TPMT*7 is assigned no function based on limited evidence. Erythrocytes from an individual genotyped TPMT*1/*7 exhibited intermediate activity (9711875, 9831928). In vitro studies using mammalian cell systems found that TPMT.7 enzymatic activity is either comparable (16220112) or decreased by 90% (13679074, 1870894) relative to TPMT.1, and protein expression levels are comparable to TPMT.1 in mammalian (16220112, 18708949) and yeast cells (13679074). Additionally, studies agree that TPMT.7 exhibited decreased affinity for 6-TG in vitro (13679074, 18708949). One out of ten variant effect predictors tested by CPIC staff predicts that the TPMT*7-defining SNV, c.681T>G (p.H227Q), impairs protein function. Despite conflicting in vitro evidence, the experts agreed to assign no function based on the available clinical data.