UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 14, 2020

Mirum Pharmaceuticals, Inc.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (650) 667-4085

(Former name or former address, if changed since last report.)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b–2 of the Securities Exchange Act of 1934 (§ 240.12b–2 of this chapter).

Emerging growth company  ☒

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.  ☒

On December 14, 2020, Mirum Pharmaceuticals, Inc. (the “Company”) entered into an underwriting agreement (the “Underwriting Agreement”) with J.P. Morgan Securities LLC, SVB Leerink LLC and Evercore Group L.L.C., as representatives of the several underwriters named therein (collectively, the “Underwriters”), relating to the issuance and sale in a public offering of 3,750,000 shares of the Company’s common stock, par value $0.0001 per share (the “Common Stock”). The price to the public in the offering was $20.00 per share. The gross proceeds to the Company from the offering are expected to be $75.0 million, before deducting underwriting discounts and commissions and estimated offering expenses payable by the Company. The closing of the offering is expected to occur on December 17, 2020, subject to the satisfaction of customary closing conditions. In addition, the Company granted the Underwriters an option, exercisable for 30 days, to purchase up to 562,500 additional shares of Common Stock at the public offering price, less the underwriting discounts and commissions.

The Underwriting Agreement contains customary representations, warranties and agreements by the Company, customary conditions to closing, indemnification obligations of the Company and the Underwriters, including for liabilities under the Securities Act of 1933, as amended, other obligations of the parties and termination provisions. The representations, warranties and covenants contained in the Underwriting Agreement were made only for purposes of such agreement and as of specific dates, were solely for the benefit of the parties to such agreement and may be subject to limitations agreed upon by such parties.

The offering is being made pursuant to an effective registration statement on Form S-3 and accompanying prospectus (File No. 333-240290), previously filed with the Securities and Exchange Commission (the “SEC”), and a prospectus supplement thereunder. A copy of the Underwriting Agreement is filed as Exhibit 1.1 to this report, and the foregoing description of the terms of the Underwriting Agreement does not purport to be complete and is qualified in its entirety by reference to such exhibit. A copy of the opinion of Cooley LLP relating to the legality of the issuance and sale of the shares in the offering is attached as Exhibit 5.1 hereto.

Forward-Looking Statements

Certain statements contained in this report are forward-looking statements that involve a number of risks and uncertainties. Such forward-looking statements include, without limitation, statements about the Company’s expectations with respect to the completion of the offering and the expected gross proceeds from the offering. Words such as “will”, “expect”, “may,” “goal,” “potential” and similar expressions are intended to identify forward-looking statements, though not all forward-looking statements necessarily contain these identifying words. For such statements, the Company claims the protection of the Private Securities Litigation Reform Act of 1995. Actual events or results may differ materially from the Company’s expectations. Factors that could cause actual results to differ materially from the forward-looking statements include, but are not limited to, risks and uncertainties associated with market conditions, the satisfaction of customary closing conditions related to the offering and the COVID-19 global pandemic. Additional factors that could cause actual results to differ materially from those stated or implied by the Company’s forward-looking statements are disclosed in the Company’s filings with the SEC, including in the section captioned “Risk Factors” in the Company’s quarterly report on Form 10-Q for the quarterly period ended September 30, 2020 and the prospectus supplement relating to the offering. These forward-looking statements represent the Company’s judgment as of the time of this report. The Company disclaims any intent or obligation to update these forward-looking statements, other than as may be required under applicable law.

(d) Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.