The pharmacological manipulation of fetal haemoglobin: trials using hydroxyurea and recombinant human erythropoietin

Abstract

Hydroxyurea (HU) and recombinant human erythropoietin (rHuEpo) have been used in several studies to elevate Hb F level in sickle cell disease (SCD) patients and hence to ameliorate the clinical presentations of the disease. The treatment protocol and doses have varied in the different studies. We studied the effects of HU+rHuEpo combination therapy in sickle cell anaemia (SCA patients) to investigate the Hb F manipulation and hence treatment of SCA. Six patients with severe SCA were selected for treatment with HU (20-25 mg/kg body weight) and rHuEpo (400-800 U/kg body weight) combination therapy for 4 weeks followed by HU (20-25 mg/kg body weight) maintenance therapy for 6 months to 1 year. Iron and folic acid were administered during HU+rHuEpo treatment. Signs, symptoms and complications were recorded to obtain the severity index. Only patients with a severity index > or = 6 were included in the study. Haematological and biochemical parameter values, Hb A2, Hb F, Hb F distribution, Hb F cells, bilirubin level and reticulocyte count were assessed at least on 2-3 occasions prior to initiation of the therapy protocol to establish baseline values. During the treatment period, the clinical presentations were monitored and the estimation of the laboratory parameters was carried out every 4-8 weeks. The results of these parameters during HU and rHuEpo combination therapy and HU maintenance therapy were compared with baseline values using paired t test. The elevation in the level of Hb F, Hb F cells, total haemoglobin, red cell count and MCV were significant (p < 0.005), while reticulocyte count and total bilirubin were significantly decreased (p < 0.05). Each patient showed an individual pattern of Hb F elevation. The increase in Hb F level was correlated with the haematological and biochemical parameters using the General Linear Model Programme of Statistical Analysis System. In general, the clinical presentation improved as Hb F level increased in each patient. In addition, the positive correlation with the haematological parameters and negative correlation with reticulocytes and total bilirubin confirmed the beneficial effect of elevated Hb F level on reducing red cell haemolysis. No correlation could be demonstrated between the pretreatment Hb F level and the increase in Hb F during the treatment period. Daily doses of HU with a single intravenous rHuEpo and iron supplementation elevate Hb F and Hb F cells in SCA patients. The Hb F level can be maintained high on HU therapy alone.(ABSTRACT TRUNCATED AT 400 WORDS)