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Subject: CHELATOR DRUGS
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Blood 81: 2166-73 (1993)[93229759]
A comparative study of the iron-clearing properties of desferrithiocin
analogues with desferrioxamine B in a Cebus monkey model.
R. J. Bergeron, R. R. Streiff, E. A. Creary, R. D. Daniels, W. King, G.
Luchetta, J. Wiegand, T. Moerker & H. H. Peter
Department of Medicinal Chemistry, Medicine, University of Florida,
Gainesville 32610-0485.
A comparative study of the iron-clearing properties of subcutaneously
administered desferrioxamine B (DFO) with those of orally administered
desferrithiocin sodium salt (1), desmethyl desferrithiocin (2),
desazadesmethyl desferrithiocin sodium salt (3), desazadesmethyl
desferrithiocin pivaloyloxymethyl ester (4), and
desazadesmethyl-5,5-dimethyl desferrithiocin (5) in an iron-loaded
Cebus monkey model and a non-iron overloaded bile duct-cannulated rat
model is presented. All six drugs, which performed well in rodent
studies, demonstrated increased efficiency in the Cebus monkey model.
When administered to rodents at a daily dosage of 384 mumol/kg over a
period of 10 days, drug 1 demonstrated severe renal toxicity. whereas
drugs 3, 4, and 5 exhibited severe gastrointestinal (GI) toxicity.
Under the same experimental protocol, drug 2 did not show significant
toxic side effects. In addition, to further evaluate the iron-clearing
properties of analogue 2, a dose-response study was performed in the
primates that showed that iron excretion increased in a dose-dependent
fashion.
MeSH Terms:
* Animal
* Cebus
* Comparative Study
* Deferoxamine/administration & dosage
* Deferoxamine/metabolism
* Dihydropyridines/administration & dosage
* Dihydropyridines/metabolism
* Dihydropyridines/toxicity
* Feces/chemistry
* Gastrointestinal Diseases/chemically induced
* Iron/metabolism
* Iron/urine
* Kidney Diseases/chemically induced
* Male
* Rats
* Rats, Sprague-Dawley
* Siderophores/metabolism
* Thiazoles/administration & dosage
* Thiazoles/metabolism
* Thiazoles/toxicity
Substances:
* Iron
* Siderophores
* Thiazoles
* Deferoxamine
* Dihydropyridines
* desferrithiocin
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Subject: deferiprone/chelator/NEW
Blood 86: 2008-2013 (1995)[95383676]
Deferiprone (L1) chelates pathologic iron deposits from membranes of intact
thalassemic and sickle red blood cells both in vitro and in vivo.
O. Shalev, T. Repka, A. Goldfarb, L. Grinberg, A. Abrahamov, N. F.
Olivieri, E. A. Rachmilewitz & R. P. Hebbel
Department of Medicine, Hadassah-Hebrew University Hospital,
Jerusalem, Israel.
Red blood cell (RBC) membranes from patients with the thalassemic and
sickle hemoglobinopathies carry abnormal deposits of iron presumed to
mediate a variety of oxidative-induced membrane dysfunctions. We
hypothesized that the oral iron chelator deferiprone (L1), which has
an enhanced capacity to permeate cell membranes, might be useful in
chelating these pathologic iron deposits from intact RBCs. We tested
this hypothesis in vitro by incubating L1 with RBCs from 15 patients
with thalassemia intermedia and 6 patients with sickle cell anemia. We
found that removal of RBC membrane free iron by L1 increased both as a
function of time of incubation and L1 concentration. Thus, increasing
the time of incubation of thalassemic RBCs with 0.5 mmol/L L1 from 0.5
to 6 hours, enhanced removal of their membrane free iron from 18% +/-
9% to 96% +/- 4%. Dose-response studies showed that incubating
thalassemic RBC for 2 hours with L1 concentrations ranging from 0.125
to 0.5 mmol/L resulted in removal of membrane free iron from 28% +/-
15% to 68% +/- 11%. Parallel studies with sickle RBCs showed a similar
pattern in time and dose responses. Deferoxamine (DFO), on the other
hand, was ineffective in chelating membrane free iron from either
thalassemic or sickle RBCs regardless of dose (maximum, 0.333 mmol/L)
or time of incubation (maximum, 24 hours). In vivo efficacy of L1 was
shown in six thalassemic patients whose RBC membrane free iron
decreased by 50% +/- 29% following a 2-week course of L1 at a daily
dose of 25 mg/kg. As the dose of L1 was increased to 50 mg/kg/d (n =
5), and then to 75 mg/kg/d (n = 4), 67% +/- 14% and 79% +/- 11%,
respectively, of their RBC membrane free iron was removed. L1
therapy--both in vitro and in vivo--also significantly attenuated the
malondialdehyde response of thalassemic RBC membranes to in vitro
stimulation with peroxide. Remarkably, the heme content of RBC
membranes from L1-treated thalassemic patients decreased by 28% +/-
10% during the 3-month study period. These results indicate that L1
can remove pathologic deposits of chelatable iron from thalassemic and
sickle RBC membranes, a therapeutic potential not shared by DFO.
Furthermore, membrane defects possibly mediated by catalytic iron,
such as lipid peroxidation and hemichrome formation, may also be
alleviated, at least in part, by L1.
MeSH Terms:
* Anemia, Sickle Cell/blood
* Comparative Study
* Erythrocyte Membrane/drug effects
* Erythrocyte Membrane/metabolism
* Erythrocytes/drug effects
* Erythrocytes/metabolism
* Human
* Iron/blood
* Iron Chelates/pharmacology
* Iron Chelates/therapeutic use
* Lipid Peroxidation/drug effects
* Malondialdehyde/blood
* Pyridones/pharmacology
* Pyridones/therapeutic use
* Splenectomy
* Support, Non-U.S. Gov't
* Support, U.S. Gov't, P.H.S.
* Thiobarbituric Acid Reactive Substances/analysis
* beta-Thalassemia/blood
* beta-Thalassemia/therapy
Substances:
* Iron
* Malondialdehyde
* Iron Chelates
* Pyridones
* 1,2-dimethyl-3-hydroxypyrid-4-one
* Thiobarbituric Acid Reactive Substances
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