A T-cell-engaging B7-H4/CD3-bispecific Fab-scFv Antibody Targets Human Breast Cancer.

PURPOSE

The B7 homolog 4 (B7-H4, ) is an immune checkpoint molecule that negatively regulates immune responses and is known to be overexpressed in many human cancers. Previously, we generated a mouse anti-human B7-H4 mAb that did not have a significant antitumor effect probably because of molecule instability. In this study, we designed a B7-H4/CD3-bispecific antibody (BsAb) and investigated its antitumor activity and using a humanized mouse model.

EXPERIMENTAL DESIGN

cDNAs of the antibody-binding fragment (Fab)-single-chain variable fragment (scFv) and scFv-scFv of the anti-B7-H4/CD3 BsAb were synthesized, and the BsAb antibodies were produced in HEK293 cells. The antitumor activity against human breast cancer cells by human peripheral blood mononuclear cells (hPBMC) with BsAb was measured by lactate dehydrogenase release and using hPBMC-transplanted MHC class I- and class II-deficient NOG mice.

RESULTS

hPBMCs with anti-B7-H4/CD3 BsAbs successfully lysed the human breast cancer cell line MDA-MB-468 (EC: 0.2 ng/mL) and other B7-H4 cell lines . When BsAb was injected in a humanized mouse model, there was an immediate and strong antitumor activity against MDA-MB-468, HCC-1954, and HCC-1569 tumors and CD8 and granzyme B CTL infiltration into the tumor, and there were no adverse effects after long-term observation. CD8 T-cell depletion by an anti-CD8 antibody mostly reduced the antitumor effect of BsAb .

CONCLUSIONS

An anti-B7-H4/CD3 BsAb may be a good therapeutic tool for patients with B7-H4 breast cancers.