NRG1 and cancer: Interestingly, using a systems biology approach, a human monoclonal antibody seribantumab (MM-121), that inhibits NRG1-stimulated ERBB3 signaling with low nanomolar IC50 values compared with lapatinib and other ERBB inhibitors, was identified to be more effective in blocking ligand-induced activation of ERBB3 signaling network, which led to a Phase II clinical trial of human cancers (29, 30, 44).