Non-systemic kinase inhibitors (NSKI) offer a novel approach for the treatment of Diabetic Macular Edema

Abstract

Purpose : Diabetic macular edema (DME) is a debilitating disease causing blurred vision, floaters and gradual deterioration of eyesight that ultimately results in blindness. The pathophysiology of the disease is complex involving both inflammation and angiogenesis. NSKIs are designed to inhibit specific kinases involved in inflammatory and VEGF signalling cascades. Utilising in vitro and in vivo experiments we investigate the potential of NSKIs, to inhibit both inflammatory and angiogenic mechanisms associated with DME.

Methods : Inhibitory kinase activity of the NSKI TOP1257 was assessed in competition binding assays, with determination of dissociation constants (K_d, KinomeScan^TM) for P-38 alpha (P38-α) and Src family kinases (SFK), Src and Lck. Anti-inflammatory effects were assessed in vitro via inhibition of inflammatory cytokine release from PBMCs, harvested from healthy volunteers, stimulated with either lipopolysaccharide (LPS) or anti-CD3/anti-CD28. In vivo effects were assessed in a rat endotoxin induced uveitis model. LPS (100 ng) was administered via IVT with test compounds administered as topical eye drops. 6 hours after insult, eyes were enucleated and pro-inflammatory cytokine release measured in posterior eye tissue by ELISA. Anti-angiogenic effects were assessed in a VEGF-stimulated HUVEC model.

Results : TOP1257 is a potent inhibitor of P38-α and SFK kinases with Kd values of < 20nM. In cellular assays, TOP1257 was highly efficacious with IC₅₀ values of 1.0 and 0.9 nM against LPS stimulated IL-8 and TNFα release respectively and 9.1nM against IFNy release from anti-CD3/anti-CD28 stimulated cells. In vivo, TOP1257, after topical administration, demonstrated dose dependent inhibition of pro-inflammatory cytokine release with statistically significant inhibition of IL-1b, IL-6 and MCP-1 achieved with a dose of 500 μg/eye. In the VEGF-dependent angiogenesis assay, TOP1257 demonstrated potent inhibition of tube length (6.7 ng/ml IC₅₀) and network branching (6.0 ng/ml IC₅₀) and was superior to Dexamethasone in the model.

Conclusions : TOP1257 is a potent inhibitor of P38-α and SFK; key kinases involved in inflammatory and angiogenic signalling cascades. Here, we demonstrate that TOP1257 can effectively inhibit inflammatory and angiogenic cascades offering a novel treatment modality for DME patients.

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