---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-215676"
form_type: "8-K"
ticker: "MBX"
cik: "0001776111"
company_name: "MBX Biosciences, Inc."
filed_at: "2026-05-11T23:59:59+00:00"
generated_at: "2026-05-14T18:48:42.344310+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.75
calibrated_materiality_score: 0.75
confidence: "high"
source: SEC EDGAR
---

# MBX 4291 Phase 1 shows 7% mean weight loss at 8 weeks; MBX 5765 nominated

## Summary
- Preliminary blinded data: mean weight loss 7% (range 0-16%) at 8 weeks in first MAD Part B cohort (n=8, incl. 2 placebo).
- PK profile supports once-monthly dosing: T1/2Cmax ~26 days, Tmax 13–14 days, dose-proportional PK from 15-180 mg.
- MBX 5765 nominated as amycretin prodrug (GLP-1/GIP/GCG/DACRA agonist); IND-enabling studies expected Q2 2026.
- Imapextide achieved POC in PBH Phase 2a (glucose nadir +34% at 200 mg); company will not pursue Phase 2b.
- 12-week MAD Part C data for MBX 4291 remain on track for Q4 2026.

## SEC filing metadata
- accession: 0001193125-26-215676
- form_type: 8-K
- ticker: MBX
- cik: 0001776111
- company_name: MBX Biosciences, Inc.
- filed_at: 2026-05-11T23:59:59+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.75
- calibrated_materiality_score: 0.75
- confidence: high
- sec_items: 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1776111/000119312526215676/0001193125-26-215676-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1776111/000119312526215676/mbx-20260511.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-215676
- JSON: https://secwatch.observer/filing/0001193125-26-215676.json
- Plain text: https://secwatch.observer/filing/0001193125-26-215676.txt

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