NRAS knockdown reverses monocytic cell state and resensitizes resistant FLT3-AML cells to gilteritinib

While the FLT3 inhibitor gilteritinib is initially effective in patients with FLT3-mutated acute myeloid leukemia (AML), patients invariably relapse within months of treatment. Gilteritinib resistance is commonly driven by the emergence of NRAS mutations and a shift towards a more monocytic cell state. We hypothesized that directly targeting and depleting NRAS protein would reverse these adaptive differentiation changes and restore therapeutic sensitivity. To test this, we utilized a mutation-agnostic antisense oligonucleotide (ASO) to selectively knock down NRAS expression across gilteritinib-resistant AML cell lines, in vivo cell-line-derived xenografts, and primary patient samples. NRAS ASO successfully resensitized gilteritinib resistant cells with multiple distinct NRAS mutations, displaying superior efficacy compared to downstream MEK inhibition. This therapeutic efficacy was independent of NRAS mutant variant allele frequency, suggesting that wild-type NRAS may also contribute to resistance. Comprehensive multi-omic profiling (transcriptomics, proteomics, phosphoproteomics) revealed that NRAS knockdown consistently reversed monocytic phenotype, shifting cells back toward a more primitive cell state. Monocytic differentiation and NRAS mutations are established drivers of resistance to diverse targeted regimens in AML, including FLT3, IDH, and BCL2 inhibitors, so we also tested venetoclax resistant primary cells with NRAS mutations. Resistant cells were resensitized to venetoclax after NRAS knockdown, suggesting that NRAS knockdown may be more broadly applicable in overcoming monocytic cell state and drug resistance in AML.