Michael G. Grey - 19 Dec 2025 Form 4 Insider Report for Mirum Pharmaceuticals, Inc. (MIRM)

Reporting relationship: Director
Issuer ticker: MIRM
Reported as of: 19 Dec 2025
Net transaction value: -$3,753,200
SEC form: 4
Accepted by SEC: 23 Dec 2025, 18:50:04 UTC
Prior SEC filing: 15 Dec 2025
Next SEC filing: 26 May 2026
Source filing: View source filing
Reporting owner signature: /s/ Jody Howe, Attorney-in-Fact

Key filing fact

Michael G. Grey filed Form 4 for Mirum Pharmaceuticals, Inc. (MIRM) on 23 Dec 2025.

Key facts

This page summarizes Michael G. Grey's Form 4 filing for Mirum Pharmaceuticals, Inc. (MIRM).
3 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 23 Dec 2025, 18:50.

Change

Previous filing in this sequence was filed on 15 Dec 2025.
Current net transaction value: -$3,753,200.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001240122 Primary reporting owner

GREY MICHAEL G

Relationship: Director
Address: C/O MIRUM PHARMACEUTICALS, INC., 989 E HILLSDALE BLVD., SUITE 300, FOSTER CITY
Signature: /s/ Jody Howe, Attorney-in-Fact
Signature date: 23 Dec 2025

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

MIRM transaction

Common Stock

Options Exercise

Transaction value: $146,800
Shares: +50,000
Change %
Price: $2.94
Shares after: 50,000
Date: 19 Dec 2025
Ownership: Direct

MIRM transaction

Common Stock

Sale

Transaction value: $3,900,000
Shares: -50,000
Change %: -100%
Price: $78.00
Shares after: 0
Date: 19 Dec 2025
Ownership: Direct
Footnotes: F1

MIRM holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 186,410
Date: 19 Dec 2025
Ownership: By The Grey Family Trust dated November 12,1999

MIRM holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 93,750
Date: 19 Dec 2025
Ownership: By The Grey 2018 Irrevocable Children's Trust

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

MIRM transaction Derivative

Stock Option (right to buy)

Options Exercise

Transaction value: $0
Shares: -50,000
Change %: -22%
Price: $0.000000
Shares after: 181,176
Date: 19 Dec 2025
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 50,000
Exercise price: $2.94
Footnotes: F2

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Rule 10b5-1 trading plan

These transactions were reported as open-market trades under a Rule 10b5-1 plan. The plan lets an insider set trading instructions in advance, which can reduce the risk of trading while in possession of material nonpublic information.

Original filing language: transaction made pursuant to a contract, instruction, or written plan intended to satisfy Rule 10b5-1(c).

Explanation of responses 2 footnotes

Footnote F1

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

Footnote F2

The stock option is fully vested and exercisable.