Linker containing arylnitro, antibody-drug conjugate containing linker and use of linker

A compound represented by Formula II or a salt thereof,

• wherein:
• R1 is hydrogen, methyl, ethyl, n-propyl or isopropyl;
• R2 is hydrogen, methyl, ethyl, n-propyl or isopropyl;
• R4 is
• and in
• the two carbonyl groups are located on the same side of the C═C double bond, which is a cis structure, R11 is a C1-6 linear or branched alkyl, and R11 is optionally mono- or multi-substituted by one or more substituents selected from the group consisting of:
• halogen and C1-4 alkoxy;
• X is oxygen atom (O), nitrogen atom (N) or sulfur atom (S);
• Ar is aryl, heteroaryl, aryl-fused-heterocyclyl or heteroaryl-fused-heterocyclyl;
• R5 is hydrogen, methyl, ethyl, n-propyl, isopropyl, fluorine, chlorine, bromine, iodine, hydroxyl or cyano;
• R6 is hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, fluorine, chlorine, bromine, iodine, hydroxyl, nitro or cyano;
• R7 is hydrogen, methyl, ethyl, n-propyl or isopropyl;
• R8 is hydrogen, methyl, ethyl, n-propyl or isopropyl;
• q is 0, 1, 2 or 3;
• p is 0, 1, 2 or 3;
• L is —(CH2)iO(CH2)j—, —(CH2)i—(CH2)j—C(O)—, —(CH2)i—C(O)NH—(CH2)j—, —(CH2CH2O)i—(CH2)j—C(O)—, —(CH2)i—(CH2CH2O)j—C(O)—, —(OCH2CH2)i—, —(CH2)m—, —(CH2)r—C(O)—, —(CH2)k—C(O)NH—(CH2CH2O)g—(CH2)h—C(O)—, —(CH2)b—C(O)NH—CH[(CH2)d—NHC(O)—(CH2CH2O)e—(CH2)f—CH3]—,
• W represents a linking group, and is —NH—CH2—C(O)—NH—, —NH—CH2—CH2—C(O)—NH—, —C(O)—NH—, —NH—C(O)—, —O—, —S—, —NH—, —N(CH3)—, —C(O)— or —NH—CH(R10)—C(O)—NH—, further preferably —NH—CH2—C(O)—NH—, —C(O)—NH—, —NH—C(O)— or —O—;
• R10 is —H, —CH3, —C3H6, —CH—(CH3)2, —CH2—CH(CH3)2, —CH(CH3)—CH2—CH3, —CH2—C6H5, —C8NH6, —CH2—C6H4—OH, —CH2—COOH, —CH2—CONH2, —(CH2)2—COOH, —(CH2)4—NH2, —(CH2)2—CONH2, —(CH2)—S—CH3, —CH2—OH, —CH(CH3)—OH or —CH2—SH;
• m is 1, 2, 3, 4, 5, 6, 7, 8 or 9;
• each i is independently 1, 2, 3, 4, 5, 6, 7, 8 or 9;
• each j is independently 1, 2, 3, 4, 5, 6, 7, 8 or 9;
• r is 1, 2, 3, 4, 5, 6, 7, 8 or 9;
• k is 1, 2, 3, 4, 5 or 6;
• g is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12;
• h is 1, 2, 3, 4, 5 or 6;
• b is 1, 2, 3, 4, 5 or 6;
• d is 1, 2, 3, 4, 5 or 6;
• e is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12;
• f is 1, 2, 3, 4, 5 or 6;
• B is an active compound, selected from the group consisting of drug, cytotoxin, detection reagent, diagnostic reagent and targeting carrier;
• B is coupled to the site* or site** through a N atom or O atom in the active compound molecule;
• t is 0 or 1.

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

• wherein:
• R1 is hydrogen, methyl, ethyl, n-propyl or isopropyl;
• R2 is hydrogen, methyl, ethyl, n-propyl or isopropyl;
• X is oxygen atom (O), nitrogen atom (N) or sulfur atom (S);
• Ar is aryl, heteroaryl, aryl-fused-heterocyclyl or heteroaryl-fused-heterocyclyl;
• R6 is hydrogen, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, fluorine, chlorine, bromine, iodine, hydroxyl, nitro or cyano;
• R7 is hydrogen, methyl, ethyl, n-propyl or isopropyl;
• R8 is hydrogen, methyl, ethyl, n-propyl or isopropyl;
• q is 0, 1, 2 or 3;
• p is 0, 1, 2 or 3;
• L is —(CH2)iO(CH2)j—, —(CH2)iO(CH2)j—C(O)—, —(CH2)i—C(O)NH—(CH2)j—, —(CH2CH2O)i—(CH2)j—C(O)—, —(CH2)i—(CH2CH2O)j—C(O)—, —(OCH2CH2)i—, —(CH2)m—, —(CH2)r—C(O)—, —(CH2)k—C(O)NH—(CH2CH2O)g—(CH2)h—C(O)—, —(CH2)b—C(O)NH—CH[(CH2)d—NHC(O)—(CH2CH2O)e—(CH2)f—CH3]—,
• W represents a linking group, and is —NH—CH2—C(O)—NH—, —NH—CH2—CH2—C(O)—NH—, —C(O)—NH—, —NH—C(O)—, —O—, —S—, —NH—, —N(CH3)—, —C(O)— or —NH—CH(R10)—C(O)—NH—, further preferably —NH—CH2—C(O)—NH—, —C(O)—NH—, —NH—C(O)— or —O—;
• R10 is —H, —CH3, —C3H6, —CH—(CH3)2, —CH2—CH(CH3)2, —CH(CH3)—CH2—CH3, —CH2—C6H5, —C8NH6, —CH2—C6H4—OH, —CH2—COOH, —CH2—CONH2, —(CH2)2—COOH, —(CH2)4—NH2, —(CH2)2—CONH2, —(CH2)—S—CH3, —CH2—OH, —CH(CH3)—OH or —CH2—SH, preferably;
• m is 1, 2, 3, 4, 5, 6, 7, 8 or 9;
• each i is independently 1, 2, 3, 4, 5, 6, 7, 8 or 9;
• each j is independently 1, 2, 3, 4, 5, 6, 7, 8 or 9;
• r is 1, 2, 3, 4, 5, 6, 7, 8 or 9;
• k is 1, 2, 3, 4, 5 or 6;
• g is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12;
• h is 1, 2, 3, 4, 5 or 6;
• b is 1, 2, 3, 4, 5 or 6;
• d is 1, 2, 3, 4, 5 or 6;
• e is 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12;
• f is 1, 2, 3, 4, 5 or 6;
• B is an active compound, selected from the group consisting of drug, cytotoxin, detection reagent, diagnostic reagent and targeting carrier;
• B is coupled to the site* or site** through a N atom or O atom in the active compound molecule;
• t is 0 or 1;
• A is a targeting compound, selected from the group consisting of:
• protein, antibody, polypeptide, enzyme and small molecule;
• n is a number between 0.5 and 8.5.