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JS Penn, X Qi, PA Percinel, VS Rajaratnam, DP Bingaman; Studies of the Effect and Mechanism of Action of Topical Nepafenac in a Rat Model of ROP . Invest. Ophthalmol. Vis. Sci. 2002;43(13):2741.
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Purpose: To investigate the angiostatic potential of Nepafenac, or 2-amino-3-benzoylbenzeneacetamide, and its mechanism of action using well-established in vitro and in vivo systems. As a prodrug, the topical NSAID Nepafenac has rapid corneal penetration, and it is metabolized to a potent cyclo-oxygenase (COX I & II) inhibitor, AL-6295A. Methods: Bovine retinal microvascular endothelial cells (BRMEC) were used at 6th passage in VEGF-stimulated proliferation and tube formation assays. In addition, preretinal neovascularization (NV) was produced in rat pups maintained from birth in a variable oxygen atmosphere for 14 days and then removed to room air for up to 6 days before euthanasia (Penn et al, 2001; IOVS, 42:283-290). Starting 1 day prior to removal to room air, some rats received topical QID OU delivery of 0.1% Nepafenac or vehicle (0.5% carbopol, 2.4% mannitol, 0.1% tyloxapol in water). Retinas were harvested at 1, 2, 4, and 6 days post-exposure for retinal VEGF measurement by ELISA. In other rats, topical QID OU delivery of 0.1% Nepafenac, vehicle, or two marketed NSAIDs, 0.5% ketorolac tomethamine or 0.1% diclofenac, was administered from P14-19. Retinas were harvested at P20 for assessment of preretinal NV. Results: Nepafenac showed no significant effect on VEGF-stimulated BRMEC proliferation or tube formation at concentrations between 0.1-10µM. Its metabolite, AL-6295A, significantly inhibited both proliferation and tube formation in a potent, dose-dependent manner. In the rat ROP model, 0.1% Nepafenac caused a 56% inhibition of preretinal NV (p = 0.0292) as compared to vehicle, and the two marketed NSAIDs had no effect. Topical ocular delivery of 0.1% Nepafenac marginally inhibited retinal VEGF protein levels only at P18 (p = 0.0498). Conclusion: COX activity is suspected to provide regulation of angiogenesis in colon cancer and Alzheimer's disease. This is the first evidence of COX inhibition preventing ocular angiogenesis in an animal model. Our VEGF ELISA results suggest that the mechanism by which Nepafenac/AL-6295A inhibits NV is primarily downstream of VEGF, but additional experiments are in progress to further elucidate the link between COX activity and ischemia-induced preretinal NV. Nepafenac is formulated for topical ocular delivery, which restricts its angiostatic action to the eye and may eliminate the systemic toxicity that has limited the clinical utility of other antiangiogenic agents.
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