Induction of multiple anti-c-erbB-2 specificities accompanies a classical idiotypic cascade following 2B1 bispecific monoclonal antibody treatment

Abstract

The bispecific monoclonal antibody (bsmAb) 2B1, targeting the extracellular domain of c-erbB-2, the protein product of the HER-2/neu proto-ocogene, and Fc gamma RIII (CD16), expressed by human natural killer cells, neutrophils and differentiated monocytes, mediates the specific cytotoxic activity of these effector cells to tumor cells. A group of 24 patients with c-erbB-2-overexpressing tumors were treated with intravenously administered 2B1 in a phase I clinical trial and followed after treatment to evaluate the diversity and extent of the 2B1-induced humoral immune responses. As expected, 17 of 24 patients developed human anti-(murine Ig) antibodies (HAMA) to whole 2B1 IgG in a range from 100 ng/ml to more than 50000 ng/ml; 10 of these patients (42%) had strong (at least 1000 ng/ml) HAMA responses, some of which were still detectable at day 191. These responses were usually associated with similar reactivity to the F(ab')2 fragments of the parental antibodies 520C9 (anti-c-erbB-2) and 3G8 (anti-CD16). We sought evidence of an idiotypic cascade induction, indicating a prolonged specific treatment-induced effect on at least one selected target of 2B1. Using competition-based enzyme-linked immunosorbent assays, specific anti-idiotypic antibodies (Ab2) were detectable against 520C9 in 11 patients and against 3G8 in 13 patients. Peak anti-idiotypic antibodies generally occurred 3-5 weeks from treatment initiation, with a downward trend thereafter. There was a statistically significant correlation among the induction of significant HAMA responses, anti-idiotypic antibody production and the development of antibodies to c-erbB-2. The anti-c-erbB-2 responses, which were distinct from anti-anti-idiotypic (Ab3) antibodies, were detected in the post-treatment sera of 6/16 patients examined. No obvious correlation could be made between the development of humoral immune responses, the dose received, and the clinical response. Future investigation involving 2B1 therapy will concentrate on investigating an association of these humoral responses to any c-erbB-2-specific cellular responses. Manipulations of 2B1 therapy effects that augment immunity to c-erbB-2 could provide additional avenues for immunotherapy with this and other bispecific antibodies.

New approaches to antibody therapy

“…While Rituximab can be safely administered at doses of 375 mg/m 2 per dose, the maximally-tolerated dose of 2B1 is only 1 mg/m 2 per dose. 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).…”

Bispecific Minibodies Targeting HER2/neu and CD16 Exhibit Improved Tumor Lysis When Placed in a Divalent Tumor Antigen Binding Format

“…Therapy with this antibody led to occasional clinical responses and induced the development of host anti-HER2/neu antibodies and T-cell responses directed against both the extracellular and intracellular domains of HER2/neu. This phenomenon of Fc receptor-targeted immunization is best explained by bispecific antibody promotion of tumor lysis, with subsequent antigen presentation (42).…”

Increasing the Affinity for Tumor Antigen Enhances Bispecific Antibody Cytotoxicity

“…It has been previously shown that the bispecific mAb 2B1 had significant clinical toxicities due to the simultaneous cellular engagement of its Fc domain and the anti-Fc␥RIII arm of this Ab (25,34). The Bsab we describe here lack the Fc domain and hence preclude Bsab-directed leukocyte activation until cross-linking occurs through Bsab bound to the tumor Ag.…”