Ms. Susan Pietropaolo reports

APTOSE SELECTS ERNST & YOUNG GLOBAL LIMITED AS ITS NEW INDEPENDENT AUDITOR AND CALLS RECONVENED MEETING OF ITS SHAREHOLDERS

Aptose Biosciences Inc.'s board of directors has 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 had previously adjourned its annual and special meeting of shareholders held on May 27, 2025, for the purposes of completing its search for a successor independent auditor.

EY is a top-ranked global accounting firm that offers a complete spectrum of tax, assurance and advisory services; it has been selected due to its expertise, capabilities, and fit and understanding of the company's industry and business.

The company will reconvene its annual general and special meeting of shareholders on Aug. 22, 2025, at 10 a.m. Eastern Time, to vote on the appointment of EY and the authorization of the board to fix EY's remuneration.

All interested parties are invited to attend the reconvened meeting by live webcast. Only registered shareholders and duly appointed proxyholders as of the record date on April 22, 2025, will be entitled to vote and ask questions at the reconvened meeting.

Unless properly revoked, proxies previously completed, signed, dated and returned in respect of the original meeting will be effective at the reconvened meeting and shareholders do not need to vote again. New forms of proxies are not being distributed by the company. Registered shareholders of record at the close of business on April 22, 2025, who have not previously deposited a form of proxy may deposit a properly executed form of proxy no later than 48 hours, excluding weekends and holidays, before the reconvened meeting, or any adjournments or postponements thereof, with Computershare Investor Services Inc.: (i) through the Internet; (ii) by phone at 1-866-732-8683; or (iii) by mail to Computershare Investor Services, 320 Bay St., 14th floor, Toronto, Ont., M5H 4A6. Copies of the proxy statement and form of proxy have been filed on SEDAR+ and are available electronically on SEDAR+. Beneficial shareholders who wish to vote must follow the procedures and instructions received from their brokers or other intermediaries and contact their brokers or other intermediaries if they need assistance.

About Aptose Biosciences Inc.

Aptose Biosciences is a clinical-stage biotechnology company committed to developing precision medicines addressing unmet medical needs in oncology, with an initial focus on hematology. The company's lead clinical-stage, oral kinase inhibitor, tuspetinib (TUS), has demonstrated activity as a monotherapy and in combination therapy in patients with relapsed or refractory acute myeloid leukemia (AML) and is being developed as a front-line triplet therapy in newly diagnosed AML.

We seek Safe Harbor.