Vaso-occulsive crisis is a complication of Sickle cell disease in which the red blood cells (RBC) change shape, causing congestion within the blood vessels that leads to pain and tissue damage.

The study medication FT-4202, an oral tablet, is believed to reduce the rate of sickle cell polymerization and improve RBC membrane function, thereby reduction sickling of RBCs and their hemolysis (breakdown of red cells) that causes vascular obstruction and anemia.

This study will consist of a 52-week, randomized (volunteers are selected by chance to receive study either study medication or placebo) , placebo controlled (a placebo is a look-alike pill that contains no active medication). There will be 17 study visits.

The study is followed by a 52-week open label extension study in which all participants will receive study medication. There will be 11 study visits.

This registry is an observational study designed to evaluate the effect of Oxbryta in individuals with Sickle Cell Disease (SCD) in a real-world setting.

Participants who are currently taking or have been prescribed and initiating standard of care treatment with Oxbryta are eligible to participate. This registry will collect data that is recorded in participants' medical records and other off site sources. Study data will be collected a regular intervals and entered in case reports (CRFs) by electronic capture system (EDC) by the study staff. Participants will be on the study for 5 years after their first dose of Oxbryta treatment or until they choose to withdraw from the study. Participants who stop Oxbryta treatment prior to the 5 years will continue to be monitored at regular intervals unless they request to withdraw from study. Participants quality of life (QoL) questionnaires will be collected throughout the 5 years of the study.

Participants safety and tolerability will be assessed throughout the study data collection period by the study doctor and reported to the Sponsor.