MBX Biosciences (MBX) director receives stock options for 12,500 shares

Rhea-AI Filing Summary

MBX Biosciences, Inc. director Laurie Stelzer 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.

According to the terms, the grant will vest in full on the earlier of the one-year anniversary of the June 4, 2026 grant date or the date of the company’s next annual meeting of stockholders, as long as Stelzer continues to serve as a non-employee director. Following this award, Stelzer holds options for 12,500 shares directly.

Insider Trade Summary

1 transaction reported

Mixed 1 txn

Insider Stelzer Laurie

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

Option grant size: 12,500 shares Exercise price: $30.91 per share Expiration date: June 4, 2036 +1 more

4 metrics

Option grant size 12,500 shares Stock option award to director Laurie Stelzer

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

Expiration date June 4, 2036 Option term for director grant

Post-grant options held 12,500 shares Total options following transaction, direct ownership

Key Terms

Stock option (right to buy), exercise price, vest in full, expiration date

4 terms

Stock option (right to buy) financial

"Security title reported as Stock option (right to buy) for the director grant."

exercise price financial

"The stock option grant carries an exercise price of $30.91 per share."

The exercise price is the fixed amount at which you can buy or sell an asset, like a stock, when using an options contract. It matters because it helps determine whether exercising the option will be profitable or not, depending on the current market price. Think of it as the set price you agree on today to buy or sell later.

vest in full financial

"The grant will vest in full on the earlier of the one-year anniversary or next annual meeting."

expiration date financial

"The options have an expiration date of June 4, 2036 under the award terms."

The expiration date is the deadline after which a financial contract, such as an option or a futures agreement, is no longer valid or can be exercised. It matters to investors because it determines the timeframe during which they can take action or benefit from the contract, similar to how a coupon or a food item has a limited period of usefulness. Once the expiration date passes, the contract loses its value or ability to be used.

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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^*

Stelzer Laurie

(Last) (First) (Middle)

C/O MBX BIOSCIENCES, INC.

11711 N. MERIDIAN STREET, STE 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		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) director Laurie Stelzer report in this Form 4?

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

What are the key terms of Laurie Stelzer’s MBX stock option grant?

The grant covers 12,500 shares of common stock with an exercise price of $30.91 per share. The options expire on June 4, 2036, giving a long exercise window, and represent compensation rather than a cash purchase of shares.

When do Laurie Stelzer’s MBX Biosciences options vest?

The options vest in full on the earlier of the one-year anniversary of the June 4, 2026 grant date or the date of MBX Biosciences’ next annual stockholders’ meeting. Vesting is conditioned on her continued service as a non-employee director.

Is Laurie Stelzer buying or selling MBX shares in this filing?

She is not buying or selling shares in the market. The Form 4 reports a grant of stock options, giving her the right to buy 12,500 MBX shares at $30.91, subject to vesting, as part of director compensation.

How many MBX shares are covered by options after this grant?

After the transaction, Laurie Stelzer holds stock options covering 12,500 shares of MBX Biosciences common stock directly. This reflects the full amount of the newly granted options disclosed in the filing, with no additional derivative holdings shown.

What is the expiration date of Laurie Stelzer’s MBX stock options?

The options expire on June 4, 2036. After that expiration date, any unexercised options will lapse and no longer give the right to purchase MBX Biosciences shares at the $30.91 exercise price specified in the award.