A phase I pharmacokinetics study of 9-nitrocamptothecin in patients with advanced solid tumors

Purpose

9-Nitrocamptothecin (9-NC) is a novel orally administered camptothecin analog. The purpose of this study is to evaluate the pharmacokinetics and safety of 9-nitrocamptothecin in patients with advanced solid tumors.

Methods

The 23 patients for a single-dose pharmacokinetic experiment were divided into 3 dosing cohorts. The dosage of 9-nitrocamptothecin capsule was 1.25, 1.5 and 1.75 mg/m², respectively. The 8 patients for a multiple-dose pharmacokinetic study were orally administered 9-nitrocamptothecin 1.5 mg/m² for 5 consecutive days. Determination of the plasma concentration of 9-nitrocamptothecin was performed by high-performance liquid chromatography-ultraviolet detector technique, and determination of plasma concentration of 9-aminocamptothecin was performed by high-performance liquid chromatography-fluorescence detector technique.

Results

In the single-dose pharmacokinetic study, the mean ± SD 9-nitrocamptothecin C _max were 94.49 ± 41.38, 115.56 ± 63.27 and 147.57 ± 38.19 ng/mL; AUC_0–36 were 877.14 ± 360.90, 961.33 ± 403.58 and 1,189.75 ± 405.80 ng h/mL, respectively; the mean ± SD 9-aminocamptothecin C _max were 12.85 ± 6.46, 10.72 ± 6.58 and 28.74 ± 31.94 ng/mL; AUC_0–36 were 157.61 ± 111.61, 88.71 ± 39.51 and 173.52 ± 122.19 ng h/mL, respectively. In the multiple-dose pharmacokinetic study, the mean ± SD 9-nitrocamptothecin AUC_ss was 907.04 ± 736.47 ng h/mL, C _max was 85.98 ± 47.52 ng/mL, C _min was 18.91 ± 22.50 ng/mL, C _av was 37.79 ± 30.69 ng/mL, DF was 2.16 ± 0.87; the mean ± SD 9-aminocamptothecin AUC_ss was 442.73 ± 308.39 ng h/mL, C _max was 34.83 ± 18.31 ng/mL, C _min was 10.32 ± 6.95 ng/mL, C _av was 18.45 ± 12.85 ng/mL, DF was 1.34 ± 0.42. Comparing single-dose 1.5 mg/m² group with multiple-dose 1.5 mg/m² group, no significant difference was observed in 9-NC pharmacokinetic parameters, but with respect to the metabolite, significant differences were observed in C _max and AUC. The toxicity of 9-NC varied from mild to moderate. No grade 3 or grade 4 toxicity was observed during the study. There was 2- to 13-fold variabilities in 9-NC and 9-AC exposure among different patients for any given dose of 9-NC.

Conclusions

All participants had good tolerance throughout the study. 9-NC and 9-AC exposure did not increase proportionally to the dose ranging from 1.25 to 1.75 mg/m². After 5-day continuous administration, accumulation was observed in the metabolite 9-AC, but not in 9-NC.