Targeting the MUC4β part of the TM mucin via protein–protein interaction (PPI) inhibitors has, thus, become an alternative route to target MUC4/HER2 overexpressing cancers [16], as well as to rescue the targeting of HER2 positive cancers for which direct HER2 targeting has failed [17] or triggered strong secondary effects [18]. This evidence concerns the gene ERBB2 and cancer.