METABOLISM OF INDIUM CHELATES ATTACHED TO MONOCLONAL-ANTIBODY - MINIMAL TRANSCHELATION OF INDIUM FROM BENZYL-EDTA CHELATE INVIVO

  • 1 February 1990
    • journal article
    • research article
    • Vol. 31  (2) , 218-224
Abstract
The metabolism of radiolabeled antibodies is important for radioimmunoimaging and therapy. The loss of indium-111 (111In) from the chelate can pose problems in imaging and increases the radiation dose to normal tissues. We have evaluated the loss in vivo of 111In from Lym-1-benzyl-EDTA-111In (an antibody conjugated with isothiocyanatobenzyl-EDTA) in normal mice. A monoclonal antibody (CHA 255) that binds to benzyl-EDTA-indium chelates, but not to other forms of indium, was used to measure the percent of 111In remaining in the chelate. Four days after injection, 97.4 .+-. 2.2% of the 111In in the liver was still in the benzyl-EDTA chelate, as was 99.4 .+-. 0.7% of the 111In in the urine, and 99.1 .+-. 0.7% of the 111In in the blood. Studies in vitro indicate that a benzyl-EDTA-111In-antibody-chelate conjugate is more stable in human serum than a benzyl-DTPA-111In conjugate, and that both benzyl-chelate conjugates are much more stable than an unsubstituted DTPA conjugate.