A Study of JNJ-78278343, a T-Cell-Redirecting Agent Targeting Human Kallikrein 2 (KLK2), for Advanced Prostate Cancer

Inclusion Criteria

• Inclusion Criteria: - 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 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