Synthesis of multi-galactose-conjugated 2′-O-methyl oligoribonucleotides and their in vivo imaging with positron emission tomography
作者:Jussi Mäkilä、Satish Jadhav、Anu Kiviniemi、Meeri Käkelä、Heidi Liljenbäck、Päivi Poijärvi-Virta、Tiina Laitala-Leinonen、Harri Lönnberg、Anne Roivainen、Pasi Virta
DOI:10.1016/j.bmc.2014.10.034
日期:2014.12
Ga-68 labelled 20-O-methyl oligoribonucleotides (anti-miR-15b) bearing one, three or seven D-galactopyranoside residues have been prepared and their distribution in healthy rats has been studied by positron emission tomography (PET). To obtain the heptavalent conjugate, an appropriately protected 1,4, 7-triazacyclononane-1,4,7-triacetic acid (NOTA) precursor bearing a 4-[4-(4,4'-dimethoxytrityloxy) butoxy] phenyl side arm was first immobilized via a base labile linker to the support and the oligonucleotide was assembled on the detritylated hydroxyl function of this handle. A phosphoramidite building block bearing two phthaloyl protected aminooxy groups and one protected hydroxyl function was introduced into the 5'-terminus. One acetylated galactopyranoside was coupled as a phosphoramidite to the hydroxyl function, the phthaloyl protections were removed on-support and two trivalent galactopyranoside clusters were attached as aldehydes by on-support oximation. A two-step cleavage with aqueous alkali and ammonia released the conjugate in a fully deprotected form, allowing radiolabelling with Ga-68 in solution. The mono-and tri-galactose conjugates were obtained in a closely related manner. In vivo imaging in rats with PET showed remarkable galactose-dependent liver targeting of the conjugates. (C) 2014 Elsevier Ltd. All rights reserved.