In silico studies and in vitro microsomal metabolism of potent MetAP2 inhibitor and in vivo tumor suppressor for prostate cancer: A thioether-triazole hybrid

Background/aim: The in-vitro microsomal metabolism of (S)-3-((2,4,6-trimethylphenyl)thio)-4-(4-fluorophenyl)-5-(1-(6-methoxynaphtalene-2-yl)ethyl)-4H-1,2,4-triazole (SGK636), an anticancer drug candidate was studied using pig microsomal preparations fortified with NADPH to identify the potential S-oxidation and S-dealkylation metabolites. 
Materials and methods: In the present study, the sulfoxide metabolite was synthesized, purified and characterized by chromatographic and spectroscopic methods. SGK636, the S-oxidation and S-dealkylation metabolites were then separated by a reversed phase LC-MS, with UV detection and with an HP-TLC system. The results from the in-vitro microsomal metabolic experiments showed that SGK636 produced the corresponding S-oxidation metabolite (sulfoxide) which was observed by LC-MS, LC-MS/MS and HP-TLC with the identical Rt and Rfx100 values and UV/MS spectra in comparison with the authentic compounds, but no any S-dealkylation metabolite was detected. 
Results: The present results were proved with molecular docking and molecular dynamic studies. Since sulfoxidation process can be reversible and it may partly explain the low amount of sulfoxide metabolite in our experiment, we also incubated the sulphoxide. No conversion back to the substrate (SGK636) was observed, but it produced the corresponding sulphone metabolite. In order to establish if SGK636 is autooxidized, the substrate was also incubated in buffer under standard incubation conditions, but no any autooxidation was observed into the corresponding sulfoxide. We also did a stability work for SGK636-SO (sulfoxide) in buffer to see any possible autooxidation to sulphone or reduction back to SGK636. No conversion was observed in either way. The substrate seems to be stable to metabolic reactions and to autooxidation which could be an advantage in terms of its pharmacological activity. 
Conclusion: The present metabolic and study indicates that SGK 636 underwent S-oxidation. In order to identify the responsible oxydative enzyme, molecular docking and molecular dynamic studies were performed. CYP3A4 was found to be responsible enzyme for S-oxidation.