Anti-angiogenic collagen IV-derived peptide target engagement with _v3 and ₅₁ in ocular neovascularization models

AXT107, a collagen-derived peptide that binds integrins ccvI33 and cc5I31 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 alpha(v)beta(3) and alpha(5)beta(1) 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 alpha(v)beta(3) and alpha(5)beta(1). Likewise, after intravitreous injection, fluorescein amidite-labeled AXT107 co-localized with alpha(v)beta(3) and alpha(5)beta(1) on NV but not normal vessels. AXT107 also co-localized with alpha(v) and alpha(5) 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 alpha(v)beta(3) and alpha(5)beta(1) which are markedly up-regulated on endothelial cells in NV providing selective targeting of diseased vessels which has therapeutic and safety benefits.