CORRECTION — Aptosis Presents – GuruFocus.com

HM43239 Delivers New Full Remission at 160mg Dose in AML with Wildtype FLT3

New Luxeptinib “G3” Formulation Shows Encouraging Pharmacokinetic Results

SAN DIEGO and TORONTO, June 02, 2022 (GLOBE NEWSWIRE) — In a press release issued under the same title earlier today by Aptose Biosciences, Inc. (APTO, TSX: APS), please note that in the clinical results section updated with HM43239, fifth bullet point should read “Eight total responses, including seven CR and one PR, and favorable safety achieved at three separate dose levels (80mg, 120mg, 160mg)”. The corrected version follows:

Aptose Biosciences Inc. (“Aptose” or the “Company”) (APTO, TSX: APS), a clinical-stage precision oncology company developing highly differentiated oral kinase inhibitors to treat hematological malignancies, today published highlights from a key opinion leader (KOL) and company update event held today, June 2, 2022. The event included an up-to-date review clinical data from Aptose’s two investigational products in development for hematological malignancies: HM43239, an oral myeloid kinome inhibitor in an international Phase 1/2 trial in patients with relapsed or refractory acute myeloid leukemia (AML); and luxeptinib, an oral lymphoid and myeloid kinome inhibitor, in a phase 1 a/b trial in patients with relapsed or refractory B-cell malignancies, and in a separate phase 1 a/b trial in patients with relapsed or refractory AML or at risk of myelodysplastic syndrome (MDS).

Invited KOLs included Brian Druker, MD, of Oregon Health & Science University, Naval G. Daver, MD, of the University of Texas MD Anderson Cancer Center, and Brian Andrew Jonas, MD, Ph.D., of the University of California, Davis, Comprehensive Cancer Center, who discussed the current therapeutic landscape and unmet medical needs in the treatment of patients with acute myeloid leukemia (AML), as well as their experiences with experimental Aptose therapies .

Webcast of the presentation, including Q&A with guest KOLs, is available on Aptose’s website here.

Aptose has provided updated clinical results with HM43239, a potent suppressor of FLT3, SYK, JAK 1/2 and mutant forms of cKIT kinases operating in AML:

• Clinically validated in a highly diverse set of patients with relapsed/refractory (R/R) AML
• Fast Track designation supported by multiple complete remissions (CR) in FLT3 mutant refractory R/R AML, including those who have failed prior treatment with other FLT3 inhibitors
• New CRi at 160mg Dose in R/R AML Patient with Wild-Type FLT3 and Other Adverse Mutations
• Patient with CRi at 120mg dose bridged for hematopoietic stem cell transplant
• Eight total responses, including seven CR and one PR, and favorable safety achieved at three distinct dose levels (80 mg, 120 mg, 160 mg)
• One muscle weakness DLT (not rhabdomyolysis) reported at 200mg
• Three separate doses (80 mg, 120 mg, 160 mg) selected for expansion clinical trials
• Expansion single-agent clinical trials in AML with FLT3 mutation and without FLT3 mutation are expected to begin in the second half of 2022
• Clinical trials to extend the combination (HM43239 with venetoclax) in AML with FLT3 mutation and without FLT3 mutation should start in the first half of 2023

Aptose also reviewed clinical outcomes with the new G3 formulation of luxeptinib (Lux):

• The G3 formulation was designed to increase plasma exposure and reduce pill count
• Patients who have previously received the G3 formulation at 50 mg, 100 mg and 200 mg
• The G3 formulation is being tested in patients with BR/R cell malignancies and R/R AML
• Encouraging G3 formulation with rapid absorption and sustained exposures over 3 days
• Plan to transition from continuous G1 to G3 dosing if PK modeling studies are favorable

“We are pleased to announce today a new complete remission (CRi) with HM43239 in a patient with relapsed AML with wild-type FLT3 and mutations in various genes (RAS, BCOR, U2AF1, SETBP1), expanding the genotypes and the R/R AML patient population that may respond to this drug which has thus far been generally well tolerated,” said William G. Rice, Ph.D., Chairman, President and Chief “We have identified three doses and target patient populations for our next stage of expansion clinical trials with HM43239, as we move along a path toward registrational studies. For Lux, our new G3 formulation appears to be significantly better absorbed than the original formulation and we continue to believe in its potential as a unique inhibitor of the lymphoid and myeloid dual kinoma.

About Aptose

Aptose Biosciences is a clinical-stage biotechnology company engaged in the development of precision medicines addressing unmet medical needs in oncology, with an initial focus on hematology. The Company’s pipeline of small molecule cancer therapeutics includes products designed to provide single-agent efficacy and to enhance the efficacy of other cancer therapies and regimens without overlapping toxicities. The Company has two clinical-stage oral kinase inhibitors in development for hematological malignancies: HM43239, an oral myeloid kinome inhibitor in an international Phase 1/2 trial in patients with relapsed acute myeloid leukemia (AML) or refractory; and luxeptinib, an oral, lymphoid, and myeloid kinome inhibitor, in a Phase 1 a/b trial in patients with relapsed or refractory B-cell malignancies who have failed or are intolerant to standard therapies, and in a trial separate phase 1 a/b in patients with relapsed or refractory AML or high-risk myelodysplastic syndrome (MDS). For more information, please visit www.aptose.com.

Forward-looking statements

This press release contains forward-looking statements within the meaning of Canadian and United States securities laws, including, but not limited to, statements regarding clinical development plans and dose escalations, clinical potential, anticancer activity, therapeutic potential and applications and safety profile of HM43239 and luxeptinib; the potential expansion of the treatable population list for HM43239; the phase 1/2 clinical trial in AML HM43239; the Phase 1 a/b clinical trials of luxeptinib in B-cell malignancies and Phase 1 a/b AML and the next steps in these trials; the development of a new formulation (G3) for luxeptinib; upcoming updates regarding clinical trials; and statements relating to the Company’s plans, goals, expectations and intentions and other statements including words such as “continue”, “expect”, “intend”, “will”, “hope “, “should”, “could”, “could”, “potential” and other similar expressions. These statements reflect our current views regarding future events and are subject to risks and uncertainties and are necessarily based on a number of estimates and assumptions which, although considered reasonable by us, are inherently subject to change. important business, economic, competitive, political changes and social uncertainties and hazards. Many factors could cause our actual results, performance or achievements to be materially different from any future results, performance or achievements described in this press release. These factors could include, among others: our ability to obtain capital required for research and operations; the risks inherent in early-stage drug development, including demonstration of efficacy; development time/cost and regulatory approval process; the progress of our clinical trials; our ability to find and enter into agreements with potential partners; our ability to attract and retain key personnel; changing market and economic conditions; inability of new manufacturers to produce acceptable GMP batches in sufficient quantities; unexpected manufacturing defects; the potential impact of the COVID-19 pandemic and other risks detailed from time to time in our current reports, quarterly filings, annual information forms, annual reports and annual filings with Canadian securities regulators and the United States Securities and Exchange Commission.

Should one or more of these risks or uncertainties materialize, or should the assumptions set forth in the section titled “Risk Factors” in our filings with Canadian securities regulators and the United States Securities and Exchange Commission under should these forward-looking statements prove to be incorrect, the actual results may differ materially from those described herein. These forward-looking statements are made as of the date of this press release and we do not intend, and undertake no obligation, to update these forward-looking statements, except as required by law. We cannot assure you that such statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Investors are cautioned that forward-looking statements are not guarantees of future performance and, accordingly, investors are cautioned not to place undue reliance on forward-looking statements due to the inherent uncertainty therein.