Synergy Between second-generation FLT3 inhibitors and the ERK1/2 inhibitor Ulixertinib in FLT3-ITD-mutated acute myeloid leukemia (AML) cells.

The FLT3 internal tandem duplication (FLT3-ITD) mutation is a critical molecular marker in acute myeloid leukemia (AML) and is closely associated with adverse patient prognosis. Although FLT3 inhibitors have been clinically applied, their therapeutic efficacy is constrained by reduced drug responsiveness and disease relapse. This study aims to investigate the underlying causes of the limited therapeutic efficacy of FLT3 inhibitors in FLT3-ITD-positive AML cells and propose feasible solutions. We screened datasets associated with Gilteritinib and Quizartinib in the Gene Expression Omnibus (GEO) database for enrichment analysis and validated potential key pathways that may limit their therapeutic efficacy through qPCR and Western blot. By assessing proliferation, apoptosis, and cell cycle in MV4-11 and MOLM-13 cells, we verified the combined effects of the ERK1/2 inhibitor Ulixertinib with Gilteritinib or Quizartinib, and further explored the underlying mechanisms via transcriptome sequencing. Gilteritinib and Quizartinib both significantly activated the RAS/MAPK pathway in FLT3-ITD-positive AML cells. While the ERK1/2 inhibitor Ulixertinib alone did not inhibit FLT3-ITD-positive AML cells viability, its combination with Gilteritinib or Quizartinib exhibited potent synergistic effects. Transcriptome sequencing revealed that these synergistic effects may stem from the regulation of gene expression such as PKD1, NR2E3, KDF1, and PRSS8 as well as modulation of ion channel activity. This in vitro study identifies aberrant activation of the RAS/MAPK pathway as a critical factor limiting the efficacy of FLT3 inhibitors in FLT3-ITD-positive AML and demonstrates the potent synergistic effects of Ulixertinib combined with FLT3 inhibitors in FLT3-ITD-positive AML cells, providing a novel therapeutic strategy for AML.