Another highly potent nonxanthene 18F PET radioligand analog of SCH442416, [18F]MNI-444 (Ki = 2.8 nM, human recombinant A2ARs) was developed to noninvasively monitor A2A receptor densities and functions in the brain of patients with PD.131 [18F]MNI-444 radioligand has shown high uptake, rapid kinetics, and high target/nontarget ratios in the brain, consistent with A2A receptor distribution.131,132 Thus far, [18F]MNI-444 has turned out to be a superior imaging tracer among all the 18F PET radioligands for studying and mapping the A2AR in the brain.133 A list of all A2A receptor PET radioligands is presented in Table 2.
