The hit compound , 4-(p-tolylsulfonyl)-naphtho-[2,3-g][2], [1], [3]benzothiadiazole-6,11-dione (38_1), is a Top1 inhibitor and shows in vitro antitumour activity in the A-549 non-small-cell lung cancer cell line (IC50 = 0.50±0.0021 μM), as well as the LOVO (colon cancer, IC50 = 43±1.1 μM) and MDA-MB-435 (breast cancer, IC50 = 25±0.97 μM) cell lines [38]. This evidence concerns the gene TOP1 and breast carcinoma.