Inclusion Criteria: - Male or female subject aged ≥18 years. - Unresectable advanced or metastatic histologically proven STS. Eligibility will include desmoplastic small round cell tumor, Ewing's sarcoma, and osteosarcoma. - Subjects must have relapsed or had progressive disease following standard of care treatment with chemotherapy prior to enrollment or intolerant to prior standard of care treatment with chemotherapy due to safety issues. - Recovery from toxic effects of prior therapies to Grade 1 or better according to National Cancer Institute-Common Terminology Criteria of Adverse Events (NCI-CTCAE, Version 3). - Hematologic test results: - Hemoglobin ≥8 g/dL - Absolute neutrophil count (ANC) ≥1,500/μL - Platelet count ≥100,000/μL - Clinical chemistry test results: - If serum creatinine ≤1.5 times the upper limit of normal (ULN), or if serum creatinine is >1.5 times the ULN, then 24 hour creatinine clearance of >50 cc/min, creatine phosphokinase (CPK) ≤2.5 times the ULN - Hepatic function test results: - Total bilirubin ≤ULN, if increased then measure indirectly to rule out Gilbert's syndrome. If direct bilirubin is within normal limits, subject may be considered eligible. - Total alkaline phosphatase ≤1.5 times the ULN, or if liver metastases are present, then alkaline phosphatase may be ≤2.5 times the ULN. - AST and ALT must be ≤2.5 times the ULN. - Female subjects must be surgically sterile, abstinent, or, if sexually active, be practicing an effective method of birth control (e.g., prescription oral contraceptives, contraceptive injections, intrauterine device, double-barrier method, contraceptive patch) before entry and throughout the study, and have a negative urine or serum pregnancy test result at screening. For male subjects and partners, acceptable methods of birth control include sterilization, barrier contraception, and abstinence. - Subjects must have signed an informed consent document indicating that they understand the purpose of and procedures required for the study and are willing to participate in the study. Exclusion Criteria: - Less than 3 weeks from the last dose of radiation therapy; last dose or 4 half lives of systemic cytotoxic therapy; therapy with any investigational agent; less than 2 weeks from the last dose of radiation therapy with any investigational agent or systemic therapy, provided all side effects from those therapies have resolved to Grade 1 or less. - Active viral hepatitis or chronic liver disease. - Unstable cardiac condition, including congestive heart failure or angina pectoris, myocardial infarction within 1 year before enrollment, uncontrolled arterial hypertension or arrhythmias. - Active infection. - Female subject who is pregnant or breast-feeding.