Based on this foundation, the authors suggest that use of forodesine – an inhibitor of purine nucleoside phosphorylase (PNP), which degrades deoxyguanosine – in combination with exogenous deoxyguanosine would act synergistically in patients with SAMHD1 deficiency due to an accumulation of cytotoxic dGTP, which could be exploited in the treatment of CLL. This evidence concerns the gene PNP and B-cell chronic lymphocytic leukemia.