This is an open-label, multicenter Phase I/II study to evaluate the safety and efficacy of single-agent AT-101 in men with hormone-refractory prostate cancer.

Inclusion Criteria:

1. Rising PSA, as defined by increasing levels on at least two consecutive assessments
2. ECOG performance status 0 or 1
3. Adequate hematologic function
4. Adequate liver and renal function
5. Able to swallow and retain oral medication.

Exclusion Criteria:

1. Received prior chemotherapy for HRPC.
2. Concurrent therapy for the treatment of prostate cancer.
3. Clinical signs or symptoms of CNS metastases
4. Requirement for corticosteroid treatment, with the exception of topical corticosteroids or inhaled corticosteroids for reactive airway disease.
5. Active secondary malignancy or history of other malignancy within the last 5 years.
6. Failure to recover from toxicities related to prior therapy.
7. Uncontrolled concurrent illness.