The recently proposed ligands 2-(2-([18F]fluoro)pyridin-4-yl)-9H-pyrrolo[2,3-b:4,5c′]dipyridine ([18F]PI-2620) and 1-[18F]fluoro-3-((2-((1E,3E)-4-(6-(methylamino)pyridine-3-yl)buta-1,3-dien-1-yl)benzo[d]thiazol-6-yl)oxy)propan-2-ol ([18F]PM-PBB3, official generic name: florzolotau (18F) or florzolotau) proved to be promising tau biomarkers in patients with suspected 4R tauopathies in several studies, including patients with a clinical diagnosis of PSP (1,2) or amyloid-β (Aβ)–negative corticobasal syndrome (CBS) (3,4). The gene discussed is MAPT; the disease is supranuclear palsy, progressive, 1.