Form 144 notice: 10,000 common shares proposed for sale

MBX proposed the sale of 10,000 shares of Common Stock via a Form 144 notice.

Rhea-AI Filing Summary

MBX proposed the sale of 10,000 shares of Common Stock via a Form 144 notice. The filing shows 7,500 shares from an option granted 04/20/2022 and 2,500 shares from an option granted 11/07/2022, with transactions routed through Fidelity Brokerage Services LLC on 03/16/2026. The filing lists an aggregate value of $300,470.62.

Insights

Securities Compliance Attorney

Form 144 notifies the market of a proposed sale under Rule 144.

Form 144 is a notice of a proposed sale by an affiliate or control person; it does not itself execute the sale. The filing lists 10,000 shares to be sold and identifies the broker and option grant dates.

Timing and completion depend on volume, holding periods, and Rule 144 conditions; subsequent filings will report actual dispositions.

FAQ

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

What does MBX's Form 144 filing mean?

It notifies the market of a proposed sale of 10,000 common shares under resale rules. The notice lists share sources, broker, and dates but does not itself complete the sale; subsequent reports disclose whether the shares were actually sold.

How many shares and from what sources are listed in MBX's filing?

The filing lists a total of 10,000 shares: 7,500 from an option granted on 04/20/2022 and 2,500 from an option granted on 11/07/2022, offered through Fidelity Brokerage Services LLC.

What price or aggregate value is reported in the MBX Form 144?

The Form 144 excerpt reports an aggregate value of $300,470.62 associated with the proposed sale. This figure is listed on the filing and reflects the reported value tied to the 10,000 shares on 03/16/2026.

Does MBX's Form 144 mean the shares have already been sold?

No. The Form 144 is a notice of an intended sale, not proof of execution. It shows the broker and proposed sources; actual sale completion and any proceeds will be disclosed in later transaction reports if and when the sale occurs.

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

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Accepted by SEC EDGAR 03/16/2026 - 02:47 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	10000	300470.62	47510243	03/16/2026	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	03/16/2026	Option Granted - 04/20/2022	Issuer			7500	03/16/2026	Cash
Common	03/16/2026	Option Granted - 11/07/2022	Issuer			2500	03/16/2026	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

Nothing to Report

144: Remarks and Signature

Remarks
Date of Notice	03/16/2026
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)