This is a Phase I, multicenter, open-label, dose-escalation study of DSTP3086S administered as a single agent by intravenous (IV) infusion to patients with metastatic Castration-Resistant Prostate Cancer (CRPC).

Inclusion Criteria:

• Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2
• Life expectancy of at least 12 weeks
• Histologic documentation of adenocarcinoma of the prostate
• Surgical castration or ongoing use of gonadotropin-releasing hormone agonists with confirmed castrate levels of testosterone
• Metastatic progressive CRPC defined as progressive disease despite surgical castration or ongoing use of gonadotropin-releasing hormone agonists with confirmed castrate levels of testosterone
• For patients in the dose-expansion cohort of the study, not more than two prior lines of cytotoxic chemotherapy in the metastatic setting
• Evaluable or measurable disease
• Documented willingness to use an effective means of contraception

Exclusion Criteria:

• Anti-tumor therapy, including chemotherapy, biologic, experimental, or hormonal therapy, or radiotherapy within 4 weeks prior to Day 1, with the following exceptions: maintenance hormonal therapy for metastatic prostate cancer and palliative radiation to bone metastases within 2 weeks prior to Day 1
• Major surgical procedure within 4 weeks prior to Day 1
• Known active bacterial, viral, fungal, mycobacterial, or other infection (including HIV and atypical mycobacterial disease, but excluding fungal infections of the nail beds)
• Ongoing corticosteroid use with > 10 mg of daily prednisone or equivalent
• Symptomatic hypercalcemia requiring continued use of bisphosphonate therapy. Patients who are receiving bisphosphonate therapy specifically to prevent skeletal events and who do not have a history of clinically significant hypercalcemia are eligible.
• History of severe allergic or anaphylactic reactions to monoclonal antibody therapy (or recombinant antibody-related fusion proteins)
• Clinically significant history of liver disease, including viral or other hepatitis, current alcohol abuse, or cirrhosis
• Untreated or active central nervous system (CNS) metastases. Patients with a history of treated CNS metastases are eligible, provided that they meet all of the following criteria: evaluable or measurable disease outside the CNS, radiographic demonstration of improvement upon the completion of CNS-directed therapy and no evidence of interim progression between the completion of CNS-directed therapy and the screening radiographic study, and screening CNS radiographic study is >/= 8 weeks since completion of radiotherapy and >/= 4 weeks since the discontinuation of corticosteroids and anticonvulsants
• Dose expansion cohort (B): no prior chemotherapy is allowed