---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-25-023570"
form_type: "8-K"
ticker: "SION"
cik: "0002036042"
company_name: "Sionna Therapeutics, Inc."
filed_at: "2025-02-10T23:59:59+00:00"
generated_at: "2026-05-27T00:30:58.184139+00:00"
event_type: "other"
sentiment: "neutral"
materiality_score: 0.15
calibrated_materiality_score: 0.15
confidence: "high"
source: SEC EDGAR
---

# Sionna adopts amended charter/bylaws with IPO completion; eliminates written consent

## Summary
- Amended charter authorizes 500M common shares and 10M undesignated preferred shares; prior preferred series removed.
- Stockholder ability to act by written consent or call special meetings eliminated.
- Bylaws updated with advance notice procedures for stockholder proposals and director nominations.
- Changes were previously disclosed in the S-1 and became effective upon January 31, 2025 IPO closing.
- Governance structure now conforms to typical public company standards.

## SEC filing metadata
- accession: 0001193125-25-023570
- form_type: 8-K
- ticker: SION
- cik: 0002036042
- company_name: Sionna Therapeutics, Inc.
- filed_at: 2025-02-10T23:59:59+00:00
- event_type: other
- sentiment: neutral
- materiality_score: 0.15
- calibrated_materiality_score: 0.15
- confidence: high
- sec_items: 5.03, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/2036042/000119312525023570/0001193125-25-023570-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/2036042/000119312525023570/d886749d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-25-023570
- JSON: https://secwatch.observer/filing/0001193125-25-023570.json
- Plain text: https://secwatch.observer/filing/0001193125-25-023570.txt

## Key facts
- Governance Changes
  Sionna Therapeutics, Inc.: Amended and restated bylaws became effective, establishing procedures for stockholder actions at meetings, advance notice procedure for proposals and director nominations, and conforming to amended charter provisions.
  - Change: bylaw amendment
  source text: the amended and restated bylaws of the Company (the “Amended and Restated Bylaws”)
  evidence_url: https://www.sec.gov/Archives/edgar/data/2036042/000119312525023570/0001193125-25-023570-index.htm
- Governance Changes
  Sionna Therapeutics, Inc.: Fifth amended and restated certificate of incorporation filed, increasing authorized common stock to 500M shares, eliminating references to prior preferred stock series, authorizing 10M undesignated preferred shares, and eliminating stockholder ability to act by written consent and call special meet (effective 2025-01-31).
  - Change: charter amendment
  - Effective: 2025-01-31
  source text: the Company filed its fifth amended and restated certificate of incorporation (the “Amended and Restated Certificate”) with the Secretary of State of the State of Delaware on January 31, 2025
  evidence_url: https://www.sec.gov/Archives/edgar/data/2036042/000119312525023570/0001193125-25-023570-index.htm

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