FDA Allows Human Trials of Aptose’s CG-806 Oral Compound for AML

FDA Allows Human Trials of Aptose’s CG-806 Oral Compound for AML

The U.S. Food and Drug Administration (FDA) has granted Aptose Biosciences an investigational new drug (IND) allowance that will let the company begin a human Phase 1a/b clinical study of CG-806, a potent oral compound to treat people with acute myeloid leukemia (AML).

Aptose says it plans to begin the trial in the second half of 2020, involving patients who have relapsed or are resistant (refractory) to current treatments. 

“Our strategy was to identify a starting dose of CG-806 that we believe could be therapeutically active in critically ill patients with relapsed or refractory AML,” Rafael Bejar, MD, PhD, Aptose’s senior vice president and chief medical officer, said in a press release. “We are pleased that the FDA has allowed us to initiate a clinical trial in these patients at a starting dose of 450mg [twice daily].”

“Despite recent advances in the treatment of AML, many patients relapse or remain refractory to current therapies leading to a poor overall prognosis,” he added.

Bejar said the investigational medication “offers hope” to people with AML whose disease has been difficult to treat.

CG-806 — which demonstrated efficacy in mouse models of leukemia — is a small molecule designed to block an enzyme called FMS-like tyrosine kinase 3 (FLT3) and all of its mutant forms (mutation-agnostic). These enzymes play a crucial role in tumor cell proliferation. In cancers such as AMLFLT3 is overproduced or mutated, which affects white blood cells, red blood cells, or platelets.

“Based on strong preclinical evidence of CG-806’s activity against AML – including demonstration of mutation-agnostic and genotype-agnostic potency, particularly compared against other FLT3 inhibitors, and its ability to safely cure AML in murine leukemia models – we believe CG-806 offers hope to the fragile and difficult-to-treat AML patient population,” Bejar said. 

FLT3 malfunction also underlies cancers that affect B-cells, the immune cells that produce antibodies that fight infections. CG-806 is currently being tested in a Phase 1 dose escalation study (NCT03893682) in people with B-cell malignancies, including chronic lymphocytic leukemia (CLL) and non-Hodgkin’s lymphomas, who have failed or are intolerant to current therapies.

“We continue to dose escalate in an ongoing study in patients with CLL and other B cell cancers, and are eager to advance this separate AML protocol through Institutional Review Boards at key clinical sites, recruit appropriate AML patients, and initiate dosing as soon as possible,” Bejar said. 

CG-806 also blocks normal and mutant forms of another enzyme called Bruton’s tyrosine kinase (BTK), which is overproduced or mutated in B-cell cancers, including CLL, mantle cell lymphoma, and diffuse large B cell lymphoma. Because CG-806 blocks these two key enzymes involved in bone marrow-related cancers, it is in development for both B-cell cancers and AML. 

Aptose is currently conducting a Phase 1b dose escalation study (NCT02267863) for an alternative therapy called APTO-253 in patients with relapsed or refractory AML or high-risk myelodysplastic syndrome. APTO-253 targets and suppresses the MYC oncogene, which is elevated in many different types of cancer, including AML.