Discovery of N‑(4‑[18F]Fluoro-5-methylpyridin-2-yl)isoquinolin-6-amine (JNJ-64326067), a New Promising Tau Positron Emission Tomography Imaging Tracer

In Alzheimer’s disease, the density and spread of aggregated tau protein track well with neurodegeneration and cognitive decline, making the imaging of aggregated tau a compelling biomarker. A structure–activity relationship exploration around an isoquinoline hit, followed by an exploration of tolerated fluorination positions, allowed us to identify 9 (JNJ-64326067), a potent and selective binder to aggregated tau with a favorable pharmacokinetic profile and no apparent off-target binding. This was confirmed in rat and monkey positron emission tomography studies using [18F]9.