NAT2*69 is assigned decreased function based on moderate evidence. NAT2*TBD is characterized by the core SNVs c.341T>C (p.I114T) and c.589C>T (p.R197X). c.589C>T results in the amino acid change p.R197X, introducing a premature stop codon leading to the expression of a truncated protein product that is predicted to be nonfunctional (19164093, 29273096). Four out of four variant effect predictors tested by CPIC staff predict that c.589C>T (p.R197X) impairs function. c.341T>C (p.I114T) defines NAT2*5 which has been extensively studied, exhibiting decreased N-acetyltransferase activity both in vivo and in vitro. In vitro studies also show that NAT2*5 (which contains the core SNV c.341T>C, p.I114T) is subjected to enhanced protein degradation by the proteasome (15564878). Thus, NAT2*TBD would presumably be degraded in the same manner. Additionally, five out of nine variant effect predictors tested by CPIC staff predict that c.341T>C (p.I114T) impairs protein function. NAT2*TBD is assigned decreased function based on c.341T>C. Despite this, the combinatorial effects associated with c.341T>C and c.589C>T are uncertain.