Monoclonal antibodies against the Thy 1.1 differentiation antigen are ineffective in the treatment of transplanted AKR T-cell lymphoma once a palpable tumor nodule is present, due to the inability of the host to eliminate antibody-coated tumor cells. To overcome this limitation, we have evaluated the use of 131I-labeled anti-thy 1.1 antibodies for the therapy of established AKR/J SL2 lymphoma (Thy 1.1+) nodules growing in congeneic AKR/Cu mice (Thy 1.2+). In these experiments, 131-anti-Thy 1.1 antibody specifically localized to a s.c. tumor with a mean of 6.5% of the infused dose per g of tumor at 24 h after infusion. The proportion of infused anti-Thy 1.1 antibody localizing to tumor was constant following antibody doses of up to 400 μg/animal. Antibody iodinated with up to 2 atoms of iodine per antibody of molecule maintained binding activity and localization to tumor equivalent to antibody labeled with less iodine. The concentations of 131I-anti-Thy 1.1 in tumor would result in delivery of a mean of 1600 cGy to tumor following infusion of 500 μCi of 131I-labeled anti-thy 1.1 antibody. In comparison, 500 μCi 131I-labeled irrelevant antibody would deliver a mean of 380 cGy to tumor. Treatment of animals with palpable tumor nodules with 500 μCi 131I-labeled anti-thy 1.1 led to regression of the tumor nodule in 44% of animals, significantly prolonged survival, and cured two of five of the animals treated prior to the development of metastatic disease. In contrast, unlabeled anti-Thy 1.1 led to tumor response in 6% of animals, and up to 1000 μCi 131I-labeled irrelevant antibody had no effect on tumor growth. Therapy was limited by the emergence of variant tumor cells lacking the target antigen and by bone marrow toxicity following 131I-labeled antibody doses of ≥ 1000 μCi/animal. These studies demonstrate that 131I-labeled monoclonal antibodies can have a significant antitumor effect in a situation where unmodified antibody is ineffective.
|Original language||English (US)|
|Number of pages||9|
|Publication status||Published - 1985|
ASJC Scopus subject areas
- Cancer Research