Since its inception in 1997, the NHLBI Sickle Cell Disease (SCD) Reference Laboratory (Ref Lab) has received over 150 candidate drugs from over 30 researchers, universities and companies for evaluation. All candidate drugs are evaluated for both their beneficial and adverse effects in vitro using more than 10 sophisticated methods. Specifically, each candidate drug is studied to see whether it inhibits cell sickling, prolongs the delay time prior to deoxy-hemoglobin (Hb) S polymerization, increases the solubility of deoxy-Hb S, hydrates red blood cells (RBCs), prevents dehydration of RBCs, shifts the oxygen equilibrium curve (OEC) toward the left, reduces the adhesion of RBCs to endothelial cells, promotes the synthesis of Hb F, causes hemolysis, promotes formation of met-Hb and increases the denaturation of intracellular Hb S. With this new approach, we have found more than 10 new antisickling agents that showed beneficial effects without significant adverse effects in the in vitro tests. Of these, five drugs were further studied in vivo using transgenic mice that produce human Hb S, and all five drugs inhibited the formation of sickled cells in the blood and significantly prolonged their survival time under acute hypoxic conditions. The five drugs are NIPRISAN (plant extracts) [Brit. J. Haematol. (BJH) 122:1001,2003], MX-1520 (prodrug of vanillin) (

BJH 125: 788,2004
), 5-hydroxymethyl-2-furfural (5HMF) (
BJH 128:552,2005
), NS3623 (Blood 97: 1461,2001, in vivo results not shown), and FLOCOR (surfactant) (
Blood 94:420a,1999
). Of these 5 drugs, FLOCOR and NS3623 did not have an antisickling effect in vitro. It is quite interesting that FLOCOR and NS3623 which showed no direct antisickling effect in vitro, showed a strong antisickling effect in vivo. Some of our results suggest that combined use of some of these drugs may have a synergistic effect in vivo. Studies on the combined use of these drugs are planned. Researchers with candidate drugs that may have beneficial effects for SCD are welcome to contact the SCD Ref Lab for free in vitro evaluation of their agents (for more information, please see our website at www.tatcom.com/sickle-cell).

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