Novel Fluorophenylated Dihydroimidazotriazinones as Potential Anticancer Agents: Design, Synthesis, In Vitro, Ex Vivo and In Silico Characterisation

Abstract

This article describes the synthesis, structure confirmation, and evaluation of physico-chemical, pharmacological, and pharmacokinetic properties of new para-fluorophenylated dihydroimidazotriazinones. Based on the strategy of heteroannulation, and the concept of fluorine–hydrogen isosterism, an efficient and simple synthetic route was developed. The target heterobicycles (10–18) were obtained by the reaction of nucleophilic building blocks, i.e., 1-(R-phenyl)-2-hydrazinylideneimidazolidine hydroiodides (1–9), with an electrophilic two-carbon synthon, i.e., 2-(4-fluorophenyl)-2-oxoacetic acid. The structures of the new compounds were confirmed by spectroscopic data. The spectrum of anticancer activity, selectivity profile, and effect on caspase levels, as well as the haemolytic and antihaemolytic properties of the molecules were assessed in in vitro and ex vivo studies. Most compounds exhibited antiproliferative activity against human solid tumour and leukaemic cells (superior/comparable to anticancer drugs) with low toxicity to normal cells. Moreover, they revealed a broader spectrum of anticancer activity than previously obtained isosteres without fluorine substitution, suggesting that the isosteric replacement of hydrogen with fluorine was a fruitful modification. The most selective molecules were able to increase the levels of apoptotic caspases in lung, cervical, and breast cancer cells. Molecular docking results revealed that although all fluorophenylated fused triazinones exhibited affinity for the adenosine A2A and A2B receptors, ligands 13, 16, and 17 emerged as promising dual-target candidates due to their superior interaction profiles and stronger binding affinities for both receptor subtypes. All the compounds proved to be safe for red blood cells, as they did not induce any haemolytic effects. Additionally, most of them revealed protective effects on oxidatively stressed erythrocytes, and their antihaemolytic activity was better or comparable to that of antioxidant standards. In silico ADME (absorption, distribution, metabolism, excretion) profiling demonstrated favourable drug-like and pharmacokinetic properties of compounds. Lipophilicity of the molecules was measured by RP-HPLC on an ODS-2 column using an appropriately selected mobile phase. The retention factors, logs k, for most compounds showed a strong correlation with both in silico log P (logarithmic n-octanol/water partition coefficient) and log PHSA (logarithmic human serum albumin/water partition coefficient) values. In summary, among the nine original fluorophenylated fused 1,2,4-triazinones studied, five molecules (11, 13, 14, 15, and 17) seem to be the most promising anticancer drug candidates suitable for further development.