APTE BIOS : Aptose Corporate Presentation September 2023

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P R E C I S I O N O N C O L O G Y F O R T H E R A P I E S O F T O M O R R O W	NASDAQ: APTO
		T SX: APS

C O N F I D E N T I A L

Aptose Disclosure

This presentation does not, and is not intended to, constitute or form part of, and should not be construed as, an offer or invitation for the sale or purchase of, or a solicitation of an offer to purchase, subscribe for or otherwise acquire, any securities, businesses and/or assets of any entity, nor shall it or any part of it be relied upon in connection with or act as any inducement to enter into any contract or commitment or investment decision whatsoever.

This presentation contains forward-lookingstatements, which reflect APTOSE Biosciences Inc.'s (the "Company") current expectations, estimates and projections regarding future events, including statements relating to our business strategy, our clinical development plans, our ability to obtain the substantial capital we require, our plans to secure strategic partnerships and to build our pipeline, our clinical trials and their projected timeline, the efficacy and toxicity of our product candidates, potential new intellectual property, our plans, objectives,

expectations and intentions; and other statements including words such as "anticipate", "contemplate", "continue", "believe", "plan", "estimate", "expect", "intend", "will", "should", "may", and other similar expressions. Such statements constitute forward-looking statements within the meaning of securities laws.

Although the Company believes that the views reflected in these forward-looking statements are reasonable, such statements involve significant risks and uncertainties, and undue reliance should not be placed on such statements. Certain material factors or assumptions are applied in making these forward-looking statements, and actual results may differ materially from those statements. Those factors and risks include, but are not limited to, our ability to raise the funds necessary to continue our operations, changing market conditions, the successful and timely completion of our clinical studies including delays, the demonstration of safety and efficacy of our drug candidates, our ability to recruit patients, the establishment and maintenance of corporate alliances, the market potential of our product candidates, the impact of competitive products and pricing, new product development, changes in laws and regulations, uncertainties related to the regulatory approval process and other risks detailed from time to time in the Company's ongoing quarterly filings and annual reports.

Forward-looking statements contained in this document represent views only as of the date hereof and are presented for the purpose of assisting potential investors in understanding the Company's business and may not be appropriate for other purposes. The Company does not undertake to update any forward-looking statements, whether written or oral, that may be made from time to time by or on its behalf, except as required under applicable securities legislation. Investors should read the Company's continuous disclosure documents available at www.sedar.comand EDGAR at www.sec.gov/edgar.shtml,especially the risk factors detailed therein.

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C O N F I D E N T I A L

Aptose Biosciences is a precision oncology company developing oral targeted agents to treat hematologic malignancies

Acute myeloid leukemia, AML Myelodysplastic syndromes, MDS

(Nasdaq: APTO ; TSX: APS)

Aptose Investment Highlights

Tuspetinib (TUS) lead agent: Once daily, oral, kinase inhibitor designed to selectively suppress a handful of kinases that drive key oncogenic signaling pathways operative in AML

Mechanistic Precision

SYK FLT3WT/MUT KITMUT JAK1/2 RSK1/2

C O N F I D E N T I A L

Aptose Biosciences is a precision oncology company developing oral targeted agents to treat hematologic malignancies

Acute myeloid leukemia, AML Myelodysplastic syndromes, MDS

(Nasdaq: APTO ; TSX: APS)

Aptose Investment Highlights

Tuspetinib (TUS) lead agent: Ideal drug for combination therapies in AML

• AML treatment strategies quickly shifting to combination therapies
• Combination therapies deliver greatest commercial and medical impact
• • Represent 98% of tuspetinib commercial forecasts
  • Projected faster accruals and earlier regulatory approvals
  • Can deliver higher response rates and more durable responses
• TUS/VEN/HMA ideal combination therapy planned for 1L AML
• TUS/VEN clinical responses in R/R AML with Prior-VEN failure
• • Presents accelerated approval path for TUS/VEN in R/R AML
• Annual commercial forecast > $2.5 Bn for AML and HR-MDS

$25M Keystone and $7M Hanmi capital investments

Value-driving clinical milestones during 2H2023

C O N F I D E N T I A L

Review Clinical Path and Findings that Support Tuspetinib Combination Strategy

EOP1 Meeting with FDA

• Successful meeting and outcomes
• RP2D = 80mg once daily
• All approval paths remain available

Dose Escalation Ph 1/2 Trial in R/R AML

• Demonstrated single agent efficacy
• Established "contribution of component" that TUS brings to combination therapy
• Favorable safety and tolerability

APTIVATE Expansion Trial in R/R AML

• TUS or TUS/VEN doublet
• TUS/VEN safe and highly active → including Prior-VEN failure subgroup that is difficult-to-treat

Finding Differentiates TUS/VEN Doublet from Other Therapies

• TUS/VEN impressive Response Rate in Prior-VEN AML
• High unmet need │ Dismal response to salvage therapy
• 90%+ R/R AML patients entering our APTIVATE trial
• Enables a clear Accelerated Approval path

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C O N F I D E N T I A L