Characterization of a New Humanized Anti-CD20 Monoclonal Antibody, IMMU-106, and Its Use in Combination with the Humanized Anti-CD22 Antibody, Epratuzumab, for the Therapy of Non-Hodgkin’s Lymphoma

Abstract

Purpose: A new humanized anti-CD20 monoclonal antibody (MAb), IMMU-106, was evaluated to elucidate its action as an antilymphoma therapeutic, as a single agent, and in combination with the anti-CD22 MAb, epratuzumab.Experimental Design: Antiproliferative effects, apoptotic effects, and the ability of IMMU-106 to mediate complement-mediated cytotoxicity and antibody-dependent cellular cytotoxicity on a panel of non-Hodgkin's lymphoma (NHL) cell lines were compared with the chimeric anti-CD20 MAb, rituximab, and evaluated in light of the various levels of antigen expression by the cell lines. In vivo therapy studies were performed in SCID mice bearing disseminated Raji lymphoma.Results: The mechanisms of cytotoxicity of IMMU-106 were found to be similar to rituximab, and include direct apoptosis, antibody-dependent cellular cytotoxicity, and complement-mediated cytotoxicity. IMMU-106 was also found to be very similar to rituximab in terms of antigenbinding specificity, binding avidity, and dissociation constant. Treatment of Raji-bearing SCID mice with IMMU-106 yielded median survival increases of up to 4.2-fold compared with control mice. Survival in mice treated with IMMU-106 plus epratuzumab was compared with IMMU-106 treatment alone. Although the combined treatment did not improve median survival, an increased proportion of long-term survivors was observed. An enhanced antiproliferative effect was also observed in vitro in SU-DHL-6 cells when IMMU-106 was combined with epratuzumab. These findings are consistent with the up-regulation of CD22 expression observed after pretreatment of NHL cells in vitro with CD20 MAb (IMMU-106).Conclusions: It is expected that in humans IMMU-106 should be at least as effective as rituximab and, due to its human framework construction, it may exhibit different pharmacokinetic, toxicity, and therapy profiles. In addition, it may be possible to enhance efficacy by combination therapy comprised of anti-CD20 and other B-cell lineage targeting MAbs, such as epratuzumab. The current results emphasize that in vitro as well as in vivo studies with many of the NHL cell lines were generally predictive of the known activity of anti-CD20 MAbs in NHL patients, as well as the enhanced efficacy of epratuzumab combined with rituximab observed in early clinical trials.

Preclinical and clinical evaluation of epratuzumab (anti-CD22 IgG) in B-cell malignancies

“…Based in part on preclinical work suggesting that epratuzumab can enhance anti-tumor effects of anti-CD20 antibodies (Nitschke et al, 1997;Stein et al, 2004), clinical trials have been conducted to evaluate it in combination with rituximab. The first of these assessed epratuzumab 360 mg/m 2 and rituximab 375 mg/m 2 , each administered weekly for four consecutive weeks in patients with recurrent indolent (n ¼ 16, 15 with follicular) and aggressive (n ¼ 7, all DLBCL) NHL (Strauss et al, 2006).…”

“…Several second-generation CD20 monoclonal antibodies currently are in development and clinical testing, including a fully human MAb (Teeling et al, 2004) and a humanized form (Stein et al, 2004) in trials in patients with B-cell malignancies (Morschhauser et al, 2005). Initial results with these compounds suggest that they are well tolerated and can induce responses in various lymphoma subtypes.…”

Improved therapy of non-Hodgkin's lymphoma xenografts using radionuclides pretargeted with a new anti-CD20 bispecific antibody

“…Earlier studies have shown the antitumor effects afforded by the unlabeled IMMU-106 IgG, but at higher doses than used in this report. 11 The lack of human CD20 on the normal B cells of nude mice does not allow an assessment of conditions that might be required to optimize targeting when there is a substantial antigen sink, such as in patients where normal B cells also express the antigen. Interestingly, the initial clinical studies using a streptavidin-biotin-pretargeting systems in NHL reported good targeting, but they did not investigate the potential need for predosing patients with an anti-CD20 antibody to improve the targeting of the subsequently administered radiolabeled biotin.…”

“…The humanized anti-CD20 IgG 1 , IMMU-106, 11 and the 1,4,7,10-tetraazacyclododecane-N,N 0 ,N 00 ,N 000 -tetracetic acid (DOTA)-di-HSG hapten-peptide 9 (Supplementary data online Figure 1S) were provided by Immunomedics Inc. (Morris Plains, NJ, USA), and the murine anti-679 anti-histamine-succinylglycine peptide (HSG) antibody 8 Schematic representation of the bispecific antibody-pretargeting procedure. The bispecific antibody is a chemical conjugate composed of the Fab 0 of the IMMU-106 humanized anti-CD20 monoclonal antibody and Fab 011 of a murine antibody (m679) specific for the hapten, HSG.…”

“…Recently, we reported the development of a humanized anti-CD20 antibody that has similar antitumor activity as rituximab both in vitro and in NHL xenograft models. 11 The purpose of this investigation was to assess whether a pretargeting procedure based on a chemically conjugated bsMAb prepared from this humanized anti-CD20 antibody fused with the previously reported anti-peptide-hapten antibody would have a therapeutic advantage over the directly radiolabeled anti-CD20 IgG in an animal model for human NHL.…”