX directly holds 3,566,912 shares of Common Stock of the Issuer (the "FLS IX Shares"). FHMLS IX, L.P. is the general partner of FLS IX and FHMLS IX, L.L.C. is the general partner of FHMLS IX, L.P. Heron and Topper are the members of FHMLS IX, L.L.C. and therefore share voting and investment power over the FLS IX Shares. FLS X directly holds 168,308 shares of Common Stock of the Issuer (the "FLS X Shares"). FHMLS X, L.P. is the general partner of FLS X and FHMLS X, L.L.C. is the general partner of FHMLS X, L.P. Heron and Topper are the members of FHMLS X, L.L.C. and therefore share voting and investment power over the FLS X Shares. FLS XI directly holds 544,954 shares of Common Stock of the Issuer (the "FLS XI Shares"). FHMLS XI, L.P. is the general partner of FLS XI and the general partner of FHMLS XI, L.P. is FHMLS XI, L.L.C., which is managed by an investment committee of three that acts by majority vote. Accordingly, no members of such committee are attributed beneficial ownership of the securities directly held by FLS XI, and this Schedule 13D corrects any previous attribution to, and overstatement of beneficial ownership by, such members as reflected in any prior Statements. Except as specifically stated herein, the filing of this Schedule 13D shall not be construed as an admission that any Reporting Person or any of the foregoing is, for the purposes of Section 13(d) and/or Section 13(g) of the Act or otherwise, the beneficial owner of any securities covered by this Schedule 13D or a member of a "group" with any other person. Exhibit 99.1 Joint Filing Agreement (incorporated by reference to Exhibit A to Schedule 13D/A filed on September 5, 2023) Frazier Life Sciences IX, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLS IX, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLS IX, L.L.C. /s/ Steve R. Bailey 08/20/2025 Frazier Life Sciences X, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLS X, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLS X, L.L.C. /s/ Steve R. Bailey 08/20/2025 Frazier Life Sciences Public Fund, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLSP, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLSP, L.L.C. /s/ Steve R. Bailey 08/20/2025 Frazier Life Sciences Public Overage Fund, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLSP Overage, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLSP Overage, L.L.C. /s/ Steve R. Bailey 08/20/2025 Frazier Life Sciences XI, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLS XI, L.P. /s/ Steve R. Bailey 08/20/2025 FHMLS XI, L.L.C. /s/ Steve R. Bailey 08/20/2025 James N. Topper /s/ Steve R. Bailey 08/20/2025 Patrick J. Heron /s/ Steve R. Bailey 03/06/2025 Albert Cha /s/ Steve R. Bailey 08/20/2025 James Brush /s/ Steve R. Bailey 08/20/2025 Daniel Estes /s/ Steve R. Bailey 08/20/2025