Sequence symmetric modified IgG4 bispecific antibodies

The present disclosure relates to a symmetric bispecific antibody of the class IgG4 comprising two heavy chains which each comprise a variable domain, CH1 domain and a hinge region, wherein in each heavy chain:the cysteine in the CH1 domain which forms an inter-chain disulphide bond with a cysteine in a light chain is substituted with another amino acid; andoptionally one or more of the amino acids positioned in the upper hinge region is substituted with cysteine, wherein the constant region sequence of each heavy chain is similar or identical and the variable region in each heavy chain is different, formulations comprising the same, the use of each of the above in treatment and processes for preparing said antibodies and formulations.