Cancer is a complex disease that represents one of the biggest public health problems of the developed world. Each year, due to the increasingly unhealthy lifestyle and population aging, the number of people suffering from cancer and consequently deaths due to this disease are increasing. Researchers around the world are striving to discover new effective anti-cancer drugs, among which DNA topoisomerase IIα inhibitors have proven to be very important.
Based on the previous work and the discoveries of researchers from the Department of Pharmaceutical Chemistry at the Faculty of Pharmacy, University of Ljubljana, we prepared a small series of new N-(2-(3-carbamoylbenzyloxy))phenylpyrrolamide catalytic inhibitors of human DNA topoisomerase IIα, which bind to ATP-binding domain on the N-terminal part of the enzyme. All prepared compounds were evaluated by chromatographic and spectroscopic methods and their physicochemical properties were determined.
Inhibitory activity on the DNA topoisomerase IIα enzyme was determined for the three final compounds, 12, 16 and 20, using a commercially available in vitro relaxation assay. All three compounds showed inhibitory activities on the enzyme at low micromolar concentrations. The best inhibitory activity was shown by compound 20 with a mean inhibitory concentration of 6.3 μM, following by compounds 16 and 12, with IC50 values of 7.7 μM and 27 μM. The inhibitory activity of compounds was also tested on the human liver cancer cell line HepG2, and extremely encouraging results were obtained. All tested compounds showed very good cytotoxic activity. Compound 16 proved to be the most potent, with an IC50 value of 0.13 µM. It was followed by compounds 20 and 12, with IC50 values of 1.6 µM and 1.9 µM. Based on these results, we can confirm our assumption that a pyrrolamide structural element that mimics the adenine fragment of the ATP molecule and forms key hydrogen bonds with the amino acid residue Asn120 is important for binding to the active site of the enzyme. In addition, we confirmed the key role of the basic center for cytotoxic activity, which in our case is present on the aminopiperidine or aminopyrrolidine moiety.
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