SEC FORM 3

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

CORNELIUS JAMES M

(Last)

(First)

(Middle)

C/O MBX BIOSCIENCES, INC.

11711 N. MERIDIAN STREET, SUITE 300

(Street)

CARMEL

46032

(City)

(State)

(Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
09/12/2024

3. Issuer Name and Ticker or Trading Symbol
MBX Biosciences, Inc. [ MBX ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

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

5. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
1. Title of Derivative Security (Instr. 4)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
Stock Option (right to buy)	⁽¹⁾	08/31/2030	Common Stock	16,636	$0.49	D
Stock Option (right to buy)	⁽²⁾	01/30/2034	Common Stock	22,641	$9.14	D
Series A Convertible Preferred Stock	⁽³⁾	⁽³⁾	Common Stock	82,686	⁽³⁾	D
Series B Convertible Preferred Stock	⁽³⁾	⁽³⁾	Common Stock	19,396	⁽³⁾	D

Explanation of Responses:

1. 1/48th of the shares underlying this option vest and become exercisable in substantially equal monthly installments on each monthly anniversary of September 1, 2020, subject to the Reporting Person's continued service on each such vesting date.

2. 1/48th of the shares underlying this option vest and become exercisable in substantially equal monthly installments on each monthly anniversary of January 31, 2024, subject to the Reporting Person's continued service on each such vesting date.

3. Each share of Series A Convertible Preferred Stock and Series B Convertible Preferred Stock (together, the "Preferred Stock") is convertible into Common Stock on a one-for-12.0221 basis at any time at the option of the holder, and will automatically convert into the number of shares shown in Column 3 immediately prior to the closing of the Issuer's initial public offering. The Preferred Stock has no expiration date.

Remarks:

Exhibit 24 - Power of Attorney

	/s/ Richard Bartram, attorney-in-fact	09/12/2024
	** 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 5 (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.