---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-26-341230"
form_type: "8-K"
ticker: "SION"
cik: "0002036042"
company_name: "Sionna Therapeutics, Inc."
filed_at: "2026-08-10T11:15:06+00:00"
generated_at: "2026-08-10T11:20:20.394943+00:00"
event_type: "other_material"
sentiment: "negative"
materiality_score: 0.85
calibrated_materiality_score: 0.85
confidence: "high"
source: SEC EDGAR
---

# Sionna's SION-719 Phase 2a misses sweat chloride endpoint; program halted as add-on

## Summary
- SION-719 Phase 2a missed key endpoint: -1.0 mmol/L placebo-adjusted sweat chloride change (p=0.7); not advancing as add-on to SOC.
- Phase 1 of SION-451 dual combos met safety/PK goals; SION-451 + SION-2222 preferred; evaluating next steps.
- Q2 cash $268.3M; plans to preserve capital while assessing SION-451 program.
- SION-719 was well tolerated; no serious AEs; potential confounders (variability, Trikafta exposure) under review.

## SEC filing metadata
- accession: 0001193125-26-341230
- form_type: 8-K
- ticker: SION
- cik: 0002036042
- company_name: Sionna Therapeutics, Inc.
- filed_at: 2026-08-10T11:15:06+00:00
- event_type: other_material
- sentiment: negative
- materiality_score: 0.85
- calibrated_materiality_score: 0.85
- confidence: high
- sec_items: 8.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/2036042/000119312526341230/0001193125-26-341230-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/2036042/000119312526341230/d135438d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-26-341230
- JSON: https://secwatch.observer/filing/0001193125-26-341230.json
- Plain text: https://secwatch.observer/filing/0001193125-26-341230.txt

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