Synthesis and radiolabeling of a somatostatin analog for multimodal imaging

W. Barry Edwards; Kexian Liang; Baogang Xu; Carolyn J. Anderson; Samuel Achilefu

doi:10.1117/12.648096

10 February 2006 Synthesis and radiolabeling of a somatostatin analog for multimodal imaging

W. Barry Edwards, Kexian Liang, Baogang Xu, Carolyn J. Anderson, Samuel Achilefu

Author Affiliations +

Proceedings Volume 6097, Optical Molecular Probes for Biomedical Applications; 609703 (2006) https://doi.org/10.1117/12.648096
Event: SPIE BiOS, 2006, San Jose, California, United States

Abstract

A new multimodal imaging agent for imaging the somatostatin receptor has been synthesized and evaluated in vitro and in vivo. A somatostatin analog, conjugated to both 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraaceticacid (DOTA) and cypate (BS-296), was synthesized entirely on the solid phase (Fmoc) and purified by RP-HPLC. DOTA was added as a ligand for radiometals such as ⁶⁴Cu or ¹⁷⁷Lu for either radio-imaging or radiotherapy respectively. Cytate, a cypatesomatostatin analog conjugate, has previously demonstrated the ability to visualize somatostatin receptor rich tumor xenografts and natural organs by optical imaging techniques. BS-296 exhibited low nanomolar inhibitory capacity toward the binding of radiolabeled somatostatin analogs in cell membranes enriched in the somatostatin receptor, demonstrating the high affinity of this multimodal imaging peptide and indicating its potential as a molecular imaging agent. ⁶⁴Cu, an isotope for diagnostic imaging and radiotherapy, was selected as the isotope for radiolabeling BS-296. BS-296 was radiolabeled with ⁶⁴Cu in high specific activity (200 μCi/μg) in 90% radiochemical yield. Addition of 2,5-dihydroxybenzoic acid (gentisic acid) prevented radiolysis of the sample, allowing for study of the ⁶⁴Cu -BS-296 the day following radiolabeling. Furthermore, inclusion of DMSO at a level of 20% was found not to interfere with radiolabeling yields and prevented the adherence of ⁶⁴Cu -BS-296 to the walls of the reaction vessel.

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W. Barry Edwards, Kexian Liang, Baogang Xu, Carolyn J. Anderson, and Samuel Achilefu "Synthesis and radiolabeling of a somatostatin analog for multimodal imaging", Proc. SPIE 6097, Optical Molecular Probes for Biomedical Applications, 609703 (10 February 2006); https://doi.org/10.1117/12.648096

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