Study of the Purification of 177Lu-DOTAELA Complex

Abstract

Radiolabeled analog of the gonadotropin releasing hormone having a close molecular weight, namely 177Lu -1,4,7,10- tetra-azacyclododecane -1,4,7,10- tetraacetic acid - 4-[[(1R)-2-[5-(2-fluoro-3-methoxyphenyl)-3-[[2-fluoro-6 (trifluoromethyl)phenyl]methyl]-4-methyl-2,6 dioksopirimidin-1-yl]-1-phenylethyl]amino]butanoic acid (177Lu-DOTAELA) plays an important role in radionuclide receptor therapy for triple negative breast cancer. The preparation with a label was purified using C18 Sep-Pak cartridge and various types of cation exchangers. The reaction mixture was passed through the column after radiolabeling. The pure product of 177Lu-DOTAELA was eluted with ethanol and acetonitrile. The flushing was performed with distilled water and acetate buffer solution pH 5.0. The elution was performed using sterile vials. Ethanol was removed by heating at 80°C. The final product was diluted with physiological solution. According to the data obtained in experiments, 177Lu3+ cations and the 177Lu-DOTAELA complex are retained on the cartridge with C18 and filled with various cation exchangers. Standard implementation of purification with C18, which is usually effective for eliminating non-included 177Lu3+ ions, requires the use of a substances reducing the radiolysis effect (e.g., ascorbic acid) for maintaining radiochemical purity (RCP) of 177Lu-DOTAELAas well as the search for other eluents (e.g., trifluoroacetic acid) increasing the polarity of solvent.