[Form 4] Mirum Pharmaceuticals, Inc. Insider Trading Activity

Rhea-AI Filing Summary

Mirum Pharmaceuticals (MIRM) director reports option exercise and share sale. On 11/21/2025, the reporting person exercised a stock option for 50,000 shares of common stock at $2.936 per share and acquired the shares. On the same day, they sold 50,000 shares of common stock at $70 per share under a pre-arranged Rule 10b5-1 trading plan.

After these transactions, the director reported no directly held common shares, but continued to report indirect ownership of 186,410 shares through The Grey Family Trust dated November 12, 1999 and 93,750 shares through The Grey 2018 Irrevocable Children's Trust. They also reported 281,176 stock options beneficially owned following the transactions, with the option referenced in this filing fully vested and exercisable.

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

X

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

GREY MICHAEL G

(Last) (First) (Middle)

C/O MIRUM PHARMACEUTICALS, INC.

989 E HILLSDALE BLVD., SUITE 300

(Street)

FOSTER CITY CA 94404

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Mirum Pharmaceuticals, Inc. [ MIRM ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director		10% Owner
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
11/21/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	11/21/2025		M		50,000	A	$2.936	50,000	D
Common Stock	11/21/2025		S(1)		50,000	D	$70	0	D
Common Stock								186,410	I	By The Grey Family Trust dated November 12,1999
Common Stock								93,750	I	By The Grey 2018 Irrevocable Children's Trust

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Stock Option (right to buy)	$2.936	11/21/2025		M			50,000	(2)	03/11/2029	Common Stock	50,000	$0	281,176	D

Explanation of Responses:

1. Reported transaction occurred pursuant to a Rule 10b5-1 Plan adopted August 22, 2025.

2. The stock option is fully vested and exercisable.

	/s/ Judit Ryvkin, Attorney-in-Fact	11/24/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did the Mirum Pharmaceuticals (MIRM) director report?

The director reported exercising a stock option for 50,000 shares of Mirum Pharmaceuticals common stock at $2.936 per share on 11/21/2025, and selling 50,000 shares of common stock at $70 per share on the same date.

Was the Mirum (MIRM) insider trade made under a Rule 10b5-1 plan?

Yes. The filing states the reported transaction occurred pursuant to a Rule 10b5-1 Plan adopted August 22, 2025, which is a pre-arranged trading plan for insiders.

How many Mirum Pharmaceuticals (MIRM) shares does the director own after this Form 4?

After the reported transactions, the director reported 0 shares of common stock held directly, 186,410 shares held indirectly by The Grey Family Trust dated November 12, 1999, and 93,750 shares held indirectly by The Grey 2018 Irrevocable Children's Trust.

How many Mirum (MIRM) stock options does the reporting person hold after the transaction?

The filing shows the reporting person beneficially owned 281,176 stock options following the reported transaction. The specific 50,000-share option referenced is fully vested and exercisable with an exercise price of $2.936 and an expiration date of 03/11/2029.

What is the relationship of the reporting person to Mirum Pharmaceuticals (MIRM)?

The reporting person is identified as a Director of Mirum Pharmaceuticals, Inc., as indicated in the relationship section of the Form 4.

How is the indirect ownership in Mirum (MIRM) structured for this insider?

The filing reports indirect beneficial ownership of Mirum common stock through two trusts: 186,410 shares held by The Grey Family Trust dated November 12, 1999 and 93,750 shares held by The Grey 2018 Irrevocable Children's Trust.