3-(Alkyl(dialkyl)amino)benzothieno[2,3-f]quinazolin-1(2H)-ones (4-9) have been designed using Ellipticine structure as a model, replacing the carbazole core and the pyridine ring with a dibenzothiophene and a pyrimidine moiety, respectively. New benzothienoquinazolinones (4-9) have been synthesized by a simple one-pot reaction employing 3-aminodibenzothiophene as starting material. The benzothienoquinazolinones obtained (4-9), were evaluated for their anticancer activity against two breast cancer cell lines, MDA-MB-231 and MCF-7. The results revealed that compounds 4 and 7 presented a good antitumor activity toward the triple negative MDA-MB-231, without cytotoxicity against non-tumoral cells. Furthermore, the compounds 4 and 7 can be considered important molecular multi-target tools for their dual inhibition of different cellular proteins, i.e. Tubulin and human Topoisomerase I, involved in relevant cellular processes, as predicted by in silico studies and demonstrated by in vitro assays (for compound 4).