Company: MIRM
Filing Date: 2025-08-12
Form Type: S-3ASR
Source: 0001193125-25-178937
Chunk: 36

Company: Mirum Pharmaceuticals, Inc.
Filing Date: 2025-08-12
Form: S-3ASR
Chunk 36
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 securities exchanges or 
 quotation or trading services.                                                                            |

Such at-the-marketofferings, if any, may be conducted by underwriters acting as principal or agent. A prospectus supplement or supplements (and any related free writing prospectus that we may authorize to be provided to you) will describe the terms of the offering of the securities, including, to the extent applicable:

| • |     | the name or names of any underwriters, dealers or agents, if any; |

| • |     | the purchase price of the securities and the proceeds we will receive from the sale; |

| • |     | any options pursuant to which underwriters may purchase additional securities from us; |

| • |     | any agency fees or underwriting discounts and other items constituting agents’ or underwriters’ 
 compensation;                                                                                   |

| • |     | any public offering price; |

| • |     | any discounts or concessions allowed or reallowed or paid to dealers; and |

| • |     | any securities exchange or market on which the securities may be listed. |

Only underwriters named in the prospectus supplement are underwriters of the securities offered by the prospectus supplement. If underwriters are used in the sale, they will acquire the securities for their own account and may resell the securities from time to time in one or more transactions at a fixed public offering price or at varying prices determined at the time of sale. The obligations of the underwriters to purchase the securities will be subject to the conditions set forth in the applicable underwriting agreement. We may offer the securities to the public through underwriting syndicates represented by managing underwriters or by underwriters without a syndicate. Subject to certain conditions, the underwriters will be obligated to purchase all of the securities offered by the prospectus supplement, other than securities covered by any option to purchase additional securities. Any public offering price and any discounts or concessions allowed or reallowed or paid to dealers may change from time to time. We may use underwriters with whom we have a material relationship. We will describe in the prospectus supplement, naming the underwriter, the nature of any such relationship. 29

We may sell securities directly or through agents we designate from time to time. We will
name any agent involved in the offering and sale of securities, and we will describe any commissions and other compensation we will pay the agent in the prospectus supplement. Unless the prospectus supplement states otherwise, our agent will act on
a best-efforts basis for the period of