10-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One)

☒ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934

For the fiscal year ended December 31, 2025

☐TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM TO

Commission File Number 001-32001

Aptose Biosciences Inc.

(Exact name of Registrant as specified in its Charter)

(Address of principal executive offices) (Zip Code)

Registrant’s telephone number, including area code: (647) 479-9828

Securities registered pursuant to Section 12(b) of the Act:

Title of each class TradingSymbol(s) Name of each exchange on which registered

None N/A N/A

Securities registered pursuant to Section 12(g) of the Act: None

Indicate by check mark if the Registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act. Yes ☐ No☒

Indicate by check mark if the Registrant is not required to file reports pursuant to Section 13 or 15(d) of the Act. Yes ☐ No ☒

Indicate by check mark whether the Registrant: (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes ☒ No ☐

Indicate by check mark whether the Registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the Registrant was required to submit such files). Yes ☒ No ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, 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.

Large accelerated filer ☐ Accelerated filer ☐

Non-accelerated filer ☒ Smaller reporting company ☒

Emerging growth company ☐

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 13(a) of the Exchange Act. ☐

Indicate by check mark whether the registrant has filed a report on and attestation to its management’s assessment of the effectiveness of its internal control over financial reporting under Section 404(b) of the Sarbanes-Oxley Act (15 U.S.C. 7262(b)) by the registered public accounting firm that prepared or issued its audit report. ☐

If securities are registered pursuant to Section 12(b) of the Act, indicate by check mark whether the financial statements of the registrant included in the filing reflect the correction of an error to previously issued financial statements. ☐

Indicate by check mark whether any of those error corrections are restatements that required a recovery analysis of incentive-based compensation received by any of the registrant’s executive officers during the relevant recovery period pursuant to §240.10D-1(b). ☐

Indicate by check mark whether the Registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act). Yes ☐ No ☒

The aggregate market value of the voting stock and nonvoting common equity held by non-affiliates computed by reference to the price at which the common equity was last sold, or the average bid and asked prices of such common equity, as of June 28, 2024 was $22,075,799.

As of March 31, 2026, the registrant had 2,552,429 Common Shares outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

TABLE OF CONTENTS

PART I. 2

ITEM 1. BUSINESS 2

ITEM 1A. RISK FACTORS 24

ITEM 1B. UNRESOLVED STAFF COMMENTS 45

ITEM 1C. CYBERSECURITY 46

ITEM 2. PROPERTIES 47

ITEM 3. LEGAL PROCEEDINGS 47

ITEM 4. MINE SAFETY DISCLOSURES 47

PART II. 48

ITEM 6. RESERVED 48

ITEM 7A. QUALITATIVE AND QUANTITATIVE DISCLOSURES ABOUT MARKET RISK 71

ITEM 8. FINANCIAL STATEMENTS AND SUPPLEMENTARY DATA 71

ITEM 9A. CONTROLS AND PROCEDURES 71

ITEM 9B. OTHER INFORMATION 72

ITEM 9C. DISCLOSURE REGARDING FOREIGN JURISDICTIONS THAT PREVENT INSPECTIONS 72

PART III.

ITEM 10. DIRECTORS, EXECUTIVE OFFICERS AND CORPORATE GOVERNANCE 73

ITEM 11. EXECUTIVE COMPENSATION 79

ITEM 14. PRINCIPAL ACCOUNTING FEES AND SERVICES 98

PART IV. 99

ITEM 15. EXHIBITS, FINANCIAL STATEMENT SCHEDULES 99

This Annual Report on Form 10-K contains certain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), and is subject to the safe harbor created by those sections. For more information, see “Part I. Item 1. Business — Cautionary Note Regarding Forward-Looking Statements.”

As used in this report, the terms “Aptose,” “Aptose Biosciences,” the “Company,” "the "Corporation," “we,” “us,” “our” and similar references refer to Aptose Biosciences Inc. (formerly known as Lorus Therapeutics Inc.) and our consolidated subsidiaries, and the term “Common Shares” refers to our common shares, no par value.

Aptose had historically qualified as a “foreign private issuer” for purposes of reporting under the Exchange Act, and filing registration statements under the Securities Act of 1933, as amended. Effective December 31, 2018, however, Aptose ceased qualifying as a foreign private issuer and began filing reports with the United States Securities and Exchange Commission ("SEC") as a “domestic issuer.” As a result, Aptose changed the accounting standards by which it prepares its financial statements from International Financial Reporting Standards to generally accepted accounting principles in the United States, or “U.S. GAAP.” All financial statements contained in this Annual Report are presented in accordance with U.S. GAAP. This report contains the following trademark, trade name and service mark of ours: Aptose. This report also contains trademarks, trade names and service marks that are owned by other persons or entities. All references to “dollar” or the use of the symbol “$” are to United States dollars, unless otherwise indicated.

PART I.

Item 1. Business

Overview

Aptose is a science-driven clinical stage biotechnology company dedicated to developing and commercializing precision medicines that address unmet clinical needs in oncology, with an initial focus on hematology. The Company’s small molecule cancer therapeutics pipeline includes products designed to deliver single-agent efficacy and to boost the effectiveness of other anti-cancer therapies and regimens without overlapping toxicities. The Company’s executive offices are located in San Diego, California, and its head office is based in Toronto, Canada.

Proposed Plan of Arrangement

On November 18, 2025, the Company entered into a definitive arrangement agreement (the “Arrangement Agreement”) with Hanmi Pharmaceutical Co. Ltd. ("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 ("Common Shares") 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, RSUs or warrants shall cease to be a holder of such options, RSUs 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 (the amended and restated Arrangement Agreement is referred to as the Arrangement Agreement). On March 31, 2026, shareholders of the Company approved the Arrangement at a special meeting of shareholders held for such purpose. In connection with the Arrangement, the Company will continue from the Canada Business Corporations Act to the Business Corporations Act (Alberta). The Arrangement is expected to close in the first half of 2026, subject to the satisfaction of customary closing conditions.

We expect to devote significant time and resources to the completion of the transactions contemplated by the Arrangement Agreement. However, there are no assurances when or if the Arrangement will be completed. The completion of the Arrangement is subject to the satisfaction or waiver of a number of conditions as set forth in the

Arrangement Agreement, including, among others (i) approval of the Arrangement Agreement by the shareholders of the Company, (ii) obtaining certain regulatory and governmental approvals, and (iii) the absence of legal restraints prohibiting the completion of the Arrangement. While the Aptose Board of Directors unanimously recommends voting FOR the Arrangement, there can be no assurance as to when these conditions will be satisfied or waived, if at all, or that other events will not intervene to delay or result in the failure to close the Arrangement. A substantial delay in obtaining satisfactory approvals or the imposition of unfavorable terms or conditions in any government or regulatory approvals could have an adverse effect on the business or financial condition of the Company. In addition, if for any reason the conditions to the Arrangement are not satisfied or waived or if the Arrangement is not completed for any reason, the Company’s ongoing business and financial results may be adversely affected, the market price of the Company’s common shares may be adversely affected, and the Company may need to consider insolvency.

Our Programs

We are advancing oral targeted agents to treat life-threatening hematologic cancers that require immediate treatment. We have one clinical-stage oral kinase inhibitor under active development for the treatment of hematologic malignancies: tuspetinib (HM43239). Two other molecules, luxeptinib (CG-806) and APTO-253, are not undergoing active clinical development at this time and will not be discussed further.

Tuspetinib, Aptose’s lead asset, is being developed for frontline combination therapy (tuspetinib + the BCL-2 inhibitor venetoclax + hypomethylating agent; TUS+VEN+HMA) in newly diagnosed AML patients to unlock the most significant patient impact and greatest commercial opportunity. Tuspetinib is a once-daily oral kinase inhibitor, targeting a select group of kinases operative in myeloid malignancies, such as acute myeloid leukemia ("AML") and the higher risk myelodysplastic syndromes ("hr-MDS"), and known to be involved in tumor proliferation, resistance to therapy, and differentiation. However, tuspetinib avoids kinases that typically cause toxicities associated with other kinase inhibitors and is consequently a well-tolerated antileukemic agent.

Tuspetinib-based triple drug (triplet) frontline combination therapy (tuspetinib + the BCL-2 inhibitor venetoclax + the hypomethylating agent azacitidine; TUS+VEN+AZA) currently is being investigated in newly diagnosed AML patients in the Phase 1/2 TUSCANY clinical study. Aptose has reported data from the 40, 80, 120, and 160 mg TUS cohorts that have demonstrated safety, complete remissions (CRs) and minimal residual disease (MRD) negativity across patients with diverse mutations, including patients with difficult-to-treat mutations in TP53, RAS and FLT3 genes.

The clinical development path with the tuspetinib-based TUS+VEN+HMA triplet combination therapy in newly diagnosed AML patients began with demonstration of safety and activity of tuspetinib as a single agent ("TUS") and then with the TUS+VEN doublet combination therapy in relapsed or refractory ("R/R") AML patients in whom frontline therapies have previously failed.

Tuspetinib monotherapy dose escalation and dose exploration activities have been completed as part of an international Phase 1/2 clinical trial designed to assess safety, tolerability, pharmacokinetics, pharmacodynamic responses, and efficacy of TUS as a single agent in patients with R/R AML. Complete responses (“CRs”) without dose limiting toxicities were achieved at four dose levels across a broad diversity of mutationally-defined AML populations and with a highly favorable safety profile. Tuspetinib monotherapy to date has demonstrated a favorable safety profile and has caused no drug-related QTc prolongations, liver or kidney toxicities, muscle damage, differentiation syndrome, and no myelosuppression with continuous dosing of patients in remission. A recommended phase 2 dose ("RP2D") of 80 mg tuspetinib once daily as an oral tablet was selected and approved by the U.S. FDA for use as a single agent in patients with R/R AML. At the RP2D, tuspetinib demonstrated notable response rates in R/R AML patients that had never been treated with venetoclax (VEN-naive AML): CR/CRh=36% among all-comers, CR/CRh=50% among patients with mutated FLT3, and CR/CRh=25% in patients with wildtype FLT3.

Following completion of the single agent dose escalation and exploration trial, tuspetinib advanced into the APTIVATE expansion trial of the Phase 1/2 program in R/R AML patient populations treated with tuspetinib combined with the BCL-2 inhibitor venetoclax (TUS+VEN doublet), with the intent to position tuspetinib for triple combination studies in frontline therapy for newly diagnosed AML patients. The TUS+VEN doublet combination therapy (with both 40mg and 80mg TUS) maintained a favorable safety profile: no new or unexpected safety signals

were observed, and there were no reported drug-related adverse events of QTc prolongation, differentiation syndrome, or deaths. Also, the TUS/VEN doublet combination (with 80mg TUS) achieved responses in heavily pretreated R/R AML patients, including those with wildtype or mutated FLT3, and those who failed prior therapy with venetoclax (Prior-VEN) or FLT3 inhibitors (Prior-FLT3i).

Based on the safety and efficacy profile of tuspetinib, we believe that tuspetinib, if approved, could 1) become the preferred kinase inhibitor for inclusion in triplet combination for front line AML patients with wild type FLT3 and with difficult-to-treat patients harboring mutations in the FLT3, RAS or TP53 genes, 2) become the preferred kinase inhibitor for inclusion in combination with venetoclax for second line AML patients, 3) serve as an effective agent for maintenance therapy to prevent relapse in patients who achieved a complete remission through a stem cell transplant or through drug-based therapy, 4) serve as an effective agent for the treatment of third line FLT3 mutated patients failed by prior therapy with other FLT3 inhibitors and 5) serve in front line triplet combinations, second line doublet combinations, and maintenance therapy for hr-MDS patients. These beliefs related to the potential commercial opportunity are based on management’s current assumptions and estimates, which are subject to change, and there can be no assurance that tuspetinib will ever be approved or successfully commercialized and, if approved and commercialized, that it will ever generate significant revenues. See our “Risk Factors – “We are an early-stage development company with no revenues from product sales.” and “We have a history of operating losses. We expect to incur net losses and we may never achieve or maintain profitability.” in this Annual Report on Form 10-K.

The following figure presents the clinical stage agents in our pipeline and their respective stages of development.

Tuspetinib Program

Licensing Overview

On November 4, 2021, we entered into a licensing agreement (the "Tuspetinib Licensing Agreement") with the South Korean company Hanmi Pharmaceutical Co Ltd. (“Hanmi”) for the clinical and commercial development of tuspetinib (formerly HM43239). Under the terms of the Tuspetinib Licensing Agreement, Hanmi granted us exclusive worldwide rights to tuspetinib for all indications. Hanmi received an upfront payment of $12.5 million, including $5.0 million in cash and $7.5 million in Common Shares. Also pursuant to the Tuspenitib Licensing Agreement, Hanmi is entitled to receive up to $407.5 million in future milestone payments, which are contingent upon achieving certain clinical, regulatory and sales milestones across several potential indications, as well as tiered royalties on net sales. The term of the Tuspenitib Licensing Agreement will continue on a product-by-product and country-by-country basis

until the expiration of the royalty period for such product in such country. The licenses granted to us will survive and become non-exclusive, perpetual, irrevocable and fully paid-up on a product-by-product and country-by-country basis, upon their natural expiration under the terms of the Tuspenitib Licensing Agreement.

Preclinical Profile

Tuspetinib isan oral, once-daily, highly potent myeloid kinome inhibitor designed to target key kinases operative in myeloid malignancies. In preclinical studies, tuspetinib demonstrated potent in vitro and in vivo activity against FLT3 ITD mutated as well as D835 and gatekeeper (F691) tyrosine kinase domain ("TKD") mutated AML that confer resistance to other agents. Additionally, tuspetinib inhibited phosphorylation of the SYK kinase, known to be highly activated in AML and associated with resistance to FLT3 targeted therapy. Tuspetinib also was designed to inhibit several kinases involved in tumor cell proliferation and/or differentiation, including mutant forms of c-KIT, JAK1, JAK2, and RSK, all with half maximal inhibitory concentration ("IC50") values < 10 nM.

Tuspetinib induced in vitro cytotoxicity in AML and Ba/F3 cell lines expressing FLT3 WT, ITD, and/or TKD point mutations. Tuspetinib showed greater inhibitory activity compared to quizartinib on Ba/F3 cells expressing resistance-conferring ITD/TKD double mutations (ITD/F691L and ITD/D835Y). Thus, tuspetinib may overcome clinically relevant ITD/TKD double mutations, which may result from sustained FLT3 inhibition. Moreover, target modulation was shown as tuspetinib inhibited FLT3 phosphorylation and downstream signaling molecules such as phospho-ERK and phospho-STAT5.

The in vivo anti-tumor efficacy of tuspetinib was demonstrated in murine xenograft models using MV-4-11 and MOLM-13 human AML cells having the ITD mutant form of FLT3 and using the MOLM-14 model having the ITD and F691L dual mutations of FLT3 with dosing regimens that match those currently under investigation. Tuspetinib exhibited dose-dependent tumor growth inhibition of models of FLT3 ITD mutant AML with complete tumor regression observed in some groups, and no change in body weight. Of note, tuspetinib produced greater tumor growth inhibition in the MOLM-14 FLT3-ITD/F691L model compared to gilteritinib, or entospletinib (SYK inhibitor) as single agents, and comparable activity to the gilteritinib plus entospletinib combination.

Latest Clinical Update and Program Status

On December 6, 2025, Aptose presented additional data from the ongoing TUSCANY trial of tuspetinib in combination with venetoclax and azacitidine (TUS+VEN+AZA) in a poster at the 67th American Society of Hematology (ASH) Annual Meeting in Orlando, Florida. Aptose reported that the TUS+VEN+AZA triplet frontline therapy shows high efficacy and MRD-negative remissions in newly diagnosed AML patients with diverse mutations. They also highlighted that safety remains a key feature of TUS-based therapies, with a 100% response rate (CR/CRh) at the higher dose levels (80 and 120 mg TUS). Complete responses (CR/CRh) were observed in FLT3 wildtype patients, who make up about 70% of AML cases, and also in AML patients with TP53/complex karyotype, RAS, and MDS-related mutations.

Key Messages included:

•

In newly diagnosed AML patients, TUS+VEN+AZA shows promising safety, tolerability and resilient efficacy, including MRD-negative remissions across a broad mutational spectrum

•

High quality clinical responses (CR/CRh):

90% across 40, 80 and 120 mg dose levels

100% at the higher 80 mg and 120 mg dose levels

Observed in FLT3-WT, FLT3-ITD, and NPM1c genetic subgroups

Observed in biallelic TP53/complex karyotype and RAS adverse genetic subgroups

Observed in AML with MDS-related mutations

•

MRD negativity: 78% by central flow cytometry in responding subjects

•

TUS targets VEN resistance mechanisms; inhibits kinase-driven abnormal signaling

•

Two subjects transitioned to stem cell transplantation, and both returned for TUS maintenance

•

TUS+VEN+AZA triplet therapy was well tolerated with no dose-limiting toxicities (DLTs) across all evaluable TUS dose levels

No DLTs including no prolonged myelosuppression for subjects in remission in Cycle 1

No drug-related deaths, differentiation syndrome, QTc prolongation, or CPK elevation reported

8/10 evaluable subjects experienced red cell and platelet transfusion independence for > 8 weeks after their best response

Febrile neutropenia was reported in 2 subjects (16.7%), with 1 subject related to TUS

•

At the recently enrolled 160 mg dose level, preliminary findings show patients achieving early blast clearance with MRD-negativity and formal responses in the first few weeks of treatment (not included in poster data cut)

On October 16, 2025, Aptose announced that Tuspetinib exceeded expectations when combined with standard of care treatment across diverse populations of newly diagnosed AML patients. Aptose announced that data from the ongoing TUSCANY trial of tuspetinib in combination with venetoclax and azacitidine (TUS+VEN+AZA) were presented in a poster presentation, entitled “TUSCANY Study of Safety and Efficacy of Tuspetinib plus Standard of Care Venetoclax and Azacitidine in Study Participants with Newly Diagnosed AML Ineligible for Induction Chemotherapy,” at the European School of Haematology (ESH) 7th International Conference on Acute Myeloid Leukemia “Molecular and Translational”: Advances in Biology and Treatment, being held from October 16-18, 2025 in Estoril, Portugal. Data to date from 10 patients in the TUSCANY trial across all three cohorts, 40 mg, 80 mg or 120 mg TUS dose in TUS+VEN+AZA, reveal promising clinical safety and antileukemic activity and support the use of TUS with standard of care treatment across a broad range of AML populations, including those carrying adverse mutations regardless of FLT3 mutation status.

Key Messages included:

•

TUS in combination with standard dosing of VEN+AZA has been well tolerated with no DLT, no treatment-related deaths, no differentiation syndrome, no QTc prolongation, no prolonged myelosuppression after remission in Cycle 1, and no CPK elevations reported at any dose levels to date in these newly diagnosed AML patients.

•

Addition of TUS to VEN+AZA achieved CR/CRh responses in 6/6 (100%) patients treated at the higher dose levels of 80 mg and 120 mg TUS, exceeding the 66% rate expected from VEN+AZA alone.

•

Overall, TUS+VEN+AZA CR/CRh responses were observed in 9/10 (90%) patients.

•

7 of 8 (88%) CR/CRh responses in FLT3 wildtype AML, representing 70% of AML population.

•

TUS+VEN+AZA MRD-negativity noted in 7/9 (78%) responding patients by central flow cytometry.

•

CR/CRh responses achieved across diverse mutational subtypes, including: unmutated FLT3, FLT3-ITD, NPM1c, biallelic TP53 with complex karyotype, RAS, and myelodysplasia-related mutations.

•

Dosing at the TUS 160 mg level is now ongoing.

On August 6, 2025, Aptose announced that the Cohort Safety Review Committee (the "CSRC") monitoring Aptose’s Phase 1/2 TUSCANY trial of TUS in combination with standard of care dosing of venetoclax and azacitidine (TUS+VEN+AZA triplet) has approved escalating from 120 mg TUS dose to 160 mg TUS dose based on its favorable review of safety and efficacy data from patients in the first three cohorts (40 mg, 80 mg, and 120 mg TUS dose levels) of the trial. Enrollment is open for dosing subjects at the 160 mg TUS dose level.

Key Messages included:

•

Safety Review Committee endorses escalation to 160 mg TUS dosing.

•

Cohorts with 120 mg, 80 mg, 40 mg TUS dosing completed with no dose-limiting toxicities.

•

Excellent safety and complete remissions (CRs) in some of the most difficult-to-treat AML populations.

•

No dose reductions required to the standard-of-care VEN/AZA with TUS dose cohorts.

•

TUS+VEN+AZA triplet continues to achieve CRs and minimal residual disease (MRD)-negativity with favorable safety in newly diagnosed AML patients.

On June 12, 2025, Aptose presented clinical data on safety, response, and MRD-negativity from the TUSCANY Phase 1/2 clinical trial of Tuspetinib triplet therapy in newly diagnosed AML patients during an oral presentation at the European Hematology Association Congress (EHA 2025), held from June 12-15, 2025, in Milan, Italy. The title of the presentation was “TUSCANY Study of Safety and Efficacy of Tuspetinib Plus Standard of Care Venetoclax and Azacitidine in Study Participants with Newly Diagnosed AML Ineligible for Induction Chemotherapy”. Dr. Gabriel Mannis, Associate Professor of Medicine, Stanford University School of Medicine, key opinion leader (KOL) in the treatment of AML, and an investigator in the TUSCANY study, delivered the oral presentation and reported safety and efficacy data from the first two dose cohorts at 40 mg of TUS or 80 mg of TUS in the TUS+VEN+AZA triplet. Dr. Mannis also noted that three patients were rapidly enrolled on the third dose cohort of 120 mg TUS in the TUS+VEN+AZA triplet, and that no DLTs have been observed to date. The oral presentation also included minimal residual disease (MRD-negativity) assessments and a longer duration of follow-up.

The TUS+VEN+AZA triplet is being developed as a mutation-agnostic frontline therapy to treat large, mutationally diverse populations of newly diagnosed AML patients who are ineligible to receive induction chemotherapy. The data presented reveal complete responses across patients with diverse mutations, including TP53-mutated/CK AML and FLT3-wildtype AML patients. TUS could have a significant commercial opportunity in the largest markets and the most challenging of AML cases, following regulatory clearance.

Key Messages included:

•

Addition of TUS to the standard of care VEN+AZA creates a well-tolerated and mutation-agnostic frontline triple drug therapy for newly diagnosed AML patients.

•

AML patients with diverse mutations, including TP53-mutated/CK and FLT3-wildtype, safely achieved complete remissions and MRD negativity.

•

Ten AML patients dosed across 40 mg, 80mg, and 120 mg TUS with TUS+VEN+AZA triplet.

Key Findings included:

•

As of June 30, 2025, ten newly diagnosed AML patients received the TUS+VEN+AZA combination:

Four received the 40 mg dose of TUS, three received the 80 mg dose of TUS, and three received the 120 mg dose of TUS

•

At the initial dose of 40 mg TUS (n=4), with patients on the longest duration of drug:

Three subjects achieved CRs and were MRD-negative, including

▪

Patient with FLT3-ITD

▪

Patient with FLT3-WT

▪

Patient with TP53/CK

•

At the 80 mg TUS dose level (n=3):

All three patients (100%) achieved composite complete remissions (CR and CRi)

A TP53-mutated/CK AML patient achieved an CRh

Too early in treatment for final MRD assessment

•

At the 120 mg TUS dose level (n=3):

All three patients at the 120 mg TUS dose level remain on therapy

All three patients (100%) already achieved composite complete remissions (CR and CRi)

Too early in treatment for formal MRD assessments

•

Regardless of mutation status, TUS is active in newly diagnosed AML patients

MRD-negative responses achieved across diverse genetic populations, including adverse TP53 mutations and CK

Responses continue to evolve, and the triplet continues to be well tolerated with no DLTs

•

TUS can be administered safely with standard-of-care dosing of VEN/AZA

TUS PK properties not altered by VEN, AZA, antifungals or food

No prolonged myelosuppression in Cycle 1 in the absence of AML

No treatment-related deaths; 9 out of 10 enrolled subjects remain on study

No treatment-related QTc prolongation, CPK elevations, or differentiation syndrome

On February 20, 2025, Aptose announced that the CSRC monitoring Aptose’s Phase 1/2 TUSCANY trial of tuspetinib in combination with standard of care dosing of venetoclax and azacitidine (TUS+VEN+AZA triplet) has unanimously approved escalating from a 40 mg dose of TUS to an 80 mg dose of TUS based on its favorable review of data from the first four patients in the trial. No significant safety concerns or dose-limiting toxicities (DLTs) have been reported, including no prolonged myelosuppression of subjects in remission. All four subjects treated in the 40 mg cohort remain on study, while enrollment is open for the 80 mg dose cohort.

Key Findings and Messages included:

•

To date, four newly diagnosed AML patients have received the lowest dose of TUS (40 mg) as part of the (TUS+VEN+AZA) combination.

•

Three patients with unmutated (wild-type) FLT3 (FLT3-WT) completed Cycle 1 of treatment with no dose-limiting toxicities (DLTs) or TUS dose adjustments.

Two FLT3-WT patients achieved complete remissions (CR and CRh) by the end of Cycle 1.

Notably, a patient with biallelic TP53 mutations and a complex karyotype obtained CR.

The third FLT3-WT patient experienced significant reductions in bone marrow leukemic blasts during Cycle 1 and remains on therapy in Cycle 2.

•

The fourth patient, harboring FLT3-ITD and NPM1 mutations, is currently dosing in Cycle 1 and is not yet eligible for response evaluation.

•

Pharmacokinetic (PK) analyses of TUS show that plasma levels are unaffected by the addition of AZA, providing predictability and avoiding the need for dose alterations due to PK interactions.

•

Similarly, VEN plasma levels in Cycle 1 are consistent with published results and the prior TUS/VEN APTIVATE study in R/R AML, indicating no clinically significant interactions with TUS.

On February 12, 2025, Aptose reported early safety and response results from Aptose’s Phase 1/2 TUSCANY trial with a 40 mg dose of tuspetinib in combination with standard of care dosing of venetoclax and azacitidine (TUS+VEN+AZA triplet) in mutationally diverse populations of newly diagnosed AML patients who are ineligible to receive induction chemotherapy.

Key Findings and Messages included:

•

In January 2025, Aptose announced the initiation of the TUSCANY trial and dosing in the first cohort of newly-diagnosed AML patients with the lowest starting dose (40 mg) of TUS as part of the TUS+VEN+AZA triplet, and the early data reveal promising clinical safety and antileukemic activity.

•

Four newly diagnosed AML patients have received the lowest dose of TUS (40 mg) as part of the (TUS+VEN+AZA) combination.

•

Three patients with unmutated (wild-type) FLT3 (FLT3-WT) completed Cycle 1 of treatment with no dose-limiting toxicities (DLTs) and no dose adjustments.

Two FLT3-WT patients achieved complete remissions (CR and CRh) by the end of Cycle 1.

Notably, a patient with biallelic TP53 mutations and a complex karyotype obtained CR.

The third FLT3-WT patient experienced significant reductions in bone marrow leukemic blasts during Cycle 1 and remains on therapy in Cycle 2.

•

The fourth patient, harboring FLT3-ITD and NPM1 mutations, is currently dosing in Cycle 1 and is not yet eligible for response evaluation.

•

Pharmacokinetic (PK) analyses for TUS show that plasma levels are unaffected by the addition of AZA, providing predictability and avoiding the need for dose adjustments due to PK interactions.

On January 20, 2025, Aptose announced that the CSRC monitoring Aptose’s Phase 1/2 TUSCANY trial of tuspetinib in combination with standard of care dosing of venetoclax and azacitidine (TUS+VEN+AZA triplet) has unanimously approved escalating from 40 mg TUS to 80 mg TUS based on its favorable review of data from the first four patients in the trial. No significant safety concerns or dose limiting toxicities (DLTs) have been reported, including no prolonged myelosuppression of subjects in remission. All four subjects treated in the 40 mg cohort remain on study while enrollment is open for the 80 mg cohort.

Key Findings and Messages included:

•

To date, four newly diagnosed AML patients have received the lowest dose of TUS (40 mg) as part of the (TUS+VEN+AZA) combination.

•

Three patients with unmutated (wildtype) FLT3 (FLT3-WT) completed Cycle 1 of treatment with no dose-limiting toxicities (DLTs) and no TUS dose adjustments.

Two FLT3-WT patients achieved complete remissions (CR and CRh) by the end of Cycle 1.

Notably, a patient with biallelic TP53 mutations and a complex karyotype obtained CR.

The third FLT3-WT patient experienced significant reductions in bone marrow leukemic blasts during Cycle 1 and remains on therapy in Cycle 2.

•

The fourth patient, harboring FLT3-ITD and NPM1 mutations, is currently dosing in Cycle 1 and is not yet eligible for response evaluation.

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Pharmacokinetic (PK) analyses for TUS show plasma levels unaffected by the addition of AZA, providing predictability and avoiding the need for dose alterations due to PK interactions.

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Similarly, VEN plasma levels in Cycle 1 are consistent with published results and the prior TUS/VEN APTIVATE study in R/R AML, indicating no clinically significant interactions with TUS.

On January 9, 2025, Aptose announced dosing the first set of patients in the TUSCANY Phase 1/2 study with tuspetinib (TUS) in combination with venetoclax (VEN) and azacitidine (AZA) as a frontline triple drug combination (triplet) therapy for patients newly diagnosed with acute myeloid leukemia, or AML.

On January 12, 2025, Aptose announced promising early safety and response results from newly diagnosed acute myeloid leukemia (AML) patients dosed in Aptose’s Phase 1/2 TUSCANY trial with a 40 mg dose of tuspetinib in combination with standard of care dosing of venetoclax and azacitidine (TUS+VEN+AZA triplet). The TUS+VEN+AZA triplet is being developed as a frontline therapy to treat large, mutationally diverse populations of newly diagnosed AML patients who are ineligible to receive induction chemotherapy.

In December 2024, Aptose attended the 66th Annual American Society of Hematology (ASH) Meeting and Exposition in San Diego, California, and presented a poster entitled “Phase 1 Safety and Efficacy of Tuspetinib Plus Venetoclax Combination Therapy in Study Participants with Relapsed or Refractory Acute Myeloid Leukemia (AML) Support Exploration of Triplet Combination Therapy of Tuspetinib Plus Venetoclax and Azacitidine for Newly Diagnosed AML”.

Key Findings and Messages included:

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TUS+VEN+AZA triplet trial is proceeding in newly diagnosed AML patients

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TUS+VEN retains activity in the difficult-to-treat prior-VEN AML population

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TUS+VEN is active in FLT3 wildtype, representing ~70% of AML patients

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TUS+VEN is well tolerated and can be safely co-administered

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TUS+VEN is active across broad populations of R/R AML

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Combination of TUS with VEN may avoid VEN resistance

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TUS+VEN+AZA triplet may establish a more effective, mutation agnostic standard of care for chemotherapy ineligible AML patients

Highlights of the ASH poster presentation included:

TUS as Single Agent (n= 93 Patients)

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60% and 42% CR/CRh with 80 mg TUS in FLT3 mutated and all-comer VEN-naïve AML

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33% CRc & 42% ORR (CR, CRp, CRh, CRi or PR) in FLT3 mutated and VEN-naïve patients

Includes 40, 80, 120, and 160 mg TUS dose as a single agent

Includes those who failed prior therapy with venetoclax

Includes those with mutated or unmutated FLT3, those who failed prior-HSCT, priorFLT3i, prior-chemotherapy, prior-HMA

TUS once daily orally as a single agent achieved CR/CRh responses at four different dose levels (40, 80, 120, and 160 mg) with no dose limiting toxicities (no DLTs)

TUS showed a favorable safety profile with no DLTs through 160 mg per day, and no drug related discontinuations, no QTc, no differentiation syndrome, and no deaths

TUS/VEN Combination Therapy (n= 79 Patients)

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40% ORR with 80 mg TUS + 400 mg VEN in FLT3 mutated patients

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83% (5/6) had failed prior-VEN treatment and 50% (3/6) had failed both prior-VEN and FLT3i treatment

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TUS+VEN achieved responses among diverse R/R AML with adverse mutations in VEN-naïve, prior-VEN, FLT3WT, FLT3MUT, prior-FLT3

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TUS+VEN showed favorable safety and tolerability with no new or unexpected safety

On December 3, 2024, the Company announced that the National Cancer Institute (NCI), part of the National Institutes of Health, and the Company had entered into a Cooperative Research and Development Agreement (“CRADA”). Under the CRADA, the NCI and Aptose will collaborate on the clinical development of Aptose’s proprietary lead clinical-stage compound tuspetinib (TUS), an inhibitor of key signaling kinases involved in myeloid malignancies, in the NCI Cancer Therapy Evaluation Program (CTEP) sponsored MyeloMATCH trials employing combinations of targeted therapy for the treatment of molecularly defined acute myeloid leukemia (AML) and myelodysplastic syndromes (MDS) populations. These trials will be conducted by NCI's National Clinical Trials

Network (NCTN), with the participation of the NCI Community Oncology Research Program (NCORP) in the U.S. and Canada. The MyeloMATCH precision medicine trials (NCT05564390), funded by the NCI, were officially launched on May 16, 2024. MyeloMATCH aims to expedite the development of tailored drug combination treatments for patients with newly diagnosed AML and MDS and to treat patients with these aggressive cancers of the blood and bone marrow from diagnosis throughout their treatment journey.

On June 14, 2024, Aptose presented tuspetinib (TUS) clinical findings as a clinical poster presentation and preclinical findings as a e-poster at the European Hematology Association (EHA) 2024 Hybrid Congress in Madrid, Spain.

Highlights of the findings include:

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Tuspetinib Monotherapy (TUS) and Tuspetinib + Venetoclax (TUS+VEN) Doublet Therapy Show Broad Clinical Activity and Strong Safety Data in relapsed or refractory (R/R) Acute Myeloid Leukemia (AML) and Differentiate TUS from other Investigational Drugs in AML

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TUS Monotherapy and TUS+VEN Doublet Therapy Active in Difficult-to-treat Genetic Subgroups, FLT3 Wildtype AML

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TUS Shown to Target VEN Resistance Mechanisms and Retain Activity on VEN-Resistant AML Cells in Preclinical Study

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Tuspetinib + Venetoclax + Azacitidine (TUS+VEN+AZA) Triplet Trial to Treat Newly Diagnosed AML Patients; Clinical Sites Being Activated

Our APTIVATE clinical trial of Tuspetinib as a monotherapy (TUS) and in combination treatment with Venetoclax (TUS+VEN) in a very ill AML patient population, yielded excellent and consistent safety findings and demonstrated clinical activity across a broad range of AML – including many with highly adverse genetic mutations. These findings supported the advancement of Tuspetinib as an ideal third agent to add to a venetoclax and hypomethylating agent regimen for the frontline treatment of Newly Diagnosed AML patients. Conclusions from the clinical poster, entitled “Safety and Efficacy of Tuspetinib as Monotherapy and Combined with Venetoclax in a Phase 1/2 Trial of Patients with Relapsed or Refractory (R/R) Acute Myeloid Leukemia” include:

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Extensive dose exploration was performed with TUS (93 patients) and TUS+VEN (79 patients) in highly treatment-experienced R/R AML patients (prior VEN, FLT3i, HMA, chemotherapy, HSCT)

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TUS monotherapy achieved complete remissions at 40, 80, 120, and 160 mg with no DLT, achieved a 42% CRc and 50% ORR in VEN naïve and FLT3-mutation harboring patients, and achieved responses in patients harboring highly adverse genetics (TP53MUT, RASMUT, other)

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TUS+VEN Doublet remained safe and well tolerated (40mg TUS + 400mg VEN | 80mg TUS + 400mg VEN), and achieved bone marrow blast reductions and responses among diverse R/R AML patients with adverse mutations and prior failure of VEN

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TUS targets known VEN resistance mechanisms in vitro and is clinically active in both FLT3MUT & FLT3WT R/R AML populations even after prior VEN exposure.

The greatest unmet medical need in AML is for an improved frontline therapy in Newly Diagnosed AML patients. Tuspetinib is now being developed as the TUS+VEN+HMA to establish a new standard of care for the treatment of these Newly Diagnosed AML patients that may increase response rates, extend survival, safely improve quality of life, treat a broad spectrum of genetically unique AML patient populations, and blunt the development of resistance to venetoclax.

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Progress has been made with VEN+HMA in 1L therapy but 1/3 do not respond and median OS <15 months with <25% alive at 3-years.

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Response rates and OS need improvement, especially in adverse genetic subgroups

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Emergence of VEN resistance via RAS/MAPK, TP53, and FLT3 clonal expansion, among other mechanisms, leads to relapse or refractory (R/R) AML that does not respond well to subsequent salvage therapies in R/R setting.

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A 3rd agent is needed to boost responses with VEN+HMA standard of care therapy.

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We believe Tuspetinib is the ideal 3rd Agent for Addition to VEN+AZA to Treat Newly Diagnosed AML

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TUS has excellent safety alone and in combination with VEN when co-administered

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TUS has broad activity across genetic subgroups including TP53, RAS/MAPK, & FLT3 mutants

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TUS mechanism may minimize drug resistance to VEN via inhibition of key AML kinases

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TUS can be administered with or without food allowing co-administration with VEN

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Preliminary PK data suggest no clinically meaningful interaction between TUS and VEN requiring dose modification for co-administration

In addition to the Tuspetinib clinical poster, a separate preclinical abstract was published as a poster publication at EHA, entitled “Tuspetinib Retains Nanomolar Potency Against AML Cells Engineered to Express the NRAS G12D Mutation or Selected for Resistance to Venetoclax’. The study demonstrated that TUS targets known venetoclax (VEN) resistance mechanisms, retaining nanomolar potency against AML cells engineered to express the NRAS-G12D mutation or selected for resistance to VEN, and in combination with VEN, could prevent the emergence of resistance to both agents. TUS resistant cells showed hypersensitivity to VEN such that treatment with both drugs could also interfere with the emergence of TUS resistance.

On March 26, 2024, Aptose announced that more than 170 patients to date received TUS alone or in combination with the BCL-2 inhibitor venetoclax (VEN) during the Phase 1/2 clinical program in the very ill relapsed or refractory (R/R) AML patient population. At the single-agent 80 mg dose, TUS demonstrated a favorable safety profile and an impressive response rate among patients naive to VEN. The safety profile of TUS remained favorable when combined with VEN in R/R AML patients, and responses were observed in both patients naive to VEN and those who had failed prior VEN therapy. TUS avoids many typical toxicities observed with other agents and achieves broad activity across AML patients with a diversity of adverse genetic abnormalities.

On December 9, 2023, Aptose featured tuspetinib in an oral presentation at the 65th American Society of Hematology ("ASH") Annual Meeting and Exposition and announced that a growing body of clinical data for Aptose’s lead compound tuspetinib, demonstrates significant benefit as a single agent and in combination with venetoclax (VEN) in patients with R/R AML in the ongoing APTIVATE Phase 1/2 study. Data was presented in an oral presentation by lead investigator Naval G. Daver, M.D., Professor, Director Leukemia Research Alliance Program, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, TX.

Dr. Daver reported data from more than 100 relapsed/refractory patients from multiple international clinical sites, who had failed prior therapy and then were treated with TUS as a single agent or the TUS+VEN doublet. Both TUS and the TUS+VEN doublet delivered multiple composite complete remissions ("CRc") in this very ill AML population, while maintaining a favorable safety profile across all treated patients. The data demonstrated that tuspetinib as a single agent (TUS) is active and well tolerated in one of the most challenging and heterogeneous disease settings in oncology – relapsed and refractory AML. Tuspetinib demonstrated broad activity, including in patients with FLT3 wild-type AML (accounting for more than 70% of the AML population), FLT3-mutated AML, NPM1-mutated AML, and in patients with mutations historically associated with resistance to targeted therapy. Most notably, TUS targets VEN resistance mechanisms, enabling the TUS+VEN combination therapy to uniquely treat the very ill prior-VEN AML population, including both FLT3-mutant and FLT3-wildtype disease. From a broader perspective, the growing body of antileukemic activity and continued favorable safety profile support the advancement of tuspetinib as the TUS+VEN+HMA triplet combination therapy for the treatment of frontline newly diagnosed AML patients.

Dr. Daver also pointed out that while patients on the TUS+VEN therapy are early in their treatment cycles, most patients achieving a response remained on treatment and that responses have begun to mature as dosing continues. Highlights of Dr. Daver’s ASH oral presentation include:

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As a single agent at therapeutic doses of 80-160 mg in 68 evaluable patients, TUS was more active in VEN-naive patients, with an overall CRc rate of 29% (8/28). This included a 42% CRc rate (5/12) in FLT3-mutated patients and a 19% CRc rate (3/16) in FLT3-unmutated, or wildtype, AML patients. Responses and blood counts improved with continuous dosing, many patients bridged to an allogeneic stem cell transplant (HSCT), durability was observed when HSCT was not performed, and 80 mg was selected as the RP2D. Overall, tuspetinib showed a favorable safety profile with only mild adverse events (AEs) and no dose-limiting toxicities (DLTs) up to 160 mg per day, and no drug discontinuations from drug-related toxicity.

•

In the TUS+VEN doublet study, 49 patients were dosed with 80 mg of tuspetinib and 200 mg of venetoclax, with 36 evaluable (and 13 patients too early to assess). Patients were heavily exposed to Prior-VEN and Prior-FLT3 inhibitor treatment. TUS+VEN was active in both VEN-naive and Prior-VEN R/R AML patients. TUS demonstrated compelling composite complete remission (CRc) rates. Among all evaluable patients, TUS+VEN demonstrated a CRc rate of 25% (9/36); 43% (3/7) in VEN-naive patients, and 21% (6/29) in Prior-VEN patients. Among FLT3 wildtype patients, TUS+VEN demonstrated an overall CRc rate of 20% (5/25); 33% (2/6) in VEN-naive patients, and 16% (3/19) in Prior-VEN patients. Among FLT3 mutant patients, TUS+VEN demonstrated an overall CRc rate of 36% (4/11); a complete response in a VEN-naive patient (1/1); a 30% (3/10) in Prior-VEN patients; and 44% (4/9) in patients treated prior with a FLT3 inhibitor.

Clinical data from tuspetinib in AML was presented at the ASH Annual Meeting in December 2022 and during a Corporate Comprehensive Clinical Update Call held December 11, 2022. Data presented demonstrated that tuspetinib delivers single agent responses without prolonged myelosuppression or life-threatening toxicities in these very ill and heavily pretreated relapsed or refractory AML patients. Responses were observed in a broad range of mutationally-defined populations, including those with mutated forms of NPM1, MLL, TP53, NRAS, KRAS, DNMT3A, RUNX1, wild-type FLT3, ITD or TKD mutated FLT3, various splicing factors, and other genes. As of October 6, 2022, 60 heavily pretreated R/R AML patients were enrolled at multiple centers and treated at doses escalating from 20 mg to 200 mg, with further dose exploration at the 40 mg, 80 mg, 120 mg and 160 mg dose levels. Tuspetinib delivered multiple CRs at 40 mg, 80 mg, 120 mg and 160 mg dose levels in which no DLTs were observed. Tuspetinib demonstrated clinically meaningful benefit in all responders, by either bridging successfully to HSCT or leading to a durable response, as well as a favorable safety profile. In addition to 5 CRcs and 1 PR reported at ASH 2021, 4 new CRcs and 3 new PRs were generated in 2022. New responses during 2022 were achieved with 160 mg, 120 mg, 80 mg, and 40 mg. Among efficacy-evaluable patients treated with 80 mg, 120 mg, or 160 mg, response rates ranging from 19% to 75% were observed in specific genotypic subpopulations of R/R AML patients. Significant bone marrow leukemic blast reductions were observed broadly in FLT3+ and FLT3 wildtype patients across multiple dose levels, comparable to reported gilteritinib data, except that the patients treated with tuspetinib were more heavily pre-treated relapsed and refractory AML patients than those treated with gilteritinib. Vignettes of patient experiences highlight the potency and breadth of tuspetinib in delivering complete remissions across several mutationally defined populations with diverse adverse mutations. Tuspetinib continued to show a favorable safety profile with only mild AEs and no DLTs up to 160 mg per day, and no drug discontinuations from drug-related toxicity. No drug-related SAE, drug-related deaths, differentiation syndrome, AE of QT prolongation or DLT were observed through the 160 mg level. Tuspetinib avoids many of the typical toxicities observed with other tyrosine kinase inhibitors. We identified a safe therapeutic range with a broad therapeutic window, spanning the dose levels of 40, 80, 120 and 160 milligrams. We also announced that enrollment had been initiated in the APTIVATE expansion trial for monotherapy and drug combination therapy with tuspetinib. For the APTIVATE expansion trial, we selected 120 mg as the initiating single agent expansion dose and 80 mg as the initiating dose selected for combination with venetoclax.

On January 30, 2023, we announced the dosing of patients in the APTIVATE Phase 1/2 clinical trial of tuspetinib, and that another clinical response has been achieved by a R/R AML patient receiving 40 mg tuspetinib once daily orally in the original dose exploration trial, the second response at the recently launched low-dose 40 mg cohort. In addition, we elucidated a rationale for the superior safety profile of tuspetinib. While several kinase inhibitors require high exposures to elicit responses by nearly completely suppressing a single target, they often cause

additional toxicity because they also extensively inhibit that target in normal cells. In contrast, tuspetinib simultaneously suppresses a small suite of kinase-driven pathways critical for leukemogenesis. Consequently, tuspetinib achieves clinical responses at lower exposures with less overall suppression of each pathway, thereby avoiding many toxicities observed with competing agents

Concurrent with the European Hematology Association (EHA) Annual Congress held June 8-11, 2023, Aptose held an interim clinical update webcast on June 10, 2023, to present highlights from the ongoing clinical development of tuspetinib. Aptose reported completion of the tuspetinib dose escalation and dose exploration Phase 1/2 trial in 77 R/R AML patients, tuspetinib demonstrated a favorable safety profile, and tuspetinib delivered monotherapy responses across four dose levels with no dose-limiting toxicity in mutationally diverse and difficult to treat R/R AML populations, including patients with highly adverse mutations that typically do not respond to monotherapy or combination therapy: TP53-mutated patients with a CR/CRh = 20% and RAS-mutated patients with a CR/CRh = 22%. Aptose also reported completion of a successful End of Phase 1 Meeting with the US FDA for tuspetinib, that a monotherapy RP2D was selected as 80mg daily, and that all development paths remain open, including the single arm accelerated path. Following completion of the dose escalation and dose exploration phases of the Phase 1/2 clinical program, Aptose focused attention on the tuspetinib APTIVATE expansion trial. The APTIVATE trial sought to identify patient populations that may serve as development paths for R/R AML patients sensitive to the TUS+VEN doublet and that can support accelerated and full approvals. We reported that patient enrollment in the APTIVATE expansion trial has been brisk and preliminary CR activity had already been reported in patients receiving the TUS+VEN doublet who previously failed therapy with venetoclax.

On October 29, 2023, Aptose presented two posters related to the clinical and preclinical activity of tuspetinib at the European School of Haematology 6th International Conference: Acute Myeloid Leukemia "Molecular and Translational": Advances in Biology and Treatment, held October 29-31, 2023, in Estoril, Portugal. Clinical findings included 1) data from the APTO-TUS-HV01 clinical trial (the "Food Effect Study") evaluating the pharmacokinetic (PK) properties of tuspetinib in healthy human volunteers in which tuspetinib was administered with or without food, and 2) from an international Phase 1/2 study of tuspetinib as a single agent and in combination with venetoclax in patients with R/R AML from across clinical centers in the United States, South Korea, Spain, Australia and other sites. Data from the Food Effect Study in healthy human volunteers demonstrated tuspetinib can be administered with or without food and foresee no clinically meaningful difference in exposure. This is an important finding for patient convenience, as venetoclax is dosed with food and tuspetinib can now be simultaneously administered with the venetoclax rather than require staggered dosing. Findings from the Phase 1/2 clinical trial demonstrated tuspetinib as a single agent was well-tolerated and highly active among R/R AML patients with a diversity of adverse genotypes and delivered a 42% CR/CRh cross-evaluable venetoclax-naive patients at the 80mg daily RP2D. The TUS+VEN doublet has been well tolerated in the APTIVATE international Phase 1/2 expansion trial in R/R AML patients and achieved multiple responses in patients who previously failed venetoclax ("Prior-VEN failure AML"), including Prior-VEN failure patients who also previously failed FLT3 inhibitors, all of whom represent emerging populations of high unmet medical need. Notably, tuspetinib targets mechanisms of venetoclax resistance that may re-sensitize patients with prior venetoclax failure to venetoclax.

Separate from the clinical studies, the preclinical study (entitled: “Tuspetinib Oral Myeloid Kinase Inhibitor Creates Synthetic Lethal Vulnerability to Venetoclax”) presented by Aptose during the ESH Conference investigated the effects of tuspetinib on key elements of the phosphokinome and apoptotic proteome in both parental and TUS-resistant AML cells. In parental cells, tuspetinib inhibits key oncogenic signaling pathways and shifts the balance of pro- and anti-apoptotic proteins in favor of apoptosis, suggesting that it may generate vulnerability to venetoclax. Indeed, acquired resistance in the AML cells to tuspetinib generated a synthetic lethal vulnerability to venetoclax of unusually high magnitude. Concurrent administration of TUS+VEN therefore may discourage the emergence of resistance to tuspetinib during treatment. In conjunction with poster presentations at the ESH Conference, on October 30, 2023, Aptose held a “Clinical Update and KOL Data Review of AML Drug Tuspetinib” that was webcast and featured Dr. Naval Daver, MD, Professor, Director Leukemia Research Alliance Program, Department of Leukemia, The University of Texas MD Anderson Cancer Center, Houston, Texas. Dr. Daver is the lead investigator on Aptose’s APTIVATE trial and is recognized for significant achievements in the development of novel AML treatments, including several combination therapies. Aptose presented data in 49 patients who received the TUS+VEN doublet, showing an overall response rate (ORR) of 48% among all patients that had achieved an evaluable stage, as well as a 44% ORR among Prior-VEN failure AML patients, including FLT3-unmutated (wildtype) patients (43% ORR) and FLT3-mutated patients (60% ORR), some of whom also had failed prior therapy with FLT3 inhibitors. The TUS+VEN

doublet was well tolerated with no unexpected safety signals. The TUS/VEN doublet may serve the Prior-VEN failure R/R AML patients that represent a rapidly growing population that is highly refractory to any salvage therapy with response rates in the 4-15% range. The compelling data with the TUS+VEN doublet in R/R AML patients suggest a TUS+VEN+HMA triplet may serve the needs of frontline (1L) newly diagnosed AML patients.

Competitive Conditions

The biotechnology and pharmaceutical industries are characterized by rapidly evolving technology and intense competition. There are numerous companies in these industries that are focusing their efforts on activities similar to ours. Some of these are companies with established positions in the pharmaceutical industry and may have substantially more financial and technical resources, more extensive research and development capabilities, and greater marketing, distribution, production, and human resources than us. In addition, we face competition from other companies for opportunities to enter partnerships with biotechnology and pharmaceutical companies and academic institutions.

Competition with our potential products may include chemotherapeutic agents, monoclonal antibodies, antisense therapies, small molecules, immunotherapies, vaccines, and other biologics with novel mechanisms of action. These drugs may kill cancer cells indiscriminately, or through a targeted approach, and some have the potential to be used in non-cancer indications. We also expect that we will experience competition from established and emerging pharmaceutical and biotechnology companies that have other forms of treatment for the cancers that we target, including drugs currently in development for the treatment of cancer that employ a number of novel approaches for attacking these cancer targets. Cancer is a complex disease with more than 100 indications requiring drugs for treatment. The drugs in competition with our potential drugs have specific targets for attacking the disease, targets which are not necessarily the same as ours. These competitive drugs, however, could potentially also be used together in combination therapies with our drugs to manage the disease. Other factors that could render our potential products less competitive may include the stage of development, where competitors’ products may achieve earlier commercialization, as well as superior patent protection, better safety profiles, or a preferred cost-benefit profile.

Intellectual Property

We believe that our issued patents and pending applications are important in establishing and maintaining a competitive position with respect to our products and technology.

Tuspetinib (HM43239)

In November 2021, we licensed the exclusive rights to research, develop, and commercialize tuspetinib (the "Tuspetinib Licensing Agreement"). Under the terms of the Tuspetinib Licensing Agreement, Hanmi granted Aptose exclusive worldwide rights to tuspetinib for all indications. Aptose is now the exclusive licensee of the composition of matter and use patents covering tuspetinib, and tuspetinib analogs. Aptose believes that it now owns rights to a strong and defensive intellectual property position.

As of December 31, 2025, Aptose owned rights in 59 issued patents, including 4 issued U.S. patents, and 23 patents validated in European countries that are in force and cover the tuspetinib compound or analog compounds. These patents are expected to provide protection until 2038 through 2039. Patent applications are also pending in the United States and in contracting states to the Patent Cooperation Treaty for coverage of tuspetinib and analog compounds, with expected expiry dates between 2038 and 2044.

The Company’s research and development activities involve the controlled use of hazardous and radioactive materials and, accordingly, the Company is subject to federal, provincial and local laws and regulations in the United States and Canada governing the use, manufacture, storage, handling and disposal of such materials and certain waste products. To the knowledge of the Company, compliance with such environmental laws and regulations does not and will not have any significant impact on its capital spending, profits or competitive position within the normal course of its operating activities. There can be no assurance, however, that the Company will not be required to incur significant costs to comply with environmental laws and regulations in the future or that its operations, business or assets will not be materially adversely affected by current or future environmental laws or regulations.

Employees

As of December 31, 2025, we employed 14 full-time persons in research and drug development and administration activities. Three of our employees hold Ph.D.s, one holds an M.D, and numerous others hold degrees and designations such as M.Sc., B.Sc., C.P.A., and M.B.A. To encourage a focus on achieving long-term performance, employees and members of the board of directors of the Company (the “Board”) have the ability to acquire an ownership interest in the Company through Aptose’s share option and alternative compensation plans.

The business of the Company requires personnel with specialized oncology skills and knowledge. Researchers must be able to design and implement studies to assess the efficacy of anticancer drugs. Specialized knowledge and skills relating to chemistry and formulation process development are also needed. Such knowledge and skills are needed to develop product-specific analytical methods and formulation processes. The Company’s business also requires clinical and regulatory expertise. The Company has trained scientists and personnel with broad experience in these fields.

None of our employees are unionized, and we consider our relations with our employees to be good.

Government Regulation

Overview

Our overall regulatory strategy is to work with the appropriate government departments that regulate the use and sale of therapeutic drug products. This includes the FDA in the United States, Health Canada in Canada, the European Medicines Agency (“EMA”) in Europe, and other local regulatory agencies with oversight of preclinical studies, clinical trials and marketing of therapeutic products. Where possible, we intend to take advantage of opportunities to accelerate the development of drugs designed to treat rare and serious or life-threatening diseases. We also intend to pursue priority evaluation of any application for marketing approval filed in Canada, the United States or the European Union and to file additional drug applications in other markets where commercial opportunities exist. We may not be able to successfully pursue these opportunities.

Regulations by government authorities in the United States, Canada, and the European Union are significant factors in guiding our current research and drug development activities. To clinically test, manufacture and market drug products for therapeutic use, we must be in compliance with guidance and regulations established by the regulatory agencies in the countries in which we currently operate or intend to operate.

The laws of most of these countries require the licensing of manufacturing facilities, carefully controlled research and the extensive testing of products. Biotechnology companies must establish the safety and efficacy of their new products in clinical trials; they must establish and comply with current good manufacturing practices ("cGMPs") for the manufacturing of the product and control over marketing activities before being allowed to market a product. The safety and efficacy of a new drug must be demonstrated through human clinical trials conducted in accordance with the guidance and regulations established by local and federal regulatory agencies.

The process of completing clinical trials and obtaining regulatory approval for a new drug takes several years and requires substantial resources. Once a new drug or product license application is submitted, regulatory agencies may not review it in a timely manner or approve the product. Even after a New Drug Application (“NDA”) submission has occurred and/or approval has been obtained, further studies, including post-marketing studies, may be required to provide additional data on the efficacy and safety necessary to confirm the approved indication or to gain approval for

the use of the new drug as a treatment for clinical indications other than those for which the new drug was initially tested. Regulatory agencies also require post-marketing surveillance programs to monitor a new drug’s side effects, safety and long-term effects of the product. A serious safety or effectiveness problem involving an approved new drug may result in a regulatory agency mandating its withdrawal from the market and possible civil action. We may encounter such difficulties or high costs in securing the necessary approvals, which could delay or prevent us from manufacturing or marketing our products.

In addition to the regulatory product approval framework, biotechnology companies, including Aptose, are subject to regulation under local, provincial, state and federal law, including requirements regarding occupational safety, laboratory practices, environmental protection and hazardous substance control, and may be subject to other present and future local, provincial, state, federal and foreign regulation, including possible future regulation of the biotechnology industry.

Approval of New Drugs in Canada

In Canada, the manufacture and sale of new drugs are controlled by Health Canada. New drugs must pass through several testing stages, including pre-clinical testing and human clinical trials. Pre-clinical testing involves testing the new drug’s chemistry, pharmacology and toxicology in vitro and in vivo. Successful results (that is, potentially valuable pharmacological activity combined with an acceptable level of toxicity) enable the developer of the new drug to file a clinical trial application to initiate clinical trials in humans.

To study a drug in Canadian patients, a clinical trial application submission must be filed with Health Canada. The clinical trial application submission must contain specified information, including the results of the pre-clinical tests completed at the time of the submission and any available information regarding use of the drug in humans. In addition, since the method of manufacture may affect the efficacy and safety of a new drug, information on manufacturing methods and standards and the stability of the drug substance and dosage form must be presented. Production methods and quality control procedures must be in place to ensure an acceptably pure product, essentially free of contamination and uniformity across all quality aspects.

In addition, all federally regulated trials must be approved and monitored by an independent committee of doctors, scientists, advocates and others to ensure safety and ethical standards, Institutional Review Boards (“IRBs”) or Ethics Review Boards (“ERBs”). The review boards study and approve all study-related documents before a clinical trial begins and also carefully monitor data to detect benefit or harm, and the validity of results.

Provided that Health Canada does not reject the clinical trial application and IRB or ERB approval has been obtained, clinical trials can begin. Clinical trials for product candidates in Canada, as in the United States, are generally carried out in three phases. Phase 1 involves studies to evaluate toxicity and ideal dose levels in healthy humans. The new drug is administered to human patients who have met the clinical trial entry criteria to determine pharmacokinetics, human tolerance and prevalence of any adverse side effects. Phases 2 and 3 involve therapeutic studies. In Phase 2, efficacy, dosage, side effects and safety are established in a small number of patients who have the disease or disorder that the new drug is intended to treat. In Phase 3, there are controlled clinical trials in which the new drug is administered to a large number of patients who are likely to receive benefit from the new drug. In Phase 3, the effectiveness of the new drug in patients is compared with that of standard accepted methods of treatment to provide sufficient data for statistical proof of safety and efficacy for the new drug.

If clinical studies establish that a new drug is safe and effective, the manufacturer submits a new drug submission application to Health Canada for marketing approval. The new drug submission contains all known information known about the new drug, including the results of pre-clinical testing and clinical trials. Information about a substance contained in a new drug submission includes its proper name, its chemical name, and details on its method of manufacturing and purification, and its biological, pharmacological, and toxicological properties. The new drug submission also provides information about the dosage form of the new drug, including a quantitative listing of all ingredients used in its formulation, its method of manufacture, manufacturing facility information, packaging and labeling, the results of stability tests, and its diagnostic or therapeutic claims and side effects, as well as details of the clinical trials to support the safety and efficacy of the new drug. Furthermore, for biological products, an on-site evaluation is completed to assess the production process and manufacturing facility. It is required prior to the issuance of a notice of compliance. All aspects of the new drug submission are critically reviewed by Health Canada. If a new

drug submission is found satisfactory, a notice of compliance is issued permitting the new drug to be sold for the approved use. In Canada, an establishment license must be obtained prior to marketing the product.

Health Canada has a policy of prioritizing the evaluation of new drug submissions for all drugs intended for serious or life-threatening diseases for which no drug product has received regulatory approval in Canada and for which there is reasonable scientific evidence indicating that the proposed new drug is safe and may provide effective treatment.

An exception to the foregoing requirements relating to the manufacture and sale of a new drug is the limited authorization that may be available for the sale of new drugs for emergency treatment. Under the special access program, Health Canada may authorize the sale of a quantity of a new drug for human use to a specific practitioner for the emergency treatment of a patient under the practitioner’s care. Prior to authorization, the practitioner must supply Health Canada with information concerning the medical emergency for which the new drug is required, such data as is in the possession of the practitioner with respect to the use, safety and efficacy of the new drug, the names of the institutions at which the new drug is to be used and such other information as may be requested by Health Canada. In addition, the practitioner must agree to report to both the drug manufacturer and Health Canada the results of the new drug’s use in the medical emergency, including information concerning adverse reactions, and must account to Health Canada for all quantities of the new drug made available.

The Canadian regulatory approval requirements for new drugs outlined above are similar to those of other major pharmaceutical markets. While testing carried out in Canada is often acceptable for regulatory submissions in other countries, individual regulatory authorities may request supplementary testing during their assessment of any submission. Therefore, the clinical testing conducted under Health Canada authorization or the approval of regulatory authorities of other countries may not be accepted by regulatory authorities outside Canada or other countries.

Approval of New Drugs in the United States

In the United States, the FDA regulates and investigates the manufacturing, testing and sale of new drugs. New drugs require FDA approval of an NDA prior to commercial sale. For certain biological products, a Biological License Application (“BLA”) must be obtained prior to marketing and batch release. As in Canada, to obtain marketing approval, data from adequate and well-controlled human clinical trials, demonstrating to the FDA’s satisfaction a new drug’s safety and effectiveness for its intended use, are required. Data are generated in studies conducted pursuant to an investigational new drug (“IND”) submission, similar to that required for a clinical trial application in Canada. Clinical trials with human subjects are classified as Phase 1, Phase 2, Phase 3 or a combination thereof. In a marketing application, the manufacturer must also demonstrate the identity, potency, quality, and purity of the new drug's active ingredients, and the stability of those ingredients. Further, the manufacturing facilities, equipment, processes and quality controls for the new drug must comply with the FDA’s current cGMP regulations for drugs both in a pre-licensing inspection before product licensing and in subsequent periodic inspections after licensing. An establishment license grants the sponsor permission to fabricate, package, label, distribute, import, wholesale or test the newly approved drug.

Federally regulated trials must be approved and monitored by an independent committee of doctors, scientists, advocates, and others to ensure safety and ethical standards, IRBs or ERBs. The review boards study and approve all study-related documents before a clinical trial begins and also carefully monitor data to detect benefit or harm, and validity of results.

Post-Approval Regulation

The monitoring of a new drug does not cease once it is on the market. For example, a manufacturer of a new drug must report any new information received concerning serious side effects, as well as the failure of the new drug to produce desired effects. If Health Canada determines it to be in the interest of public health, a notice of compliance for a new drug may be suspended and the new drug may be removed from the market.

A post surveillance program involves clinical trials conducted after a drug is marketed (referred to as Phase 4 studies in the United States) and is an important source of information on as yet undetected adverse outcomes, especially in populations that may not have been involved in the premarketing trials (e.g., children, the elderly, pregnant women) and the drug’s long-term morbidity and mortality profile. Regulatory authorities may require companies to conduct Phase 4 studies as a condition of market approval. Companies often conduct post-marketing studies in the absence of a regulatory mandate.

The foregoing description summarizes the requirements for a new drug to be approved for marketing in North America. The EMA and the Japanese Pharmaceuticals and Medical Devices Agency are also important regulatory authorities in drug development. Together with the FDA, they are the three International Conference on Harmonization parties that oversee the three largest markets for drug sales.

Information About Our Executive Officers

Aptose’s leadership team comprises accomplished industry, financial and clinical research professionals who are dedicated to building a comprehensive anticancer drug pipeline and clinical development programs focused on targeted therapeutics directed against dysregulated oncogenic processes in patients with life. The team includes our President, Chairman and Chief Executive Officer, our Senior Vice President, Chief Financial Officer and Chief Business Officer, and our Chief Medical Officer.

William G. Rice, Ph.D., age 67, joined Aptose as Chairman, President and Chief Executive Officer in October 2013. Dr. Rice brings more than 25 years of C-level executive, operational, business development, financial, and R&D experience in the biotech industry to Aptose. Prior to joining Aptose, Dr. Rice served as the President, Chief Executive Officer and Chairman of the board of Cylene Pharmaceuticals, Inc., a private biotechnology company, from 2003 to 2013. Prior to Cylene, Dr. Rice was the founder, President, Chief Executive Officer and Director of Achillion Pharmaceuticals, Inc. from 1998 to 2003. He also served as Senior Scientist and Head of the Drug Mechanism Laboratory at the National Cancer Institute-Frederick National Laboratory for Cancer Research from 1992 to 1998 and served as a faculty member in the division of Pediatric Hematology and Oncology at Emory University School of Medicine from 1989 to 1992. Dr. Rice performed his postdoctoral training in the Division of Hematology/Oncology in the Department of Internal Medicine at the University of Michigan Medical Center, prior to which he earned his Ph.D. in Biochemistry from Emory University Department of Biochemistry.

Fletcher Payne, age 63, joined Aptose as Senior Vice President, Chief Business Officer, Chief Financial Officer (“CFO”) and Corporate Secretary in June 2022. With over 25 years of experience in the healthcare sector, Mr. Payne has held several CFO and senior management positions at biotech companies, as well as roles in finance and accounting. He has overseen legal, corporate development, and licensing functions. Throughout his career, he has successfully executed a diverse range of business transactions totaling more than $3.7 billion, with a focus on clinical testing, oncology, neurological conditions, and orphan disease indications. Mr. Payne most recently served as CFO of Syapse, where he successfully completed several financing transactions and oversaw the company’s accounting, finance, corporate development, and legal functions. Previously, he served as CFO at Catalyst Biosciences, a publicly traded biotech company. Mr. Payne has also held CFO roles and senior financial positions at CytomX Therapeutics, Plexxikon Inc., Rinat Neuroscience Corporation, Dynavax Technologies Corporation, and Cell Genesys, among others. He earned a Bachelor of Science in Finance from the Haas School of Business at the University of California, Berkeley.

Rafael Bejar, M.D, Ph.D., age 54, joined Aptose as Senior Vice President and Chief Medical Officer in January 2020. Dr. Bejar is an internationally recognized physician scientist with extensive research and clinical experience in the area of hematologic malignancies. Dr. Bejar joined Aptose from UC San Diego (“UCSD”) where he began working in 2012. He continues to serve at UCSD as an Associate Professor of Clinical Medicine, caring for patients and maintaining a research laboratory focused on translational studies of myeloid malignancies and also serves and is an independent consultant as an advisor and Chair of Independent Data Monitoring Committees for other pharmaceutical companies. At UCSD, he founded the MDS Center of Excellence and led the Hematology Disease Team from 2017 to 2019. There he has directed several clinical studies and served as an advisor for numerous companies including Celgene (now BMS), Takeda, AbbVie, Astex, Genoptix (now NeoGenomics), Keros, Servier, Geron, Forty Seven (now Gilead), PersImmune, Epizyme (now Ipsen) and Daiichi-Sankyo. Outside UCSD, Dr. Bejar sits on the Scientific Advisory Board for the MDS Foundation, is a prior member of the National Comprehensive Cancer Network

Guidelines Committee and has led projects for the International Working Group for MDS. He is frequently invited to speak at national and international meetings and has published articles in a variety of journals including The New England Journal of Medicine, Journal of Clinical Oncology, Leukemia (where he is an Associate Editor), Blood, and BloodAdvances. Dr. Bejar completed his fellowship in the Massachusetts General Hospital Cancer Center/Dana-Farber Cancer Institute program and has been board certified in Internal Medicine, Hematology, and Oncology. He completed his internship in Internal Medicine at the University of Chicago followed by his residency at the Brigham and Women’s Hospital in Boston where he later served as a Medical Chief Resident and an Instructor in Hematology. He holds an M.D. degree and a Neuroscience Ph.D. from UCSD and a B.S. in Physics from MIT.

Corporate Information

Our headquarters are located at 66 Wellington Street West, Suite 5300, TD Bank Tower Box 48, Toronto, Ontario, MK5 1E6, Canada, and our executive offices are located at 12770 High Bluff Drive, Suite 120, San Diego, CA 92130 (telephone: 858-926-2730).

We file annual, quarterly, current reports, proxy statements and other information with the SEC. The SEC maintains an Internet site that contains our public filings and other information regarding the Company, at www.sec.gov. We make these reports available free of charge at our website http://www.aptose.com (under the “Investors — Financial Information” caption).

We are also a reporting issuer under the securities laws of every province of Canada.

Cautionary Note Regarding Forward-Looking Statements and Risk Factor Summary

This Annual Report on Form 10-K contains forward-looking statements within the meaning of the United States Private Securities Litigation Reform Act of 1995 and “forward-looking information” within the meaning of applicable Canadian securities law. We refer to such forward-looking statements and forward-looking information collectively as “forward-looking statements”. These statements relate to future events or future performance and reflect our expectations and assumptions regarding our growth, results of operations, performance and business prospects and opportunities. Such forward-looking statements reflect our current beliefs and are based on information currently available to us. In some cases, forward-looking statements can be identified by terminology such as “may”, “would”, “could”, “will”, “should”, “expect”, “plan”, “intend”, “anticipate”, “believe”, “estimate”, “predict”, “potential”, “continue” or the negative of these terms or other similar expressions concerning matters that are not historical facts. The forward-looking statements in this Annual Report on Form 10-K include, among others, statements regarding our future operating results, economic performance and product development efforts and statements in respect of:

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the proposed Arrangement and its expected terms, benefits, timing and closing, including receipt of required approvals, and satisfaction of other customary closing conditions, and the anticipated timing thereof;

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our ability to obtain the capital we require to fund research and operations and to continue as a going concern;

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our business strategy;

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our clinical development plans;

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our plans to conduct clinical trials and preclinical programs;

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our ability to accrue appropriate numbers and types of patients;

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our reliance on external contract research/manufacturing organizations for certain activities;

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our plans to secure and maintain strategic partnerships to assist in the further development of our product candidates and to build our pipeline;

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our ability to file and maintain intellectual property to protect our pharmaceutical assets;

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potential exposure to legal actions and potential need to take action against other entities;

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our expectations regarding the progress and the successful and timely completion of the various stages of our drug discovery, drug synthesis and formulation, preclinical and clinical studies and the regulatory approval process;

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our plans, objectives, expectations, and intentions; and

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other statements including words such as “anticipate,” “contemplate,” “continue,” “believe,” “plan,” “estimate,” “expect,” “intend,” “will,” “should,” “may,” and other similar expressions.

The forward-looking statements contained in this Annual Report on Form 10-K reflect our current views with respect to future events, are subject to significant risks and uncertainties, and are based upon a number of estimates and assumptions that, while considered reasonable by us, are inherently subject to significant business, economic, competitive, political and social uncertainties and contingencies. Forward-looking statements contained in this Annual Report on Form 10-K are made as of the date of this Annual Report on Form 10-K.

Except as required under applicable securities legislation, we undertake no obligation to publicly update or revise forward-looking statements, whether as a result of new information, future events or otherwise.

Risk Factor Summary

Many factors could cause our actual results, performance or achievements to be materially different from any future results, performance, or achievements that may be expressed or implied by such forward-looking statements, including, among others:

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possibility that the Arrangement will not be completed on the terms and conditions, or on the timing, currently contemplated, and that it may not be completed at all, due to a failure to obtain or satisfy, in a timely manner or otherwise;

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the failure to complete the Arrangement, which could negatively impact the price of the Common Shares or otherwise affect the business of the Company;

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the possibility that Aptose and Hanmi may be the targets of legal claims, securities class actions, derivative lawsuits and other claims and negative publicity related to the Arrangement;

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the dedication of significant resources to pursuing the Arrangement and the restrictions imposed on the Corporation while the Arrangement is pending;

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the uncertainty surrounding the Arrangement could adversely affect the Company’s retention of business partners and key employees;

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the payment by the Company of an expense fee if the Arrangement Agreement is terminated in certain circumstances;

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CCAA Plan if the Arrangement is not completed;

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certain directors and executive officers of the Company may have interests in the Arrangement that may be different from, or in addition to, the interests of shareholders generally;

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our ability to continue as a going concern;

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our lack of product revenues;

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our need to raise substantial additional capital in the near future and that we may be unable to raise such funds when needed and on acceptable terms;

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our early stage of development, particularly the inherent risks and uncertainties associated with (i) developing new drug candidates generally, (ii) demonstrating the safety and efficacy of these drug candidates in clinical studies in humans, and (iii) obtaining regulatory approval to commercialize these drug candidates;

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further equity financing, which may substantially dilute the interests of our existing shareholders;

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clinical studies and regulatory approvals of our drug candidates are subject to delays, and may not be completed or granted on expected timetables, if at all, and such delays may increase our costs and could substantially harm our business;

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our reliance on external contract research/manufacturing organizations for certain activities and if we are subject to quality, cost, or delivery issues with the preclinical and clinical grade materials supplied by contract manufacturers, our business operations could suffer significant harm;

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clinical studies are long, expensive and uncertain processes and the United States Food and Drug Administration, or “FDA”, or other similar foreign regulatory agencies that we are required to report to, may ultimately not approve any of our product candidates;

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our ability to comply with applicable regulations and standards;

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our inability to achieve our projected development goals in the time frames we announce and expect;

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difficulties in enrolling patients for clinical trials may lead to delays or cancellations of our clinical trials;

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impact of government spending cuts;

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our reliance on third parties to conduct and monitor our preclinical studies;

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our ability to attract and retain key personnel, including key executives and scientists;

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any misconduct or improper activities by our employees;

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our exposure to exchange rate risk;

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our ability to commercialize our business attributed to negative results from clinical trials;

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the marketplace may not accept our products or product candidates due to the intense competition and technological change in the biotechnical and pharmaceuticals, and we may not be able to compete successfully against other companies in our industries and achieve profitability;

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our ability to obtain and maintain patent protection;

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our ability to afford substantial costs incurred with defending our intellectual property;

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our ability to protect our intellectual property rights and not infringe on the intellectual property rights of others;

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our business is subject to potential product liability and other claims;

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potential exposure to legal actions and potential need to take action against other entities;

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commercialization limitations imposed by intellectual property rights owned or controlled by third parties;

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our ability to maintain adequate insurance at acceptable costs;

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our ability to find and enter into agreements with potential partners;

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extensive government regulation;

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data security incidents and privacy breaches could result in increased costs and reputational harm;

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our Common Share price has been and is likely to continue to be volatile;

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future sales of our Common Shares by us or by our existing shareholders could cause our Common Share price to drop;

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changing global market and financial conditions;

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difficulties by non-Canadian investors to obtain and enforce judgments against us because of our Canadian incorporation and presence;

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any failures to maintain an effective system of internal control may result in material misstatements of our financial statements, or cause us to fail to meet our reporting obligations or fail to prevent fraud;

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our broad discretion in how we use the proceeds of the sale of Common Shares, if any;

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our ability to expand our business through the acquisition of companies or businesses; and

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other risks detailed from time-to-time in our on-going filings with the SEC and Canadian securities regulators, and those which are discussed in Item 1A. Risk Factors in this Annual Report on Form 10-K.

Should one or more of these risks or uncertainties materialize, or should the assumptions described in the Item 1A. Risk Factors in this Annual Report on Form 10-K underlying those forward-looking statements prove incorrect, actual results may vary materially from those described in the forward-looking statements.

Although we have attempted to identify factors that could cause actual actions, events or results to differ materially from those described in forward-looking statements, there may be other factors that cause actions, events or results not anticipated, estimated or intended. Forward-looking statements are based upon our beliefs, estimates and opinions at the time they are made and we undertake no obligation to update forward-looking statements if these beliefs, estimates and opinions or circumstances should change, except as required by applicable law. There can be no assurance that forward-looking statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking statements.

We qualify all the forward-looking statements contained in this Annual Report on Form 10-K by the foregoing cautionary statements.

ITEM 1A. RISK FACTORS

Risk Factors and Uncertainties

Any of the risks and uncertainties described below could significantly and negatively affect our business, prospects, financial condition, operating results, or credit ratings, which could cause the trading price of our Common Shares to decline. Additional risks and uncertainties not presently known to us, or risks that we currently consider immaterial, could also impair our business operations or financial condition. The following discussion of risk factors contains “forward-looking” statements, as discussed above.

Risks Related to the Plan of Arrangement

There is no assurance when or if the Arrangement will be completed.

The completion of the Arrangement is subject to the satisfaction or waiver of a number of conditions as set forth in the Arrangement Agreement, including, among others (i) approval of the Arrangement Agreement by the shareholders of the Company, (ii) obtaining certain regulatory and governmental approvals, and (iii) the absence of legal restraints prohibiting the completion of the Arrangement. There can be no assurance as to when these conditions will be satisfied or waived, if at all, or that other events will not intervene to delay or result in the failure to close the Arrangement. A substantial delay in obtaining satisfactory approvals or the imposition of unfavorable terms or conditions in any government or regulatory approvals could have an adverse effect on the business or financial condition of the Company. In addition, if for any reason the conditions to the Arrangement are not satisfied or waived or if the Arrangement is not completed for any reason, the Company’s ongoing business and financial results may be adversely affected, the market price of the Common Shares may be adversely affected.

Failure to complete the Arrangement could negatively impact the market price of the Company's Common Shares and the Company's future business and financial results.

If the Arrangement is not completed for any reason, the Company’s ongoing business and financial results may be adversely affected. In addition, if the Arrangement is not completed, the Company will be subject to a number of additional risks, including the following:

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Under the terms of the Arrangement Agreement, in certain circumstances, if the Arrangement is not completed by reason of certain circumstances attributable to the Company, the Company may be required to pay a termination fee;

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The price of the Common Shares may decline to the extent that the current market price of the Common Shares reflects a market assumption that the Arrangement will be completed and that the related benefits will be realized, or as a result of the market’s perceptions that the Arrangement was not consummated due to an adverse change in the Company’s business or financial condition; and

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Whether or not the Arrangement is completed, the pending Arrangement could adversely affect the Company’s operations because matters relating to the Arrangement require substantial commitments of time and resources by the Company’s management and employees which could otherwise have been devoted to other opportunities that may have been beneficial to the Company.

The Company cannot guarantee when, or whether, the Arrangement will be completed, that there will not be a delay in the completion of the Arrangement or that all or any of the anticipated benefits of the Arrangement will be obtained. If the Arrangement is not completed or is delayed, the Company may experience the risks discussed above which may adversely affect the Company’s business, financial results and share price.

The application of interim operating covenants may restrict the Company's ability to pursue certain opportunities.

Pursuant to the Arrangement Agreement, the Company has agreed to certain interim operating covenants intended to ensure that the Company carries on business in the ordinary course consistent with past practice, except as required or expressly authorized by the Arrangement Agreement or any applicable law. These operating covenants

cover a broad range of activities and business practices. Consequently, it is possible that a business opportunity will arise that is out of the ordinary course or is not consistent with past practices, and that the Company will not be able to pursue or undertake the opportunity due to its covenants in the Arrangement Agreement.

Aptose and Hanmi may be the targets of legal claims, securities class actions, derivative lawsuits and other claims and negative publicity related to the Arrangement.

Aptose and Hanmi may be the target of lawsuits that could delay or prevent the Arrangement from being consummated or result in significant additional costs. Securities class action lawsuits and derivative lawsuits are often brought against companies that have entered into an agreement to acquire a public company or to be acquired. Third parties may also attempt to bring claims against Aptose or Hanmi in an attempt to delay or block the consummation of the Arrangement or to seek other remedies, including additional monetary compensation. Even if the lawsuits are unsuccessful or meritless, significant financial resources and attention from management can be required to defend against these claims and proceedings may result in a delay to closing the Arrangement. Such proceedings, among other events, could also subject Aptose to negative press coverage or public scrutiny that could impact the ability of Aptose and Hanmi to consummate the Arrangement, as well as negatively impacting the Company’s existing business performance and operations.

Lawsuits that may be brought against Aptose, Hanmi or their respective directors which could seek, among other things, injunctive relief or other equitable relief, including a request to rescind parts of the Arrangement Agreement already implemented and to otherwise enjoin the parties from consummating the Arrangement. One of the conditions to the closing of the Arrangement is that no law (including injunction or judgments) is in effect that makes the Arrangement illegal or enjoins or prohibits Aptose or Hanmi from consummating the Arrangement. Consequently, if a plaintiff is successful in obtaining an injunction prohibiting completion of the Arrangement, that injunction may delay or prevent the Arrangement from being completed within the expected timeframe or at all, which may adversely affect Aptose’s and Hanmi’s respective business, financial position, results of operations and cash flows.

No Equity Interest in the Company Following the Arrangement

Following the Arrangement, shareholders of Aptose will no longer hold any of the Common Shares. Shareholders will forgo any future increase in value that might result from future growth and the potential achievement of the Company’s long-term plans, including, but not limited to, future royalty or related payments related to in-licensing of our product candidates

The Diversion of the Attention of Management

The pendency of the Arrangement could cause the attention of Management to be diverted from the day-to-day operations of the Company. These disruptions could be exacerbated by any delay in the completion of the Arrangement and could have an adverse effect on the business, operating results or prospects of the Company.

Parties with which we and Hanmi do business may experience uncertainty associated with the Arrangement, including with respect to current or future business relationships with us, Hanmi or the combined company. Our and Hanmi’s relationships may be subject to disruption as customers, suppliers and other persons with whom we and Hanmi have a business relationship may delay or defer certain business decisions or might decide to seek to terminate, change or renegotiate their relationships with us or Hanmi, as applicable, or consider entering into business relationships with parties other than us or Hanmi. In addition, our current and prospective associates may experience uncertainty about their future roles, which might adversely affect our ability to attract and retain key personnel and key management and other employees may be difficult to retain or may become distracted from day-to-day operations because matters related to the Arrangement may require substantial commitments of their time and resources. These disruptions could have an adverse effect on the results of operations, cash flows and financial position of us, Hanmi or the combined company following the completion of the Arrangement, including an adverse effect on our ability to realize the expected benefits of the Arrangement. The risk, and adverse effect, of any disruption could be exacerbated by a delay in the completion of the Arrangement or the termination of the Arrangement Agreement.

Uncertainty Surrounding the Arrangement

The Arrangement is dependent upon satisfaction of various conditions, and as a result, its completion is subject to uncertainty. In response to this uncertainty, the Company’s business and clinical trial partners may delay or defer decisions concerning the Company. Uncertainty surrounding the Arrangement could also adversely affect the retention of key employees of the Company. Any change, delay or deferral of those decisions by business and clinical partners and any loss of key employees could negatively impact the Company’s business, operations and prospects, regardless of whether the Arrangement is ultimately completed.

The Company will incur costs and may have to pay an Expense Fee.

Certain costs relating to the Arrangement, such as certain legal, accounting and financial advisor fees, must be paid by the Company even if the Arrangement is not completed. If the Arrangement is not completed for certain reasons, the Company may also be required to pay an expense fee of C$300,000 to Hanmi. If the Company is required to pay this expense fee, the financial condition and ability of the Corporation to fund current operations could be materially adversely affected.

CCAA Plan in the Event Arrangement is not Completed

If the Arrangement Agreement is terminated in certain circumstances, the Corporation will be required to immediately implement the Alternative CCAA Proceedings (as such term is defined in the Arrangement Agreement). In the event that the Company commences Alternative CCAA Proceedings, shareholders of the Company may not be entitled to receive any consideration on their Common Shares.

Certain directors and executive officers of the Company may have interests in the Arrangement that may be different from, or in addition to, the interests of Shareholders generally.

Certain directors and officers of the Company may have interests in the Arrangement that may be different from, or in addition to, the interests of shareholders generally, including, but not limited to, the receipt of certain bonuses upon the completion of the Arrangement, indemnification and insurance coverage and golden parachute compensation.

Risks Related to our Business

There is substantial doubt that we can remain a going concern over the next twelve months.

As of the filing date, the Company does not have sufficient liquidity to fund operations and relies on advances made by Hanmi. In order for the Company to meet its capital requirements, and continue to operate, additional financing will be necessary. The Company is evaluating strategies to obtain the required additional funding for future operations. These strategies may include, but are not limited to, obtaining equity financing, and restructuring of operations to decrease expenses. However, given the challenges in the U.S. and global financial markets, that may impact the Company's ability to raise financing in the capital markets, the Company may be unable to access further equity when needed, if at all. As the Company is primarily pursuing one compound that is licensed from a related party with significant licensing payments who will have influence on the Company, other investors may not be willing to invest in the Company. As such, there can be no assurance that the Company will be able to obtain additional liquidity when needed or under acceptable terms, if at all. The consolidated financial statements do not reflect any adjustments to the carrying amounts and classification of assets, liabilities, and reported expenses that may be necessary if the Company were unable to continue as a going concern. Such adjustments may be material. (See footnote 2.(b) Basis of presentation - Going Concern.)

We are an early-stage development company with no revenues from product sales.

We are at an early stage of development. None of our potential products have obtained regulatory approval for commercial use and sale in any country, and as such, no revenues have resulted from product sales. Significant additional investment will be necessary to complete the development of any of our product candidates. Preclinical and clinical trial work must be completed before our potential products could be ready for use within the markets that we have identified. We may fail to develop any products, obtain regulatory approvals, enter or complete clinical trials or commercialize any products. We do not know whether any of our potential product development efforts will prove to be effective, meet applicable regulatory standards, obtain the requisite regulatory approvals, be capable of being manufactured at a reasonable cost or be accepted in the marketplace and assuming the Arrangement is completed, whether Hanmi will continue these development efforts and whether their development plans are consistent with ours.

The product candidate we are currently developing is not expected to be commercially viable for at least the next several years, and we may encounter unforeseen difficulties or delays in commercializing this product candidate. In addition, our potential products may not be effective or may cause undesirable side effects. In addition, if the Arrangement is completed, there is no guarantee that the integration efforts with Hanmi will be successful and whether those efforts will result in delays or changes to the development strategy.

Our product candidates require significant funding to reach regulatory approval assuming positive clinical results. We are currently conducting Phase 1 clinical trials with our lead product candidate, tuspetinib. Significant additional capital will be necessary to complete the Phase 1 clinical trials, and if required, Phase 2 or Phase 3 clinical trials. Such funding for our product candidates may be difficult, or impossible to raise in the public or private markets or through partnerships. If funding or partnerships are not readily attainable, the development of our product candidates may be significantly delayed or stopped altogether. The announcement of a delay or discontinuation of development of any of our product candidates could have a negative impact on our share price.

We need to raise additional capital.

APTOF US Equity

APTOF · 10-K · period ended 2025-12-31

Item 1. Business

ITEM 1A. RISK FACTORS

APTOF US Equity☆

APTOF · 10-K · period ended 2025-12-31

Item 1. Business

ITEM 1A. RISK FACTORS

APTOF US Equity