This study looks at how safe and effective a medicine called crizanlizumab is for people with Sickle Cell Disease (SCD) who have frequent vaso-occlusive crises (VOC). SCD is a blood disorder that affects red blood cells, and VOCs are painful episodes that occur when blood vessels get blocked. The study compares crizanlizumab to a placebo, which is a substance with no active medicine. Participants can be taking another medicine called hydroxyurea/hydroxycarbamide but must have at least 4 VOCs in the year before joining. The study will include people aged 12 and older who have these conditions.

• The study lasts about 52 weeks, during which participants will receive either crizanlizumab or placebo.
• Participants will be randomly assigned to receive crizanlizumab or placebo, and neither they nor the doctors will know which they are getting.
• Participants must not have had certain treatments or conditions, like a stem cell transplant or blood transfusion, recently.