A New Era of Immunotherapy in Prostate Cancer

Prostate cancer was one of the first cancer types where FDA (Food and Drug Administration) approval was granted to a cancer vaccine, sipuleucel-T, in the metastatic setting for asymptomatic or minimally symptomatic patients. This marked the beginning of the era of immunotherapies in cancer and stimulated the interest to develop other immune-based novel agents. In addition to sipuleucel-T vaccine, pox viral-based vaccine and personalized peptide vaccine are also being investigated in prostate cancer. Other agents that modulate the tumor microenvironment to enhance the immune response against the prostate cancer cells is also being developed. Immune checkpoint inhibitors such as ipilimumab, anti-PD-1 monoclonal antibody (programmed cell death-1), and Indoleamine 2,3-dioxygenase (IDO) inhibitors have shown some promise in this field. However, similar to sipuleucel-T vaccine, the preliminary data reflects the efficacy of these to be limited to mCRPC patients with favorable risk factors without any visceral disease. More clinical trials are needed to identify the group of patients with mCRPC that would benefit from immunotherapy. In this article we review the role of immune-based therapies including vaccines and immune checkpoint inhibitors in mCRPC. Keywords: Castration resistant prostate cancer, sipuleucel-T, PROSTVAC-VF, personalized peptide vaccines, ipilimumab, Cytotoxic T-Lymphocyte Antigen-4 (CTLA-4) inhibitor, Indoleamine 2, 3-dioxygenase (IDO), PD-1 targeted immunotherapy.