Antibody-drug conjugate having cyclic benzylidene acetal linker

An antibody-drug conjugate having a cyclic benzylidene acetal linker represented by formula (1) or formula (2):

• wherein, in the formula (1) and the formula (2), Y is an antibody;
• D is a drug;
• R1 and R6 are each independently a hydrogen atom or a hydrocarbon group;
• R2, R3, R4 and R5 are each independently an electron-withdrawing or electron-donating substituent or a hydrogen atom;
• s is 1 or 2, t is 0 or 1, and s+t is 1 or 2;
• w is an integer of 1 to 20;
• and each of Z1 and Z2 is a divalent spacer composed of a structural unit independently selected from an ether group, an ester group, a carbonate group, a urethane group, an amide group, a thioether group, a disulfide group, a 1H-1,2,3-triazole-1,4-diyl group, a secondary amino group, an aliphatic hydrocarbon group containing any of these groups, or an aliphatic hydrocarbon group;
• or each of Z1 and Z2 is a divalent spacer composed of two identical structural units selected from an ether group, an ester group, a carbonate group, a urethane group, an amide group, a thioether group, a disulfide group, a 1H-1,2,3-triazole-1,4-diyl group, a secondary amino group or an aliphatic hydrocarbon group containing any of these groups.