Angiogenesis is a complex phenomenon regulated by both pro- and antiangiogenic factors such as the vascular endothelial growth factor (VEGF), and inflammation may be involved in the process. Although antagonizing VEGF has been proposed as a therapeutic approach to limit corneal angiogenesis, alternative targets are needed. In this study, we demonstrate that, under proangiogenic experimental conditions, human endothelial cells (hECs) express more insulin receptor substrate (IRS)-1 proteins relative to quiescent cells. The antisense oligonucleotide, GS-101 (5'-TATCCGGAGGGCTCGCCATGCTGCT-3'), targeting IRS-1 mRNA, dose-dependently inhibited (p < 0.01) both IRS-1 expression and in vitro angiogenesis (hEC tube-like structure formation) with IC(50) of 8.51 +/- 3.01 microM (mean +/- S.E.M.) and 2.47 +/- 0.56 microM, respectively, demonstrating that partial IRS-1 down-regulation interferes with angiogenesis. The antiangiogenic effects of GS-101 were associated with a decrease in protein kinase B (Akt) activation but not mitogen-activated protein kinase-1/2 and a dose-dependent reduction in vascular endothelial growth factor-A (IC(50) = 5.59 +/- 2.76 microM) and the proinflammatory cytokine interleukin-1beta (IC(50) = 2.19 +/- 1.07 microM) mRNA expression. In accordance, once daily topical application of GS-101 dose-dependently inhibited injury-dependent corneal angiogenesis in vivo (p < 0.05). GS-101 in vivo efficacy was achieved at final tissue concentrations within in vitro EC(50) for IRS-1 down-regulation. In conclusion, these results suggest that IRS-1 is important for angiogenesis and that GS-101 could become a novel therapeutic tool against corneal angiogenesis.