Rational Design of Pyridinium Styryl Derivatives as PET Tracers for Cardiac Amyloidosis Imaging

Cardiac amyloidosis (CA) is a complex restrictive cardiomyopathy, and while treatment options are advancing rapidly, specific diagnostic probes for CA have rarely been developed or reported. In this study, a series of pyridinium styryl derivatives were designed and synthesized, exhibiting specific affinity for immunoglobulin light chain protein amyloidosis (AL). Through a structure–activity relationship analysis and bioevaluations, [18F]23 was identified as the first candidate for PET/CT imaging in rodents. However, due to its increasing lipophilicity, the uptake in healthy myocardium remained high (SUV = 3.8) during imaging, making it unsuitable for detecting myocardial amyloidosis. Subsequently, we rationally designed and optimized the second candidate, [68Ga]37, maintaining moderate affinity (IC50 = 134.3 nM) while increasing hydrophilicity. Compound [68Ga]37 successfully labeled AL deposits on myocardial slices and demonstrated rapid clearance from healthy myocardium. Overall, [68Ga]37 represents a promising PET tracer for CA imaging and warrants further clinical evaluation.