4. Patients whose disease is refractory (defined as evidence of disease progression while on drug or within 3 months of its discontinuation) to more than 2 lines of chemotherapy given for CRPC. Any number of chemotherapies to which the patient's disease is not refractory are allowed, as long as time on treatment did not exceed 6 months (counted from day 1 of cycle 1 to day 1 of the last cycle of treatment).