Off‐target inhibition by active site‐targeting SHP2 inhibitors

Due to the involvement of SHP2 (SH2 domain‐containing protein‐tyrosine phosphatase) in human disease, including Noonan syndrome and cancer, several inhibitors targeting SHP2 have been developed. Here, we report that the commonly used SHP2 inhibitor NSC‐87877 does not exhibit robust inhibitory effects on growth factor‐dependent MAPK (mitogen‐activated protein kinase) pathway activation and that the recently developed active site‐targeting SHP2 inhibitors IIB‐08, 11a‐1, and GS‐493 show off‐target effects on ligand‐evoked activation/trans‐phosphorylation of the PDGFRβ (platelet‐derived growth factor receptor β). GS‐493 also inhibits purified human PDGFRβ and SRC in vitro, whereas PDGFRβ inhibition by IIB‐08 and 11a‐1 occurs only in the cellular context. Our results argue for extreme caution in inferring specific functions for SHP2 based on studies using these inhibitors.