ITRI-E-247, a novel selective Rho-associated kinase inhibitor, characterized with the potent intraocular pressure lowering effect and less conjunctival hyperemia.

Abstract

Purpose : The Rho-associated protein kinase (ROCK) inhibitors constitute a new class of drugs of glaucoma therapeutics. The purpose of this study is to evaluate the efficacy and safety of one selective ROCK inhibitor ITRI-E-247 in New Zealand White rabbit (NZW).

Methods : The ROCK activity was carried out using the Kinase-Glo® Luminescent kinase assay to determine IC₅₀. The inhibition of fibroblast growth factor receptors (FGFRs) was determined using an active site-directed competition binding assay by LeadHunter™ Discovery Services (Fremont, CA). The myosin light-chain phosphorylation and cellular relaxation were evaluation in A7r5 cells at concentrations ranging from 30-1000 nM. Ocular hypotensive activity and tolerability were evaluated in male New Zealand White rabbits (n = 4/group) at 0.5% and 1% of ITRI-E-247, respectively. Topical ocular doses of 0.5% ITRI-E-247 (35 mL/drop) were administered to both eyes of 3 male New Zealand rabbits. Aqueous humor (AH) samples were taken at designed time points after dosing. Levels of ITRI-E-247 were measured in the samples by Liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Results : ITRI-E-247 is a highly selective and potent ROCK inhibitor. The IC₅₀ value of ITRI-E-247 was 10.9 nM, which achieved almost 100-fold selectivity towards ROCK over FGFRs (34% inhibition at 1000 nM). The FGFR-MAPK signaling inhibition was reported to cause the ocular toxicities (Cancer Treat Rev. 2013; 39: 664-72.). ITRI-E-247 could inhibit myosin light-chain phosphorylation in a concentration-dependent manner and cause cell relaxation in A7r5 cells. In rabbits, 0.5% ITRI-E-247 ophthalmic solution significantly reduced 32% IOP from baseline IOP at 6 hours after topical instillation. No significant ocular toxicities including conjunctival hyperemia was observed in all groups throughout the study. The concentrations of ITRI-E-247 in AH at 4 h and 6 h following a single topical administration of 0.5% ITRI-E-247 were virtually achieved target IC₅₀ value, 4.5±1.9 ng/mL and 3.2±2.5 ng/mL, respectively.

Conclusions : The present study showed potential in developing a second-generation ROCK inhibitor. Selectively target to ROCK but not FGFR, ITRI-E-247 exhibited lowering intraocular pressure and fewer ocular side effects in NZW rabbits.

This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.