mAbs have emerged as a promising strategy for the treatment of
cancer. However, in several
malignancies, no effective antitumor mAbs are yet available. Identifying therapeutic mAbs that recognize common
tumor antigens could render the treatment widely applicable. Here, a human
single-chain variable fragment (scFv) antibody library was sequentially affinity selected against a panel of human
cancer cell lines and an
antibody fragment (named MS5) that bound to solid and
blood cancer cells was identified. The MS5 scFv was fused to the human
IgG1 Fc domain to generate an antibody (MS5-Fc fusion) that induced antibody-dependent cellular cytotoxicity and phagocytosis of
cancer cells by macrophages. In addition, the MS5-Fc antibody bound to primary
leukemia cells and induced antibody-dependent cellular cytotoxicity. In the majority of analyzed
cancer cells, the MS5-Fc antibody induced cell surface redistribution of the receptor complexes, but not internalization, thus maximizing the accessibility of the
IgG1 Fc domain to immune effector cells. In vitro stability studies showed that the MS5-Fc antibody was stable after 6 d of incubation in human serum, retaining ∼60% of its initial intact form. After
intravenous injections, the antibody localized into
tumor tissues and inhibited the growth of 3 different human
tumor xenografts (breast,
lymphoma, and
leukemia). These antitumor effects were associated with
tumor infiltration by macrophages and NK cells. In the Ramos
B-cell lymphoma xenograft model, the MS5-Fc antibody exhibited a comparable antitumor effect as
rituximab, a chimeric anti-CD20
IgG1 mAb. These results indicate that human
antibodies with pan-
cancer abilities can be generated from phage display libraries, and that the engineered MS5-Fc antibody could be an attractive agent for further clinical investigation.-Sioud, M., Westby, P., Vasovic, V., Fløisand, Y., Peng, Q. Development of a new high-affinity human antibody with antitumor activity against solid and blood
malignancies.