REVIEW Cancer Immunotherapy With Peptide-Based Vaccines: What Have We Achieved? Where Are We Going?

Many human tumor-associated antigens (TAAs) have re-cently been identified and molecularly characterized. When bound to major histocompatibility complex molecules, TAA peptides are recognized by T cells. Clinical studies have therefore been initiated to assess the therapeutic potential of active immunization or vaccination with TAA peptides in patients with metastatic cancer. So far, only a limited num-ber of TAA peptides, mostly those recognized by CD8+ T cells in melanoma patients, have been clinically tested. In some clinical trials, partial or complete tumor regression was observed in approximately 10%–30 % of patients. No serious side effects have been reported. The clinical responses, how-ever, were often not associated with a detectable T-cell-specific antitumor immune response when patients ’ T cells were evaluated in ex vivo assays. In this review, we analyz