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A large-scale systematic evaluation of potential iron chelators for the treatment of hemosiderosis was conducted. The compounds were identified and evaluated using a hypertransfused mouse screen in which deferrioxamine B was a standard. This screen was designed to measure iron depletion in the tissues as well as iron excretion. Groups of 10 previously hypertransfused BDF1 male mice received a single daily i.p. injection of either vehicle, standard, or test compound for 7 days. Iron in daily urine pools and individual spleen and liver homogenates was determined by atomic absorption. More than 70 chelators were evaluated, including natural and synthetic hydroxamic acids, phenols, catechols and tropolones known to have a high affinity for iron (III) in vitro. Ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid) was shown to be considerably more effective than deferrioxamine B (i.p.) and, in addition, was orally active. Factors determining the efficacy of this and other chelating agents are discussed.

A series of polymers bearing hydroxamic acid-terminated side chains were prepared for the purpose of developing new iron chelators for treating iron overload in beta-thalassemia (Cooley's anemia) and other iron diseases. The polymers are for the most part amino acid amide derivatives of acrylic and methacrylic acid with the terminal carboxyl group converted to the hydroxamic acid. The polymers are generally water soluble and sequester iron(III) avidly. The polymeric iron chelators were assayed via a mouse screen for activity in removing iron. Iron overloaded mice were administered i.p. the iron chelator over a 7-day period. Urine and feces were collected and the iron content measured by atomic absorption. At the end of the treatment period the mice were sacrificed and the livers and spleens were homogenized and examined for iron content. The results were compared with similar data obtained for the iron chelator drug desferrioxamine as a standard. Four of the polymers prepared exhibited strong activity, as good or better than desferrioxamine in iron removal capability. The four polymers are the polyacroloyl and polymethacryloyl derivatives of beta-alanine with the side chain carboxyls converted to the N'--H or N'--CH3 hydroxamic acids. Of these four the polyacryloyl N'--CH3 derivative exhibited superior behavior, being 3 to 5 times as effective as desferrioxamine at the lower dose level. None of the four polymers produced toxic signs and the administration was accompanied by little or no pain response.