Mifamurtide (L-MTP-PE) for High-Risk Osteosarcoma

Inclusion Criteria: 1. Had signed informed consent/assent. Voluntary participation in the pharmacokinetic portion of the compassionate access protocol was included in the informed consent but not required for compassionate use participation. 2. Had diagnosis of high grade osteosarcoma with relapsed or recurrent disease, locally or metastatic, with disease not completely resectable or who were unable to complete recommended chemotherapy due to toxicity: relapse, recurrence local or metastatic; unable to have standard surgical resection; abbreviated chemotherapy regimen secondary to toxicity (e.g. hypophosphatemia from ifosfamide, cardiotoxicity from doxorubicin, renal dysfunction from methotrexate, ifosfamide, or cisplatin.) 3. Aged 2 ≤ 50 years. 4. Had adequate hematopoietic function as demonstrated by: 1) Absolute Neutrophil Count (ANC) \> 750/microL; Hemoglobin (Hb) \> 8 g/dL; Platelets \> 30,000/microL. 5. Had adequate hepatic function as documented by 1) ALT \< 2.5 x upper limit of normal (ULN) for age; 2) total bilirubin ≤ 1.5 x ULN for age. 6. Had adequate renal function as demonstrated by: 1) Creatinine clearance or radioisotope glomerular filtration rate \> 70 mL/min/1.73 m\^2; OR, 2) Serum creatinine ≤ 2x ULN for age. 7. Had absence of concurrent active acute infection (i.e., afebrile). 8. In females of child bearing potential (not menopausal for 12 months or no previous surgical sterilization), had a negative pregnancy test. All sexually active participants used an effective means of contraception. Such means included oral contraceptives, Lupron Depot, DepoProvera, and condom with diaphragm and spermicidal jelly. 9. Performance status: Lansky 50-100% (≤ 16 years of age); OR, Eastern Cooperative Oncology Group (ECOG) 0-2 or Karnofsky 50-100% (\>16 years of age). Exclusion Criteria: 1. Had chronic use of corticosteroids or other immunosuppressive agents. 2. Was pregnant or breast-feeding.