Effect of voxelotor on sickling of SS red cells. Fraction sickled vs time after start of deoxygenation to a final oxygen concentration of 5% in the absence of voxelotor and at various concentrations of voxelotor from 30 nM to 100 μM. The vertical bars represent the standard deviation from the average of 44 images. The Hb composition for patient 1 was (89% HbS, 7% HbF, 3.9% HbA₂; Hb = 7.5 g/dL, hematocrit = 22.6%, MCHC = 33.3) and for patient 2 is (76% HbS, 21% HbF, 2.6% HbA₂; Hb = 8.4 g/dL, hematocrit = 22.5%, MCHC = 37.2).