Inclusion Criteria:  Confirmed adenocarcinoma of the prostate which has spread to other body parts Prior treatment with at least 1 prior novel androgen receptor (AR)-targeted therapy or chemotherapy Measurable or evaluable disease Concurrent use of any other anticancer treatment must be discontinued for at least 2 weeks before the first dose of study drug Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 Prior surgical removal of testicles; or, for participants who have not undergone surgical removal of testicles, must be receiving ongoing androgen deprivation therapy (ADT) with a gonadotropin releasing hormone analog  Exclusion Criteria:  Disease conditions  Active central nervous system (CNS) involvement Toxicity related to prior anticancer therapy has not adequately recovered  Prior/Concomitant Therapy  Prior treatment with human kallikrein (KLK) 2-targeted therapy Received, or are receiving, medications that suppress the immune system within 3 days prior to the first dose of study drug Received or plans to receive any live, attenuated vaccine within 4 weeks prior to the first dose of study drug  Prior/Concurrent Medical Conditions  Diagnosis of cancer other than prostate cancer within 2 years prior to the first dose of study drug Solid organ or bone marrow transplantation Major clotting diseases within one month prior to the first dose of study drug Active autoimmune disease within 12 months prior to the first dose of study drug Active infection Major diseases of heart and blood vessels within 6 months prior to the first dose of study drug Clinically significant lung diseases Active or chronic hepatitis B or hepatitis C infection Known positive test result for human immunodeficiency virus (unless stable on antiretroviral therapy with undetectable viral load) Any serious underlying medical conditions or other issue that would impair the ability of the participant to receive or tolerate the planned treatment