Discovery of highly potent and selective VEGFR2 kinase inhibitors for the treatment of rheumatoid arthritis.

Synovial angiogenesis is essential for the development of rheumatoid arthritis (RA). Human vascular endothelial growth factor receptor 2 tyrosine kinase (VEGFR2) is a direct target gene that is notably elevated in RA synovium. Herein, we report the identification of indazole derivatives as a novel class of potent VEGFR2 inhibitors. The most potent compound, compound 25, displayed single-digit nanomolar potency against VEGFR2 in biochemical assays and achieved good selectivity for other protein kinases in the kinome. In addition, compound 25 dose-dependently inhibited the phosphorylation of VEGFR2 in Human Umbilical Vein Endothelial Cells (HUVECs) and showed an anti-angiogenic effect, as evidenced by the inhibition of capillary-like tube formation in vitro. Moreover, compound 25 reduced the severity and development of adjuvant-induced arthritis in rats by inhibiting synovial VEGFR2 phosphorylation and angiogenesis. Overall, these findings provide evidence that compound 25 is a leading potential drug candidate for anti-arthritic and anti-angiogenic therapy.