DC101, an anti-VEGFR2 agent, promotes high-endothelial venule formation and immune infiltration versus SAR131675 and fruquintinib

There is an increasing interest in combining immune checkpoint inhibitors (ICIs) with anti-angiogenic drugs to enhance their anti-tumor effects. In this study, three anti-angiogenic agents, DC101 (acting on VEGFR2), SAR131675 (acting on VEGFR3), and fruquintinib (a small-molecule inhibitor acting on multiple targets) were administered to B16F1-OVA-loaded C57BL/6 mice. Immune cells infiltration in the tumor tissues, vascular normalization, and high-endothelial venule (HEV) formation were assessed to provide evidence for drug combination. Both DC101 and fruquintinib significantly slowed the melanoma growth and increased the proportion of CD3+ and CD8+ T cells infiltration compared with SAR131675, of note, the effect of DC101 was more pronounced. Moreover, DC101 and fruquintinib increased the interferon-γ and perforin levels, meanwhile, DC101 increased the granzyme B levels, whereas fruquintinib and SAR131675 did not. Only the fruquintinib-treated group showed decreased regulatory T cells infiltration. We found upregulation of PD-L1 expression in tumor cells and CD45+ immune cells in DC101-treated group as well as upregulation of PD-1 expression on CD3+ T cells. However, fruquintinib only increased PD-L1 expression in tumors. Both DC101 and fruquintinib reduced the proportion of CD31+ vessels, while DC101 increased the ratio of α-SMA +/CD31+ cells and reduced the expression of HIF-1α more than fruquintinib. Moreover, DC101 enhanced the infiltration of dendritic cells and B cells, and local HEV formation. In conclusion, our data indicate that DC101 may be a better choice for the combined clinical application of ICIs and anti-angiogenic agents.