ERBB2 and breast cancer: In order to improve drug efficacy by overcoming tumour cell receptor heterogenicity, Houdaihed et al. formulated a polymeric nanoparticle functionalized with Fab fragments targeting both HER2 and EGFR receptors for the delivery of paclitaxel (PTX) and Everolimus (EVER) in SK-BR-3 (HER2-positive/EGFR moderate) breast cancer cells and spheroids.