Abstract: The present invention relates to antibody- or peptide-drug conjugate compounds where one or more cryptophycin derivatives (macrocyclic depsipeptide) are covalently attached by a self-immolative linker which binds to one or more tumor-associated antigens or cell-surface receptors. The linker contains a cleavage site for proteases and a dipeptide unit able to form a diketopiperazine. These compounds may be useful in methods of diagnosis or treatment of cancer, and other diseases and disorders, such as immune or infective diseases.