Sipuleucel-T: Prototype for Development of Anti-tumor Vaccines

Prostate cancer immunotherapy officially debuted with the recent FDA approval of Sipuleucel-T. The novel trend of cancer immunotherapy relies on the identification of particular tumor-associated antigens, like prostatic acid phosphatase (PAP). Sipuleucel-T consists of autologous dendritic cells activated in vitro with recombinant fusion protein PA2024, PAP-linked to granulocyte-macrophage colony-stimulating factor. Sipuleucel-T represents a prototype for the development of cancer vaccines. Preclinical and clinical data as well as landmark studies for the existing narrow chemotherapy alternatives and early immunotherapy trials will be discussed. The pivotal trial demonstrated a 4.1-month difference of median survival, but with no effect on time to progression in asymptomatic or minimally symptomatic metastatic castrate-resistant patients. Several immunologic effects were observed in the treated population, including antibody and T cell–specific activity to P2024 and PAP. With all new therapies the extent of clinical and objective benefits versus encountered limitations should be evaluated. This review highlights the events and decisions in the process of the development of Sipuleucel-T. We discuss how this successful immunotherapy outcome challenges us to use it as a starting point for variations to or try to amplify practical anticancer progress within the antitumor vaccine paradigm.