NAT2*59 is assigned decreased function based on moderate evidence. NAT2*59 is characterized by the core SNVs c.475T>A (p.W159R), c.803G>A (p.R268K), and c.857G>A (p.G286E). c.803G>A (p.R268K) defines NAT2*4, formerly considered the reference allele, which has repeatedly shown increased function in vivo and in vitro. There is no literature describing function for c.475T>A (p.W159R). Eight out of ten variant effect predictors tested by CPIC staff predict that c.475T>A (p.W159R) impairs protein function. c.857G>A (p.G286E) defines NAT2*7 which has been extensively studied, exhibiting decreased N-acetyltransferase activity both in vivo and in vitro. Ten out of ten variant effect predictors tested by CPIC staff predict that c.857G>A (p.G286E) is neutral for protein function. However, published in silico modeling indicates that c.857G>A (p.G286E) disrupts the size/shape of the protein's active site (18680467). Thus, NAT2*59 is assigned decreased function based on c.857G>A. Despite this, the combinatorial effects associated with c.475T>A and c.857G>A are uncertain.