Radioimmunotherapy using 131I-labeled anti-CD22 monoclonal antibody (LL2) in patients with previously treated B-cell lymphomas.

Experience in using rapidly internalizing antibodies, such as the anti-CD22 antibody, for radioimmunotherapy of B-cell lymphomas is still limited. The present study was conducted to assess the efficacy and toxicity of a 131I-labeled anti-CD22 monoclonal antibody (mAb), LL2, in patients with B-cell lymphomas failing first- or second-line chemotherapy. Eligible patients were required to have measurable disease, less than 25% B cells in unseparated bone marrow, and an uptake of 99mTc-labeled LL2Fab' in at least one lymphoma lesion on immunoscintigram. Eight of nine patients examined with immunoscintigraphy were unequivocally found to have an uptake, and therapy with 131I-labeled anti-CD22 [1330 MBq/m2 (36 mCi/m2)] preceded by 20 mg of naked anti-CD22 mAb was administered. Three patients achieved partial remission (duration, 12, 3, and 2 months), and one patient with progressive lymphoma showed stable disease for 17 months. Four patients exhibited progressive disease. The toxicity was hematological. Patients with subnormal counts of neutrophils or platelets before therapy seemed to be more at risk for hematological side effects. Radioimmunotherapy in patients with B-cell lymphomas using 131I-labeled mouse anti-CD22 can induce objective remission in patients with aggressive as well as indolent lymphomas who have failed prior chemotherapy.