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68Ga-Labeled 2-{3-[5-(7-{1-benzyloxycarbonyl-5-[2-(4,7,10-tris-carboxymethyl-1,4,7,10-tetraazacyclododec-1-l)acetylamino]pentylcarbamoyl}-heptanoylamino)-1-carboxypentyl]ureido}pentanedioic acid.


Chopra A.


Molecular Imaging and Contrast Agent Database (MICAD) [Internet]. Bethesda (MD): National Center for Biotechnology Information (US); 2004-2013.
2010 Sep 28 [updated 2010 Dec 28].


The prostate-specific membrane antigen (PSMA) is a type II membrane glycoprotein that is present primarily in the prostate and is overexpressed during all stages of the androgen-insensitive or the metastatic cancer of this organ (1). In addition, PSMA is expressed at lower levels (compared to the prostate) in the neovasculature of some solid tumors (for details, see Elsasser-Beile et al. (1)). Because of its high expression during the development and progression of a malignancy, PSMA is considered to be a good target for the imaging and treatment of prostate cancer (2). Several investigators have reported the use of radio-halogenated (e.g., 18F, 125I, etc.) and 99mTc-labeled small molecule inhibitors for the imaging of PSMA (3). Among these radionuclides, 18F is the most frequently used to label diverse positron emission tomography (PET) agents for diagnostic imaging because its addition to a molecule (usually by the replacement of a hydrogen atom) does not alter its chemical properties; however, due to its short half-life (~110 min), an on-site cyclotron is needed to produce this radio-halogen (4). Recently 68Ga (half-life, ~68 min) has been suggested to be a suitable alternative to the use of 18F for the production of PET imaging probes because 68Ga is easy to produce with a 68Ge/68Ga generator system that does not have to be on-site. However, it is necessary to mention that currently no 68Ge/68Ga generator system has been approved by the United States Food and Drug Administration (Eckelman: personal communication). In addition, 68Ga has been successfully used by some investigators to study cancer and tumor biology (4, 5). On the basis of these observations, and as an extension of their earlier work (for references, see Banerjee et al. (3)), Banerjee et al. developed two 68Ga-labeled, urea-based inhibitors of PSMA ([68Ga]-labeled 2-{3-[5-(7-{1-benzyloxycarbonyl-5-[2-(4,7,10-tris-carboxymethyl-1,4,7,10-tetraazacyclododec-1-l)acetylamino]pentylcarbamoyl}-heptanoylamino)-1-carboxypentyl]ureido}pentanedioic acid ([68Ga]3) and [68Ga]-labeled 2-[3-(1-carboxy-5-{7-[5-carboxy-5-(3-phenyl-2-{3-phenyl-2-[2-(4,7,10-tris-carboxymethyl-1,4,7,10-tetraazacyclododec-1-l)acetylamino]propionylamino}propionylamino)pentylcarbamoyl]heptanoylamino}pentyl) ureido]pentanedioic acid ([68Ga]6)) and evaluated them for biodistribution and the imaging of PSMA-expressing tumors in nude mice (3). This chapter details the results obtained with [68Ga]3. Results obtained with [68Ga]6 are presented in a separate chapter of MICAD ( (6).

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