The Effect of Voxelotor on Exercise Capacity of Youths With Sickle Cell Anemia

1. Provision of signed and dated informed consent form

2. Stated willingness to comply with all study procedures and availability for the
duration of the study

3. Male or female, age > 12 years

4. In good general health as evidenced by medical history and diagnosed with a
genetically severe form of sickle cell anemia (Hgb SS, Hgb S beta 0 thalassemia, Hgb
SCHarlem, and others)

5. Patients who are on Hydroxyurea need to be on a stable dose for at least 3 months
without anticipated change in dosing until the study is completed.

6. Ability to take oral medication and willingness to adhere to daily voxelotor and 2
CPETs at scheduled intervals.

7. For females of reproductive potential who are sexually active: use of highly effective
contraception for at least 1 month prior to screening and agreement to use such a
method during study participation and for an additional 30 days after the end of
study.

8. For males of reproductive potential: use of condoms or other methods to ensure
effective contraception with partner