During Part 1, 5 escalating single oral doses of RO5024048 or placebo were given to 40 healthy volunteers, when fasted (have not eaten any food for at least 10 hours). The doses given were 500 mg, 1500 mg, 4500 mg, 6000 mg, and 9000 mg. Another group of 6 volunteers was given 1500 mg with food.