Human Monoclonal Antibodies to Sialyl-Lewisa (CA19.9) with Potent CDC, ADCC, and Antitumor Activity

Abstract

Purpose: The carbohydrate antigen sialyl-Lewis a (sLe a ), also known as CA19.9, is widely expressed on epithelial tumors of the gastrointestinal tract and breast and on small-cell lung cancers. Since overexpression of sLe a appears to be a key event in invasion and metastasis of many tumors and results in susceptibility to antibody-mediated lysis, sLe a is an attractive molecular target for tumor therapy. Experimental Design: We generated and characterized fully human monoclonal antibodies (mAb) from blood lymphocytes from individuals immunized with a sLe a -KLH vaccine. Results: Several mAbs were selected based on ELISA and FACS including two mAbs with high affinity for sLe a (5B1 and 7E3, binding affinities 0.14 and 0.04 nmol/L, respectively) and further characterized. Both antibodies were specific for Neu5Aca2-3Galb1-3(Fuca1-4)GlcNAcb as determined by glycan array analysis. Complement-dependent cytotoxicity against DMS-79 cells was higher (EC 50 0.1 mg/mL vs. 1.7 mg/mL) for r7E3 (IgM) than for r5B1 (IgG1). In addition, r5B1 antibodies showed high level of antibodydependent cell-mediated cytotoxicity activity on DMS-79 cells with human NK cells or peripheral blood mononuclear cells. To evaluate in vivo efficacy, the antibodies were tested in a xenograft model with Colo205 tumor cells engrafted into SCID (severe combined immunodeficient mice) mice. Treatment during the first 21 days with four doses of r5B1 (100 mg per dose) doubled the median survival time to 207 days, and three of five animals survived with six doses. Conclusion: On the basis of the potential of sLe a as a target for immune attack and their affinity, specificity, and effector functions, 5B1and 7E3 may have clinical utility.

Monoclonal Antibodies Targeting LecLex-Related Glycans with Potent Antitumor Activity

“…More recently, human SLe a mAbs were produced using a patient vaccination strategy that showed specific binding to SLe a and exhibited ADCC, CDC, and antitumor activity in a xenograft model (21).…”

“…No studies, to date, have shown tumor eradication of 10-day established tumors and liver metastases. SC104 inhibited tumor growth in vivo, but was more effective in the tumor prevention model and only worked in the therapeutic models in combination with 5-FU/leucovorin (21). The humanized SC104 (NCT01447732) currently in phase I/II trials (SC104/CEP-37250/KHK2804) has been defucosylated for enhanced effector functions.…”

A murine–human chimeric IgG antibody against vascular endothelial growth factor receptor 2 inhibits angiogenesis in vitro

“…The Fc region was consequently converted from murine IgG2a to human IgG1. Fc region of human IgG1 can enhance FccRIII-mediated antibody-dependent cell-mediated cytotoxicity (ADCC) and complement dependent cytotoxicity (CDC), and can be the most suitable for therapeutic use against pathogen and cancer cells (Sawada et al 2011). The effect of ADCC and CDC of the 2F12 antibody on hepatocellular carcinoma cells needs to be further confirmed.…”

Selecting an Optimal Antibody for Antibody- Drug Conjugate Therapy

“…Conjugates of protein toxins to anti-IgG secondary reagents have been reported, either chemical conjugates to ricin A (Till et al 1988) or pokeweed antiviral protein (Weltman et al 1987) or genetic fusions of Pseudomonas exotoxin A to an antikappa single-domain antibody (Kellner et al 2011) or to the Z domain of Staphylococcus protein A (Mazor et al 2007). Commercially available secondary antibodies conjugated to the ribosome-inactivating protein saporin have been widely used to confirm antibody internalization (Kohls and Lappi 2000;Nguyen et al 2006;Fransson and Borrebaeck 2009;Sawada et al 2011). Antibodies can be incubated with saporin-conjugated antimouse, antirat, or antihuman reagents and then incubated with tumor cells for 3-4 days.…”