In the second part of the study (Part 2), doses higher than those previously evaluated may be studied and/or different dosing schedules designed to deliver a maximum tolerated dose over 24 hours. If a dose level higher than those previously studied is chosen, there will be an optional single dose studied initially for safety and pharmacokinetic profile (Part 2A), followed about 14 days later in another group of subjects by exposure at that same dose level over 8 consecutive days (Part 2B). These higher doses may be given in a once or twice daily dosing schedule. Six subjects will receive active compound and two will receive placebo in both the single dose and multiple dose cohorts. The single dose cohorts will receive study drug in a sentinel group design in which two subjects receive study drug (one active and one placebo) on the first day and the rest of the group one day later. There will be a review of safety data by the Principal Investigator and the Medical Monitor after the first two subjects have been dosed and before the last six subjects are dosed in each cohort in part 2A.