Ibalizumab (iMab)-based biAb construction and confirmation. (A) Schematic depicting the structure of an iMab-based biAb. The variable fragments (VH and VL) of VRC01, 3BNC60, NIH45-46G54W, PGT123, PGT128 or 10E8 were tethered by a flexible glycine-serine linker to create a single-chain Fv (scFv), which was fused to the N-terminus or C-terminus of the iMab heavy chain. (B) SDS-PAGE analysis of purified VRC01-ibalizumab (01-iMab) bispecific Abs: iMab-VRC01(VH-VL) (iMab-01(HL)), VRC01(VL-VH)-iMab (01(LH)-iMab), and VRC01(VH-VL)-iMab (01(HL)-iMab). (C) 3BNC60-iMab (60-iMab) biAb. (D) PGT128-iMab (128-iMab) biAb.