Our long-term goal is to develop drugs for the safe, effective treatment of sickle cell anemia. Our approach involves the use of structural information obtained by X-ray crystallography and results of various biochemical and biological assays in the rational design of new compounds, selection of existing drugs, and subsequent modification of selected/designed molecules to enhance their antisickling properties. In continuing our sickle cell research, we propose to study: 1) dihalogenated acrylophenoxy acids and bases designed using X-ray information on the binding of ethacrynic acid at two sites on the hemoglobin molecule; 2) analogs of chloroquine and quinacrine, existing drugs currently used for other purposes that are known to be taken up by red cells in vivo; 3) substituted 4-(2-nitro-1-butenyl)-phenoxy acids and bases; 4) various 4-(2-methylenealkylsulfonyl)-phenoxy acids and bases that react covalently with sickle hemoglobin; and 5) covalently-acting derivatives of the potent, non-covalently-acting anisic acids series. At the Drug Design Institute at the University of Pittsburgh, we will continue to determine X-ray crystal structures, run antigelling assays, perform solution binding studies, perform energy calculations, and model drug-protein interactions. We also will continue our collaboration with M. Perutz and his colleagues at the MRC Laboratory of Molecular Biology (Cambridge, UK) in X-ray determination of binding sites and molecular modeling. Compounds found to have a significant antigelling effect or other desirable properties will be subjected to a series of tests. At the Drug Design Institute, we will measure their in vitro uptake by red cells and their effects on oxygen affinity and red cell deformability. Their allosteric effect on polymerization will be studied by C. Poyart at INSERM (Paris). E. Orringer at the U. of North Carolina at Chapel Hill will assess their effects on red cell volume, ion transport across the red cell membrane, and cell deformability. O. Castro at Howard U. will evaluate their effect on red cell survival time. Thus, with this network of collaborators and NHLBI support, we will continue to progress toward our ultimate goal of developing safe, effective antisickling drugs.
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