secwatch.observer — SEC 8-K summary
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Issuer:     MBX Biosciences, Inc. (MBX)
CIK:        0001776111
Form:       8-K
Filed at:   2026-05-11T23:59:59+00:00
Accession:  0001193125-26-215676
Event type: other_material
Sentiment:  positive
Materiality: 0.75
Item codes: 7.01, 8.01, 9.01
LLM model:  deepseek-v4-flash:cloud@v2

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

Source:
  EDGAR index:    https://www.sec.gov/Archives/edgar/data/1776111/000119312526215676/0001193125-26-215676-index.htm
  Primary doc:    https://www.sec.gov/Archives/edgar/data/1776111/000119312526215676/mbx-20260511.htm
  HTML page:      https://secwatch.observer/filing/0001193125-26-215676

License: Source filings: public domain (SEC EDGAR). Summaries (headline + bullets): CC-BY-4.0; attribute https://secwatch.observer