Richard Bartram - 02 Feb 2026 Form 4 Insider Report for MBX Biosciences, Inc. (MBX)

Role: Chief Financial Officer
Signature: /s/ Richard Bartram
Issuer symbol: MBX
Transactions as of: 02 Feb 2026
Net transactions value: $0
Form type: 4
Filing time: 03 Feb 2026, 16:16:29 UTC
Previous filing: 05 Feb 2025
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Bartram Richard	Chief Financial Officer	C/O MBX BIOSCIENCES, INC., 11711 N. MERIDIAN STREET, SUITE 300, CARMEL	/s/ Richard Bartram	03 Feb 2026	0001723729

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	MBX	Common Stock	Award	$0	+15,000		$0.000000	15,000	02 Feb 2026	Direct	F1

Derivative Securities (e.g., puts, calls, warrants, options, convertible securities)

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Underlying Class	Amount	Exercise Price	Ownership	Footnotes
transaction	MBX	Stock option (right to buy)	Award	$0	+70,000		$0.000000	70,000	02 Feb 2026	Common Stock	70,000	$39.07	Direct	F2

* An asterisk sign (*) next to the price indicates that the price is likely invalid.

Explanation of Responses:

Id	Content
F1	Represents the grant of restricted stock units (RSUs). The RSUs will vest over a four (4) year period in equal quarterly installments, subject to the Reporting Person's continued service on such vesting date.
F2	The shares underlying this option vest and become exercisable in forty eight (48) equal monthly installments, beginning on March 2, 2026, subject to the Reporting Person's continued service on such vesting date.