Format of bispecific antibodies (BsAbs)-Controlled Fab arm exchange

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Controlled Fab arm exchange (cFAE) has proven to be a generic and versatile technology for the efficient generation of IgG-like bispecific antibodies (DuoBodies or DBs). This involves the recombination of antigen-binding arms (heavy chain–light chain (H-L) pairs) between individually expressed antibody molecules and is termed Fab-arm exchange, can be modified to make the routine generation of bsAbs feasible. The production of DuoBodies involves (i) separate expression and purification of two parental IgG1s containing two matching point mutations, one in either IgG1, at the CH3:CH3 interface, (ii) mixing of the parental IgGs; (iii) controlled reduction of interchain disulfide bonds in vitro, allowing the recombination of H-L pairs (driven by the matching mutations); and (iv) removal of reducing agent, allowing the reoxidation of interchain disulfide bonds to occur. Fragment-based formats are compatible with well-characterized and cost-effective prokaryotic and lower eukaryotic expression systems, offering the potential advantages of high yields.

Formats of bispecific antibodies (BsAbs)

Many formats have been developed for BsAb generation as listed in the following table.

Format	Description	Example BsAb	Trademark	Company
tandem VHH	Tandem VHH fragment-based BsAb	N/A
tandem scFv	Tandem ScFv fragment-based BsAb	AMG330	BiTE^TM	Amgen
Dual-affinity re-targeting antibody	Tandem domain-exchanged Fv (can also be used to fuse with Fc domain to create whole Abs)	Flotetuzumab	DART^TM	Macrogenics
Diabody	dimer of single-chain Fv (scFv) fragment	vixtimotamab	ReSTORE^TM	Amphivena Therapeutics
(scFv)2-Fab	a Fab domain and two scFv domains bind	A-337	ITab^TM	Generon/EVIVE Biotech
Rat–mouse hybrid IgG	Full-size IgG-like half antibodies from two different species	Catumaxomab	Triomab^TM	Trion Pharma
Hetero heavy chain, Common light chain	Hetero heavy chain, Common light chain	Emicizumab	ART-Ig^TM	Genentech/ Chugai/Roche
Controlled Fab arm exchange	Recombin the parental half antibodies	JNJ-64007957	Duobody^TM	Genmab/ Janssen
Hetero H, forced HL IgG1	KIH technology for heterodimerization of 2 distinct H chains, replacing the native disulfide bond in one of the CH1-CL interfaces with an engineered disulfide bond to enhance the cognate of H and L paring	MEDI5752	DuetMab^TM	MedImmune/ AstraZeneca
cH IgG1	Identical heavy chains; 2 different light chains: one kappa (κ) and one lambda (λ)	NI-1701	κλ body^TM	Novimmune SA
Hetero H, CrossMab	KIH technology; domain crossover of immunoglobulin domains in the Fab region	Vanucizumab	CrossMab^TM	Roche
scFv-Fab IgG	Fab-Fc; ScFv-Fc	Vibecotamab; M802	Xmab^TM (the engineered Fc to enhance the generation of heterodimeric Fc); YBODY^TM	Xencor/Amgen; YZYBio
VH1-VH2-CH1-Fc1(G1) x VL2-VL1-CL-Fc2(G1)	2 binding motif in one half antibody	SAR440234	CODV-Ig^TM	Sanofi
VL1-CL1-VH2-CH2-Fc x VH1-CH1 x VL2-CL2	2 binding motif in one half antibody	EMB-01	FIT-Ig^TM	EPIMAB BIOTHERAPEUTICS
VH-1-TCR Cα x VL-1-TCR Cβ; VH-2-CH-2-Fc x VL-2-CL-2	KIH technology; TCR Cα/Cβ is used to substitute the CH1 and CL domain in one arm		WuXibody^TM	WuXi Biologics
C-terminal linker of Fc	Link the other molecules at the C-terminal of Fc	APVO442	ADAPTIR-FLEX^TM	Aptevo Therapeutics
Fc antigen binding site	2 natural binding sites; 2 additional binding sites in the Fc loop	FS118	mAb²	F-star Therapeutics