Hemoglobin response in study subjects. Mean hemoglobin response in all 16 patients completing the 50-mg BID dose level, and 9 of 10 subjects completing the 100-mg BID dose level. Error bars correspond to SDs. ∗A linear mixed effects model of hemoglobin change at different dose levels with age and sex as covariates showed a significant change in hemoglobin level compared with baseline at the 20-, 50-, and 100-mg BID dose levels of mitapivat (P = .0007, <.0001, and .0007, respectively).