Combination of simvastatin and tBHQ increases the proportion of HbF in primary human erythroid cells more than either drug alone. Human CD34⁺ peripheral blood cells were treated with 5μM tBHQ, 5μM statin, and a combination of statin + tBHQ during in vitro erythroid differentiation. At the end of differentiation on day 20, cells were lysed and the proportions of HbA (A) and HbF (F) were determined by ion-exchange HPLC. (A) Representative HPLC traces. (B) Quantitation of HPLC traces from 3 independent experiments (2 different donors). Error bars represent ± SEM. *P < .05 compared with untreated; #P < .05 compared with tBHQ.