• Male or female.

• Age 12 years or above at the time of signing the informed consent.

• Confirmed diagnosis of sickle cell disease: Documentation of sickle cell disease (SCD) genotype (HbSS, HbSβ0-thalassemia or other sickle cell syndrome variants) based on prior history of laboratory testing or screening test results from central laboratory. Molecular genotyping is not required. SCD genotype may be determined from the results of haemoglobin (Hb) electrophoresis, high-performance liquid chromatography (HPLC) or similar testing. Note that Hb electrophoresis is performed by the central laboratory at screening.

• Have 1-15 episodes of documented vaso occlusive crises (VOC) within the 12 months prior to screening. Documentation must exist in the participant's medical record prior to randomisation. Events based solely on participant recall without supporting documentation should not be counted towards eligibility.

• Hb greater than or equal to (≥) 5.0 and less than or equal to (≤) 10.0 g/dL (greater than or equal to (≥) 50 and less than or equal to (≤) 100 g/L) at screening.