HL-217, a new topical anti-angiogenic agent, inhibits retinal vascular leakage and pathogenic subretinal neovascularization in Vldlr^-/- mice

HL-217 is a new synthetic angiogenesis inhibitor. Platelet derived growth factor (PDGF) is a vasoactive factor and has been implicated in proliferative retinopathies. In this study, we examined the mechanism of action and efficacy of topical application of HL-217 on subretinal neovascularization in very low-density lipoprotein receptor knockout (Vldlr^-/-) mice. In three-week-old male Vldlr^-/- mice, HL-217 (1.5 or 3 mg/ml) was administered twice per day for 4 weeks by topical eye drop instillation. Neovascular areas were then measured. We used a protein array to evaluate the expression levels of angiogenic factors. The inhibitory effect of HL-217 on the PDGF-BB/PDGFRβ interaction was evaluated in vitro. The neovascular area in the Vldlr^-/- mice was significantly reduced by HL-217. Additionally, HL-217 decreased the expression levels of PDGF-BB protein and VEGF mRNA. Moreover, HL-217 dose-dependently inhibited the PDGF-BB/PDGFRβ interaction (IC₅₀ = 38.9 ± 0.7 μM). These results suggest that HL-217 is a potent inhibitor of PDGF-BB. HL-217, when applied topically, is an effective inhibitor of subretinal neovascularization due to its ability to inhibit the pro-angiogenic effects of PDGF-BB.