Disclosed herein are maytansinoid drug linker derivatives which can be linked to a antigen binding unit (Abu), and maytansinoid drugs linked with an antigen binding unit (Drug-Linker-Antigen binding Unit: D-L-Abu), for targeted delivery to disease tissues. D-L-Abu, D-L-Abu derivatives, and methods relating to the use of such drug conjugates to treat antigen positive cells in cancers and immunological disorders are provided.