RADIOIMMUNOTHERAPY OF B-CELL LYMPHOMAS WITH I-131-LABELED LL2 (EPB-2) MONOCLONAL-ANTIBODY

LL2, or EPB-2, is a new monoclonal antibody (MAb) that shows specificity for non-Hodgkin's B-cell lymphomas (NHL). In a series of 5 evaluable therapy patients, doses as low as 30 mCi I-131-labeled LL2 IgG or F(ab')2 resulted in tumor responses (2 partial remissions, 2 mixed and minor responses, and 1 no response), while one patient given diagnostic doses showed a partial remission for 1 year, followed by a complete remission after a second low dose. Only myelotoxicity was found at therapeutic doses. Dosimetry estimates revealed spleen and tumor doses of a mean of 4.6 cGy/mCi, which was 3- to 4-fold the. dose to other organs. Imaging indicated that 82% of 60 known extrasplenic lymphoma sites could be detected with the I-131-labeled LL2 MAb. Using a new Tc-99m-Fab' imaging kit of LL2, 3 lymphoma patients were studied, and known sites of lymphoma could be disclosed at the 1 mg Fab' dose.