You will have blood drawn (less than 1 teaspoon each) to measure the level of uric acid in your blood at different time points throughout this study so that researchers can learn the effectiveness of the study drug on your disease. You will have a total of 7 samples drawn. Your blood will be drawn on Day 1 before your dose of rasburicase and then at 4, 24, 48, 72, 96,120 (Day 6), and 144 (Day 7) hours after your dose of the study drug.