A liposome-encapsulated peptide vaccine consisting of a synthetic peptide derived from the mucin 1 (MUC-1) antigen with potential antineoplastic activity. Upon vaccination, emepepimut-S may stimulate the host immune system to mount a cytotoxic T lymphocyte (CTL) response against MUC-1-expressing tumor cells, resulting in growth inhibition. MUC-1 antigen is a high-molecular-weight transmembrane glycoprotein that is overexpressed on the cell surfaces of many epithelial tumor cells as well as on the cell surfaces of some B-cell lymphoma cells and multiple myeloma cells.