Rapidly Accelerated Fibrosarcoma, Vascular Endothelial Growth Factor Receptor, Platelet-Derived Growth Factor Receptor, and Fibroblast Growth Factor Receptor kinases (RAF/VEGFR/PDGFR/FGFR)

The RAF/VEGFR/PDGFR/FGFR kinase group comprises a set of pivotal signaling enzymes that drive both tumor cell intrinsic growth and the development of the tumor microenvironment [1, 5]. This cluster includes the RAF family of serine/threonine kinases (A-RAF, B-RAF, and C-RAF) and three major families of receptor tyrosine kinases: Vascular Endothelial Growth Factor Receptors (VEGFR1-3), Platelet-Derived Growth Factor Receptors (PDGFR-alpha/beta), and Fibroblast Growth Factor Receptors (FGFR1-4) [1, 7]. Biologically, these kinases mediate the Ras-Raf-MEK-ERK and PI3K-AKT-mTOR pathways, which are essential for cell proliferation, survival, and migration [2, 6]. In the context of oncology, VEGFRs and FGFRs are primary drivers of angiogenesis, while PDGFRs contribute to pericyte recruitment and vessel stabilization [11, 17]. Mutations or overactivation of these pathways are common in various malignancies, leading to uncontrolled growth and robust vascularization [5, 12]. Drugs targeting this collective group, known as multi-kinase inhibitors (MKIs), are used to treat various solid tumors, including hepatocellular carcinoma and renal cell carcinoma, by simultaneously inhibiting tumor cell signaling and cutting off the blood supply [1, 15]. These inhibitors typically function by competing with ATP for binding to the intracellular kinase domains, thereby preventing downstream signal transduction [2, 8]. However, the broad spectrum of activity associated with these targets often results in characteristic toxicities such as hypertension, hand-foot skin reaction, and metabolic disturbances like hyperphosphatemia [6, 16].

Other names

Multi-kinase targetAngiogenesis-related kinasesRTK/RAF signaling clusterRAF/VEGFR/PDGFR/FGFR

Multi-kinase inhibitors (MKIs) targeting this group typically act as ATP-competitive inhibitors that bind to the intracellular kinase domain of the receptors (VEGFR, PDGFR, FGFR) and the RAF kinases [1, 2]. By stabilizing the kinase in an inactive conformation (Type II) or binding the active form (Type I), these drugs prevent the phosphorylation of downstream substrates, thereby blocking the MAPK/ERK and PI3K/AKT signaling cascades [5, 7]. This dual action inhibits both tumor cell proliferation and the angiogenic processes required for tumor growth and metastasis [11, 17].