Notably, no patient had a homozygous form of TPMT or NUDT15. More importantly, patients who harbor defective alleles of TMPT and NUDT15 genes required a significantly lower dose of the planned dose of 6-MP compared to the wild-type carriers of these alleles (Figure 1), with 6-MP dose intensity in the one child with the NUDT15 CT genotype being less than that reported in Asian patients with ALL (Yang et al., 2015; Zhou et al., 2018). This evidence concerns the gene TPMT and acute lymphoblastic leukemia.