Alteration of interleukin 2 (IL-2) pharmacokinetics and function by IL-2 antibodies induced after treatment of colorectal carcinoma patients with a combination of monoclonal antibody 17-1A, granulocyte macrophage colony-stimulating factor, and IL-2

In this study, we have assessed the development of neutralizing and non-neu tralizing interleukin 2 (IL-2) antibodies in metastatic colorectal carcinom a patients receiving a colon carcinoma reactive monoclonal antibody (17-1A) in combination with granulocyte macrophage colony-stimulating factor and I L-2 therapy, Before treatment, no IL-2 antibodies were detected in any of t he patients. After therapy, 10 of the 19 patients tested developed antibodi es that bound to the IL-2 product used for therapy, but only one developed antibodies that neutralized the biological activity of IL-2 as assessed usi ng an in vitro bioassay, We found that the induction of IL-2 antibodies in some patients irrespective of their neutralizing potential had a significan t impact on IL-2 pharmacokinetics, A significant reduction of the area unde r the concentration-time curve and maximum concentration (C,,,) and increas ed IL-2 distribution and clearance were observed in IL-2 antibody-positive patients in comparison with IL-2 antibody-negative patients. A significant decrease in IL-2-mediated expansion of lymphocytes was also evident in pati ents positive for IL-2 antibodies in comparison with those negative for the se antibodies. Further characterization of sera from patients with antibodi es showed that, in most cases, the antibodies recognized different IL-2 pre parations. Results also showed that serum IL-2 concentration at initiation of therapy in patients was significantly higher relative to healthy control donors. The endogenous production of IL-2 gradually increased during the t reatment cycles. To conclude, induction of neutralizing and non-neutralizin g antibodies in cytokine-treated patients should be carefully monitored in terms of their clinical significance.