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PURPOSE: Prostate-specific membrane antigen (PSMA) is a cell surface protein that is overexpressed in prostate cancer, including hormone-refractory and metastatic disease. Our goal in this study was to develop a series of PSMA-based imaging agents for clinical use. EXPERIMENTAL DESIGN: We have synthesized and evaluated the in vivo biodistribution of two radiolabeled urea derivatives that have high affinity for PSMA in severe combined immunodeficient mice harboring MCF-7 (breast, PSMA-negative), PC-3 (prostate, PSMA-negative), and LNCaP (prostate, PSMA-positive) xenografts. Radiopharmaceutical binding selectivity and tumor uptake were also evaluated in vivo using dedicated small animal positron emission tomography, single photon emission computed tomography, and gamma scintigraphic imaging devices. N-N-[(S)-1,3-dicarboxypropylcarbamoyl]-S-(11)Cmethyl-L-cysteine ((11)CDCMC K(i), 3.1 nmol/L) and N-N-[(S)-1,3-dicarboxypropylcarbamoyl]-S-3-(125)Iiodo-L-tyrosine ((125)CDCIT K(i), 1.5 nmol/L) were synthesized using (11)CCH(3)I and with (125)INaI/Iodogen, respectively. RESULTS: At 30 minutes postinjection, (11)CDCMC and (125)IDCIT showed tumor/muscle ratios of 10.8 and 4.7, respectively, with clear delineation of LNCaP-derived tumors on imaging. MCF-7- and PC-3-derived tumors showed significantly less uptake of (11)CDCMC or (125)IDCIT. CONCLUSION: These results show the feasibility of imaging PSMA-positive prostate cancer using low molecular weight agents.
Foss et al. (Wed,) studied this question.
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