Effect of Ticagrelor vs. Placebo in the Reduction of Vaso-occlusive Crises in Pediatric Patients With Sickle Cell Disease

Hestia3 will evaluate the efficacy, safety and tolerability of ticagrelor versus placebo in children with SCD during treatment for at least 12 months and up to approximately 24 months. * The target population are children aged ≥2 to \<18 years of age and body weight of ≥12 kg diagnosed with HbSS or HbS/β0 confirmed by high-performance liquid chromatography or hemoglobin electrophoresis. At least 50 evaluable patients should be recruited in each of the age groups, ≥2 years to \<12 years and ≥12 years to \<18 years. * To be eligible for the study, patients must have experienced at least 2 VOCs (defined as painful crisis and/or ACS) events in the past 12 months prior to Visit 1, indicating that the severity of the patient's disease justifies preventive chronic long-term treatment. The intent is to enroll only children aged 2 years or above, since VOCs become more frequent with age. * Study participants should receive standard of care for SCD, adjusted to the individual patient at the discretion of the investigator, including routine health care screening examinations and immunizations according to local guidelines and health care programmers. Study drug will be given on the background of standard treatments for SCD. Study participants are not withheld from any other treatments that may be used in SCD (eg., hydroxyurea) during the trial, which is important considering the use of a placebo control group. However, restrictions apply to some medications and interventions that may be necessary for the patient's health and well-being during the study. * Patients are to be followed up to 24 months or until a common study end date is reached defined as 12 months after the last patient is randomised. The expected average follow-up is 18 months. Considering inclusion of patients with at least 2 VOC events in the past year, this treatment duration is considered long enough to evaluate effects on VOC events as well as to capture safety and tolerability data supporting a potential future long term use of ticagrelor. * Due to ticagrelor mechanism of action and the potential to reduce symptoms caused by ischemia during a vaso-occlusion, a composite endpoint with painful crises and/or ACS has been selected for the primary endpoint. Painful crisis is the most common reason for emergency department visits for patients with SCD with a significant impact on young patients' lives, affecting them physically and emotionally. Secondary endpoints are included to broaden the understanding of effects in patients with SCD and to also assess potential benefits on symptomatic disease burden and health-related quality of life (HRQL). * Patients will be treated with 15, 30 and 45 mg bd or matching placebo, depending on body weight.