Metformin (Met) and HU additively induce HbF in HSPCs from normal individuals and from patients with SCD. (A) HSPCs from a normal individual were treated with the indicated drugs on day 7 of culture and analyzed at day 14. HbA and HbF were measured by HPLC; representative graphs are shown. (B) Aggregate of results of drug treatment of HSPCs from normal individuals on HbF (%). (C) HSPCs from an individual with SCD were treated with the indicated drugs on day 7 of culture and analyzed at day 14. HbA and HbF were measured by HPLC; representative graphs are shown. (D) Aggregate of results of drug treatment of HSPCs from individuals with SCD on HbF (%), calculated as (HbF/HbF+HbA) * 100. Error bar represents SD. ***P < .0001, *P < .05.