A metabolism-specific drug-repurposing screen reveals itraconazole as a potent OXPHOS inhibitor in acute myeloid leukemia

ABSTRACT: Targeting mitochondrial oxidative phosphorylation (OXPHOS) enhances the effects of standard chemotherapy and overcomes treatment resistance in preclinical models of acute myeloid leukemia (AML). So far, the few clinically available OXPHOS inhibitors have shown adverse effects or limited potency in clinical trials; therefore, the identification of safe and effective drugs that target mitochondrial metabolism in AML is critical. Here, we performed a high-throughput drug-repurposing screen designed to identify clinically applicable OXPHOS-specific inhibitors through nutrient sensing. We uncover itraconazole, a US Food and Drug Administration-approved antifungal compound, as a potent OXPHOS inhibitor in AML cells. Mechanistically, through stable isotope-assisted metabolomics and functional studies, we reveal that cytochrome P450 family 51 subfamily A member 1 (CYP51A1), which is part of the cytochrome P450 family and the prime target of azole antifungals, is involved in mitochondrial respiration and electron transport chain (ETC) complex I activity in AML cells. Critically, we demonstrate that itraconazole and related azole antifungals interfere with tricarboxylic acid cycle activity and inhibit OXPHOS through the inhibition of ETC complex I activity. Overexpression of yeast nicotinamide adenine dinucleotide (NADH) dehydrogenase-1 (NDI1) restored mitochondrial NADH oxidation and complex I activity following itraconazole treatment. Using patient-derived cells and preclinical xenograft models, we demonstrate that itraconazole targets therapy-resistant leukemic stem cells (LSCs) when used in combination with cytarabine, highlighting the repurposing potential for itraconazole as a clinically safe and effective therapeutic option for AML LSC eradication.