A compound of formula (I) or a pharmaceutically acceptable salt or solvate thereof is provided. In formula (I), R1, R2 and R3 are each, independently, hydrogen, amino, nitro, halogen, hydroxyl, C1-C6 alkoxy, carboxylic acid, C1-C6 alkoxycarbonyl, C1-C6 amino, C1-C6 aminocarbonyl, C1-C6 alkyl, branched C1-C6 alkyl, C1-C6 cycloalkyl, C1-C6 heterocyclic, aryl or heteroaryl, provided at least one of R1 and R3 is an amino group. A linker-drug and a ligand-drug conjugate including the compound are also provided.
