Sorafenib Tosylate and Hypoxia-Activated Prodrug TH-302 in Treating Patients With Advanced Kidney Cancer or Liver Cancer That Cannot Be Removed By Surgery

Phase I Registration - Inclusion Criteria * Age ≥18 years * Cytological or histological confirmed diagnosis of advanced hepatocellular or renal cell carcinoma. HCC patients should not be amenable to treatment with surgery or to orthotopic liver transplant. * Patients must have measurable disease as defined in the protocol. * RCC patients only: Tumor progression after receiving standard/approved chemotherapy and/or targeted agent, where there is no approved therapy or for tumors where sorafenib based therapy would be standard therapy. * HCC patients only: * First line (i.e., no prior systemic therapy) or second line (with prior first line sorafenib therapy only) advanced HCC. * Child Pugh class A or B7 liver disease * Prior chemoembolization, radioembolization, radiofrequency ablation (RFA), or other local ablative therapies are permissible if ≥6 weeks from procedure with evidence of progression or new metastatic disease, if applicable. * ECOG Performance Status (PS) 0 or 1. * The following laboratory values obtained ≤14 days prior to registration. * Absolute neutrophil count (ANC) ≥1200/mm3 * Peripheral Platelet Count (PLT) ≥75,000/mm3 * Hemoglobin (HgB) \>8.5 g/dL * Bilirubin ≤3.0 x upper limit of normal (ULN) * SGOT (AST) ≤2.5 x ULN, if subject has HCC or liver metastases ≤5 x UL * SGPT (ALT) ≤2.5 x ULN, if subject has HCC or liver metastases ≤5 x ULN * Creatinine ≤1.5 x ULN * INR ≤1.5 x ULN. Patients receiving anti-coagulation therapy are permitted…