Phase I trial of iodine-131-chimeric B72.3 (human IgG4) in metastatic colorectal cancer

R. F. Meredith, M. B. Khazaeli, W. E. Plott, M. N. Saleh, T. Liu, L. F. Allen, C. D. Russell, R. A. Orr, D. Colcher, J. Schlom, D. Shochat, R. H. Wheeler, A. F. LoBuglio

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Twelve patients with metastatic colorectal cancer participated in a Phase I trial of 131I-labeled chimeric B72.3 (human IgG4). Consecutive groups of patients received 18 mCi/m2, 27 mCi/m2 and 36 mCi/m2. No acute side effects related to antibody administration were noted. Bone marrow suppression was the only side effect; it was dose-dependent and correlated with whole-body radiation dose estimates. The lowest dose level produced no marrow suppression, whereas 27 mCi/m2 resulted in Grade 1 and 2 marrow suppression in two of three patients. The maximum tolerated dose was 36 mCi/m2 with all six patients at this dose level having at least Grade 1 and two patients with Grade 3 and 4 marrow suppression. Eight of 12 patients had radioimmune imaging of tumor sites at 5-22 days. Seven patients had an antibody response to initial infusion. On retreatment, whole-body kinetics and imaging were altered for patients with a high anti-ch-B72.3 response. Thus, chimeric B72.3 (IgG4) has limited utility as a means of delivering multiple therapeutic doses of 131I in the majority of patients; alternative strategies including second generation anti-TAG-72 monoclonal antibodies, other radioisotopes and other chimeric human isotypes will need to be pursued.

Original languageEnglish
Pages (from-to)23-29
Number of pages7
JournalJournal of Nuclear Medicine
Issue number1
Publication statusPublished - 1992
Externally publishedYes


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