title: Pharmacokinetics and pharmacodynamics of 9-aminocamptothecin infused over 72 hours in phase II studies.
abstract: A novel derivative of camptothecin, 9-aminocamptothecin (9-AC), is currently under Phase II evaluation in various cancers. Exceptionally mild toxicities were observed in patients with brain tumors who were treated with anticonvulsants. To investigate a pharmacokinetic interaction between 9-AC and anticonvulsants, and to evaluate the pharmacodynamics of 9-AC, we investigated the clinical pharmacology of 9-AC, administered by a 72-h infusion, in three Phase II studies. Plasma concentrations of total 9-AC (lactone plus carboxylate) at a steady state were measured in 56, 10, and 14 patients with non-small cell lung cancer, malignant glioma, and head and neck cancer, respectively. For lung cancer or glioma patients, 9-AC was infused at 45 (51 patients) or 59 (15 patients) microg/m2/h, and 9-AC was infused at 35.4 microg/m2/h in head and neck cancer patients. All glioma patients had been treated with phenytoin or carbamazepine. 9-AC clearance did not differ among the dosage rates, but differed according to the diseases (P = 0.002). Glioma patients had a higher clearance (1.0-18.0; median, 2.0 liters/h/m2) than lung cancer patients (0.3-5.1; median, 0.9 liters/h/m2). A logistic regression model described the relationship between the 9-AC concentration and the probability of grade 4 neutropenia, which was the main toxicity. Observed incidences of grade 4 neutropenia for patients with model-predicted probability of 0-20%, 20-40%, and 40-100% were 10%, 32%, and 67%, respectively, and corresponded to 9-AC concentration of <54, 54-86, and >86 ng/ml, respectively. Anticonvulsants seem to induce the clearance of 9-AC, and the concentration of 9-AC predicts the probability of grade 4 neutropenia.
authors.affiliation: Section of Hematology/Oncology, The University of Chicago, Illinois 60637, USA.
authors.forename: H
authors.initials: H
authors.lastname: Minami
authors.forename: T E
authors.initials: TE
authors.lastname: Lad
authors.forename: M K
authors.initials: MK
authors.lastname: Nicholas
authors.forename: E E
authors.initials: EE
authors.lastname: Vokes
authors.forename: M J
authors.initials: MJ
authors.lastname: Ratain
mesh_terms: D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000008:administration & dosage; D001772:Blood Cell Count / Q000187:drug effects; D001932:Brain Neoplasms / Q000188:drug therapy*; D002166:Camptothecin / Q000008:administration & dosage / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy*; D002294:Carcinoma, Squamous Cell / Q000188:drug therapy*; D004334:Drug Administration Schedule; D005260:Female; D005910:Glioma / Q000188:drug therapy*; D016179:Granulocyte Colony-Stimulating Factor / Q000008:administration & dosage; D006258:Head and Neck Neoplasms / Q000188:drug therapy*; D006801:Humans; D007262:Infusions, Intravenous; D016015:Logistic Models; D008175:Lung Neoplasms / Q000188:drug therapy*; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged
chemical_list: D000927:Anticonvulsants; D016179:Granulocyte Colony-Stimulating Factor; C080125:9-aminocamptothecin; D002166:Camptothecin