Genotype-directed, dose-finding study of irinotecan in cancer patients with UGT1A1*28 and/or UGT1A1*6 polymorphisms

Irinotecan-induced severe neutropenia is associated with homozygosity for the UGT1A1*28 or UGT1A1*6 alleles. In this study, we determined the maximum-tolerated dose (MTD) of irinotecan in patients with UGT1A1 polymorphisms. Patients who had received chemotherapy other than irinotecan for metastatic gastrointestinal cancer were enrolled. Patients were divided into three groups according to UGT1A1 genotypes: wild-type (*1/*1); heterozygous (*28/*1, *6/*1); or homozygous (*28/*28, *6/*6, *28/*6). Irinotecan was given every 2 weeks for two cycles. The wild-type group received a fixed dose of irinotecan (150 mg/m(2)) to serve as a reference. The MTD was guided from 75 to 150 mg/m(2) by the continual reassessment method in the heterozygous and homozygous groups. Dose-limiting toxicity (DLT) and pharmacokinetics were evaluated during cycle 1. Of 82 patients enrolled, DLT was assessable in 79 patients (wild-type, 40; heterozygous, 20; and homozygous, 19). Dose-limiting toxicity occurred in one patient in the wild-type group, none in the heterozygous group, and six patients (grade 4 neutropenia) in the homozygous group. In the homozygous group, the MTD was 150 mg/m(2) and the probability of DLT was 37.4%. The second cycle was delayed because of neutropenia in 56.3% of the patients given the MTD. The AUC(0-24 h) of SN-38 was significantly greater (P < 0.001) and more widely distributed in the homozygous group. Patients homozygous for the UGT1A1*28 or UGT1A1*6 allele can receive irinotecan in a starting dose of 150 mg/m(2), but many required dose reductions or delayed treatment in subsequent cycles. UMIN Clinical Trial Registration number: UMIN000000618.     

Correlative analysis of plasma SN-38 levels and DPD activity with outcomes of FOLFIRI regimen for metastatic colorectal cancer with UGT1A1 *28 and *6 wild type and its implication for individualized chemotherapy

It remains uncertain whether there is an correlation between clinical pharmacokinetic parameters and outcomes for metastatic colorectal cancer especially with UGT1A1 *28 and *6 wild type (*1/*1-*1/*1) for serious events associated with Irinotecan are largely excluded. This study retrospectively analyzed the relationship between Irinotecan metabolite levels and outcomes of UGT1A1 *1/*1-*1/*1 genotype arrangement. Blood samples (n = 244) were collected for analysis of plasma DPD activity (before first chemotherapy) and SN-38 levels (1.5 and 49 hour after CPT-11 administration). Clinical variables such as toxicity and outcomes were then assessed. Of the *1/*1 -*1/*1 genotype combination, the median progression free survival of the C_{SN-38 1.5 h} > 50.24 ng/ml subset was remarkably longer than that of the C_{SN-38 1.5 h} ≤ 50.24 ng/ml subset. However, there were no differences between the C_{SN-38 49 h} > 15.25 ng/ml subgroup and the ≤ 15.25 ng/ml group. It was lower DPD activity that responsible for the relatively higher incidence of bone marrow hypocellular, diarrhea, and oral mucositis in the C_{SN-38 1.5 h} > 50.24 ng/ml and C_{SN-38 49 h} > 15.25 ng/ml subsets. Therefore, plasma SN-38 levels is related to outcomes for UGT1A1 *1/*1-*1/*1 genotype, to improve efficacy, patients with C_{SN-38 1.5 h} lower than 50.24 ng/ml, CPT-11 dosage could be added in next chemmotherapy on SN-38 plasma level monitoring. Additionally, in patients with DPD activity below 3.18 before treatment, appropriate reduction of 5-FU dose could be considered to minimize the incidence of adverse events.     

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.     

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.     

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*1/*28 and *1/*6 genotypes have no effects on the efficacy and toxicity of FOLFIRI in Japanese patients with advanced colorectal cancer

Purpose

Differences in efficacy and toxicity between UDP-glucuronosyltransferase (UGT) 1A1*1/*1 and *1/*6 or *1/*28 genotypes remain unclear in Japanese patients.

Methods

Patients with advanced colorectal cancer who received irinotecan combined with 5-fluorouracil plus l-leucovorin (FOLFIRI) as first-line therapy were divided into two groups: those with UGT1A1*1/*1 genotype and those with UGT1A1*1/*6 or *1/*28 genotype. Efficacy and toxicity were compared between these groups retrospectively.

Results

Forty-two patients (24 *1/*1 and 18 *1/*6 or *1/*28) were evaluated. The response rate was 48% in *1/*1 group and 56% in *1/*6 or *1/*28 group (P?=?0.847). Median progression-free survival was 8.6?months in *1/*1 group and 8.5?months in *1/*6 or *1/*28 group (P?=?0.888). No hematologic or non-hematologic toxic effects were clearly related to UGT1A1*1/*6 or *1/*28 during the first cycle or throughout the entire course of chemotherapy.

Conclusions

There were no significant differences in the efficacy or toxicity of FOLFIRI between patients with UGT1A1*1/*1 genotype and those with UGT1A1*1/*6 or *1/*28 genotype. Our results suggest that patients with the latter genotypes can receive FOLFIRI at the same dose of irinotecan as those with the UGT1A1*1/*1 genotype receive.     

伊立替康联合顺铂或5-FU治疗UGT1A1*28野生型TA6/6患者不良反应的比较

目的：比较尿苷二磷酸葡萄糖醛酸转移酶1A1（UGT1A1）*28启动子为野生型的TA6/6患者在使用伊立替康（irinotecan,CPT-11）联合顺铂与CPT-11联合5-FU/亚叶酸钙治疗时不良反应方面的差异。方法根据采取的治疗方案将98例UGT1A1*28野生型TA6/6患者分为CPT-11联合顺铂组（IP组,n＝47）和CPT-11联合5-FU/亚叶酸钙组（FOLFIRI组,n＝51）,对患者进行UGT1A1*28启动子多态性检测,比较不良反应差异。结果在总体3～4级不良反应方面,IP组的发生率（61.7%）明显高于FOLFIRI组（39.2%）,且组间差异具有统计学意义（P=0.026）。在血液学不良反应方面,IP组3～4级白细胞减少、中性粒细胞减少、血小板减少和血红蛋白减少发生率分别为34.0%、51.1%、14.9%和8.5%,FOLFIRI组的发生率分别为11.8%、29.4%、2.0%、0,组间差异均有统计学意义（均P＜0.05）;在非血液学方面,FOLFIRI组3～4级迟发性腹泻发生率为9.8%,IP组未发生3～4级腹泻,两组间发生率的差异有统计学意义（P=0.028）。结论 UGT1A1*28野生型TA6/6患者在接受CPT-11联合顺铂和CPT-11联合5-FU/亚叶酸钙两种化疗方案治疗的不良反应谱存在差异;应用CPT-11时,不但要考虑到UGT1A1*28启动子多态性对不良反应的影响,而且还要考虑CPT-11联合不同药物出现不良反应情况。     

UGT1A1*28基因多态性与伊立替康相关毒性及化疗疗效的关系

伊立替康严重的骨髓抑制和迟发性腹泻限制其广泛应用于各种恶性肿瘤的治疗中。伊立替康代谢受到多种基因调控的影响，其中尿苷二磷酸葡苷酸转移酶1A1（uridine diphosphate glucuronosyltransferase 1A1，UGT1A1）更是起到了关键性作用。本文从伊立替康所致毒性反应的机制、UGT1A1*28基因多态性与之关系及化疗疗效3个方面进行综述，为肿瘤个体化治疗提供新视角。     

UGT1A1 polymorphism can predict hematologic toxicity in patients treated with irinotecan.

PURPOSE: Irinotecan (CPT-11) is approved in metastatic colorectal cancer treatment and can cause severe toxicity. The main purpose of our study was to assess the role of different polymorphisms on the occurrence of hematologic toxicities and disease-free survival in high-risk stage III colon cancer patients receiving 5-fluorouracil (5FU) and CPT-11 adjuvant chemotherapy regimen in a prospective randomized trial. EXPERIMENTAL DESIGN: Four hundred patients were randomized in a phase III trial comparing LV5FU2 to LV5FU2 + CPT-11. DNA from 184 patients was extracted and genotyped to detect nucleotide polymorphism: 3435C>T for ABCB1, 6986A>G for CYP3A5, UGT1A1*28 and -3156G>A for UGT1A1. RESULTS: Genotype frequencies were similar in both treatment arms. In the test arm, no significant difference was observed in toxicity or disease-free survival for ABCB1 and CYP3A5 polymorphisms. UGT1A1*28 homozygous patients showed more frequent severe hematologic toxicity (50%) than UGT1A1*1 homozygous patients (16.2%), P = 0.06. Moreover, patients homozygous for the mutant allele of -3156G>A UGT1A1 polymorphism showed more frequent severe hematologic toxicity (50%) than patients homozygous for wild-type allele (12.5%), P = 0.01. This toxicity occurred significantly earlier in homozygous mutant than wild-type homozygous patients (P = 0.043). In a Cox model, the hazard ratio for severe hematologic toxicity is significantly higher for patients with the A/A compared with the G/G genotype [hazard ratio, 8.4; 95% confidence interval, 1.9-37.2; P = 0.005]. CONCLUSIONS: This study supports the clinical utility of identification of UGT1A1 promoter polymorphisms before LV5FU2 + CPT-11 treatment to predict early hematologic toxicity. The -3156G>A polymorphism seems to be a better predictor than the UGT1A1 (TA)(6)TAA>(TA)(7)TAA polymorphism.     

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.     

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。     

UGT1A1基因不同表型与FOLFIRI方案治疗晚期结直肠癌疗效及毒副反应的相关性

目的:回顾性分析UGT1A1基因不同表型与FOLFIRI方案治疗晚期结直肠癌疗效及毒副反应的相关性。方法:收集贵州医科大学附属肿瘤医院腹部肿瘤科2014年1月至2018年12月收治的临床分期为Ⅳ期结直肠癌或根治性手术后复发转移的晚期结直肠癌患者240例的临床病理资料,所有患者初次行FOLFIRI方案化疗前抽血,提取全血中的DNA,采用PCR技术行UGT1A1基因型检测;接受FOLFIRI化疗方案治疗直至疾病进展或者发生不可耐受的毒性反应。分别采用Binary Logistic Regression模型分析UGT1A1基因不同表型与FOLFIRI化疗疗效的相关性,分解模型及广义估计方程多应变量回归分析UGT1A1基因不同表型与FOLFIRI化疗毒副反应的相关性。结果:本组患者共发现3种UGT1A1基因表型,分别为UGT1A1*1/*1(纯合野生型TA6/6型 188/240 78.3%)、UGT1A1*28/*1(杂合突变型TA6/7型 47/240 19.6%)和UGT1A1*28/*28(纯合突变型TA7/7型 5/240 2.1%)。UGT1A1基因型中TA6/7型TA6/6型相比,FOLFIRI化疗无应答风险增加16%,但无统计学差异;本组转移器官＞2个的患者中TA6/7型和TA6/6型相比,血液学及非血液学毒副反应发生的风险均增加了9.377 3倍（P=0.007 9）,其中消化道毒副反应发生风险增加了42.806 6倍（P=0.025 9）;本组行FOLFIRI化疗≥4周期的患者中,TA6/7型比TA6/6型的患者发生血液学毒性的风险增加了22.324 6倍（P=0.003 5）。结论:TA6/6型为我省结直肠癌患者最为常见的UGT1A1基因表型,而TA7/7型罕见;晚期结直肠癌转移器官数超过2个行FOLFIRI化疗的患者中UGT1A1基因TA6/7型较TA6/6型患者血液学及非血液学毒副反应发生的风险均明显增加,其中消化道毒副反应发生的风险更胜。     

UGT1A1*28 and other UGT1A polymorphisms as determinants of irinotecan toxicity

Irinotecan is a drug commonly used for the treatment of cancer patients, both as a single agent or in combination therapy. Neutropenia and diarrhea are the dose-limiting toxicities. Genetic variations of proteins involved in irinotecan metabolism and transport have been considered in the development of irinotecan toxicity. In particular, polymorphisms affecting UDP-glucuronosyltransferase isoform 1A1 (UGT1A1) expression or activity are being investigated. Among these, UGT1A1*28 has been considered as the major predictive pharmacogenetic marker for severe hematological toxicity (neutropenia). However, translation to clinical practice of UGT1A1*28 testing as a predictive marker of adverse effects needs to be further investigated and the available data are not conclusive in defining a precise genotype-based dosage. Further prospective studies are required to reach a personalization of chemotherapy with irinotecan.     

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。     

UGT1A1*28 and Other UGT1A Polymorphisms as Determinants of Irinotecan Toxicity

Abstract

Irinotecan is a drug commonly used for the treatment of cancer patients, both as a single agent or in combination therapy. Neutropenia and diarrhea are the dose-limiting toxicities. Genetic variations of proteins involved in irinotecan metabolism and transport have been considered in the development of irinotecan toxicity. In particular, polymorphisms affecting UDP-glucuronosyltransferase isoform 1A1 (UGT1A1) expression or activity are being investigated. Among these, UGT1A1*28 has been considered as the major predictive pharmacogenetic marker for severe hematological toxicity (neutropenia). However, translation to clinical practice of UGT1A1*28 testing as a predictive marker of adverse effects needs to be further investigated and the available data are not conclusive in defining a precise genotype-based dosage.

Further prospective studies are required to reach a personalization of chemotherapy with irinotecan.     

Integrated pharmacogenetic prediction of irinotecan pharmacokinetics and toxicity in patients with advanced non-small cell lung cancer

To define an integrated pharmacogenetic model for predicting irinotecan pharmacokinetic (PK) and severe toxicity, we evaluated multivariate analysis using 15 polymorphisms within seven genes with putative influence on metabolism and transport of irinotecan. A total of 107 NSCLC patients treated with irinotecan were evaluated for PK and genotyped for the UGT1A1*6, UGT1A1*28, UGT1A9*22, ABCB11236C>T, 2677G>T/A, 3435C>T, ABCC2-24C>T, 1249G>A, 3972C>T, ABCG234G>A, 421C>A, and SLCO1B1 -11187G>A, 388A>G, and 521T>C, and CYP3A5*3 polymorphisms. Multivariate linear and logistic regression analyses including genotypes and clinicopathologic factors were performed. SN-38 AUC was significantly correlated with ANCs (r=-0.3, p=0.009) and grade 4 neutropenia (p=0.01). The UGT1A1*6/*6, UGT1A9*1/*1 or *1/*22, and SLCO1B1 521TC or CC genotypes, and female-gender were predictive for higher AUC(SN-38) in multivariate analysis. Among them, SLCO1B1 521TC or CC and UGT1A1*6/*6 genotypes were independently predictive for grade 4 neutropenia in multivariate analysis (OR=3.8 and 7.4, respectively). Although no significant association was observed between PK parameters and grade 3 diarrhea, UGT1A9*1/*1, ABCC23972CC, and ABCG234GA or AA genotypes were independently predictive for grade 3 diarrhea in multivariate analysis (OR=6.3, 5.6, and 5.1, respectively). Patient selection based on integrated pharmacogenetic model would be helpful for predicting irinotecan-PK and severe toxicities in NSCLC patients.     

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.     

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.     

Impact of UGT1A1 genotype on the efficacy and safety of irinotecan-based chemotherapy in metastatic colorectal cancer

The phase III AXEPT study showed the noninferiority of modified capecitabine plus irinotecan (mXELIRI) with or without bevacizumab relative to fluorouracil, leucovorin, and irinotecan (FOLFIRI) with or without bevacizumab as a second-line treatment for metastatic colorectal cancer. We evaluated the associations between the UGT1A1 genotype linked to adverse events—caused by irinotecan—and the efficacy and safety of mXELIRI and FOLFIRI. The UGT1A1 genotype was prospectively determined and patients were categorized into three groups according to WT (*1/*1), single heterozygous (SH; *28/*1 or *6/*1), and double heterozygous or homozygous (DHH; *28/*28, *6/*6, or *28/*6). Overall survival (OS), progression-free survival, response rate, and safety were assessed. The UGT1A1 genotype was available in all 650 randomized patients (WT, 309 [47.5%]; SH, 291 [44.8%]; DHH, 50 [7.7%]). The median OS was 15.9, 17.7, and 10.6 months in the WT, SH, and DHH groups, respectively, with an adjusted hazard ratio (HR) of 1.53 (95% confidence interval [CI], 1.12-2.09; P = .008) for DHH vs WT or SH. The median OS in the mXELIRI and FOLFIRI arms was 18.1 vs 14.3 months (HR 0.80; 95% CI, 0.62-1.03) in the WT group, 16.3 vs 18.3 months (HR 1.04; 95% CI, 0.79-1.36) in the SH group, and 13.0 vs 9.1 months (HR 0.71; 95% CI, 0.39-1.31) in the DHH group, respectively. Modified capecitabine plus irinotecan with or without bevacizumab could be a standard second-line chemotherapy in terms of efficacy and safety regardless of the UGT1A1 genotype.