A Study of Pexa-Vec (JX-594) Prior to Sorafenib to Treat Unresectable Primary Hepatocellular Carcinoma

Inclusion Criteria: * Histological confirmation or clinical/laboratory diagnosis of primary hepatocellular carcinoma (HCC) * Cancer is not surgically resectable for cure * Child Pugh A or B * Performance Score: KPS score of ≥ 70 * Platelet count ≥ 50,000 plts/mm3 * Total bilirubin ≤ 2.5 x ULN * AST, ALT \< 5.0 x ULN * Acceptable coagulation status: INR ≤ 1.5 x ULN * Acceptable kidney function: Serum creatinine \< 2.0 mg/dL * Sorafenib naive or refractory to sorafenib therapy Tumor Status: At least one intrahepatic tumor, and at least ≥50% of the total intrahepatic viable tumor mass, measurable by CT and injectable under imaging-guidance (note: injected and/or viable tumors must be previously untreated or ≥20% increase in size since preceding local-regional treatment). Exclusion Criteria: * Known contraindications to sorafenib * Pregnant or nursing an infant * Significant immunodeficiency due to underlying illness (e.g. hematological malignancies, congenital immunodeficiencies and/or HIV infection/AIDS) and/or medication (e.g. high-dose systemic corticosteroids) * History of exfoliative skin condition (e.g. severe eczema, ectopic dermatitis, or similar skin disorder) that at some stage has required systemic therapy * Clinically significant and/or rapidly accumulating ascites, peri-cardial and/or pleural effusions * Severe or unstable cardiac disease * Current, known CNS malignancy * Use of anti-platelet or anti-coagulation medication * Use of the following anti-viral agents: ribavirin, adefovir, cidofovir (within 7 days prior to the first treatment), and PEG-IFN (within 14 days prior to the first treatment). * Patients with household contacts who meet any of these criteria unless alternate living arrangements can be made during the patient's active dosing period and for 7 days following the last dose of study medication: * Pregnant or nursing an infant * Children \< 12 months old * History of exfoliative skin condition that at some stage has required systemic therapy * Significant immunodeficiency due to underlying illness (e.g. HIV/AIDS) and/or medication