The purpose of this study is to evaluate the safety, tolerability, and efficacy of JX-594 (Pexa-Vec) administered intravenously either alone or in combination with Irinotecan in colorectal carcinoma patients who are refractory to or intolerant to standard therapy.

This was a Phase 1/2a, open-label, dose-escalation study in patients with advanced colorectal cancer (CRC)

Inclusion Criteria:

• Histologically-confirmed, advanced metastatic colorectal cancer failed treatment with fluoropyrimidine (fluoruracil or capecitabine) and oxaliplatin based therapies or had contradictions to treatment with these drugs as determined by the investigator
• Failed treatment with irinotecan
• Kras mutant tumor or Kras wild-type having failed cetuximab (Erbitux) or panitumumab (Vectibix) or had contradictions to treatment
• Regorafenib-naïve (have not received regorafenib)
• Eastern Cooperative Oncology Group (ECOG) Performance Status 0, 1 or 2
• Measurable tumor (≥1 cm longest diameter)
• Acceptable health status as determined by the investigator and blood work (Chemistry, Complete Blood Count, Coagulation)

Exclusion Criteria:

• Intolerant to Irinotecan (if assigned to the combination arm: Cohort 3, Cohort 4 or Combination Expansion Arm)
• Treatment with ketoconazole, enzyme-inducing anticonvulsants and St. John's Wort (if assigned to combination arm)
• Significant immunodeficiency due to underlying illness and/or medication
• History of severe exfoliative skin condition requiring systemic therapy within the past 2 years
• Clinically significant and/or rapidly accumulating ascites, pericardial and/or pleural effusions
• Active cardiovascular disease, including but not limited to significant coronary artery disease (e.g., requiring angioplasty or stenting) or congestive heart failure within the preceding 12 months
• Viable Centrual Nervous System (CNS) malignancy associated with clinical symptoms
• Received anti-cancer therapy within 4 weeks prior to first treatment (6 weeks for mitomycin c or nitrosoureas)
• Prior participation in any other research protocol involving an investigational medicinal product within 4 weeks prior to first treatment
• Use of prohibited anti-viral medication, interferon/pegylated interferon (PEG-IFN) or ribavirin that cannot be discontinued within 14 days prior to any JX 594 dose
• Inability to suspend treatment with anti-hypertensive medication for 48 hours prior to and 48 hours after all JX-594 treatments.
• Pregnant or nursing an infant
• Diagnosis of chronic inflammatory bowel disease and/or bowel obstruction.