ABCB1 and neoplasm: Regardless of whether these data come from an efficacy study in mice [5] or a preclinical microdialysis study in rats using the human equivalent dose of eribulin [7], caution must be exercised when extrapolating data about blood–brain barrier and blood-tumor barrier penetrance from animal models to humans, because interspecies differences exist, particularly in regard to levels of expression and substrate specificity of various efflux transporters, such as P-glycoprotein, within the blood–brain barrier [26].