Enhanced Antitumor Efficacy of a Combination of CPT‐11, a New Derivative of Camptothecin, and Cisplatin against Human Lung Tumor Xenografts

The objective of this study was to evaluate the antitumor efficacy of combined use of 7‐ethyl‐10‐[4‐(1‐piperidino)‐1‐piperidino]carhonyloxycamptothecin (CPT‐11) and cisplatin (CDDP). The antitumor activities of CPT‐11, CDDP and their combination against 3 human lung tumor xenografts were estimated using congenitally athymic BALB/c (nu/nu) mice. The doses were 47 mg/kg for CPT‐11 and 6 mg/kg for CDDP on days 1, 5 and 9. In combination therapy, half of the single dosage of each agent was used. The doses were administered intraperitoneally. The antitumor activity and toxicity were evaluated in terms of the tumor volume and body weight change of mice, respectively. The combination therapy resulted in a statistically significant tumor regression compared to the use of only CPT‐11 or CDDP in two tumor xenografts out of three. The toxicity of the combination therapy was no higher than that of CPT‐11 or CDDP alone. These results suggest that the antitumor activity of the combination of CPT‐11 and CDDP is superior to that of CPT‐11 or CDDP alone.