Treatment of diabetic macular edema with an inhibitor of vascular endothelial-protein tyrosine phosphatase that activates Tie2.

AKB-9778 is a small-molecule competitive inhibitor of vascular endothelial-protein tyrosine phosphatase (VE-PTP) that promotes Tie2 activation and reduces vascular leakage and neovascularization in mouse models. The purpose of this study was to test the safety, tolerability, pharmacokinetics, and biological activity of AKB-9778 in patients with diabetic macular edema (DME). Open-label, dose-escalation clinical trial. Four dose cohorts of 6 patients with DME self-administered subcutaneous injections of 5 mg, 15 mg, 22.5 mg, or 30 mg AKB-9778 twice daily for 4 weeks. Patients were seen weekly during a 4-week treatment period for safety assessments, best-corrected visual acuity (BCVA) assessment by Early Treatment Diabetic Retinopathy Study protocol, and measurement of central subfield thickness (CST) by spectral-domain optical coherence tomography. Additional safety assessments were performed at 6, 8, and 12 weeks. Safety assessments, change from baseline BCVA, and change from baseline CST. All doses were well tolerated. A modest, transient reduction in blood pressure and adverse events consistent with vasodilatory activity of AKB-9778 emerged at doses of 22.5 mg or more twice daily. At the week 4 primary end point, BCVA improved 5 letters or more from baseline in 13 of the 18 patients receiving 15 mg or more twice daily; 1 patient improved by 10 to 15 letters, and 2 patients improved by more than 15 letters. Among 18 patients receiving 15 mg or more twice daily, CST decreased by more than 100 μm in 5 patients and by 50 to 100 μm in 2 patients. There was a significant correlation between reduction in CST and improvement in BCVA. No safety concerns were identified after systemic administration of AKB-9778 for 4 weeks in patients with DME, and doses of 15 mg or more twice daily reduced macular edema and improved vision in some patients. This is a preliminary demonstration of clinical safety and efficacy of a VE-PTP inhibitor and Tie2 activator.