The Efficacy and Safety of Rilzabrutinib in Participants Aged 10 to 65 Years With Sickle-cell Disease

This is a multicenter, randomized, double-blind, placebo-controlled, parallel-group, flexible-adaptive, group-sequential study (Part A), followed by an open-label LTE period (Part B) to investigate the efficacy, and safety of rilzabrutinib in participants with sickle-cell disease (SCD). Study details include: * Study duration: a 52-week double-blind period (Part A), followed by an open-label LTE period (Part B). Double-blind period has two parts, 50% (adult only) until the interim analysis (a proof-concept part analogous to a phase 2b study), and 50% (adult and children) after the interim analysis. Only the participants who complete double-blind treatment period (Part A) are eligible to continue to the LTE period. The duration of the LTE period (Part B) will be from the first-participant-in (FPI)-LTE (Part B) until the last participant who enters the LTE has completed 52 weeks. * Treatment duration: 52-week double-blind period (Part A); LTE period (Part B) from the (FPI until the last participant who enters the LTE has completed 52 weeks. * Visit frequency: Week visits based on the Schedule of Assessments.

Inclusion Criteria: * Participants who have been diagnosed with SCD. * Participants who have had between ≥2 and ≤10 episodes of documented clinical VOC within 12 months of the screening events. * Participants who are either not on hydroxyurea and/or L-glutamine at the Screening Visit and does not plan to receive them during the course of the study or has received HU and/or L-glutamine for a minimum of 6 months. Participants on hydroxyurea and/or L-glutamine must have been on a stable weight-based dose level (mg/kg) for at least 3 months prior to the Screening Visit, with the intent to continue at the same weight-based dose level for the duration of the study, except for safety reasons. * Participants with Eastern Cooperative Oncology Group (ECOG) performance status grade 2 or lower. * Contraceptive use by men and women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies. * For participants ≥10 to \