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

Rhea-AI Filing Summary

Christopher Peetz, Mirum Pharmaceuticals CEO and director, reported related transactions on 08/11/2025 executed pursuant to a Rule 10b5-1 plan. He exercised 40,000 employee stock options with an exercise price of $2.936, resulting in an increase in directly held common stock to 178,641 shares. On the same date he sold 40,000 common shares at $62.00, reducing his direct holdings to 138,641 shares.

The filing also shows indirect beneficial ownership of 208,570 shares held by The Peetz Family Trust and that the exercised options are fully vested. All reported transactions were made under a 10b5-1 written plan adopted November 22, 2024.

Positive

• Transactions executed under a Rule 10b5-1 plan, indicating pre-planned trades and reduced insider trading risk
• Exercise of fully vested employee stock options, converting options into common shares
• Substantial indirect ownership remains (208,570 shares held by The Peetz Family Trust), maintaining economic alignment

Negative

• Sale of 40,000 shares at $62.00 reduced direct ownership from 178,641 to 138,641 shares
• Large insider sale could be perceived negatively by some investors, though it was pre-planned

Insights

Corporate Governance Expert

TL;DR: Insider transactions were pre-planned under a 10b5-1 plan and include an option exercise and an equal-sized block sale.

The transactions are explicitly reported as made pursuant to a Rule 10b5-1 trading plan, which indicates the trades were pre-scheduled and intended to provide an affirmative defense against insider trading claims. The CEO converted 40,000 vested options at a low exercise price ($2.936) and simultaneously sold 40,000 shares at $62.00. From a governance perspective, the use of a 10b5-1 plan reduces regulatory risk, while the sale materially reduces the CEO's direct share count by 40,000 shares. The presence of significant indirect ownership via a family trust (208,570 shares) suggests continued economic exposure.

Securities Analyst

TL;DR: Transaction structure is neutral; option exercise funded or converted into sale proceeds, with sustained indirect ownership.

The report shows an exercise of employee stock options that were fully vested and the subsequent sale of the same number of shares. The exercise price of $2.936 versus the sale price of $62.00 highlights a large realized spread per share, but the filing contains no information about the use of proceeds or market impact. After the transactions, direct holdings moved from 178,641 to 138,641 shares, while indirect holdings remain 208,570. On materiality, these are routine, pre-planned insider transactions rather than an unplanned, material governance event.

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^*

Peetz Christopher

(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
X	Officer (give title below)		Other (specify below)
	CHIEF EXECUTIVE OFFICER

3. Date of Earliest Transaction (Month/Day/Year)
08/11/2025

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	08/11/2025		M		40,000	A	$2.936	178,641	D
Common Stock	08/11/2025		S(1)		40,000	D	$62	138,641	D
Common Stock								208,570	I	By The Peetz Family 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
Employee Stock Option (right to buy)	$2.936	08/11/2025		M			40,000	(2)	03/11/2029	Common Stock	40,000	$0	158,487	D

Explanation of Responses:

1. Reported transaction occurred pursuant to a Rule 10b5-1 Plan adopted by the reporting person on November 22, 2024.

2. The stock option is fully vested.

	/s/ Judit Ryvkin, Attorney-in-Fact	08/12/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
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FAQ

What insider transactions did Mirum (MIRM) report for CEO Christopher Peetz?

On 08/11/2025 Mr. Peetz exercised 40,000 options at $2.936 and sold 40,000 shares at $62.00, reported on Form 4.

Were these trades part of a pre-arranged plan for MIRM insider Christopher Peetz?

Yes. The filing states the transactions occurred pursuant to a Rule 10b5-1 plan adopted on November 22, 2024.

How many Mirum shares does Christopher Peetz beneficially own after these transactions?

The filing shows 138,641 shares held directly after the sale and 208,570 shares indirectly via The Peetz Family Trust.

Were the stock options exercised by Christopher Peetz vested?

Yes. The filing includes an explicit statement that the stock option is fully vested.

Does the Form 4 indicate why the shares were sold?

No. The filing states the sale was made under a 10b5-1 plan but does not provide reasons or use of proceeds.