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).

Striatal uptake of [11C]KF21213 shows a gradual increase for the initial 15 minutes before declining, while its absorption by the cortex and cerebellum decreases swiftly post-injection, aligning with blood levels. As a result, the striatum to cortex and striatum to cerebellum uptake ratios escalate to 8.6±1.6 and 10.5±2.1 (N=4), respectively, within 60 minutes. Initially retained for 5 minutes, [11C]KF21213's striatal activity then diminishes over time, unlike [11C]KF18446, which drops quickly. Similarly, cerebellar activity for both ligands decreases rapidly. The striatum-to-cerebellum uptake ratio for [11C]KF21213 progressively increases to 2.4±0.5 (N=3) over 50-60 minutes, while for [11C]KF18446, it peaks within the first 10 minutes before stabilizing at 1.4±0.3 (N=3) between 25-35 minutes.