KF21213 shows a high affinity for the adenosine A2A receptors (Ki=3.0 nM). KF21213 is a highly selective ligand for mapping CNS adenosine A2A receptors.

A2A receptor:ki： 3.0 nM

KF21213 shows a high affinity for the adenosine A2A receptors in vitro (Ki=3.0 nM) and a very low affinity for the A1 receptors (Ki>10,000 nM).KF21213 as a PET ligand for mapping adenosine A2A receptors in the central nervous system (CNS).

The uptake of [11C]KF21213 by the striatum gradually increases for the first 15 min and then decreases. The uptake by the cortex and cerebellum is rapidly decreased after injection. Their levels are compatible with that in the blood. Consequently, the uptake ratios of striatum to cortex and striatum to cerebellum increases up to 8.6±1.6 and 10.5±2.1 (N=4), respectively, by 60 min. The striatal activity level of [11C]KF21213 is retained for the initial 5 min and then gradually decreased with time, whereas that of [11C]KF18446 rapidly decreases.The cerebellar activity of the two ligands rapidly decreases.The striatum-to-cerebellum uptake ratio for [11C]KF21213 gradually increases to 2.4 6 0.5 (N 5 3) by 50-60 min, whereas that for [11C]KF18446 increases for the first 10 min and remains constant (1.4±0.3, N=3, at 25-35 min).