Agranulocytosis in a patient with thalassaemia major during treatment with the oral iron chelator, 1,2-dimethyl-3-hydroxypyrid-4-one

A Case of Fatal Agranulocytosis That Developed in a Patient with β-Thalassemia Major Treated with Deferiprone

A 29-year-old male with transfusion-dependent β-thalassemia major (β-TM), splenectomized and on chelation therapy with deferiprone (DFP or L1) due to heart and liver hemosiderosis, presented with high fever and agranulocytosis. Deferiprone was discontinued and a broad spectrum antibiotic therapy was started intravenously. The patient remained febrile and showed no recovery of neutrophil count even after the initiation of granulocyte colony-stimulation factor (G-CSF). After 12 days at the hospital, he developed respiratory failure and was transferred to the intensive care unit (ICU) where he developed multi-organ failure and died 3 days later. To investigate the mechanism of agranulocytosis, bone marrow mononuclear cells of a healthy volunteer were plated on culture dishes, with or without the patient's serum. The observation of colony forming units of progenitor cells in dishes that contained the patient's serum, provided inconclusive explanation of the possible mechanism of DFP-induced agranulocytosis. This is a case of fatal agranulocytosis developing in a patient being treated with DFP, a well recognized but rare complication of this drug. Further studies are required in order to elucidate the possible pathogenic mechanism of agranulocytosis due to DFP and to provide clear guidelines in order to best care for the patient.

Safety profiles of iron chelators in young patients with haemoglobinopathies

BACKGROUND

This review describes the safety of deferoxamine (DFO), deferiprone (DFP), deferasirox (DFX) and combined therapy in young patients less than 25 yr of age with haemoglobinopathies.

METHODS

Searches in electronic literature databases were performed. Studies reporting adverse events associated with iron chelation therapy were included. Study and reporting quality was assessed using AHRQ Risk of Bias Assessment Tool and McMaster Quality Assessment Scale of Harms. Prospective clinical studies were pooled in a random-effects meta-analysis of proportions.

RESULTS

Safety data of 2040 patients from 34 studies were included. Ninety-two case reports of 246 patients were identified. DFX (937 patients) and DFP (667 patients) possess the largest published safety evidence. Fewer studies on combination regimens are available. Increased transaminases were seen in all regimens (3.9-31.3%) and gastrointestinal disorders with DFP and DFX (3.7-18.4% and 5.8-18.8%, respectively). Therapy discontinuations due to adverse events were low (0-4.1%). Reporting quality was selective and poor in most of the studies.

CONCLUSION

Iron chelation therapy is generally safe in young patients, and published data correspond to summary of product characteristics. Each iron chelation regimen has its specific safety risks. DFO seems not to be associated with serious adverse effects in recommended doses. In DFP and DFX, rare, but serious, adverse reactions can occur. Data on combined therapy are scarce, but it seems equally safe compared to monotherapy.

Deferiprone-induced agranulocytosis: 20 years of clinical observations

Use of the iron chelator deferiprone for treatment of iron overload in thalassemia patients is associated with concerns over agranulocytosis, which requires weekly absolute neutrophil counts (ANC). Here, we analyze all episodes of agranulocytosis (n = 161) and neutropenia (n = 250) during deferiprone use in clinical trials (CT) and postmarketing surveillance programs (PMSP). Rates of agranulocytosis and neutropenia in CT were 1.5% and 5.5%, respectively. Of the agranulocytosis cases, 61% occurred during the first 6 months of therapy and 78% during the first year. These events appeared to be independent of dose, and occurred three times more often in females than males. Their duration was not significantly shortened by use of G‐CSF. No patient with baseline neutropenia (n = 12) developed agranulocytosis during treatment, which raises questions about the validity of prior neutropenia as a contraindication to use. Only 1/7 novel neutropenia cases in CT progressed to agranulocytosis with continued treatment, indicating that neutropenia does not necessarily lead to agranulocytosis. The agranulocytosis fatality rate was 0% in CT and 15/143 (11%) in PMSP. Rechallenge with deferiprone produced agranulocytosis in 75% of patients in whom the event had already occurred, and in 10% with previous neutropenia. Weekly ANC monitoring allows early detection and interruption of therapy, but does not prevent agranulocytosis from occurring. Its relevance appears to decrease after the first year of therapy, when agranulocytosis occurs less often. Based upon analysis of data collected over the past 20 years, it appears that patient education may be the key to minimizing agranulocytosis‐associated risks during deferiprone therapy. Am. J. Hematol. 91:1026–1031, 2016. © 2016 The Authors. American Journal of Hematology Published by Wiley Periodicals, Inc.

Deferiprone-Induced Agranulocytosis : A Critical Review of Five Rechallenged Cases

The most serious adverse effect of deferiprone, the first orally active iron chelator, is agranulocytosis afflicting an estimated 1.6% of patients. Among the 13 reported patients who had experienced deferiprone-induced agranulocytosis or severe neutropenia, 5 were rechallenged. We studied the onset, clinical and rechallenge course of all 5 patients in an attempt to characterise the mechanisms involved in deferiprone-induced agranulocytosis, to verify whether rechallenge in future patients is ethically justified. Deferiprone-induced agranulocytosis showed no trend of dose dependency: of all patients who had experienced agranulocytosis 23% were treated with 50 mg/kg/day, 46% with 75 to 90 mg/kg/day, and 31 % with > 90 mg/kg/day. Available data including bone marrow aspiration in some patients support the hypothesis that an early myeloid precursor is the target cell affected by deferiprone. All 5 rechallenged patients re-experienced agranulocytosis/neutropenia. The lag period to agranulocytosis/neutropenia following reinduction was significantly shorter (13.2 ± 21.7 weeks compared with 46.4 ± 14.2 weeks in the first episode; p < 0.05). All but one of the rechallenged patients re-experienced agranulocytosis or neutropenia 2 to 4 weeks following re-exposure to deferiprone, suggesting a possible immune mechanism. We found that deferiprone was oxidised in vitro by hypochlorous acid, the major neutrophil oxidant to produce a myelotoxic metabolite. This reactive species demonstrated neutrophil toxicity and a dose-dependent lymphotoxic curve. However, we found no differences in the toxicity of this reactive species to neutrophils from 2 patients with a history of deferiprone-induced agranulocytosis when compared with controls. In combination with the clinical characteristics, these results suggest a reactive metabolite-induced immune-mediated reaction. These 5 rechallenged cases ethically preclude the rechallenge of additional cases.

Comparative assessment of deferiprone and deferasirox in thalassemia major patients in the first two decades-single centre experience

Iron overload is mainly responsible for the morbidity and mortality in patients with beta thalassemia major (TM). Our aim was to compare treatment outcomes with oral iron chelators, deferiprone (DFP), and deferasirox (DFX) in the first two decades on therapy. Seventy patients with TM (mean age ± SD, 7.9 ± 4.2; range 1.5-17 years) attending the pediatric day care unit for regular transfusional support were enrolled in this cross-sectional cohort study. The patients were treated either with DFP at the dose of 75-100 mg/kg/d in three divided doses after food or DFX at the dose of 25-40 mg/kg/d as single dose before food. Mean serum ferritin (±SD) was lower in patients below 10 years (n = 44) at 1283 (±600) ng/mL when compared with patients ≥10 years (n = 19) at 1546 (±589) ng/mL. There was no significant difference in mean serum ferritin (±SD) level in patients receiving DFP (1360 ± 589) versus DFX (1260 ± 641) in this cohort, P > 0.05. 67% of the patients had Vitamin D deficiency (<50 umol/L). Our results show comparable efficacy of DFP and DFX with regards to iron chelation as estimated by serial serum ferritin levels; however, MRI T2* values were higher in the DFP-treated patients compared to DFX treatment.

Iron chelation therapy in thalassemia syndromes

Transfusional hemosiderosis is a frequent complication in patients with transfusion dependent chronic diseases such as thalassemias and severe type of sickle cell diseases. As there are no physiological mechanisms to excrete the iron contained in transfused red cells (1 unit of blood contains approximately 200 mg of iron) the excess of iron is stored in various organs. Cardiomyopathy is the most severe complication covering more than 70% of the causes of death of thalassemic patients. Although the current reference standard iron chelator deferoxamine (DFO) has been used clinically for over four decades, its effectiveness is limited by a demanding therapeutic regimen that leads to poor compliance. Despite poor compliance, because of the inconvenience of subcutaneous infusion, DFO improved considerably the survival and quality of life of patients with thalassemia. Deferiprone since 1998 and Deferasirox since 2005 were licensed for clinical use. The oral chelators have a better compliance because of oral use, a comparable efficacy to DFO in iron excretion and probably a better penetration to myocardial cells. Considerable increase in iron excretion was documented with combination therapy of DFO and Deferiprone. The proper use of the three chelators will improve the prevention and treatment of iron overload, it will reduce complications, and improve survival and quality of life of transfused patients.

Agranulocyosis in Beta Thalassemia Major Patients treated with Oral Iron Chelating Agent (Deferiprone)

Deferiprone is an oral chelating agent that has been recently shown to reduce cardiac siderosis, but is also known to be associated with serious side effects like agranulocytosis which can be fatal. This report is a single centre experience of 5 cases with severe agranulocytosis in amongst 144 patients (3.47%) of thalassemia major on combined chelation therapy with subcutaneous desferrioxamine and oral deferiprone which is much higher than the previous reports.

Safety of oral iron chelator deferiprone in young thalassaemics

Deferiprone is now widely used for iron chelation in patients with thalassaemia. Studies on its efficacy and safety have largely included older children and adults.

OBJECTIVE

To assess the safety of deferiprone in children <6 yr of age.

METHODS

The study is based on scrutiny of follow-up data of 44 patients of age <6 yr receiving deferiprone for a variable period of time. Occurrence of various side effects including gastrointestinal, osteoarticular were noticed and complete blood counts were performed every 2-4 wk.

RESULTS

Nausea and vomiting were noticed in 12 (27.2%), joint symptoms were reported by four (9.1%) and neutropenia was observed in only two patients (4.5%). None of the patient had agranulocytosis. Thrombocytopenia was observed in 20 patients (45.45%), which occurred 3 months to 1 yr after deferiprone therapy. Interruption of deferiprone for 2-4 wk led to reversal of symptoms in all but two patients.

CONCLUSION

Thrombocytopenia is one of the major side effects in young thalassaemics and necessitates frequent close monitoring of blood counts but its resolution after discontinuation and absence of clinical evidence of bleeding does not preclude its use.

[Iron overload and myelodysplastic syndromes]

Transfusion of RBC units, the only current treatment for many myelodysplastic syndromes, and excess intestinal absorption of Fe related to dyserythopoiesis often result in iron overload. This condition is associated with high rates of morbidity and mortality. High-risk patients include those with refractory anemia, sideroblastic anemia, 5q-syndrome, patients with a good prognosis (low or lower intermediate international prognosis score), patients having received over 100 RBC units, and patients under the age of 70. Deferoxamine, while it can prevent iron overload, is a strenuous treatment requiring 8-to-12 hour-overnight subcutaneous injections. When patients comply with the regimen, it efficiently prevents mortality due to iron overload, but must be implemented early in the disorder, usually before transfusing 20 RBC concentrates. A simple way of monitoring iron overload is to measure seric ferritin levels and record the number of RBC concentrates. The chelating treatment should be modulated according to age, MDS type, international prognosis score, number of RBC units received, ferritin levels, and most of all, patient tolerance. The direct subcutaneous approach is currently being evaluated by the French Group for Myelodysplasias for its efficiency to prevent disorders, but seems to be both efficient and well complied with (a national protocol is under way). The recent findings on the proteins implied in iron recycling by macrophages after destruction of RBCs, may in the long term, enable us to manage patients with less burdensome treatments and more effective new oral chelates.

Safety profile of the oral iron chelator deferiprone: a multicentre study

In previous trials, the orally active iron chelator deferiprone (L1) has been associated with sporadic agranulocytosis, milder forms of neutropenia and other side-effects. To determine the incidence of these events, we performed a multicentre prospective study of the chelator. Blood counts were performed weekly, and confirmed neutropenia mandated discontinuation of therapy. Among 187 patients with thalassaemia major, the incidence of agranulocytosis (neutrophils < 0.5 x 109/l) was 0.6/100 patient-years, and the incidence of milder forms of neutropenia (neutrophils 0.5-1.5 x 109/l) was 5.4/100 patient-years. All cases of neutropenia resolved after interruption of therapy. Neutropenia occurred predominantly in non-splenectomized patients. Nausea and/or vomiting occurred early in therapy, was usually transient and caused discontinuation of deferiprone in three patients. Mild to moderate joint pain and/or swelling did not require permanent cessation of deferiprone and occurred more commonly in patients with higher ferritin levels. Mean alanine transaminase (ALT) levels rose during therapy. Increased ALT levels were generally transient and occurred more commonly in patients with hepatitis C. Persistent changes in immunological studies were infrequent, although sporadic abnormalities occurred commonly. Mean zinc levels decreased during therapy. Ferritin levels did not change in the overall group but decreased in those patients with baseline levels > 2500 microgram/l. This study characterized the safety profile of deferiprone, and, under the specific conditions of monitoring, demonstrated that agranulocytosis is less common than previously predicted.

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.

Oral iron-chelating therapy: the L1 experience

L1 is the most widely studied oral iron-chelating drug and at present the only one shown to be effective at causing negative iron balance in long-term clinical trials for thalassemia major and other transfusion-dependent refractory anaemias. Because of side-effects, both in experimental animals and in humans, its development as a widely available pharmaceutical agent has been delayed. However, for the large numbers of transfusion-dependent, iron-overloaded patients who do not use DFX because of poor compliance, adverse effects or unavailability of the drug, L1 may be a suitable alternative for iron chelation. However, its use should be restricted to Ethical Committee approved clinical trials. Patients who are capable of using DFX effectively should be encouraged to continue doing so until an oral iron chelator has been fully established for clinical use. It is hoped that 3-hydroxypyrid-4-one analogues of L1 as well as compounds related to pyridoxal isonicotinyl hydrazone, HBED or hydroxamic acid can be found both orally effective and safe for long-term administration. Current and future trials of L1 could address some of the following issues, beside extending present studies on the efficacy and adverse effects of L1: 1. The effect of administering a reduced dose of L1 (< 75 mg/kg per day) on the incidence of adverse effects and on long-term efficacy. 2. The efficacy and adverse effects of L1 at a low dose in patients with non-transfusional iron overload such as thalassaemia intermedia, primary haemochromatosis and congenital haemolytic anaemias. 3. The effect of combining oral L1 with intravenous or subcutaneous DFX on the incidence of adverse effects and efficacy. 4. Elucidation of the mechanisms involved in agranulocytosis and joint toxicity and finding methods to predict for individual susceptibility to these adverse effects and ways of preventing them.

Deferiprone-associated myelotoxicity

Agranulocytosis developed in a 63-year-old patient with myelodysplasia 6 weeks after commencing treatment with the oral iron chelator deferiprone (L1, 1,2-dimethyl-3-hydroxypyrid-4-one, CP20) at a daily dose of 79 mg/kg. This was the 3rd case of agranulocytosis (neutrophils 0 x 10(9)/l) in clinical trials of L1 at the Royal Free Hospital. The neutrophil count recovered 7 days after stopping L1 and commencing G-CSF at a dose of 300 micrograms daily. Three other patients with milder degrees of neutropenia (neutrophils < 1.5 x 10(9)/l) have also been observed in our trials. The case histories of these 4 patients are described here; other reported cases of neutropenia or agranulocytosis are reviewed. Based on worldwide long-term clinical trials the incidence of agranulocytosis is about 1.6% and of neutropenia 2%.

The effect of deferiprone (L1) and desferrioxamine on myelopoiesis using a liquid culture system

Agranulocytosis was observed in a 63-year-old patient with myelodysplasia 6 weeks after commencing chelation with the oral iron chelator deferiprone (1,2-dimethyl-3-hydroxypyrid-4-one, L1) at a daily dose of 79 mg/kg. Using a liquid culture system no difference was observed when L1 toxicity to normal and patient myelopoiesis was compared (IC50: 150 v 172 microM respectively). L1 was found to be less toxic than desferrioxamine (DFX) (IC50: 150 v 9 microM respectively) to normal myelopoiesis. Delayed addition of iron to myeloid cultures containing an inhibitory concentration of L1 or DFX was associated with reversal of chelator-induced inhibition of myelopoiesis up to 6 h but not after 24 h. Further studies are needed to determine the incidence and elucidate the pathogenesis of agranulocytosis associated with L1 therapy.

Differential toxicity of alpha-keto hydroxypyridine iron chelators and desferrioxamine to human haemopoietic precursors in vitro

Compliance with iron chelation therapy improves life expectancy in transfusion-dependent haematological disorders. However, failure of compliance with parenteral desferrioxamine (DF) therapy and the expense incurred makes this drug unavailable for most patients in the developing world. We have been evaluating the orally active iron chelator 1,2-dimethyl-3-hydroxypyrid-4-one (L1) in both preclinical and clinical trials. Five patients have developed reversible agranulocytosis during treatment with this agent. We have now studied the effects of L1, other alpha-ketohydroxypyridines and DF on bone marrow myeloid progenitors using the CFU-GM system. The results show that L1 is less toxic than DF to normal bone marrow myeloid progenitors (ID50:130 mumol/l versus 7.9 mumol/l). The L1 ID50 is within the previously reported range of peak plasma values (80-450 mumol/l). When saturating concentrations of iron were added to the cultures, the mean toxicity of all the chelators was significantly decreased over the range of doses tested, e.g. L1 ID50, 567 mumol/l; DF ID50, > 1000 mumol/l. The toxicity of L1 in vitro was similar for marrows from 3 normal donors and for the recovery marrow from a patient with thalassaemia major who had experienced agranulocytosis. Further studies are required to elucidate the mechanisms of L1-induced agranulocytosis.