Topo II inhibitors (Al-Azhar University)

A series of fluoroquinolone analogs (II, III_a-g) derived from Ciprofloxacin hydrazide were designed, and synthesized. The NCI-60 Human Tumor Cell Line Screening assay indicated that compounds II, III_b, and III_f are the most potent among the series and were further selected for five-dose evaluation, where they exhibited potent cytotoxicity with mean GI₅₀ values of 3.30, 2.45, and 9.06 µM, respectively, where they reduced the cell proliferation of most of the tested cell lines with IC₅₀ values significantly lower than the reference drug Etoposide. A selectivity study demonstrated the high selective cytotoxicity of III_f towards cancerous cells over normal mammalian Vero cells, presenting it as a potent and selective antitumor agent. Cell cycle analysis revealed that treatment with II, III_b, or III_f induced cell cycle arrest at the G2/M phase in MCF-7 cells. Topoisomerase II enzyme inhibition assay showed that the three tested compounds are potent topo II inhibitors where compound II (IC₅₀ = 51.66 µM) displayed more potent inhibitory activity compared to the well-known topo II inhibitor Etoposide (IC₅₀ = 58.96 µM), while compounds III_b and III_f showed comparable activity to the reference drug. Molecular modeling study suggested that the topoisomerase inhibitory activity may be attributed to the binding to the Merbarone binding site and chelation with Mg²⁺_.

The DNA topoisomerase II (topo II) enzyme plays an important role in the replication, recombination, and repair of DNA. Despite their widespread applications in cancer therapy, new, selective, and potent topo II inhibitors with better pharmaceutical profiles are needed to handle drug resistance and severe adverse effects. In this respect, an array of 36 new anticancer compounds was designed based on a Xanthone core tethered to multifunctional Pyridine-amines and Imidazole scaffold via alkyl chain linkers. An integrated in silico approach was used to understand the structural basis and mechanism of inhibition of the hybrid xanthone derivatives. In this study, we established an initial virtual screening workflow based on pharmacophore mapping, docking, and cancer target association to validate the target selection process. Next, a simulation-based docking was conducted along with pharmacokinetic analysis to filter out the five best compounds (7, 10, 25, 27, and 30) having binding energies within the range of -60.45 to -40.97 kcal/mol. The screened compounds were further subjected to molecular dynamics simulation for 200 ns followed by MM-GBSA and ligand properties analysis to assess the stability and binding affinity to hTOP2α. The top-ranking hits 3,7-bis(3-(2-aminopyridin-3-ylhydroxy)propoxy)-1-hydroxy-9H-xanthen-9-one (ligand 7) and 3,8-bis(3-(2-aminopyridin-3-ylhydroxy)propoxy)-1-hydroxy-9H-xanthen-9-one (ligand 25) were found to have no toxicity, optimum pharmacokinetic and, DFT properties and stable intermolecular interactions with the active site of hTopo IIα protein. In conclusion, further in vitro and in vivo experimental validation of the identified lead molecules is warranted for the discovery of new human Topoisomerase 2 alpha inhibitors.Communicated by Ramaswamy H. Sarma.