The invention relates to novel cell-binding agent-cytotoxic agent conjugate having a peptide linkers and more specifically to conjugates of formula (I). The invention also provides novel cytotoxic agents of formula (II), linker compounds represented by formula (III), and drug-linker compounds represented by formula (IV). The invention further provides compositions and methods useful for inhibiting abnormal cell growth or treating a proliferative disorder in a mammal using the compounds or conjugates of the invention.