Fig. 2

EGFR and HER2 T-BsAb heterodimerization and in vitro kinetics (A) Schematic of BsAb heterodimerization by controlled Fab Arm Exchange. Parental BsAbs bore 2 Fabs specific to EGFR or HER2 and 2 scFvs specific for CD3 (‘2 + 2’). Reduction of inter-H-chain disulfide bonds and subsequent heterodimerization (driven by F405L and K409R amino acid substitutions) yielded EGFRxHER2 BsAbs bearing 1 EGFR Fab, 1 HER2 Fab, and 2 CD3 scFv (‘1 + 1 + 2’). (B) SPR analysis of T-BsAbs binding to EGFR (left panel), HER2 (middle panel), and EGFR x HER2 (right panel) proteins. Representative normalized sensorgrams at 20nM were shown. (C) IHC staining of two cell-derived PDAC xenograft tumors SW1990 (top) and BxPC-3 (bottom). OCT-embedded tumor sections were stained with EGFRxEGFR, HER2xHER2, or EGFRxHER2 BsAbs. Control slides were either unstained (SW1990) or incubated with a control antibody (BxPC-3). (D) Antibody-dependent T cell-mediated cytotoxicity assays (ADTC) against SW1990 (left) and BxPC-3 (right). Cytotoxicity measured by Chromium-51 release. Ratio of effector T cells to target PDAC cells (E: T ratio) was set to 10:1. EC50s (SW1990; BxPC-3): EGFRxEGFR: 165.8fM; 31.5fM, HER2xHER2: 18.5pM; 7.14pM, EGFRxHER2: 699.6fM; 128.8fM. CD33xCD33 BsAb was included as a negative control