A low molecular weight PSMA-based fluorescent imaging agent for cancer

We synthesized YC-27 3 to provide a fluorescent imaging agent for the prostate-specific membrane antigen (PSMA), a marker for hormone-independent prostate cancer and tumor neovasculature, with suitable pharmacokinetics for use in vivo. Immediate precursor trifluoroacetate salt of 2-(3-{5-[7-(5-amino-1-carboxy-pentylcarbamoyl)-heptanoylamino]-1-carboxy-pentyl}-ureido)-pentanedioic acid 2 was conjugated with a commercially available near-infrared light-emitting dye (IRDye 800CW) to provide 3 in 72% yield. YC-27 3 demonstrated a PSMA inhibitory activity of 0.37 nM and was capable of generating target-to-nontarget ratios of at least 10 in PSMA-expressing PC3-PIP vs. PSMA-negative PC3-flu tumors in vivo. YC-27 3 may be useful for study of PSMA-expressing tissue in preclinical models or for intraoperative guidance.