Synthesis, Preclinical Evaluation, and First-in-Human PET Study of Quinoline-Containing PSMA Tracers with Decreased Renal Excretion

The prostate-specific membrane antigen (PSMA) is considered to be an excellent theranostic target of prostate Cancer (PCa). In this study, three ¹⁸F-labeled PSMA tracers with a more lipophilic quinoline functional spacer were designed, synthesized, and evaluated based on the Glu-Ureido-Lys binding motif. The effect of structure-related lipophilic difference on distribution and excretion of these tracers in vitro and in vivo (cells, rodent, primate, and human) was investigated by comparing with [¹⁸F]DCFPyL. There is no significant correlation between the renal elimination and the lipophilicity of the tracers in all species. However, the higher the lipophilicity of tracer, the higher the radioactivity accumulation in the liver of primate and human, and the less radioactivity is to excrete to the bladder with urine. The screened tracer [¹⁸F]8c, with a K_i value of 4.58 nM, displayed notable low bladder retention and demonstrated good imaging properties in patients with PCa.