ATP-binding cassette sub-family B member 1 (P-glycoprotein) and ATP-binding cassette sub-family G member 2 (BCRP) (ABCB1 and ABCG2)

P-glycoprotein (ABCB1) and Breast cancer resistance protein (ABCG2) are ATP-binding cassette (ABC) efflux transporters located on the plasma membrane of various tissues, notably the blood–brain barrier, intestine, liver, kidney, and placenta. They actively extrude a broad range of substrates, including many clinically used drugs, from inside the cell to the extracellular space or into secretory pathways, thereby modulating drug absorption, distribution, excretion, and toxicity. Both are highly expressed in certain tumor cells, where their upregulation contributes to multidrug resistance by decreasing intracellular concentrations of anticancer agents. At barrier tissues (such as the blood–brain barrier), they serve protective roles by restricting entry of xenobiotics and metabolites into sensitive organs. Inhibiting both P-gp and BCRP is often required to significantly increase CNS drug delivery due to their functional redundancy. Genomic variants in these transporters can affect drug disposition and efficacy.

Other names

MDR1P-gpMultidrug resistance protein 1CD243ABC20GP170CLCSPGY1Breast cancer resistance proteinABCG2MXR (mitoxantrone resistance protein)

Efflux of drugs from cells, reducing intracellular concentrations Active transport coupled to ATP hydrolysis Prevention of tissue accumulation (especially brain, testes, placenta) Limitation of oral absorption and tissue penetration of drugs