Rudd et al. reported that the ribonucleotide reductase inhibitors gemcitabine and hydroxyurea suppress the Ara-CTPase activity of SAMHD1 and overcome the SAMHD1-mediated barrier to Ara-C efficacy in both primary blasts and mouse models of AML [45]. The gene discussed is SAMHD1; the disease is acute myeloid leukemia.