Growth factors are an extremely heterogeneous group of proteins that regulate the growth and differentiation of various cell types. They are capable of stimulating cellular growth, proliferation and cellular differentiation. Growth factor receptors are the first stop in cells where the signaling cascade for cell differentiation and proliferation begins. Growth factors, which are ligands that bind to the receptor are the initial step to activating the growth factor receptors and tells the cell to grow and/or divide. These receptors may use the JAK/STAT, MAP kinase, and PI3 kinase pathways.

Their potent biological effects make them attractive targets for the development of novel therapeutic agents. But, because of their poor pharmacokinetic properties, recombinant proteins are unlikely to be the optimal agents for clinical use.