N-(META-[I-125]IODOPHENYL)MALEIMIDE - AN AGENT FOR HIGH-YIELD RADIOLABELING OF ANTIBODIES

In an effort to radiolabel antibodies, N-(m-[I-125]iodophenyl)maleimid e (m-[I-125]IPM) was prepared by the demetallation of an N-[m-tri-(n-b utyl)stannylphenyl]maleimide intermediate. The unlabeled intermediate was synthesized in greater-than-or-equal-to 75% yield using a palladiu m catalyzed reaction of hexabutylditin with m-bromoaniline, followed b y reaction with maleic anhydride and ring annulation. All products wer e confirmed by NMR and elemental analysis. Labeling with I-125 was car ried out in a biphasic mixture containing chloramine-T (radiochemical yield greater-than-or-equal-to 70%). Rabbit IgG modified with the hete robifunctional crosslinking agent N-succinimidyl-3-(2-pyridyldithio)pr opionate (SPDP) and bovine serum albumin were conjugated with m-[I-125 ]IPM (yield: 40 and 80%, respectively). In addition, m-[I-125]IPM was conjugated to rabbit IgG subunits (HL) in 70% yield. The in vitro stab ility of the radiolabeled proteins in serum showed < 1% deiodination o ver 24 h.