Current landscape of immunotherapy clinical trials in prostate cancer

Purpose The number of immunotherapies that have been approved in recent years has generated a lot of enthusiasm in the field of oncology. This success has come on the results of approvals for immunotherapy drugs and the expansion of indications for a variety of hematological and solid malignancies. However, very few immunotherapies have demonstrated improved overall survival in treating patients with prostate cancer. This is due to several factors including tumor heterogeneity, limited prostate tumor-associated antigens, and an immunosuppressive environment. Despite these challenges, numerous clinical trial efforts are ongoing to determine outcomes of immunotherapies in prostate cancer, and many are in the context of combination strategies. The purpose of this project was to identify and categorize the current landscape of immunotherapies that are in clinical trials for prostate cancer. Methods An extensive evaluation of the all currently registered clinical trials in the United States of immunotherapies in the setting of prostate cancer was performed utilizing www.clinicaltrials.gov on 1-20-18. The following search parameters were used: Condition/disease: “prostate cancer” Other terms: “immunotherapy”, “CAR-T cell therapy”, “monoclonal antibody”, “checkpoint inhibitors”, and “vaccine”. Results The query resulted in a total of 215 registered clinical trials. Most of these trials (84%) were in the context of vaccine therapy against prostate cancer, 12% of trials involved checkpoint inhibitors, and 4% were testing CAR-T cell therapy. Only 6% of the trials were in the phase 3 setting while 32% and 60% were in phase I or phase II, respectively (the remainder were not categorized into a phase). The majority of these trials used combination strategies. Conclusion The slow-growing nature of prostate cancer in many patients makes this cancer uniquely suitable for utilizing immunotherapies that may need time to allow for an immune response to mount against cancer cells. There is a tremendous amount of clinical trials that are currently being performed on prostate cancer with a variety of immunotherapeutic strategies. Although more research needs to be done, the potential of a durable and sustained response with immunotherapies is encouraging in the setting of prostate cancer.