MEDI-565 itself is composed of a humanized single-chain antibody recognizing human CEA connected by a short flexible linker to a de-immunized single-chain antibody specific for CD3, and shares the characteristics of the BiTE antibody class as described above [16, 17, 18] . It specifically binds to CEA and not to other CEACAM family members [16] . Upon concurrent binding to CEA on cancer cells and CD3 on T cells, MEDI-565 mediates T cell activation and the subsequent killing of CEA-expressing target cells in a perforin-and granzyme-dependent manner that is insensitive to concentrations up to 5 mg/mL of soluble CEA [16, 17, 18] . Furthermore, intravenous and subcutaneous administration of MEDI-565 had anticancer activity in severe combined immunodeficient mouse xenograft models of various human cancers [18] ; growth inhibition of the cancers was contingent on both the presence of un-stimulated human T cells and the expression of CEA on the cancer cells [18] . MEDI-565 is currently in phase I clinical trials (clinicaltrials.gov identifier: NCT01284231) for the treatment of gastrointestinal adenocarcinomas.