Camptothecin compound and conjugate thereof

A compound represented by structural formula II or a pharmaceutically acceptable salt, stereoisomer, solvate or prodrug thereof:

• in structural formula II, R5 is C1-5 alkyl or C1-5 alkyl substituted with one or more substituents, C3-6 cycloalkyl, or C3-6 cycloalkyl substituted with one or more substituents, phenyl or substituted phenyl;
• G is hydrogen, halogen, methyl, or methoxy;
• X is oxygen or sulfur;
• n=0 or 1;
• when X is oxygen, G is hydrogen, and n=0, R5 is not n-butyl.

A compound represented by structural formula III or a pharmaceutically acceptable salt, stereoisomer, solvate or prodrug thereof:

• in structural formula III, E is selected from the group consisting of the following groups, in which means the bonding site to M:
• M is phenylene or phenylene substituted with one or more substituents, or a chemical bond;
• and in the substituted phenylene, the phenylene is substituted with substituent(s) selected from the group consisting of alkyl, haloalkyl, alkoxy, halogen, ester, amide, and cyano;
• and preferably, M is halogen-substituted phenylene;
• SP1 is selected from the group consisting of C1-8 alkylene, C1-8 cycloalkylene, or C1-21 linear heteroalkylene comprising 1-11 heteroatoms selected from the group consisting of N, O, and S, in which the C1-8 alkylene, C1-8 cycloalkylene, and C1-21 linear heteroalkylene independently of one another are optionally substituted with one or more substituents selected from the group consisting of hydroxyl, amino, sulfonic acid group, and cyano;
• SP2 is selected from the group consisting of —NH(CH2CH2O)aCH2CH2CO—, —NH(CH2CH2O)aCH2CO—, —S(CH2)aCO—, or a chemical bond, in which a is an integer in the range of 1 to 20, preferably an integer in the range of 1 to 10, more preferably an integer in the range of 1 to 6;
• A means a peptide group of 2 to 4 amino acids;
• CPT is a compound of camptothecins.