Characterization of tumor vaccines during product development

The term tumor vaccines encompasses a wide variety of diverse agents capable of interacting with the immune system to produce local inflammation, delayed type hypersensitivity reaction and/or tumor regression and, hopefully, a therapeutic effect. These vaccines may be grouped into the following general areas: (1) Cell-based vaccines such as manipulated tumor cells, activated peripheral blood or bone marrow-derived lymphocytes, dendritic cells or other antigen presenting cells (APC) and gene-modified tumor cells or other cells engineered to express cytokines, growth factors or tumor antigens. (2) Antigen preparations, such as synthetic peptides, purified antigens and tumor cell lysates. (3) Viral and plasmid vectors expressing therapeutic genes. (4) Liposome containing antigen, peptides, plasmids encoding tumor antigens. While no tumor vaccine has been licensed by the FDA, numerous clinical trials are ongoing and some products have advanced to Phase III pivotal stages of development. However, as with many novel products, major regulatory and scientific issues associated with clinical use of tumor vaccines remain to be addressed. In this paper, we address issues associated with different types of tumor vaccines and provide recommendations for the characterization of these vaccines at various stages of development.