Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027947 (neutropenia)
 17,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The metabolism of irinotecan (CPT-11) involves sequential activation to SN-38 and detoxification to the pharmacologically inactive SN-38 glucuronide (SN-38G). We have previously demonstrated the role of UGT1A1 enzyme in the glucuronidation of SN-38 and a significant correlation between in vitro glucuronidation of SN-38 and UGT1A1 gene promoter polymorphism. This polymorphism (UGT1A1*28) is characterized by the presence of an additional TA repeat in the TATA sequence of the UGT1A1 promoter, ((TA)7TAA, instead of (TA)6TAA). Here we report the results from a prospective clinical pharmacogenetic study to determine the significance of UGT1A1*28 polymorphism on irinotecan disposition and toxicity in patients with cancer. Twenty patients with solid tumors were treated with a 90 min i.v. infusion of irinotecan (300 mg m(-2)) once every 3 weeks. The frequency of UGT1A1 genotypes was as follows: 6/6--45%, 6/7--35% and 7/7--20%, with allele frequencies of 0.375 and 0.625 for (TA)7TAA and (TA)6TAA, respectively. Patients with the (TA)7TAA polymorphism had significantly lower SN-38 glucuronidation rates than those with the normal allele (6/6>6/7>7/7, P = 0.001). More severe grades of diarrhea and neutropenia were observed only in patients heterozygous (grade 4 diarrhea, n = 1) or homozygous (grade 3 diarrhea/grade 4 neutropenia, n = 1 and grade 3 neutropenia, n = 1) for the (TA)7TAA sequence. The results suggest that screening for UGT1A1*28 polymorphism may identify patients with lower SN-38 glucuronidation rates and greater susceptibility to irinotecan induced gastrointestinal and bone marrow toxicity.
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PMID:UGT1A1*28 polymorphism as a determinant of irinotecan disposition and toxicity. 1199 Mar 81

Etoposide is a substrate for P-glycoprotein, CYP3A4, CYP3A5, and UGT1A1. Glucocorticoids modulate CYP3A and P-glycoprotein in preclinical models, but their effect on clinical etoposide disposition is unknown. We studied the pharmacokinetics of etoposide and its catechol metabolite in children with acute lymphoblastic leukemia, along with polymorphisms in CYP3A4, CYP3A5, MDR1, GSTP1, UGT1A1, and VDR. Plasma pharmacokinetics were assessed at day 29, after 1 month of prednisone (n = 102), and at week 54, without prednisone (n = 44). On day 29, etoposide clearance was higher (47.4 versus 29.2 mL/min/m2, P <.0001) than at week 54. The day 29 etoposide or catechol area under the curve (AUC) was correlated with neutropenia (P =.027 and P =.0008, respectively). The relationship between genotype and etoposide disposition differed by race and by prednisone use. The MDR1 exon 26 CC genotype predicted higher day 29 etoposide clearance (P =.002) for all patients, and the CYP3A5 AA and GSTP1 AA genotypes predicted lower clearance in blacks (P =.02 and.03, respectively). The UGT1A1 6/6, VDR intron 8 GG, and VDR Fok 1 CC genotypes predicted higher week 54 clearance in blacks (P =.039,.036, and.052, respectively). The UGT1A1 6/6 genotype predicted lower catechol AUC. Prednisone strongly induces etoposide clearance, genetic polymorphisms may predict the constitutive and induced clearance of etoposide, and the relationship between genotype and phenotype differs by race.
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PMID:Effects of prednisone and genetic polymorphisms on etoposide disposition in children with acute lymphoblastic leukemia. 1296 65

SN-38 is the active metabolite of irinotecan and it is metabolised through conjugation by uridine diphosphate glucuronosyl transferase (UGT1A1). The major toxicity of irinotecan therapy is diarrhoea, which has been related to the enzymatic activity of UGT1A1. We examined the influence of the UGT1A1 gene promoter polymorphism in the toxicity profile, in the response rate and in the overall survival (OS) in 95 patients with metastatic colorectal cancer treated with an irinotecan-containing chemotherapy. Genotypes were determined by analysing the sequence of TATA box of UGT1A1 of genomic DNA from the patients. Clinical parameters and genotypes were compared by univariate and multivariate statistical methods. The more frequent adverse effects were asthenia (34 patients), diarrhoea (29 patients) and neutropenia (20 patients). Severe diarrhoea was observed in 7/10 homozygous (70%) and 15/45 heterozygous (33%) in comparison to 7/40 (17%) wild-type patients (P=0.005). These results maintained the statistical significance in logistic regression analysis (P=0.01) after adjustment for other clinical relevant variables. The presence of severe haematological toxicity increased from wild-type patients to UGT1A1(*)28 homozygotes, but without achieving statistical significance. No relationship was found between the UGT1A1(*)28 genotypes and infection, nausea or mucositis. In univariate studies, patients with the UGT1A1(*)28 polymorphism showed a trend to a poorer OS (P=0.09). In the multivariate analysis, the genotype was not related to clinical response or to OS. The role of the UGT1A1 genotype as a predictor of toxicity in cancer patients receiving irinotecan demands the performance of a randomized trial to ascertain whether genotype-adjusted dosages of the drug can help to establish safe and effective doses not only for patients with the UGT1A1(*)28 homozygous genotype but also for those with the most common UGT1A1 6/6 or 6/7 genotype.
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PMID:UGT1A1 gene variations and irinotecan treatment in patients with metastatic colorectal cancer. 1528 Sep 27

Irinotecan (CPT-11) is now widely used, especially for colorectal and lung cancers, whereas the drug causes severe adverse drug reactions (ADR), such as leukopenia/neutropenia or diarrhea. Irinotecan undergoes drug metabolism to form an active SN-38, which is further converted to its beta-glucuronide by UDP-glucuronosyltransferase (UGT) 1A1. A variant in the promoter of UGT1A1 gene, UGT1A1*28 allele, has been extensively studied, and pharmacogenetic relationships between the variant and ADR to irinotecan have been reported. A case-control study of Japanese cancer patients demonstrated that the patients having UGT1A1*28 were at significantly increased risk of severe ADR to irinotecan. To date, genetic variations of the UGT1A1 gene is the most important hereditary factor to predict severe ADR to irinotecan. The UGT1A1*28 is the only one variant that has multiple lines of clinical evidence in multiple races, whereas genetic variations of other UGT isoforms, drug-metabolizing enzymes and drug transporters need more confirmations of its clinical significance in multiple patient groups. At present, irinotecan chemotherapy based on a patient's UGT1A1 genetic status is scientifically reasonable.
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PMID:Clinical pharmacogenetics of irinotecan (CPT-11). 1625 34

Irinotecan, an anticancer drug, is associated with severe and potentially fatal diarrhea and neutropenia. The objective of this analysis was to evaluate the role of SN-38 exposure, the active metabolite of irinotecan, UGT1A1 genotypes, and baseline bilirubin on the maximum decrease (nadir) in absolute neutrophil counts following irinotecan. This analysis extended the work of a previous study that examined the effect of UGT1A1 genotypes on the incidence of severe neutropenia in 86 advanced cancer patients following irinotecan treatment. Regression analysis showed that the absolute neutrophil count nadir depended on SN-38 exposure (AUC) and UGT1A1*28 homozygous 7/7 genotype. An increased SN-38 AUC and the 7/7 genotype were significantly associated with a lower absolute neutrophil count nadir (R2 = .49). An alternate model suggested that higher baseline bilirubin and the 7/7 genotype were also significantly associated with a lower absolute neutrophil count nadir, although with a lower coefficient of determination (R2 = .31). Based on these findings and other reports, the irinotecan label was modified to indicate the role of UGT1A1*28 polymorphism in the metabolism of irinotecan and the associated increased risk of severe neutropenia. The label modifications also included recommendations for lower starting doses of irinotecan in patients homozygous for the UGT1A1*28 (7/7) polymorphism.
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PMID:The role of SN-38 exposure, UGT1A1*28 polymorphism, and baseline bilirubin level in predicting severe irinotecan toxicity. 1719 5

UDP glucuronosyltransferase (UGT) 1A1 gene promoter polymorphism can affect the expression level of the UGT 1A1 enzyme. The polymorphism consists of an insertion of a TA nucleotide sequence into a (TA)6TAA sequence in the gene promoter resulting in (TA)7TAA (UGT1A1*28). This results in a reduced UGT 1A1 expression with 70% less glucuronidation capacity for bilirubin and other UGT1A1 substrates. Other polymorphisms include (TA)8TAA (UGT1A1*37) and (TA)5TAA (UGT1A1*36). The longer the TA repeats the lower the enzyme expression level. The anticancer agent irinotecan is metabolized to the active SN-38, which is further glucuronidated and detoxified by UGT 1A1. Decreased glucuronidation leads to SN-38 accumulation with severe neutropenia and diarrhea. We have developed a rapid polymerase chain reaction (PCR)-based detection of all length polymorphisms in the UGT 1A1 gene promoter. It uses PCR and DNA fragment analysis using an ABI Genetic Analyzer. Thirty-two blood samples were analyzed for UGT 1A1 promoter polymorphism. We found 2 (TA)(5)TAA/(TA)(5)TAA, 4 (TA)(5)TAA/(TA)(6)TAA, 2 (TA)(5)TAA/(TA)(7)TAA, 9 (TA)(6)TAA/(TA)(6)TAA, 11 (TA)(6)TAA/(TA)(7)TAA, 2 (TA)(7)TAA/(TA)(7)TAA, and 2 (TA)(7)TAA/(TA)(8)TAA in our sample group. To confirm the results, 6 samples with different repeats were also analyzed by DNA sequencing method. This is a rapid and reliable method for analysis of the promoter length polymorphisms of UGT 1A1 gene.
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PMID:Validation of rapid polymerase chain reaction-based detection of all length polymorphisms in the UGT 1A1 gene promoter. 1747 Nov 58

Irinotecan is widely used in the treatment of metastatic colorectal cancer and extensive small-cell lung cancer. Its use is limited by severe toxicities such as neutropenia and delayed-type diarrhea. Irinotecan is converted to its active metabolite SN-38. SN-38 is further metabolized to SN-38G by various hepatic and extrahepatic UGT1A isozymes, mainly UGT1A1. Impaired glucuronidation activity of the UGT1A1 enzyme has been linked with elevated levels of SN-38, leading to toxicities. UGT1A1*28 involves an extra TA repeat in the UGT1A1 promoter region and is the variant most frequently contributing to interpatient variability in irinotecan pharmacokinetics and toxicities. This information led to the revision of the irinotecan label by the US Food and Drug Administration. Recently, UGT1A1*6 seems to contribute to the risk of toxicity of irinotecan in Asian patients. The pharmacogenetics of irinotecan (irinogenetics) is one of few promising examples of the application of pharmacogenetics to individualized drug therapy. This review summarizes ongoing studies and unanswered questions on irinogenetics.
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PMID:Insights, challenges, and future directions in irinogenetics. 1752 81

The hepatic isoform 1A1 of uridine diphosphate glucuronosyltransferase is responsible for glucuronidation and detoxification of SN-38, the active metabolite of irinotecan. The presence of an additional TA repeat in the TATA sequence of the UGT1A1 promoter leads to a significant decrease in SN-38 glucuronidation. Patients with the UGT1A1 (TA)7 allele are more likely to experience severe neutropenia and diarrhea following irinotecan chemotherapy. We assessed the distribution of the UGT1A1 (TA)n polymorphism in healthy male and female US residents of European and Asian descent. We used a fluorescent polymerase chain reaction-based assay to detect UGT1A1 (TA)n polymorphisms in 138 healthy volunteers (56 Caucasians, 37 Chinese, 37 Filipino and eight Japanese) between the ages of 18 and 65 years. The chi-test was used to assess between-group differences in the distribution of UGT1A1 (TA)n genotypes. The UGT1A1 (TA)6/6 genotype was significantly more common in Asians than in Caucasians (76 vs. 46%), whereas the (TA)6/7 (39 vs. 20%) and (TA)7/7 (13 vs. 5%) genotypes were more common in Caucasians than in Asians. Genotype distributions did not differ significantly between men and women in either group. The UGT1A1 (TA)5/5 genotype was detected in one Caucasian woman. In conclusion, consistent with previous reports, the UGT1A1 (TA)7/7 genotype was significantly more common in Caucasians than in Asians. UGT1A1 (TA)n/n genotype distribution did not vary with sex in individuals of European or Asian descent.
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PMID:Distribution of the UGT1A1*28 polymorphism in Caucasian and Asian populations in the US: a genomic analysis of 138 healthy individuals. 1776 98

Irinotecan is used widely in the treatment of several malignancies, but unpredictable severe toxicities such as myelosuppression and delayed-type diarrhea are sometimes experienced. Polymorphism of the UGT1A1 gene is one of the likely reasons for interindividual differences in irinotecan pharmacokinetics and severe toxicity. Also, polymorphic organic anion-transporting polypeptide 1B1 (OATP1B1, SLCO1B1) is reported to be involved in the hepatocellular uptake of SN-38. A 61-year-old man with lung cancer developed severe toxicities, including grade 3 diarrhea, grade 4 leukopenia, and grade 4 neutropenia, after the first cycle of irinotecan (60 mg/m) plus cisplatin chemotherapy. The irinotecan and SN-38 areas under the concentration-time curve from time zero to infinity in this patient were 43% and 87% higher than the corresponding mean values for 10 other patients with lung cancer treated with irinotecan (60-100 mg/m) normalized for the dose of irinotecan. Analysis of genetic variants in genes encoding the drug-metabolizing enzyme (UGT1A1) and transporter (SLCO1B1) involving irinotecan disposition revealed that this patient was homozygous for the SLCO1B1*15 allele, which may result in severe toxicities attributable to the extensive accumulation of SN-38. Screening of SLCO1B1*15 is suggested to be useful in irinotecan chemotherapy to avoid unpredicted severe toxicity, although the homozygous genotype is rare among the Japanese.
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PMID:Severe toxicities after irinotecan-based chemotherapy in a patient with lung cancer: a homozygote for the SLCO1B1*15 allele. 1789 62

Recent pharmacogenetic studies on irinotecan have revealed the impact of UDP glucuronosyltransferase (UGT) 1A1*28 on severe irinotecan toxicities. Although the clinical role of UGT1A1*6, which is specifically detected in East Asian patients, in irinotecan toxicities is suggested, clear evidence remains limited. To examine the impact of *6, the association of UGT1A1 genotypes with severe irinotecan toxicities was retrospectively investigated in Japanese cancer patients. A significant *6-dependent increase in the incidence of grade 3 or 4 neutropenia was observed in 49 patients on irinotecan monotherapy (p=0.012). This study further clarifies the clinical importance of *6 in irinotecan therapy in East Asians.
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PMID:Importance of UDP-glucuronosyltransferase 1A1*6 for irinotecan toxicities in Japanese cancer patients. 1808 37


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