Metformin (Met) does not act through known modifiers of HbF. (A) Treatment with Met does not alter expression levels of BCL11A, KLF1, or MYB. HSPCs from 3 patients with SCD were treated with Met (0 or 100 µM), and expression levels were analyzed by RT-qPCR. (B) Effect of Met treatment on BCL11A, as shown in a representative western blot. (C) Aggregate of 3 independent assays, with quantification of the BCL11A XL band. Error bar represents SD. ****P < .00001, *P < .01. N.S, not significant.