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

Abstract

[131 I]Metuximab injection (Licartin) was an efficient therapeutic anti-hepatocellular

carcinoma (HCC) radioimmunological agent generated by labeling 131 I with the murine

monoclonal antibody fragment HAb18-F(ab’)2 but human anti-mouse antibody (HAMA)

response in some patients after administration limited its clinical use. To reduce the

immunogenicity of murine antibody, we attempted to humanize HAb18 by variable domain

resurfacing based on the three-dimensional structure of Fv fragment. Considering the

surface accessibility of non-human like framework residues and the potential to form a

molecular hydrogen bond within the context of the homology modeled Fv of HAb18, three

residues in a single chain fragment of antibody variable region of HAb18 (HAb18scFv)

were replaced by their human counterparts. We fabricated a humanized version of

HAb18scFv, 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 was

decreased while its specificity and similar binding activity (KD = 1.5 × 10-9 M) were

retained compared with its parental antibody. In addition, this antibody is an efficient

mediator of antibody-dependent cell-mediated cytotoxicity (ADCC) and

complement-dependent cytotoxicity (CDC). These results suggest (HAb18-huscFv)2-Fc

could be a more efficient antibody fragment with less immunogenicity and additional

cytotoxicity function.