Organic cation transporter (OCT) 2, multidrug and toxin extrusion protein (MATE) 1, and MATE2K mediate the renal secretion of various cationic drugs and can serve as the loci of drug-drug interactions (DDI). To support the evaluation of cynomolgus monkey as a surrogate model for studying human organic cation transporters, monkey genes were cloned and shown to have a high degree of amino acid sequence identity versus their human counterparts (93.7%, 94.7%, and 95.4% for OCT2, MATE1 and MATE2K, respectively). Subsequently, the 3 transporters were individually stably expressed in human embryonic kidney (HEK) 293 cells and their properties (substrate selectivity, time course, pH-dependence, and kinetics) were found to be comparable to the corresponding human form. For example, six known human cation transporter inhibitors, including pyrimethamine (PYR), showed generally similar IC50 values against the monkey transporters (within 6-fold). Consistent with the in vitro inhibition of metformin (MFM) transport by PYR (IC50 for cynomolgus OCT2, MATE1 and MATE2K; 1.2 ± 0.38, 0.17 ± 0.04 and 0.25 ± 0.04 μM, respectively), intravenous pretreatment of monkeys with PYR (0.5 mg/kg) decreased the clearance (54 ± 9%) and increased in the area under the plasma concentration-time curve of MFM (AUC ratio versus control = 2.23; 90% confidence interval of 1.57 to 3.17). These findings suggest that the cynomolgus monkey may have some utility in support of in vitro-in vivo extrapolations (IVIVEs) involving the inhibition of renal OCT2 and MATEs. In turn, cynomolgus monkey-enabled IVIVEs may inform human DDI risk assessment.