Enrollment staggered by age group starting with the older children (≥12 years). In each younger age group, enrolment was planned to initiate only following a review by the Data Monitoring Committee (DMC) of the clinical safety data and available PK and PD data from the first 3 out of 7 children from the previous older age group. Enrollment of infants <3 months was planned to initiate after recruitment of all patients ≥3 months had been completed and all data analyzed by the DMC.