In vitro activity: Nedaplatin (Aqupla) is a derivative of cisplatin for inhibition of tumor colony forming units with IC50 of 28.5 μg/mL. Nedaplatin is a platinum compound which is used for cancer chemotherapy. Nedaplatin inhibits the proliferation of SBC-3 cells by 98%, 93%, 75%, 54%, 27%, 6%, and 2% at a concentration of 0.005 μg/mL, 0.01 μg/mL, 0.025 μg/mL, 0.05 μg/mL, 0.1 μg/mL, 0.25 μg/mL, and 0.5 μg/mL, respectively. The IC50 value of Nedaplatin for growth inhibition of SBC-3 cells is 0.053 μg/mL.

Cell Assay: The inhibition of cell (including human SCLC cell line SBC-3 and human NSCLC cell line PC-14) proliferation after drug treatments as the antitumor activity using a regrowth assay is messured. Briefly, cells are exposed to drugs alone or in combination for 6 days at 37°C in an atmosphere of 100% humidity with 5% CO2; the cells are then pipetted six to eight times until almost all cells appeared as single cells and counted with a counter. For each drug, concentration-effect curves are drawn as plots of the fraction of surviving cells (unaffected cell fraction, fu) versus drug concentration. The cell proliferation ratio of the treated:control cultures (T:C%) is calculated as follows: [(the number of treated cells on day 6)/(the number of treated cells on day 0)]/[(the number of control cells on day 6)/(the number of control cells on day 0)] × 100%. The IC50 is defined as the drug concentration required for a 50% reduction in the number of cells. Four or five independent experiments are carried out for each. To check the effect of the drug treatment schedule on the effect of the combination, the cells are treated either by simultaneous exposure to the two drugs or by sequential exposure to Nedaplatin followed by irinotecan (Nedaplatin→irinotecan) and vice versa (irinotecan→Nedaplatin) for 3 hours. For the sequential exposure treatment, cells are exposed to the first drug for 3 hours, ished in fresh medium once, and then immediately exposed to the second drug for 3 hours. The treated cells are cultured in drug-free medium until evaluation.