Oral iron chelation: a review with special emphasis on Indian work on deferiprone (L1)

Drug Selection and Posology, Optimal Therapies and Risk/Benefit Assessment in Medicine: The Paradigm of Iron-Chelating Drugs

The design of clinical protocols and the selection of drugs with appropriate posology are critical parameters for therapeutic outcomes. Optimal therapeutic protocols could ideally be designed in all diseases including for millions of patients affected by excess iron deposition (EID) toxicity based on personalised medicine parameters, as well as many variations and limitations. EID is an adverse prognostic factor for all diseases and especially for millions of chronically red-blood-cell-transfused patients. Differences in iron chelation therapy posology cause disappointing results in neurodegenerative diseases at low doses, but lifesaving outcomes in thalassemia major (TM) when using higher doses. In particular, the transformation of TM from a fatal to a chronic disease has been achieved using effective doses of oral deferiprone (L1), which improved compliance and cleared excess toxic iron from the heart associated with increased mortality in TM. Furthermore, effective L1 and L1/deferoxamine combination posology resulted in the complete elimination of EID and the maintenance of normal iron store levels in TM. The selection of effective chelation protocols has been monitored by MRI T2* diagnosis for EID levels in different organs. Millions of other iron-loaded patients with sickle cell anemia, myelodysplasia and haemopoietic stem cell transplantation, or non-iron-loaded categories with EID in different organs could also benefit from such chelation therapy advances. Drawbacks of chelation therapy include drug toxicity in some patients and also the wide use of suboptimal chelation protocols, resulting in ineffective therapies. Drug metabolic effects, and interactions with other metals, drugs and dietary molecules also affected iron chelation therapy. Drug selection and the identification of effective or optimal dose protocols are essential for positive therapeutic outcomes in the use of chelating drugs in TM and other iron-loaded and non-iron-loaded conditions, as well as general iron toxicity.

Deferiprone-induced arthropathy in thalassemia: MRI findings in a case

Arthropathy is a well known side effect of the iron chelator deferiprone (L1); however, the imaging findings in deferiprone-induced arthropathy are not well known. In this article, we describe the typical radiographic and MRI findings in a patient receiving regular blood transfusions who developed arthropathy after long-term therapy with the oral iron chelator deferiprone (L1). Deferiprone primarily affects the articular cartilage and the changes include synovial thickening, articular cartilage thickening, and subchondral bone erosions.

Reduction of body iron stores to normal range levels in thalassaemia by using a deferiprone/deferoxamine combination and their maintenance thereafter by deferiprone monotherapy

BACKGROUND

Iron overload and toxicity is the major cause of morbidity and mortality in thalassaemia patients. New chelating drug protocols are necessary to treat completely transfusional iron overload and eliminate associated toxicity. Appropriate deferiprone/deferoxamine combinations could achieve this goal.

METHODS

A single-centre, single-armed, proof-of-concept study of the combination of deferiprone (75-100 mg/kg/d) and deferoxamine (40-60 mg/kg, at least 3 d per week) was carried out in eight patients with thalassaemia major (four men and four women) for 21-68 months. The patients were previously treated with deferoxamine and had variable serum ferritin [geometric (G) mean ± SD = 1446 ± 1035 μg/L] and magnetic resonance imaging relaxation times T2* cardiac (Gmean ± SD = 10.32 ± 6.72 ms) and liver (G mean ± SD = 3.77 ± 4.69 ms). The use of deferiprone (80-100 mg/kg/d) continued for 7-26 months in seven of the eight patients following the combination therapy. Organ function, blood and other biochemical parameters were monitored for toxicity.

RESULTS

  The deferiprone/deferoxamine combination caused an absolute value increase in cardiac (G mean ± SD = 29.6 ± 6.6 ms, P < 0.00076) and liver (G mean ± SD = 25.9 ± 8.07 ms, P < 0.00075) T2* and reduction in serum ferritin (G mean ± SD = 114.7 ± 139.8 μg/L, P < 0.0052) to within the normal body iron store range levels. In two cases, normalisation was achieved within a year. Deferiprone monotherapy was sufficient thereafter in maintaining normal range cardiac (G mean ± SD = 31.4 ± 5.25 ms, P < 0.79) and liver (G mean ± SD = 26.2 ± 12.4 ms, P < 0.58) T2* and normal serum ferritin (G mean ± SD = 150.7 ± 159.1, μg/L, P < 0.17) in five of the seven patients. No serious toxicity was observed.

CONCLUSION

  Transfusional iron overload in patients with thalassaemia could be reduced to normal body iron range levels using effective deferiprone/deferoxamine combinations. These levels could be maintained using deferiprone monotherapy.

Radiographic and MRI Features of Deferiprone-Related Arthropathy of the Knees in Patients with β-Thalassemia

OBJECTIVE

This study was undertaken to describe the radiographic and MRI appearances of arthropathy of the knees in 14 patients with beta-thalassemia major undergoing chelation therapy with deferiprone (L1).

MATERIALS AND METHODS

All available radiographs and MRI studies of the knees in 14 beta-thalassemia major patients (mean age, 16.3 years; age range, 7-33 years) undergoing chelation therapy with L1 were retrospectively assessed for changes in the synovium, cartilage, and bone. Imaging findings and signs of knee arthropathy were correlated with chelation therapy and average serum ferritin concentration.

RESULTS

Nine (64%) of the 14 patients developed arthralgia of the knees during treatment with L1. Abnormal imaging findings were present in all symptomatic and two asymptomatic patients (12/14, 86%) and included joint effusion, subchondral bone irregularity, and patellar beaks. Additional MRI findings were thickening and enhancement of the synovium; hypointense bands in the synovium; irregularly thickened epiphyseal and articular cartilage overlying subchondral bone defects; and, on T2-weighted sequences, hyperintense articular cartilage lesions. The degree of knee symptoms at the time of imaging did not reflect the severity of cartilage and subchondral bone changes.

CONCLUSION

Radiologic changes can be seen in L1-related arthropathy and should be recognized. MRI of the knees should be considered in symptomatic children and young adults with thalassemia undergoing L1 chelation therapy for iron overload.

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.

An investigation into variability in the therapeutic response to deferiprone in patients with thalassemia major

Data suggest a large variability in the effectiveness of the orally active iron chelator, deferiprone, in inducing a sustained decrease in body iron to concentrations compatible with the avoidance of complications from iron overload. We analyzed 19 patients with thalassemia major who were undergoing long-term therapy with deferiprone (75 mg/kg/day every 8 hours). In seven of the 19 patients, hepatic iron concentration had been reduced or maintained at less than 7 mg/g of dry weight liver tissue, associated with no evidence of iron-induced toxicity (group A). In the remaining 12, hepatic iron concentration had either stabilized at higher than 7 mg/g of dry weight liver tissue, or increased to such concentrations during therapy with deferiprone (group B). We studied in these patients determinants that may explain such variability, including initial hepatic iron concentrations, compliance, transfusion index, pharmacokinetic characteristics of deferiprone, and plasma vitamin C status. Patients in group B showed significantly decreased plasma vitamin C concentrations compared with those in group A, who demonstrated normal levels (0.04 mg/dl [0.04-0.19 mg/dl] and 0.62 mg/day [0.44-1.05 mg/day], respectively; p = 0.02). A significant difference in apparent volume of distribution (Vd/F) had developed between the groups over time, with a higher Vd/F in group B (1.66 [0.681, group A] and 3.16 [0.811, group B]; p = 0.006). Group B had started with hepatic iron concentrations that were significantly higher than those of group A, a difference that became more pronounced over time. In the initial analysis, serum ferritin concentrations were also higher in group B. The two groups did not differ in the remaining factors. The initial hepatic iron concentrations predicted the slope of change in this value. Regression analysis suggested that patients with initial hepatic iron concentration of less than or equal to 7.22 mg/g of dry weight liver tissue are unlikely to further decrease while taking deferiprone 75 mg/kg/day. Vitamin C deficiency developed in patients in group B over time. Vitamin C is an important biologic cofactor that plays a role in the distribution of iron. The trend of increase in Vd/F of deferiprone over time may imply a compartment shift of iron stores to one less accessed by deferiprone. This study confirmed the effectiveness of deferiprone in heavily iron-loaded patients and provided evidence that its effectiveness decreases in proportion to liver iron load.

Oral iron chelation with deferiprone

Deferiprone is the most widely studied oral iron chelator and, at present, the only one shown to be effective in achieving negative iron balance in long-term clinical trials for chronic iron overload. Because of its adverse effects (e.g., agranulocytosis and arthropathy) its use is presently restricted to clinical trials and to countries where desferrioxamine is unavailable. Deferiprone was licensed for clinical use in India in 1995. Clinical trials are in progress in many centers worldwide that will provide further information on the long-term effectiveness of deferiprone as well as on the incidence of serious adverse effects in patients with iron overload. Trials of combined use of deferiprone and desferrioxamine are also in progress. In the meantime, deferiprone is an acceptable alternative for patients who cannot use desferrioxamine because of serious adverse effects, lack of compliance, or unavailability. Elucidation of the mechanisms involved in the agranulocytosis and arthropathy associated with deferiprone is still needed, as are methods to predict individual susceptibility to these adverse effects and ways of preventing them. In addition, new indications for iron-chelating therapy are continuously being explored.