Bartram files Form 144 to sell 9,167 shares

Richard B. Bartram reported a proposed sale of 9,167 shares of Common Stock related to a stock option exercise, planned for 06/10/2026 and to be processed through Fidelity Brokerage Services LLC on NASDAQ for cash.

Rhea-AI Filing Summary

Richard B. Bartram reported a proposed sale of 9,167 shares of Common Stock related to a stock option exercise, planned for 06/10/2026 and to be processed through Fidelity Brokerage Services LLC on NASDAQ for cash. The filing also lists multiple open-market dispositions by Mr. Bartram during the prior three months, including sales on 05/11/2026 (22,500 shares) and 06/09/2026 (10,833 shares).

Insights

Insider Transactions Analyst

Affiliate plans to sell 9,167 shares after exercising options; several recent large sales are disclosed.

The filing records a stock option exercise tied to 9,167 shares slated for sale on 06/10/2026 through Fidelity Brokerage Services LLC. The method of disposition is listed as Cash.

Recent sale entries in the submission show multiple open-market dispositions in the prior three months, notably 22,500 shares on 05/11/2026 and 10,833 shares on 06/09/2026. These transactions are factual disclosures; their trading impact depends on market size and timing.

Key Figures

Planned sale: 9,167 shares Recent sale: 22,500 shares Recent sale: 10,833 shares +2 more

5 metrics

Planned sale 9,167 shares Stock Option Exercise on 06/10/2026

Recent sale 22,500 shares Sold on 05/11/2026 for $991,901.00

Recent sale 10,833 shares Sold on 06/09/2026 for $321,273.00

Recent sale 10,000 shares Sold on 03/16/2026 for $300,471.00

Recent sale 15,000 shares Sold on 05/13/2026 for $554,295.50

Key Terms

Stock Option Exercise, Fidelity Brokerage Services LLC, Cash

3 terms

Stock Option Exercise financial

"Common | 06/10/2026 | Stock Option Exercise"

A stock option exercise is the act of using a previously granted right to buy shares of a company's stock at a specific, predetermined price by paying that price and receiving the shares. It matters to investors because exercising changes who owns the shares (which can dilute existing ownership), can trigger taxable events and shift potential gains or losses, and affects voting power and the company’s outstanding share count—like turning a voucher into an actual product that becomes part of circulating supply.

Fidelity Brokerage Services LLC market

"Fidelity Brokerage Services LLC 900 Salem Street Smithfield RI 02917"

Cash financial

"06/10/2026 | Stock Option Exercise | Issuer | | | 9167 | 06/10/2026 | Cash"

FAQ

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

What did MBX insider Richard B. Bartram report in the Form 144?

He reported a proposed sale of 9,167 shares of Common Stock tied to a stock option exercise, scheduled for 06/10/2026, to be sold for cash through Fidelity Brokerage Services LLC on NASDAQ.

Does the filing show prior sales by Richard B. Bartram?

Yes; the filing lists multiple sales in the past three months, including 22,500 shares on 05/11/2026 ($991,901.00) and 10,833 shares on 06/09/2026 ($321,273.00), with dates and proceeds recorded.

What is the disposition method for the 9,167 shares in the Form 144?

The disposition method is listed as Cash and the transaction is associated with a Stock Option Exercise, with execution through Fidelity Brokerage Services LLC on 06/10/2026.

Where were the sales to be executed according to the filing?

The filing indicates transactions are to be processed via Fidelity Brokerage Services LLC, 900 Salem Street, Smithfield RI and executed on the NASDAQ market as recorded in the submission.

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

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Accepted by SEC EDGAR 06/10/2026 - 12:41 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	0001723729
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	Bartram Richard
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	9167	280010.00	47597536	06/10/2026	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	06/10/2026	Stock Option Exercise	Issuer			9167	06/10/2026	Cash

* 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
Richard B. Bartram 11711 N. Meridian Street, Suite 300 Carmel IN 46032	Common	03/16/2026	10000	300471.00
Richard B. Bartram 11711 N. Meridian Street, Suite 300 Carmel IN 46032	Common	03/25/2026	1061	30217.49
Richard B. Bartram 11711 N. Meridian Street, Suite 300 Carmel IN 46032	Common	04/22/2026	10423	341377.72
Richard B. Bartram 11711 N. Meridian Street, Suite 300 Carmel IN 46032	Common	05/01/2026	5000	159000.00
Richard B. Bartram 11711 N. Meridian Street Suite 300 Carmel IN 46032	Common	05/07/2026	10000	322050.00
Richard B. Bartram 11711 N. Meridian Street Suite 300 Carmel IN 46032	Common	05/08/2026	10000	379562.50
Richard B. Bartram 11711 N. Meridian Street Suite 300 Carmel IN 46032	Common	05/11/2026	22500	991901.00
Richard B. Bartram 11711 N. Meridian Street Suite 300 Carmel IN 46032	Common	05/13/2026	15000	554295.50
Richard B. Bartram 11711 N. Meridian Street, Suite 300 Carmel IN 46032	Common	06/09/2026	10833	321273.00

144: Remarks and Signature

Remarks
Date of Notice	06/10/2026
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/ Gerardo Ibarra-Munoz, as a duly authorized representative of Fidelity Brokerage Services LLC, as attorney-in-fact for Richard B. Bartram
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)