Search

By modifying the structures of targeted A 2A R antagonists and tracers, novel compounds 3 , 7a , 9 , 12c , and BIBD-399 were designed and synthesized. In vitro inhibition experiments demonstrated that 3 , 12c , and BIBD-399 have high affinity for A 2A R. [ 18 F]3 and [ 18 F]BIBD-399 were successfully synthesized. In terms of biological distribution, the brain uptake of [ 18 F]MNI-444 exhibits greater than that of [ 18 F]3 and [ 18 F]BIBD-399. PET imaging shows that [ 18 F]3 is off-target in the brain, while [ 18 F]BIBD-399 and [ 18 F]MNI-444 can be specifically imaged in regions with high A 2A R expression. Differently, [ 18 F]BIBD-399 could quickly reach equilibrium in the targeted region within 10 min after administration, while [ 18 F]MNI-444 shows a slowly increasing trend within 2 h of administration. [ 18 F]BIBD-399 is mainly metabolized by the liver and kidney, and there is no obvious defluorination in vivo. Additional in vitro autoradiography showed that the striatal signals of [ 18 F]BIBD-399 and [ 18 F]MNI-444 were inhibited by the A 2A R antagonist SCH442416 but not by the A 1 R antagonist DPCPX, demonstrating the high A 2A R binding specificity of [ 18 F]BIBD-399. Molecular docking further confirms the high affinity of MNI-444 and BIBD-399 for A 2A R. Further tMCAo imaging showed that [ 18 F]BIBD-399 can sensitively distinguish between infarcted and noninfarcted sides, a capability not observed with [ 18 F]MNI-444. Given its pharmacokinetic properties and the ability to identify lesion regions, [ 18 F]BIBD-399 has potential advantages in monitoring A 2A R changes, meriting further clinical investigation.

Accurate quantification of amyloid beta (Aβ) plaques is an important indicator for Alzheimer's disease diagnosis and treatment. For this purpose, new highly sensitive Aβ tracers were designed by regulating the position and number of nitrogen atoms. A series of derivatives of florbetapir (AV45) containing different numbers and positions of N atoms were synthesized and evaluated for in vitro affinity and in vivo biodistribution. Preliminary study results showed that [ 18 F]BIBD-124 and [ 18 F]BIBD-127 had better clearance rates and less in vivo defluorination than AV45 in ICR (ICR = Institute of Cancer Research) mice. Autoradiography and molecular docking indicated that the binding sites of [ 18 F]BIBD-124/127 were similar to that of [ 18 F]AV45. Micro-positron emission tomography-computed tomography imaging further demonstrated that [ 18 F]BIBD-124 could monitor Aβ plaques similar to [ 18 F]AV45. Besides, the imaging contrast of [ 18 F]BIBD-124 is better than that of [ 18 F]AV45. Mass spectrometric metabolic analysis showed that BIBD-124 was less demethylated than AV45 without subsequent acetylation, which might explain its less non-specific uptake and higher imaging contrast. Gauss calculations further confirmed that the introduction of N 5 in [ 18 F]BIBD-124 decreased demethylation. Considering imaging contrast and in vivo defluorination, [ 18 F]BIBD-124 is expected to be a promising radiotracer of Aβ plaques for further clinical trials.