P. Kent Hawryluk - 26 Feb 2026 Form 4 Insider Report for MBX Biosciences, Inc. (MBX)

Role: President & CEO, Director
Signature: /s/ Richard Bartram, attorney-in-fact
Issuer symbol: MBX
Transactions as of: 26 Feb 2026
Net transactions value: +$460,288
Form type: 4
Filing time: 27 Feb 2026, 16:07:02 UTC
Previous filing: 03 Feb 2026
SEC: View on sec.gov

Reporting Owners (1)

Name	Relationship	Address	Signature	Signature date	CIK
Hawryluk P. Kent	President & CEO, Director	C/O MBX BIOSCIENCES, INC., 11711 N. MERIDIAN STREET, SUITE 300, CARMEL	/s/ Richard Bartram, attorney-in-fact	27 Feb 2026	0001673991

Transactions Table

Type	Sym	Class	Transaction	Value $	Shares	Change %	* Price $	Shares After	Date	Ownership	Footnotes
transaction	MBX	Common Stock	Options Exercise	$460,288	+28,768	+4.1%	$16.00	728,274	26 Feb 2026	Direct
holding	MBX	Common Stock						468,277	26 Feb 2026	By Trust	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)	Options Exercise	$0	-28,768	-24%	$0.000000	91,668	26 Feb 2026	Common Stock	28,768	$16.00	Direct	F2

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

Explanation of Responses:

Id	Content
F1	Shares held by the P. Kent Hawryluk Revocable Trust dated January 25, 2011, of which the Reporting Person serves as trustee. The Reporting Person disclaims beneficial ownership except to the extent of any pecuniary interest therein, and this report shall not be deemed an admission that such shares are beneficially owned by him for Section 16 or any other purpose.
F2	25% of the shares underlying this option vested and became exercisable on September 12, 2025, with the remaining 75% vesting in thirty-six (36) equal monthly installments thereafter, subject to the Reporting Person's continued service on each such vesting date.