An example of relapse-associated SNPs affecting pharmacokinetics and pharmacodynamics of antileukemic agents. Genotype at ABCB1 SNP rs10264856 is associated with both ALL relapse (A) and dexamethasone apparent oral plasma clearance (B). Note that the C allele is linked to lower dexamethasone clearance and also lower cumulative incidence of relapse. The association of SNP genotype with clearance and with relapse was estimated by linear regression and the Fine and Gray hazard regression model, respectively. Dexamethasone clearance was determined in St Jude Total XV protocol at week 7 of continuation therapy, which is shown for those in the standard-/high-risk arm.