A dual inhibitor overcomes drug-resistant FLT3-ITD acute myeloid leukemia

Abstract

FLT3 mutations are the most frequently identified genetic alterations in acute myeloid leukemia (AML) and are associated with poor prognosis. Multiple FLT3 inhibitors are in various stages of clinical evaluation. However, resistance to FLT3 inhibitors resulting from acquired point mutations in tyrosine kinase domain (TKD) have limited the sustained efficacy of treatments, and a “gatekeeper” mutation (F691L) is resistant to most available FLT3 inhibitors. Thus, new FLT3 inhibitors against both FLT3 internal tandem duplication (FLT3-ITD) and FLT3-TKD mutations (including F691L) are urgently sought. Herein, we identified KX2-391 as a dual FLT3 and tubulin inhibitor and investigated its efficacy and mechanisms in overcoming drug-resistant FLT3-ITD-TKD mutations in AML. KX2-391 exhibited potent growth inhibitory and apoptosis promoting effects on diverse AML cell lines harboring FLT3-ITD mutations and AC220-resistant mutations at the D835 and F691 residues in TKD and inhibited FLT3 phosphorylation and its downstream signaling targets. Orally administered KX2-391 significantly prolonged the survival of a murine leukemia model induced by FLT3-ITD-F691L. KX2-391 also significantly inhibited the growth of 4 primary AML cells expressing FLT3-ITD and 2 primary AML cells expressing FLT3-ITD-D835Y. Our preclinical data highlight KX2-391 as a promising FLT3 inhibitor for the treatment of AML patients harboring FLT3 mutations, especially refractory/relapsed patients with F691L and other FLT3-TKD mutations.

Insights on Cancer Cell Inhibition, Subcellular Activities, and Kinase Profile of Phenylacetamides Pending 1H-Imidazol-5-One Variants

“…In general, our findings suggest that KIM-161 could simultaneously inhibit signaling at multiple nodes originating from various tumor microenvironment cues. The direct target(s) of this compound has not been fully understood in as much as tirbanibulin is still revealing its polypharmacology nature ( Wang et al, 2021 ). Our work with KIM-161 proved that changes in the KX2-391 skeleton changes the cytotoxic profile from dual Src/tubulin inhibition to other targets.…”

“…Nevertheless, it is rare to find a clinically relevant kinase inhibitor that does not bind to other kinases, an approach commonly known as the polypharmacology (multi-targeted) kinase inhibitors ( Hartmann et al, 2009 ). KX2-391 itself was recently found to inhibit a mutated FLT3 kinase ( Wang et al, 2021 ). Therefore, we decided to investigate a change of the biphenyl core of KX series to a related system aiming to: a) study the SAR of KX scaffold extending beyond the biphenyl-4-( N -benzyl)acetamide scaffold (KX1-136, Figure 1B ), b) monitor the effect of replacing the outer ring of the biaryl system of KX series on kinase activities and specificities, and c) attempt to identify novel molecular leads with potent anticancer activities that are not necessarily dependent on Src/tubulin inhibition ( Figure 1B ).…”

Rapid and Sensitive Diagnosis of Drug-Resistant FLT3-F691L Mutation by CRISPR Detection

“…Although rarely observed in AML patients, FLT3 gene F691L mutation shows universal resistance to all available FLT3 inhibitors. Therefore, F691L mutation becomes a crucial detection item for treatment decisions ( Albers et al, 2013 ; Smith et al, 2015 ; Yamaura et al, 2018 ; Wang et al, 2021 ). Furthermore, earlier identification of drug-resistant mutations will help better understand the progression of the disease, and enable properly targeted treatment and more durable remissions for patients.…”

Overcoming Resistance: FLT3 Inhibitors Past, Present, Future and the Challenge of Cure

“…Wang P. et al identified and analyzed the in vitro efficacy of a dual oral FLT3 and tubulin inhibitor KX2-391, with very interesting effects on resistant FLT3mut AML cell lines (D835 and F691L). It also effectively reduced leukemic growth of FLT3-ITD-F691L, FLT3-ITD and FLT3-ITD-D835Y mut AML cells in a xenograft leukemia model [ 96 ].…”