Ewing's sarcoma characterized by the t(11; 22) (q24; q12) translocation at several but prioritized breakpoint sites, resulting in the EWS/FLI1 fusion gene is the second most frequently diagnosed primary malignant bone tumor in the US with an annual incidence, from birth to age 20, of 2.9 cases per million population. The survival rate for patients with high-risk recurrent disease (relapse < 2 years) is < 10% at 5 years. Moreover, of patients who progress after second line treatment, eighty percent do not achieve a second complete response and of these patients < 10% survive one year. Refractory patients to both frontline and second line therapy have even worse prognosis. The EWS/FLI1 gene is well known as the driver gene of Ewing's sarcoma. We designed a novel pbi-shRNA™ EWS/FLI1 Type 1 LPX which has demonstrated sufficient specificity, safety and efficacy in animal testing to justify Phase I testing. Clinical safety (no ≥ grade 3 product related toxic effect) and target specific activity has been observed with other bi-shRNA products involving 147 cancer patients (698 separate dose administrations) (BB-Investigational New Drug (IND) 14205; BB-IND 14938). Moreover, safety has been observed with IV delivery of pbi-shRNA™ EWS/FLI1 Type 1 LPX in murine and swine testing via multidose IV administration.