MBX Biosciences (MBX) director and 10% owner receives 12,500 stock options grant

Rhea-AI Filing Summary

MBX Biosciences, Inc. director and ten percent owner Patrick J. Heron received a grant of stock options covering 12,500 shares of common stock. The options have an exercise price of $30.91 per share and expire on June 4, 2036.

The grant will vest in full on the earlier of the one-year anniversary of the grant date or the date of the company’s next annual meeting of stockholders, as long as the non-employee director continues to provide services. This is a compensation-related award rather than an open-market share purchase or sale.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider Heron Patrick J

Role null

Type	Security	Shares	Price	Value
Grant/Award	Stock option (right to buy)	12,500	$0.00	--

Holdings After Transaction: Stock option (right to buy) — 12,500 shares (Direct, null)

Footnotes (1)

1. [object Object]

Key Figures

Options granted: 12,500 shares Exercise price: $30.91 per share Expiration date: June 4, 2036 +3 more

6 metrics

Options granted 12,500 shares Stock option grant to director and ten percent owner

Exercise price $30.91 per share Stock option (right to buy) grant terms

Expiration date June 4, 2036 Option term for granted stock options

Shares underlying options 12,500 shares Underlying MBX Biosciences common stock

Transaction code A (Grant, award, or other acquisition) Characterization of Form 4 transaction

Vesting trigger Earlier of 1-year or next annual meeting Vesting condition subject to continued service

Key Terms

Stock option (right to buy), Grant, award, or other acquisition, non-employee director, annual meeting of stockholders

4 terms

Stock option (right to buy) financial

"security_title: "Stock option (right to buy)""

Grant, award, or other acquisition financial

"transaction_code_description: "Grant, award, or other acquisition""

non-employee director financial

"subject to the non-employee director's continued services to the Company"

annual meeting of stockholders financial

"on the date of our next annual meeting of stockholders"

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Form 4 Insider Transactions: What Each Field Means →

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).

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^*

Heron Patrick J

(Last) (First) (Middle)

C/O MBX BIOSCIENCES, INC.

11711 N. MERIDIAN STREET, SUITE 300

(Street)

CARMEL INDIANA 46032

(City) (State) (Zip)

UNITED STATES

(Country)

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

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

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/04/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

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

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)	$30.91	06/04/2026		A		12,500		(1)	06/04/2036	Common Stock	12,500	$0	12,500	D

Explanation of Responses:

1. The grant will vest in full on the earlier of the one-year anniversary of the grant date or on the date of our next annual meeting of stockholders, subject to the non-employee director's continued services to the Company.

	/s/ P. Kent Hawryluk, attorney-in-fact	06/05/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What did MBX (MBX) insider Patrick J. Heron report in this Form 4?

Patrick J. Heron reported receiving a grant of stock options for 12,500 shares of MBX Biosciences common stock. The options are a compensation-related award, not an open-market trade, and give him the right to buy shares at a fixed exercise price.

What are the key terms of the MBX (MBX) stock options granted to Patrick J. Heron?

The grant covers 12,500 shares of MBX Biosciences common stock with an exercise price of $30.91 per share and an expiration date of June 4, 2036. These options provide long-term potential upside if the stock trades above the exercise price.

How do the MBX (MBX) options granted to Patrick J. Heron vest?

The stock options vest in full on the earlier of one year after the June 4, 2026 grant date or the date of MBX Biosciences’ next annual stockholder meeting. Vesting requires the non-employee director to continue providing services to the company through that date.

Is the MBX (MBX) Form 4 transaction a stock purchase or sale?

No, the Form 4 shows a grant of stock options, not a purchase or sale of common shares. The transaction is coded as an acquisition (grant or award), reflecting equity-based compensation rather than open-market trading activity in MBX Biosciences stock.

What position does Patrick J. Heron hold at MBX (MBX) and why is this Form 4 required?

Patrick J. Heron is a director and a ten percent owner of MBX Biosciences. As an insider, he must report equity-related transactions such as option grants on Form 4, providing transparency into his compensation-related holdings and potential future share ownership.