Current and Future Therapies for β-Thalassaemia: A Review Article

This article will review recent and forthcoming advances in the treatment of thalassaemia. Prognosis of thalassaemia has dramatically improved in the last 50 years with the development of regular and safe blood transfusions and iron chelation. Almost 20 years ago, development of oral chelators, and more recently the improvement in the knowledge and understanding of iron pathophysiology, have led to optimal iron toxicity prevention and treatment. These considerable advancements in medical therapy have transformed transfusion-dependent thalassaemia from a lethal childhood disease to a chronic disease with an open prognosis, even in those individuals over 50 years of age, and with the disease being, in some instances, curable. In the 1980s, the introduction of allogeneic haematopoietic cell transplantation provided the possibility of curing the congenital disease for the first time. More recent developments include an improved understanding of erythropoiesis, which led to the development of new erythroid-stimulating factors effective in thalassaemia, an expansion of donor pull for transplantation, and the approach of the long-term promised gene therapy in clinical practice. Moreover, ongoing trials of gene editing and agents modulating iron metabolism promise new improvements. Today, patients with thalassaemia have several weapons in their therapeutic arsenal and, hopefully, will have much more to come. As usual in medical practice, new advancements provide new challenges for the medical community, and it is the duty of this community to clearly understand the benefits and challenges of any new approach in order to provide the highest clinical benefit to patients.

Comparison of Compliance of Different Iron Chelators Including Original and Bioequivalents of Deferasirox

Objective: The current iron chelation therapy regimens include deferoxamine (DFO), deferiprone (DFP), and deferasirox (DFX) in transfusion-dependent patients. Compliance with iron-chelating therapy is one of the significant determinants of mortality and morbidities related to iron loading in chronically transfused patients. This survey aims to compare the compliance and the satisfaction of DFO, DFP, and DFX formulations in patients who have iron-overloading in three hematology centers from Turkey. Moreover, bioequivalent (generic) formulations of dispersible DFX tablet compared with the original formulation in terms of taste and treatment compliance. Patients and Methods: A written questionnaire with a list of pre-set questions was applied to measure patient-reported outcomes to a total of 85 patients, where 77 had beta-thalassemia major, 7 had beta-thalassemia intermedia, and 1 had sickle cell anemia diagnoses. Results: The patients’ median age at enrollment was 15 years (range 7 – 42). The compliance was below 50% in 8 (18.6%), 4 (16%), and 5 (6.7%) in patients receiving DFO, DFP, and DFX, respectively. Additionally the compliance was below 80% in 16 (37.2%), 9 (36%), and 17 (22.6%) in patients receiving DFO, DFP, and DFX, respectively. It was found that 39 (47%) patients had compliance problems due to the dispersible DFX tablet formulations’ taste, except combination therapies. There was no difference between the currently used oral chelators in terms of taste and treatment compliance. Conclusion: This study draws attention to compliance problems in patients with iron-loading anemias, partly due to the unpleasant taste of DFX. Improving patient satisfaction and compliance with iron-chelator therapy may reduce complications of iron overload.

Neutropenia in Children Treated with Deferiprone or Deferasirox: A Report of the Largest Randomized Trial of Oral Chelators in Transfusion-Dependent Pediatric Patients

Introduction: Agranulocytosis/severe neutropenia is an established adverse event during deferiprone (DFP) use. Less is known about milder episodes, which are frequently transient despite continuous deferiprone use. To provide further insight into this topic, we compared the incidence of neutropenia during DFP or deferasirox (DFX) treatment in the randomized Deferiprone Evaluation in Paediatrics (DEEP-2) trial, where blood neutrophil count was regularly monitored in patients randomized to be treated with DFP or DFX. Methods: DEEP-2 was a multicenter, randomized, 12-month, open-label trial comparing DFP vs DFX in pediatric (<18 years old) patients with transfusion-dependent hemoglobinopathies. 390 patients from 22 centers in 7 countries were randomized (1:1 DFP:DFX) and received at least one dose of the study medication (193 on DFP and 197 on DFX). Neutrophil count was regularly assessed every 7 +/-7 days in all patients. Neutrophil counts <500/mm3 were classified as agranulocytosis/severe neutropenia, 500 - <1,000 /mm3 as moderate neutropenia, and 1,000 - <1,500 /mm3 as mild neutropenia. The incidence of neutrophil counts below the threshold of neutropenia (1,500/mm3) and the rate of reported episodes of neutropenia as identified by the treating physician were compared between the two treatments. An ANOVA model was used to compare the time to neutropenia and time for its resolution between the two treatment groups. To compare the cumulative hazard curves was used the Kaplan-Meier log rank test. Results: 3579 and 4027 neutrophil counts were available for DFP- and DFX-treated patients, respectively. 47 (1.3%) of the total counts in 24 (12.4%) of the 193 DFP-treated patients versus 48 (1.2%) of the total counts in 27 (13.7%) of the 197 DFX-treated patients were below 1,500/mm3. Of these, 28 cases in 23 DFP-treated patients and 15 cases in 11 DFX-treated patients were reported by the treating physician as neutropenia, corresponding to a global incidence rate 11.9% for DFP and 5.6% for DFX (p=0.081, Chi-Square test). 23 (82.1%) of the 28 episodes of neutropenia during DFP use were considered drug related vs 2 (13.3%) of the 15 episodes during DFX use (p-value < 0.001, Fisher Exact test) (table 1). The mean (SD) treatment duration with either DFP or DFX prior to diagnosis of mild or moderated neutropenia was 127 (96.1) days and 101 (85.7) respectively. All those episodes, except for 2, resolved within a mean time of 13 days (1 - 42 days) in DFP-treated patients and 18 days (6 - 46 days) in DFX-treated patients. The 2 cases where neutropenia did not resolve were diagnosed as constitutional neutropenia and bone marrow suppression. There was no significant difference in those results between the two treatment groups as assessed by one-way ANOVA(p = 0.379), Log-Rank test (p = 0.065) or cumulative-hazard and Kaplan-Meier. During the study 3 events of agranulocytosis occurred, all in patients treated with DFP and not included in the present analysis. All 3 episodes resolved. Conclusion: Data from the largest randomized trial of oral chelators in transfusion-dependent pediatric patients provide evidence that, a drop in the neutrophil count below the threshold for mild neutropenia is very common (>10% of patients) for both DFP and DFX treated patients. All episodes of neutropenia, except for 2 with specific etiology, resolved, irrespective of their severity and of chelator used. A causal relationship of neutropenia to chelator use varied based on the chelator; the majority of events observed during DFP use were assessed by the clinician as drug related, whereas the majority of events observed during DFX use were assessed unrelated to its use. These data indicate that while agranulocytosis rate in DFP patients is not changed from previous reports, moderate/mild neutropenia represent discrete events in patients undergoing oral iron chelation therapy. Disclosures Tricta: ApoPharma: Employment. Della Pasqua:GlaxoSmithKline: Employment. Kattamis:Ionis: Membership on an entity's Board of Directors or advisory committees; ViFOR: Membership on an entity's Board of Directors or advisory committees; Vertex: Membership on an entity's Board of Directors or advisory committees; Apopharma: Honoraria; Celgene Corporation: Honoraria, Membership on an entity's Board of Directors or advisory committees; Novartis Oncology: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding. Reggiardo:CVBF: Consultancy. Spino:ApoPharma: Employment. Tsang:Apotex Inc.: Employment.

Treatment of iron overload syndrome: a general review

SUMMARY INTRODUCTION Iron overload is a broad syndrome with a large spectrum of causative etiologies that lead to iron deposition. When iron exceeds defenses, it causes oxidative damage and tissular disfunction. Treatment may prevent organ dysfunction, leading to greater life expectancy. METHODS Literature from the last five years was reviewed through the use of the PubMed database in search of treatment strategies. DISCUSSION Different pharmacological and non-pharmacological strategies are available for the treatment of iron overload and must be used according to etiology and patient compliance. Therapeutic phlebotomy is the basis for the treatment of hereditary hemochromatosis. Transfusional overload patients and those who cannot tolerate phlebotomy need iron chelators. CONCLUSION Advances in the understanding of iron overload have lead to great advances in therapies and new pharmacological targets. Research has lead to better compliance with the use of oral chelators and less toxic drugs.

Modeling Combination Chelation Regimes To Optimize Cellular Iron Removal and Explore Mechanisms Of Enhanced Chelation

Introduction Monotherapy with clinically available chelators, namely deferoxaime (DFO), deferasirox (DFX) or deferiprone (DFP) is effective but often slow and suboptimal. Combinations of DFO with DFP have been used clinically to enhance cellular iron mobilization but the conditions under which this occurs have not been studied systematically. With the emergence of DFX, the possibility exists to combine this with either DFO or DFP to enhance chelation. We have developed a system to study the optimal concentrations and times of exposure to these chelators, alone or in combination for maximising cellular iron removal. Isobol modeling has been used to determine whether interaction is additive or synergistic. The demonstration of synergy would imply the primary chelator acting as a ‘sink’ for iron chelated and donated to this sink by low concentrations of a secondary ‘shuttle’ chelator as shown in plasma (Evans et al. TransL. Res, 2010). Methods Human hepatocellular carcinoma (HuH-7) cells were chosen as hepatocytes are the major cell of iron storage in iron overload. Iron concentration was determined using the ferRozine (Riemer et al. Anal Biochem. 2004). A threefold increase of intracellular iron compared to control was obtained by serially treating cells with 10% FBS RPMI media. The cells were then exposed to iron chelator then lysed and intracellular iron concentration determined via the ferrozine assay, normalized against protein content. Cell viability was assessed using 0.4% Trypan blue as well as Acridine Orange /Propidium Iodide and was consistently > 98%. Isobolograms were constructed (Tallarida et al, Pharmacol Ther, 2010) as well as a the synergy index (QUOTE 1-1/R) x 100 (%), where R = difference of areas between the line of additivity and the curve of synergy on the isobologram. This index represents how much of the obtained effect exceeds that expected by additivity of two chelators. Results Monotherapy with DFP, DFX or DFO at clinically relevant concentrations of 1 to 30µM iron binding equivalents (IBE), induced both dose and time dependent cellular iron removal. Dual therapy combinations of all 3 chelators enhanced iron removal at 4, 8 and 12 hours. At 4 hours of incubation, whereas 10µM DFO alone had no demonstrable effect on cellular iron removal, addition of DFP at as little as 1µM IBE increased cellular iron removal. Table 1 shows examples of cellular iron removal at specimen chelator concentrations alone or in combination at 8h. The combination of DFX with DFO, DFX with DFP and DFP with DFO all resulted in enhanced cellular iron removal. The combination of DFP and DFX was the most effective. Isobol plot analysis from multiple chelator concentrations demonstrated synergy for all pairs at 4 and 8 hours of exposure. The derived synergy index at 8h indicates that when DFX and DFO are combined, 49% of the chelation effect is due to synergy in this system and 51% in the case of DFP and DFO combination. Most interestingly, the synergistic effect is even greater, in the case of the two oral chelators DFP and DFX when in combination (59%). Figure 1. Conclusion Remarkably low concentrations of a second chelator are required to enhance cellular iron removal by the primary chelator. Isobol analysis shows synergy rather than additivity as the mechanism for enhanced chelation for all 3 combinations, implying a ‘shuttle’ and ‘sink’ effect. Interestingly, the combination of two oral chelators DFP and DFX showed the most marked enhancement of cellular iron removal, without cellular toxicity, suggesting a potentially powerful therapeutic approach, provided this is also well tolerated clinically. The long plasma half life of once daily oral DFX will allow a continuous ‘sink’ for iron shuttled by the shorter acting DFP. Line of Additivity Curve of Synergy below the line Disclosures: Porter: Novartis: Consultancy, Honoraria, Research Funding; Shire: Consultancy, Honoraria; Celgene: Consultancy.