New selective and allosteric FLT3 inhibitors show efficacy against resistant acute myeloid leukemia cells.

Activating FLT3 mutations confer a poor prognosis in acute myeloid leukemia (AML). FLT3 inhibitors significantly improved the clinical outcomes of FLT3-mutated AML. However, all clinically approved inhibitors target the ATP-binding pocket of FLT3. The acquired FLT3 mutations in the ATP-binding pocket, including mutations at D835 and F691, are common mechanisms of leukemia relapse. Using druggable site prediction (DSP) and high-throughput virtual screening, we revealed that the predicted site 1 region was promising for allosteric inhibitor development, and F-17 was identified as the first potential allosteric FLT3 inhibitor. F-17 exhibited high affinity for site 1 in an ATP non-competitive manner. KINOMEscan analysis showed that F-17 was significantly selective toward FLT3 over other homologous kinases of the RTK family. Moreover, F-17 showed potent selectivity and inhibition activity for FLT3-mutated cells both in vitro and in vivo. Collectively, the work provided a new insight for FLT3 inhibitor development.