Receptor tyrosine kinase/growth factor signaling
Receptor tyrosine kinase cell signaling pathways regulate a variety of cellular processes including cell growth, proliferation, differentiation, survival, gene transcription, metabolic regulation, and others. Receptor tyrosine kinase signaling pathways are activated by the binding of a ligand, such as a growth factor, to the receptor tyrosine kinase. Receptor tyrosine kinase signaling pathways are inhibited by complex negative feedback loops which function to attenuate the activated receptor signaling. 
Figure 1. Binding of a growth factor (e.g., EGF, HGF) to a receptor tyrosine kinase activates the receptor tyrosine kinase and typically causes the dimerization of the two receptor monomers. The receptors are activated by phosphorylation within their kinase domains. Once the receptor is turned on, numerous downstream pathways are activated including MAP kinase signaling, JAK/STAT signaling, and PI3K/AKT1/MTOR signaling. Specific nodes in the pathway that are therapeutically actionable are noted.
EGFR, ERBB2, KIT, MET, and ALK are the most frequent biomarkers that serve as inclusion criteria in therapies targeting the receptor tyrosine kinase/growth factor signaling pathway.
Biomarkers in the receptor tyrosine kinase/growth factor signaling pathway serve as inclusion eligibility criteria in 1324 clinical trials, of which 921 are open and 403 are closed. The genes ERBB2, EGFR, ALK, FLT3, and ROS1 on this pathway most frequently harbor alterations that are inclusion eligibility criteria for clinical trials.
Of the trials that contain alteration(s) in the receptor tyrosine kinase/growth factor signaling pathway as inclusion criteria, 13 are early phase 1 (8 open), 21 are n/a (16 open), 327 are phase 1 (198 open), 217 are phase 1/phase 2 (153 open), 562 are phase 2 (400 open), 20 are phase 2/phase 3 (14 open), 147 are phase 3 (121 open), and 8 are phase 4 (6 open) .