Carcinoembryonic antigen expression of resurgent human colon carcinoma after treatment with therapeutic doses of 90Y-alpha-carcinoembryonic antigen monoclonal antibody

We have previously shown that the colon carcinoma (LS174T) xenografts that emerged shortly after radioimmunotherapy with 90Y-labeled anti-CEA monoclonal antibody (MAb) ZCE025 lacked significant expression of CEA in comparison with the untreated tumors. The present study was designed to establish if the immunophenotype of the treated tumors was the result of CEA specific therapy and if the effect was permanent. Athymic mice bearing LS174T tumors were treated either with 120 mu Ci of 90Y-ZCE025, an equal dose of 90Y-96.5 (nonspecific MAb), or received no treatment. When the treated tumors grew to approximately 1.5 cm in diameter (6 weeks after therapy), they were resected and aliquoted to be transplanted to other mice, plated in tissue culture, fixed in formalin, and homogenized for CEA quantitation. The procedure was repeated 3 times (a total of 4 months after treatment). The CEA content was evaluated 2 and 6 weeks after therapy and when the tumors were transplanted. We confirmed a 4-fold decrease of CEA in the resurgent tumors 6 weeks after specific 90Y-ZCE025 therapy, which was twice the decrease experienced by the tumors treated with nonspecific 90Y-96.5, indicating substantial and specific killing of CEA-expressing cells. The CEA content slowly but progressively increased with each new pass of the tumor in the mice, reaching approximately one-half the value of the controls at the end of the study. The resurgent tumors were also studied by immunohistochemistry with MAbs detecting different epitopes of CEA, keratin, TAG-72, and epithelial membrane antigen to evaluate possible additional immunophenotypic changes induced by radioimmunotherapy. Only the expression of TAG-72 (recognized by MAb B72.3) increased immediately after therapy, but it returned to the original levels by the end of the study. These results suggest that: (a) specific radioimmunotherapy with 90Y-ZCE025 selectively kills cells that express higher levels of CEA; (b) the immunophenotype of the surviving fraction of the tumor appears to slowly revert to its original form; and (c) other tumor markers unrelated to CEA can also be affected. These observations have important implications for the design of radioimmunotherapy trials.     

Treatment of acute graft-versus-host disease with a nonmitogenic anti-CD3 monoclonal antibody.

Treatment with the monoclonal antibody OKT3 specific for the CD3 complex associated with the T cell antigen receptor can reverse acute rejection of human renal allografts. However, efficacy of anti-CD3 antibodies for treatment of patients with acute graft-versus-host disease after marrow transplantation has not been established. The dose-limiting side effects resulting from T cell activation induced by some anti-CD3 antibodies in vivo have discouraged their use for this application. We now report a phase I-II study of GVHD treatment with the anti-CD3 antibody BC3, a monoclonal murine IgG2b that, unlike OKT3, does not activate T cells. Fourteen patients were treated with BC3 after progression of acute GVHD despite treatment with cyclosporine and corticosteroids, and three patients received BC3 as primary treatment for GVHD. BC3 was administered at a dose of 0.1 or 0.2 mg/kg/day for seven or eight days. Five patients achieved complete resolution of GVHD, eight patients had partial improvement, two patients had no change, and two patients had progression of GVHD on therapy. Responses were sustained in 8 of 13 patients. Mild chills, fever, hypertension, and chest discomfort occurred in various combinations following 6 of 17 (35%) initial infusions of BC3 and following 4 of 99 (4%) subsequent infusions. In each instance it was possible to continue BC3 therapy without adjusting the dose or treatment schedule. In each patient treated, the absolute count of peripheral blood lymphocytes decreased transiently but returned to baseline within 22 hr after the first infusion. Circulating T cells had surface CD3 molecules saturated by the infused antibody in all but one patient. Four patients survived longer than one year after treatment with antibody BC3, and 13 patients died of infection or organ failure. Administration of the nonmitogenic anti-CD3 antibody BC3 was associated with improvement in the clinical manifestations of GVHD with minimal acute toxicity. Efficacy of antibody treatment did not depend on depletion of circulating T cells. Therefore, antibody BC3 may be achieving therapeutic immunosuppression by modulating T cell function. Controlled studies in patients treated earlier in the course of GVHD should determine whether antibody BC3 can improve survival.