Inclusion Criteria:

- Histologically confirmed, unresectable, Stage IV metastatic melanoma

- Failure of prior chemotherapy and / or immunotherapy based regimen

- Measurable disease (based on RECIST criteria)

- Males and females of at least 18 years of age

- Women of reproductive potential (defined as being <1 year post-menopausal) must have
a negative pregnancy test within 3 days prior to randomization; and men and women of
reproductive potential must agree to practice an effective method of avoiding
pregnancy

- Eastern Cooperative Oncology Group (ECOG) Performance status of 0 or 1.

- Life expectancy of at least 3 months

- WBC ≥ 3,000/mm3, absolute neutrophil count (ANC) ≥ 1,500/mm3, platelet count
≥100,000/mm3

- Bilirubin ≤ 1.5 mg/dL (25.65 μmol/L) (unless due to Gilbert's syndrome in which case
the bilirubin should be ≤3.5 mg/dL (59.86 μmol/L)), aspartate transaminase
(AST)/alanine transaminase (ALT) ≤ 3 × upper limit of normal (ULN); hepatic alkaline
phosphatase ≤ 3.0 × ULN

- LDH ≤ 2.5 upper limit of normal (ULN)

- Serum creatinine ≤ 1.5 mg/dL (132.60 μmol/L), proteinuria < 2.0 g/24 hr urine

- Patients who have had prior treatment with adjuvant or palliative immunotherapy are
eligible provided that therapy ended at least 1 month prior to randomization and all
treatment-related toxicities have resolved

- Patients with bone metastasis should be evaluated by the investigator and prior
treatment should be finished at least 1 month prior to randomization

- Prior radiotherapy (for palliative care only) is allowed provided there is
measurable/evaluable disease outside of the radiation field and all radiation-related
toxicities have resolved; if there is only one measurable lesion it may not have been
irradiated unless subsequent progression has been documented

- Patients who had prior major surgery are eligible if at least 4 weeks have passed
since their surgery and all surgical wounds have healed prior to randomization and at
least one measurable tumor is present

- All toxicities related to prior adjuvant therapy must have resolved

- Written informed consent

Exclusion Criteria:

- Pregnancy or nursing

- Any concurrent chemotherapy, radiotherapy, immunotherapy, biologic or hormonal
therapy for treatment of cancer

- Current or planned participation in a research protocol

- Received an investigational agent within 4 weeks prior to randomization

- Brain metastases or primary brain tumors, symptomatic pleural effusion or ascites
requiring paracentesis

- Ocular melanoma

- History of prior malignancies within the past 5 years other than non-melanomatous
skin cancers that have been controlled, carcinoma in situ of the cervix, T1a or b
prostate cancer noted incidentally during a transurethral resection of prostate
(TURP) with prostate-specific antigen (PSA) values within normal limits since TURP,
or superficial bladder cancer

- Any evidence of or history elicited by the investigator of symptomatic
cerebrovascular events within 6 months prior to randomization; or any history or
evidence of pulmonary embolism or thrombophlebitis requiring anticoagulant therapy

- Any current evidence of hematemesis, melena, hematochezia, or gross hematuria

- Elective surgery planned during the study period through 30 days after the last dose
of CY-503

- History of hypersensitivity to previously administered mistletoe

- Prior therapy with mistletoe

- History of primary immunodeficiency

- Known human immunodeficiency virus (HIV) or known active viral hepatic infections

- Prior treatment with CY-503

- A general medical or psychological condition or behaviour in the opinion of the
investigator, might not permit the patient to complete the study or sign the informed
consent.