---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-369674"
form_type: "8-K"
ticker: "MBX"
cik: "0001776111"
company_name: "MBX Biosciences, Inc."
filed_at: "2026-08-27T12:34:34+00:00"
generated_at: "2026-08-27T12:35:03.745150+00:00"
event_type: "other_material"
sentiment: "positive"
materiality_score: 0.7
calibrated_materiality_score: 0.7
confidence: "high"
source: SEC EDGAR
---

# MBX Biosciences doses first patient in Phase 3 oPTimize trial of canvuparatide for hypoparathyroidism

## Summary
- First patient dosed in pivotal Phase 3 oPTimize trial (NCT07699471) of once-weekly canvuparatide in chronic hypoparathyroidism.
- Trial enrolls ~160 adults, randomized 3:1 canvuparatide vs placebo over 26-week double-blind period, then 78-week open-label extension.
- Primary endpoint: composite responder at Week 26 (normal serum calcium, no active vitamin D, calcium ≤600 mg/day, no dose increase).
- Builds on positive Phase 2 Avail results showing normalized serum calcium, reduced urinary calcium, restored bone metabolism, increased eGFR.
- Canvuparatide administered once weekly using commercial-intent device; CEO cites potential as new standard of care.

## SEC filing metadata
- accession: 0001193125-26-369674
- form_type: 8-K
- ticker: MBX
- cik: 0001776111
- company_name: MBX Biosciences, Inc.
- filed_at: 2026-08-27T12:34:34+00:00
- event_type: other_material
- sentiment: positive
- materiality_score: 0.7
- calibrated_materiality_score: 0.7
- confidence: high
- sec_items: 7.01, 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1776111/000119312526369674/0001193125-26-369674-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1776111/000119312526369674/mbx-20260827.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-369674
- JSON: https://secwatch.observer/filing/0001193125-26-369674.json
- Plain text: https://secwatch.observer/filing/0001193125-26-369674.txt

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