Novel monoclonal antibodies that specifically bind to KAAG1 are described. In some embodiments, the antibodies block the biological activity of KAAG1 and are useful in composition in certain cancers, more particularly in cancers that have increased cell surface expression of KAAG1, such as ovarian, renal, lung, colorectal, breast, brain, and prostate cancer, as well as melanoma. The invention also relates to cells expressing the monoclonal antibodies and antigen binding fragments such as humanized and chimeric antibodies. Additionally, methods of detecting and treating cancer using the antibodies and fragments are also disclosed.
