Study testing of pbi-shRNA™ EWS/FLI1 Type 1 LPX will involve patients (≥age 8) with advanced Ewing's sarcoma. The first 3 subjects enrolled onto the study as well as the first subject enrolled into each dose cohort must be 16 years of age or older. pbi-shRNA™ EWS/FLI1 Type 1 LPX will be given via intravenous infusion twice a week for 4 weeks (e.g. Mon and Thurs, preferred) for a total of 8 infusions of the product per cycle followed by a 2 week washout period. Patients will be accrued in 3-patient dose escalation cohorts using the following escalation schema (50% to 33% to 25% to 25% to 25%) at a starting IV dose of 0.04 mg/kg.