NUDT15 codon 139 is the best pharmacogenetic marker for predicting thiopurine-induced severe adverse events in Japanese patients with inflammatory bowel disease: a multicenter study

Yoichi Kakuta, Yosuke Kawai, Daisuke Okamoto, Tetsuya Takagawa, Kentaro Ikeya, Hirotake Sakuraba, Atsushi Nishida, Shoko Nakagawa, Miki Miura, Takahiko Toyonaga, Kei Onodera, Masaru Shinozaki, Yoh Ishiguro, Shinta Mizuno, Masahiro Takahara, Shunichi Yanai, Ryota Hokari, Tomoo Nakagawa, Hiroshi Araki, Satoshi Motoya, Takeo Naito, Rintaro Moroi, Hisashi Shiga, Katsuya Endo, Taku Kobayashi, Makoto Naganuma, Sakiko Hiraoka, Takayuki Matsumoto, Shiro Nakamura, Hiroshi Nakase, Tadakazu Hisamatsu, Makoto Sasaki, Hiroyuki Hanai, Akira Andoh, Masao Nagasaki, Yoshitaka Kinouchi, Tooru Shimosegawa, Atsushi Masamune, Yasuo Suzuki, for the MENDEL study group

Despite NUDT15 variants showing significant association with thiopurine-induced adverse events (AEs) in Asians, it remains unclear which variants of NUDT15 or whether additional genetic variants should be tested to predict AEs. To clarify the best pharmacogenetic test to be used clinically, we performed association studies of NUDT15 variants and haplotypes with AEs, genome-wide association study (GWAS) to discover additional variants, and ROC analysis to select the model to predict severe AEs. Overall, 2630 patients with inflammatory bowel disease (IBD) were enrolled and genotyped for NUDT15 codon 139; 1291 patients were treated with thiopurines. diplotypes were analyzed in 970 patients, and GWASs of AEs were performed with 1221 patients using population-optimized genotyping array and imputation. We confirmed the association of NUDT15 p.Arg139Cys with leukopenia and alopecia (p = 2.20E-63, 1.32E-69, OR = 6.59, 12.1, respectively), and found a novel association with digestive symptoms (p = 6.39E-04, OR = 1.89). Time to leukopenia was significantly shorter, and when leukopenia was diagnosed, thiopurine doses were significantly lower in Arg/Cys and Cys/Cys than in Arg/Arg. In GWASs, no additional variants were found to be associated with thiopurine-induced AEs. Despite strong correlation of leukopenia frequency with estimated enzyme activities based on the diplotypes (r2 = 0.926, p = 0.0087), there were no significant differences in the AUCs of diplotypes from those of codon 139 to predict severe AEs (AUC = 0.916, 0.921, for acute severe leukopenia, AUC = 0.990, 0.991, for severe alopecia, respectively). Genotyping of NUDT15 codon 139 was sufficient to predict acute severe leukopenia and alopecia in Japanese patients with IBD.