A dual fluorinated and iodinated radiotracer for PET and SPECT imaging of β-amyloid plaques in the brain.

ABSTRACT
We report a fluorinated and iodinated radiotracer as a probe for PET/SPECT to detect of β-amyloid (Aβ) plaques in the brain of patients with Alzheimer’s disease (AD). We successfully designed and synthesized the fluorinated and iodinated aurone derivative (3) and its radiolabels ([¹²⁵I]3 and [¹⁸F]3). In binding experiments in vitro, 3 showed high affinity for Aβ aggregates (K_i = 6.81 nM). In brain sections of AD model mice, 3 intensely stained Aβ plaques. Furthermore, a specific plaque labeling signal was observed on the autoradiography of postmortem AD brain sections using [¹²⁵I]3. In biodistribution experiments using normal mice, [¹²⁵I]3 and [¹⁸F]3 displayed good uptake into and a rapid washout from the brain, properties highly desirable for Aβ imaging agents. These results suggest that 3 may function as a PET/SPECT dual imaging agent for detecting Aβ plaques in AD brains.