Cancer is a term describing multiple disease states and is one of the most common causes of death. A significant part of the development of anti-cancer drugs is devoted to the research of new molecules, which could effectively and without side-effects treat patients. One of the studied and important targets for the development of new anti-cancer drugs is the human DNA topoisomerase IIα (topo IIα). This is a complex molecular motor, which plays a crucial part in successful cell division, because it enables topological changes of the DNA molecule. By inhibiting this enzyme, the process of cell replication is halted, leading ultimately to cell death. Multiple inhibitors of topo IIα are used in the clinic, such as mitoxantrone and etoposide. The problem with these drugs is that they act as topoisomerase poisons and cause multiple serious side–effects. In addition, cancer cells can eventually develop resistance to the treatment with these drugs. Recent developments of topoisomerase inhibitors focuses on finding substances that work as catalytic inhibitors. One of such classes of compounds are the 4,6-substituted-1,3,5-triazine-2(1H)ones, which bind to the ATPase domain of the topo IIα enzyme.
Based on previous research, which was focused on the optimization of the inhibitory activity (which, unfortunately, led to poorly soluble compounds) we here focused on the synthesis of a new series of 4,6-substituted-1,3,5-triazine-2(1H)ones with improved solubility and retained biological activity. First, we synthesized the corresponding thiourea derivatives, followed by the construction of the 1,3,5-triazin-2(1H)-one scaffold with the use of intramolecular condensation. On this ring, we then attached the 3-fluoro-5-(trifluoromethyl)benzyl fragment. We synthesized four compounds and characterized them with spectroscopic methods and determined their inhibitory activity.
All prepared compounds 5, 6, 13, and 14 showed comparable inhibition of topo IIα as previously published compounds, with inhibitory values superior than the reference drug topo II poison etoposide. Because of better solublity, additional assays with compounds 13 and 14 were performed. With the cleaveage assay we showed that compounds act as catalytic inhibiotrs. Moreover, with the decantenation assay we proved that 13 and 14 inhibit the enzyme at lower concentrations than the reference drug etoposide. We used molecular docking to establish the binding modes in the ATP binding site for these two compounds, which is located on the N-terminal domain of the enzyme. The results of our study represent an important step for further development of this chemical class of compounds with effective inhibiton of the target and appropriate physico-chemical properties.
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