Rarity of systemic lupus erythematosus after oral iron chelator L1

Benefits and risks of deferiprone in iron overload in Thalassaemia and other conditions: comparison of epidemiological and therapeutic aspects with deferoxamine

Deferiprone is the only orally active iron-chelating drug to be used therapeutically in conditions of transfusional iron overload. It is an orphan drug designed and developed primarily by academic initiatives for the treatment of iron overload in thalassaemia, which is endemic in the Mediterranean, Middle East and South East Asia and is considered an orphan disease in the European Union and North America. Deferiprone has been used in several other iron or other metal imbalance conditions and has prospects of wider clinical applications. Deferiprone has high affinity for iron and interacts with almost all the iron pools at the molecular, cellular, tissue and organ levels. Doses of 50-120 mg/kg/day appear to be effective in bringing patients to negative iron balance. It increases urinary iron excretion, which mainly depends on the iron load of patients and the dose of the drug. It decreases serum ferritin levels and reduces the liver and heart iron content in the majority of chronically transfused iron loaded patients at doses >80 mg/kg/day. It is metabolised to a glucuronide conjugate and cleared through the urine in the metabolised and a non-metabolised form, usually of a 3 deferiprone: 1 iron complex, which gives the characteristic red colour urine. Peak serum levels of deferiprone are observed within 1 hour of its oral administration and clearance from blood is within 6 hours. There is variation among patients in iron excretion, the metabolism and pharmacokinetics of deferiprone. Deferiprone has been used in more than 7500 patients aged from 2-85 years in >50 countries, in some cases daily for >14 years. All the adverse effects of deferiprone are considered reversible, controllable and manageable. These include agranulocytosis with frequency of about 0.6%, neutropenia 6%, musculoskeletal and joint pains 15%, gastrointestinal complains 6% and zinc deficiency 1%. Discontinuation of the drug is recommended for patients developing agranulocytosis. Deferiprone is of similar therapeutic index to subcutaneous deferoxamine but is more effective in iron removal from the heart, which is the target organ of iron toxicity and mortality in iron-loaded thalassaemia patients. Deferiprone is much less expensive to produce than deferoxamine. Combination therapy of deferoxamine and deferiprone has been used in patients not complying with subcutaneous deferoxamine or experiencing toxicity or not excreting sufficient amounts of iron with use of either drug alone. New oral iron-chelating drugs are being developed, but even if successful these are likely to be more expensive than deferiprone and are not likely to become available in the next 5-8 years. About 25% of treated thalassaemia patients in Europe and more than 50% in India are using deferiprone. For most thalassaemia patients worldwide who are not at present receiving any form of chelation therapy the choice is between deferiprone and fatal iron toxicity.

Deferiprone: a review of its clinical potential in iron overload in beta-thalassaemia major and other transfusion-dependent diseases

Patients with beta-thalassaemia and other transfusion-dependent diseases develop iron overload from chronic blood transfusions and require regular iron chelation to prevent potentially fatal iron-related complications. The only iron chelator currently widely available is deferoxamine, which is expensive and requires prolonged subcutaneous infusion 3 to 7 times per week or daily intramuscular injections. Moreover, some patients are unable to tolerate deferoxamine and compliance with the drug is poor in many patients. Deferiprone is the most extensively studied oral iron chelator to date. Non-comparative clinical studies mostly in patients with beta-thalassaemia have demonstrated that deferiprone 75 to 100 mg/kg/day can reduce iron burden in regularly transfused iron-overloaded patients. Serum ferritin levels are generally reduced in patients with very high pretreatment levels and are frequently maintained within an acceptable range in those who are already adequately chelated. Deferiprone is not effective in all patients (some of whom show increases in serum ferritin and/or liver iron content, particularly during long term therapy). This may reflect factors such as suboptimal dosage and/or severe degree of iron overload at baseline in some instances. Although few long term comparative data are available, deferiprone at the recommended dosage of 75 mg/kg/day appears to be less effective than deferoxamine; however, compliance is superior with deferiprone, which may partly compensate for this. Deferiprone has additive, or possibly synergistic, effects on iron excretion when combined with deferoxamine. The optimum dosage and long term efficacy of deferiprone, and its effects on survival and progression of iron-related organ damage, remain to be established. The most important adverse effects in deferiprone-treated patients are arthropathy and neutropenia/agranulocytosis. Other adverse events include gastrointestinal disturbances, ALT elevation, development of antinuclear antibodies and zinc deficiency. With deferiprone, adverse effects occur mostly in heavily iron-loaded patients, whereas with deferoxamine adverse effects occur predominantly when body iron burden is lower.

CONCLUSION

Deferiprone is the most promising oral iron chelator under development at present. Further studies are required to determine the best way to use this new drug. Although it appears to be less effective than deferoxamine at the recommended dosage and there are concerns regarding its tolerability, it may nevertheless offer a therapeutic alternative in the management of patients unable or unwilling to receive the latter drug. Deferipone also shows promise as an adjunct to deferoxamine therapy in patients with insufficient response and may prove useful as a maintenance treatment to interpose between treatments.

Drugs recently associated with lupus syndromes

A number of drugs have recently been implicated in a syndrome that resembles systemic lupus erythematosus. One of the difficulties in many of these patients is that the signs, symptoms and serological abnormalities reported in these patients may be a natural consequence of the primary diseases rather than the incriminated drug. A second problem with the studies is a lack of uniform reporting of the techniques used to detect autoantibodies. For example, a patient that has a highly positive ANA with a homogeneous pattern of staining or a positive LE cell test usually has antibodies directed against chromatin components (DNA, histones, high mobility group (HMG) proteins). The discrepancies in clinical criteria and the serological techniques in many of these reports, emphasize the importance of using guidelines for the diagnosis of drug-induced or drug-related lupus. In the future, it appears that the increased use of biological response modifiers such as interferon-alpha and other cytokines may prompt more reports of lupus syndromes associated with their use.

The transport of two iron chelators, desferrioxamine B and L1, across Caco-2 monolayers

The transport of two iron chelators, desferrioxamine B (DFO) and L1 (1,2-dimethyl-3 hydroxypyridin-4-one) has been studied in vitro using the human adenocarcinoma cell line, Caco-2. The transport of DFO and L1 has also been compared with that of their iron-bound complexes, ferrioxamine (FO) and L1(3)-Fe, respectively. We report an apparent permeability coefficient (Papp) value for DFO of 0.170 x 10(-7) +/- 0.080 cm s-1. The Papp value of L1 was 1.297 x 10(-5) +/- 0.133 cm s-1. The Papp values of their iron bound complexes FO and L1(3)-Fe are 0.230 x 10(-7) +/- 0.065 cm s-1 and 2.356 x 10(-6) +/- 0.365 cm s-1, respectively. We have shown that the transport of DFO and FO is similar in the Caco-2 cell system. The transport of L1, however, is greatly reduced when complexed to iron. The value for total uptake after 60 min for DFO into the Caco-2 cells was 1.49 +/- 0.09 x 10(-3) nmol per filter. The values for total uptake after 60 min for L1 and L1(3)-Fe were 0.37 +/- 0.03 nmol per filter and 0.04 +/- 0.01 nmol per filter, respectively. Our results indicate that the poor oral bioavailability of DFO can be attributed to the low epithelial permeability of the molecule coupled with its size (mol wt 656). In contrast, the oral bioavailability observed with L1 is due to the high lipophilicity and low molecular weight (mol wt 139) of the molecule. We believe that these differences between the two molecules account for L1 being better orally absorbed than DFO.