Sickle Cell Anemia and Antisickling Agents Then and Now

Sickle cell anemia is a genetic blood disorder arising from a point mutation in the b-globin gene that leads to the replacement of glutamic acid residue by valine at the sixth position of the b-chain of hemoglobin. At low oxygen tension, the mutant hemoglobin, sickle hemoglobin, polymerizes inside the red blood cells into a gel or further into fibers leading to a drastic decrease in the red cell deformability. As a result, micro-vascular occlusion arises which may lead to serious, sometimes fatal, crises. The present article reviews the historical, genetic, molecular, cellular, and clinical aspects of the disease. A review for the development and design of drugs to treat sickle cell anemia is presented. Anti-sickling agents are classified, based on the target to be modified, into three classes: the gene, the sickle hemoglobin molecule, and the red cell membrane modifiers. In spite of the full understanding of the pathology, physiology, and the molecular nature of the disease, and the development of large number of antisickling agents, a cure for sickle cell anemia still is unavailable. Strategies to treat sickle cell anemia since the early times of the disease state discovery in 1910, has focussed mainly on prophylactic measures to alleviate the painful crises. The article addresses clinical approaches used then and now to treat the disease, and the rationale of their use. Currently in clinical pracice, hydroxyurea is the most commonly used agent to treat the disease, and it has been recently approved by the united states Food and Drug Administration as a drug for that purpose.