Pharmacodynamics and pharmacokinetics of a 72-hour infusion of 9-aminocamptothecin in adult cancer patients

• Published in: Journal of clinical oncology Vol. 15; no. 4; p. 1492
• Main Authors: Takimoto, C H, Dahut, W, Marino, M T, Nakashima, H, Liang, M D, Harold, N, Lieberman, R, Arbuck, S G, Band, R A, Chen, A P, Hamilton, J M, Cantilena, L R, Allegra, C J, Grem, J L
• Format: Journal Article
• Language: English
• Published: United States 01.04.1997
• Subjects: Adult; Aged; Antineoplastic Agents - administration & dosage; Antineoplastic Agents - pharmacokinetics; Antineoplastic Agents - pharmacology; Camptothecin - administration & dosage; Camptothecin - analogs & derivatives; Camptothecin - pharmacokinetics; Camptothecin - pharmacology; Chromatography, High Pressure Liquid; Drug Administration Schedule; Female; Half-Life; Humans; Male; Middle Aged; Neoplasms - blood; Neoplasms - drug therapy
• ISSN: 0732-183X
• DOI: 10.1200/JCO.1997.15.4.1492

To investigate the pharmacokinetics and pharmacodynamics of 9-aminocamptothecin (9-AC) infused over 72 hours at doses of 5 to 74 micrograms/m2/h. 9-AC lactone and total (lactone plus carboxylate) plasma concentrations were measured in 44 patients with solid tumors using a high-performance liquid chromatography (HPLC) assay. Fifteen patients underwent extended pharmacokinetic sampling to determine the distribution and elimination kinetics of 9-AC. At steady-state, 8.7% +/- 4.7% (mean +/- SD) of the total drug circulated in plasma as the active 9-AC lactone. Clearance of 9-AC lactone was uniform (24.5 +/- 7.3 L/h/m2) over the entire dose range examined; however, total 9-AC clearance was nonlinear and increased at higher dose levels. In 15 patients treated at dose levels > or = 47 micrograms/m2/h, the volume of distribution at steady-state for 9-AC lactone was 195 +/- 114 L/m2 and for total 9-AC it was 23.6 +/- 10.6 L/m2. The elimination half-life was 4.47 +/- 0.53 hours for 9-AC lactone and 8.38 +/- 2.10 hours for total 9-AC. In pharmacodynamic studies, dose-limiting neutropenia correlated with steady-state lactone concentrations (Css) R2 = .77) and drug dose (R2 = .71). Plasma 9-AC concentrations rapidly declined to low levels following the end of a 72-hour infusion and the mean fraction of total 9-AC circulating in plasma as the active lactone was less than 10%. The pharmacokinetics of 9-AC may have a great impact on its clinical activity and should be considered in the design of future clinical trials of this topoisomerase I inhibitor.