The following groups satisfied the safety and PK guidelines specified in the protocol: Groups 3,4,6,7,8. Groups 5 and 5A did not satisfy the protocol-defined pharmacokinetic criteria. There was considerable inter-subject variability in systemic exposures in this age group, such that a dose escalation to 415mg/m^2 may have resulted in ATV exposures greater than 90,000 ng*hr/mL in some children. Thus, a further dose increase in Groups 5 and 5A was not attempted.