---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-25-189846"
form_type: "8-K"
ticker: "APTOF"
cik: "0000882361"
company_name: "Aptose Biosciences Inc."
filed_at: "2025-08-27T23:59:59+00:00"
generated_at: "2026-05-17T09:52:14.569705+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.5
calibrated_materiality_score: 0.5
confidence: "high"
source: SEC EDGAR
---

# Aptose Biosciences appoints EY as independent auditor, replacing KPMG

## Summary
- KPMG informed company it would not stand for re-appointment for 2025 annual audit.
- Board approved EY as independent auditor; shareholders voted approval at reconvened meeting on August 22, 2025.
- No disagreements or reportable events between company and KPMG during past two fiscal years.
- KPMG letter agreeing with disclosures attached as Exhibit 16.1.

## SEC filing metadata
- accession: 0001193125-25-189846
- form_type: 8-K
- ticker: APTOF
- cik: 0000882361
- company_name: Aptose Biosciences Inc.
- filed_at: 2025-08-27T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.5
- calibrated_materiality_score: 0.5
- confidence: high
- sec_items: 4.01, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/882361/000119312525189846/0001193125-25-189846-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/882361/000119312525189846/d96555d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-25-189846
- JSON: https://secwatch.observer/filing/0001193125-25-189846.json
- Plain text: https://secwatch.observer/filing/0001193125-25-189846.txt

## Key facts
- Auditor Changes
  Aptose Biosciences Inc. engaged Ernst & Young LLP as its auditor.
  - Action: engagement
  - Auditor: Ernst & Young LLP
  source text: on August 1, 2025 the Company announced that the Board of Directors (the “Board”) unanimously approved the selection of Ernst & Young LLP (“EY”) as the Company’s independent registered public accounting firm to serve as the Company’s independent auditor.
  evidence_url: https://www.sec.gov/Archives/edgar/data/882361/000119312525189846/0001193125-25-189846-index.htm

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