The invention relates to novel cell-binding agent-maytansinoid conjugate having a self-immolative peptide linker and more specifically to conjugates of formula (I). The invention also provides novel maytansinoid compounds of formula (II), (III), (IV) or (V). 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.