Study to Assess the Effect of Long-term Treatment With Voxelotor in Participants Who Have Completed Treatment in Study GBT440-031

An Open Label Extension Study of Voxelotor (GBT440) Administered Orally to Participants With Sickle Cell Disease Who Have Participated in Voxelotor Clinical Trials

Open Label Extension Study of Voxelotor Clinical Trial Participants with Sickle Cell Disease Who Participated in Voxelotor Clinical Trials

This open label extension (OLE), multi-center study will be conducted at approximately 100 clinical sites globally and will be available to eligible participants from study GBT440-031.

The study will enroll participants from GBT440-031 (approximately 435) under any of the following conditions:

• Participant has completed 72 weeks of treatment regardless of dose selection for GBT440-031
• Dose selection has occurred for GBT440-031 and participant is on non-selected dose on GBT440-031
• GBT440-031 study interim data analysis and/or study modifications have occurred
• GBT440-031 study has completed

The objective of this open-label extension (OLE) study is to assess the long-term safety and treatment effect of voxelotor in participants who have completed treatment in study GBT440-031, using the following parameters:

1. Safety based upon AEs, clinical laboratory tests, physical examinations (PE) and other clinical measures.
2. Frequency of sickle cell disease (SCD)-related complications.
3. Hemolytic anemia as measured by hematological laboratory parameters (e.g. hemoglobin, reticulocytes and unconjugated bilirubin).

All participants will receive daily voxelotor treatment.

Participants may receive study drug as long they continue to receive clinical benefit which outweighs risk as determined by the Investigator and/or until the participant has access to voxelotor from an alternative source (i.e., commercialization or through a managed access program).

Inclusion Criteria:

• Male or female study participants with SCD who participated and received study treatment in Study GBT440-031.

Note: Participants in GBT440-031 who discontinued study drug due to an AE, but who remained on study may be eligible for treatment in this study provided the AE does not pose a risk for treatment with voxelotor.

• Females of child-bearing potential are required to have a negative urine pregnancy test prior to dosing on Day 1.
• Female participants of child-bearing potential must use highly effective methods of contraception to 30 days after the last dose of study drug. Male participants must use barrier methods of contraception to 30 days after the last dose of study drug.
• Participant has provided written informed consent or assent (the ICF must be reviewed and signed by each participant; in the case of pediatric participants, both the consent of the participant's legal representative or legal guardian, and the participant's assent must be obtained).

Exclusion Criteria:

• Female who is breast-feeding or pregnant.
• Participant withdrew consent from Study GBT440-031.
• Participant was lost to follow-up from Study GBT440-031.
• Participant requiring chronic dialysis.
• Any medical, psychological, safety, or behavioral conditions, which, in the opinion of the Investigator, may confound safety interpretation, interfere with compliance, or preclude informed consent.