Linker, antibody-drug conjugate including same and use thereof

A compound represented by Formula III, a salt or a solvate thereof,

• wherein:
• A is a targeting compound selected from antibody;
• A is coupled to the site # or ## through a S atom in the B targeting compound;
• B is an active compound selected from the group consisting of auristatin, methyl-auristatin E (MMAE), maytansine, maytansinoid, DM1, DM3, DM4, paclitaxel, calicheamicin, duocarmycin, doxorubicin, camptothecin, and pyrrolobenzodiazepine, wherein DM1, DM3 and DM4 are defined as:
• B is coupled to the site * through a N atom or O atom in the active compound;
• or B is coupled to L3 through a N atom or O atom in the active compound;
• n is a number between 0.5 and 8.5;
• R1 is a C1-6 linear or branched alkyl, and R1 is optionally mono- or multi-substituted by one or more substituents selected from the group consisting of:
• halogen and C1-4 alkoxy;
• L1 is selected from the group consisting of:
• —(CH2)m—, —(CH2)tO—, —(CH2CH2O)r—, —O—, —NH—, —S—, —S(O)—, —S(O)2—, —NCH3—, —NH(CH2)2NH—, —C(O)—, —(CH2)e—C(O)NH—(CH2CH2O)f—(CH2)g—, —(CH2)h—C(O)NH—CH[(CH2)i—NHC(O)—(CH2CH2O)—(CH2)k—CH3]—,
• q′ is 1 and q″ is 0, or q′ is 0 and q″ is 1;
• R3 is selected from the group consisting of:
• hydrogen, halogen, methyl, ethyl, nitro, methoxy, and ethoxy;
• q is 0 or 1;
• m, r, t, e, f, g, h, i, j and k are each independently selected from the group consisting of 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 and 11;
• each p is independently 0, 1, 2, 3 or 4;
• Y is an amino acid residue formed by a dipeptide selected from the group consisting of:
• Val-Cit, Val-Ala, Val-Lys, Val-Gly, Val-Thr, Val-Val, Val-Leu, Val-Ile, Val-Asn and Phe-Lys, wherein the N-terminus is connected to the carbonyl and the C-terminus is connected to the N atom;
• Z is —CH2—, —CH(CH3)— or —C(CH3)2—.