Inclusion Criteria:  Body weight >=40 kg. Male or female with confirmed diagnosis of HbSS (SCD genotype of sickle cell anemia) or HbSβ0 (SCD genotype of sickle cell beta zero thalassemia). Two or more (>=2) to <=10 documented VOEs in the 12 months prior to randomisation. If receiving concurrent SCD-directed therapy, the participant must have been on a stable dose for a minimum of 3 months prior to study enrollment. There should be no plans to modify the participants' dosing throughout the study duration, other than for safety reasons. If receiving erythropoietin, the participant must have been prescribed this medication for the preceding 3 months and be dose-stabilised for at least 3 months prior to study enrollment. Vaccination against N. meningitides and Vaccinations against H. influenza type B and S. pneumonia. Participants who have been vaccinated (partially or in full) against SARS-CoV-2 with a locally approved vaccine are eligible to be enrolled in the study, 3 days or longer after inoculation. Adequate hepatic and renal function. For women of childbearing potential: agreement to remain abstinent or use contraception during the treatment period and for 6 months after the final dose of study treatment.  Exclusion Criteria:  History of hematopoietic stem cell transplant. Participating in a chronic transfusion program and/or planning on undergoing an exchange transfusion during the duration of the study. History of hypersensitivity, allergic, or anaphylactic reactions to any ingredient contained in the study treatment. Received active treatment on another investigational trial within 28 days (or within five half-lives of that agent, whichever is greater) prior to screening visit, or plans to participate in another investigational drug trial. Hemoglobin <6 g/dL. Known or suspected hereditary complement deficiency. Active systemic bacterial, viral, or fungal infection within 14 days before first drug administration. Presence of fever (>=38 degrees Celsius) within 7 days before the first drug administration. Immunised with a live attenuated vaccine within 1 month before first drug administration. Pregnant or breastfeeding, or intending to become pregnant during the study or within 6 months after the final dose of study treatment. Known HIV infection with documented CD4 count <200 cells/microliter within 24 weeks prior to screening. History of N. meningitidis infection within the prior 6 months.