Potent immunomodulatory and antitumor effect of anti-CD20-IL2no-alpha tri-functional immunocytokine for cancer therapy.

Introduction: The anti-CD20 antibody rituximab (RTX) has substantially improved outcomes of patients with B-cell lymphomas, although more efficient therapies are needed for refractory or relapsing lymphomas. An approach to increase the clinical effectiveness of anti-tumor therapy is the use of antibody-cytokine fusion proteins (immunocytokines (ICKs)) to deliver at the tumor site the antibody effector functions and cytokines that trigger anti-tumor activities. In particular, IL-2-based ICKs have shown significant results in preclinical studies but not in clinical trials due to the toxicity profile associated to high doses IL-2 and the undesired expansion of Tregs. Methods: To improve the efficacy of RTX therapy, we fused a murine (mIgG2a) or a human (hIgG1) version of RTX to a mutated IL-2 (no-alpha mutein), which has a disrupted affinity for the high affinity IL-2 receptor (IL-2R) to prevent the stimulation of Tregs and reduce the binding to endothelial cells expressing CD25, the α chain of high affinity IL-2R. Characterization of anti-CD20-IL2no-alpha ICKs was performed by SDS-PAGE, Western-blotting and SEC-HPLC and also by several functional in vitro techniques like T-cell proliferation assays, apoptosis, CDC and ADCC assays. The in vivo activity was assessed by using murine tumor cells expressing huCD20 in C57/Bl6 mice. Results: Both ICKs exhibited similar in vitro specific activity of their IL2no-alpha mutein moieties and kept CD20-binding capacity. Anti-CD20-IL2no-alpha (hIgG1) retained antibody effector functions as complement-dependent cytotoxicity and enhanced direct apoptosis, NK cell activation and antibody-dependent cellular cytotoxicity relative to RTX. In addition, both ICKs demonstrated a higher antitumor efficacy than parental molecules or their combination in an EL4-huCD20 tumor model in immunocompetent mice. Anti-CD20-IL2no-alpha (hIgG1) strongly expanded NK and CD8+ T cells but not Tregs in tumor-bearing mice. Discussion: These findings suggest that anti-CD20-IL2no-alpha could represent an alternative treatment for B cell lymphoma patients, mainly those refractory to RTX therapy.

A rationally-engineered IL-2 improves the antitumor effect of anti-CD20 therapy.

Anti-CD20 treatment represents a therapeutic benefit for patients with B-cell lymphomas, although more efficient therapies are needed for refractory or relapsing patients. Among them, the combination of anti-CD20 and IL-2 that induces T cell response has been hampered by the expansion of FoxP3+ Tregs that strongly express the high affinity IL-2 receptor (IL-2R αßγ). We explore here the anti-tumor effect of an anti-CD20 antibody combined with a mutated IL-2 (no-alpha mutein) which has a disrupted affinity for the IL-2R αßγ. We demonstrate that anti-CD20/no-alpha mutein combination significantly augments the survival rate of mice challenged with huCD20+ cells as compared to animals treated with anti-CD20 ± IL-2. Moreover, the combination with no-alpha mutein but not IL-2 provokes an increase of granzyme B and perforin in splenic NK and CD8+ T cells, a reduction of Tregs and an increase in activated macrophages. The former combination also induces a T helper profile different from that obtained with IL-2, with an earlier polarization to Th1 and no increase in Th17. The therapeutic effect of anti-CD20/no-alpha mutein was accompanied by an expansion of peripheral central (TCM) and effector (TEM) memory CD8+ T cell compartments. Last, as opposed to IL-2, no-alpha mutein administered at the beginning of anti-CD20 treatment did not dampen the long-term protection of surviving mice after tumor rechallenge. Thus, this study shows that the combination of anti-tumor antibodies and no-alpha mutein is a promising approach to improve the therapeutic effect of these antibodies by potentiating NK/macrophage-mediated innate immunity and the adaptive T-cell response.

Antitumor and cytotoxic properties of a humanized antibody specific for the GM3(Neu5Gc) ganglioside.

Gangliosides are sialic acid-bearing glycosphingolipids expressed on all mammalian cell membranes, and participate in several cellular processes. During malignant transformation their expression changes, both at the quantitative and qualitative levels. Of particular interest is the overexpression by tumor cells of Neu5Gc-gangliosides, which are absent, or detected in trace amounts, in human normal cells. The GM3(Neu5Gc) ganglioside in particular has been detected in many human tumors, and it is considered one of the few tumor specific antigen. We previously demonstrated that a humanized antibody specific for this molecule, named 14F7hT, retained the binding and cytotoxic properties of the mouse antibody. In this work, we confirm that 14F7hT exerts a non-apoptotic cell death mechanism in vitro and shows its potent in vivo antitumor activity on a solid mouse myeloma model. Also, we demonstrate, in contrast to the murine counterpart, the capacity of this antibody to induce antibody-dependent cell-mediated cytotoxicity using human effector cells, which increases its potential for the treatment of GM3(Neu5Gc)-expressing human tumors.

Expression and biological characterization of an anti-CD20 biosimilar candidate antibody: a case study.

The CD20 molecule is a non-glycosylated protein expressed mainly on the surface of B lymphocytes. In some pathogenic B cells, it shows an increased expression, thus becoming an attractive target for diagnosis and therapy. Rituximab is a chimeric antibody that specifically recognizes the human CD20 molecule. This antibody is indicated for the treatment of non-Hodgkin lymphomas and autoimmune diseases, such as rheumatoid arthritis and systemic lupus erythematosus. In this work, we describe the stable expression and biological evaluation of an anti-CD20 biosimilar antibody. While rituximab is produced in fed-batch culture of recombinant Chinese hamster ovary (CHO) cells, our biosimilar antibody expression process consists of continuous culture of recombinant murine NS0 myeloma cells. The ability of the purified biosimilar antibody to recognize the CD20 molecule on human tumor cell lines, as well as on peripheral blood mononuclear cells from humans and primates, was demonstrated by flow cytometry. The biosimilar antibody induced complement-dependent cytotoxicity, antibody-dependent cell-mediated cytotoxicity and apoptosis on human cell lines with high expression of CD20. In addition, this antibody depleted CD20-positive B lymphocytes from peripheral blood in monkeys. These results indicate that the biological properties of the biosimilar antibody compare favorably with those of the innovator product, and that it should be evaluated in future clinical trials.

A cytotoxic humanized anti-ganglioside antibody produced in a murine cell line defective of N-glycolylated-glycoconjugates.

Gangliosides containing the N-glycolyl (NGc) form of sialic acid are tumor-associated antigens and promising candidates for cancer therapy. We previously generated the murine 14F7 monoclonal antibody (mAb), specific for the N-glycolyl-GM3 ganglioside (NGcGM3), which induced an oncosis-like type of cell death on malignant cell lines expressing this antigen and recognized breast carcinoma by immunoscintigraphy in cancer patients. As humanization is expected to enhance its use for human cancer therapy, herein we describe the design and generation of two humanized versions of the 14F7 mAb by disrupting potential human T cell epitopes on its variable region. No differences in antigen reactivity or cytotoxic properties were detected among the variants tested and with respect to the chimeric counterpart. Humanized 14F7 genes were transfected into the NGcGM3-expressing NS0 cell line. Therefore, in the industrial scaling-up of the transfectoma in serum-free medium, cell viability was lost due to the cytotoxic effect of the secreted antibody. This shortcoming was solved by knocking down the CMP-N-acetylneuraminic acid hydroxylase enzyme, thus impairing the synthesis of NGc-glycoconjugates. Humanized 14F7 mAb is of potential value for the therapy of NGcGM3-expressing tumors.

Chimeric anti-N-glycolyl-ganglioside and its anti-idiotypic MAbs: immunodominance of their variable regions.

P3 monoclonal antibody (MAb) is a murine IgM that specifically recognizes N-glycolyl (NeuGc)-gangliosides and sulfatides. It also reacts with antigens expressed in human breast tumors and melanoma. In syngeneic model, P3 MAb is able to elicit a strong anti-idiotypic (Ab2) antibody response, even in the absence of adjuvants or carrier proteins. 1E10 MAb is an anti-idiotypic antibody specific for P3 MAb that has demonstrated anti-tumoral effects in syngeneic and allogeneic animals. Here we report the construction of the human IgG(1) chimeric P3 and 1E10 antibodies, and the evaluation of the maintenance of the main properties of the murine MAbs. Chimeric P3 antibody specifically reacted with GM3(NeuGc) and GM2(NeuGc) gangliosides, and not with their acetylated variants. Also, it strongly recognized the anti-idiotypic 1E10 MAb. Chimeric 1E10 antibody specifically reacted with P3 MAb. Upon immunization of Balb/c mice with both chimeric antibodies, we were able to demonstrate the immunodominance of their variable regions. The anti-idiotypic response induced by both antibodies was strong and in most of the mice was even significantly higher than the anti-isotypic response, despite the fact that 70% of the chimeric molecule is xenogenic with respect to the animal model.

Humanization of predicted T-cell epitopes reduces the immunogenicity of chimeric antibodies: new evidence supporting a simple method.

Genetic engineering has provided several approaches to reduce immunogenicity of murine antibodies. We described previously a new method based on the humanization of the linear epitopes presented to T cells. In brief, potential immunogenic epitopes in the variable region were identified and subjected to point mutations to make them human and/or to modify amphipatic motifs. The resulting recombinant antibody retained its antigen binding affinity and was less immunogenic in monkeys than their murine or chimeric predecessors are. The present study provides two new examples of this T-cell epitope humanization approach: ior-t1A murine monoclonal antibody (mMAb), which recognizes the human-CD6 molecule, and ior-C5 mMAb, which recognizes a novel glycoprotein expressed on the surface of malignant colorectal cells. Seven amino acids were substituted in ior-C5 and eleven residues in ior-t1A, by the corresponding residues from the highest homologous human sequences. Surprisingly, the homology between re-shaped chimeric antibody variable region frameworks and human sequences was 80-90%. Experiments in monkeys showed that T1AhT and C5hT "detopes" antibodies were less immunogenic than their chimeric analogues while they retained 30-50% of antigen binding affinities. The proposed method might be of general applicability to reduce immunogenicity of chimeric antibodies with therapeutic potential.