MAPT and Alzheimer disease: Because MK-6240 was initially screened in vitro for NFT binding affinity using AD brain homogenates rich in NFT and an amyloid plaque tracer for counterscreening [15], and seemed to bind to the same site as AV-1451 in that tissue material, we predicted that, just like AV-1451, MK-6240 would exhibit high binding affinity and selectivity for PHF-tau lesions relative to non-PHF-tau lesions, Aβ deposits and α-synuclein and transactive response DNA binding protein-43 (TDP-43) aggregates.