Radiolabeled antibody conjugates have been prepared with monoclonal antibodies that are reactive with the lymphoid differentiation antigens CD5, CD20, and CD22 and the Lym-1 antigen. Only the 131I-labeled Lym-1 and the 90Y-labeled anti-CD5-radiolabeled conjugates have been tested in CLL (Table 2). One B-CLL patient was treated with 90Y-T101 anti-CD5 murine antibody and had a partial response lasting 6 mo (66). Five of five CLL patients receiving a series of injections up to 300 mCi cumulative dose of 131I-Lym 1 antibody had remissions lasting an average of 6 mo (67). Thus, CLL appears to respond to radiolabeled conjugates, but none of the patients treated to date have shown durable complete remissions. The 131I-labeled LL2 anti-CD22 antibody, the 90Y-labeled ibritumomab anti-CD20 antibody, the 131I-labeled tositumomab anti-CD20 antibody, and the 67Cu-labeled Lym-1 antibody have been tested and have shown clinical activity in non-Hodgkin's lymphomas but have not been used for CLL patients (68-71). Radiolabeled antibodies deserve further testing in CLL.
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