NUDT15*9 is assigned no function based on strong evidence. An in vitro study using a bacterial expression system found that NUDT15.9 enzymatic activity was undetectable and NUDT15.9 exhibited decreased protein thermostability compared to NUDT15.1 (28659275). NUDT15*1/*9 patients exhibit decreased tolerance to thiopurines (28659275) and experience severe hematotoxicity (30728528, 30806694). NUDT15*9 is characterized by the deletion c.50delGAGTCG (p.del17_18GV), which is predicted to impair protein function by CADD and PhD-SNPg