R. Ratnakaram

Gene Therapy for Leber Congenital Amaurosis Caused by RPE65 Mutations: Safety and Efficacy in 15 Children and Adults Followed Up to 3 Years

OBJECTIVE To determine the safety and efficacy of subretinal gene therapy in the RPE65 form of Leber congenital amaurosis using recombinant adeno-associated virus 2 (rAAV2) carrying the RPE65 gene. DESIGN Open-label, dose-escalation phase I study of 15 patients (range, 11-30 years of age) evaluated after subretinal injection of the rAAV2- RPE65 vector into the worse-functioning eye. Five cohorts represented 4 dose levels and 2 different injection strategies. MAIN OUTCOME MEASURES Primary outcomes were systemic and ocular safety. Secondary outcomes assayed visual function with dark-adapted full-field sensitivity testing and visual acuity with Early Treatment Diabetic Retinopathy Study charts. Further assays included immune responses to the vector, static visual fields, pupillometry, mobility performance, and optical coherence tomography. RESULTS No systemic toxicity was detected; ocular adverse events were related to surgery. Visual function improved in all patients to different degrees; improvements were localized to treated areas. Cone and rod sensitivities increased significantly in the study eyes but not in the control eyes. Minor acuity improvements were recorded in many study and control eyes. Major acuity improvements occurred in study eyes with the lowest entry acuities and parafoveal fixation loci treated with subretinal injections. Other patients with better foveal structure lost retinal thickness and acuity after subfoveal injections. CONCLUSIONS Gene therapy for Leber congenital amaurosis caused by RPE65 mutations is sufficiently safe and substantially efficacious in the extrafoveal retina. There is no benefit and some risk in treating the fovea. No evidence of age-dependent effects was found. Our results point to specific treatment strategies for subsequent phases. APPLICATION TO CLINICAL PRACTICE Gene therapy for inherited retinal disease has the potential to become a future part of clinical practice. TRIAL REGISTRATION clinicaltrials.gov Identifier: NCT00481546.

Ab-Externo AAV-Mediated Gene Delivery to the Suprachoroidal Space Using a 250 Micron Flexible Microcatheter

Background The current method of delivering gene replacement to the posterior segment of the eye involves a three-port pars plana vitrectomy followed by injection of the agent through a 37-gauge cannula, which is potentially wrought with retinal complications. In this paper we investigate the safety and efficacy of delivering adeno-associated viral (AAV) vector to the suprachoroidal space using an ab externo approach that utilizes an illuminated microcatheter. Methods 6 New Zealand White rabbits and 2 Dutch Belted rabbits were used to evaluate the ab externo delivery method. sc-AAV5-smCBA-hGFP vector was delivered into the suprachoroidal space using an illuminated iTrackTM 250A microcatheter. Six weeks after surgery, the rabbits were sacrificed and their eyes evaluated for AAV transfection using immunofluorescent antibody staining of GFP. Results Immunostaining of sectioned and whole-mounted eyes demonstrated robust transfection in all treated eyes, with no fluorescence in untreated control eyes. Transfection occurred diffusely and involved both the choroid and the retina. No apparent adverse effects caused by either the viral vector or the procedure itself could be seen either clinically or histologically. Conclusions The ab externo method of delivery using a microcatheter was successful in safely and effectively delivering a gene therapy agent to the suprachoroidal space. This method presents a less invasive alternative to the current method of virally vectored gene delivery.

Short-term response of macular oedema to intravitreal bevacizumab

Background/aims: Bevacizumab has been shown to be an effective treatment of macular oedema. This study assesses the response of macular oedema to bevacizumab with specific focus on the first 24 h postinjection. Methods: Subjects with diabetic macular oedema (DMO) or exudative age-related macular degeneration (ARMD) received intravitreal bevacizumab injections. Early Treatment of Diabetic Retinopathy Study (ETDRS) visual acuity and OCT macular thickness measurements were obtained at baseline, 1, 3, 6, 24 and 48 h, 1 week and 1 month postinjection. Results: The average baseline OCT was 452.91 µm (SD 182.96, range 249.00 to 784.00). After injection, there was a statistically significant decrease in OCT thickness within 2 h with a plateau phase out to 24 h, followed by a significant drop between 24 and 48 h, and a return towards baseline between 1 week and 1 month. Average changes in ETDRS visual acuity were not statistically significant, though many patients experienced a positive outcome. Conclusion: While there is an immediate pressure-related effect, it appears that the anti-VEGF effects of bevacizumab require approximately 24 h to become active and persist for 2–3 weeks. These results suggest that injections at 2–3-week intervals might provide improved clinical outcomes, compared with the currently typical 4–6-week interval of injections.