Inclusion Criteria:

• Patients ≥15 years of age with metastatic and/or unresectable sarcomas of the following histological subgroups: Bone sarcomas, such as osteosarcoma and Ewings sarcoma; Leiomyosarcoma; Liposarcomas*; Any other soft tissue sarcoma* except GIST. * Patients with well-differentiated liposarcoma or desmoid tumors must have demonstrated progressive disease within the previous 6 months.
• Presence of at least one measurable lesion that: Can be accurately measured in at least one dimension with longest diameter ≥20 mm using conventional techniques or ≥10 mm with spiral CT scan (or otherwise at least twice the reconstruction interval for CT or MRI scans).
• ECOG performance status ≤1
• Minimum life expectancy of 3 months
• Adequate renal and hepatic function, as specified in the protocol.
• Adequate bone marrow function, as specified in the protocol.
• Serum cholesterol <350 mg/dL and triglycerides < 400 mg/dL
• Male and female patients who are not surgically sterile or postmenopausal must agree to use reliable methods of birth control for the duration of the study until 30 days after the last dose of study drug
• Able to understand and give written informed consent

Exclusion Criteria:

• Women who are pregnant or lactating
• Presence of brain metastases
• Prior therapy with rapamycin, rapamycin analogues or tacrolimus
• Prior anticancer treatment (chemotherapy, radiotherapy, hormonal, immunotherapy, biological response modifiers, signal transduction inhibitors, etc) within 4 weeks prior to the first dose of AP23573
• Ongoing toxicity associated with prior anticancer therapy (except peripheral neuropathy of ≤ grade 1 by NCI toxicity criteria)
• Another primary malignancy within the past three years (except for non-melanoma skin cancer and cervical carcinoma in situ)
• Known or suspected hypersensitivity to drugs formulated with polysorbate 80 (Tween) or any other excipient contained in the study drug
• Known Grade 3 or 4 hypersensitivity to macrolide antibiotics (e.g., clarithromycin, erythromycin, azithromycin)
• Significant uncontrolled cardiovascular disease
• Active infection requiring systemic therapy
• Known HIV infection
• Treatment with any investigational agent within 4 weeks prior to the first dose of AP23573
• Concurrent treatment with immunosuppressive agents other than prescribed corticosteroids at stable doses for 2 weeks prior to first planned dose of study drug
• Inadequate recovery from any prior surgical procedure or having undergone any major surgical procedure within 2 weeks prior to the first dose of AP23573
• Presence of any other life-threatening illness or organ system dysfunction which, in the opinion of the Investigator, would either compromise the patient's safety or interfere with evaluating the safety of the study drug