CHEK1 and myelodysplastic syndrome: *USP7 inhibition: a) upregulates Gelsolin to induce differentiation of MDS cells [33]; b) reduces the viability of primary AML cells and tumour burden in vivo in PDX models [13, 16]; c) delays MLL‐AF9‐induced leukaemia in vivo in human leukaemia xenografts [16]. *USP7 deubiquitinates and stabilises CHK1 in AML cells [13]. *USP7 interacts with PRC1.1 complex and its catalytic activity is required for PRC1.1 stability [16]. *USP7 deubiquitinates and stabilises BCR‐ABL to promote the survival of CML cells [22]. *USP7 is differential expressed in MDS [4].