Safety, Efficacy, and Pharmacokinetics of CSL889 in Adults and Adolescents With Sickle Cell Disease During Vaso-Occlusive Crisis

Inclusion Criteria: * At the time of informed consent: * 18 years of age (adults); or * 12 to less than (\<) 18 years of age (adolescents, where approved and when enrollment for adolescents has been opened by the sponsor, with the endorsement of the Independent Data Monitoring Committee \[IDMC\]) * Diagnosed with SCD (any genotype). * Presented at the study site with a new acute VOC necessitating treatment with parenteral opioids. Exclusion Criteria: * VOC pain onset greater than (\>) 72 hours before administration of first parenteral opioid. * Must not have a history of \> 5 VOCs requiring hospital admission in the past 6 months; or signs and / or symptoms of ACS; or new neurological symptoms suggestive of acute stroke or transient ischemic attack; or any stage (acute kidney injury) AKI; or been discharged from inpatient hospital admission for VOC or other vaso-occlusive event within 14 days before the current presentation. * Serum hemoglobin \< 6 g/dL, serum ferritin ≥ 2000 ng/mL, receiving an approved medication for SCD that has not been on a stable, well-tolerated regimen, currently taking methadone or buprenorphine.