Dipeptides Degradable by Enzyme in Lysosome

　1, 2, 3, 4, and 5 are dipeptides containing valine (Val)-citrulline (Cit) and p-aminobenzylalcohol (PAB) moieties. It has been reported that Cathepsin B in the lysosome degrades the peptide bond between Cit-PAB.¹⁾ Therefore, a drug conjugate bound covalently with carbamate bonds between PAB and the drug can be synthesized by using the dipeptide as a linker. The drug can be then released by hydrolysis after cleavage of the peptide bond between Cit-PAB. Antibody-drug conjugates (ADCs) in which the N-terminus of Val is bound to an antibody have been developed.²⁾