The purpose of this study is to evaluate the safety, pharmacokinetics (PK), and preliminary activity of GDC-1261 in participants with advanced or metastatic prostate cancer. It's also to identify a recommended dose(s) and regimen for GDC-1261 for subsequent studies.
Eastern Cooperative Oncology Group (ECOG) Performance Status of <=1
Life expectancy is >= 3 months
Histologically or cytologically confirmed prostate adenocarcinoma
Disease progression during or following the direct prior line of therapy
Treatment with any approved systemic anti-cancer therapy within 14 days or 5 drug elimination half-lives
Structurally unstable bone lesions suggest an impending fracture
Untreated central nervous system (CNS) metastases or leptomeningeal disease
Uncontrolled pain