Three patients will be treated at each dose level unless a dose-limiting toxicity (DLT) is observed. Enrollment will proceed to the next dose level if 0 of 3 patients experiences a DLT; if one of the first 3 patients experiences a DLT, additional patients will be enrolled until a second patient experiences a DLT (which defines the toxic dose) or until six total patients have been treated at that dose level, whichever comes first. If a second DLT is not experienced within that cohort, dose escalation may continue.