Pilot Study of PLX3397 in Patients With Advanced Castration-Resistant Prostate Cancer (CRPC)

Inclusion Criteria: * Histologically confirmed prostate cancer, currently with objective progressive disease. * Castrate level of testosterone (\<50 ng/dL). * Baseline circulating tumor cell (CTC) count ≥10/7.5 mL blood. * Archival tumor tissue (unstained sections, paraffin block, or frozen tumor tissue) has been requisitioned for shipment to the central laboratory. * Karnofsky performance status of 80-100. * Adequate organ and marrow function. Exclusion Criteria: * The subject has received: * Any systemic chemotherapy (including investigational agents) within 4 weeks (with the exception of nitrosoureas/mitomycin C within 6 weeks), of the first dose of study treatment, OR * Biological agents (antibodies, immune modulators, cytokines, or vaccines) within 6 weeks of the first dose of study treatment, OR * Hormonal anticancer therapy (not including LHRH agonists or antagonists) within 2 weeks before the first dose of study treatment. Specific restrictions on prior hormonal and other anticancer treatments are detailed in inclusion criterion, OR * Small-molecular kinase inhibitors or any other type of investigational agent within 4 weeks before the first dose of study treatment or 5 half-lives of the compound or active metabolite, whichever is shorter. * The subject has received drugs used to control loss of bone mass (e.g., bisphosphonates) within 4 weeks prior to the first dose of study treatment. * The subject has symptomatic or uncontrolled brain metastasis or epidural disease requiring current treatment including steroids and anti-convulsants. * The subject has a corrected QT interval calculated by the Fridericia formula (QTcF) \>450 ms at screening. * The subject has uncontrolled or significant intercurrent illness including, but not limited to, the following conditions: * Cardiovascular disorders such as symptomatic congestive heart failure (CHF), \*Uncontrolled hypertension * Unstable angina pectoris, clinically-significant cardiac arrhythmias * History of stroke (including transient ischemic attack \[TIA\] or other ischemic event) within 6 months of study treatment * Myocardial infarction within 6 months of study treatment * History of thromboembolic event requiring therapeutic anticoagulation within 6 months of study treatment or main portal vein or vena cava thrombosis or occlusion.