Study CSEG101A2202 is designed as a Phase II, multicenter, open-label study. Up to 45 patients (to identify 27 evaluable patients) will be enrolled to the treatment group crizanlizumab 5.0 mg/kg to complete full PK/PD sampling at week 1 and week 15. In all patients, trough PK/PD samples will also be collected prior to each dose. In addition, throughout the study (and when possible), all patients will have blood drawn for serum to assess PK and PD drawn at times of onset and resolution of each VOC event, fever, or suspected infection. Once the up to 45 patients are enrolled, 10 additional patients will be enrolled to the exploratory treatment group and begin at 7.5 mg/kg of crizanlizumab.