5-Azacytidine increases γ-globin synthesis and reduces the proportion of dense cells in patients with sickle cell anemia

We previously demonstrated that 5-azacytidine can selectively increase γ-globin synthesis in a patient with β⁺-thalassemia, prompting us to treat two patients with sickle cell anemia and two additional patients with β⁺ thalassemia. 5-Azacytidine (2 mg/kg/day) was continuously infused for 7 days with no apparent clinical toxicity. The γ/β-globin biosynthetic ratio increased fourfold to sixfold in the bone marrow cells of each patient after treatment and remained elevated for 7-14 additional days. Hypomethylation of DNA near the γ-globin genes in bone marrow cells was demonstrated 2 days after beginning the 5-azacytidine infusion. The peripheral blood fetal hemoglobin (HbF) level increased from 6.0% to 13.7% in one patient with sickle cell anemia and from 1.6% to 8.9% in the second. Stractan gradient analyses of peripheral blood from patients with sickle cell anemia revealed a marked decrease in the percentage of dense cells (cells that contain increased amounts of HbS polymer when deoxygenated) following treatment. These observations provide an impetus to investigate the effects of repeated courses of 5-azacytidine in a small group of severely ill patients to determine whether this drug may have a role in the treatment of patients with sickle cell anemia and β-thalassemia.