Results of Top1 DNA cleavage assay and cytotoxicity assay.

1Chemical Abstracts Registration Number.2Top1 inhibition ranking: 0 (no activity); + (20–50% of 1 µM CPT activity); ++ (50–75% of 1 µM CPT activity); +++ (75–100% of 1 µM CPT activity); ++++ (equipotent or more potent than 1 µM CPT).3Cytotoxic activity measured in the US National Cancer Institute (NCI) 60 human tumour cell line anticancer drug screen [47]. GI50 corresponds to the concentration of the drug (molar) resulting in a 50% growth inhibition.4determined previously, published on-line (http://dtp.nci.nih.gov/); in case of camptothecin, the data has been averaged from six experiments, for all other compounds, only one experiment has been performed.5determined during this work, data from single experiment.