CY-503 for the Treatment of Chemotherapy-refractory Metastatic Colorectal Cancer

Inclusion Criteria * Age ≥ 18 years * Patients are eligible with diagnosis of measurable metastatic colorectal carcinoma and radiologic documentation of disease progression during or with 3 months after termination of standard chemotherapy (fluoropyrimidine-based therapy with oxaliplatin and irinotecan). Patients who had to interrupt the 1st or 1nd line therapy due to intolerance or who were refractory or intolerant to the standard treatment regimens are eligible, too. Bevacizumab can, but does not need to be administered at discretion of treating physician. Patients with K-RAS wild-type can be treated with cetuximab or panitumumab before they enter the study. * No chemotherapy within 4 weeks before treatment start * No residual significant toxicity (greater than NCI grade 1), in case of peripheral neuropathy: no symptoms of peripheral neuropathy of NCI CTC grade 4 within 4 weeks before treatment start. * No previous treatment with experimental therapies after standard therapies is allowed. * Patients must use effective contraception if of reproductive potential. Females must not be pregnant or lactating * Eastern Cooperative Oncology Group (ECOG) Performance status of 0 - 2 * WBC ≥ 3,000/mm3, absolute neutrophil count (ANC) ≥ 1,500/mm3, platelet count ≥100,000/mm3 * Bilirubin ≤ 2.0 mg/dL (40 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) ≤ 5 × upper limit of normal (ULN); hepatic alkaline phosphatase ≤ 3.0 × ULN (in case of liver metastases higher levels do not hinder inclusion of patients) * Serum creatinine ≤ 2.0 mg/dL (180 μmol/L)or creatinine clearance \>= 50 ml/min. , proteinuria \< 2.0 g/24 hr urine collection in patients with a positive urine dipstick for protein * Written informed consent according to ICH-GCP and national laws and regulations prior to receipt of any trial medication or beginning trial procedures Exclusion Criteria: * Evidence of any other malignant disease (with the exception of tumors operatively cured at least 5 years prior to the trial) * Known brain metastases * Uncontrolled pleural effusions * Interstitial pneumonitis or pulmonary fibrosis * Severe/ unstable systemic disease or infection and circumstances not permitting trial participation (e.g., alcoholism or substance abuse) * Unstable cardiac disease in the last 6 months * Use of conventional mistletoe preparations, any immunostimulating substances and/or monoclonal antibodies within four weeks prior to and during the trial - ongoing therapy with steroids is permitted if the dose is not higher than 20 mg of prednisone-equivalent at the time of inclusion and during this clinical trial * Any evidence or history (elicited by the investigator) of symptomatic cerebrovascular events (i.e., stroke or transient ischemic attack) within 6 months prior to randomization * Any history or evidence of pulmonary embolism or thrombophlebitis (including deep vein thrombosis) requiring anticoagulant therapy (e.g., marcumar or heparin) * History of hypersensitivity to 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, including substance dependence or abuse that, in the opinion of the investigator, might not permit the patient to complete the trial or sign the informed consent