Cytotoxic conjugates comprising a cell binding agent and a cytotoxic agent,therapeuticcompositions comprising the conjugate, methods for using the conjugates in theinhibition of cell growth and the treatment of disease, and a kit comprisingthe cytotoxicconjugate are disclosed are all embodiments of the invention. In particular,the cellbinding agent is a monoclonal antibody, and epitope-binding fragments thereof,thatrecognizes and binds the CA6 glycotope. The present invention is also directedtohumanized or resurfaced versions of DS6, an anti-CA6 murine monoclonalantibody, andepitope-binding fragments thereof. The humanized versions of the DS6monoclonalantibody binds the tumour antigen CA6, which is a sialoglycotope on mucinreceptorMuc 1 . The cytotoxic conjugates may be a humanized antibody linked to acytotoxicagent, wherein the cytotoxic agent may be a maytansinoid, a taxane, or anothercytotoxiccompound.
