Iron, an essential
element for all aerobic organisms, exists in a very insoluble form under physiological conditions. Therefore, most microorganisms secrete
iron chelating compounds called
siderophores which are able to sequester ferric
ions from the environment. A vast number of such compounds has been isolated from cultures of microorganisms and tested for enhancement of
iron excretion in experimental animals. Only one compound,
deferrioxamine B, has been shown to be clinically effective and well tolerated in humans suffering from chronic
iron overload. However, this
drug can only be administered successfully by injection or slow infusion. In spite of considerable research it has not been possible to overcome this drawback by developing suitable formulations or derivatives which are orally active. Deferri-
ferrithiocin, a novel type of
siderophore, has recently been isolated from a streptomyces culture. This substance is well absorbed orally and has been shown to enhance the excretion of ferric ion in
iron loaded rats. Further investigations are now necessary to establish acute toxicity levels and longterm tolerability before efficacy tests in man can be planned. Other recent developments in the field of
metal chelation include experimental studies using deferrioxamine for the treatment of conditions resulting from toxic levels of
iron or
aluminium in chronically dialyzed patients. In addition, attempts are being made to administer
chelation therapy in the treatment of various
infections and chronic
inflammation, as well as other conditions linked with disorders of
iron metabolism.