Once a safe and recommended dose level is determined, an expanded cohort (Expansion Cohort 1) of up to 40 patients with either unresectable HCC or advanced renal cell carcinoma (RCC), for whom sorafenib is indicated, will be enrolled and treated at this dose level (expansion portion). Up to 20 patients with unresectable HCC and up to 20 patients with advanced RCC may be enrolled in this protocol (including patients in dose-escalation cohorts and expansion cohort).