CONJUGATE COMPRISING LIGAND AND CEACAM5 ANTIBODY FAB FRAGMENT

Provided is a conjugate comprising a ligand, a spacer, and a peptide linker useful for an in-vivo diagnostic drug and internal radiation therapy, using an anti-human CEACAM5 antibody Fab fragment whose binding activity is not attenuated even by labeling with a metal, a fluorescent dye, or the like. A conjugate comprising an anti-human CEACAM5 antibody Fab fragment and a ligand, the fragment comprising a heavy chain fragment including a heavy chain variable region consisting of a specific amino acid sequence and a light chain including a light chain variable region consisting of a specific amino acid sequence, or a conjugate comprising a ligand, a spacer, and a peptide linker, wherein the binding activity thereof is not attenuated even by labeling with a metal, a fluorescent dye, or the like, can be used as a diagnostic composition and/or a pharmaceutical composition.