A Study of JNJ-63898081 in Participants With Advanced Stage Solid Tumors

Open to people ages 18 years and up

• Histology: Part 1: Metastatic castration-resistant prostate cancer (mCRPC) with histologic confirmation of adenocarcinoma. Adenocarcinoma with small-cell or neuroendocrine features is allowed. mCRPC is defined by prostate Cancer Working Group (PCWG )3 criteria. Part 2: mCRPC as defined above or pathologically confirmed metastatic renal cell carcinoma (RCC) as defined by world health organization (WHO) 2016 Classifications
• Measurable or evaluable disease: Part 1: Either measurable or evaluable disease for prostate cancer. Part 2: At least one measurable lesion as per RECIST v1.1.
• Evidence of disease progression on prior therapy that requires a new line of treatment
• Participants with accessible lesions enrolled in selected pharmacokinetic (PK)/pharmacodynamics (PD) cohorts and in Part 2 must agree to undergo the mandatory fresh tumor biopsies, unless collection of the biopsy presents a safety risk

• Less than 2 weeks between prior anticancer treatment (including radiotherapy) discontinuation and the first dose of study drug, and toxicities have not returned to Grade less than or equal to (<=) 1 or baseline
• Prior treatment with prostate-specific membrane antigen (PSMA)-targeted therapy except for PSMA-targeted vaccine is permitted
• Solid organ or bone marrow transplantation
• Seizure or known condition that may predispose to seizure or intracranial masses
• Other active malignancy requiring systemic treatment <=12 months prior to enrollment