Oral iron chelators

Iron; Benefits or threatens (with emphasis on mechanism and treatment of its poisoning)

Iron is a necessary biological element and one of the richest in the human body, but it can cause changes in cell function and activity control. Iron is involved in a wide range of oxidation - reduction activities. Whenever iron exceeds the cellular metabolic needs, its excess causes changes in the products of cellular respiration, such as superoxide, hydrogen peroxide and hydroxyl. The formation of these compounds causes cellular toxicity. Lack of control over reactive oxygen species causes damages to DNA, proteins, and lipids. Conversely, superoxide, hydrogen peroxide and hydroxyl are reactive oxygen species, using antioxidants, restoring DNA function, and controlling iron stores lead to natural conditions. Iron poisoning causes clinical manifestations in the gastrointestinal tract, liver, heart, kidneys, and hematopoietic system. When serum iron is elevated, serum iron concentrations, total iron-binding capacity (TIBC) and ferritin will also increase. Supportive care is provided by whole bowel irrigation (WBI), esophagogastroduodenoscopy is required to evaluate mucosal injury and remove undissolved iron tablets. The use of chelator agents such as deferoxamine mesylate, deferasirox, deferiprone, deferitrin are very effective in removing excess iron. Of course, the combined treatment of these chelators plays an important role in increasing iron excretion, and reducing side effects.

Model-Based Optimisation of Deferoxamine Chelation Therapy

Purpose

Here we show how a model-based approach may be used to provide further insight into the role of clinical and demographic covariates on the progression of iron overload. The therapeutic effect of deferoxamine is used to illustrate the application of disease modelling as a means to characterising treatment response in individual patients.

Methods

Serum ferritin, demographic characteristics and individual treatment data from clinical routine practice on 27 patients affected by β-thalassaemia major were used for the purposes of this analysis. The time course of serum ferritin was described by a hierarchical nonlinear mixed effects model, in which compliance was parameterised as a covariate factor. Modelling and simulation procedures were implemented in NONMEM (7.2.0).

Results

A turnover model best described serum ferritin changes over time, with the effect of blood transfusions introduced on the ferritin conversion rate and the effect of deferoxamine on the elimination parameter (Kout) in a proportional manner. The results of the simulations showed that poor quality of execution is preferable over drug holidays; and that independently of the compliance pattern, the therapeutic intervention is not effective if >60% of the doses are missed.

Conclusions

Modelling of ferritin response enables characterisation of the dynamics of iron overload due to chronic transfusion. The approach can be used to support decision making in clinical practice, including personalisation of the dose for existing and novel chelating agents.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-015-1805-0) contains supplementary material, which is available to authorised users.

Safety of deferasirox: a retrospective cohort study on the risks of gastrointestinal, liver and renal events

BACKGROUND

Deferasirox (DFX) is an effective and well-tolerated oral iron chelator elevating the adherence to iron chelating therapy among patients with iron overload. However, the US Food and Drug Administration issued a warning about the potential adverse events associated with DFX in 2010.

METHODS

To examine the risks of gastrointestinal (GI) bleeding, acute liver necrosis, and acute renal failure among DFX users compared with desferrioxamine (DFO) users in a real-world setting, first-time users of DFX or DFO between 2005 and 2008 in Taiwan's National Health Insurance database were observed in this population-based retrospective cohort study. The risks of different adverse events were individually analyzed by Cox proportional hazards models and adjusted by age, sex, concomitant medications, and prior medical conditions.

RESULTS

Deferasirox users had the highest incidence rates of GI bleeding (2.03 per 10 000 patient-days), acute liver necrosis (0.26 per 10 000 patient-days) and acute renal failure (1.45 per 10 000 patient-days) compared with other iron chelator users. Compared with DFO users, DFX users were not associated with the risk of GI bleeding (adjusted HR 1.03, 95% CI 0.61-1.74, p = 0.90) and the risk of acute liver necrosis (adjusted HR 2.13, 95% CI 0.49-9.33, p = 0.32). The association between DFX use and acute renal failure was found to be statistically significant (HR 2.18, 95% CI 1.18-4.02, p = 0.01; adjusted HR 2.41, 95% CI 1.27-4.58, p = 0.01).

CONCLUSION

In this study, we found statistically significant higher risk of acute renal failure and non-statistically significant higher risk of GI bleeding and acute liver necrosis associated with DFX use. More researches are warranted to evaluate the association between DFX use and potential adverse events.

Synthetic and natural iron chelators: therapeutic potential and clinical use

Iron-chelation therapy has its origins in the treatment of iron-overload syndromes. For many years, the standard for this purpose has been deferoxamine. Recently, considerable progress has been made in identifying synthetic chelators with improved pharmacologic properties relative to deferoxamine. Most notable are deferasirox (Exjade(®)) and deferiprone (Ferriprox(®)), which are now available clinically. In addition to treatment of iron overload, there is an emerging role for iron chelators in the treatment of diseases characterized by oxidative stress, including cardiovascular disease, atherosclerosis, neurodegenerative diseases and cancer. While iron is not regarded as the underlying cause of these diseases, it does play an important role in disease progression, either through promotion of cellular growth and proliferation or through participation in redox reactions that catalyze the formation of reactive oxygen species and increase oxidative stress. Thus, iron chelators may be of therapeutic benefit in many of these conditions. Phytochemicals, many of which bind iron, may also owe some of their beneficial properties to iron chelation. This review will focus on the advances in iron-chelation therapy for the treatment of iron-overload disease and cancer, as well as neurodegenerative and chronic inflammatory diseases. Established and novel iron chelators will be discussed, as well as the emerging role of dietary plant polyphenols that effectively modulate iron biochemistry.

Clinical consequences of iron overload from chronic red blood cell transfusions, its diagnosis, and its management by chelation therapy

Iron overload from chronic transfusion therapy can be extremely toxic. Excess transfusional iron is deposited in the liver, heart, and other organs as free iron, which can cause organ dysfunction and damage over time. Increased awareness of the risk of iron overload in patients requiring chronic transfusion therapy is needed, and such patients should be screened for hyperferritinemia. Those with serial serum ferritin levels exceeding 1000 ng/mL and a total infused red blood cell volume of 120 mL/kg of body weight or more should be treated with chelation therapy and then monitored to ensure that treatment adequately reduces iron levels.