NAMPT INHIBITION SELECTIVELY TARGETS MDS MYELOBLASTS IN HIGH-RISK MDS WITH MONOSOMY 7 OR DEL(7Q)

Monosomy 7 and deletion of the q arm of chromosome 7 (-7/-7q) are high-risk markers in myelodysplastic syndromes (MDS). We previously showed that blasts with -7/-7q from patients with acute myeloid leukemia (AML) are exceptionally sensitive to NAMPT inhibitors, with the sensitivity caused by NAMPT gene haploinsufficiency as a result of - 7/-7q. The objective of this study was to investigate whether blasts from patients with -7/-7q MDS are similarly susceptible to NAMPT inhibition. We first assessed the sensitivity of MDS samples to NAMPT inhibition using data from ex vivo cell viability-based drug sensitivity assays, which showed that MDS samples were more sensitive to NAMPT inhibition compared to healthy donor samples and that a MDS sample with -7/-7q was the most sensitive to NAMPT inhibition. We further evaluated the efficacy of NAMPT inhibitors on different leukemic and healthy cell populations using a flow cytometry-based drug sensitivity assay. Leukemic cell populations from -7/-7q samples were highly sensitive to NAMPT inhibition and were more sensitive than cells from non -7/-7q samples. Additionally, we combined NAMPT inhibitor KPT-9274 with BCL2 inhibitor venetoclax, which resulted in significantly more leukemic cell killing than the NAMPT inhibitor alone. MDS samples with -7/-7q also showed significantly lower NAMPT expression compared to the non -7/-7q samples, indicative of haploinsufficient gene expression profile. The results from this study show that NAMPT inhibitors can effectively target -7/-7q MDS blasts ex vivo and the findings are in line with earlier studies in AML, suggesting that patients with high-risk MDS, especially those with -7/-7q, could benefit from NAMPT inhibitors.