Transport of 14C-deferiprone in normal, thalassaemic and sickle red blood cells

Pattern of iron chelation therapy in Egyptian beta thalassemic patients: Mansoura University Children's Hospital experience

BACKGROUND

The simultaneous use of deferoxamine (DFO) and deferiprone (DFP) has an additive effect in iron excretion in transfusion-dependent thalassemic patients.

AIM OF THE WORK

To evaluate the efficacy and safety of a prospective alternating therapy with DFO and DFP in patients with beta-thalassemia major (TM) and increased serum ferritin with DFO monotherapy alone.

PATIENT AND METHODS

Sixty patients with beta-TM (mean age +/- SD, 13.05 +/- 6.1, range 10-20 years) with iron overload (serum ferritin > 2000 ng/ml) were studied. They received DFO at a daily dose of 40 mg/kg/day for 5-7 nights/week for the past several years. These patients were randomly assigned either to continue treatment with DFO alone (DFO group, n = 30) or prospectively receive additional alternating therapy with DFP at 75 mg/kg/day for 4 days/week and DFO for the other 2 days/week (alternating therapy group, n = 30). The efficacy of both groups was assessed by measurements of serum ferritin, echocardiography, and 24 h urine iron excretion (UIE) levels throughout 1 year follow-up.

RESULTS

In the 60 evaluable patients, the mean serum ferritin ( +/- SD) fell dramatically from 4500 ( +/- 1250) ng/ml at the start of the study to 1250 ( +/- 750) ng/ml (alternate therapy group; P < 0.001) at the end of the study. There was also a significant improvement in the myocardial function as assessed by the ejection fraction (P < 0.002) and fractional shortening (P < 0.01) in those patients on alternate therapy for 1 year. Their mean urinary iron excretion elevated from 0.41 +/- 0.27 to 0.76 +/- 0.49 mg/kg/24 h (P < 0.003). There was a significant difference between both groups as regard the studied parameters at the end of the study. Whereas, there was no statistical difference as regard the studied parameters at the start and the end of the study in the DFO group. No significant adverse effects had occurred in both groups that necessitated withdrawal from the study.

CONCLUSIONS

beta-Thalassemic major patients with transfusional iron overload can be safely and effectively treated with an alternate therapy of DFO/DFP with a progressive fall in the mean serum ferritin and significant improvement of myocardial performance.

Iron mobilization using chelation and phlebotomy

Knowledge of the basic mechanisms involved in iron metabolism has increased greatly in recent years, improving our ability to deal with the huge global public health problems of iron deficiency and overload. Several million people worldwide suffer iron overload with serious clinical implications. Iron overload has many different causes, both genetic and environmental. The two most common iron overload disorders are hereditary haemochromatosis and transfusional siderosis, which occurs in thalassaemias and other refractory anaemias. The two most important treatment options for iron overload are phlebotomy and chelation. Phlebotomy is the initial treatment of choice in haemochromatosis, while chelation is a mainstay in the treatment of transfusional siderosis. The classical iron chelator is deferoxamine (Desferal), but due to poor gastrointestinal absorption it has to be administered intravenously or subcutaneously, mostly on a daily basis. Thus, there is an obvious need to find and develop new effective iron chelators for oral use. In later years, particularly two such oral iron chelators have shown promise and have been approved for clinical use, namely deferiprone (Ferriprox) and deferasirox (Exjade). Combined subcutaneous (deferoxamine) and oral (deferiprone) treatment seems to hold particular promise.

Optimal management strategies for chronic iron overload

Iron overload is characterised by excessive iron deposition and consequent injury and dysfunction of target organs, especially the heart, liver, anterior pituitary, pancreas and joints. Iron overload disorders are common worldwide and occur in most major race/ethnicity groups. Physiological mechanisms to excrete iron are very limited. Thus, all patients with iron overload need safe and effective treatment that is compatible with their co-existing medical conditions. Treatments for iron overload include phlebotomy and erythrocytapheresis that remove iron predominantly as haemoglobin, and chelation therapy with drugs that bind excess iron selectively and increase its excretion. The most important potential benefits of therapy are preventing deaths due to cardiac siderosis and hepatic cirrhosis. Preventing iron-related injury to endocrine organs is critical in children. Successful treatment or prevention of iron overload increases quality of life and survival in many patients. This article characterises the major categories of iron overload disorders, tabulates methods to evaluate and treat iron overload, and describes treatment options for iron overload disorders. Research needed to advance knowledge about treatment of iron overload is proposed.

Iron chelation treatment with combined therapy with deferiprone and deferioxamine: a 12-month trial

The simultaneous use of deferioxamine (DFO) and deferiprone (DFP) has an additive effect in iron excretion in transfusion-dependent thalassemic patients. In a prospective study, we evaluated the safety and effectiveness of combined therapy with these two chelators. Fifty patients with beta-thalassemia were uniformly treated with DFP for 4 days per week and combined therapy with DFP and DFO for 3 days of the week. Efficacy was evaluated by ferritin and cardiac shortening fraction (SF). Hepatic hemosiderosis was also assessed by estimation of the T2 relaxation time by magnetic resonance in a subgroup of patients. Forty-three patients completed 1 year of therapy. Mean ferritin decreased from 3363.7 +/- 2144.5 microg/L to 2323.2 +/- 1740.8 microg/L (P < 0.0001). The reduction was significant even in the group of patients with ferritin <2500 microg/L. Significant improvement in T2 relaxation and SF was observed. The most common adverse events were gastrointestinal symptoms (20%) and transaminasemia (18%). The rate of agranulocytosis was 4.2 cases per 100 patient-years. Prolonged use of combined therapy with DFP and DFO is effective in decreasing iron load and improving cardiac function. Its possible association with higher incidence of agranulocytosis emphasizes the need for close monitoring.

Combined Therapy with Deferoxamine and Deferiprone

Therapy with either deferiprone (DFP) or deferoxamine (DFO) is inadequate in achieving negative iron balance in many patients with thalassemia. There are mounting theoretical, experimental, and clinical evidences of increased efficacy when therapy includes both chelating agents. DFP and DFO chelate excess iron in different ways without affecting each other's metabolism. When both chelators are administered simultaneously, they interact either in an additive or synergistic manner, probably through "shuttling" iron from DFP to DFO. Iron-balance studies have shown that the use of both agents on the same day can induce negative iron balance in all patients. Long-term combined therapy with DFO with DFP results in considerable reduction of both ferritin levels and liver iron concentration as well as significant improvement in cardiac siderosis and function. This therapeutic regimen is well tolerated and safe, even though it may be related to a small increase in the incidence of agranulocytosis compared with DFP monotherapy. Apart from using both agents simultaneously, sequential administration of DFP and DFO has also shown promising results. Combining the available iron chelators offers many therapeutic options that can be tailored to each patient individually. It is an exciting advance in treating hemosiderosis in thalassemic patients.

Deferiprone: New Insight

Recent results from independent studies suggest that deferiprone is more cardioprotective than deferoxamine. Patients on long-term treatment with deferiprone have a better myocardial magnetic resonance imaging pattern and less chance to develop a new cardiac disease or worsen an existing one. Most of these observations are retrospective and require confirmation from randomized controlled trials. Other new observations regard the effects of combining the two chelators. Most results indicate an additional effect on iron excretion and a significant reduction of the time required to mitigate severe iron overload and to reverse clinical heart disease. Again, these data require confirmation, as they were mostly obtained on individual cases or small groups of patients treated with a wide range of combinations of the two chelators, but the univocity of results is impressive. After many years of controversy, deferiprone is emerging as a useful oral iron chelator that enhances the chances for the patient to have optimal treatment. Well-designed and -conducted studies will help in answering the questions still open.

Deferiprone as an oral iron chelator in sickle cell disease

Iron overload is not uncommon in sickle cell disease (SCD) and requires regular chelation therapy in several instances. The present study evaluates the effect of deferiprone in 15 adult patients with SCD (ten beta(s)/beta(0)thalassemia and five beta(s)/beta(s)) and iron overload. Deferiprone was given at a dose of 75 mg/kg daily for 12 months. The evaluation considered pre- and post-treatment values of serum ferritin, urinary iron excretion, and T2 values of liver and heart obtained by magnetic resonance imaging (MRI). Eleven patients had a liver biopsy prior to starting therapy to evaluate iron concentration (LIC). Twelve patients completed the study with satisfactory compliance. In ten of them (83.3%) the serum ferritin levels decreased significantly at the end of the trial; in eight patients (66.6%) the reduction of serum ferritin was accompanied by a significant increase of their liver T2 values. All patients had a significant increase of urinary iron excretion in response to the drug. Ferritin levels and liver T2 values correlated with liver iron concentration; on the contrary, ferritin levels and liver T2 values failed to show any correlation with heart T2 values. Heart T2 values did not also show any correlation with left ventricular ejection fraction. Deferiprone was well tolerated and did not cause any significant adverse effects. These results suggest that deferiprone may effectively decrease the iron deposition in patients with SCD; moreover, T2 MRI proves to be a reliable and rapid, noninvasive method for assessing the liver iron load in patients with SCD.

New Strategies in the Treatment of the Thalassemias

In addition to the severe beta thalassemias, hematologists have begun to recognize the more severe forms of alpha thalassemia, namely hemoglobin (Hb) H disease and Hb H/Hb Constant Spring, as well as the beta compound heterozygote, beta thalassemia/HbE. Clinically, variably severe anemia becomes apparent in the first year accompanied by occasionally massive expansion of erythropoiesis. The most anemic patients require regular red blood cell transfusions to avoid death from cardiac failure. However, the inevitable iron accumulation leads to dysfunction, primarily involving the heart, liver, and endocrine system; thus, regularly transfused patients require iron chelation. A major discovery was that allogeneic bone marrow (stem cell) transplantation in severely affected subjects with both alpha and beta thalassemia could result in cure. Current work deals with specific complications, such as iron overload and endocrine, cardiopulmonary, thrombophilic, and osteopenic problems. The thalassemias are likely to benefit in the future from specific gene therapy. There are also important advances in genetic counseling based on results of early fetal diagnosis.

Clinical trial of deferiprone iron chelation therapy in beta-thalassaemia/haemoglobin E patients in Thailand

Nine patients with either beta-thalassaemia/haemoglobin E (7) or homozygous beta-thalassaemia (2) not requiring regular transfusions were treated with the oral iron chelator, deferiprone 25-50 mg/kg/d for between 17 and 86 weeks (mean 49 weeks). There were significant decreases in serum ferritin (initial mean +/- standard deviation 2168 +/- 1142, final 418 +/- 247 micro g/l; t-test for paired samples, P = 0.005), hepatic iron (initial 20.3 +/- 6.26, final 11.7 +/- 4.83 mg/g/dry weight; P = < 0.02), red cell membrane iron (initial 76.2 +/- 3.64, final 7.2 +/- 0.56 mmol/mg protein; P = < 0.0005) and serum non-transferrin bound iron (initial 9.0 +/- 0.56, final 5.9 +/- 0.89 micro mol/l; P = < 0.0005). There was also a significant rise in serum erythropoietin (initial 240 +/- 195.1, final 433.2 +/- 269.2 U/l; P = 0.034). The haemoglobin level rose in three patients and transfusion requirements were reduced substantially in four patients. Serum thiobarbituric acid reactive substance (TBARS) also fell in six of eight patients. Patients generally improved clinically, with weight gain observed. Side-effects were mild and included gastrointestinal symptoms (6) and arthralgia (1), not requiring withdrawal of the drug. One patient died at 17 weeks of therapy as a result of an intercurrent infection. His neutrophil count was normal. We conclude that deferiprone is an effective, well-tolerated iron chelator for patients with thalassaemia intermedia. Further studies are needed to determine the optimum dose and length of treatment needed to reduce iron burden to a safe level in these patients.