BlackRock (MBX) discloses 5.5% beneficial ownership in MBX Biosciences common stock

Rhea-AI Filing Summary

BlackRock, Inc. reports beneficial ownership of common stock of MBX Biosciences Inc. on a Schedule 13G. BlackRock reports beneficial ownership of 2,628,181 shares of MBX common stock, representing 5.5% of the outstanding class as of the reporting date.

BlackRock has sole voting power over 2,583,923 shares and sole dispositive power over 2,628,181 shares, with no shared voting or dispositive power. Various underlying persons have rights to dividends or sale proceeds, but no individual person has an interest in more than five percent of MBX’s outstanding common shares.

Key Figures

Beneficial ownership: 2,628,181 shares Percent of class: 5.5% Sole voting power: 2,583,923 shares +3 more

6 metrics

Beneficial ownership 2,628,181 shares Common stock of MBX Biosciences Inc. beneficially owned by BlackRock, Inc.

Percent of class 5.5% Percentage of MBX Biosciences Inc. common stock class held by BlackRock, Inc.

Sole voting power 2,583,923 shares Shares of MBX over which BlackRock, Inc. has sole power to vote

Shared voting power 0 shares Shares of MBX over which BlackRock, Inc. has shared voting power

Sole dispositive power 2,628,181 shares Shares of MBX over which BlackRock, Inc. has sole power to dispose

Shared dispositive power 0 shares Shares of MBX over which BlackRock, Inc. has shared power to dispose

Key Terms

Schedule 13G, beneficially owned, sole voting power, sole dispositive power, +1 more

5 terms

Schedule 13G regulatory

"In accordance with SEC Release No. 34-39538 (January 12, 1998), this reflects the securities beneficially owned"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

beneficially owned financial

"this reflects the securities beneficially owned, or deemed to be beneficially owned, by certain business units"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

sole voting power financial

"Sole Voting Power 2,583,923.00"

Sole voting power is the exclusive right to cast votes attached to a shareholder’s stock without needing approval from anyone else. Like holding the only remote control for a TV, it lets that holder decide corporate matters such as board members, mergers, and policy changes, making it important to investors because it concentrates control and can strongly influence a company’s strategy and the value of its shares.

sole dispositive power financial

"Sole Dispositive Power 2,628,181.00"

Sole dispositive power is the exclusive legal authority to decide what happens to a security — for example, whether to sell, transfer, or retain shares — without needing anyone else’s permission. Investors care because it signals who truly controls the economic outcome of an investment: like holding the only key to a safe, the holder can realize gains or losses and may trigger regulatory reporting, insider rules, or influence over corporate ownership.

percent of class financial

"Percent of class: 5.5 %"

Percent of class is the portion of a specific category of securities—such as a company’s common shares, preferred shares, or a bond series—that takes part in or approves a corporate action (vote, consent, tender, etc.). Investors watch this number because it reveals how much support or opposition exists within that particular shareholder group; like counting how many members of a club back a proposal, it can determine whether a plan passes or how influence is distributed.

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

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Available on EDGAR 07/29/2026 - 03:21 PM Accepted by SEC EDGAR 07/29/2026 - 03:19 PM Learn about SEC filing dates

FAQ

What percentage of MBX (MBX) common stock does BlackRock, Inc. report owning?

BlackRock, Inc. reports beneficial ownership of 5.5% of MBX Biosciences Inc.’s common stock, based on 2,628,181 shares held. This level of ownership triggers a Schedule 13G institutional holder filing.

How many MBX (MBX) shares does BlackRock, Inc. have voting power over?

BlackRock, Inc. has sole voting power over 2,583,923 shares of MBX Biosciences Inc. and no shared voting power. This means BlackRock alone can vote those shares or direct how they are voted.

What is BlackRock, Inc.’s dispositive power over MBX (MBX) shares?

BlackRock, Inc. reports sole dispositive power over 2,628,181 MBX shares and no shared dispositive power. Dispositive power reflects the authority to dispose of or direct the disposition of those shares.

Why did BlackRock, Inc. file a Schedule 13G for MBX (MBX)?

BlackRock, Inc. filed a Schedule 13G because it beneficially owns more than 5% of MBX Biosciences Inc.’s common stock, specifically 2,628,181 shares, which meets the SEC reporting threshold for certain institutional investors.

Do any individual investors hold more than 5% of MBX (MBX) through BlackRock’s position?

The filing states that various persons have rights to dividends or sale proceeds from MBX shares held by BlackRock’s units, but no one person’s interest exceeds five percent of MBX’s total outstanding common shares.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

MBX BIOSCIENCES INC

(Name of Issuer)

Common Stock

(Title of Class of Securities)

55287L101

(CUSIP Number)

06/30/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 55287L101

1

Names of Reporting Persons

BlackRock, Inc.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 2,583,923.00
6	Shared Voting Power 0.00
7	Sole Dispositive Power 2,628,181.00
8	Shared Dispositive Power 0.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

2,628,181.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

5.5 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MBX BIOSCIENCES INC
(b)	Address of issuer's principal executive offices: 11711 N. Meridian Street, Suite 300 Carmel IN 46032
Item 2.
(a)	Name of person filing: BlackRock, Inc. In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by certain business units (collectively, the "Reporting Business Units") of BlackRock, Inc. and its subsidiaries and affiliates. It does not include securities, if any, beneficially owned by other business units whose beneficial ownership of securities are disaggregated from that of the Reporting Business Units in accordance with such release.
(b)	Address or principal business office or, if none, residence: BlackRock, Inc., 50 Hudson Yards New York, NY 10001
(c)	Citizenship: See Item 4 of Cover Page
(d)	Title of class of securities: Common Stock
(e)	CUSIP Number(s): 55287L101
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 2628181
(b)	Percent of class: 5.5 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 2583923
	(ii) Shared power to vote or to direct the vote: 0
	(iii) Sole power to dispose or to direct the disposition of: 2628181
	(iv) Shared power to dispose or to direct the disposition of: 0
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. Various persons have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of the common stock of MBX BIOSCIENCES INC. No one person's interest in the common stock of MBX BIOSCIENCES INC is more than five percent of the total outstanding common shares.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. See Exhibit 99
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under § 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

BlackRock, Inc.

Signature:	Spencer Fleming
Name/Title:	Managing Director
Date:	07/29/2026

Exhibit Information

Exhibit 24: Power of Attorney Exhibit 99: Item 7