Phase 1b Dose Escalation Study of Intravenous JX-594 in Metastatic, Refractory Colorectal Carcinoma

Inclusion Criteria: * Histologically-confirmed, advanced/metastatic colorectal carcinoma * Failed both oxaliplatin and irinotecan based regimens for advanced/metastatic disease (if tumor advanced either immediately or within 3 months of the end of treatment) * Resistance to Erbitux: patients with Ras mutations, or for whom Erbitux has failed (if tumor advanced either immediately or within 3 months of the end of treatment, or there is no response to Erbitux therapy due to a lack of expression of EGFR (epidermal growth factor)) * Karnofsky Performance Score (KPS) ≥ 70 * Age ≥18 years * Laboratory Safety: WBC ≥ 3,500 cells/mm3 and ≤ 50,000 cells/mm3, ANC ≥ 1,500 cells/mm3, Hemoglobin ≥ 10 g/dL (transfusion allowed), Platelet count ≥ 100,000 plts/mm3,Total bilirubin ≤ 1.5 X ULN, INR ≤ 1.5, AST, ALT ≤ 2.5x ULN (in case of liver metastasis: AST,ALT ≤5.0 x ULN) * Serum chemistries within normal limits (WNL) or Grade 1 (excluding alkaline phosphatase) - If patients are diabetic, a fasting glucose must be done and patients must be \> 160 mg/dL. * Patients who, if they are sexually active, are willing and able to refrain from sexual activity for 3 weeks following JX-594 administration. Patients who are willing and able to use a permitted contraceptive for 3 months after the final administration of JX-594. Exclusion Criteria: * Significant immunodeficiency due to underlying illness (e.g. HIV/AIDS) and/or medication (e.g. systemic corticosteroids) * Known myeloproliferative disorders requiring systemic therapy * History of exfoliative skin condition (e.g. eczema or ectopic dermatitis) requiring systemic therapy * History of acquiring opportunistic infections. * Tumor(s) invading a major vascular structure (e.g. carotid artery) * Tumor(s) in location that would potentially result in significant clinical adverse effects if post-treatment tumor swelling were to occur * Clinically uncontrolled and/or rapidly accumulating ascites, pericardial and/or pleural effusions * History of severe or unstable cardiac disease * Current, known CNS malignancy (history of completely resected or irradiated brain metastases by WBRT or stereotactic radiosurgery allowed) * Administered anti-cancer therapy within 4 weeks prior to first treatment (6 weeks in case of mitomycin C or nitrosoureas) * Use of anti-viral, anti-platelet, or anti-coagulation medication \[Patients who discontinue such medications within 7 days prior to first treatment may be eligible for this study.\] Low dose aspirin (approximately 81 mg) allowed. * Pulse oximetry O2 saturation \<90% Pulse oximetry O2 saturation \<90% at rest * Experienced a severe systemic reaction or side-effect as a result of a previous smallpox vaccination * Pregnant or nursing * Household contact exclusions: * Women who are pregnant or nursing an infant * Children \< 5 years old * People with skin disease (e.g. eczema, atopic dermatitis, and related diseases * Immunocompromised hosts (severe deficiencies in cell-mediated immunity, including AIDS, organ transplant recipients, hematologic malignancies)