Y-33075 (Y-39983) is a potent ROCK inhibitor, with an IC ₅₀ of 3.6 nM. Y-33075 also inhibits PKC and CaMKII more potently than Y-27632, and the IC ₅₀ s of Y-27632 and Y-33075 for PKC are 9.0 μM and 0.42 μM, respectively, whereas the IC ₅₀ s of Y-27632 and Y-33075 for CaMKII are 26 μM and 0.81 μM, respectively. The IC ₅₀ s of Y-27632 and Y-33075 for PKC is 82 and 117 times those for ROCK, respectively, whereas the IC ₅₀ s of Y-27632 and Y-33075 for CaMKII is 236 and 225 times those for ROCK, respectively. Y-33075 (Y-39983, 10 μM) extends neurites in the retinal ganglion cells (RGCs) compared with those in RGCs treated without Y-39983. Y-33075 (Y-39983, 1 μM) inhibits the contraction of rabbit ciliary artery segments evoked by histamine in Ca ²⁺ -free solutions. Y-33075 (10 μM) shows no effect on the [Ca ²⁺ ]i increase with the high-potassium (high-K) solution.

In rabbits, Y-39983 (≥0.01%) significantly lowers intraocular pressure (IOP) at 2 hours after topical administration. In monkeys, Y-39983 (0.05%)-treated eyes show significant reduction of IOP between 2 and 7 hours after topical administration. Y-39983 (100 μM) increases the regenerating axons of retinal ganglion cells (RGCs) in the eyes of the rats.