Thiopurine therapy, commonly used in autoimmune conditions, can be complicated by life-threatening leukopenia. This leukopenia is associated with genetic variation in TPMT (encoding thiopurine S-methyltransferase). Despite a lower frequency of TPMT mutations in Asians, the incidence of thiopurine-induced leukopenia is higher in Asians than in individuals of European descent. Here we performed an Immunochip-based 2-stage association study in 978 Korean subjects with Crohn’s disease treated with thiopurines. We identified a nonsynonymous SNP in NUDT15 (encoding p.Arg139Cys) that was strongly associated with thiopurine-induced early leukopenia (odds ratio (OR) = 35.6; Pcombined = 4.88 × 10−94). In Koreans, this variant demonstrated sensitivity and specificity of 89.4% and 93.2%, respectively, for thiopurine-induced early leukopenia (in comparison to 12.1% and 97.6% for TPMT variants). Although rare, this SNP was also strongly associated with thiopurine-induced leukopenia in subjects with inflammatory bowel disease of European descent (OR = 9.50; P = 4.64 × 10−4). Thus, NUDT15 is a pharmacogenetic determinant for thiopurine-induced leukopenia in diverse populations.

BACKGROUND & AIMS: This study compared pharmacokinetics, symptomatic and endoscopic efficacy, safety, and immunogenicity of a subcutaneous formulation of the infliximab biosimilar CT-P13 (CT-P13 SC) vs intravenous CT-P13 (CT-P13 IV) in patients with inflammatory bowel disease (IBD). METHODS: This randomized, multicenter, open-label, parallel-group, phase 1 study enrolled tumor necrosis factor inhibitor-naïve patients with active ulcerative colitis (total Mayo score 6-12 points with endoscopic subscore 2) or Crohn's disease (Crohn's Disease Activity Index 220-450 points) at 50 centers. After CT-P13 IV induction at Week (W) 0/ W2, patients were randomized (1:1) to receive CT-P13 SC every 2 weeks (q2w) from W6 to W54 or CT-P13 IV every 8 weeks from W6 to W22. At W30, all patients receiving CT-P13 IV switched to CT-P13 SC q2w until W54. The primary endpoint was noninferiority of CT-P13 SC to CT-P13 IV for observed predose CT-P13 concentration at W22 (C trough,W22 ), concluded if the lower bound of the 2-sided 90% confidence interval (CI) for the ratio of geometric least-squares means exceeded 80%. RESULTS: Overall, 66 and 65 patients were randomized to CT-P13 SC and CT-P13 IV, respectively. The primary endpoint of noninferiority was met with a geometric least-squares means ratio for C trough,W22 of 1154.17% (90% CI 786.37-1694.00; n ¼ 59 [CT-P13 SC]; n ¼ 57 [CT-P13 IV]). W30/W54 clinical remission rates were comparable between arms. Other efficacy,