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PubMed1990

Development of an HPLC method for measuring orally administered 1-substituted 2-alkyl-3-hydroxypyrid-4-one iron chelators in biological fluids.

"High-performance" liquid-chromatographic (HPLC) methods have been developed for identifying 1-substituted 2-alkyl-3-hydroxypyrid-4-one iron chelators in serum and urine. Ion pairing with heptane- or octanesulfonic acid in pH 2.0-2.2 phosphate buffer and reversed-phase chromatography were required to separate these compounds from endogenous compounds in both biological fluids. In both the 2-methyl and 2-ethyl series of 1-substituted compounds (H, methyl, ethyl, or propyl) the elution times increased in accordance with the n-octanol/water partition coefficients (propyl greater than ethyl greater than H greater than methyl). Urine samples were filtered (0.4 microns pore size) and injected either undiluted or after dilution with elution buffer. After the addition of internal standard, the plasma or serum samples were deproteinized by treatment with HCIO4, 0.5 mol/L, centrifuged, and the supernates were injected directly onto the HPLC. Using these procedures, we could identify 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in the serum and urine of a thalassemic patient who had received a 3-g dose of the drug and in the urine of other patients who had received the same dose. One or more possible metabolites were also observed in the chromatograms of both urine and serum. The 24-h urinary output of L1 (0.22-2.37 g) and iron (10.6-71.5 mg) varied but there was no correlation between the two with respect to quantity or concentration. Instead, urinary iron output was higher in patients with a greater number of transfused units of erythrocytes. This is the first study in humans to show that L1 is absorbed from the gut, enters the circulation, and is excreted in the urine.

Adolescent↗
PubMed1990

Methodological issues in studying the effect of the new oral chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) on absorption of iron.

Although deferoxamine is currently the drug of choice for iron chelation, there is more and more evidence of its toxicity. As a replacement for deferoxamine, 1,2-dimethyl-3-hydroxypyrid-4-one (L1), a new oral iron chelator, is undergoing clinical studies in thalassemic patients. Iron handling in experimental acute iron intoxication is being studied in a multiphase study. Preliminary results suggest that the L1-iron complex is not absorbed from the gastrointestinal tract. Methodological issues in studying iron chelation in the context of acute iron intoxication are presented.

Administration, Oral↗
PubMed1989

Oral iron chelators.

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Administration, Oral↗
PubMed1989

Comparison of activity of deferoxamine with that of oral iron chelators against human neuroblastoma cell lines.

The iron chelator, deferoxamine, has demonstrated cytotoxicity against neuroblastoma cells. In this study we examined the in vitro antineuroblastoma activity of several potentially less expensive oral chelating agents. On a mole for mole basis, 1-hydroxypyridine-2-thionine (omadine) had 100 times the cytotoxicity of deferoxamine. 1,2-Dimethyl-3-hydroxypyrid-4-one also caused demonstrable cell death but at considerably higher molar concentrations than those required for deferoxamine. 2,3-Dihydroxybenzoic acid had no effect on neuroblastoma cell viability over a range of concentrations. In contrast to the effect of both deferoxamine and 1,2-Dimethyl-3-hydroxypyrid-4-one, those due to omadine were permanent within 24 hours of incubation, were not significantly altered by the presence of ionic iron, and correlated with an increase in the percentage of cells in the S-G2-M phases of the cell cycle. On the basis of these in vitro studies, we believe that the use of omadine in particular and iron chelators in general, by themselves or as cell cycle-recruiting agents together with standard cell cycle specific drugs, is an approach to the treatment of cancer worth further investigation.

Administration, Oral↗
PubMed1995

Effect of iron overload on the metabolism and urinary recovery of 3-hydroxypyridin-4-one chelating agents in the rat.

Three orally active iron chelating agents from the 3-hydroxypyridin-4-one series of compounds were administered by gavage to both normal and iron-overloaded (500 mg Fe/kg) rats at a dose of 450 mumol/kg to investigate the effect of iron loading on metabolism and urinary recovery. Compounds selected for investigation were either poorly metabolized [1-(2'-hydroxyethyl) derivative, CP102] or predominantly biotransformed by either phase I [1,2-diethyl derivative, CP94] or phase II (1,2-dimethyl derivative, CP20) metabolic pathways. Unchanged drug and metabolite(s) recovered in urine were determined by HPLC and iron levels by atomic absorption spectrometry. Significant differences in recovery of unchanged drug were seen for both CP20 (L1) and CP94 between normal and iron-overloaded animals. In contrast, no such difference was seen for the poorly metabolized compound, CP102. For CP20 (L1), the proportion of unchanged drug excreted in the urine increased from 36.2 +/- 9.9% in normal animals to 78.7 +/- 8.1% (p < or = 0.02) in iron-loaded animals and 20.1 +/- 4.5% to 39.9 +/- 8.6% for CP94 (p < or = 0.05). A significant decrease in metabolite recovery of CP20 (L1) was seen with the 3-O-glucuronide conjugate decreasing from 38.2 +/- 8.8% in normal animals to 2.5 +/- 2.0% in the iron-overloaded group. The decrease of the 2-(1'-hydroxyethyl) metabolite of CP94 from 41.4 +/- 6.6% to 29.4 +/- 4.6% in the iron-loaded animals was, however, not statistically significant. Total dose recovered in the urine between normal and iron-overloaded animals was only significant for CP94 (p < or = 0.05).

Animals↗
PubMed1993

Autoantibodies in thalassaemia major: relationship with oral iron chelator L1.

Ninety patients with thalassaemia major were investigated for the occurrence of antinuclear antibodies (ANA), and those with ANA were tested for antibodies to histones (AHA). ANA were detected in 7 of 27 thalassemics on oral iron chelator L1, and in 2 of 63 thalassaemics not on L1 (p < 0.01). AHA were seen in 4 of 7 thalassemics receiving L1 with positive ANA, and in none of the 2 not receiving L1 (p < 0.03). Joint pains were seen in patients receiving L1, but in none of the patients not receiving L1. There was no correlation between hepatitis B or HIV positivity and presence of ANA or joint pains. While some amount of background ANA-positivity was found in patients with thalassaemia major, it was significantly more in patients receiving L1. Laboratory evidence of drug-induced lupus-like reaction was seen only in patients who received L1. In view of serious concerns about the safety of L1 and wide variations in the incidence and severity of adverse reactions reported by different sources, an urgent regulatory audit of all trial centres is essential.

Adolescent↗
PubMedDate not supplied

Pharmacokinetics of representative 3-hydroxypyridin-4-ones in rabbits: CP20 and CP94.

Selected 3-hydroxypyridin-4-ones (HPs) are under clinical investigation as iron chelators. Representative HPs have been shown to be potential aluminum chelators by use of in vitro test systems. This study was conducted to determine systemic availability of representative HPs in rabbits prior to studies of their oral efficacy as aluminum chelators. Each of 12 rabbits was administered 0.45 mmol/kg 1,2-dimethyl- (CP20; L1) and of 1,2-diethyl-3-hydroxypyridin-4-one (CP94; EL1NEt) by gastric lavage and by injection into a lateral ear vein. Each rabbit received both compounds via both routes with at least 7 days between doses. Blood samples (1.5 ml) were collected up to 24 hr after dosing. The HPs were extracted, then analyzed by HPLC with a column packed with graphitized carbon. The mean (+/- SD) systemic clearance, steady-state volume of distribution, mean residence time, mean oral absorption time, and systemic availability for CP20 and CP94 were 0.8 +/- 0.3 and 2.1 +/- 1.4 liter/hr/kg; 1.2 +/- 0.5 and 1.2 +/- 0.5 liter/kg; 1.7 +/- 0.7 and 0.7 +/- 0.3 hr; 0.9 +/- 1.6 and 0.6 +/- 0.5 hr; and 72 +/- 20 and 57 +/- 27%, respectively. Rabbits demonstrated fairly good absorption and rapid elimination of 1,2-dimethyl- and 1,2-diethyl-3-hydroxypyridin-4-one.

Animals↗
PubMed1994

Iron-balance and dose-response studies of the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in iron-loaded patients with sickle cell disease.

Several life-threatening complications of the common disorder sickle cell disease require management with red blood cell transfusions and, hence, long-term iron-chelating therapy. The efficacy of the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) has not previously been determined in patients with sickle cell disease. We compared the efficacy of L1 to that of standard-dose subcutaneous deferoxamine in four regularly transfused patients with homozygous sickle cell disease, who had evidence of severe iron overload and a history of poor compliance with deferoxamine. Determination of 24-hour urinary iron excretion conducted over 5 days immediately after transfusion showed that the mean daily urinary iron excretion induced by L1 at 75 mg/kg/d (0.48 +/- 0.23 mg/kg) was equivalent to that induced by deferoxamine at 50 mg/kg/d (0.39 +/- 0.06 mg/kg). In two of three patients studied, a significant (P < .025) increase in mean daily urinary iron excretion was achieved when the dose of L1 was increased to 100 mg/kg/d. Total iron balance studies, which quantitated both urinary and stool iron excretion on L1 and deferoxamine, determined that mean total daily iron excretion induced by deferoxamine (0.88 +/- 0.05 mg/kg) was significantly greater (P < .05) than that induced by L1 (0.53 +/- 0.17 mg/kg), attributable to the significantly greater stool iron excretion during deferoxamine treatment (0.50 +/- 0.16 mg/kg/d) compared with that measured during L1 treatment (0.12 +/- 0.08 mg/kg/d, P < .01). Stool iron excretion accounted for a significantly greater percentage of total iron excretion during deferoxamine treatment (59% +/- 20%) than during L1 treatment (23% +/- 14%, P < .01). These iron balance studies are the first to compare total iron excretion induced by L1 with that achieved by deferoxamine. They demonstrate that the mean total daily iron excretion during L1 treatment (0.53 +/- 0.17 mg/kg) is sufficient to maintain net negative iron balance in most regularly transfused patients with sickle cell disease. Because long-term compliance with L1 has been shown previously to be superior to that with deferoxamine in patients with homozygous beta-thalassemia, the use of L1 should increase the long-term effectiveness of iron chelation in patients with sickle cell disease.

Administration, Oral↗
PubMed1994

Ability of the orally effective iron chelators dimethyl- and diethyl-hydroxypyrid-4-one and of deferoxamine to restore sarcolemmal thiolic enzyme activity in iron-loaded heart cells.

In view of the profound functional and structural abnormalities shown in our previous studies in cultured, iron-loaded rat heart cells, we have examined the ability of the orally effective iron chelators dimethyl-3-hydroxypyrid-4-one (DMHP or L1) and diethyl-3-hydroxy-pyrid-4-one (DEHP or CP94) and of deferoxamine (DF) to reverse the damage caused by iron loading to heart cell organelles. At a concentration of 1.0 mmol/L, all three iron chelators were equally efficient in removing iron and restoring the activity of the thiolic sarcolemmal enzymes 5'-nucleotidase and Na,K,ATPase. However, at 0.1 mmol/L DMHP and DEHP were less effective than DF both in their iron-mobilizing effect and in promoting thiolic enzyme recovery. The superior efficiency of DF at low concentrations illustrates the advantage of the hexadentate chelating action of DF as compared with bidentate chelators such as DMHP and DEHP requiring a 3 to 1 molar ratio to iron for optimal effect. In contrast to its beneficial effect on sarcolemmal enzyme activity, iron chelation was unable to reverse the increase in beta-hexosaminidase activity caused by abnormal lysosomal fragility. Our study demonstrates for the first time that iron-induced peroxidative damage to the myocardial cell is associated with a marked loss of Na,K,ATPase activity, an enzyme with a major role in the maintenance of cellular resting potential. The timing of this damage and the restoration of Na,K,ATPase function by iron-chelating treatment suggest a cause-and-effect relationship between the observed injury to the sarcolemmal enzyme and the reversible electrophysiologic abnormalities observed in the same heart culture system in our previous studies.

5'-Nucleotidase↗
PubMed1994

The oral iron chelator, 1,2-dimethyl-3-hydroxypyrid-4-one reduces hepatic-free iron, lipid peroxidation and fat accumulation in chronically ethanol-fed rats.

The effect of the oral iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) on liver nonheme iron, lipid peroxidation and hepatic fat accumulation in the intragastric feeding rat model for alcoholic liver disease was studied. Male Wistar rats (225-250 g) were fed liquid diet and ethanol for 1 month. In control pair-fed animals, ethanol was replaced isocalorically by dextrose. Two additional groups of animals (dextrose and ethanol-fed) received L1 (75 mg/kg/day for 30 days). The blood ethanol level in the ethanol-fed animals was maintained between 150 and 350 mg/dl. For each animal, the levels of hepatic nonheme iron, lipid peroxidation and triglyceride were evaluated. The nonheme iron in alcohol-fed animals was significantly higher (416 +/- 15 nmol/g of liver) than in pair-fed dextrose controls (346 +/- 18.5 nmol/g, P < .05). Animals fed ethanol and L1 had significantly lower nonheme iron (364 +/- 9.3 nmol/g) than rats fed ethanol alone (P < .05). L1 had no effect on nonheme iron levels in dextrose-fed controls. The importance of iron in lipid peroxidation in this model is shown by the positive correlation between the nonheme iron levels and microsomal conjugated dienes (r = 0.67, P < .02) and liver thiobarbituric acid reactive substances (r = 0.62, P < .05). The most significant observations in this study were: 1) the higher hepatic nonheme iron content in ethanol-fed rats compared to pair-fed dextrose controls; 2) lower nonheme iron and liver fat in the ethanol-fed rats treated with L1; and 3) the significant positive correlation between the liver nonheme and lipid peroxidation.

Alcoholism↗
PubMed1993

Comparison of the pharmacokinetics of 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in healthy volunteers, with and without co-administration of ferrous sulfate, to thalassemia patients.

Given the mortality and morbidity associated with acute iron intoxication, effective iron chelation which is easily administered in an emergency situation would be ideal. The pharmacokinetics of L1 were examined in 5 healthy adult male volunteers to assess its potential for use in acute iron overload. Ferrous sulfate (600 mg), L1 (900 mg), and ferrous sulfate and L1 were administered on three separate days, each one week apart. On each test day, blood samples were collected at regular intervals for the measurement of plasma L1 and total iron. Pharmacokinetic values were calculated. The data were also compared to that obtained in 10 patients with beta-thalassemia and chronic iron overload. In the normal volunteers, a 20% decrease in the area under the concentration time curve of plasma iron and of plasma L1 was demonstrated when they were co-administered. There was no change in urinary iron excretion when L1 was given with iron (p = 0.414). The elimination half-life of L1 in the thalassemia patients (137.65 +/- 48.65 min) was significantly longer than that in the healthy volunteers (77.56 +/- 13.0) (p = 0.0047) due to larger apparent volume of distribution. In all of the iron-overloaded individuals L1 resulted in increased urinary iron excretion. None of the other pharmacokinetic variables compared were significantly different between these two groups. These studies indicate that at levels below saturation, transferrin does not allow L1 to remove absorbed iron in healthy volunteers, whereas in thalassemia patients, who are beyond saturation of their iron binding capacity, the drug binds iron and promotes its excretion.

Adolescent↗
PubMed1993

Oral iron chelation with 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in iron loaded thalassemia patients.

Despite the successes of deferoxamine (DFO) in the treatment and prevention of iron overload, an effective orally available iron chelating drug is needed, since erratic compliance with irritating, cumbersome parenteral infusions still results in fatal iron accumulation in many patients. Disorders of increased iron absorption should also benefit from the development of safe and effective iron chelating agents. Individuals with non-transfusion-dependent thalassemia (thalassemia "intermedia"), exhibit excessive dietary iron absorption that can lead to serious iron loading by the second or third decade of life. An orally effective iron-chelating drug would have major therapeutic advantages for all these patients.

Administration, Oral↗