Plan of Arrangement

On November 18, 2025, the Company entered into a definitive arrangement agreement, as amended or restated from time to time (the “Arrangement Agreement”), with Hanmi and HS North America Ltd., a wholly owned subsidiary of Hanmi (“Hanmi Purchaser” and together with Hanmi, the "Hanmi Purchasers") pursuant to a plan of arrangement of the Company under the Canada Business Corporations Act (the "Arrangement") whereby Hanmi Purchaser will acquire all of the issued and outstanding Common Shares of the Company that are not currently owned or controlled by the Hanmi Purchasers or their respective affiliates. Pursuant to the Arrangement, each shareholder of the Company will receive an amount in cash equal to C$2.41 for each Common Share of the Company held by such shareholder. All incentive securities and warrants of the Company, whether vested or unvested, outstanding on the effective date of the Arrangement shall be deemed (i) cancelled and/or (ii) surrendered and cancelled, and each holder of options, restricted stock units or warrants shall cease to be a holder of such options, restricted stock units or warrants. Following the completion of the Arrangement, the Company’s securities will be delisted from the Toronto Stock Exchange.

On February 23, 2026, the Arrangement Agreement was amended and restated to, among other things, extend the outside date for completing the Arrangement from March 15, 2026 to June 30, 2026. On March 31, 2026, shareholders of the Company approved the Arrangement at a special meeting of shareholders held for such purpose. In addition, in connection with the Arrangement, shareholders of the Company approved to continue the Company from the Canada Business Corporations Act to the Business Corporations Act (Alberta), and such continuance was effected on March 31, 2026. The Arrangement is expected to close in May 2026, subject to the satisfaction of customary closing conditions and certain Korean regulatory approvals.

Transactions with Hanmi Pharmaceutical Co. Ltd.

On February 23, 2026, the Company and Hanmi entered into the Second Amended Facility Agreement, pursuant to which Hanmi provided an additional uncommitted facility ("Facility #3") for up to $11.1 million, administered through multiple advances for the purpose of the continued clinical development of tuspetinib and to fund operations of the Company. Advances under the Second Amended Facility Agreement may be provided in one or more (but no more than six advances) until May 31, 2026. No single advance shall be for an amount in excess of $2.0 million or for an amount that is less than $0.5 million. Additionally, Hanmi may cancel availability under the Second Amended Facility Agreement at any time without notice, acting solely at its discretion. Any amounts repaid under the Second Amended Facility Agreement may not be re-borrowed. As of March 31, 2026, Aptose received a total of $4.0 million under the Second Amended Facility Agreement with additional advances received subsequent to March 31, 2026 (see Note 11). Amounts outstanding pursuant to the Second Amended Facility Agreement, including accrued and unpaid interest, are repayable in full on August 31, 2028. Unpaid principal with respect to each advance shall accrue interest at a rate of 6% per annum.

During the three months ended March 31, 2026 and 2025, Aptose recognized interest expense of $0.4 million and $0.1 million, respectively, and paid nil in interest during both periods pursuant to the Hanmi Loan Agreement, Hanmi Facility Agreement, Amended Facility Agreement and Second Amended Facility Agreement. As of March 31, 2026 and December 31, 2025, accrued interest on the related party loan payable was $1.3 million and $0.9 million, respectively, with such amounts classified as a long-term liability given unpaid interest is due on August 31, 2028.

Pursuant to the Hanmi Facility Agreement, Amended Facility Agreement and Second Amended Facility Agreement, the Company granted a first ranking general security interest to Hanmi over all present and after acquired personal property, including over all inventory of drug substances and drug products that the Company has purchased or manufactured or will purchase or manufacture, and the Tuspetinib Licensing Agreement and all tuspetinib clinical trial data.

As of March 31, 2026, Hanmi held 508,710 Common Shares and 77,972 warrants to purchase Common Shares at an exercise price of $51.30 per Common Share of Aptose. Also see Note 8: Share capital.