Y-33075, a selective inhibitor of ROCK derived from Y-27632, exhibits greater potency than Y-27632 with an IC50 of 3.6 nM.

CaMK II:810 nM, ROCK:3.6 nM, PKC:420 nM

Y-33075 (Y-39983) is a potent ROCK inhibitor with an IC50 of 3.6 nM. It also inhibits PKC and CaMKII more effectively than Y-27632, with respective IC50s of 0.42 μM and 0.81 μM for Y-33075 compared to 9.0 μM and 26 μM for Y-27632. The IC50s of Y-27632 and Y-33075 for PKC are 82 and 117 times higher than those for ROCK, respectively, while for CaMKII, they are 236 and 225 times higher, respectively [1]. Y-33075 (10 μM) promotes neurite extension in retinal ganglion cells (RGCs) compared to untreated RGCs [2], and Y-33075 (1 μM) inhibits histamine-induced contraction of rabbit ciliary artery segments in Ca2+-free solutions [3].

Y-39983, when administered topically at concentrations of 0.01% or higher, significantly reduces intraocular pressure (IOP) in rabbits within 2 hours. In monkeys, eyes treated with 0.05% Y-39983 demonstrate a substantial decrease in IOP from 2 to 7 hours post-administration. Additionally, at a concentration of 100 μM, Y-39983 fosters the growth of regenerating axons in the retinal ganglion cells (RGCs) of rats.