Vandetanib is a multi-kinase inhibitor targeting primarily receptor tyrosine kinases, such as vascular endothelial growth factor receptors (VEGFR1, KDR, and FLT4), epidermal growth factor receptor (EGFR), and fibroblast growth factor receptor (FGFR; Morabito et al.). It most potently inhibits KDR with an IC₅₀ of 40 nM. It also inhibits non-receptor tyrosine kinases such as RET, ABL, and SRC as well as several serine/threonine kinases (Carlomagno et al.; Hennequin et al.; Kiselyov et al.; Levinson & Boxer).