Role of UGT1A1*28 and UGT1A1*6 for irinotecan-induced adverse drug reaction

Irinotecan is widely used in the treatment of colorectal, gastric, and lung cancers. However, adverse drug reactions such as severe diarrhea and neutropenia limit the dose of this drug. Irinotecan is metabolized by carboxylesterase to form an active metabolite, 7-ethyl-10-hydroxycamptothecin(SN-38), which in turn is subsequently conjugated by UGT-glucuronosyltransferase 1A1(UGT1A1)to yield an inactive form, SN-38 glucuronide(SN-38 G). The UGT1A1 gene polymorphisms contribute to the individual variation in adverse events among patients administered irinotecan. However, the distribution of polymorphisms shows large interethnic differences. The distribution of UGT1A1*28 greatly differs between Caucasians and Japanese; the frequency of UGT1A1*28 is high in Caucasians, whereas it is low in Asians including Japanese. Recently, it has been demonstrated that genetic variants of UGT1A1*6 in addition to UGT1A1*28 are associated with the occurrence of adverse events in irinotecan chemotherapy in Asians. This review summarizes recent studies to outline the role of UGT1A1*28 and UGT1A1*6 for irinotecan-induced adverse drug reaction in Japanese cancer patients.     

川东北地区人群结直肠癌患者UGT1A1*28基因多态性与伊立替康所致毒副反应的相关性

目的:观察结直肠癌患者UGT1A1*28基因多态性的分布频率,了解UGT1A1*28基因多态性与结直肠癌患者应用伊立替康联合5-氟尿嘧啶化疗毒副反应的相关性。方法:从384例接受伊立替康联合氟尿嘧啶一线化疗的晚期结直肠癌病例中采外周血提取DNA。采用PCR 法扩增目的基因片段,直接测序法分析UGT1A1*28基因多态性。临床观察并评价患者化疗毒副反应分级,统计分析UGT1A1*28基因表型与化疗毒副反应相关性。结果:全部 384例患者 UGT1A1*28基因多态性分布情况:TA6/6野生基因型287例(74.7％),TA6/7杂合基因型73例（19.0％）,TA7/7纯合基因型24例（6.3％）。化疗毒副反应和UGT1A1*28基因多态性进行临床单因素分析显示UGT1A1*28基因纯合型TA7/7、杂合型TA6/7与3-4度白细胞减少、中性粒细胞减少、腹泻、胆红素升高具有明显相关性（P<0.01）,UGT1A1*28基因纯合型TA7/7及杂合型TA6/7患者发生中性粒细胞减少的风险较UGT1A1*28基因野生型TA6/6患者高5.625倍（OR=5.625）。UGT1A1*28基因纯合型TA7/7和UGT1A1*28基因杂合型TA6/7患者发生腹泻的风险较UGT1A1*28基因野生型TA6/6患者高6.778倍（OR=6.778）。结论:UGT1A1*28基因纯合型TA7/7及杂合型TA6/7患者应用伊立替康化疗后发生重度中性粒细胞减少、重度腹泻的风险高于UGT1A1*28基因野生型TA6/6,为临床伊立替康用药选择、剂量调整、毒副反应的提前干预提供理论依据。     

Relevance of different UGT1A1 polymorphisms in irinotecan-induced toxicity: a molecular and clinical study of 75 patients.

PURPOSE: We wanted to assess polymorphisms in the uridine diphosphoglucuronosyl transferase 1A1 (UGT 1A1) gene: the TATA box polymorphism and UGT 1A1 G71R and Y486D mutations in the coding sequence, the main mutations characterizing Gilbert's syndrome, as predictors of severe toxic event occurrence after irinotecan (CPT-11) administration. Therefore, we set up a rapid, sensitive, and reliable technique in routine practice to detect before CPT-11 treatment, the at-risk patients. EXPERIMENTAL DESIGN: Seventy-five patients with advanced colorectal cancer and treated with CPT-11 and 5-fluorouracil, entered the study. We used the Pyrosequencing technology a real-time sequencing method, to detect the UGT 1A1 TATA box polymorphisms and mutations in the coding regions. Patients were also assessed for both biochemical and clinical evaluation and tolerance to treatment. RESULTS: No G71R and Y486D mutations were found in our population. Frequencies for UGT 1A1 TATA box polymorphisms were 41, 47, and 9% for wild-type 6/6, heterozygous 6/7, and Gilbert's syndrome 7/7, respectively. Tolerance to treatment decreased with increased number of TA repeat with 71% of the patients in 7/7 group who experienced grade 3/4 toxicity. CONCLUSIONS: The method we set up is suitable for the detection of UGT 1A1 polymorphism in routine practice before irinotecan treatment. It could help to detect the patients homozygous or heterozygous for Gilbert's syndrome, at-risk of CPT 11-induced toxicity, and thus could help to individualize the dose to optimize efficacy and limit toxicity.     

Pharmacogenetic impact of polymorphisms in the coding region of the UGT1A1 gene on SN-38 glucuronidation in Japanese patients with cancer

Pharmacogenetic testing for UDP-glucuronosyltransferase (UGT) 1A1*28, a promoter variant of the UGT1A1 gene, is now carried out clinically to estimate the risk of irinotecan-associated toxicity. We studied the clinical significance of UGT1A1*6 and UGT1A1*27, two variants in exon 1 of the UGT1A1 gene that are found mainly in Asians. The study group comprised 46 Japanese patients who received various regimens of chemotherapy including irinotecan at doses from 50 to 180 mg/m(2). Pharmacogenetic relationships were explored between the UGT1A1 genotype and the ratio of the area under the plasma concentration-time curve (AUC) of the active metabolite of irinotecan (SN-38) to that of SN-38 glucuronide (SN-38G), used as a surrogate for UGT1A1 activity (AUC(SN-38)/AUC(SN-38G)). No patient was homozygous for UGT1A1*28, and none had UGT1A1*27. Two were heterozygous for UGT1A1*28. Two were homozygous and 15 heterozygous for UGT1A1*6, all of whom were wild type with respect to UGT1A1*28. Two patients were simultaneously heterozygous for UGT1A1*28 and UGT1A1*6, present on different chromosomes. The other 25 patients had none of the variants studied. The two patients simultaneously heterozygous for UGT1A1*28 and UGT1A1*6 and the two patients homozygous for UGT1A1*6 had significantly higher AUC(SN-38)/AUC(SN-38G) ratios than the others (P = 0.0039). Concurrence of UGT1A1*28 and UGT1A1*6, even when heterozygous, altered the disposition of irinotecan remarkably, potentially increasing susceptibility to toxicity. Patients homozygous for UGT1A1*6 should also be carefully monitored. UGT1A1 polymorphisms in the coding region of the UGT1A1 gene should be genotyped in addition to testing for UGT1A1*28 to more accurately predict irinotecan-related toxicity, at least in Asian patients.     

Usefulness of one-point plasma SN-38G/SN-38 concentration ratios as a substitute for UGT1A1 genetic information after irinotecan administration

Background

It was recently reported that genetic polymorphisms of UDP glucuronyltransferase-1 polypeptide A1 (UGT1A1), a glucuronidation enzyme, were associated with irinotecan (CPT-11) metabolism. The active metabolite of CPT-11, 7-ethyl-10-hydroxycamptothecin (SN-38) was glucuronidated (SN-38G) by UGT1A1. Genetic polymorphisms of UGT1A1 were associated with potentially serious adverse events, including neutropenia. Several studies have suggested that the dose of CPT-11 should be decreased in patients homozygous for UGT1A1*6 or UGT1A1*28, or double heterozygotes (*6/*28). However, the reference dose for patients with these genetic polymorphisms is unclear.

Methods

We investigated the relationship between the SN-38G/SN-38 concentration ratio and the dose of CPT-11 in 70 patients with colorectal cancer who received FOLFIRI-based regimens, by measuring the plasma concentrations of CPT-11, SN-38, and SN-38G.

Results

The SN-38G/SN-38 concentration ratio was lower in patients who were homozygous for UGT1A1*6, heterozygous for UGT1A1*6 or UGT1A1*28, or were double heterozygotes compared with patients with wild-type genes. The relative decreases in the SN-38G/SN-38 concentration ratio in patients homozygous for UGT1A1*6 and in double heterozygotes were greater than in patients heterozygous for UGT1A1*6 or UGT1A1*28. Interestingly, decreases in the SN-38G/SN-38 concentration ratio were associated with decreases in the neutrophil count and the final infusion dose of CPT-11.

Conclusion

Our results suggest that the SN-38G/SN-38 concentration ratio is an important factor for guiding dose adjustments, even in patients with wild-type genes. Therefore, the SN-38G/SN-38 concentration ratio, as an index of the patient’s metabolic capacity, is useful for assessing dose adjustments of CPT-11.     

Severe CPT-11 toxicity in patients with Gilbert's syndrome: Two case reports

Background: CPT-11 is hydrolyzed to its active metabolite SN-38, which is mainly eliminated through conjugation by hepatic uridine diphosphate glucuronosyl transferases (UGTs) to the glucuronide (SN-38G) derivative. Preclinical studies showed that UGT*1.1 is the isozyme responsible for SN-38 glucuronidation. Patients with Gilbert's syndrome have deficient UGT*1.1 activity, therefore may have an increased risk for related CPT-11 toxicity.Patients and methods: Two patients with metastatic colon cancer and Gilbert's syndrome were treated with CPT-11 based chemotherapy. CPT-11, SN-38 and SN-38G pharmacokinetics parameters were obtained. Serum bilirubin was analysed by alkaline methanolysis and HPLC.Results: Both patients presented grade 4 neutropenia and/or diarrhea (NCI-CTC) in every treatment cycle. Biliary index (after Gupta et al) values were well above 4000.Conclusion: We present the first clinical evidence linking bilirubin glucuronidation status and CPT-11 related toxicity. The severe toxicity experienced by the two patients with Gilbert's syndrome treated with CPT-11 based chemotherapy has a genetic basis. Individuals with Gilbert's syndrome have an enhanced risk for CPT-11 toxicity. Unconjugated serum bilirubin could be predictive parameter of CPT-11 toxicity.     

Polymorphisms of UDP-glucuronosyltransferase gene and irinotecan toxicity: a pharmacogenetic analysis

Irinotecan unexpectedly causes severe toxicity of leukopenia or diarrhea. Irinotecan is metabolized to form active SN-38, which is further conjugated and detoxified by UDP-glucuronosyltransferase (UGT) 1A1 enzyme. Genetic polymorphisms of the UGT1A1 would affect an interindividual variation of the toxicity by irinotecan via the alternation of bioavailability of SN-38. In this case-control study, retrospective review of clinical records and determination of UGT1A1 polymorphisms were performed to investigate whether a patient with the variant UGT1A1 genotypes would be at higher risk for severe toxicity by irinotecan. All patients previously received irinotecan against cancer in university hospitals, cancer centers, or large urban hospitals in Japan. We identified 26 patients who experienced severe toxicity and 92 patients who did not. The relationship was studied between the multiple variant genotypes (UGT1A1*28 in the promoter and UGT1A1*6, UGT1A1*27, UGT1A1*29, and UGT1A1*7 in the coding region) and the severe toxicity of grade 4 leukopenia (< or =0.9 x 10(9)/liter) and/or grade 3 (watery for 5 days or more) or grade 4 (hemorrhagic or dehydration) diarrhea. Of the 26 patients with the severe toxicity, the genotypes of UGT1A1*28 were homozygous in 4 (15%) and heterozygous in 8 (31%), whereas 3 (3%) homozygous and 10 (11%) heterozygous were found among the 92 patients without the severe toxicity. Multivariate analysis suggested that the genotype either heterozygous or homozygous for UGT1A1*28 would be a significant risk factor for severe toxicity by irinotecan (P < 0.001; odds ratio, 7.23; 95% confidence interval, 2.52-22.3). All 3 patients heterozygous for UGT1A1*27 encountered severe toxicity. No statistical association of UGT1A1*6 with the occurrence of severe toxicity was observed. None had UGT1A1*29 or UGT1A1*7. We suggest that determination of the UGT1A1 genotypes might be clinically useful for predicting severe toxicity by irinotecan in cancer patients. This research warrants a prospective trial to corroborate the usefulness of gene diagnosis of UGT1A1 polymorphisms prior tb irinotecan chemotherapy.     

UGT1A1基因多态性与伊立替康临床用药安全性及疗效的关系

目的：研究 UGT1A1基因多态性与伊立替康治疗结直肠癌患者的不良反应及疗效之间的关系。方法：自外周血中抽提基因组 DNA,进行 PCR 扩增,应用直接测序法分析2012年3月至2013年3月,于我院行基因检测的65例结直肠癌患者 UGT1A1*28和 UGT1A1*6基因多态性的分布情况。并对这65例应用含伊立替康方案化疗的患者出现的不良反应及化疗疗效,进行观察记录,比较不同基因型间的差异。结果：65例患者中,UGT1A1*28野生型 TA6／6有49例（75．4％）,杂合突变型 TA6／7有14例（21．5％）,纯合突变型TA7／7有2例（3．1％）。UGT1A1*6野生型 G／G 有47例（72．3％）,杂合突变型 G／A 有15例（23．1％）,纯合突变型 A ／A 有3例（4．6％）。在以上65例结直肠癌患者中,UGT1A1基因启动子区28位点,TA6／6、TA6／7和TA7／7型,发生3级以上腹泻者分别为8．2％、37．5％;发生3级以上中性粒细胞减少者分别为28．6％、62．5％。UGT1A1基因启动子区6位点,G／G、G／A 和 A ／A 型,发生3级以上腹泻者分别为12．8％、44．4％;发生3级以上中性粒细胞减少者分别为14．9％、22．2％。各组之间疗效无统计学差异。结论：患者 UGT1A1*28和UGT1A1*6多态性分布基本一致,UGT1A1*28突变型可以使应用含伊立替康化疗患者发生3级以上腹泻和中性粒细胞减少的风险增加。UGT1A1*6突变型可增加3级以上腹泻的发生风险。因此,UGT1A1基因型的检测对伊立替康相关的不良反应有一定的预测作用,可提高用药安全性,在临床用药中起到了指导作用。     

Genetic Polymorphisms of the UDP-Glucuronosyltransferase 1A7 Gene and Irinotecan Toxicity in Japanese Cancer Patients

Irinotecan often causes unpredictably severe, occasionally fatal, toxicity involving leukopenia or diarrhea. It is converted by carboxyesterase to an active metabolite, SN–38, which is further conjugated and detoxified to SN–38–glucuronide by UDP-glucuronosyltransferase (UGT). We genotyped the UGT1A7 gene by direct sequencing analysis and polymerase chain reaction-restriction fragment length polymorphism in 118 cancer patients and 108 healthy subjects. All the patients had received irinotecan-containing chemotherapy and were evaluated to see whether the variant UGT1A7 genotype would increase the likelihood of severe toxicity of irinotecan consisting of grade 4 leukopenia and/or grade 3 or more diarrhea. Among the 26 patients with severe toxicity, the allele frequencies were 61.5% for UGT1A7*1 , 15.4% for UGT1A7*2 , and 23.1% for UGT1A7*3. On the other hand, the frequencies were 63.6% for UGT1A7*1 , 15.8% for UGT1A7*2 , and 20.7% for UGT1A7*3 among the 92 patients without severe toxicity. None of the 118 patients had UGT1A7*4. Neither univariate analysis (odds ratio, 1.13; 95% confidential interval, 0.46–2.75) nor multivariate logistic regression analysis (odds ratio, 0.74; 95% confidential interval, 0.26–2.07) found any significant association between carrying at least one of the variant alleles and the occurrence of severe toxicity. The distribution of UGT1A7 genotypes in 108 healthy subjects was not significantly different from that in the patients ( P =0.99 and 0.86 for those with and without severe toxicity, respectively), but significantly less than that in Caucasians reported previously ( P <0.001). The results suggested that determination of UGT1A7 genotypes would not be useful for predicting severe toxicity of irinotecan.     

Clinical Observations on Associations Between the UGT1A1 Genotype and Severe Toxicity of Irinotecan

Background: Severe toxicity is commonly observed in cancer patients receiving irinotecan (CPT-11)UDPglucuronosyltransferase1A1 (UGT1A1) catalyzes the glucuronidation of the active metabolite SN-38 but therelationship between UGT1A1 and severe toxicity remains unclear. Our study aimed to assess this point to guideclinical use of CPT-11. Materials and Methods: 89 cancer patients with advanced disease received CPT-11-basedchemotherapy for at least two cycles. Toxicity, including GI and hematologic toxicity was recorded in detail andUGT1A1 variants were genotyped. Regression analysis was used to analyse relationships between these variablesand tumor response. Results: The prevalence of grade III-IV diarrhea was 10.1%, this being more common inpatients with the TA 6/7 genotype (5 of 22 patients, 22.7%) (p<0.05). The prevalence of grade III-IV neutropeniawas 13.4%and also highest in patients with the TA 6/7 genotype (4 of 22 patients; 18.2%) but without significance(p>0.05). The retreatment total bilirubin levels were significantly higher in TA6/7 patients (mean, 12.75μmol/L)with compared to TA6/6 (mean, 9.92 μmol/L) with p<0.05. Conclusions: Our study support the conclusion thatpatients with a UGT1A1*28 allele (s) will suffer an increased risk of severe irinotecan-induced diarrhea, whetherwith mid-or low-dosage. However, the UGT1A1*28 allele (s) did not increase severe neutropenia. Higher serumtotal bilirubin is an indication that patients UGT1A1 genotype is not wild-type, with significance for clinic usageof CPT-11.     

The value of genetic polymorphisms to predict toxicity in metastatic colorectal patients with irinotecan-based regimens

Purpose

We are trying to identify predictive factors of high risk of toxicity by analyzing candidate genes in the irinotecan pathways in order to identify useful tools to improve mCRC patient management under real practice conditions.

Methods

Genomic DNA was genotyped for UGT1A1 (*28, *60 and *93) from all 101 patients, and irinotecan dose was 180 mg/m² every second week. Clinical data were obtained by retrospective chart review. The primary endpoint is to find out whether the pharmacogenetic test in the clinical practice may predict toxicity.

Results

Grade 3/4 diarrhea occurred in twelve patients and required dose reduction in six patients, and neutropenia reached grade 3/4 in 19 patients (only one patient with *28/*28 genotype). The UGT1A1*93 seemed to relate with grade 3/4 neutropenia but only in the heterozygote state (G/A), p = 0.071, and UGT1A*60 showed no association with neutropenia. Twenty-eight percentage of patients required the use of G-CSF; 64.3 % of them harbored *1/*28 or *28/*28 genotypes, p = 0.003. Thirty-seven (36.6 %) patients required dose reduction of irinotecan and/or 5-FU owing to toxicity, mainly neutropenia and diarrhea. No significant association was detected between *28, *60 and *93 UGT1A variants and severe irinotecan-associated hematologic or GI toxicity.

Conclusion

The impact of increased risk of toxicity attributed to the UGT1A variants may be offset by irinotecan in clinical practice by dose reduction or the use of colony-stimulating factor.     

UGT1A1*28 genotype and irinotecan-induced neutropenia: dose matters

The Food and Drug Administration and Pfizer changed the package insert for irinotecan to include a patient's UGT1A1*28 genotype as a risk factor for severe neutropenia on the basis of the findings of four pharmacogenetic studies, which found that irinotecan-treated patients who were homozygous for the UGT1A1*28 allele had a greater risk of hematologic toxic effects than patients who had one or two copies of the wild-type allele (UGT1A1*1). Findings of subsequent irinotecan pharmacogenetic studies have been inconsistent. In a meta-analysis, we reviewed data presented in nine studies that included a total of 10 sets of patients (for a total of 821 patients) and assessed the association of irinotecan dose with the risk of irinotecan-related hematologic toxicities (grade III-IV) for patients with a UGT1A1*28/*28 genotype. The risk of toxicity was higher among patients with a UGT1A1*28/*28 genotype than among those with a UGT1A1*1/*1 or UGT1A1*1/*28 genotype at both medium (odds ratio [OR] = 3.22, 95% confidence interval [CI] = 1.52 to 6.81; P = .008) and high (OR = 27.8, 95% CI = 4.0 to 195; P = .005) doses of irinotecan. However, risk was similar at lower doses (OR = 1.80, 95% CI = 0.37 to 8.84; P = .41). Low doses of irinotecan (100-125 mg/m2) are in the commonly used therapeutic range. The risk of experiencing irinotecan-induced hematologic toxicity for patients with a UGT1A1*28/*28 genotype thus appears to be a function of the dose of irinotecan administered.     

Author Index

Abstract

Irinotecan is a promising anticancer agent for the treatment of childhood cancer un-responsive to conventional chemotherapy. Its active metabolite, 7-ethyl-10 hydroxy-camptothecin (SN-38) is glucuronidated by a uridine-diphosphoglucuronosyl-transferase (UGT1A1) to form an inactive metabolite. It was supposed that patientswith the UGT1A1*28 polymorphism would have a greater prevalence of elevated pre-treatment serum bilirubin levels and higher toxicity. The aim of our study was to investigate the predictive value of pre-treatment bilirubin levels in the development of severe diarrhea in solid tumor patients treated with irinotecan. The survey included14 pediatric patients with refractory sarcomas treated with irinotecan (CPT-11). Patients were grouped based on the development of mild (G0-2) or severe (G3) gastrointestinal toxicity. The simple linear regression model and the non-parametric paired wilcoxon test were adopted for the analysis. P <0.05 was judged to indicate a significant difference. The results showed a significant increase in severity of diarrhea with in creasing total pre-treatment bilirubin. Therefore, we propose that pre-treatmentbilirubin levels can predict gastrointestinal toxicity in pediatric cancer.     

Linkage disequilibrium of UGT1A1 *6 and UGT1A1 *28 in relation to UGT1A6 and UGT1A7 polymorphisms

UDP-glucuronosyltransferase (UGT) enzymes are responsible for the glucuronidation and detoxification of many endogenous or exogenous xenobiotics. Gilbert's syndrome (GS) and Crigler Najjar syndrome type 2 (CNS-II) are characterized by unconjugated hyperbilirubinemia due to reduced enzymatic activity of UGT1A1. Recent studies have demonstrated the frequent co-existence of UGT1A1 *28 (-53 [TA]6>7) with other polymorphisms of UGT1A6 and UGT1A7. This finding suggests the occurrence of linkage disequilibrium (LD) among UGT1A1, UGT1A6 and UGT1A7 polymorphisms. UGT1A1 *6 (211G>A, G71R) and UGT1A1 *28 are common in Asian populations. In the present study, we investigated the LD of UGT1A1 *6 and UGT1A1 *28 in relation to UGT1A6 and UGT1A7 polymorphisms. Exon 1 of UGT1A1, UGT1A6 and UGT1A7 was sequenced using genomic DNA isolated from peripheral leukocytes of 390 Japanese subjects. LD and haplotypes were analyzed using SNPAlyze ver. 5.0 software. UGT1A1 *6 had a strong LD in relation to UGT1A6 variants including 541A>G and 552A>C (D'=0.846-0.848, r(2)=0.413-0.438) and UGT1A7 variants including 387T>G, 391C>A, 392G>A and 622T>C (D'=0.667-0.858, r(2)=0.207-0.413). UGT1A1 *28 had a lower degree of LD than UGT1A1 *6 in relation to these variants (D'=0.245-0.401, r(2)=0.025-0.063). All the haplotypes with G71R lacked -53[TA]6>7. The present study showed for the first time that the LD of UGT1A1 *6 in relation to UGT1A6 and 1A7 polymorphisms is far stronger than UGT1A1 *28. The UGT1A1 *6 allele appears to be independent of the UGT1A1 *28 allele. Although patients with GS and CNS-II are believed to have good prognosis, a subgroup of GS or CNS-II patients with the UGT1A1 *6 polymorphism might be at risk of abnormal drug metabolism and of developing malignant disease.     

UGT1A1基因多态性与伊立替康治疗结直肠癌不良反应的关系

背景与目的：尿苷二磷酸葡萄糖醛酸转移酶1A1(uridine diphosphoglucu-ronosyltransferase 1A1,UGTlA1)是伊立替康代谢关键酶,其活性受基因多态性影响显著。本研究探讨结直肠癌患者中,UGT1A1*28和UGT1A1*6基因多态性与伊立替康治疗相关不良反应之间的关系。方法：入组2013年4月—2013年12月于复旦大学附属中山医院肿瘤内科接受治疗的消化道恶性肿瘤患者160例。抽提外周血中基因组DNA,分别采用STR方法和Sanger测序法,检测UGT1A1*28和UGT1A1*6基因型,分析UGT1A1基因多态性分布情况。对其中82例化疗方案中含伊立替康的结直肠癌患者进行随访,记录不良反应发生情况和严重程度,比较不同基因型患者之间的差异。结果：160例消化道肿瘤患者中,UTG1A1*28(启动子TATA盒区域TA重复次数)野生型TA6/6124例(77.5%);杂合子TA6/7 33例(20.5%);纯合子TA7/7 3例(2.0%)。UGT1A1*6位点(211G>A)野生型GG 105例(65.6%),杂合子GA 48例(30.0%);纯合子AA 7例(4.4%)。82例化疗方案中含伊立替康的结直肠癌患者中,*28基因型(TA6/7和TA7/7)显著增加发生3级以上中性粒细胞减少的风险(58.3% vs 0.0%,P<0.001),并增加整体不良反应发生率(76.0% vs 45.6%,P<0.001);*6基因型(GA和AA)、年龄、性别、化疗方案和伊立替康相关不良反应发生无显著相关性。结论：接受伊立替康化疗的结直肠癌患者,UGT1A1*28位点多态性显著增加中性粒细胞减少发生的风险,可预测伊立替康引起的骨髓抑制性不良反应,辅助临床选择合适的化疗方案。     

Effect of milk thistle (Silybum marianum) on the pharmacokinetics of irinotecan.

PURPOSE: Milk thistle (Silybum marianum) is one of the most commonly used herbal therapies, and its principal constituent silybin significantly inhibits cytochrome P450 isoform 3A4 (CYP3A4) and UDP glucuronosyltransferase isoform 1A1 (UGT1A1) in vitro. Here, we investigated whether milk thistle affects the pharmacokinetics of irinotecan, a substrate for CYP3A4 and UGT1A1, in humans. EXPERIMENTAL DESIGN: Six cancer patients were treated with irinotecan (dose, 125 mg/m(2)) given as a 90-minute infusion once every week. Four days before the second dose, patients received 200 mg milk thistle, thrice a day, for 14 consecutive days. Pharmacokinetic studies of irinotecan and its metabolites 7-ethyl-10-hydroxycamptothecin (SN-38), 7-ethyl-10-[3,4,5-trihydroxy-pyran-2-carboxylic acid]-camptothecin (SN-38-glucuronide), and 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]-carbonyloxycamptothecin were done during the first three irinotecan administrations. RESULTS: Short-term (4 days) or more prolonged intake of milk thistle (12 days) had no significant effect on irinotecan clearance (mean, 31.2 versus 25.4 versus 25.6 L/h; P = 0.16). The area under the curve ratio of SN-38 and irinotecan was slightly decreased by milk thistle (2.58% versus 2.23% versus 2.17%; P = 0.047), whereas the relative extent of glucuronidation of SN-38 was similar (10.8 versus 13.5 versus 13.1; P = 0.64). Likewise, the area under the curve ratio of 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]-carbonyloxycamptothecin and irinotecan was unaffected by milk thistle (0.332 versus 0.285 versus 0.337; P = 0.53). The maximum plasma concentrations of silybin ranged between 0.0249 and 0.257 micromol/L. CONCLUSIONS: Silybin concentrations after intake of milk thistle are too low to significantly affect the function of CYP3A4 and UGT1A1 in vivo, indicating that milk thistle is unlikely to alter the disposition of anticancer drugs metabolized by these enzymes.     

UGT1A7 and UGT1A9 polymorphisms predict response and toxicity in colorectal cancer patients treated with capecitabine/irinotecan.

PURPOSE: Capecitabine and irinotecan are commonly used in the treatment of metastatic colorectal cancer (CRC). We hypothesized that germline polymorphisms within genes related to drug target (thymidylate synthase) or metabolizing enzymes (UDP-glucuronosyltransferase, UGT) would impact response and toxicity to the combination of capecitabine plus irinotecan (CPT-11). EXPERIMENTAL DESIGN: Sixty-seven patients with measurable CRC were treated with irinotecan i.v. (100 or 125 mg/m(2)) on days 1 and 8 and capecitabine orally (900 or 1,000 mg/m(2), twice daily) on days 2 through 15 of each 3-week cycle. Genomic DNA was extracted from peripheral blood and genotyped using Pyrosequencing, GeneScan, and direct sequencing (Big Dye terminator) technologies. RESULTS: The overall objective response rate was 45% with 21 patients (31%) exhibiting grade 3 or 4 diarrhea and 3 patients (4.5%) demonstrating grade 3 or 4 neutropenia in the first two cycles. Low enzyme activity UGT1A7 genotypes, UGT1A7*2/*2 (six patients) and UGT1A7*3/*3 (seven patients), were significantly associated with antitumor response (p = 0.013) and lack of severe gastrointestinal toxicity (p = 0.003). In addition, the UGT1A9 -118 (dT)(9/9) genotype was significantly associated with reduced toxicity (p = 0.002) and increased response (p = 0.047). There were no statistically significant associations between UGT1A1, UGT1A6, or thymidylate synthase genotypes and toxicity or tumor response. CONCLUSIONS: These data strongly suggest that UGT1A7 and/or UGT1A9 genotypes may be predictors of response and toxicity in CRC patients treated with capecitabine plus irinotecan. Specifically, patients with genotypes conferring low UGT1A7 activity and/or the UGT1A9 (dT)(9/9) genotype may be particularly likely to exhibit greater antitumor response with little toxicity.     

Associations between UGT1A1*6 or UGT1A1*6/*28 polymorphisms and irinotecan-induced neutropenia in Asian cancer patients

Purpose

Neutropenia is a life-threatening side effect of irinotecan, and uridine diphosphate glucuronosyltransferases (UGTs) gene polymorphisms are considered to be one of the predictive markers of irinotecan-related toxicities. Many studies have demonstrated that patients bearing UGT1A1*28 have a higher risk of severe neutropenia on toxicity of irinotecan. However, UGT1A1 (TA7/TA7) was very rare in Asian populations. Some researches reported that UGT1A1*28 and/or UGT1A1*6 could predict irinotecan-induced toxicities in Asian populations, but controversial conclusions still remained. This study aims to investigate the association between UGT1A1 gene polymorphisms *6, *6/*28 and irinotecan-related neutropenia in Asian cancer patients receiving irinotecan regimen chemotherapy.

Experimental design

Meta-analyses were done to assess the relationship between UGT1A1*6 or UGT1A1*6/*28 and irinotecan-induced neutropenia.

Results

The risk of neutropenia was significantly higher among patients with a UGT1A1*6 genotype than among those carrying the UGT1A1*1 allele(s) [odds ratio (OR) 3.276; 95 % confidence interval (CI) 1.887–5.688; P = 0.000 (*6/*6 vs. *1/*6 or *1/*1)], [OR 1.542; 95 % CI 1.180–2.041; P = 0.001 (*6/*6 or *1/*6 vs. *1/*1)]. Also, the risk was significantly higher among patients with a UGT1A1*6/*28 than among those carrying the UGT1A1*1 allele(s) [OR 3.275; 95 % CI 2.152–4.983; P = 0.000 (*6/*6 or *28/*28 or *6/*28 vs. *1/*6 or *1/*28 or *1/*1)].

Conclusions

In conclusion, the UGT1A1*6 and UGT1A1*6/*28 genotypes were associated with an increased risk of irinotecan-induced neutropenia in Asian cancer patients.     

Clinical and pharmacogenetic factors associated with irinotecan toxicity

Irinotecan is a topo-isomerase-I inhibitor with broad antitumor activity in solid tumors. Its use may lead to severe toxicities, predominantly neutropenia and diarrhea which can be life-threatening. This review discusses clinical determinants and pharmacogenetic factors associated with irinotecan toxicity. Age, performance status, co-medication and elevated transaminases have been associated with increased risk of diarrhea or neutropenia. Also, elevated bilirubin levels, due to liver impairment, conjugation disorders or UGT1A1 *28 genotype, have been associated with increased incidence of grades 3 intestinal toxicity and neutropenia. UGT1A1 *28 homozygosity is strongly associated with irinotecan-induced neutropenia and polymorphisms in the transporting peptides ABCB1 and OATP1B1 have also been associated with gastrointestinal toxicity and irinotecan pharmacokinetics, respectively. In the irinotecan product label, it is advised to reduce the irinotecan starting dose for UGT1A1 *28 homozygotes. However, due to the lack of prospective data, it is yet unknown whether dose reduction leads to reduced toxicity or altered antitumor effect. Combined toxicity analysis reveals that most patients experiencing grade 3-4 diarrhea and/or neutropenia are not homozygous for UGT1A1 *28. Future studies should combine pharmacogenetics with clinical determinants such as performance status and co-medication as to predict irinotecan toxicity and to develop predefined dosing algorithms.     

Genetic variants in the UDP-glucuronosyltransferase 1A1 gene predict the risk of severe neutropenia of irinotecan.

PURPOSE: Severe toxicity is commonly observed in cancer patients receiving irinotecan. UDP-glucuronosyltransferase 1A1 (UGT1A1) catalyzes the glucuronidation of the active metabolite SN-38. This study prospectively evaluated the association between the prevalence of severe toxicity and UGT1A1 genetic variation. PATIENTS AND METHODS: Sixty-six cancer patients with advanced disease refractory to other treatments received irinotecan 350 mg/m(2) every 3 weeks. Toxicity and pharmacokinetic data were measured during cycle 1. UGT1A1 variants (-3279G>T, -3156G>A, promoter TA indel, 211G>A, 686C>A) were genotyped. RESULTS: The prevalence of grade 4 neutropenia was 9.5%. Grade 4 neutropenia was much more common in patients with the TA indel 7/7 genotype (3 of 6 patients; 50%) compared with 6/7 (3 of 24 patients; 12.5%) and 6/6 (0 of 29 patients; 0%) (P =.001). The TA indel genotype was significantly associated with the absolute neutrophil count nadir (7/7 < 6/7 < 6/6, P =.02). The relative risk of grade 4 neutropenia was 9.3 (95% CI, 2.4 to 36.4) for the 7/7 patients versus the rest of the patients. Pretreatment total bilirubin levels (mean +/- standard deviation) were significantly higher in patients with grade 4 neutropenia (0.83 +/- 0.08 mg/dL) compared to those without grade 4 neutropenia (0.47 +/- 0.03 mg/dL; P <.001). The -3156G>A variant seemed to distinguish different phenotypes of total bilirubin within the TA indel genotypes. The -3156 genotype and the SN-38 area under the concentration versus time curve were significant predictors of ln(absolute neutrophil count nadir; r(2) = 0.51). CONCLUSION: UGT1A1 genotype and total bilirubin levels are strongly associated with severe neutropenia, and could be used to identify cancer patients predisposed to the severe toxicity of irinotecan. The hypothesis that the -3156G>A variant is a better predictor of UGT1A1 status than the previously reported TA indel requires further testing.