# EDGAR Filing Document

**Accession Number:** 0000882361
**File Stem:** 0001193125-25-189846
**Filing Date:** 2025-8
**Character Count:** 8224
**Document Hash:** 7210ba11b5395d9c8157b9b1f25ddeb1
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-25-189846.hdr.sgml**: 20250827

**ACCESSION NUMBER**: 0001193125-25-189846

**CONFORMED SUBMISSION TYPE**: 8-K

**PUBLIC DOCUMENT COUNT**: 15

**CONFORMED PERIOD OF REPORT**: 20250822

**ITEM INFORMATION**: Changes in Registrant's Certifying Accountant

**ITEM INFORMATION**: Financial Statements and Exhibits

**FILED AS OF DATE**: 20250827

**DATE AS OF CHANGE**: 20250827

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Aptose Biosciences Inc.
- **CENTRAL INDEX KEY:** 0000882361
- **STANDARD INDUSTRIAL CLASSIFICATION:** BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** A6
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 8-K
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 001-32001
- **FILM NUMBER:** 251266295

**BUSINESS ADDRESS:**
- **STREET 1:** 66 WELLINGTON STREET WEST, SUITE 5300
- **STREET 2:** TD BANK TOWER BOX 48
- **CITY:** TORONTO
- **STATE:** A6
- **ZIP:** M5K 1E6
- **BUSINESS PHONE:** 310-849-8060

**MAIL ADDRESS:**
- **STREET 1:** 66 WELLINGTON STREET WEST, SUITE 5300
- **STREET 2:** TD BANK TOWER BOX 48
- **CITY:** TORONTO
- **STATE:** A6
- **ZIP:** M5K 1E6

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Aptose Biosciences Inc., (formerly LORUS THERAPEUTICS INC.)
- **DATE OF NAME CHANGE:** 20140905

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** LORUS THERAPEUTICS INC
- **DATE OF NAME CHANGE:** 19990308

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** IMUTEC PHARMA INC
- **DATE OF NAME CHANGE:** 19970113

?xml version='1.0' encoding='ASCII'? 8-K

### UNITED STATES

### SECURITIES AND EXCHANGE COMMISSION

#### Washington, D.C. 20549

### FORM 8-K

#### CURRENT REPORT

#### Pursuant to Section 13 or 15(d)

#### of the Securities Exchange Act of 1934

#### Date of Report (Date of earliest event reported): August 22, 2025

## APTOSE BIOSCIENCES INC.

#### (Exact name of registrant as specified in its charter)

---

| | | |
|:---|:---|:---|
| **Canada** | **001-32001** | **98-1136802** |
| **(State or Other Jurisdiction<br>of Incorporation)** | **(Commission**<br> **File Number)** | **(I.R.S. Employer<br>Identification No.)** |

---

#### 66 Wellington Street West, Suite 5300

#### TD Bank Tower, Box 48

#### Toronto, Ontario M5K 1E6

#### Canada

#### (Address of Principal Executive Offices) (Zip Code)
(647) 479-9828

#### (Registrant's telephone number, including area code)

#### (Former name or former address, if changed since last report)
Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

---

| | | |
|:---|:---|:---|
| **Title of each class** | **Trading<br>Symbol(s)** | **Name of each exchange<br>on which registered** |
| N/A | N/A | N/A |

---

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

------

---

| | |
|:---|:---|
| **Item 4.01.** | **Changes in Registrant's Certifying Accountant.**  |

---

On April 15, 2025, Aptose Biosciences Inc. (the "Company") previously announced that KPMG LLP ("KPMG"), the Company's independent registered public accounting firm, informed the Company that it would not stand for re-appointment for the Company's 2025 annual audit. KPMG agreed to continue to review the Company's quarterly interim financial results through the first two fiscal quarters of 2025. As a result, the Company conducted a competitive selection process to determine the Company's independent registered public accounting firm for the fiscal year ending December 31, 2025.

As a result of this process, 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. The Company reconvened its Annual General and Special Meeting of shareholders today to vote on the appointment of EY and the authorization of the Board to fix EY's remuneration, to which was subsequently approved.

During the Company's two most recent fiscal years ended December 31, 2024 and 2023, and the interim period through August 22, 2025, neither the Company nor anyone on its behalf has consulted EY with respect to either (i) the application of accounting principles to a specified transaction, either completed or proposed, or the type of audit opinion that might be rendered on the Company's financial statements, and neither a written report nor oral advice was provided to the Company that EY concluded was an important factor considered by the Company in reaching a decision as to any accounting, auditing or financial reporting issue; or (ii) any matter that was either the subject of a disagreement (as defined in Item 304(a)(1)(iv) of Regulation S-K and the related instructions) or a reportable event (as defined in Item 304(a)(1)(v) of Regulation S-K).

In accordance with Item 304(a)(3) of Regulation S-K, the Company provided KPMG with a copy of the disclosures it is making in this Current Report on Form 8-K and requested from KPMG a letter addressed to the Securities and Exchange Commission indicating whether it agrees with such disclosures. A copy of KPMG's letter dated August 21, 2025 is attached as Exhibit 16.1 hereto.

---

| | |
|:---|:---|
| **Item 9.01.** | **Financial Statements and Exhibits.**  |

---

(d) Exhibits

---

| | |
|:---|:---|
| **Exhibit<br>Number** | **Description** |
| 16.1 | [Letter from KPMG LLP to the Securities and Exchange Commission](d96555dex161.htm) |
| 104 | Cover Page Interactive Data File (embedded within the Inline XBRL document) |

---

------

#### SIGNATURE
Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

---

| | | |
|:---|:---|:---|
|  | **Aptose Biosciences Inc.** | **Aptose Biosciences Inc.** |
| Date: August 27, 2025 | By: | /s/ William G. Rice |
|  |  | William G. Rice, Ph.D. |
|  |  | President and Chief Executive Officer |

---

## Exhibit 16.1

**Exhibit 16.1**![LOGO](g96555g0827035507386.jpg)

KPMG LLP

100 New Park Place, Suite 1400

Vaughan, ON L4K 0J3

Tel 905-265 5900

Fax 905-265 6390

www.kpmg.ca

To Securities and Exchange Commission

Washington, DC

August 21, 2025

Dear Sir/Madam

**Re: Notice of Change of Auditors of Aptose Biosciences Inc.** 

We have read the statements made by Aptose Biosciences Inc. (the "Company") set forth in Item 4.01 "Changes in Registrant's Certifying Accountant" on its Form 8-K dated August 22, 2025. We are in agreement with the statements contained in such Notice insofar as they relate to our firm. We are not in a position to agree or disagree with other statements of the Company contained therein.

Yours very truly,

![LOGO](g96555g0827035507683.jpg)

August 21, 2025

KPMG LLP, an Ontario limited liability partnership and member firm of the KPMG global

organization of independent member firms affiliated with KPMG International Limited, a private

English company limited by guarantee.

KPMG Canada provides services to KPMG LLP.

Document classification: KPMG Confidential