High yield direct Br-76-bromination of monoclonal antibodies using chloramine-T

Monoclonar antibody (MAb) A33 was labeled with the positron emitter Br-76 ( T-1/2 = 16.2 h). Direct labeling was done using the conventional chloramine -rr method. After optimization of the labeling conditions, a maximum yield (mean +/- max error) of 77 +/- 2% was obtained at pH 6.8. In vitro binding of Br-76-A33 to SW1222 colonic cancer cells showed that the immunoreactivit y was retained. Also, the MAbs 38S1 and 38193 and the peptide hEGF were Br- 76-labeled, resulting in labeling yields (mean + max error) of 75 +/- 3%, 6 3 +/- 4%, and 73 +/- 0.1%, respectively. We conclude that antibodies and pe ptides can be labeled conveniently with Br-76 for the purpose of whole-body tumour imaging by positron emission tomography. (C) 2000 Elsevier Science Inc. All rights reserved.