An open label, safety and pharmacokinetic study of oral hydroxyurea solution administered to
children from 6 months to 17.99 years (i.e. to the day before 18th birthday), with a 12 to 15
month treatment period for each participant. The study treatment duration will be for 6
months at the maximum tolerated dose [MTD], which is usually reached by 6 months after
initiation of treatment. For patients in whom time to MTD is longer than 6 months or not
achieved at all, the maximum duration of study treatment will be 15 months.