MAPT and neurodegenerative disease: The first tau PET ligand to be reported was 2-(1-{6-[(2-[18F]fluoroethyl)(methyl)amino]-2-naphthyl}ethylidene)malononitrile ([18F]FDDNP) (Figure 5), although not specific for tau as such, high binding affinity was reported in several neurodegenerative diseases (Bresjanac et al., 2003; Small et al., 2006; Kepe et al., 2010; Nelson et al., 2011; Kepe et al., 2013; Small et al., 2013).