In light of the mixed results of [18F]AV-1451 binding to non-AD tauopathies, an in vitro study compared the binding patterns of [11C]PBB3 and [18F]AV-1451.71 PBB3 demonstrated increased labeling of 4R tauopathies (PSP, CBD, FTDP-17 with N279K MAPT mutation) and 3R tauopathies (Pick’s disease, FTDP-17 with G272 MAPT mutation) compared to the weak signals of AV-1451. This evidence concerns the gene MAPT and tauopathy.