Format of bispecific antibodies (BsAbs)-Hetero H, forced HL IgG1

Hetero H, forced HL IgG1/ DuetMab replaces the native disulfide bond in the CH1-CL interface with an engineered disulfide bond (fig. 1). This enhances cognate light chain pairing. Three different positions in the CH1-CL interface are possible candidates for favoring the formation of a novel disulfide bond. An amino acid on the HC and one on the LC is replaced with cysteine in one of the Fab regions. The native disulfide bond on the other Fab region is left intact. It is advantageous that the modifications are in the CH1-CL interface and not in the variable domain, as this could have detrimental effects on antigen binding. Although, engineering in the CH1-CL interface could mean that κ and λ constant light chains would somehow affect the usefulness of this approach. However, it was shown to be compatible to both isotypes (Mazor et al. 2015). DuetMab could be generically applied to bispecific antibodies in development since the approach: (i) does not contain variable domain engineering, (ii) is compatible with both kappa and lambda isotypes and (iii) was able to induce correct heterodimerization.