Bispecific antibody targeting MSLN and 4-1BB and application thereof

The invention discloses a bispecific antibody targeting MSLN and 4-1BB and an application of the bispecific antibody. The target bispecific antibody provided by the invention contains an MSLN antigen binding domain (namely a nano antibody variable region, CDR1, CDR2 and CDR3 are sequentially shown as the 484-491 < th > site, the 509-515 < th > site and the 554-565 < th > site in SEQ ID No.5) and a 4-1BB antigen binding domain (CDR1, CDR2 and CDR3 in a heavy chain variable region are sequentially shown as the 31-35 < th > site, the 50-65 < th > site and the 98-106 < th > site in SEQ ID No.5); cDR1, CDR2 and CDR3 in a light chain variable region are sequentially shown as the 24 < th > to 34 < th >, the 50 < th > to 56 < th > and the 89 < th > to 97 < th > in SEQ ID No.7). The bispecific antibody provided by the invention has a good T cell activation effect, and shows a good in-vitro tumor cell killing effect and an in-vivo tumor inhibition effect on the basis of the T cell activation effect, so that the bispeci