Clinical AE rates on hydroxyurea treatment. The rates are illustrated as the number of events per 100 patient-years, separated into 6-month treatment blocks. Months 0 to 6 represent the fixed-dose phase, whereas months 6 to 24 include dose escalation to MTD, and months >24 are the MTD treatment phase. (A) All clinical AEs; (B) sickle-related AEs; (C) vaso-occlusive painful events; and (D) infections.