Radiolabeling of MAG 3-morpholino oligomers with 188Re at high labeling efficiency and specific radioactivity for tumor pretargeting

Abstract

We are investigating a novel pretargeting approach involving an initial IV injection of antitumor antibody conjugated with a phosphorodiamidate morpholino oligomer (MORF, a DNA analog) and the subsequent IV injection of the radiolabeled complement oligomer (cMORF). In this paper, the cMORF was labeled with 188Re using MAG 3 as chelator for therapeutic applications. Since (c)MORFs are unstable in acidic condition, an optimal labeling pH was first selected and the other labeling factors were then examined. A labeling efficiency of greater than 90% can be achieved even at a concentration of MAG 3–cMORF as low as 0.8 μM. The labeled cMORF is stable and capable of hybridizing to its complement.