Inosine Triphosphate Pyrophosphatase Gene Research Articles

Analysis of the NUDT15 gene and metabolites of azathioprine in Japanese patients with inflammatory bowel disease

BackgroundThiopurines continue to play an important role in the treatment of inflammatory bowel disease (IBD). It is well known that thiopurines can cause several adverse reactions. Especially, hematopoietic toxicity may lead to severe agranulocytosis. In a previous prospective study, we investigated the relationship between inosine triphosphate pyrophosphatase (ITPA) c.94c > a polymorphism, 6-thioguanine nucleotide (6-TGN) concentration and toxicity.MethodsTo clarify the cause of thiopurine toxicity, we analysed nucleoside disphosphate-linked moiety X-type motif 15 (NUDT15) gene polymorphisms, i.e., R139C, V18I, and V19_V19insGV, and measured 6-mercaptopurines and 6-methylmercaptopurines (6-MMP) using the archived blood samples collected from 49 IBD patients for our previous study.ResultsThe ITPA c.94c > a polymorphism was detected in 19 patients (38.7%, all heterozygous). The R139C polymorphism was found in 10 patients (20.4%, 1 homozygous, 9 heterozygous), V18_V19insGV in 7 patients (14.3%, all heterozygous), and V18I in 2 patients (4.08%, all heterozygous). Although R139C was more strongly associated with leukopenia than c.94c > a, there were no significant correlations with 6-TGN and 6-MMP levels, as for c.94c > a. The leukopenia incidence rates for each gene polymorphism were 0% in those with all wild-type genes, 21.4% for c.94c > a only, 42.9% for NUDT15 polymorphism (s) only, and 80.0% for both polymorphisms.ConclusionsAll cases of leukopenia were associated with ITPA c.94c > a and/or polymorphism of NUDT15 and the risk of developing leukopenia was synergistically increased by ITPA and NUDT15 gene polymorphism. However, there was no association between the level of azathioprine metabolites and these polymorphisms.

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.

A facile PCR-RFLP method for genotyping of ITPA rs1127354 and rs7270101 polymorphisms.

Inosine triphosphate pyrophosphatase (ITPA) gene single nucleotide polymorphisms (SNPs), rs1127354 and rs7270101, may cause a functional impairment in ITPase enzyme, resulting anemia protection in patients with chronic hepatitis C virus (HCV) infection undergoing ribavirin (RBV)-dependent regimens. The main purpose of this study was to provide and validate a simple, rapid, and inexpensive polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique for genotyping of ITPA rs1127354 and rs7270101 polymorphisms in chronic HCV-infected patients. In the current study, 100 Iranian patients with chronic hepatitis C were examined and genotyped for ITPA rs1127354 and rs7270101 gene polymorphisms. To genotype rs1127354 and rs7270101 polymorphisms, PCR-RFLP technique and sequencing technique were performed on these samples. To validate the PCR-RFLP method, the PCR-RFLP genotyping results should be 100% concordant with the PCR-sequencing results. The rs1127354 and rs7270101 polymorphisms of ITPA gene were genotyped by PCR-RFLP technique and sequencing simultaneously, and the results of both techniques were 100% concordant in all 100 patients. Both PCR-RFLP and sequencing techniques indicated that the genotypic frequency of rs7270101 was 80% AA, 19% AC and 1% CC, and for rs1127354 was 79% CC, 20% CA and 1% AA, respectively. We developed and validated a rapid and inexpensive PCR-RFLP technique for the detection of ITPA rs1127354 and rs7270101 gene polymorphisms.

Role of inosine triphosphate pyrophosphatase gene variant on fever incidence during zidovudine antiretroviral therapy.

Zidovudine, the antiretroviral drug used to treat HIV infection, commonly causes adverse effects, such as systemic fever and gastrointestinal alterations. In the present study, the potential role of inosine triphosphate pyrophosphatase (ITPA) gene variant on the incidence of adverse events during antiretroviral therapy (ART) of HIV with zidovudine was discussed. Individuals from Northeastern Brazil (N = 204) receiving treatment for HIV-1 infection were recruited. Zidovudine-related adverse effects developed during the treatment were registered. The rs1127354 polymorphism in the ITPA gene was genotyped using real-time PCR to assess whether this single nucleotide polymorphism was associated with the occurrence of zidovudine-related adverse effects. We observed a significant association between the ITPA variant genotype and the reported systemic fever (odds ratio = 7.17, 95% confidence interval = 1.19-43.15; P = 0.032). Zidovudine use could indirectly lead to an increase in the levels of inosine monophosphate in an antimetabolite-like manner, which is converted to inosine triphosphate (ITP). The rs1127354 variant caused a decrease in ITPA activity, thereby leading to ITP accumulation. This in turn resulted in cytotoxicity, which was manifested by neutropenia and fever. Therefore, we hypothesized a pharmacogenetic model involving the ITPA variant genotype in multifactorial components that act together to determine the onset of zidovudine-related adverse effects.

THU-298 - Inosine triphosphate pyrophosphatase enhances the effect of ribavirin on hepatitis C virus cell culture infection

Genetic variants of the inosine triphosphate pyrophosphatase gene (ITPA), resulting in decreased enzymatic activity of the corresponding enzyme, ITPase, are known to correlate with a decreased risk ...

Inosine Triphosphate Pyrophosphatase Gene Polymorphisms and Ribavirin-Induced Anemia in HCV Patients

In spite of the interferon (INF) redundancy in treating HCV, ribavirin (RBV) is still included with the new direct antiviral therapies. Ribavirin-induced hematological alterations had been referred to ITPA gene polymorphisms. Objective: Evaluate ITPA gene polymorphisms (rs1127354 and rs7270101) with development of anemia in chronic hepatitis C (CHC) Egyptian patients during treatment with pegylated-interferon (Peg-IFN) plus ribavirin (RBV). Methods: 100 Egyptian CHC patients treated with PEG-IFN/RBV were recruited, 55 patients developed anemia (Hb decline>2 g/dl), and other 45 would not developed anemia (Hb decline ≤ 2 g/dl) at week 12 throughout the treatment course. Routine laboratory investigations were done for all participates (HCV-Abs, HBs Ag, HCV-RNA levels, complete blood picture, liver and kidney function tests. Single nucleotide polymorphism (SNP) was done by ABI TaqMan allelic discrimination kit for ITPA polymorphisms (rs1127354 and rs7270101). Results: CC and AA were the most prevalent genotypes of SNPs rs1127354 and rs7270101 respectively among two studied groups. rs1127354 polymorphism was associated with Hb-decline at week 12 of treatment and with rs7270101 polymorphism for predicting platelet decline during treatment. Lower levels of platelet decline were detected with CC rs1127354 and AA rs7270101. Conclusion: While ITPA polymorphisms rs1127354 CC genotype carried a predilection of anemia occurrence in PEG-IFN/RBV HCV treated subjects, the minor allele rs1127354 AA plays a crucial role in their protection. Platelet decline was reported in both ITPA rs1127354 and rs7270101 polymorphisms. Screening for ITPA polymorphisms in Egyptian HCV patients would be of value in avoiding hematological disturbances and dose modulations in RBVbased therapies.

Enhancement of Nucleoside Production in Hirsutella sinensis Based on Biosynthetic Pathway Analysis.

To enhance nucleoside production in Hirsutella sinensis, the biosynthetic pathways of purine and pyrimidine nucleosides were constructed and verified. The differential expression analysis showed that purine nucleoside phosphorylase, inosine monophosphate dehydrogenase, and guanosine monophosphate synthase genes involved in purine nucleotide biosynthesis were significantly upregulated 16.56-fold, 8-fold, and 5.43-fold, respectively. Moreover, dihydroorotate dehydrogenase, uridine nucleosidase, uridine/cytidine monophosphate kinase, and inosine triphosphate pyrophosphatase genes participating in pyrimidine nucleoside biosynthesis were upregulated 4.53-fold, 10.63-fold, 4.26-fold, and 5.98-fold, respectively. To enhance the nucleoside production, precursors for synthesis of nucleosides were added based on the analysis of biosynthetic pathways. Uridine and cytidine contents, respectively, reached 5.04 mg/g and 3.54 mg/g when adding 2 mg/mL of ribose, resulting in an increase of 28.6% and 296% compared with the control, respectively. Meanwhile, uridine and cytidine contents, respectively, reached 10.83 mg/g 2.12 mg/g when adding 0.3 mg/mL of uracil, leading to an increase of 176.3% and 137.1%, respectively. This report indicated that fermentation regulation was an effective way to enhance the nucleoside production in H. sinensis based on biosynthetic pathway analysis.

Role of ITPA gene polymorphism in ribavirin-induced anemia and thrombocytopenia in Egyptian patients with chronic hepatitis C.

Ribavirin (RBV)-induced anemia is one of the major causes of dose reduction and discontinuation of therapy for chronic hepatitis C (CHC) patients. We investigated the role of inosine triphosphate pyrophosphatase (ITPA) single nucleotide polymorphism (SNP) (rs1127354) in predicting RBV-induced anemia and thrombocytopenia among Egyptian patients with CHC genotype 4 infection. One hundred and twenty Egyptian patients with CHC genotype 4 who had received standard of care combination therapy were enrolled in this study. Single nucleotide polymorphism at ITPA (rs1127354) was genotyped by real-time detection polymerase chain reaction. Hb levels between CC and non-CC groups were significantly different at weeks 4, 8, and 12. Hemoglobin decline was significantly higher among CC patient than non-CC patients at week 4 and week 8 of treatment. The RBV dose reduction was higher in CC than non-CC group. Platelet decline was significantly lower in CC patients than non-CC patients at baseline, 4, 12weeks only. Rs1127354 ITPA polymorphism was associated with RBV-induced anemia and thrombocytopenia in Egyptian patients with hepatitis C virus genotype 4 infection.

TPMT and ITPA genetic variants in Lithuanian inflammatory bowel disease patients: Prevalence and azathioprine-related side effects

PurposeInter-individual thiopurine metabolism variability can influence treatment outcomes in inflammatory bowel disease (IBD) patients. Genetic polymorphisms in thiopurine methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) were linked with toxicity of azathioprine (AZA). The aim of the study was to investigate frequencies of TPMT and ITPA polymorphisms in Lithuanian IBD patients and analyze their association with AZA-related adverse events. Materials/methodsPolymorphisms in TPMT (TPMT*2,*3B,*3C,*3A) and ITPA (rs1127354, rs7270101) genes were determined using PCR-RFLP and TaqMan® genotyping assays. 551 consecutive Lithuanian IBD patients were genotyped. The use of AZA and its side effects were assessed retrospectively according to hospital medical records. ResultsFrequencies of TPMT*3A, TPMT*3B and TPMT*3C alleles were 3.1%, 0.5% and 0.1%, respectively. TPMT*2 genetic variant was not detected in the study group. The distribution of minor alleles for ITPA rs1127354 and rs7270101 polymorphisms was 9.9% and 10.5%, respectively. AZA was prescribed in 82 patients and it provoked myelotoxicity in 11%, hepatotoxicity in 6.1%, dyspepsia in 6.1%, and pancreatitis in 3.6% of cases. Among patients who had AZA-related myelotoxicity, 11.1% were TPMT compound heterozygous, 44.4% had heterozygous genotype (P<0.01). Frequencies of ITPA minor alleles were similar among the patients with and without AZA-related side effects. ConclusionFrequencies of TPMT and ITPA variant alleles in Lithuanian IBD group were similar to those observed in the Northern-Eastern Europe Caucasian populations. Polymorphisms in TPMT might be associated with myelotoxicity and leukopenia in AZA treated patients, while ITPA variant alleles appear not to be linked with treatment-related side effects.

ITPA gene variant may protect against anemia induced during pegylated interferon Alfa and Ribavirin combination treatment in Ukrainian patients with chronic hepatitis C

The aim of this study was to clarify the association between the inosine triphosphate pyrophosphatase (ITPA) gene variants and PEG-IFNalpha/RBV combination treatment induced anemia in chronic hepatitis C (CHC) Ukrainian patients. The data were collected from 80 CHC patients with HCV genotype 1 infection. All study participants received standard doses of PEG-IFNalpha and RBV According to the Hb level changes patients were distributed into: case group--42 patients with combination treatment induced anemia, and control group--38 patients with no signs of anemia. Genotyping for ITPA gene rs1127354 and rs7270101 variants was performed using PCR followed by RFLP assay. Fisher's exact test was used to estimate the difference in genotype and allelic distribution. Distribution of rs 7270101 genotypes was not significantly different between groups of CHC patients with RB Vinduced anemia and without it. The frequency of rs1127354 A allele carriers was significantly higher (P < < 0,05) in group of CHC patients without anemia (23.7%) comparing to the group ofpatients with anemia (7.3%). The respective allele frequency in control group (13.2%) was almost 3-fold higher (P < 0,05) comparing to the case group (4.9%). Significant association of ITPA gene rs1127354 with protection against RB V-induced hemolytic anemia was found in Ukrainian patients with CHC infection. Rs1127354 variant may assist as a pharmacogenetic marker in HCV antiviral therapy correction for side effect avoidance..

Variants of the inosine triphosphate pyrophosphatase gene and relapse risk following treatment for HCV genotype 2/3

Variants of the inosine triphosphate pyrophosphatase gene and relapse risk following treatment for HCV genotype 2/3

Prevalence of TPMT and ITPA gene polymorphisms and effect on mercaptopurine dosage in Chilean children with acute lymphoblastic leukemia.

BackgroundMercaptopurine (6-MP) plays a pivotal role in treatment of childhood acute lymphoblastic leukemia (ALL); however, interindividual variability in toxicity of this drug due to genetic polymorphism in 6-MP metabolizing enzymes has been described. We determined the prevalence of the major genetic polymorphisms in 6-MP metabolizing enzymes in Chilean children with ALL.Methods103 Chilean pediatric patients with a confirmed diagnosis of ALL were enrolled. DNA was isolated from whole blood and genetic polymorphism in thiopurine S-methyltransferase (TPMT) and inosine triphosphate pyrophosphatase (ITPA) coding genes were detected by polymorphism chain reaction-restriction fragment length (PCR-RFLP) assay.ResultsThe total frequency of variant TPMT alleles was 8%. TPMT*2, TPMT*3A and TPMT*3B alleles were found in 0%, 7%, and 1% of patients, respectively. For ITPA, the frequency of P32T allele was 3%. We did not observe any homozygous variant for TPMT and ITPA alleles. We also analyzed a subgroup of 40 patients who completed the maintenance phase of ALL treatment, and we found that patients carrying a TPMT gene variant allele required a significantly lower median cumulative dosage and median daily dosage of 6-MP than patients carrying wild type alleles.ConclusionTMPT genotyping appears an important tool to further optimize 6-MP treatment design in Chilean patients with ALL.

Variants of the inosine triphosphate pyrophosphatase gene are associated with reduced relapse risk following treatment for HCV genotype 2/3

The present study evaluated the impact of variations in the inosine triphosphate pyrophosphatase (ITPase) gene (ITPA) on treatment outcome in patients with hepatitis C virus (HCV) genotype 2/3 infection receiving peginterferon-α2a and lower, conventional 800 mg daily dose of ribavirin. Previous studies using higher, weight-based ribavirin dosing report that patients carrying polymorphisms encoding reduced predicted ITPase activity show decreased risk of ribavirin-induced anemia but increased risk of thrombocytopenia, with no impact on elimination of virus. In all, 354 treatment-naïve HCV genotype 2/3-infected patients, enrolled in a phase III trial (NORDynamIC), were genotyped for ITPA (rs1127354 and rs7270101). Homo- or heterozygosity at Ars1127354 or Crs7270101 , entailing reduced ITPase activity, was observed in 37% of patients and was associated with increased likelihood of achieving sustained virological response (SVR) (P = 0.0003 in univariate and P = 0.0002 in multivariate analyses) accompanied by a reduced risk of relapse among treatment-adherent patients. The association between ITPA variants and SVR remained significant when patients were subdivided by the 12- and 24-week treatment duration arms, HCV genotype, fibrosis stage, and IL28B genotype, and was not secondary to improved adherence to therapy or less pronounced anemia. Gene variants predicting reduced predicted ITPase activity were also associated with decreased risk of anemia (P < 0.0001), increased risk of thrombocytopenia (P = 0.007), and lower ribavirin concentrations (P = 0.02). These findings demonstrate a novel ribavirin-like association between polymorphisms at ITPA and treatment efficacy in chronic hepatitis C mediated by reduced relapse risk. We hypothesize that patients (63%) being homozygous for both major alleles, leading to normal ITPase activity, may benefit more from the addition of ribavirin to present and future treatment regimens for HCV in spite of concomitant increased risk of anemia.

ITPA gene polymorphisms significantly affect hemoglobin decline and treatment outcomes in patients coinfected with HIV and HCV.

Published studies have described a strong association with a single-nucleotide polymorphism (SNP) in the inosine triphosphate pyrophosphatase (ITPA) gene and ribavirin (RBV)-induced hemolytic anemia in HCV-infected patients receiving pegylated interferon (pegIFN) and RBV. This study sought to evaluate the effect of these polymorphisms on anemia, hemoglobin reduction, HCV kinetics, and treatment outcomes. Sixty-three patients coinfected with HIV and HCV and 58 patients infected with HCV only were treated with pegIFN/RBV were genotyped using the ABI TaqMan allelic discrimination kit for the 2 ITPA SNP variants rs1127354 and rs7270101. A composite variable of ITPA deficiency using both SNPs was created as previously reported. Statistical analysis was performed using Mann-Whitney test or Chi square/Fishers exact test for categorical data and mixed model analysis for multiple variables. Thirty-five patients (30%) were predicted to have reduced ITPA activity. ITPA deficiency was found to be protective against the development of hemoglobin reduction >3 g/dl over the course of treatment. The rates of hemoglobin reduction >3 g/dl decreased in correlation with the severity of ITPA deficiency. ITPA deficiency was associated with slower hemoglobin decline early in treatment (week 4, P = 0.020) and rapid virologic response (RVR) at week 4 (P = 0.017) in patients coinfected with HIV and HCV. ITPA polymorphisms are associated with hemoglobin decline and in patients coinfected with HIV and HCV it is also associated with early virologic outcomes. Determination of ITPA polymorphisms may allow prediction of RBV-induced anemia and earlier initiation of supportive care to ensure optimal therapeutic outcomes.

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.

Association Between Adverse Effects Under Azathioprine Therapy and Inosine Triphosphate Pyrophosphatase Activity in Patients With Chronic Inflammatory Bowel Disease

Inosine triphosphate pyrophosphatase (ITPA) catalyzes the pyrophosphohydrolysis of inosine triphosphate to inosine monophosphate. Recently, single-nucleotide polymorphisms in the ITPA gene, associated with decreased enzyme activity, have been reported. Some clinical studies have demonstrated that the 94C>A mutation is linked to flu-like symptoms, rash, and pancreatitis during azathioprine (AZA) therapy and to early AZA discontinuation. In this study, we investigated whether the enzyme phenotype is also related to adverse effects (AEs). Patients suffering from inflammatory bowel disease who were treated with AZA (N=160; age 43±12 years) were included. Data were categorized into quartiles according to the ITPA activity. Information about the therapeutic regimen, AEs [leucopenia, increased hepatic enzymes (alanine aminotransferase, aspartate aminotransferase, gamma-glutamyl transferase), flu-like symptoms, and pancreatitis], cotherapy, and comorbidity was obtained from the responsible clinicians and patients by using a standardized questionnaire. ITPA activity was measured by a validated high-performance liquid chromatography procedure. In patients with decreased ITPA activity, the 94C>A and IVS2+21A>C genotypes were determined. AEs were reported significantly more often for patients with low ITPA activity than for patients with high ITPA activity; the highest odds ratio for occurrence of AEs was found to be below a threshold of 59.9 μmol/(gHb·h) [hemoglobin (Hb)]. Decreased ITPA activities [particularly <89.2 μmol/(gHb·h)] were frequently accompanied by leucopenias, whereas very low enzyme activities [<37.3 μmol/(gHb·h)] were associated with a higher incidence of increased liver enzymes. The results demonstrate a relationship between low ITPA activity and AEs and support the idea that the determination of ITPA phenotype might be an appropriate alternative to genotyping.

Association of the 5-aminoimidazole-4-carboxamide ribonucleotide transformylase gene with response to methotrexate in juvenile idiopathic arthritis

ObjectivesMethotrexate (MTX) is the mainstay treatment for juvenile idiopathic arthritis (JIA), however approximately 30% of children will fail to respond to the drug. Identification of genetic predictors of response to...

Common genetic polymorphism of ITPA gene affects ribavirin‐induced anemia and effect of peg‐interferon plus ribavirin therapy

An association between a single nucleotide polymorphism (SNP) in the inosine triphosphate pyrophosphatase (ITPA) gene and reduction of hemoglobin during peg-interferon plus ribavirin combination therapy for patients with chronic hepatitis C virus (HCV) infection has been reported. However, the effect of the SNP on outcome of therapy has not been fully elucidated. Factors associated with anemia during combination therapy, including rs1127354 genotype, were analyzed in 1,002 treated patients. The effect of the SNP on outcome of therapy was analyzed in a subset of 830 patients with genotype 1. A rapid initial decrease in hemoglobin levels was observed in patients with rs1127354 genotype CC compared with a slow decrease in non-CC patients. Cumulative reduction of ribavirin was significantly more frequent in genotype CC patients than non-CC patients (odds ratio 1.928, P = 8.6 × 10(-8) ). The frequency of patients who received at least the recommended 80% of scheduled ribavirin was significantly lower among genotype CC patients, especially among those who had pretreatment hemoglobin levels between 13.5 and 15 g/dl (P < 0.03), and the sustained viral response rate was significantly lower in this group of patients. Independent predictive factors for sustained virological response included a SNP in the IL28B locus (rs809991), age, fibrosis, ITPA SNP rs1127354 as well as pretreatment hemoglobin levels. Our data suggests that measures to prevent anemia should be considered for patients who have pretreatment hemoglobin levels less than 13.5 g/dl or who have rs1127354 genotype CC and pretreatment hemoglobin levels between 13.5 and 15 g/dl.

ITPA Polymorphism Affects Ribavirin-Induced Anemia and Outcomes of Therapy—A Genome-Wide Study of Japanese HCV Virus Patients

Ribavirin-induced anemia is one of the major causes of discontinuation and dose reduction during anti-hepatitis C virus therapy. Factors influencing this anemia, especially host genetic factors, are poorly understood. In this study we investigated predictive factors in hepatitis C virus patients treated with combination therapy. We performed a 2-step genome-wide screening followed by replication analysis and fine-mapping using a total of 923 Japanese hepatitis C virus 1b-infected patients treated with pegylated-interferon plus ribavirin. We also applied logistic regression analysis to search for possible independent associations of clinical parameters and genetic variants with treatment-induced hemoglobin (Hb) decline as well as treatment outcomes. We identified a variant, located upstream of the inosine triphosphate pyrophosphatase gene on chromosome 20p13 that is significantly associated with treatment-induced anemia (combined P = 6.0 × 10(-14)). Resequencing and fine-mapping revealed several single nucleotide polymorphisms (SNPs) strongly associated with Hb decline, including the nonsynonymous SNP rs1127354 (P = 3.5 × 10(-44)), which was recently reported for other ethnic groups. Another reported SNP, the splicing variant-related SNP rs7270101, was not polymorphic in the Japanese population. Stratified analysis based on rs1127354 genotype revealed that inosine triphosphate pyrophosphatase expression is not correlated with Hb decline, suggesting that rs1127354 is a direct causal variant in the Japanese population. Multivariate analysis demonstrated that age, baseline Hb, baseline platelet count, and rs1127354 were independently associated with severe anemia (Hb <10 g/dL). A missense substitution in inosine triphosphate pyrophosphatase gene affects ribavirin-induced anemia in hepatitis C virus-infected Japanese patients.

Gene–gene interactions in folate and adenosine biosynthesis pathways affect methotrexate efficacy and tolerability in rheumatoid arthritis

As no single nucleotide polymorphism has emerged as pivotal to predict the lack of efficacy and dose-limiting toxicities to methotrexate (MTX), we evaluated the contribution of gene-gene interactions to the effects of this prodrug in rheumatoid arthritis. A total of 255 patients treated with MTX for at least 3 months were evaluated with efficacy assessed using the European League Against Rheumatism response criteria or a physician's assessment of patient's response to MTX visual analog scale. Gastrointestinal and neurological idiosyncrasies were recorded in 158 patients. Fourteen single nucleotide polymorphisms in folate and adenosine biosynthesis pathways were measured and detection of gene-gene interactions was performed using multifactor-dimensionality reduction, a method that reduces high-dimensional genetic data into a single dimension of predisposing or risk-genotype combinations. Efficacy to MTX (53% responders) was associated with high-order epistasis among variants in inosine-triphosphate pyrophosphatase, aminoimidazole-carboxamide ribonucleotide transformylase, and reduced folate carrier genes. In the absence of predisposing genotype combinations, a 3.8-fold lower likelihood of efficacy was observed (vs. in their presence, 95% confidence interval: 2.2-6.4; P<0.001). Increasing MTX polyglutamate concentrations tended to partially overcome this selective disadvantage. Idiosyncrasies occurred in 29% of patients. In the presence of risk-genotype combinations among variants in methylene tetrahydrofolate reductase, γ-glutamyl-hydrolase, thymidylate synthase, serine hydroxymethyltransferase, and inosine-triphosphate pyrophosphatase genes, an 8.9-fold higher likelihood to exhibit toxicities was observed (vs. in their absence, 95% confidence interval: 3.6-21.9; P<0.001). False-positive report probabilities were below 0.2, thereby indicating that true signals were likely detected in this cohort. These data indicate that gene-gene interactions impact MTX efficacy and tolerability in rheumatoid arthritis.