MBX Biosciences (NASDAQ: MBX) CMO sells 231 shares to cover RSU tax obligations

Rhea-AI Filing Summary

MBX Biosciences Chief Medical Officer Salomon Azoulay reported a small routine sale of company stock. On May 6, 2026, Azoulay sold 231 shares of common stock in an open-market transaction at a weighted average price of $29.54 per share.

According to the disclosure, these shares were sold to cover tax obligations triggered by the vesting of restricted stock units under a mandatory sell-to-cover agreement with the company. After this transaction, Azoulay directly holds 14,769 shares of MBX Biosciences common stock, indicating this was a minor, tax-related disposition rather than a large change in ownership.

Insider Trade Summary

Net Seller: 231 shares ($6,824)

Net Sell 1 txn

Insider Azoulay Salomon

Role Chief Medical Officer

Sold 231 shs ($7K)

Type	Security	Shares	Price	Value
Sale	Common Stock	231	$29.54	$7K

Holdings After Transaction: Common Stock — 14,769 shares (Direct, null)

Footnotes (1)

1. The sales reported on this Form 4 represent shares of common stock sold by the Reporting Person to cover tax obligations in connection with the vesting of restricted stock units, pursuant to a mandatory sell-to-cover agreement between the Reporting Person and the Company. The price reported in Column 4 is a weighted average price. These shares were sold on an aggregate basis for all Company participants, at prices ranging from $29.23 to $29.88, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the aggregate number of shares sold at each separate price within the range set forth in this footnote.

Key Figures

Shares sold: 231 shares Weighted average sale price: $29.54 per share Post-transaction holdings: 14,769 shares +1 more

4 metrics

Shares sold 231 shares Open-market sale on May 6, 2026

Weighted average sale price $29.54 per share Common stock sale to cover tax obligations

Post-transaction holdings 14,769 shares Direct ownership after the reported sale

Price range of sales $29.23–$29.88 per share Aggregate sales range for company participants

Key Terms

restricted stock units, mandatory sell-to-cover agreement, weighted average price, open-market sale

4 terms

restricted stock units financial

"tax obligations in connection with the vesting of restricted stock units"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

mandatory sell-to-cover agreement financial

"pursuant to a mandatory sell-to-cover agreement between the Reporting Person and the Company"

weighted average price financial

"The price reported in Column 4 is a weighted average price."

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

open-market sale financial

"transaction_action: "open-market sale""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

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^*

Azoulay Salomon

(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)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/06/2026

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
Common Stock	05/06/2026		S		231(1)	D	$29.54(2)	14,769	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

Explanation of Responses:

1. The sales reported on this Form 4 represent shares of common stock sold by the Reporting Person to cover tax obligations in connection with the vesting of restricted stock units, pursuant to a mandatory sell-to-cover agreement between the Reporting Person and the Company.

2. The price reported in Column 4 is a weighted average price. These shares were sold on an aggregate basis for all Company participants, at prices ranging from $29.23 to $29.88, inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer or the staff of the Securities and Exchange Commission, upon request, full information regarding the aggregate number of shares sold at each separate price within the range set forth in this footnote.

	/s/ P. Kent Hawryluk, attorney-in-fact	05/08/2026
	** 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 insider transaction did MBX (MBX Biosciences) report for Salomon Azoulay?

MBX Biosciences reported that Chief Medical Officer Salomon Azoulay sold 231 shares of common stock on May 6, 2026. The sale was an open-market transaction tied to tax obligations from vesting restricted stock units.

At what price were the MBX shares sold by Salomon Azoulay on May 6, 2026?

The shares were sold at a weighted average price of $29.54 per share. The transaction covered multiple trades executed for company participants at prices ranging from $29.23 to $29.88, as described in the filing footnotes.

Why did MBX Biosciences’ CMO sell 231 shares of company stock?

The sale was made to cover tax obligations arising from the vesting of restricted stock units. It was executed under a mandatory sell-to-cover agreement between Salomon Azoulay and MBX Biosciences, indicating a tax-driven, routine transaction.

How many MBX Biosciences shares does Salomon Azoulay own after this Form 4 transaction?

Following the sale, Salomon Azoulay directly holds 14,769 shares of MBX Biosciences common stock. This remaining position suggests the 231-share sale was relatively small compared to his total direct holdings reported in the filing.

Was the MBX insider sale by Salomon Azoulay a discretionary trade or part of a plan?

The filing states the sale occurred under a mandatory sell-to-cover agreement with MBX Biosciences. Shares were sold to satisfy tax obligations from restricted stock unit vesting, characterizing it as a mechanical, tax-related transaction rather than a discretionary trade.