Mechanism of action of vorolanib and differentiation from other anti-vascular endothelial growth factor receptor tyrosine kinase inhibitors

Abstract

Purpose : Pathological angiogenesis is a hallmark of cancer as well as numerous ocular conditions, including wet age-related macular degeneration (wAMD). As receptor tyrosine kinases (RTKs) such as vascular endothelial growth factor receptors (VEGFRs) play a role in pathological angiogenesis, pan-VEGFR tyrosine kinase inhibitors (TKIs) such as vorolanib, sunitinib, and axitinib are being explored for treatment of these diseases. This present study utilized established methods to compare the antiangiogenic potential of these 3 anti-VEGFR TKIs as well as to differentiate these TKIs.

Methods : Kinase activity was measured using a HotSpot™ assay to identify the TKIs that inhibited RTKs implicated in pathological angiogenesis. For each TKI, half maximal inhibitory concentration (IC₅₀) values for VEGFRs were determined. A human umbilical vein endothelial cell sprouting assay was used to measure in vitro inhibition of angiogenesis, and the chorioallantoic membrane assay utilized to assess in vivo angiogenesis. Computer modeling was performed to examine interactions between vorolanib and VEGFRs because the mode of binding for vorolanib had not previously been characterized. A melanin binding assay was performed for each of the 3 TKIs as an additional method of differentiation.

Results : All 3 TKIs showed strong pan-VEGFR inhibition. In vitro, they effectively inhibited angiogenesis, and in vivo, they were more effective at inhibiting vascular endothelial growth factor (VEGF)-induced angiogenesis than bevacizumab, an anti-VEGF antibody. Based on computer modeling, vorolanib is predicted to be a type II inhibitor of VEGFRs, and this is important as type II inhibitors have greater selectivity than type I TKIs. The TKIs were further differentiated as only axitinib potently inhibited TIE2 (up to 89%) while only sunitinib bound melanin.

Conclusions : Vorolanib, sunitinib, and axitinib bound RTKs implicated in pathological angiogenesis and exhibited pan-VEGFR inhibition. Only axitinib potently inhibited TIE2, and only sunitinib bound melanin. Retaining TIE2 function is essential for maintaining vascular stability, and melanin binding risks impacting normal cell function. The properties of vorolanib make it of therapeutic interest for treatment of wAMD and other ocular conditions characterized by pathological angiogenesis.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.