---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-25-184706"
form_type: "8-K"
ticker: "SEPN"
cik: "0001984086"
company_name: "Septerna, Inc."
filed_at: "2025-08-21T23:59:59+00:00"
generated_at: "2026-05-17T10:57:52.844850+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.5
calibrated_materiality_score: 0.5
confidence: "high"
source: SEC EDGAR
---

# Septerna doses first participants in Phase 1 trial of SEP-631 for mast cell-driven diseases

## Summary
- SEP-631 is an oral small molecule MRGPRX2 negative allosteric modulator (NAM) targeting chronic spontaneous urticaria (CSU) and other mast cell-driven diseases.
- Phase 1 SAD/MAD trial will evaluate safety, tolerability, PK and PD in up to ~150 healthy volunteers; SAD dosing is underway.
- PD assessed via icatibant skin challenge in the MAD portion; no financial or guidance updates provided.
- Septerna highlights unmet need in CSU where many patients do not respond to antihistamines.

## SEC filing metadata
- accession: 0001193125-25-184706
- form_type: 8-K
- ticker: SEPN
- cik: 0001984086
- company_name: Septerna, Inc.
- filed_at: 2025-08-21T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.5
- calibrated_materiality_score: 0.5
- confidence: high
- sec_items: 7.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/1984086/000119312525184706/0001193125-25-184706-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/1984086/000119312525184706/d51455d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-25-184706
- JSON: https://secwatch.observer/filing/0001193125-25-184706.json
- Plain text: https://secwatch.observer/filing/0001193125-25-184706.txt

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