Subconjunctival delivery of p75^NTR antagonists reduces the inflammatory, vascular, and neurodegenerative pathologies of diabetic retinopathy

PURPOSE. The p75^NTR is a novel therapeutic target validated in a streptozotocin mouse model of diabetic retinopathy. Intravitreal (IVT) injection of small molecule p75^NTR antagonist THX-B was therapeutic and resolved the inflammatory, vascular, and neurodegenerative phases of the retinal pathology. To simplify clinical translation, we sought a superior drug delivery method that circumvents risks associated with IVT injections. METHODS. We compared the pharmacokinetics of a single 40 lg subconjunctival (SCJ) depot to the reported effective 5 lg IVT injections of THX-B. We quantified therapeutic efficacy, with endpoints of inflammation, edema, and neuronal death. RESULTS. The subconjunctival depot affords retinal exposure equal to IVT injection, without resulting in detectable drug in circulation. At week 2 of diabetic retinopathy, the SCJ depot provided therapeutic efficacy similar to IVT injections, with reduced inflammation, reduced edema, reduced neuronal death, and a long-lasting protection of the retinal structure. CONCLUSIONS. Subconjunctival injections are a safe and effective route for retinal delivery of p75^NTR antagonists. The subconjunctival route offers an advantageous, less-invasive, more compliant, and nonsystemic method to deliver p75^NTR antagonists for the treatment of retinal diseases.