Using three separate tumor inoculation models (intracranial, intracardiac, or intravenous injections), Wyatt et al. demonstrated that systemically administered, pH-dependent mucic acid polymer (MAP) NPs conjugated to camptothecin (CPT, MAP-CPT) (Table 3) can effectively target TfR on the luminal side of the BBB, deliver CPT, and inhibit Her2+ BCBM growth in mice [144]. This evidence concerns the gene TFRC and neoplasm.