Other chemical scaffolds worthy of further investigation include purine derivatives such as NSC 0053340 and NSC 0042379, pyrimidine derivatives such as NSC 0318814, and analogues of 2-mercaptobenzenesulphonamide such as NSC 0674004, which all display activity in the Top1 inhibition assay and similarly high in vitro antitumour activity, with the highest potency in renal cancer cells (GI50 values between 15 and 25 μM, see Table 3). The gene discussed is TOP1; the disease is renal carcinoma.