CYP2C9*39 is assigned no function based on limited evidence. Multiple in vitro studies found CYP2C9*39 demonstrated decreased clearance with numerous substrates compared to wildtype (24077631, 24118918, 25142737, 25144335, 25476996, 25832633, 25951663, 25884291, 27163851, 23844998). Therefore, consensus among experts was no function with an activity value of 0 based on limited evidence as it was determined the phenotypes containing this allele would be clinically distinct from phenotypes comprising normal function or decreased function alleles.