The state of the art of fetal hemoglobin-inducing agents.

INTRODUCTION: Sickle cell anemia (SCA) is a hematological genetic disorder caused by a mutation in the gene of the ß-globin. Pharmacological treatments will continue to be an important approach, including the strategy to induce fetal hemoglobin (HbF). AREAS COVERED: Here, we analyzed the articles described in the literature regarding the drug discovery of HbF inducers. The main approaches for such strategy will be discussed, highlighting those most promising. EXPERT OPINION: The comprehension of the mechanisms involved in the ß-globin regulation is the main key to design new drugs to induce HbF. Among the strategies, gamma-globin regulation by epigenetic enzymes seems to be a promising approach to be pursued, although the comprehension of the selectivity role for those new drugs is crucial to reduce adverse effects. The low druggability of transcription factors and their vital role in embryonic human development are critical points that should be taken in account for drug design. The guanylate cyclase and the NO/cGMP signaling pathway seem to be promising not only for HbF induction, but also for the protective effects in the cardiovascular system. The association of drugs acting through different mechanisms to induce HbF seems to be promising for the discovery of new drugs.

Foetal haemoglobin in homozygous sickle cell disease: a study of patients with low HBF levels.

High foetal haemoglobin (HbF) levels are believed to ameliorate the manifestations of homozygous sickle cell (SS) disease. The corollary implies that patients with low HbF levels should have more severe clinical courses. We investigated this in a retrospective study of 50 Jamaican patients with steady-state HbF levels below 1% compared with a control group (A) of 54 subjects with steady-state HbF levels between 2.5 and 3.4% (around the 25th centile for our population), and a second control group (B) of 60 patients with steady-state HbF levels between 4.6 and 5.2% (around the 50th centile). Comparisons across the groups indicated significantly fewer females in the study group (16, 50 and 57%, respectively). Examination for haematological trends across the groups showed positive linear trends for haemoglobin (Hb) (P=0.004), packed cell volume (PCV) (P=0.01), mean cell volume (MCV) (P= < 0.001), mean cell haemoglobin (MCH) (P= < 0.001) and a negative trend for haemoglobin A2 (P=0.03). Clinically, there were no differences in the incidence of painful crises, abdominal crises and the acute chest syndrome, but leg ulcers were significantly less frequent in the study group (P=0.04). Therefore low HbF levels do not appear to increase the clinical severity of SS disease and may be protective against leg ulceration.