In contrast, TKIs such as lapatinib and tucatinib with lower molecular weight seem to penetrate the BBB more efficiently showing promising treatment option for HER2-positive breast cancer with brain metastases (Duchnowska et al., 2018; Nader-Marta et al., 2022; Wang et al., 2022; Werter et al., 2022). Here, ERBB2 is linked to breast cancer.