Linker, linker-containing antibody drug conjugate, and preparation method therefor and use thereof

A ligand-drug conjugate represented by formula II, a stereoisomer thereof, a tautomer thereof, a pharmaceutically acceptable salt thereof, a deuterated compound thereof, or a solvate thereof:

• wherein
• Ab is a ligand selected from a protein, an antibody, a polypeptide, an enzyme, and a small molecule;
• n is a number between 0.5 and 8.5;
• for example, n is a number between 0.8 and 5, a number between 1 and 4, a number between 2 and 6, a number between 3 and 7, a number between 4 and 8, a number between 3.5 and 8.5, a number between 3.5 and 4.5, or a number between 6.5 and 8.5;
• preferably, n is about 2, 3, 4, 5, 6, 7, or 8;
• more preferably, n is about 3, 4, 5, 6, 7, or 8;
• L1 is selected from
• preferably, the carbon end of L1 is linked to the N of succinimide, and the carbonyl end of L1 is linked to L2;
• m and t are each independently selected from:
• 0, 1, 2, 3, 4, 5, 6, 7, and 8;
• q is 0, 1, 2, or 3;
• p is 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15;
• X is selected from:
• CH2, O, and NH;
• L2 is absent, or is an amino acid residue, or is a peptide residue consisting of 2-10 amino acid residues;
• preferably, the amino end of L2 is linked to L1, and the carbonyl end of L2 is linked to L3;
• preferably, the amino acid includes, but is not limited to, phenylalanine (F), glycine (G), valine (V), lysine (K), serine (S), glutamic acid (E), asparagine (N), arginine (R), alanine (A), citrulline, and cysteine (C);
• L3 is absent, or is selected from
• preferably, the amino end of L3 is linked to L2, and the carbonyl end or carbon end of L3 is linked to D;
• D is a histone deacetylase inhibitor drug selected from a thiol-based histone deacetylase inhibitor, a hydroxamic acid-based histone deacetylase inhibitor, and a benzamide-based histone deacetylase inhibitor.