COMbination of Bipolar Androgen Therapy and Nivolumab

The trial will enroll up to 44 participants (45 were enrolled because the last two patients consented at two sites simultaneously). Eligible participants will continue on androgen ablative therapy with a GnRH analogue (i.e. Zoladex, Trelstar, Eligard, or Lupron) if they have not undergone orchiectomy. Following enrollment, participants will receive an intramuscular injection of testosterone cypionate 400mg every 4 weeks for a lead-in period of 12 weeks. After the lead-in period, all participants will be treated with nivolumab 480mg IV every 4 weeks and maintained on testosterone cypionate 400mg IM every 4 weeks. Assessments for response to testosterone + nivolumab will be performed approximately every 3 months. Treatment \[with a minimum drug exposure of 12 weeks\] will be continued until PSA progression (Prostate Cancer Working Group 3 \[PCWG3\] criteria) or clinical/radiographic progression (whichever comes first), or until unmanageable toxicity requiring drug cessation.