In Part 2, up to forty-eight subjects will complete the study in up to 6 cohorts (Part 2A, Groups D1 to F1, single day dosing, and Part 2B, Groups D2 to F2 eight days' dosing). Subjects in Parts 1 and 2B will be on the study for approximately 7 weeks and Part 2A for approximately 8 weeks. Each subject will participate in one treatment cohort only, residing at the Clinical Research Unit (CRU) from Day -1 (the day before dosing) to Day 6 (120 hours after the single dose in Parts 1 and 2A) and from Day -1 (the day before dosing) to Day 13 (120 hours after the first dose in Part 2B). The proposed total daily dose levels for Part 2 will be up to 10 mg/kg/day given either once daily or in two split daily doses. The duration of the infusions will be between 2 and 24 hours which may include a loading dose to achieve therapeutic plasma concentrations as quickly as possible.