SC 13D/A #1

Number of

Shares

Beneficially

Owned by

Each

Reporting

Person

With:

Sole Voting Power

0 shares

Shared Voting Power

3,566,912 shares (1)

Sole Dispositive Power

0 shares

Shared Dispositive Power

3,566,912 shares (1)

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

SCHEDULE 13D

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)*

Mirum Pharmaceuticals, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

604749 101

(CUSIP Number)

Steve R. Bailey

Frazier Healthcare Partners

601 Union Street, Suite 3200

Seattle, WA 98101

Telephone: (206) 621-7200

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

January 13, 2020

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box. ☐

Note: Schedules filed in paper format shall include a signed original and five copies of the schedule, including all exhibits. See §240.13d-7 for other parties to whom copies are to be sent.

*	The remainder of this cover page shall be filled out for a reporting person’s initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter disclosures provided in a prior cover page.

The information required on the remainder of this cover page shall not be deemed to be “filed” for the purpose of Section 18 of the Securities Exchange Act of 1934 (“Act”) or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

CUSIP No. 604749 101


1.		Name of Reporting Persons. Frazier Life Sciences IX, L.P.
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a) ☐ (b) ☒
3.		SEC USE ONLY
4.		Source of Funds (See Instructions) WC
5.		Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ☐
6.		Citizenship or Place of Organization Delaware

(1)

Consists of 3,566,912 shares of Common Stock held directly by Frazier Life Sciences IX, L.P. FHMLS IX, L.P. is the general partner of Frazier Life Sciences IX, L.P. and FHMLS IX, L.L.C. is the general partner of FHMLS IX, L.P. Patrick Heron and James Topper are the members of FHMLS IX, L.L.C. and therefore share voting and investment power over the shares held by Frazier Life Sciences IX, L.P.

(2)

Based on 25,389,978 shares of Common Stock that were anticipated to be outstanding following the Issuer’s public offering (and excluding the underwriters’ option to purchase an additional 360,000 shares of the Issuer’s Common Stock in such public offering) as set forth in the Issuer’s final prospectus filed with the SEC pursuant to Rule 424(b)(4) on January 9, 2020.

CUSIP No. 604749 101


1.		Name of Reporting Persons. FHMLS IX, L.P.
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a) ☐ (b) ☒
3.		SEC USE ONLY
4.		Source of Funds (See Instructions) AF
5.		Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ☐
6.		Citizenship or Place of Organization Delaware

(1)

(2)

CUSIP No. 604749 101


1.		Name of Reporting Persons. FHMLS IX, L.L.C.
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a) ☐ (b) ☒
3.		SEC USE ONLY
4.		Source of Funds (See Instructions) AF
5.		Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ☐
6.		Citizenship or Place of Organization Delaware

(1)

(2)

CUSIP No. 604749 101


1.		Name of Reporting Persons. James Topper
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a) ☐ (b) ☒
3.		SEC USE ONLY
4.		Source of Funds (See Instructions) AF
5.		Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ☐
6.		Citizenship or Place of Organization United States Citizen

(1)

(2)

CUSIP No. 604749 101


1.		Name of Reporting Persons. Patrick Heron
2.		Check the Appropriate Box if a Member of a Group (See Instructions) (a) ☐ (b) ☒
3.		SEC USE ONLY
4.		Source of Funds (See Instructions) AF
5.		Check if Disclosure of Legal Proceedings Is Required Pursuant to Items 2(d) or 2(e) ☐
6.		Citizenship or Place of Organization United States Citizen

(1)

(2)

CUSIP No. 604749 101

Item 1.

Security and Issuer.

This Amendment No. 1 (“Amendment No. 1”) to Schedule 13D amends the statement on Schedule 13D filed on July 26 2019 (the “Original Schedule 13D” and together with this Amendment No. 1, the “Schedule 13D”) with respect to the Common Stock of Mirum Pharmaceuticals, Inc. (the “Issuer”), having its principal executive office at 950 Tower Lane, Suite 1050, Foster City, California 94404. Except as otherwise specified in Amendment No. 1, all items in the Schedule 13D are unchanged. All capitalized terms used in this Amendment No. 1 and not otherwise defined herein have the meanings ascribed to such terms in the Original Schedule 13D.

The Reporting Persons are filing this Amendment No. 1 to report a decrease in the percentage of the class beneficially owned by the Reporting Persons due to an increase in the aggregate number of outstanding securities of the Issuer.

Item 5.

Interest in Securities of the Issuer

(a)

FLS IX is the record owners of the FLS Shares. As the sole general partner of FLS IX, FHMLS IX, L.P. may be deemed to beneficially own the FLS Shares. As the sole general partner of FHMLS IX, L.P., FHMLS IX, L.L.C. may be deemed to beneficially own the FLS Shares. As members of FHMLS IX, L.L.C., each of the Members may be deemed to beneficially own the FLS Shares.

The percentage of outstanding Common Stock of the Issuer, which may be deemed to be beneficially owned by each Reporting Person, is set forth on Line 13 of such Reporting Person’s cover sheet. Such percentage was calculated based on the 25,389,978 shares of Common Stock that were anticipated to be outstanding following the Issuer’s public offering (and excluding the underwriters’ option to purchase an additional 360,000 shares of the Issuer’s Common Stock in such public offering) as set forth in the Issuer’s final prospectus filed with the SEC pursuant to Rule 424(b)(4) on January 9, 2020.

(b)

Regarding the number of shares as to which such person has:

Sole power to vote or to direct the vote: See line 7 of cover sheets.

Shared power to vote or to direct the vote: See line 8 of cover sheets.

Sole power to dispose or to direct the disposition: See line 9 of cover sheets.

Shared power to dispose or to direct the disposition: See line 10 of cover sheets.

(c)

Not applicable.

(d)

No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, the FLS Shares beneficially owned by any of the Reporting Persons.

(e)	Not applicable.

SIGNATURES

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.


Date: April 28, 2020	FRAZIER LIFE SCIENCES IX, L.P.
	By FHMLS IX, L.P., its general partner
	By FHMLS IX, L.L.C., its general partner

	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer

Date: April 28, 2020	FHMLS IX, L.P.
	By FHMLS IX, L.L.C., its general partner

	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer

Date: April 28, 2020	FHMLS IX, L.L.C.

	By:	/s/ Steve R. Bailey
		Steve R. Bailey, Chief Financial Officer

Date: April 28, 2020	By:	*
		James Topper

Date: April 28, 2020	By:	*
		Patrick Heron

Date: April 28, 2020	*By:	/s/ Steve R. Bailey
		Steve R. Bailey, as Attorney-in-Fact

This Schedule 13D was executed by Steve R. Bailey on behalf of the individuals listed above pursuant to a Power of Attorney, a copy of which was filed with the SEC on July 31, 2017.