MBX Biosciences director gets 18,200 stock options

One-third of the underlying shares becomes exercisable on October 20, 2027, with the remainder vesting monthly over the following two years subject to continued service.

Rhea-AI Filing Summary

MBX Biosciences, Inc. director Peter Radovich received a direct grant of options covering 18,200 shares of common stock on October 20, 2026, at an exercise price of $53.50 per share. One-third of the shares underlying the option will vest and become exercisable on October 20, 2027; the remainder will vest monthly over the following two years, subject to his continued service on each vesting date. The options expire October 20, 2036.

Insider Trade Summary

Grant/Award: 18,200 shares

Grant/Award 1 txn

Insider Radovich Peter

Role Director

Type	Security	Shares	Price	Value
Grant/Award	Stock option (right to buy) F1	18,200	$0.00	$0.00

Holdings After Transaction: Stock option (right to buy) — 18,200 contracts (Direct)

Footnotes (1)

1. F1. One-third of the shares underlying this option will vest and become exercisable on October 20, 2027, the anniversary of the date of grant, with the remainder vesting monthly over the subsequent two year period, subject to the Reporting Person's continued service on each such vesting date.

Key Figures

Options granted: 18,200 options Underlying common shares: 18,200 shares Exercise price: $53.50 per share +3 more

6 metrics

Options granted 18,200 options Granted October 20, 2026

Underlying common shares 18,200 shares Shares covered by the option grant

Exercise price $53.50 per share Option grant

Initial vesting One-third Will vest and become exercisable October 20, 2027

Remaining vesting period Two years Remainder vests monthly, subject to continued service

Option expiration October 20, 2036 Expiration date

Key Terms

stock option, vest, exercisable, exercise price

4 terms

stock option financial

"Stock option (right to buy)"

A stock option is a contract that gives you the right to buy or sell a company's stock at a specific price within a certain time frame. People use them to potentially make money if the stock's price moves favorably or to protect against losses. It's like holding a coupon that can be used to buy or sell stock at a set price later on.

vest financial

"will vest and become exercisable"

A vest is the process by which an employee earns the right to receive certain benefits or ownership interests, such as stock or retirement funds, over time. It’s similar to earning a reward gradually, ensuring that the benefit becomes fully yours only after a set period or meeting specific conditions. This makes it important for investors because it determines when they can actually claim or use those benefits.

exercisable financial

"will vest and become exercisable"

exercise price financial

"exercise price of $53.50 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.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many options did MBX director Peter Radovich receive?

Peter Radovich, a director of MBX Biosciences, received options covering 18,200 shares on October 20, 2026, at an exercise price of $53.50 per share. The options are subject to the reported vesting schedule.

When do Peter Radovich's MBX options vest?

One-third of the underlying shares will vest and become exercisable on October 20, 2027. The remainder will vest monthly over the subsequent two-year period, subject to Radovich's continued service on each vesting date.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/22/2026 - 08:25 AM EDT Accepted by SEC EDGAR 10/22/2026 - 08:25 AM EDT Learn about SEC filing dates

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^*

Radovich Peter

(Last) (First) (Middle)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/20/2026

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)	$53.5	10/20/2026		A		18,200		(1)	10/20/2036	Common Stock	18,200	$0	18,200	D

Explanation of Responses:

1. One-third of the shares underlying this option will vest and become exercisable on October 20, 2027, the anniversary of the date of grant, with the remainder vesting monthly over the subsequent two year period, subject to the Reporting Person's continued service on each such vesting date.

	/s/ Steven L. Hoerter	10/22/2026
	** 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)