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Glenn J. Jaffe, Jaque L. Duncan, Weng Tao, CNTF Study Group; A Phase 2 Study of Encapsulated CNTF-Secreting Cell Implant (NT-501) In Patients with Geographic Atrophy Associated with Dry AMD. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1651.
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To report the 18-month Phase 2 study results of an encapsulated CNTF-secreting cell implant in eyes with geographic atrophy associated with dry AMD.
The CNTF study consists of 48 participants that were randomized in a 2:1:1 ratio to receive an intravitreal high or low CNTF output implant, or to sham surgery, respectively. BCVA was measured by an Electronic Visual Acuity Tester (EVA) using the Early Treatment Diabetic Retinopathy Study (ETDRS) protocol, retinal thickness was measured by time domain optical coherence tomography (OCT) and lesion size was measured by fundus photography, each at 4, 6, 12, and 18 months following implant placement. CNTF concentration, released from explanted implants and in vitreous samples, was measured by ELISA.
Visual function was stabilized, as measured by 15-letter loss, in the high dose-treated group compared to sham and low dose groups at 12 and 18 months among eyes with baseline BCVA 20/63 or better. The mean BCVA in the high dose group was 10.5 and 10.0 letters greater than the low dose/sham group at 12 months and 18 months respectively, a difference that was statistically significant at 12 months (p=0.03). Stabilized visual acuity was accompanied by corresponding structural changes; there was a dose-dependent increase in retinal thickness as early as 4 months post-implant and this increase was maintained through 6, 12 and 18 months (p<0.001). The observed retinal thickness increase was predominately located in the outer nuclear layer. GA lesion area growth rate was reduced in treated groups at 12 and 18 months. Both the NT-501 implant and the implant procedure were well tolerated; no serious adverse events associated with the implant or implantation procedure were reported. The explanted devices showed healthy cells and stable CNTF output up to 12 months.
Intraocular CNTF delivered by ECT produced long-term stabilized visual acuity and increased retinal thickness without serious adverse events, in eyes with geographic atrophy associated with non-neovascular AMD. These data support next stage clinical studies in a larger patient population.
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