This study tests a medicine called CSL889 to see if it's safe and helps with sickle cell disease (SCD) pain crises. SCD is a blood disorder where red blood cells change shape, causing pain. The study focuses on people who have these pain episodes, called vaso-occlusive crises (VOC). CSL889 is given through a vein (intravenously) to see how well it works and how quickly it helps pain go away.

Eligibility: Participants must be at least 12 years old, have SCD, and need pain treatment with strong medicine like opioids. They cannot join if they had more than 5 VOCs needing hospital stays in the past 6 months or have other serious health issues.

• Duration: Participants will be monitored across several visits.
• Risks: As with any study, there could be side effects from the medicine.
• Compensation: Participants may receive compensation for their time and travel.

This is a "phase 2" study, meaning it's not the first time the medicine is being tested, but it's still early to learn more about its safety and effects.