An immunotherapeutic agent composed of a fusion protein containing the human melanoma-associated antigen MAGE-A3 fused to a lipidated protein D derived from Haemophilus influenzae and combined with the immunoadjuvant AS15, with potential immunostimulating and antineoplastic activities. Upon intramuscular (IM) administration, GSK 2132231A may stimulate a specific cytotoxic T-lymphocyte (CTL) response against MAGE-A3-expressing tumor cells, resulting in tumor cell death. MAGE-A3, a tumor-associated antigen, is upregulated in a variety of cancer cell types. This fusion protein may boost antitumoral immune responses. AS15, a liposomal formulation containing the immunostimulating compounds CpG 7909, 3-O-desacyl-4'-monophosphoryl lipid A (MPL), and QS-21, increases the immune response against MAGE-A3-expressing tumors.