Design and synthesis of new pyrazolylbenzimidazoles as sphingosine kinase-1 inhibitors

Sphingosine-1 kinase (SphK1) is one of the important enzymes of phospholipids and its inhibition is one of the therapeutic strategies for different diseases. SphK1 over expression is observed in different types of cancer indicating its important role in tumor growth. In search of effective SphK1 inhibitors, a new series of pyrazolylbenzimidazoles was synthesized and evaluated as sphingosine kinase-1 (SphK1) inhibitors. In order to evaluate the binding affinities of all the synthesized compounds, all compounds were subjected to docking analysis and fluorescence quenching. The results indicated that there is a consistency between the docking and the fluorescence quenching results, which revealed that compounds 47 and 48 exhibited significant decrease in the fluorescence intensity of SphK1 as well as they formed stable protein-ligand complexes. In addition, enzyme inhibition assay was performed which showed effective inhibitory potential toward SphK1. Moreover, IC50 values displayed that compounds 47 and 48 were the most promising compounds. In addition, antiproliferation study for all the synthesized compounds was performed against NCI-60 cell line panel. The target compounds 47 and 48 demonstrated effective antitumor activity and growth inhibitory potential toward cancer cell lines. Most of these compounds fit well into the ATP-binding site of SphK1 and form significant hydrogen-bonding interactions with catalytically relevant residues as predicted by molecular docking. In this article, insight has been given for the importance of pyrazolylbenzimidazoles as SphK1 inhibitors and the perspectives that they hold for future research.