Phase I clinical and pharmacokinetic study of oral 9-aminocamptothecin (NSC-603071)

Purpose: 9-Aminocamptothecin (9-AC) is a topoisomerase I inhibitor with high antitumor activity but poor solubility in conventional vehicles. The purpose of this study was to evaluate the toxicities and pharmacokinetics of a colloidal dispersion (CD) formulation of 9-AC when administered orally on a 5 days per week every 2 weeks schedule. Method: This formulation, which was developed for intravenous administration, was orally administered in 20 ml orange juice. A group of 16 cancer patients were treated at doses of 0.2- 0.68 mg/m² daily. Results: Grade 1-2 nausea (n = 9) was common, usually occurring during the last 2 days of dosing. No objective responses or cumulative toxicities were observed. Pharmacokinetic analysis of total 9-AC showed highly variable apparent oral 9-AC clearance and half-life. There was marked interpatient variability at each dose level in the 9-AC AUC and C(max), and these parameters:showed a poor correlation with dose (r² = 0.07 and 0.38, respectively). Conclusions: We conclude that this formulation is not suitable for further clinical development because of poor bioavailability and highly variable and/or saturable absorption or elimination. Another formulation developed for oral administration is under study elsewhere.