2561 BACKGROUND: 1E10 is a gamma type anti-idiotype monoclonal antibody (Ab2) that mimics the Neu-Glycolyl GM3 antigen. Ab2 is specific to an Ab1 MoAb designated as P3, which recognizes Neu-Glycolyl containing gangliosides expressed in human breast cancer (BC). METHODS: Twenty patients (pts) were enrolled in this phase I study: 16/20 with high risk BC (≥4 positive axillary lymph nodes), included after completion of adjuvant treatment, and 4/20 with metastatic BC (2 bone, 1 nodal and 1 skin). Pts were assigned at three dose level groups: 0,5 mg (7), 1 mg (6), 2 mg (7). Six intradermal injections of the vaccine (1E10 adsorbed on aluminum hydroxide adjuvant) were given at 2-week intervals (induction phase), followed by ten monthly doses until completing one year of treatment (maintenance). Those pts who completed the induction phase were evaluable for immunogenicity. RESULTS: 8 pts completed the study with no evidence of relapse or progression; 11 didn’t complete the protocol because of: progression (7), tox...