title: Prediction of the systemic exposure to oral 9-amino-20(S)-camptothecin using single-sample analysis.
abstract: The purpose of this study was to develop and validate limited-sampling strategies for prediction of the area under the plasma-concentration time curves (AUCs) of the lactone and total (i. e., lactone plus carboxylate) forms of the novel topoisomerase-I inhibitor 9-amino-20(S)-camptothecin (9-AC). Complete pharmacokinetic curves for both drug species were obtained from 32 patients who received the drug orally in a clinical phase I setting at dose levels ranging from 0.25 to 1.10 mg/m2. The concentrations of the lactone and carboxylate forms of 9-AC in plasma were measured by HPLC. Using data from 20 randomly selected patients, forward-stepwise multivariate regression analysis was used to generate modeling strategies incorporating data from one, two, or three plasma samples. The simultaneous optimal prediction of both 9-AC lactone and 9-AC total AUCs was obtained with sample time points at 0.33, 3.0, and 11.0 h after drug dosing. Validation of the models on an independent data set comprising data of the remaining 12 patients demonstrated that 9-AC lactone and 9-AC total AUCs could be predicted sufficiently unbiased and precise using one and two time points: [AUC (ng. h/ml) = 7.103*C3 + 4.333] for 9-AC lactone and [AUC (ng. h/ml) = 9.612*C3 + 13.77*C11 - 44.11] for 9-AC total, where C3 and C11 represent the 9-AC plasma concentrations in ng/ml at 3 and 11 h after drug dosing. Application of the proposed models will be valuable in the determination of 9-AC population pharmacokinetics and permits treatment optimization for patients on the basis of individual pharmacokinetic characteristics through restricted drug monitoring in clinical routines.
authors.affiliation: Department of Medical Oncology, Rotterdam Cancer Institute (Daniel den Hoed Kliniek) and University Hospital Rotterdam, Rotterdam, The Netherlands. sparreboom@onch.azr.nl
authors.forename: A
authors.initials: A
authors.lastname: Sparreboom
authors.forename: M J
authors.initials: MJ
authors.lastname: de Jonge
authors.forename: C J
authors.initials: CJ
authors.lastname: Punt
authors.forename: W J
authors.initials: WJ
authors.lastname: Loos
authors.forename: K
authors.initials: K
authors.lastname: Nooter
authors.forename: G
authors.initials: G
authors.lastname: Stoter
authors.forename: M G
authors.initials: MG
authors.lastname: Porro
authors.forename: J
authors.initials: J
authors.lastname: Verweij
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000970:Antineoplastic Agents / Q000097:blood / Q000493:pharmacokinetics*; D019540:Area Under Curve; D002166:Camptothecin / Q000031:analogs & derivatives* / Q000097:blood / Q000493:pharmacokinetics; D002851:Chromatography, High Pressure Liquid; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged
chemical_list: D000970:Antineoplastic Agents; C080125:9-aminocamptothecin; D002166:Camptothecin