Isomers of 4-[¹⁸F]fluoro-proline: Radiosynthesis, Biological Evaluation and Results in Humans Using PET

E-ISSN： 1874-4729|7|2|123-132

ISSN： 1874-4710

Source： Current Radiopharmaceuticals, Vol.7, Iss.2, 2014-12, pp. : 123-132

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Abstract

Proline and hydroxyproline represent major constituents of mammalian structural proteins, especially of collagen.An efficient radiosynthesis of the lt;supgt;18lt;/supgt;F-labeled proline derivatives cis-/trans-4-[lt;supgt;18lt;/supgt;F]fluoro-L-proline was developedtwo decades ago with the aim to investigate various diseases with altered collagen synthesis using Positron-Emission-Tomography (PET). A number of studies have explored cis-4-[lt;supgt;18lt;/supgt;F]fluoro-L-proline uptake in various pathologiesassociated with increased collagen formation and in neoplastic lesions, but so far the results have not been very promising.Trans-4-[lt;supgt;18lt;/supgt;F]fluoro-L-proline has not yet been investigated in detail, however the compound exhibits considerable differencesin metabolic behavior and biodistribution compared with its cis-enantiomer. In recent years, the D-isomers of cis-/trans-4-[lt;supgt;18lt;/supgt;F]fluoro-proline have been considered as PET tracers as well, and it was observed that both exhibit a preferreduptake into the brain compared with their L-isomers. Surprisingly, a high uptake of cis-4-[lt;supgt;18lt;/supgt;F]fluoro-D-proline was foundin brain areas exhibiting secondary neurodegeneration as well as in areas of radionecrosis after treatment of brain tumors.In this article, the present knowledge on the biological and physiological properties of cis-/trans-4-[lt;supgt;18lt;/supgt;F]fluoro-D/L-prolineand the results in various pathologies are reviewed, including some previously unpublished results from our laboratory.