This expanded access protocol will allow access to treatment with L-MTP-PE for people with osteosarcoma. L-MTP-PE is an investigational drug that has not been approved by the FDA to treat any condition, including osteosarcoma. L-MTP-PE works by activating certain types of white blood cells, and these active white blood cells help the immune system kill cancer cells.

Inclusion Criteria:

• Confirmed diagnosis of osteosarcoma of any age Note: Patients with either newly diagnosed or relapsed osteosarcoma are eligible.

• Surgical resection or other definitive local control therapy of all clinically detectable sites of osteosarcoma

• L-MTP-PE is deemed to be of potential benefit by the treating investigator

• Willing and able to understand and sign informed consent and assent as appropriate

• Life expectancy > 6 weeks

• Adequate organ function as follows:

• Adequate bone marrow function defined as:

  • absolute neutrophil count (ANC) ≥ 750/mm^3
  • platelet count ≥ 30,000/ mm^3
  • hemoglobin ≥ 8 g/dl

• Adequate renal function defined as:

  • Creatinine clearance or radioisotope glomerular filtration rate ≥ 70 mL/min/1.73m^2 OR
  • Serum creatinine ≤ 2x the upper limit of normal based on age/gender

• Adequate liver function defined as:

  • Bilirubin (sum of conjugated + unconjugated) ≤ 2x upper limit of normal for age or ≤ 4x upper limit of normal if thought to have Gilbert's disease
  • AST or ALT ≤ 3x upper limit of normal or ≤ 5x upper limit of normal for patients with liver metastases

• Willing to use a barrier method of contraception throughout the course of the study and for 1 year after participation if relevant

Exclusion Criteria:

• Use of chronic steroids of other immunosuppressive agents
• Pregnant or breast feeding