Targeted delivery of anti-angiogenic agent TNP-470 using water-soluble polymer in the treatment of choroidal neovascularization.

Purpose: The conjugation of drugs with water-soluble polymers such as poly(vinyl alcohol) (PVA) tends to prolong the half-life of drugs and facilitate the accumulation of drugs in tissues involving neovascularization. The purpose of this study was to evaluate the effect of TNP-470-PVA conjugate on the proliferation of endothelial cells in vitro and on experimental choroidal neovascularization (CNV) in vivo.
Methods: TNP-470 was conjugated in PVA by a dimethylaminopyridine-catalyzed reaction. The effects of TNP-470-PVA and free TNP-470 on the proliferation of human umbilical vein endothelial cells (HUVECs) and bovine retinal pigment epithelial cells (BRPECs) were evaluated by the tetrazolium-based colorimetric assay (XTT assay). Experimental CNV was induced by subretinal injection of gelatin microspheres containing basic fibroblast growth factor, into rabbits. Thirty rabbits were intravenously treated either with TNP-470-PVA (n = 8), free TNP470 (n = 5), free PVA (n = 5), or saline (n = 12) daily for 3 days, 2 weeks after implantation of gelatin microspheres. Fluorescein angiography was performed to detect the area with CNV, and the evaluation was made by computerized measurement of digital images. These eyes were also examined histologically. To observe the accumulation of conjugate, 3 rabbits with CNV received rhodamine B isothiocyanate-binding PVA (RITC-PVA), and the lesion was studied 24 hours later by fluorescein microscopy.
Results: The TNP-470-PVA inhibited the growth of HUVECs, similar to that of free TNP-470. The BRPECs were less sensitive to TNP-470-PVA than were the HUVECs. TNP-470-PVA significantly inhibited the progression of CNV in rabbits (P = 0.001). Histologic studies at 4 weeks after treatment demonstrated that the degree of vascular formation and the number of vascular endothelial cells in the subretinal membrane of the eyes treated with TNP-470-PVA were less than those of the control eyes. RITC-PVA remained in the area with CNV 24 hours after administration.
Conclusions: These results suggest that TNP-470-PVA inhibited the proliferation of HUVECs more sensitively than that of BRPECs, and the targeted delivery of TNP-470-PVA may have potential as a treatment modality for CNV.