P-Glycoprotein (P-gp), an efflux transporter from the adenosine triphosphate (ATP)-binding cassette (ABC) transporters family, mediates the efflux of several compounds, including Aβ peptides, and its reduced expression has been associated with Aβ accumulation and increased senile plaque formation, thus being related to the progression of the AD [20,22,23]. The gene discussed is PGP; the disease is Alzheimer disease.