MBX Biosciences (MBX) CMO exercises options and sells 70,003 shares under 10b5-1 plan

Filing Impact

(Neutral)

Filing Sentiment

(Neutral)

Form Type

Rhea-AI Filing Summary

MBX Biosciences Chief Medical Officer Salomon Azoulay reported an exercise-and-sell transaction in company stock. On 2026-05-08, he exercised options to acquire a total of 70,003 shares of common stock at strike prices of $16.00 and $10.46 per share, then sold 70,003 shares in open-market transactions.

The sales occurred at weighted average prices of $38.30 and $38.38 per share, with individual trades executed between $35.00 and $41.26, under an approved Rule 10b5-1 trading plan adopted on January 27, 2026. Following these transactions, Azoulay directly holds 14,769 common shares.

He also retains stock options, including grants that had 30,008 and 194,540 options outstanding after the reported exercises, subject to vesting schedules that began vesting 25% on June 24, 2025 and September 12, 2025, with the remaining 75% vesting in 36 monthly installments.

Insider Trade Summary 10b5-1

Net Seller: 70,003 shares ($2,685,515)

Net Sell 6 txns

Insider Azoulay Salomon

Role Chief Medical Officer

Sold 70,003 shs ($2.69M)

Type	Security	Shares	Price	Value
Exercise	Stock option (right to buy)	55,000	$0.00	--
Exercise	Stock option (right to buy)	15,003	$0.00	--
Exercise	Common Stock	55,000	$10.46	$575K
Sale	Common Stock	55,000	$38.38	$2.11M
Exercise	Common Stock	15,003	$16.00	$240K
Sale	Common Stock	15,003	$38.30	$575K

Holdings After Transaction: Stock option (right to buy) — 194,540 shares (Direct, null); Common Stock — 69,769 shares (Direct, null)

Footnotes (1)

The sales reported on this Form 4 represent the exercise and sale of common stock options by the reporting person pursuant to an approved Rule 10b5-1 trading plan adopted on January 27, 2026. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $35.00 to $41.26, 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 number of shares purchased at each separate price within the range set forth in this footnote. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $35.00 to $41.26, 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 number of shares purchased at each separate price within the range set forth in this footnote. 25% of the shares underlying this option vested and became exercisable on June 24, 2025, with the remaining 75% vesting in thirty-six (36) substantially equal monthly installments thereafter, subject to the Reporting Person's continued service on each such vesting date. 25% of the shares underlying this option vested and became exercisable on September 12, 2025, with the remaining 75% vesting in thirty-six (36) substantially equal monthly installments thereafter, subject to the Reporting Person's continued service on each such vesting date.

Key Figures

Shares sold: 70,003 shares Sale prices: $38.30 and $38.38/share Strike prices: $16.00 and $10.46/share +5 more

8 metrics

Shares sold 70,003 shares Total common shares sold in open-market transactions on 2026-05-08

Sale prices $38.30 and $38.38/share Weighted average prices for two sale blocks of common stock

Strike prices $16.00 and $10.46/share Option exercise prices for 70,003 shares of common stock

Shares held after 14,769 shares Direct common stock ownership following reported transactions

Remaining option grant 1 30,008 options Stock options outstanding after 15,003-share exercise at $16.00

Remaining option grant 2 194,540 options Stock options outstanding after 55,000-share exercise at $10.46

10b5-1 plan adoption date January 27, 2026 Date Rule 10b5-1 trading plan used for these sales was adopted

Vesting start dates June 24, 2025; September 12, 2025 Initial 25% vesting dates for the two option grants

Key Terms

Rule 10b5-1 trading plan, Stock option (right to buy), weighted average price, vested and became exercisable, +2 more

6 terms

Rule 10b5-1 trading plan regulatory

"exercise and sale of common stock options by the reporting person pursuant to an approved Rule 10b5-1 trading plan"

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

Stock option (right to buy) financial

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

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.

vested and became exercisable financial

"25% of the shares underlying this option vested and became exercisable on June 24, 2025"

substantially equal monthly installments financial

"the remaining 75% vesting in thirty-six (36) substantially equal monthly installments thereafter"

derivative security financial

"transaction_code_description": "Exercise or conversion of derivative security""

A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.

Form 4 Insider Transactions: What Each Field Means →

05/11/2026 - 04:01 PM

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)
05/08/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	05/08/2026⁽¹⁾		M		55,000	A	$10.46	69,769	D
Common Stock	05/08/2026⁽¹⁾		S		55,000	D	$38.38⁽²⁾	14,769	D
Common Stock	05/08/2026⁽¹⁾		M		15,003	A	$16	29,772	D
Common Stock	05/08/2026⁽¹⁾		S		15,003	D	$38.3⁽³⁾	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Stock option (right to buy)	$10.46	05/08/2026		M		55,000		⁽⁴⁾	08/02/2034	Common Stock	55,000	$0	194,540	D
Stock option (right to buy)	$16	05/08/2026		M		15,003		⁽⁵⁾	09/12/2034	Common Stock	15,003	$0	30,008	D

Explanation of Responses:

1. The sales reported on this Form 4 represent the exercise and sale of common stock options by the reporting person pursuant to an approved Rule 10b5-1 trading plan adopted on January 27, 2026.

2. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $35.00 to $41.26, 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 number of shares purchased at each separate price within the range set forth in this footnote.

3. The price reported in Column 4 is a weighted average price. These shares were purchased in multiple transactions at prices ranging from $35.00 to $41.26, 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 number of shares purchased at each separate price within the range set forth in this footnote.

4. 25% of the shares underlying this option vested and became exercisable on June 24, 2025, with the remaining 75% vesting in thirty-six (36) substantially equal monthly installments thereafter, subject to the Reporting Person's continued service on each such vesting date.

5. 25% of the shares underlying this option vested and became exercisable on September 12, 2025, with the remaining 75% vesting in thirty-six (36) substantially equal monthly installments thereafter, subject to the Reporting Person's continued service on each such vesting date.

	/s/ P. Kent Hawryluk, attorney-in-fact	05/11/2026
	** 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)

Source: View Original Filing on SEC EDGAR

FAQ

What insider transaction did MBX (MBX) disclose for Salomon Azoulay?

MBX Biosciences reported that Chief Medical Officer Salomon Azoulay exercised options for 70,003 shares and sold 70,003 common shares in open-market transactions on 2026-05-08, as detailed in a Form 4 insider filing.

At what prices did the MBX (MBX) insider stock sales occur?

The reported MBX Biosciences stock sales used weighted average prices of $38.30 and $38.38 per share, with individual trades executed in a range from $35.00 to $41.26 per share, according to the Form 4 disclosure.

What option exercise prices were reported in the MBX (MBX) Form 4?

Salomon Azoulay exercised stock options with strike prices of $16.00 and $10.46 per share, converting these options into 70,003 shares of MBX Biosciences common stock before the corresponding open-market sales disclosed in the Form 4.

How many MBX (MBX) shares does the reporting person hold after the transactions?

After the reported exercise-and-sell transactions, Chief Medical Officer Salomon Azoulay directly holds 14,769 shares of MBX Biosciences common stock, as shown in the post-transaction ownership column of the Form 4 filing.

Were the MBX (MBX) insider sales made under a Rule 10b5-1 plan?

Yes. The Form 4 footnotes state that the sales reflect the exercise and sale of stock options under an approved Rule 10b5-1 trading plan that was adopted on January 27, 2026, indicating these trades were pre-arranged.

What vesting schedule applies to the MBX (MBX) stock options mentioned?

Footnotes explain that for each option grant, 25% of the underlying shares vested on June 24, 2025 or September 12, 2025, with the remaining 75% vesting in thirty-six equal monthly installments, subject to continued service.