Mutant promoting homologous pairing of heavy and light chains of multispecific antibody

The antibody or antigen-binding fragment thereof, comprising one or a plurality of first antigen-binding regions that specifically bind to a first antigen and one or a plurality of second antigen-binding regions that specifically bind to a second antigen, wherein at least one of the antigen-binding regions comprise a heavy chain CH1 and light chain CL, and comprises a disulfide bond reshaping mutation at the CH1-CL interface, wherein the disulfide bond reshaping mutation comprises T139C in CH1 and F116C in CL, wherein the first antigen-binding region and the second antigen-binding region may the same or different.

The antibody or antigen-binding fragment thereof, comprising one or a plurality of first antigen-binding regions that specifically bind to a first antigen and one or a plurality of second antigen-binding regions that specifically bind to a second antigen, wherein at least one of the antigen-binding regions comprise a heavy chain variable region and light chain variable region, an amino acid pair at the heavy chain variable and light chain variable region comprise a charge mutation that mutates the two amino acids on the amino acid pair into amino acids with opposite charges, respectively, wherein the position of the amino acid pair at the heavy chain variable region and light chain variable region interface is selected from:

• position 45 of the heavy chain variable region and position 87 of the light chain variable region, position 45 of the heavy chain variable region and position 44 of the light chain variable region, position 91 of the heavy chain variable region and position 43 of the light chain variable region, or position 91 of the heavy chain variable region and position 44 of the light chain variable region (Kabat number).