Add time:08/07/2019         Source:sciencedirect.com

To develop androgen and progesterone receptor-based radioligands for SPECT imaging we synthesized several radioiodinated 17α-iodovinyl testosterone and 19-nortestosterone analogs and evaluated their biological properties. The synthesis of these compounds proceeds via the (17α,20E/Z)stannyl intermediates and involves addition of tri-n-butyltin hydride to the 17α-ethynyl group of the steroid using either azobisiso butyronitrile or triethylborane as a catalyst. The stannyl derivatives are stereospecifically converted to the corresponding (17α,20E/Z)iodovinyl derivatives using molecular iodine, or to the [125I]iodovinyl analogs using [125I]NaI and H2O2. Androgen and progesterone receptor (AR and PgR) binding affinities were measured via a competitive in vitro binding assay. In general 19-nortestosterone derivatives showed higher receptor affinities as compared to the testosterone derivatives. In the latter series the highest PgR binding affinities were observed with the (17α,20Z)iodovinyl-19-nortestosterone (IVNT) (92 vs 100 for R5020) followed by the 7α-methyl analog, whereas the highest AR binding affinity was observed with the 7α-Me-(17α,20Z)IVNT (54 vs 100 for 5α-dihydrotestosterone). These derivatives were also labeled with 125I and evaluated for their in vivo target organ uptake (prostate and estrogen-primed uterus). The highest PgR-mediated target tissue uptake was observed with the (17α,20Z)-[125I]IVNT and its 7α-methyl derivatives whereas only one derivative, the 7α-Me-(17α,20Z)-[125I]IVNT, showed AR-mediated dorsal prostate retention. Although some of the IVNT derivatives have interesting binding properties, the lack of in vivo selectivity does suggest that the 123I-labeled analogs are unlikely to be suitable for imaging of AR and PgR-rich tissues.

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