Labeling of monoclonal antibodies with a 67Ga-phenolic aminocarboxylic acid chelate |
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Authors: | Siegfried Matzku Jochen Schuhmacher Henning Kirchgeßner Josef Brüggen |
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Affiliation: | (1) Institute of Nuclear Medicine, German Cancer Research Center, D-6900 Heidelberg, Federal Republic of Germary |
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Abstract: | As a chelating agent for labeling antibodies (Abs) with metallic radionuclides, a propionic acid substituted ethylenediamine N,N -di-[(o-hydroxyphenyl) acetic acid] (P-EDDHA), which tighly complexes 67Ga, was synthesized. The 67Ga-P-EDDHA chelate was coupled in aqueous solution to IgG at a molar ratio of 1:1 via carbodiimide. The average coupling yield was 15%. A specific activity of 4 mCi/mg IgG could be obtained with commercially supplied 67Ga. In vitro stability was evaluated in human serum at 37° C and showed a half-life of about 120 h for the release of 67Ga from the labeled Ab during the initial phase of incubation. This in vitro halflife is similar to that measured for 111In-DTPA labeled Abs. Because of the high stability of the 67Ga-P-EDDHA chelate, the in vivo formation of radioactive labeled transferrin by transchelation, as described for 111In-DTPA labeled Abs, should, however, be reduced by this labeling technique. |
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Keywords: | Labeled antibodies 67Ga Propionic acid substituted phenolic aminocarboxylic acid carbodiimide coupling |
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