Design, synthesis and evaluation of biological activity of novel fasudil analogues

Nine isoquinoline Rho kinase inhibitors were designed and synthesized on the basis of a ligand-binding pocket model. With fasudil, the only Rho kinase inhibitor marketed to date, as a reference compound, their biological activities were determined, including assays of Rho kinase inhibitory activity, synapse formation, cell viability. Bio-assays were performed by means of MU 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assays and lactate dehydrogenase (LDH) assays. The obtained results indicated that (R)-6H-1-(5-isoquinolinesulfonyl)-2-hydroxy methyl-1-pyrrolidine and (R)-6H-1 -(5-isoquinolinesulfonyl)-2-chloromethyl-1-pyrrolidine exhibited excellent Rho kinase inhibitory activity, deactivation of Rho kinase led to accelerated synapse formation and enhanced cell viability. Therefore they might be potential candidates for preventing various neurological disorders. The brief study on the structure-activity relationship of these isoquinoline analogues demonstrated that modification of inhibitors targeting region D of the Rho kinase binding pocket is quite efficacious, the existence of free amino, chloro- or hydroxyl group as binding sites with region D of Rho kinase is necessary for increasing the inhibitory activity.