Rational polypharmacological targeting of FLT3, JAK2, ABL, and ERK1 suppresses the adaptive resistance to FLT3 inhibitors in AML

Despite significant advancements in developing selective FMS-like tyrosine kinase 3 (FLT3) inhibitors, resistance to treatment is common even on continued therapy. Acquisition of on-target mutations or adaptation to MAPK, JAK2, and ABL signaling pathways drive treatment failure and disease relapse. Although combinatorial targeting of all escape routes in preclinical models demonstrated its efficacy, the clinical application is challenging owing to drug-drug interaction and differing pharmacokinetics of the inhibitors. We reasoned that selective polypharmacological targeting could lead to a durable response with reduced toxicity. A cell-based screening was carried out to identify inhibitors targeting FLT3, RAS-MAPK, BCR-ABL, and JAK2 to target the adaptive resistance observed with FLT3 inhibitors. Here, we show that pluripotin is an equipotent inhibitor of FLT3, BCR-ABL, and JAK2 in addition to inhibiting Ras-GAP and extracellular signal-regulated kinase 1 (ERK1). Structural modeling studies revealed that pluripotin is a type II kinase inhibitor that selectively binds with inactive conformations of FLT3, ABL, and JAK2. Pluripotin showed potent inhibitory activity on both mouse and human cells expressing FLT3ITD, including clinically challenging resistant mutations of the gatekeeper residue, F691L. Likewise, pluripotin suppressed the adaptive resistance conferred by the activation of RAS-MAPK pathways, BCR-ABL, and JAK2 signaling. Treatment with pluripotin curbed the progression of acute myeloid leukemia (AML) in multiple in vivo models including patient-derived primary AML cells in mouse xenotransplants. As a proof of concept, we demonstrate that targeted polypharmacological inhibition of key signaling nodes driving adaptive resistance can provide a durable response.