A Phase 3, Randomized, Double-blind, Placebo-controlled Study For Subjects With Locally-advanced Unresectable or Metastatic Synovial Sarcoma (V943-003, IMDZ-04-1702)

Inclusion Criteria

• Histological diagnosis of synovial sarcoma
• Immunohistochemistry (IHC) results from tumor biopsy for New York esophageal squamous cell carcinoma 1 (NY-ESO-1) are positive
• Participants have received at least 4 but no more than 8 cycles of first-line anthracycline or ifosfamide-containing systemic anti-cancer therapy regimen
• Must have documentation of no evidence of disease progression of the tumor during or after completion of first line systemic anti-cancer therapy
• ECOG (Eastern Cooperative Oncology Group) performance status of 0 or 1
• Age >/= 12 years
• Life expectancy of at least 6 months Selected

Exclusion Criteria

• Have received last dose of first-line systemic anti-cancer therapy or date of most recent local regional therapy >28 days prior to day 1
• Have received prior anti-NY-ESO-1 therapy
• Have received first-line systemic anti-cancer therapy with an agent other than anthracycline or ifosfamide
• Have received treatment with systemic immunomodulatory agents within 28 days prior to administration of the first dose of CMB305, or 5 half-lives of the drug, whichever occurs sooner.
• Have significant immunosuppression from concurrent, recent, or anticipated need for chronic treatment with systemic immunosuppressive dose of corticosteroids or immunosuppressive medications.
• Have psychiatric or other medical illness, or any other condition that in the opinion of the investigator prevents compliance with the study procedures or ability to provide valid informed consent.
• Have history of uncontrolled autoimmune disease.
• Have a significant electrocardiogram finding or cardiovascular disease
• have inadequate organ function per protocol
• History of other cancer within 3 years
• Evidence of active tuberculosis or recent clinically-significant infection requiring systemic therapy.
• Evidence of active Hepatitis B, Hepatitis C, or Human Immunodeficiency virus (HIV) infection
• Have a history of brain metastasis
• Have received cancer therapies including chemotherapy, radiation, biologic, or kinase inhibitors, granulocyte-colony stimulating factor (G-CSF), or granulocyte-macrophage colony-stimulating factor (GM-CSF) within 3 weeks prior ot the first scheduled dose of CMB305
• Female of child bearing potential who is pregnant, is planning to become pregnant, or is breast feeding; or male who is sexually active with a female of child bearing potential who is planning to become pregnant.