Inosine Triphosphate Pyrophosphatase Genotype Research Articles

Association of inosine triphosphate pyrophosphatase gene polymorphisms with ribavirin combined with direct-acting antiviral agent in treatment of hepatitis C patients with hemolytic anemia

Objective To investigate the influencing factors for ribavirin (RBV)-induced hemolytic anemia in the treatment of chronic hepatitis C, and to provide a reference for the early prediction of ribavirin-related hemolytic anemia in clinical practice. Methods A total of 49 patients with chronic hepatitis C who attended or were hospitalized in Hebei Petrochina Central Hospital from January 2018 to July 2019 and received antiviral therapy with direct-acting antiviral agent (DAA) and RBV were enrolled, with a major allele of C allele and a minor allele of A allele at the rs1127354 locus of the inosine triphosphate pyrophosphatase (ITPA) gene, and the patients with AA and AC genotypes were compared with those with CC genotype. During treatment, RBV was reduced to 600 mg when hemoglobin (Hb) level was Results A total of 49 patients were enrolled in this study, among whom 22 had chronic hepatitis C and 27 had liver cirrhosis, with a sustained virologic response (SVR) rate of 95.9%. The dose of RBV was reduced in 3 patients (2 in the AA/AC group and 1 in the CC group) due to anemia, and RBV was withdrawn in 3 patients (1 in the AA/AC group and 2 in the CC group); all these 6 patients had liver cirrhosis and finally achieved SVR. During the anti-HCV therapy with DAA+RBV, there was relatively mild RBV-related hemolysis, and the maximum reduction in Hb from baseline was compared between the patients with AA/AC genotype at ITPA rs1127354 and those with CC genotype, which showed no significant difference between the two groups (Z=-0.18, P=0.87). Conclusion During the treatment with RBV+DAA, RBV is withdrawn or reduced for liver cirrhosis patients due to anemia, and no obvious statistical relation is observed between ITPA genotype and the maximum reduction in Hb from baseline. Therefore, detection of ITPA genotype before the application of RBV does not improve safety during treatment, and it is not recommended to perform conventional detection of ITPA gene polymorphisms.

Dosage of 6-Mercaptopurine in Relation to Genetic TPMT and ITPA Variants: Toward Individualized Pediatric Acute Lymphoblastic Leukemia Maintenance Treatment.

6-mercaptopurine (6-MP) is the mainstay in pediatric acute lymphoblastic leukemia (ALL) maintenance treatment. Variants in genes coding for thiopurine S-methyl transferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) are known to influence 6-MP metabolism. We determined TPMT and ITPA genotype and enzyme activity and the mean 6-MP doses during maintenance treatment in 40 children treated for ALL according to the Dutch Childhood Oncology Group (DCOG)-ALL11 protocol in the Radboudumc Amalia Children's Hospital, Nijmegen, The Netherlands. Patients with genetic variants in TPMT (N=3) had significantly lower TPMT enzyme activity (mean 0.46 vs. 0.72 µmol/mmol hemoglobin/h, P=0.005). Although the difference was not statistically significant, they were treated with lower mean 6-MP doses (28.1 mg/m [SD 25.5 mg/m] vs. 41.3 mg/m [SD 17.2 mg/m], P=0.375). In patients with genetic ITPA variants (N=21), ITPA enzyme activity was significantly lowered (mean 3.67 vs. 6.84 mmol/mmol hemoglobin/h, P<0.0005). The mean 6-MP doses did not differ between patients with and without variants in ITPA (40.0 mg/m [SD 20.3 mg/m] vs. 40.6 mg/m [SD 14.9 mg/m], P=0.663). The TPMT genotype, but not the ITPA genotype, should be considered as part of standard evaluation before starting ALL maintenance treatment.

Retrospective Data Analysis of the Influence of Age and Sex on TPMT Activity and Its Phenotype-Genotype Correlation.

Therapeutic efficacy and toxicity of thiopurine drugs (used as anticancer and immunosuppressant agents) are affected by thiopurine S-methyltransferase (TPMT) enzyme activity. TPMT genotype and/or phenotype is used to predict the risk for adverse effects before drug administration. Inosine triphosphate pyrophosphatase (ITPA) is another enzyme involved in thiopurine metabolism. In this study, we aimed to evaluate (a) frequency of various TPMT phenotypes and genotypes, (b) correlations between them, (c) influence of age and sex on TPMT activity, and (d) distribution of ITPA variants among various TPMT subgroups. TPMT enzyme activity was determined by LC-MS/MS. TPMT (*2,*3A-C) and ITPA (rs1127354, rs7270101) genotypes were determined using a customized TaqMan® OpenArray®. TPMT enzyme activity varied largely (6.3-90 U/mL). The frequency of low, intermediate, normal, and high activity was 0.5% (n = 230), 13.1% (n = 5998), 86.1% (n = 39448), and 0.28% (n = 126), respectively. No significant difference in TPMT activity in relation to age and sex was found. Genotype analysis revealed the frequency of variant TPMT alleles was 6.73% (*3A, n = 344), 0.05% (*3B, n = 2), 2.22% (*3C, n = 95), and 0.42% (*2, n = 19). Analysis of paired phenotype and genotype showed that TPMT activity in samples with variant allele(s) was significantly lower than those without variant alleles. Lastly, an equal distribution of ITPA variants was found among normal and abnormal TPMT activity. This retrospective data analysis demonstrated a clustering of variant TPMT genotypes with phenotypes, no significant influence of age and sex on TPMT activity, and an equal distribution of ITPA variants among various TPMT subgroups.

Effect of gender and ITPA polymorphisms on ribavirin-induced anemia in chronic hepatitis C patients

Single nucleotide polymorphisms (SNPs) in the inosine triphosphate pyrophosphatase (ITPA) gene protect patients from ribavirin induced anemia. To investigate other possible protective cofactors, gender differences were analyzed in patients with HCV genotype 1. Hemoglobin levels at baseline (Hb0) and the decline after 4 weeks of treatment (HbΔ4) were analyzed in 308 chronic hepatitis C patients participating in 5 Austrian trials (n=308, age 43.9 ± 11.1, male:185, female:123, BMI 25.3 ± 3.9, no cirrhosis: n=259, liver cirrhosis: n=49). All patients were treated with 180 μg peginterferon-alpha 2a and ribavirin [1000-1200 mg/d; females: mean (95% CI) 15.8 mg/kg (15.4-16.2); males 14.3 (14.1-14.5); p<0.001]. The SNPs rs6051702, rs1127354, rs7270101 and IL28B rs12979860 were analyzed by the StepOnePlus Real time PCR System. 188 were major alleles homozygotes; 95 (30.8%) carried the minor allele (C) of rs6051702, 47 (15.3%) of rs1127354 (A), and 69 (22.4%) of rs7270101 (C). The overall Hb0 was 14.8 g/dl (14.6-14.9) [mean (95%CI); females 13.7 (13.5-13.9); males 15.5; 15.3-15.6; p<0.001]. The overall HbΔ4 was greater in major allele homozygotes [2.8 g/dl (2.6-3.0)] than in minor allele carriers [1.6 (1.4-1.9); p<0.001]. Irrespective of the ITPA genotypes HbΔ4 was smaller in female [2.0 (1.7-2.2)] than in male patients [2.6 (2.4-2.8); p<0.001] and among females in premenopausal [1.5 (1.3-1.8)] than in postmenopausal patients [2.7 (2.3-3.1); p<0.001]. Irrespective of the protective effect of ITPA mutations, premenopausal females less likely develop ribavirin induced anemia.

Prevalence of IL‐28B and ITPA genotypes in Chinese Han population infected persistently with hepatitis C virus genotype 6 or HCV‐1

The geographic distribution, demographics, epidemiology, host factors, and clinical characteristics of persistent HCV-6 infection in China need further characterization. This multicenter study enrolled 63 patients with persistent HCV-6 infection and 63 patients with persistent HCV-1 infection as controls. Blood biochemistry, quantitation of HCV RNA levels, and identification of host IL-28B genotypes (rs12979860, rs8099917, and rs12980275) and ITPA genotype (rs1127354) were performed to estimate potential variability in host factors that may affect response to treatment. The mean HCV-6 RNA level (3.8E6 IU/ml) was significantly higher than that in patients infected with HCV-1 (1.7E6 IU/ml; P < 0.001). Patients persistently infected with HCV-6 had a high prevalence of IL-28B rs12979860 CC genotype (92.1%), rs8099917 TT genotype (93.7%), and rs12980275 AA genotype (90.5%). Their prevalence in patients infected with HCV-1 was only modestly lower (82.5%, 84.1%, and 82.5%, respectively; P > 0.05). The inosine triphosphate pyrophosphatase (ITPA) SNP rs1127354 CC genotype was present in 66.7% of patients infected with HCV-6, comparable to that of patients infected with HCV-1 (65.1%; P > 0.05). There were no differences in the liver function, proportion of hepatic cirrhosis patients or patients with increased serum glucose between these two groups. Persistent HCV-6 infection in Chinese Han is found mainly in the southern China. Chinese Han with chronic HCV-1 or HCV-6 infection have IL-28B genotypes, suggesting responsiveness to interferon-based pharmacotherapy. Most patients (67%) possess the ITPA genotype associated with susceptibility to ribavirin-induced hemolysis. The routes of transmission for HCV-6 genotype were more diversified than HCV-1 genotype. The outbreak of HCV-6 infection through blood transfusion progressed faster than HCV-1.

Efficacy of splenectomy in preventing anemia in patients with recurrent hepatitis C following liver transplantation is not dependent on inosine triphosphate pyrophosphatase genotype

A genetic polymorphism of inosine triphosphate pyrophosphatase (ITPA) has been associated with pegylated-interferon/ribavirin (PEG-IFN/RBV)-induced anemia in chronic hepatitis C patients. However, correlation of the genetic variant with anemia following liver transplantation has not been determined. Sixty-three hepatitis C virus (HCV)-positive patients who underwent liver transplantation and PEG-IFN/RBV therapy were enrolled. The rs1127354 was determined for each individual. There was no relationship with anemia or RBV dosage in patients carrying the CC allele (CC group, n = 43) and those carrying the CA allele (CA group, n = 20). The incidence of hemoglobin (Hb) decline >3 g/dL (CC: 4.7%, CA: 0%) was relatively low, whereas the incidence of Hb levels <10 g/dL (CC: 18.6%, CA: 30.0%) was high. Univariate analysis revealed that splenectomy inversely correlated with Hb levels <10 g/dL at 4 weeks (P = 0.04). Among the 22 patients who did not undergo splenectomy, the incidence of Hb levels <10 g/dL tended to be lower in the seven patients carrying the CA allele (28.6%) than in the 15 patients with the CC allele (60.0%). The ITPA genetic polymorphism does not correlate with post-transplant PEG-IFN/RBV-induced anemia. Splenectomy is useful in preventing anemia regardless of the ITPA genotype.

Polymorphism of the inosine triphosphate pyrophosphatase gene predicts ribavirin-induced anemia in chronic hepatitis C patients

Ribavirin (RBV)-induced anemia is a serious side effect of pegylated interferon (PEG-IFN) plus RBV therapy which is the standard care most effective for hepatitis C virus (HCV) infection. In the present study, we investigated the association of inosine triphosphate pyrophosphatase (ITPA) genotypes with RBV-induced hemoglobin (Hb) reduction in HCV patients treated with PEG-IFN/RBV therapy. The genotypes of the ITPA rs1127354 single nucleotide polymorphism were determined in 179 patients with HCV infection. Among them, 52 patients were treated with PEG-IFN/RBV. The frequency of the ITPA major allele (CC) was 76.3% and that of the minor allele (CA and AA) was 23.7%. A rapid decrease in Hb levels during the initial 4 weeks was observed in patients with the ITPA major allele (CC), but not in patients with the ITPA minor allele (C/A and AA). Hb levels at 4 weeks were significantly lower in patients with the ITPA major allele than the levels in patients with the minor allele. Out of the 41 patients, 6 (14.6%) with ITPA major allele had Hb levels <10 g/dl and 11 patients (26.8%) had a decline in Hb of >3 g/dl. None of the patients with the ITPA minor allele had such data. There were no significant differences in virological responses of HCV-RNA between patients with the ITPA major allele and those with the minor allele. In conclusion, the ITPA genotypes may be a useful marker for prediction of RBV-induced anemia.

Determinants of mercaptopurine toxicity in paediatric acute lymphoblastic leukemia maintenance therapy

6-mercaptopurine (6-MP) is used in the treatment of childhood acute lymphoblastic leukaemia (ALL). Its red blood cell (RBC) metabolite concentrations (6-thioguanine [6-TGN] and 6-methylmercaptopurine nucleotides [6-MMPN]) are related to drug response. We investigated the impact of non-genetic covariates and pharmacogenetic polymorphisms affecting thiopurine methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) on 6-MP metabolism and response. Sixty-six children with ALL treated according to EORTC 58951 protocol were included in this study. Six patients had a heterozygous genotype for the most common TPMT polymorphisms, nine for ITPA 94 C > A and 17 for ITPA IVS2+21 A > C. 6-MP metabolites concentrations were analyzed by mixed model analysis. During maintenance, steady-state RBC 6-TGN concentrations were lower in patients aged 6 years or younger (493 pmol/8 × 10(8) RBC) than in older children (600 pmol/8 × 10(8) RBC). 6-MMPN concentrations were low in patients with TPMT variant/wild-type ITPA (1862 pmol/8 × 10(8) RBC), intermediate in wild-type patients and high (16468 pmol/8 × 10(8) RBC) in patients wild-type TPMT/variant ITPA. A 6-MMPN threshold of 5000 pmol/8 × 10(8) RBC was associated with an increased risk of hepatotoxicity. In this study, age and both TPMT and ITPA genotypes influenced 6-MP metabolism. High 6-MMPN was associated with hepatotoxicity. These pharmacological tools should be used to monitor ALL treatment in children.

Influences of Thiopurine Methyltransferase Genotype and Activity on Thiopurine-induced Leukopenia in Korean Patients With Inflammatory Bowel Disease

Myelotoxicity has been shown to be very common in Korean patients with inflammatory bowel disease (IBD) during azathioprine (AZA) or 6-mercaptopurine (6-MP) treatment. The purpose of this study was to investigate the relative risk of the thiopurine methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) genotypes and TPMT activity for the development of leukopenia in Korean IBD patients during AZA/6-MP treatment. We retrospectively analyzed 286 Korean patients with IBD who had been treated with AZA/6-MP for at least 6 months between June 1996 and September 2006. Common TPMT mutations, including TPMT*1, *2, *3A, *3B, and *3C, and ITPA mutations, including 94C>A and IVS2+21A>C, were determined using a high-performance liquid chromatography method. TPMT activity was measured using liquid chromatography with coupled mass spectrometry/mass spectrometry. Leukopenia occurred in 118 cases (41.3%). TPMT *1/*3C was detected in 7 cases (2.4%), and ITPA 94 C>A was detected in 66 cases (23.1%), including 63 heterozygotes (22.1%) and 3 homozygotes (1.0%). The median TPMT activity was 9.3 U/mL (interquartile range 10.4, range 2.1 to 76.2). Cox regression analysis revealed that patients with heterozygous *3C type TPMT had a higher probability of leukopenia than those with wild type TPMT (P=0.02). Patients with intermediate TPMT activity had a lower probability of leukopenia than those with low activity (P=0.01). However, the ITPA genotype did not affect the risk of leukopenia. Our data showed that it could be helpful to examine TPMT genotypes and to measure TPMT activity in Korean patients taking AZA/6-MP to predict the development of leukopenia.

Inosine triphosphate pyrophosphatase 94C> A polymorphism: clinical implications for patients with systemic lupus erythematosus treated with azathioprine

Importance of the field: Azathioprine (AZA) has immunosuppressive property and has been widely used in organ transplantation and in several autoimmune diseases including systemic lupus erythematosus. The use of AZA is limited by the occurrence of adverse drug reactions (ADRs) leading to treatment discontinuation. Under AZA therapy, inosine triphosphate pyrophosphatase (ITPA) deficiency presumably leads to accumulation of unusual thioinosine metabolites with the potential for ADRs. Japanese patients require lower doses of AZA compared with Caucasian patients to achieve the same concentration of active metabolites. This ethnic difference in part is probably due to genetic polymorphisms of ITPA.Areas covered in this review: Relationships between ITPA genotype and enzyme activity, and efficacy and toxicity of AZA in both Caucasian and Asian populations are reviewed.Take home message: Clinical studies using a dose of < 1.5 mg/kg/day in various autoimmune diseases have shown no association between ITPA genotype and ADRs. In studies using higher doses, ITPA deficiency appears to increase the risk for AZA toxicity. Genotyping of ITPA may be useful to achieve dose optimization. It is important to maintain the dose of AZA < 1.5 mg/kg/day for Asian patients with ITPA 94A allele, with careful monitoring of the therapeutic efficacy.

Correlation of genotypes for thiopurine methyltransferase and inosine triphosphate pyrophosphatase with long-term clinical outcomes in Korean patients with inflammatory bowel diseases during treatment with thiopurine drugs

There is a lack of research describing the associations between thiopurine methyltransferase (TPMT)/inosine triphosphate pyrophosphatase (ITPA) genotypes and long-term clinical outcomes. We investigated whether TPMT/ITPA genotypes predicted long-term clinical response in Korean patients with inflammatory bowel diseases (IBDs) undergoing thiopurine treatment. A total of 204 patients with IBD in whom thiopurine treatment was indicated were enrolled and categorized by TPMT and ITPA genotypes. Long-term follow-up clinical data for these patients were analyzed with specific focus on disease relapse. Of the 204 patients, 162 (79.4%) patients using thiopurines achieved remission and were included in an analysis of long-term clinical outcomes. There were no significant differences in disease relapse-free survival between wild and mutant types of TPMT (P=0.903) or ITPA (P=0.392), according to the results of the log-rank analysis. Our study suggests that TPMT and ITPA genotypes may not affect the rates of disease relapse in IBD patients treated with thiopurines. Further studies are indicated to confirm the utility of TPMT/ITPA genotyping to guide clinicians formulating individualized treatments for IBD patients requiring thiopurine therapy.

Genetic Polymorphism of Inosine Triphosphate Pyrophosphatase Is a Determinant of Mercaptopurine Metabolism and Toxicity During Treatment for Acute Lymphoblastic Leukemia

The influence of genetic polymorphism in inosine triphosphate pyrophosphatase (ITPA) on thiopurine-induced adverse events has not been investigated in the context of combination chemotherapy for acute lymphoblastic leukemia (ALL). This study investigated the effects of a common ITPA variant allele (rs41320251) on mercaptopurine metabolism and toxicity during treatment of children with ALL. Significantly higher concentrations of methyl mercaptopurine nucleotides were found in patients with the nonfunctional ITPA allele. Moreover, there was a significantly higher probability of severe febrile neutropenia in patients with a variant ITPA allele among patients whose dose of mercaptopurine had been adjusted for TPMT genotype. In a cohort of patients whose mercaptopurine dose was not adjusted for TPMT phenotype, the TPMT genotype had a greater effect than the ITPA genotype. In conclusion, genetic polymorphism of ITPA is a significant determinant of mercaptopurine metabolism and of severe febrile neutropenia, after combination chemotherapy for ALL in which mercaptopurine doses are individualized on the basis of TPMT genotype.

Thiopurine-methyltransferase and inosine triphosphate pyrophosphatase polymorphism in a liver transplant recipient developing nodular regenerative hyperplasia on low-dose azathioprine

The enzymes thiopurine-methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) are involved in thiopurine metabolism. We describe a liver transplant recipient who presented with liver enzyme abnormalities after 78 months of low-dose azathioprine (AZA) therapy (less than 1 mg/kg). No underlying etiology of these abnormalities was identified after extensive analysis including repeated liver biopsy. Fifteen years after transplantation, the patient presented with variceal bleeding, liver biopsy showed nodular regenerative hyperplasia (NRH). TPMT*3C genotype was found in the patient's lymphocytes and heterozygous ITPA (94C>A) genotype was found in both patient and donor liver. These findings further emphasize the importance of pharmacogenetics in predicting NRH and other adverse events during AZA therapy. Furthermore, a high index of suspicion with early detection of NRH is crucial, as improvement seems only to occur in patients with compensated liver disease. Liver biopsy and discontinuation of AZA are recommended in case of liver enzyme abnormalities or signs of portal hypertension.

Inosine-Triphosphate-Pyrophosphatase Genotype Is a Determinant of Severe Fever with Neutropenia Following Treatment of Acute Lymphoblastic Leukemia with Combination Chemotherapy That Includes Mercaptopurine Adjusted for Thiopurine-S-Methyltransferase Genotype.

Germline polymorphisms can be significant determinants of toxicity to anti-leukemic therapy. For mercaptopurine (6MP) it is established that variant alleles of the thiopurine-S-methyl-transferase (TPMT) gene, resulting in low enzymatic activity, are associated with an increase in the concentration of thioguanine-nucleotide metabolites (TGN) and in the risk of hematotoxicity. Polymorphisms of genes encoding other enzymes involved in 6MP metabolism could also influence its pharmacokinetics and consequently its efficacy and toxicity. Among possible candidate genes, inosine-triphosphate-pyrophosphatase (ITPA) has been related to adverse events to thiopurine treatment of inflammatory bowel disease, but it has not been fully investigated for leukemia therapy. The aim of this study was to assess the association between severe life-threatening toxicities (Grade 3–4) during the continuation treatment of acute lymphoblastic leukemia (ALL) and the variant alleles of TPMT and ITPA genes, and the influence of these variant alleles on the concentration of 6MP metabolites, TGN and methylated nucleotides (MMPN). Patients with ALL on the St. Jude Total 13B protocol were assessed for toxicity according to NCI criteria. Relevant variant alleles of TPMT (SNPs rs1142345, rs1800462, rs1800660) and ITPA (SNP rs41320251) were determined using PCR assays. The association between the variant alleles and the development of adverse events during the continuation phase of treatment was assessed using weighted logistic regression. Concentrations of the two main metabolites of 6MP were measured in erythrocytes by HPLC; the association between genotypes and the concentrations of 6MP metabolites was evaluated using mixed linear effects models. TPMT and ITPA genotypes were determined for 233 patients; 13 (5.2%) were heterozygous for variant alleles of the TPMT gene and 31 (13.3%) for the ITPA gene; no patient had two variant alleles of either gene and 1 patient (0.4%) had a variant allele for both TPMT and ITPA. Since 6MP dose was individualized based on the TPMT variant allele among patients treated in the protocol, genetic polymorphisms of TPMT, not surprisingly, were not associated with toxicity. On the other hand, the presence of an ITPA variant allele was significantly associated with the incidence of Grade 3–4 fever with neutropenia in the univariate and in the multiple weighted logistic regression (odds ratio 3.0, 95% C.I. 1.2–7.8, p = 0.021). 6MP metabolites were measured in 257 samples from 108 patients, and the results revealed that variant alleles of both candidate genes were associated with changes in the concentration of the MMPN metabolites: TPMT with a reduction (p = 0.048) and ITPA with an increase (p = 0.047). Genetic polymorphism of ITPA rs41230251 is a significant determinant of severe and life-threatening fever with neutropenia and of 6MP metabolism in patients with ALL who are treated with 6MP doses individualized based on TPMT genotype.

Inosine Triphosphate Pyrophosphatase and Thiopurine S-Methyltransferase Genotypes Relationship to Azathioprine-Induced Myelosuppression

The use of azathioprine (AZA) in inflammatory bowel disease (IBD) patients is limited by toxicity, which occurs in up to 20% of treated patients. Mutations in the thiopurine S-methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) genes have been associated with the occurrence of AZA-related toxicity. The aim of our study was to determine the relative contribution of ITPA and TPMT mutations to the development of toxicity induced by AZA treatment in IBD patients. ITPA(94C>A, IVS2+21A>C) and TPMT (238G>C, 460G>A, and 719A>G) genotypes were assessed in 262 IBD patients (159 females, 103 males; 67 patients with ulcerative colitis, 195 patients with Crohn's disease) treated with AZA and were correlated with the development of leukopenia and hepatotoxicity. Leukopenia (leukocyte count, <3.0 x 10(9)/L) was observed in 4.6% of treated patients. The frequencies of mutant ITPA 94C>A and TPMT alleles were significantly higher in the leukopenic population compared with patients without leukopenia (16.7% and 5.4%, respectively, for ITPA 94C>A, and 20.8% and 4%, respectively, for TPMT). Moreover, the ITPA 94C>A and TPMT mutations predicted leukopenia: ITPA 94C>A odds ratio, 3.504; 95% confidence interval, 1.119-10.971 (P = .046); TPMT odds ratio, 6.316; 95% confidence interval, 2.141-18.634 (P = .004). Neither TPMT nor ITPA genotype predicted hepatotoxicity. ITPA 94C>A and TPMT polymorphisms are associated with AZA-related leukopenia in IBD patients.