Abstract
Purpose :
Kinase inhibitors, particularly inhibitors of Rho kinases (ROCKs), lower intraocular pressure in animal models and in humans. In contrast to previous amino acid-based kinase inhibitors, herein is presented a novel class of cyclopropyl-based kinase inhibitors that have advantages in stability. While all of the features of this class are not yet clear, they have demonstrated potent in vivo IOP lowering ability.
Methods :
Hybrid molecules consisting of ethacrynic and tienilic acid isoquinolyl amides were synthesized. These compounds were screened for protein kinase inhibitory activity, including ROCK inhibition, and for cytotoxicity. To investigate the role that unsaturation played in the activity of these molecules, in particular sulfhydryl activity, select molecules were either reduced to their corresponding alkanes, or cyclopropanated. Select compounds were tested for ocular hypotensive activity and tolerability in normotensive Dutch Belted rabbits and Formosan Rock monkeys. Representative compounds were subsequently screened for inhibitory activity against a panel of kinase proteins to assess whether a second target other than Rho kinase might contribute to their IOP-lowering activity.
Results :
Reduction of the alkenes modestly decreased activity at Rho kinase, whereas cyclopropanation led to potent molecules, and revealed single-digit nanomolar potency at JAK and IKK kinases. In vivo testing demonstrated that cyclopropyl acid amides had a distinct pharmacologic profile from compounds containing an amino acid skeleton. In a series of rabbit studies, treatment with cyclopropyl derivatives produced mean IOP reductions of 1 to 5 mm Hg (p<0.01) at 2-4 hours after dosing. Irritation scores were typically only trace (+0.5) hyperemia (Draize scale 0 - 3) lasting 4-8 hours. Addition of distal nitrogen atom produced compounds with maximal efficacy. Testing in in vitro stability assays revealed that resistance to racemization and other forms of in vivo degradation, and revealed that AR-13917 possessed the correct stereochemistry for further studies.
Conclusions :
Compounds containing cyclopropyl acid amides produced significant reductions in IOP with an extended duration of action. Removal of sulfhydryl activity preserved efficacy while improving tolerability in normotensive rabbits and monkeys. This class of Rho kinase inhibitors warrants further in vitro and in vivo studies.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.