13D Filings
MBX Biosciences, Inc.
MBX
Amendment
Ownership

8.10%

Total Shares

3,619,474

Issuer CIK

1776111

CUSIP

55287L101

Event Date

Nov 5, 2025

Accepted

Nov 10, 2025, 05:08 PM

Reporting Persons (12)
Joint Filing

This is a joint filing. The reported shares may overlap between reporting persons and should not be summed.

NameType% of ClassAggregateSole VotingShared Voting
New Enterprise Associates 17, L.P.
Partnership
8.10%3,614,48603,614,486
NEA Partners 17, L.P.
Partnership
8.10%3,614,48603,614,486
NEA 17 GP, LLC
Other
8.10%3,614,48603,614,486
Forest Baskett
Individual
8.10%3,614,48603,614,486
Ali Behbahani
Individual
8.10%3,614,48603,614,486
Carmen Chang
Individual
8.10%3,614,48603,614,486
Anthony A. Florence, Jr.
Individual
8.10%3,614,48603,614,486
Mohamad H. Makhzoumi
Individual
8.10%3,614,48603,614,486
Edward T. Mathers
Individual
8.10%3,619,4744,9883,614,486
Scott D. Sandell
Individual
8.10%3,614,48603,614,486
Paul Walker
Individual
8.10%3,614,48603,614,486
Rick Yang
Individual
8.10%3,614,48603,614,486
Disclosure Items (7)

Security Title

Common Stock, par value $0.0001 per share

Issuer Name

MBX Biosciences, Inc.

Issuer Address

11711 N. Meridian Street, Carmel, IN, 46032

Filing Persons

New Enterprise Associates 17, L.P. ("NEA 17"); NEA Partners 17, L.P. ("NEA Partners 17"), which is the sole general partner of NEA 17; and NEA 17 GP, LLC ("NEA 17 LLC" and, together with NEA Partners 17, the "Control Entities"), which is the sole general partner of NEA Partners 17; and Forest Baskett ("Baskett"), Ali Behbahani ("Behbahani"), Carmen Chang ("Chang"), Anthony A. Florence, Jr. ("Florence"), Mohamad H. Makhzoumi ("Makhzoumi"), Edward T. Mathers ("Mathers"), Scott D. Sandell ("Sandell"), Paul Walker ("Walker"), and Rick Yang ("Yang") (together, the "Managers"). The Managers are the managers of NEA 17 LLC. The persons named in this Item 2 are referred to individually herein as "Reporting Person" and collectively as the "Reporting Persons."

Business Address

The address of the principal business office of NEA 17, each Control Entity and Sandell is New Enterprise Associates, 1954 Greenspring Drive, Suite 600, Timonium, MD 21093. The address of the principal business office of Baskett, Behbahani, Chang, Makhzoumi, Walker and Yang is New Enterprise Associates, 2855 Sand Hill Road, Menlo Park, CA 94025. The address of the principal business office of Florence and Mathers is New Enterprise Associates, 104 5th Avenue, 19th Floor, New York, NY 10011.

Principal Occupation

The principal business of NEA 17 is to invest in and assist growth-oriented businesses located principally in the United States. The principal business of NEA Partners 17 is to act as the sole general partner of NEA 17. The principal business of NEA 17 LLC is to act as the sole general partner of NEA Partners 17. The principal business of each of the Managers is to manage the Control Entities, NEA 17 and a number of affiliated partnerships with similar businesses.

Convictions

During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Citizenship

NEA 17 LLC is a limited liability company organized under the laws of the State of Delaware. NEA 17 and NEA Partners 17 are limited partnerships organized under the laws of the State of Delaware. Each of the Managers is a United States citizen.

Not applicable.

NEA 17 acquired the NEA 17 Shares for investment purposes. Depending on market conditions, its continuing evaluation of the business and prospects of the Issuer and other factors, NEA 17 and the other Reporting Persons may dispose of or acquire additional shares of the Issuer. Except as set forth above, none of the Reporting Persons has any present plans which relate to or would result in: (a) The acquisition by any person of additional securities of the Issuer, or the disposition of securities of the Issuer; (b) An extraordinary corporate transaction, such as a merger, reorganization or liquidation, involving the Issuer or any of its subsidiaries; (c) A sale or transfer of a material amount of assets of the Issuer or any of its subsidiaries; (d) Any change in the present board of directors or management of the Issuer, including any plans or proposals to change the number or term of directors or to fill any existing vacancies on the board; (e) Any material change in the present capitalization or dividend policy of the Issuer; (f) Any other material change in the Issuer's business or corporate structure; (g) Changes in the Issuer's charter, bylaws or instruments corresponding thereto or other actions which may impede the acquisition of control of the Issuer by any person; (h) Causing a class of securities of the Issuer to be delisted from a national securities exchange or to cease to be authorized to be quoted in an inter-dealer quotation system of a registered national securities association; (i) A class of equity securities of the Issuer becoming eligible for termination of registration pursuant to Section 12(g)(4) of the Securities Exchange Act of 1934; or (j) Any action similar to any of those enumerated above.

Percentage of Class

NEA 17 is the record owner of the NEA 17 Shares. As the general partner of NEA 17, NEA Partners 17 may be deemed to own beneficially the NEA 17 Shares. As the sole general partner of NEA Partners 17, NEA 17 LLC may be deemed to beneficially own the NEA 17 Shares. As members of NEA 17 LLC each of the Managers may be deemed to own beneficially the NEA 17 Shares. Each Reporting Person disclaims beneficially ownership of the NEA 17 Shares other than those shares which such person owns of record. As of November 10, 2025, Mathers is the record owner of options to purchase 4,988 shares of Common Stock (the "Mathers Option Shares"), exercisable within 60 days. The percentage of outstanding Common Stock of the Issuer which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Peron's cover sheet. Such percentage was calculated based on 44,902,302 shares of Common Stock reported by the Issuer to be outstanding as of November 3, 2025 on the Issuer's Form 10-Q filed with the Securities and Exchange Commission on November 6, 2025. The percentage set forth on the cover sheet for Mathers is calculated based on the shares described in the preceding sentence plus the Mathers Option Shares.

Number of Shares

Regarding the number of shares as to which such person has: (i) sole power to vote or to direct the vote: See line 7 of cover sheets (ii) shared power to vote or to direct the vote: See line 8 of cover sheets (iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets (iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets.

Transactions

None of the Reporting Persons have effected any transaction in the last 60 days.

Shareholders

No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, Common Stock beneficially owned by any of the Reporting Persons.

Date of 5% Ownership

Not applicable.

Not applicable.

Exhibit 1 - Agreement regarding filing of joint Schedule 13D. Exhibit 2 - Power of Attorney regarding filings under the Securities Exchange Act of 1934, as amended.