A novel antibody fragment targeting HAb18G/CD147 with cytotoxicity and decreased immunogenicity

Abstract

[131 I]Metuximab injection (Licartin) was an efficient therapeutic anti-hepatocellularcarcinoma (HCC) radioimmunological agent generated by labeling 131 I with the murinemonoclonal antibody fragment HAb18-F(ab’)2 but human anti-mouse antibody (HAMA)response in some patients after administration limited its clinical use. To reduce theimmunogenicity of murine antibody, we attempted to humanize HAb18 by variable domainresurfacing based on the three-dimensional structure of Fv fragment. Considering thesurface accessibility of non-human like framework residues and the potential to form amolecular hydrogen bond within the context of the homology modeled Fv of HAb18, threeresidues in a single chain fragment of antibody variable region of HAb18 (HAb18scFv)were replaced by their human counterparts. We fabricated a humanized version ofHAb18scFv, HAb18-huscFv, to the human IgG1 Fc fragment to form (HAb18-huscFv)2-Fc.The reactivity of (HAb18-huscFv)2-Fc to the serum of patients with HAMA response wasdecreased while its specificity and similar binding activity (KD = 1.5 × 10-9 M) wereretained compared with its parental antibody. In addition, this antibody is an efficientmediator of antibody-dependent cell-mediated cytotoxicity (ADCC) andcomplement-dependent cytotoxicity (CDC). These results suggest (HAb18-huscFv)2-Fccould be a more efficient antibody fragment with less immunogenicity and additionalcytotoxicity function.