Discloses an antibody-drug conjugate of the formula: Ab-(LU-D)p or a pharmaceutically acceptable salt thereof wherein； (a) Ab is an anti-5T4 antibody or antigen binding portion thereof, comprising: (i) a VH CDR1 region as shown in SEQ ID NO: 5, (ii) a VH CDR2 region as shown in SEQ ID NO: 6, (iii) a VH CDR3 region as shown in SEQ ID NO: 7, (iv) a VL CDR1 region as shown in SEQ ID NO: 8, (v) a VL CDR2 region as shown in SEQ ID NO: 9, and (vi) a VL CDR3 region as shown in SEQ ID NO: 10, (b) LU is a maleimidocaproyl linker unit, (c) p is an integer from 1 to 8, and (d) D is a Drug unit selected from the group consisting of monomethylauristatin E (MMAE) and monomethylauristatin F (MMAF)； wherein the sequences are as defined in the complete specification.
