If you are found to be eligible to take part in this study, you will take RTA 402 by mouth (several capsules a day) in the morning with a glass of water (before eating) on the dose level that will be assigned to you. The dose level you receive will depend on when you begin on this study. You will receive the study drug for 21 days in a row. You will not take the study drug for the next 7 days. This is considered a rest period. These 28 days equal 1 cycle. You should take your study drug as instructed. If a dose is missed or vomited, it will not be replaced either on that day or at the end of the 21-day treatment period.