Ms. Susan Pietropaolo reports

APTOSE BIOSCIENCES PROVIDES UPDATE ON REVERSE STOCK SPLIT

Aptose Biosciences Inc. effected a reverse stock split on May 24, 2023, at a ratio of 15-to-1.

Both the Nasdaq Capital Market and the Toronto Stock Exchange have approved the reverse stock split, and have informed the company that its common shares will commence trading on a postreverse stock split basis at market open on Tuesday, June 6, 2023. The common shares continue to trade on the Nasdaq and the TSX under the existing ticker symbols. The new CUSIP number for the common shares is 03835T309 and the new ISIN is CA03835T3091.

As previously announced, the reverse stock split, at a ratio in the range between 10-to-1 and 20-to-1, was approved at the company's annual and special meeting of shareholders held on May 23, 2023, and is described in the proxy statement dated April 18, 2023. The company's board of directors then approved a ratio of 15-to-1 on May 23, 2023.

As a result of the reverse stock split, every 15 common shares issued and outstanding were automatically reclassified into one new common share. No fractional common shares will be issued as a result of the reverse stock split and shareholders will not receive any compensation in lieu thereof.

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 small-molecule cancer therapeutics pipeline includes products designed to provide single-agent efficacy and to enhance the efficacy of other anti-cancer therapies and regimens without overlapping toxicities. The company has two clinical-stage oral kinase inhibitors under development for hematologic malignancies: tuspetinib (HM43239), an oral, myeloid kinase inhibitor being studied as monotherapy and in combination therapy in the Aptivate international phase 1/2 expansion trial in patients with relapsed or refractory acute myeloid leukemia (AML); and luxeptinib (CG-806), an oral, dual lymphoid and myeloid kinase inhibitor in phase 1 a/b stage development for the treatment of patients with relapsed or refractory hematologic malignancies.

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