The first generationof tau PET tracers including Flortaucipir (also namedAV1451 or T807),19,20TKH5351,21 and PBB3,22 show binding both in vitro and in vivo to both AD (3/4R tau) as well as PSP/CBD (4R tau).11 Among the second-generation tau PET tracers, RO948(23) and MK6240(24) selectively show high binding in AD and no bindingin non-AD tauopathies, while PI2620(25) and PMPBB3 (also named APN1607)26 show high binding in the AD braintissue, but also in the PSP/CBD brain tissue. The gene discussed is MAPT; the disease is Alzheimer disease.