Richard Bartram - 02 Feb 2026 Form 4 Insider Report for MBX Biosciences, Inc. (MBX)

Reporting relationship: Chief Financial Officer
Issuer ticker: MBX
Reported as of: 02 Feb 2026
Net transaction value: $0
SEC form: 4
Accepted by SEC: 03 Feb 2026, 16:16:29 UTC
Prior SEC filing: 05 Feb 2025
Source filing: View source filing
Reporting owner signature: /s/ Richard Bartram

Key filing fact

Richard Bartram filed Form 4 for MBX Biosciences, Inc. (MBX) on 03 Feb 2026.

Key facts

This page summarizes Richard Bartram's Form 4 filing for MBX Biosciences, Inc. (MBX).
2 reported transactions and 1 derivative row are listed below.
Accepted by SEC: 03 Feb 2026, 16:16.

Change

Previous filing in this sequence was filed on 05 Feb 2025.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (1)

CIK 0001723729 Primary reporting owner

Bartram Richard

Relationship: Chief Financial Officer
Address: C/O MBX BIOSCIENCES, INC., 11711 N. MERIDIAN STREET, SUITE 300, CARMEL
Signature: /s/ Richard Bartram
Signature date: 03 Feb 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

MBX transaction

Common Stock

Award

Transaction value: $0
Shares: +15,000
Change %
Price: $0.000000
Shares after: 15,000
Date: 02 Feb 2026
Ownership: Direct
Footnotes: F1

Reported derivative securities

Options, warrants, convertible securities, or similar derivative positions disclosed in the filing.

MBX transaction Derivative

Stock option (right to buy)

Award

Transaction value: $0
Shares: +70,000
Change %
Price: $0.000000
Shares after: 70,000
Date: 02 Feb 2026
Ownership: Direct
Underlying class: Common Stock
Underlying amount: 70,000
Exercise price: $39.07
Footnotes: F2

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 2 footnotes

Footnote F1

Represents the grant of restricted stock units (RSUs). The RSUs will vest over a four (4) year period in equal quarterly installments, subject to the Reporting Person's continued service on such vesting date.

Footnote F2

The shares underlying this option vest and become exercisable in forty eight (48) equal monthly installments, beginning on March 2, 2026, subject to the Reporting Person's continued service on such vesting date.