title: Pharmacogenetics of irinotecan metabolism and transport: an update.
abstract: The anticancer agent irinotecan (CPT-11) is converted to SN-38, which is approximately 100 to 1,000-fold more cytotoxic than the parent drug. The pharmacokinetics of irinotecan are extremely complex and have been the subject of intensive investigation in recent years. Irinotecan is subject to extensive metabolism by various polymorphic enzymes, including CES2 to form SN-38, members of the UGT1A subfamily, and CYP3A4 and CYP3A5, which form several pharmacologically inactive oxidation products. Elimination of irinotecan is also dependent on drug-transporting proteins, notably ABCB1 (P-glycoprotein), ABCC2 (cMOAT) and ABCG2 (BCRP), present on the bile canalicular membrane. The various processes mediating drug elimination, either through metabolic breakdown or excretion, likely impact substantially on interindividual variability in drug handling. This report provides an update on current strategies to individualize irinotecan chemotherapy based on each patient's genetic constitution, which may ultimately lead to more selective use of this agent.
authors.affiliation: Molecular Pharmacology Section, Medical Oncology Branch, National Cancer Institute, Bethesda, MD, USA.
authors.forename: Nicola F
authors.initials: NF
authors.lastname: Smith
authors.forename: William D
authors.initials: WD
authors.lastname: Figg
authors.forename: Alex
authors.initials: A
authors.lastname: Sparreboom
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000972:Antineoplastic Agents, Phytogenic / Q000493:pharmacokinetics*; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D043182:Carboxylesterase / Q000235:genetics / Q000378:metabolism; D051544:Cytochrome P-450 CYP3A / Q000235:genetics / Q000378:metabolism; D005838:Genotype; D014453:Glucuronosyltransferase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000077146:Irinotecan; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins / Q000235:genetics / Q000378:metabolism; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D010597:Pharmacogenetics; D010641:Phenotype; D011355:Prodrugs / Q000493:pharmacokinetics*
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D020168:ATP Binding Cassette Transporter, Subfamily B, Member 1; D000070997:ATP Binding Cassette Transporter, Subfamily G, Member 2; D018528:ATP-Binding Cassette Transporters; D000972:Antineoplastic Agents, Phytogenic; D002166:Camptothecin; D043182:Carboxylesterase; D051544:Cytochrome P-450 CYP3A; D014453:Glucuronosyltransferase; D000077146:Irinotecan; D026901:Membrane Transport Proteins; D000089762:Multidrug Resistance-Associated Protein 2; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D009363:Neoplasm Proteins; D011355:Prodrugs; C000715087:ABCC2 protein, human; C116614:ABCG2 protein, human; C507084:Abcb1b protein, mouse; C421109:multidrug resistance-associated protein 1