Tasquinimod in the treatment of castrate-resistant prostate cancer - current status and future prospects.

Treatment options have significantly expanded in recent years for men with metastatic castration-resistant prostate cancer (mCRPC), with the routine use of immunotherapy (sipuleucel-T) and novel hormonal agents such as enzalutamide and abiraterone acetate prior to taxane-based chemotherapy or radium-223 radiotherapy. A number of immune checkpoints limit the immune response of the host to metastatic tumor progression in prostate cancer, one of which is an immunosuppressive and pro-angiogenic cell called the myeloid-derived suppressor cell (MDSC). Tasquinimod is a small molecular oral inhibitor of S100A9, a key cell surface regulator of MDSC function, and has shown anti-angiogenic, antitumor and immune-modulatory properties in preclinical models of prostate cancer and other solid tumors. A large randomized phase II trial of tasquinimod in men with chemotherapy-naïve mCRPC demonstrated a significant prolongation in radiographic and symptomatic progression-free survival compared with placebo, which was also associated with improvements in overall survival. Tasquinimod was studied in a global phase III randomized trial in men with bone mCRPC and, while it significantly improved radiographic progression-free survival, this did not result in an overall survival benefit. However, tasquinimod is under evaluation as well as a combination therapy with other systemic agents in prostate cancer and as a single agent in other solid tumors. This review encompasses the preclinical and clinical development of tasquinimod as a therapy for men with prostate cancer.