Anti-angiogenic collagen IV-derived peptide target engagement with α_vβ₃ and α₅β₁ in ocular neovascularization models

AXT107, a collagen-derived peptide that binds integrins α_vβ₃ and α₅β₁ with high affinity, suppresses vascular endothelial growth factor (VEGF) signaling, promotes angiopoietin 2-induced Tie2 activation, and suppresses neovascularization (NV) and vascular leakage. Immunohistochemical staining for α_vβ₃ and α₅β₁ was markedly increased in NV compared with normal retinal vessels. After intravitreous injection of AXT107, there was no staining with an anti-AXT107 antibody on normal vessels but robust staining of NV that co-localized with α_vβ₃ and α₅β₁. Likewise, after intravitreous injection, fluorescein amidite-labeled AXT107 co-localized with α_vβ₃ and α₅β₁ on NV but not normal vessels. AXT107 also co-localized with α_v and α₅ at cell-cell junctions of human umbilical vein endothelial cells (HUVECs). AXT107-integrin binding was demonstrated by ex vivo cross-linking/pull-down experiments. These data support the hypothesis that AXT107 therapeutic activity is mediated through binding α_vβ₃ and α₅β₁ which are markedly upregulated on endothelial cells in NV providing selective targeting of diseased vessels which has therapeutic and safety benefits.