MBX Biosciences (MBX) CFO receives 15,000 RSUs and 70,000 stock options

Rhea-AI Filing Summary

MBX Biosciences, Inc.’s Chief Financial Officer Richard Bartram received new equity awards in the form of restricted stock units and stock options. On February 2, 2026, he was granted 15,000 shares of common stock as RSUs at a price of $0 per share, all held directly after the grant.

He was also granted a stock option to buy 70,000 shares of common stock with an exercise price of $39.07 per share. These options vest and become exercisable in 48 equal monthly installments beginning on March 2, 2026, while the 15,000 RSUs vest in equal quarterly installments over four years. All vesting is conditioned on his continued service with the company.

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
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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).

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^*

Bartram Richard

(Last) (First) (Middle)

C/O MBX BIOSCIENCES, INC.

11711 N. MERIDIAN STREET, SUITE 300

(Street)

CARMEL IN 46032

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
MBX Biosciences, Inc. [ MBX ]

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

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

3. Date of Earliest Transaction (Month/Day/Year)
02/02/2026

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	02/02/2026		A		15,000(1)	A	$0	15,000	D

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)	$39.07	02/02/2026		A		70,000		(2)	02/02/2036	Common Stock	70,000	$0	70,000	D

Explanation of Responses:

1. 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.

2. 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.

	/s/ Richard Bartram	02/03/2026
	** 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 equity awards did MBX (MBX) CFO Richard Bartram receive?

Richard Bartram received 15,000 restricted stock units and a stock option for 70,000 common shares. The RSUs vest quarterly over four years, and the options vest monthly over 48 months, aligning his compensation with longer-term company performance.

How do the MBX (MBX) CFO’s 15,000 RSUs vest over time?

The 15,000 restricted stock units vest in equal quarterly installments over four years, subject to his continued service. This structure gradually delivers share ownership, encouraging retention and aligning incentives with the company’s multi‑year operational and financial goals.

What are the terms of the 70,000 stock options granted to MBX’s CFO?

The CFO received stock options for 70,000 common shares at an exercise price of $39.07. These options vest in 48 equal monthly installments starting March 2, 2026, contingent on continued service, creating a steady, long-term incentive linked directly to MBX’s share price.

When do the MBX (MBX) CFO’s new equity awards start vesting?

The stock options begin vesting on March 2, 2026 in 48 monthly installments. The 15,000 RSUs vest in equal quarterly tranches over four years, with both awards requiring that he remain in service on each vesting date.

Is the MBX CFO’s new stock option grant directly owned?

Yes. The Form 4 indicates the 70,000-share stock option is held with direct ownership. Following the transaction, 70,000 derivative securities and 15,000 common shares from RSUs are shown as directly owned by the CFO, reflecting his personal equity stake.

What was the transaction date for the MBX CFO equity grants?

Both the RSU grant of 15,000 common shares and the stock option for 70,000 shares were effective on February 2, 2026. That date marks the official award of these equity incentives under MBX Biosciences’ compensation arrangements for its Chief Financial Officer.