PI6240 and PM-PBB3 bothshow higher binding in brain of AD compared to CBD and PSP, and theregional distribution in brain differs also between AD and the primarytauopathies PSP, CBD.20,22,42 CBD-2115 is an experimental compound designed as a specific 4R tracerfor primary tauopathies, but since it also shows high affinity bindingto AD tissue as well as in vivo observation of lowuptake in mice and non-human primates,34 it is less likely to be further translated as a 4R tau PET tracerfor studies in man.34 The gene discussed is MAPT; the disease is Alzheimer disease.