5-Azacytidine increases HbF production and reduces anemia in sickle cell disease: Dose-response analysis of subcutaneous and oral dosage regimens

Varying doses of 5-azacytidine (5-aza) were given to four sickle cell individuals for 500, 200, 100, and 30 days. The percentage of fetal hemoglobin (HbF) containing reticulocytes (F reticulocytes) increased two- to five-fold within five days of 5-aza therapy in all patients, with a two- to three-fold rapid response (<48 hours after initial dose) in three patients. Reticulocyte suppression was not observed prior to, during, or after therapy in those patients who responded within 48 hours. Subcutaneous 5-aza was given in 35-day courses consisting of every day, every other day, or three consecutive days a week. No marrow toxicity was observed on any of the regimens. For three patients, the highest average F reticulocyte level was observed on the three consecutive day a week regimen. Oral 5-aza, given with tetrahydrouridine, produced comparable F reticulocyte response. In the two patients treated for more than 100 days, Hb levels increased to 11 to 12 and 9 g/dL, MCV and MCH increased by 25%, and lysate HbF levels peaked at 12% and 20%. Fetal erythroid characteristics (i-antigen, galactokinase activity, and Gγ/Aγ ratios) did not correlate with maximal HbF production. The frequency of vasoocclusive crises appeared to decrease in both patients followed for more than 100 days.