As filed with the Securities and Exchange Commission on September 21, 2023

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

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FORM S-8

REGISTRATION STATEMENT UNDER THE

SECURITIES ACT OF 1933

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APTOSE BIOSCIENCES INC.

(Exact name of registrant as specified in its charter)

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

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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 7(a)(2)(B) of the Securities Act. ☐

EXPLANATORY NOTE

REGISTRATION OF ADDITIONAL SECURITIES

This Registration Statement on Form S-8 (the “Registration Statement”) is being filed to register an additional 68,517 shares of common shares (“Shares”) of Aptose Biosciences Inc. to be issued pursuant to our 2021 Stock Incentive Plan as a result of the approval of the amendment to the 2021 Stock Incentive Plan at the Annual and Special Meeting of Shareholders held on May 23, 2023.

These additional Shares are securities of the same class as other securities for which a previous Registration Statement on Form S-8 was filed by us with the Securities and Exchange Commission (the “SEC”) on June 28, 2021 (File No. 333-257446) and for which a Post-Effective Amendment No. 1 to the aforementioned Registration Statement on Form S-8 was filed on April 1, 2022 (File No. 333-257446) (together, the “Previous Registration Statements”).  In accordance with General Instruction E of Form S-8, the contents of the Previous Registration Statements, including periodic reports filed after the Previous Registration Statements to maintain current information about our company, are incorporated by reference into this Registration Statement.

PART I

INFORMATION REQUIRED IN THE SECTION 10(A) PROSPECTUS

The documents containing the information specified in Part I of Form S-8 are not required to be filed with the Securities and Exchange Commission either as part of this registration statement or as prospectuses or prospectus supplements, pursuant to the Note to Part I of Form S-8 and Rule 424 under the Securities Act of 1933. The information required in the Section 10(a) prospectus is included in documents being maintained and delivered by Aptose Biosciences Inc. as required by Part I of Form S-8 and by Rule 428 under the Securities Act of 1933.

PART II

INFORMATION REQUIRED IN THE REGISTRATION STATEMENT

The following documents that have been filed by us with the SEC are incorporated in this registration statement by reference:

All other reports and documents subsequently filed by the Registrant pursuant to Sections 13(a), 13(c), 14 and 15(d) of the Exchange Act (other than Current Reports furnished under Item 2.02 or Item 7.01 of Form 8-K and exhibits furnished on such form that relate to such items) on or after the date of this Registration Statement and prior to the filing of a post-effective amendment to this Registration Statement which indicates that all securities offered have been sold or which deregisters all securities then remaining unsold, shall be deemed to be incorporated by reference herein and to be a part of this Registration Statement from the date of the filing of such reports and documents.

Any statement contained herein, in any amendment hereto or in a document incorporated by reference herein shall be deemed to be modified or superseded for purposes of this registration statement to the extent that a statement contained herein or in any subsequently-filed amendment to this registration statement or in any document that also is incorporated by reference herein modifies or supersedes such statement. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this registration statement

Item 4. Description of Securities.

Not applicable.

Item 5. Interest of Named Experts and Counsel.

Not applicable.

SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, Aptose Biosciences Inc. certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form S-8 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized in the City of San Diego, on this 21st day of September, 2023.

POWERS OF ATTORNEY

KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints William G. Rice and Fletcher Payne, and each of them, his true and lawful attorneys-in-fact and agents, each acting alone, with the powers of substitution and revocation, for him and in his name, place and stead, in any and all capacities, to sign this Registration Statement on Form S-8, and any and all amendments (including post-effective amendments) thereto, and to file the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto such attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite or necessary to be done in and about the premises, as fully to all intents and purposes as he might or could do in person, hereby ratifying and confirming that all such attorneys-in-fact and agents or any of them, or their substitute or substitutes, may lawfully do or cause to be done by virtue hereof.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed by the following persons in the capacities indicated below on September 21, 2023.

AUTHORIZED REPRESENTATIVE

Pursuant to the requirements of Section 6(a) of the Securities Act of 1933, the undersigned has signed this registration statement, solely in the capacity of the duly authorized representative of Aptose Biosciences Inc. in the United States, on September 21, 2023.

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