NAT2*70 is assigned decreased function based on moderate evidence. An individual heterozygous for NAT2*70 experienced drug-induced hepatotoxicity after standard isoniazid dosing (35588539). NAT2*70 is defined by the core SNVs c.341T>C (p.I114T) and c.596T>C (p.I199T). 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*70 would presumably be degraded in the same manner. Additionally, five out of ten variant effect predictors tested by CPIC staff predict that c.341T>C (p.I114T) impairs protein function. Three out of ten variant effect predictors tested by CPIC staff predict that c.596T>C (p.I199T) impairs protein function. NAT2*70 is assigned decreased function based on c.341T>C. Despite this, the combinatorial effects associated with c.341T>C and c.596T>C are uncertain.