Anti-CD3-based bispecific antibody designed for therapy of human B-cell malignancy can induce T-cell activation by antigen-dependent and antigen-independent mechanisms

Abstract

Anti‐CD3 × anti‐B‐cell antigen bispecific monoclonal antibodies (bsAbs) can redirect T‐cell‐mediated lysis toward malignant B cells. Clinical trials with CD3‐based bsAbs have shown toxicity in patients which is likely related to non‐specific T‐cell activation and targeting. Our current studies were designed to explore the mechanisms responsible for the observed in vivo toxicity by evaluating the immunologic effects of 2 different bsAb preparations in vitro. 1D10 was used as the tumor specific arm of the bsAbs. This antibody reacts with a variant of HLA‐DR found on a majority of pre‐B‐ and B‐cell malignancies, and normal B cells in some individuals. Anti‐CD3 served as the T‐cell specific arm. A 1D10 × anti‐CD3 bispecific IgG (bsIgG) produced using the hybrid‐hybridoma method was compared to a 1D10 × anti‐CD3 bispecific F(ab′)2 [bsF(ab′)2] produced using the leucine zipper technique. In cytotoxicity assays, both bsIgG and bsF(ab′)2 induced lysis by pre‐activated T cells of 1D10 (+) malignant B cells. bsIgG at high concentrations also induced lysis of 1D10 (−) tumor cells, while bsF(ab′)2 did not. Proliferation of T cells induced by bsIgG and bsF(ab′)2 was also evaluated. Both forms of bsAbs induced T‐cell proliferation in the presence of antigen (+) Raji cells, while only bsIgG did so in the presence of antigen (−) malignant B cells. bsF(ab′)2 induced T‐cell activation in the absence of any tumor cells when testing was performed on samples where the 1D10 target antigen was present on normal peripheral blood B cells. We conclude that non‐specific T‐cell activation from bsAbs can occur in an antigen‐independent manner due to the Fc/Fc receptor (FcR) interaction, or in an antigen‐dependent manner when antigen is expressed on normal or tumor cells. Both mechanisms may have been responsible for the toxicity observed in prior clinical studies. Int. J. Cancer77:251–256, 1998. © 1998 Wiley‐Liss, Inc.

Multiformat T‐Cell‐Engaging Bispecific Antibodies Targeting Human Breast Cancers

“…Overall, our findings demonstrate that bsAb constructs containing the CD3 binding domain and a functional Fc domain can specifically crosslink T cells with FcR-positive immune cells, resulting in the activation of T cells in an antigen-independent manner. This observation is consistent with previous preclinical reports [34;35] , including safety data from a clinical trial with ertumaxomab, an IgG-version bsAb with a functional Fc domain, in which nearly all the patients developed symptoms of CRS [36] . Nonetheless, the reduced nonspecific activity of Tetra-IgG (Fc null) suggests that a mutational approach can potentially improve the safety of IgG-like bsAbs.…”

New approaches to antibody therapy

“…Some tumor in®ltration by leukocytes has been seen following MDX-210 therapy (Link et al, 1998), and we have observed the induction of tumor in®ltration by leukocytes in several patients treated with 2B1. However, there is no consistent, profound leukocyte in®ltration of tumor following BsAb therapy, and preclinical data suggest that BsAb promoted cytotoxicity will require eector to target ratios of at least 1 : 1 for successful therapy (Weiner et al, 1993b).…”

“…2B1-promoted antigen presentation led to the induction of anti-HER2/neu antibodies, but only in patients treated with 2B1 doses exceeding the ultimate MTD (Clark et al, 1997). Taken together, these results indicate that whole IgG BsAb targeting eector cell trigger molecules are unsuitable therapeutic structures, in accord with predictions in selected preclinical murine models (Link et al, 1998). The engagement of T cell receptor V b chains and MHC Class II by the bacterial superantigen, staphylococcal enterotoxin A (SEA), also leads to profound leukocyte activation and the attendant dose-limiting toxicity of a multi-speci®c fusion protein consisting of an anti-tumor Fab fragment and SEA (Giantonio et al, 1997;Alpaugh et al, 1998).…”

Generation of MANAbodies specific to HLA-restricted epitopes encoded by somatically mutated genes

“…The relative lack of specificity currently presents a major obstacle for the wider implementation of powerful immunotherapeutic agents such as chimeric antigen receptors and bispecific antibodies (57)(58)(59)(60). In this context, specific somatic mutations that alter the encoded proteins of cancer driver genes represent biochemical features that distinguish cancer cells from normal cells in unparalleled fashion.…”