This study is testing a medicine called rilzabrutinib to see if it works and is safe for people with sickle-cell disease (SCD), a condition where red blood cells become sickle-shaped and cause health problems. The study lasts for about a year (52 weeks) and has two parts. In the first part, participants may receive either the medicine or a placebo (a pill with no medicine) without knowing which one they get. In the second part, everyone gets the real medicine. Participants need to visit the clinic regularly as per the study schedule.

• **Study Duration**: About 52 weeks for each part.
• **Visit Frequency**: Weekly visits based on a set schedule.
• **Eligibility**: Must have 2-10 SCD episodes in the past year and follow specific medical guidelines.

People can join if they have 2-10 SCD episodes in a year and meet other criteria. They should not have certain health conditions like recent cancer or heart problems. Participants cannot be using certain other SCD medications close to the study start. It’s important to discuss with a doctor to understand all details and risks.