On June 12, 2020 Aptose Biosciences Inc. ("Aptose" or the "Company") (NASDAQ: APTO, TSX: APS), a clinical-stage company developing highly differentiated therapeutics targeting the underlying mechanisms of cancer, reported that new clinical data on CG-806, its oral, first-in-class FLT3/BTK cluster selective kinase inhibitor, was presented in a poster presentation at the 25th Congress of the European Hematology Association (EHA) (Free EHA Whitepaper), EHA (Free EHA Whitepaper)25 Virtual Congress (Press release, Aptose Biosciences, JUN 12, 2020, View Source [SID1234561034]).

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Early Clinical Findings from a Phase 1 a/b Dose Escalation Trial to Evaluate the Safety and Tolerability of CG-806 in Patients with Relapsed or Refractory CLL/SLL or Non-Hodgkin’s Lymphomas (EHA2020 Abstract# EP711) reviewed CG-806 data for eight patients (as of the data cut-off date on May 5, 2020) with relapsed or refractory chronic lymphocytic leukemia (CLL) / small lymphocytic lymphoma (SLL) or non-Hodgkin’s lymphoma in the first in-human Phase 1 a/b, open-label, single arm, multicenter dose-escalation clinical study. The poster is available on the posters and presentations section of the Aptose website here. For more information on the ongoing study, please visit www.clinicaltrials.gov here.

CG-806 was well-tolerated in patients treated at 150mg, 300mg and 450mg BID over multiple cycles, with no drug-related dose-limiting toxicities or serious adverse events. CG-806 treatment led to lymphocytosis in two CLL patients and delivered complete inhibition of phospho-BTK and multiple oncogenic survival pathways in all patients receiving ≥ 300mg BID. Plasma from CG-806 treated patients completely inhibited phospho-FLT3 in a plasma inhibitory activity (PIA) assay, and patients receiving ≥ 300mg BID achieved steady state PK levels known to be effective in murine tumor models.

"We are pleased by evidence of CG-806’s safety and tolerability, along with early indicators of pharmacologic activity," said William G. Rice, Ph.D., Chairman, President and Chief Executive Officer. "These data continue to support further dose escalation of CG-806 and in fact, since the data cut-off date, we have progressed to the 600mg dosing cohort. The findings also suggest that dose levels evaluated in this study may be therapeutic in patients with AML."

Separately, Aptose announced it has submitted an IND for a parallel Phase 1 a/b clinical study of CG-806 in patients with relapsed or refractory FLT3-mutant or FLT3-wildtype acute myeloid leukemia (AML).

About CG-806

CG-806 is an oral, first-in-class FLT3/BTK cluster selective kinase inhibitor and is in Phase 1 clinical studies for the treatment of hematologic malignancies. This small molecule demonstrates potent inhibition of wild type and all mutant forms of FLT3 (including internal tandem duplication, or ITD, and mutations of the receptor tyrosine kinase domain and gatekeeper region), cures animals of AML in the absence of toxicity in murine xenograft models, and represents a potential best-in-class therapeutic for patients with AML and other myeloid malignancies. Likewise, CG-806 demonstrates potent, non-covalent inhibition of the wild type and Cys481Ser (C481S) mutant forms of the BTK enzyme, as well as other oncogenic kinase pathways operative in B cell malignancies, suggesting CG-806 may be developed for various B cell malignancy patients (including CLL/SLL, FL, MCL, DLBCL and others) that are resistant/refractory/intolerant to covalent or other non-covalent BTK inhibitors. Because CG-806 targets key kinases/pathways operative in malignancies derived from the bone marrow, it is in development for B-cell cancers and AML.