EX-5.2

Exhibit 5.2

December 11, 2023

Aptose Biosciences Inc.

251 Consumers Road, Suite 1105

Toronto, Ontario, M2J 4R3

Re: Registration Statement on Form S-1 (File No. 333-275870)

Ladies and Gentlemen:

We have acted as United States counsel to Aptose Biosciences Inc., a Canadian corporation (the “Corporation”), in connection with a Registration Statement on Form S-1 (as amended or supplemented, the “Registration Statement”) filed by the Corporation with the Securities and Exchange Commission (the “Commission”) under the Securities Act of 1933, as amended (the “Securities Act”), relating to the registration by the Corporation of up to $10,000,000 of securities consisting of (a) (i) up to 4,098,361 common shares, no par value (“Offered Shares”), or (ii) in lieu thereof, up to 4,098,361 pre-funded warrants (the “Pre-Funded Warrants”) to purchase up to 4,098,361 Offered Shares, and (b) up to 4,098,361 warrants (the “Warrants”) to purchase up to 4,098,361 common shares.

We have examined such documents and have reviewed such questions of law as we have considered necessary or appropriate for the purposes of our opinions set forth below. In rendering our opinions set forth below, we have assumed the authenticity of all documents submitted to us as originals, the genuineness of all signatures and the conformity to authentic originals of all documents submitted to us as copies. We have also assumed the legal capacity for all purposes relevant hereto of all natural persons. As to questions of fact material to our opinions, we have relied upon certificates or comparable documents of officers and other representatives of the Corporation and of public officials.

Based on the foregoing, we are of the opinion that the Pre-Funded Warrants and Warrants, when duly executed by the Corporation and duly delivered to the purchasers thereof against payment therefor as described in the Registration Statement, will constitute valid and binding obligations of the Corporation, enforceable against the Corporation in accordance with their terms.

(a) Our opinions set forth above are subject to the effect of any applicable bankruptcy, insolvency, reorganization, moratorium or similar law relating to or affecting creditors’ rights generally (including, without limitation, fraudulent conveyance laws).

(b) Our opinions set forth in paragraphs above are subject to the effect of general principles of equity, including, without limitation, concepts of materiality, reasonableness, good faith and fair dealing and the possible unavailability of specific performance or injunctive relief, regardless of whether considered in a proceeding in equity or at law.

(c) Our opinions set forth in paragraphs above are subject to limitations regarding the availability of indemnification and contribution where such indemnification or contribution may be limited by applicable law or the application of principles of public policy.

(d) We express no opinion as to the enforceability of (i) provisions that relate to choice of law, forum selection or submission to jurisdiction (including, without limitation, any express or implied waiver of any objection to venue in any court or of any objection that a court is an inconvenient forum) to the extent that the validity, binding effect or enforceability of any such provision is to be determined by any court other than a state court of the State of New York, (ii) waivers by the Corporation of any statutory or constitutional rights or remedies, (iii) terms which excuse any person or entity from liability for, or require the Corporation to indemnify such person or entity against, such person’s or entity’s negligence or willful misconduct or (iv) obligations to pay any prepayment premium, default interest rate, early termination fee or other form of liquidated damages, if the payment of such premium, interest rate, fee or damages may be construed as unreasonable in relation to actual damages or disproportionate to actual damages suffered as a result of such prepayment, default or termination.