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Takeshi Iwase, Brian C. Oveson, Noriyasu Hashida, Raquel Lima e Silva, Jikui Shen, Achim H. Krauss, David C. Gale, Peter Adamson, Peter A. Campochiaro; Topical Pazopanib Blocks VEGF-Induced Vascular Leakage and Neovascularization in the Mouse Retina but Is Ineffective in the Rabbit. Invest. Ophthalmol. Vis. Sci. 2013;54(1):503-511. doi: 10.1167/iovs.12-10473.
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To test the effect of pazopanib, a tyrosine kinase inhibitor that blocks VEGF and platelet-derived growth factor (PDGF) receptors and c-Kit, on vascular leakage and neovascularization (NV) in the retina.
Pazopanib was tested to determine its effect on VEGF-induced vascular permeability via measurement of [3H]mannitol retina to lung (RLLR) and retina to renal leakage ratios (RRLR) and in rho/VEGF mice with subretinal NV. In rabbits, the effect of intravitreal, topical, and systemic pazopanib on VEGF-induced leakage was tested by vitreous fluorophotometry.
In mice, oral pazopanib (40 mg/kg twice a day [bid]) reduced RLLR (0.84 to 0.58, P = 0.0014) and RRLR (0.55 to 0.30, P = 0.0018) in VEGF-injected eyes. After intraocular injection of VEGF into both eyes, topical pazopanib (10 mg/mL three times a day [tid] for 14 days) reduced RLLR (0.85 vs. 0.56, P = 0.001), RRLR (0.44 vs. 0.28, P = 0.0075), and immunoreactive albumin in the retina compared to values in fellow eye controls. Treatment of one eye of rho/VEGF mice with 10 mg/mL, but not 5 mg/mL, pazopanib tid reduced the mean area of subretinal NV compared to that in fellow eyes (0.0055 vs. 0.0025 mm2, P = 0.020). In rabbits, intravitreal pazopanib suppressed VEGF-induced fluorescein leakage, but topical (10 mg/mL four times a day [qid] or 12 mg/mL bid) had no significant effect. Systemic administration of pazopanib by osmotic pump with or without 10 mg/mL drops tid also failed to suppress VEGF-induced leakage.
Administration of pazopanib topically or systemically suppressed retinal vascular leakage in mice, but not rabbits. These data suggest differences in the blood–retinal barrier (BRB) of mice and rabbits and indicate that penetration through the outer BRB may be needed for topically administered drugs to exert effects in the retina.
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