Aptose Biosciences Inc.

A Novel Small Molecule MYC Inhibitor

APTO-253 is a novel small molecule that inhibits expression of the MYC oncogene, leading to cell cycle arrest and apoptosis in human-derived solid tumor and hematologic cancer cells. APTO-253 is under development as a novel therapy for acute myeloid leukemia (AML) and myelodysplastic syndrome (MDS).

About MDS and AML

MDS represents a group of closely related diseases arising from impaired hematopoietic stem cells in the bone marrow. Visually, the cells may appear abnormal, or dysplastic and patients with MDS may initially present with anemia, neutropenia, thrombocytopenia, or other hematological symptoms.

AML is a type of cancer that initiates in the bone marrow when stem cells or progenitor cells lose cell cycle control, anti-apoptotic factor, or other means to limit rampant proliferation. Leukemic cells can rapidly spread from the marrow to the bloodstream and quickly crowd out normal cells as they infiltrate other organs and tissue systems.

Addressing an Unmet Medical Need

~13K

Approximate MDS incidence per year or 4.4 to 4.6 cases per 100,000 people in the U.S.

~30%

Of MDS cases progress to AML, according to the American Cancer Society.

~35.7K

The estimated prevalence for AML as of January 1, 2010, according to the Leukemia & Lymphoma Society.

~18.8K

Patients with new AML diagnoses with about 10,460deaths in 2014, as projected by the American Cancer Society.

Pipeline

Product	Mechanism	Ownership	Indication	Preclinical	Clinical Proof-of-Concept	Pivotal
APTO-253	MYC	Aptose: WW	AML & MDS	complete AML & MDS Preclinical Phase complete	in progress Clinical Proof-of-Concept Phase in progress	not started Pivotal Phase not started

The Story Behind APTO-253

APTO-253 is a first-in-Class MYC Inhibitor currently in a phase 1b clinical trial for the treatment of patients with AML and MDS.

Tremendous Interest in Targeting MYC

MYC is a transcription factor that regulates cell growth, proliferation, differentiation, and apoptosis, and overexpression amplifies new sets of genes to promote oncogenesis. The MYC oncogene is overexpressed in hematologic cancers, including both myeloid and lymphoid tumors, and is typically associated with poor survival. Additionally, MYC is dysregulated or overexpressed in several solid tumors, including ovarian, breast, colorectal, pancreatic and gastric cancers.

APTO-253 as a Small Molecule MYC Inhibitor

APTO-253 does not target directly the MYC protein, but rather binds directly and selectively to a regulatory motif in the promoter of the MYC oncogene and dramatically down-regulates expression of the MYC protein in tumor cells, leading to apoptotic cell death. Thus, APTO-253 may serve as a safe and effective MYC inhibitor for MYC-driven or MYC-dependent tumors that combines well with other anti-tumor agents.

Clinical Development

Phase 1b Clinical Study of APTO-253

The phase 1b, multicenter, open-label dose-escalation clinical trial of APTO-253 is designed to assess the safety, tolerability, pharmacokinetics and pharmacodynamic responses and establish the recommended phase 2 dose of APTO-253 as a single agent. APTO-253 is being administered once weekly, over a 28-day cycle. The study is expected to enroll up to 20 patients with relapsed or refractory AML and high-risk MDS patients. The dose-escalation portion of the study is currently enrolling and is designed to then transition, as appropriate, to single-agent expansion cohorts in AML and MDS, followed by combination studies.

On Nov. 05, 2019, we announced we had completed dosing of the first three cohorts in our phase 1b trial with APTO-253, with only one patient required in each of the first two cohorts and three patients in the third cohort. In the patients on the first three dose cohorts, no drug-related adverse events had been observed, including no myelosuppression, and dosing was planned to continue to ascend until a maximum tolerated dose is reached. MYC biomarker data from AML and MDS patients in the first three cohorts continued to demonstrate reductions of MYC gene expression in their peripheral blood cells.

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Posters & Presentations

Our robust library includes numerous publications, including presentations, posters, and other media that provide additional information on our drug candidates, pre-clinical and clinical studies.

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