MBX insider plans $256K sale of vested shares

MBX insider Peter K. Hawryluk filed to potentially sell 3,745 shares of common stock through Fidelity Brokerage Services.

Rhea-AI Filing Summary

MBX insider Peter K. Hawryluk filed to potentially sell 3,745 shares of common stock through Fidelity Brokerage Services. The shares relate to restricted stock vesting on August 14, 2026 and have an indicated aggregate market value of $255,737.06. MBX reports 48,160,096 common shares outstanding on NASDAQ. In the prior three months, Hawryluk sold 936 shares for $61,563.42.

Key Figures

Shares to be sold: 3,745 shares Aggregate market value of proposed sale: $255,737.06 Shares outstanding: 48,160,096 shares +4 more

7 metrics

Shares to be sold 3,745 shares Common stock covered by the Form 144 for potential sale

Aggregate market value of proposed sale $255,737.06 Estimated market value of the 3,745 MBX common shares

Shares outstanding 48,160,096 shares MBX common shares outstanding on NASDAQ

Shares sold in past 3 months 936 shares Common shares sold by Peter K. Hawryluk on 08/04/2026

Value of past 3-month sale $61,563.42 Total proceeds from 936 MBX shares sold on 08/04/2026

Restricted stock vesting date 08/14/2026 Date of restricted stock vesting classified as compensation

Planned sale timing reference 08/17/2026 Date associated with securities information for the proposed sale

Key Terms

Form 144, restricted stock vesting, aggregate market value, compensation

4 terms

Form 144 regulatory

"144: Securities To Be Sold"

Form 144 is a document that investors must file with the government when they plan to sell a large number of shares of a company's stock. It helps ensure transparency so everyone knows how many shares are being sold and when, which can impact the stock's price.

restricted stock vesting financial

"Common | 08/14/2026 | Restricted Stock Vesting | Issuer"

Restricted stock vesting is the timetable and conditions under which shares granted to employees or insiders become fully owned and can be sold, typically requiring continued work or meeting performance goals. It matters to investors because large blocks of shares can become tradable at once, which can change share supply and price, and because vesting aligns insiders’ incentives with the company’s long‑term performance—think of it like a timed unlock that both rewards and locks in key people.

aggregate market value financial

"Common | Fidelity Brokerage Services LLC ... | 3745 | 255737.06"

Aggregate market value is the combined price you would pay to buy all outstanding shares of a company or all companies in a group at current market prices — essentially the sum of each stock’s market capitalization. It matters to investors because it shows the overall size and weight of an investment or sector (like the total cost to buy every piece of a puzzle), helps compare scale across companies or markets, and influences index composition and risk exposure.

compensation financial

"3745 | 08/14/2026 | Compensation"

FAQ

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

What does MBX insider Peter K. Hawryluk disclose in this Form 144 filing?

Peter K. Hawryluk indicates a potential sale of 3,745 MBX common shares related to restricted stock vesting on August 14, 2026, with an aggregate market value of $255,737.06, using Fidelity Brokerage Services as broker.

How many MBX (symbol MBX) shares does the Form 144 register for potential sale?

The Form 144 covers a proposed sale of 3,745 shares of MBX common stock. These shares tie to restricted stock vesting and are valued in the filing at an aggregate market value of $255,737.06 for this planned disposition.

What recent MBX stock sales does Peter K. Hawryluk report in the last three months?

Hawryluk reports a prior sale of 936 MBX common shares on August 4, 2026 for total proceeds of $61,563.42. This transaction is disclosed as securities sold during the past three months in the Form 144 information.

What is the stated number of MBX common shares outstanding in this Form 144?

The Form 144 states that MBX has 48,160,096 common shares outstanding. This figure provides context for the relative size of the 3,745-share proposed sale compared with the company’s total common equity base on NASDAQ.

What is the nature of the MBX shares being sold by Peter K. Hawryluk?

The MBX shares relate to restricted stock vesting recorded on August 14, 2026 and are identified as compensation from the issuer. This indicates the shares originated from an equity award that has recently vested before the planned sale.

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

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Available on EDGAR 08/17/2026 - 03:42 PM Accepted by SEC EDGAR 08/17/2026 - 03:41 PM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0001673991
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	MBX Biosciences, Inc.
SEC File Number	001-42272
Address of Issuer	11711 N. MERIDIAN STREET SUITE 300 CARMEL INDIANA 46032
Phone	3179893100
Name of Person for Whose Account the Securities are To Be Sold	Hawryluk P. Kent
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Former Officer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Fidelity Brokerage Services LLC 900 Salem Street Smithfield RI 02917	3745	255737.06	48160096	08/17/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	08/14/2026	Restricted Stock Vesting	Issuer			3745	08/14/2026	Compensation

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
Peter K. Hawryluk 11711 N. Meridian Street Suite 300 Carmel IN 46032	Common	08/04/2026	936	61563.42

144: Remarks and Signature

Remarks	Sale includes an amount necessary to cover a tax obligation resulting from the settlement of a vested equity award distribution.
Date of Notice	08/17/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Daniel Tucci, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Peter K. Hawryluk
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)