This is a single-arm, open label phase II trial of the investigational agent, Ara-C (cytarabine), in patients diagnosed with hormone refractory prostate cancer whose disease has progressed on or deemed not suitable for standard chemotherapy with docetaxel. Ara-C appears to inhibit DNA synthesis and is cytotoxic to a wide variety of mammalian cells. Recent discoveries have suggested the role of gene fusions in the ETS family of transcription factors as important for the development of prostate cancer. Ara-C appears to block ETS genes, suggesting that it is worthwhile to explore Ara-C as a potential new treatment for patients with hormone refractory prostate cancer given that there is no standard of care for the proposed patient population. In this study, Ara-C will be administered intravenously for 2 days every 3 weeks (1 cycle). Treatment will be for 6 cycles if tolerated and may be continued in patients who are responding and do not have severe toxicity.

Inclusion Criteria:

• Biopsy-proven prostate cancer or clinical picture consistent with metastatic prostate cancer with high level of serum PSA (> 20ng/ml)
• At least 4 weeks after docetaxel treatment and have at least 2 consecutive rising PSAs measured at least 2 weeks apart
• Progression on or intolerance of docetaxel chemotherapy
• ECOG performance status ≤ 2
• Adequate organ and marrow function

Exclusion Criteria:

• Prior treatment with cytarabine
• Receiving any other investigational or anticancer agents
• Uncontrolled intercurrent illness
• Active malignancy at any other site excluding squamous cell or basal cell carcinomas of the skin
• Radiotherapy within the past 4 weeks