This study tests a medicine called **rilzabrutinib** for people aged 10 to 65 with **sickle-cell disease (SCD)**, a condition where the red blood cells are shaped like a "sickle" and can block blood flow. The study has two parts: a **52-week double-blind period** (Part A) where neither doctors nor participants know if they are getting rilzabrutinib or a placebo (a fake treatment), and a **long-term extension (LTE) period** (Part B) where everyone gets the real medicine. Candidates must have had 2 to 10 painful episodes due to SCD in the past year. **Key Points:** - **Duration**: You'll spend 52 weeks in the initial study, with more time if you join the LTE period. - **Visits**: Regular visits are required, following a set schedule. - **Eligibility**: You must not have certain medical conditions like cancer, heart problems, or infections like tuberculosis, HBV, or HCV. Participation involves regular check-ups and following specific guidelines, including stable medication doses if already on certain treatments.