Confirmed adenocarcinoma of the prostate which has spread to other body parts

Part 1: 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

Minimum age: 18

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