A Study of JNJ-69086420, an Actinium-225-Labeled Antibody Targeting Human Kallikrein-2 (hK2) for Advanced Prostate Cancer

Inclusion Criteria:

Histologic: metastatic castration-resistant prostate cancer (mCRPC) with histologic confirmation of adenocarcinoma. Adenocarcinoma with small-cell or neuroendocrine features is allowed
Must have had prior exposure to at least one novel androgen receptor (AR) targeted therapy (example, abiraterone acetate, enzalutamide, apalutamide, darolutamide); prior taxane or other chemotherapy is acceptable but not required
Treatment with other agents for prostate cancer, if received, must have been discontinued greater than or equal to (>=) 2 weeks prior to first dose of study drug.
Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1
Adequate organ functions as reflected in laboratory parameters

Exclusion Criteria:

Part 1: Prior treatment with radium Xofigo (Ra 223 dichloride), strontium, or samarium therapy or radioconjugate therapy
Known history of myelodysplastic syndrome, leukemia, or hematological malignancy with features suggestive of myelodysplastic syndrome/acute myeloid leukemia at any timepoint
Toxicity from prior anticancer therapy has not resolved to baseline levels or to Grade less than or equal to <= 1 (except alopecia, radiation tissue fibrosis, or peripheral neuropathy)
Known allergies, hypersensitivity, or intolerance to JNJ-69086420 or its excipients and protein therapeutics
Active or chronic hepatitis B or hepatitis C infection.