In vitro binding affinities (IC50) for Tau were as follows: INFT = 7.3 × 10−8 M; ISAS = 4.7 × 10−8 M; NIPZ > 10−6 M. The binding of [125I]ISAS to gray matter (GM) correlated with the presence of Tau in the AD brain, confirmed by anti-Tau immunohistochemistry. Here, MAPT is linked to Alzheimer disease.