---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-079286"
form_type: "8-K"
ticker: "MBX"
cik: "0001776111"
company_name: "MBX Biosciences, Inc."
filed_at: "2026-02-27T23:59:59+00:00"
generated_at: "2026-05-15T23:08:37.782707+00:00"
event_type: "leadership"
sentiment: "negative"
materiality_score: 0.65
calibrated_materiality_score: 0.65
confidence: "high"
source: SEC EDGAR
---

# MBX Biosciences CFO Richard Bartram resigns; John Smither named interim CFO

## Summary
- CFO Richard Bartram resigns effective March 15, 2026; will serve as consultant post-resignation.
- John Smither appointed Interim CFO effective March 16, 2026; base salary $325k, target bonus 40%, $25k sign-on.
- Lease entered for 13,642 sqft office/lab in Burlington, MA; aggregate base rent ~$3.4M over 4-year term.
- Departure not due to dispute; search for permanent CFO underway.

## SEC filing metadata
- accession: 0001193125-26-079286
- form_type: 8-K
- ticker: MBX
- cik: 0001776111
- company_name: MBX Biosciences, Inc.
- filed_at: 2026-02-27T23:59:59+00:00
- event_type: leadership
- sentiment: negative
- materiality_score: 0.65
- calibrated_materiality_score: 0.65
- confidence: high
- sec_items: 1.01, 9.01, 5.02
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1776111/000119312526079286/0001193125-26-079286-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1776111/000119312526079286/mbx-20260224.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-079286
- JSON: https://secwatch.observer/filing/0001193125-26-079286.json
- Plain text: https://secwatch.observer/filing/0001193125-26-079286.txt

## Key facts
- Material Agreements
  MBX Biosciences, Inc. entered into Lease Agreement with 5 Burlington Woods, LLC valued at approximately $3.4 million (effective 2026-02-24).
  - Action: entry
  - Agreement: lease
  - Counterparty: 5 Burlington Woods, LLC
  - Value: approximately $3.4 million
  - Effective: 2026-02-24
  source text: On February 24, 2026, MBX Biosciences, Inc. (the “Company”) entered into a lease agreement (the “Lease Agreement”) with 5 Burlington Woods, LLC ("5 Burlington Woods") to lease approximately 13,642 square feet of new office and laboratory space in Burlington, MA
  evidence_url: https://www.sec.gov/Archives/edgar/data/1776111/000119312526079286/0001193125-26-079286-index.htm

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.