Deferiprone: a review of its clinical potential in iron overload in beta-thalassaemia major and other transfusion-dependent diseases

Iron-overload-induced ferroptosis in mouse cerebral toxoplasmosis promotes brain injury and could be inhibited by Deferiprone

Iron is a trace metal element that is essential for the survival of cells and parasites. The role of iron in cerebral toxoplasmosis (CT) is still unclear. Deferiprone (DFP) is the orally active iron chelator that binds iron in a molar ratio of 3:1 (ligand:iron) and promotes urinary iron excretion to remove excess iron from the body. The aims of this experiment were to observe the alterations in iron in brains with Toxoplasma gondii (T. gondii) acute infections and to investigate the mechanism of ferroptosis in CT using DFP. We established a cerebral toxoplasmosis model in vivo using TgCtwh3, the dominant strains of which are prevalent in China, and treated the mice with DFP at a dose of 75 mg/kg/d. Meanwhile, we treated the HT-22 cells with 100 μM DFP for half an hour and then infected cells with TgCtwh3 in vitro. A qRT-PCR assay of TgSAG1 levels showed a response to the T. gondii burden. We used inductively coupled plasma mass spectrometry, an iron ion assay kit, Western blot analysis, glutathione and glutathione disulfide assay kits, a malonaldehyde assay kit, and immunofluorescence to detect the ferroptosis-related indexes in the mouse hippocampus and HT-22 cells. The inflammatory factors interferon-γ, tumor necrosis factor-α, transforming growth factor-β, and arginase 1 in the hippocampus and cells were detected using the Western blot assay. Hematoxylin and eosin staining, electron microscopy, and the Morris water maze experiment were used to evaluate the brain injuries of the mice. The results showed that TgCtwh3 infection is followed by the activation of ferroptosis-related signaling pathways and hippocampal pathological damage in mice. The use of DFP led to ferroptosis resistance and attenuated pathological changes, inflammatory reactions and T. gondii burden of the mice, prolonging their survival time. The HT-22 cells with TgCtwh3 activated the ferroptosis pathway and was inhibit by DFP in vitro. In TgCtwh3-infected cells, inflammatory response and mitochondrial damage were severe, but these effects could be reduced by DFP. Our study elucidates the mechanism by which T. gondii interferes with the host's iron metabolism and activates ferroptosis, complementing the pathogenic mechanism of CT and further demonstrating the potential value of DFP for the treatment of CT.

Exploring Antibiotic-Potentiating Effects of Tobramycin-Deferiprone Conjugates in Pseudomonas aeruginosa

Metal ions, including Fe3+, affect the target site binding of some antibiotics and control the porin- and siderophore-mediated uptake of antibiotics. Amphiphilic tobramycins are an emerging class of antibiotic potentiators capable of synergizing with multiple classes of antibiotics against Gram-negative bacteria, including Pseudomonas aeruginosa. To study how the antibiotic-potentiating effect of amphiphilic tobramycins is affected by the presence of intermolecular iron chelators, we conjugated the FDA-approved iron chelator deferiprone (DEF) to tobramycin (TOB). Three TOB-DEF conjugates differing in the length of the carbon tether were prepared and tested for antibacterial activity and synergistic relationships with a panel of antibiotics against clinical isolates of P. aeruginosa. While all TOB-DEF conjugates were inactive against P. aeruginosa, the TOB-DEF conjugates strongly synergized with outer-membrane-impermeable antibiotics, such as novobiocin and rifampicin. Among the three TOB-DEF conjugates, 1c containing a C12 tether showed a remarkable and selective potentiating effect to improve the susceptibility of multidrug-resistant P. aeruginosa isolates to tetracyclines when compared with other antibiotics. However, the antibacterial activity and antibiotic-potentiating effect of the optimized conjugate was not enhanced under iron-depleted conditions, indicating that the function of the antibiotic potentiator is not affected by the Fe3+ concentration.

The Vital Role Played by Deferiprone in the Transition of Thalassaemia from a Fatal to a Chronic Disease and Challenges in Its Repurposing for Use in Non-Iron-Loaded Diseases

The iron chelating orphan drug deferiprone (L1), discovered over 40 years ago, has been used daily by patients across the world at high doses (75-100 mg/kg) for more than 30 years with no serious toxicity. The level of safety and the simple, inexpensive synthesis are some of the many unique properties of L1, which played a major role in the contribution of the drug in the transition of thalassaemia from a fatal to a chronic disease. Other unique and valuable clinical properties of L1 in relation to pharmacology and metabolism include: oral effectiveness, which improved compliance compared to the prototype therapy with subcutaneous deferoxamine; highly effective iron removal from all iron-loaded organs, particularly the heart, which is the major target organ of iron toxicity and the cause of mortality in thalassaemic patients; an ability to achieve negative iron balance, completely remove all excess iron, and maintain normal iron stores in thalassaemic patients; rapid absorption from the stomach and rapid clearance from the body, allowing a greater frequency of repeated administration and overall increased efficacy of iron excretion, which is dependent on the dose used and also the concentration achieved at the site of drug action; and its ability to cross the blood-brain barrier and treat malignant, neurological, and microbial diseases affecting the brain. Some differential pharmacological activity by L1 among patients has been generally shown in relation to the absorption, distribution, metabolism, elimination, and toxicity (ADMET) of the drug. Unique properties exhibited by L1 in comparison to other drugs include specific protein interactions and antioxidant effects, such as iron removal from transferrin and lactoferrin; inhibition of iron and copper catalytic production of free radicals, ferroptosis, and cuproptosis; and inhibition of iron-containing proteins associated with different pathological conditions. The unique properties of L1 have attracted the interest of many investigators for drug repurposing and use in many pathological conditions, including cancer, neurodegenerative conditions, microbial conditions, renal conditions, free radical pathology, metal intoxication in relation to Fe, Cu, Al, Zn, Ga, In, U, and Pu, and other diseases. Similarly, the properties of L1 increase the prospects of its wider use in optimizing therapeutic efforts in many other fields of medicine, including synergies with other drugs.

Iron-loaded deferiprone can support full hemoglobinization of cultured red blood cells

Iron, supplemented as iron-loaded transferrin (holotransferrin), is an essential nutrient in mammalian cell cultures, particularly for erythroid cultures. The high cost of human transferrin represents a challenge for large scale production of red blood cells (RBCs) and for cell therapies in general. We evaluated the use of deferiprone, a cell membrane-permeable drug for iron chelation therapy, as an iron carrier for erythroid cultures. Iron-loaded deferiprone (Def₃·Fe³⁺, at 52 µmol/L) could eliminate the need for holotransferrin supplementation during in vitro expansion and differentiation of erythroblast cultures to produce large numbers of enucleated RBC. Only the first stage, when hematopoietic stem cells committed to erythroblasts, required holotransferrin supplementation. RBCs cultured in presence of Def₃·Fe³⁺ or holotransferrin (1000 µg/mL) were similar with respect to differentiation kinetics, expression of cell-surface markers CD235a and CD49d, hemoglobin content, and oxygen association/dissociation. Replacement of holotransferrin supplementation by Def₃·Fe³⁺ was also successful in cultures of myeloid cell lines (MOLM13, NB4, EOL1, K562, HL60, ML2). Thus, iron-loaded deferiprone can partially replace holotransferrin as a supplement in chemically defined cell culture medium. This holds promise for a significant decrease in medium cost and improved economic perspectives of the large scale production of red blood cells for transfusion purposes.

Challenges and Opportunities of Metal Chelation Therapy in Trace Metals Overload-Induced Alzheimer's Disease

Essential trace metals like zinc (Zn), iron (Fe), and copper (Cu) play an important physiological role in the metabolomics and healthy functioning of body organs, including the brain. However, abnormal accumulation of trace metals in the brain and dyshomeostasis in the different regions of the brain have emerged as contributing factors in neuronal degeneration, Aβ aggregation, and Tau formation. The link between these essential trace metal ions and the risk of AD has been widely studied, although the conclusions have been ambiguous. Despite the absence of evidence for any clinical benefit, therapeutic chelation is still hypothesized to be a therapeutic option for AD. Furthermore, the parameters like bioavailability, ability to cross the BBB, and chelation specificity must be taken into consideration while selecting a suitable chelation therapy. The data in this review summarizes that the primary intervention in AD is brain metal homeostasis along with brain metal scavenging. This review evaluates the impact of different trace metals (Cu, Zn, Fe) on normal brain functioning and their association with neurodegeneration in AD. Also, it investigates the therapeutic potential of metal chelators in the management of AD. An extensive literature search was carried out on the "Web of Science, PubMed, Science Direct, and Google Scholar" to investigate the effect of trace elements in neurological impairment and the role of metal chelators in AD. In addition, the current review highlights the advantages and limitations of chelation therapies and the difficulties involved in developing selective metal chelation therapy in AD patients.

Selective colorimetric sensing of deferoxamine with 4-mercaptophenol- and mercaptoacetic acid-functionalized gold nanoparticles via Fe(iii) chelation

The multidentate deferoxamine ligand can selectively aggregate the Fe(iii)-attached AuNPs@(4MP–MAA) colorimetric nanoprobe, whereas other bidentate iron chelators cannot bridge the nanoparticles.

Developing an Analytical Method Based on Graphene Quantum Dots for Quantification of Deferiprone in Plasma

In the world of nanotechnology, graphene quantum dots (GQDs) have been considerably employed in numerous optical sensing and bioanalytical applications. Herein, a simple and cost-efficient methodology was developed to the quantification of deferiprone in plasma samples by utilizing the selective interaction of the GQDs and drug in the presence of Fe³⁺ ions. GQDs were synthesized by a bottom-up technique as an advantageous fluorescent probe. Increasing levels of deferiprone ranging from 5 to 50 mg.L^-1, leads to significant fluorescence quenching of GQDs. In addition, the calibration curve was revealed a linear response in this range with a sensitivity of 5 mg.L^-1. The method validation was carried out according to the FDA guidelines to confirm the accuracy, precision, stability and selectivity of the developed method. The results show that this green and low-cost fluorescent probe could be used for the analysis of deferiprone.

Synthesis and iron chelating properties of hydroxypyridinone and hydroxypyranone hexadentate ligands

Chelation therapy has become an important therapeutic approach for some diseases.

The mono(catecholamine) derivatives as iron chelators: synthesis, solution thermodynamic stability and antioxidant properties research

There is a growing interest in the development of new iron chelators as novel promising therapeutic strategies for neurodegenerative disorders. In this article, a series of mono(catecholamine) derivatives, 2,3-bis(hydroxy)-N-(hydroxyacyl)benzamide, containing a pendant hydroxy, have been synthesized and fully characterized by nuclear magnetic resonance, Fourier transform infrared spectroscopy and mass spectrum. The thermodynamic stability of the chelators with Fe^III, Mg^II and Zn^II ions was then investigated. The chelators enable formation of (3 : 1) Fe^III complexes with high thermodynamic stability and exhibited improved selectivity to Fe^III ion. Meanwhile, the results of 1,1-diphenyl-2-picryl-hydrazyl assays of mono(catecholamine) derivatives indicated that they all possess excellent antioxidant properties. These results support the hypothesis that the mono(catecholamine) derivatives be used as high-affinity chelator for iron overload situations without depleting essential metal ions, such as Mg^II and Zn^II ions.

Mechanism Underlying the Effectiveness of Deferiprone in Alleviating Parkinson's Disease Symptoms

Elevation in iron content as well as severe depletion of dopamine (DA) as a result of iron-induced loss of dopaminergic neurons has been recognized to accompany the progression of Parkinson's disease (PD). To better understand the mechanism of the mitigating effect of the iron chelator deferiprone (DFP) on PD, the interplay between iron and DFP was investigated both in the absence and presence of DA. The results show that DFP was extremely efficient in scavenging both aqueous iron and iron that was loosely bound to DA with the entrapment of iron in Fe-DFP complexed form critical to halting the iron catalyzed degradation of DA and associated generation of toxic metabolites. The DFP related scavenging of dopamine semiquinone (DA^•-) and superoxide (O₂^•-) may also contribute to its positive effects in the treatment of PD.

In vitro antiproliferative study of novel adamantyl pyridin-4-ones

The preparation of several N-aryl-substituted (phenyl, p-methylphenyl, p-methoxyphenyl, p-nitrophenyl, p-aminophenyl, p-hydroxyphenyl) 3-hydroxy-2-methylpyridin-4-ones as well as their adamantyl derivatives is described, and their in vitro antitumor properties were investigated. The compounds were synthesized in good yields using efficient synthetic routes and methods. Prepared derivatives were evaluated in an antiproliferative in vitro study on 4 cancer cell lines, namely HCT 116 (colon carcinoma), H 460 (lung carcinoma), MCF-7 (breast carcinoma) and K562 (chronic myelogenous leukemia). All tested compounds showed antiproliferative activity ranging from moderate to strong on all inspected cell lines with 4 adamantane containing derivatives being active and selective at low micromolar IC[Formula: see text] concentrations on HCT 116, H 460 and MCF-7. LDH cytotoxicity assay revealed that cytotoxic effects occur after 48 h of exposure. It was shown that there was no change in caspase activity in the treated cells, but there were changes in the cell cycle. All treated samples showed reduced number of cells in the S phase with increased G0/G1 (4b, 5a, 5b) and G2/M (4a) phase.

Population pharmacokinetics and dosing recommendations for the use of deferiprone in children younger than 6 years

AIMS

Despite long clinical experience with deferiprone, there is limited information on its pharmacokinetics in children aged <6 years. Here we assess the impact of developmental growth on the pharmacokinetics of deferiprone in this population using a population approach. Based on pharmacokinetic bridging concepts, we also evaluate whether the recommended doses yield appropriate systemic exposure in this group of patients.

METHODS

Data from a study in which 18 paediatric patients were enrolled were available for the purposes of this analysis. Patients were randomised to three deferiprone dose levels (8.3, 16.7 and 33.3 mg kg^-1 ). Blood samples were collected according to an optimised sampling scheme in which each patient contributed to a maximum of five samples. A population pharmacokinetic model was developed using NONMEM v.7.2. Model selection criteria were based on graphical and statistical summaries.

RESULTS

A one-compartment model with first-order absorption and first-order elimination best described the pharmacokinetics of deferiprone. Drug disposition parameters were affected by body weight, with both clearance and volume increasing allometrically with size. Simulation scenarios show that comparable systemic exposure (AUC) is achieved in children and adults after similar dose levels in mg kg^-1 , with median (5-95^th quantiles) AUC values, respectively, of 340.6 (223.2-520.0) μmol l^-1  h and 318.5 (200.4-499.0) μmol l^-1  h at 75 mg kg^-1 day^-1 , and 453.7 (297.3-693.0) μmol l^-1  h and 424.2 (266.9-664.0) μmol l^-1  h at 100 mg kg^-1  day^-1 given as three times daily (t.i.d.) doses.

CONCLUSIONS

Based on the current findings, a dosing regimen of 25 mg kg^-1  t.i.d. is recommended in children aged <6 years, with the possibility of titration up to 33.3 mg kg^-1  t.i.d.

Effects of renal impairment on the pharmacokinetics of orally administered deferiprone

Aims

In light of the growing recognition of renal disease in thalassemia, it is important to understand the impact of renal impairment on the pharmacokinetics of iron chelators. This study evaluated the pharmacokinetics and safety of the iron chelator deferiprone (DFP) in subjects with renal impairment in comparison with healthy volunteers (HVs).

Methods

Thirty‐two subjects were categorized into four groups based on degree of renal impairment: none, mild, moderate or severe, as determined by estimated glomerular filtration rate (eGFR). All subjects received a single oral dose of 33 mg kg⁻¹ DFP, provided serum and urine samples for pharmacokinetic assessment over 24 h and were monitored for safety.

Results

Renal clearance of DFP decreased as renal impairment increased. However, based on C_max, AUC(0,t) and AUC(0,∞), there were no significant group differences in systemic exposure, because less than 4% of the drug was excreted unchanged in the urine. DFP is extensively metabolized to a renally excreted, pharmacologically inactive metabolite, deferiprone 3‐O‐glucuronide (DFP‐G), which exhibited higher C_max, AUC(0,t), AUC(0,∞) and longer t_max and t_1/2 in the renally impaired groups compared with HVs. The C_max and AUCs of DFP‐G increased as eGFR decreased. Overall, 75%–95% of the dose was retrieved in urine, either as DFP or DFP‐G, regardless of severity of renal impairment. With respect to safety, DFP was well tolerated.

Conclusions

These data suggest that no adjustment of the DFP dosage regimen in patients with renal impairment is necessary, as there were no significant changes in the systemic exposure to the drug.

Sampling Optimization in Pharmacokinetic Bridging Studies: Example of the Use of Deferiprone in Children With β-Thalassemia

Despite wide clinical experience with deferiprone, the optimum dosage in children younger than 6 years remains to be established. This analysis aimed to optimize the design of a prospective clinical study for the evaluation of deferiprone pharmacokinetics in children. A 1-compartment model with first-order oral absorption was used for the purposes of the analysis. Different sampling schemes were evaluated under the assumption of a constrained population size. A sampling scheme with 5 samples per subject was found to be sufficient to ensure accurate characterization of the pharmacokinetics of deferiprone. Whereas the accuracy of parameters estimates was high, precision was slightly reduced because of the small sample size (CV% >30% for Vd/F and KA). Mean AUC ± SD was found to be 33.4 ± 19.2 and 35.6 ± 20.2 mg · h/mL, and mean Cmax ± SD was found to be 10.2 ± 6.1 and 10.9 ± 6.7 mg/L based on sparse and frequent sampling, respectively. The results showed that typical frequent sampling schemes and sample sizes do not warrant accurate model and parameter identifiability. Expectation of the determinant (ED) optimality and simulation-based optimization concepts can be used to support pharmacokinetic bridging studies. Of importance is the accurate estimation of the magnitude of the covariate effects, as they partly determine the dose recommendation for the population of interest.

Design and synthesis of novel pegylated iron chelators with decreased metabolic rate

Background: Deferiprone has proved to be a successful iron selective chelator in a range of pathologies. However, its use is limited by rapid Phase II metabolism, necessitating the administration of large doses. In an attempt to modify metabolic rate of this class of compounds, a range of pegylated 3-hydroxypyridin-4-ones has been synthesized. Experimental: The synthetic route in which the polyethylene glycol counterparts are introduced to a protected pyran ring involves either a Williamson etherification reaction or direct addition leading to polyethylene glycol-containing precursors. Results & discussion: The introduction of the pegylated substituent was found to lead to a relatively low rate of metabolism for some of the derivatives (6a, 6b, 8a and 8b), offering a possible improvement over deferiprone.

Population pharmacokinetics of deferiprone in healthy subjects

AIMS

To characterize the pharmacokinetics of deferiprone in healthy subjects using a model-based approach and to assess the effect of demographic and physiological factors on drug exposure.

METHODS

Data from 55 adult healthy subjects receiving deferiprone (solution 100 mg ml(-1)) were used for model building purposes. A population pharmacokinetic analysis was performed using nonmem v.7.2. The contribution of gender, age, weight and creatinine clearance (CLcr) on drug disposition was evaluated according to standard forward inclusion, backward deletion procedures. Model selection criteria were based on graphical and statistical summaries.

RESULTS

A one compartment model with first order oral absorption was found to describe best the pharmacokinetics of deferiprone. Simulated exposure values were comparable with previously published data. Mean AUC estimates were 45.8 and 137.4 mg l(-1)  h, whereas Cmax increased from 17.6 to 26.5 mg l(-1) after administration of 25 and 75 mg kg(-1) doses, respectively. Gender differences in the apparent volume of distribution (20%) have been identified, which are unlikely to be of clinical relevance. Furthermore, simulation scenarios reveal that dose adjustment is required for patients with reduced CLcr . Doses of 60, 40 and 25 mg kg(-1) for patients showing mild, moderate and severe renal impairment are proposed based on CLcr values of 60-89, 30-59 and 15-29 ml min(-1), respectively.

CONCLUSIONS

Our analysis has enabled the assessment of the impact of gender and CLcr on the pharmacokinetics of deferiprone. Moreover, it provides the basis for dosing recommendations in renal impairment. The implication of these covariates on systemic exposure is currently not available in the prescribing information of deferiprone.

Metabolically programmed iron chelators

Extensive structure activity relationship (SAR) studies focused on the desferrithiocin [DFT, (S)-4,5-dihydro-2-(3-hydroxy-2-pyridinyl)-4-methyl-4-thiazolecarboxylic acid] pharmacophore have led to three different DFT analogs being evaluated clinically for the treatment of iron overload diseases, for example, thalassemia. The SAR work revealed that the lipophilicity of a ligand, as determined by its partition between octanol and water, logP(app), could have a profound effect on the drug's iron clearing efficiency (ICE), organ distribution, and toxicity profile. While within a given structural family the more lipophilic a chelator the better the ICE, unfortunately, the more lipophilic ligands are often more toxic. Thus, a balance between lipophilicity, ICE, and toxicity must be achieved. In the current study, we introduce the concept of 'metabolically programmed' iron chelators, that is, highly lipophilic, orally absorbable, effective deferration agents which, once absorbed, are quickly converted to their nontoxic, hydrophilic counterparts.

Hexadentate 3-hydroxypyridin-4-ones with high iron(III) affinity: design, synthesis and inhibition on methicillin resistant Staphylococcus aureus and Pseudomonas strains

A range of hexadentate 3-hydroxypyridin-4-ones have been synthesized. These compounds were found to possess a high affinity for iron(III), with logK1 values of about 34 and pFe values over 30. Antimicrobial assays indicated that they can inhibit the growth of three clinical isolates of methicillin resistant Staphylococcus aureus (MRSA) and three clinical isolates of Pseudomonas, suggesting that hexadentate 3-hydroxypyridin-4-ones have potential application in the treatment of wound infections.

Desferrithiocin: a search for clinically effective iron chelators

The successful search for orally active iron chelators to treat transfusional iron-overload diseases, e.g., thalassemia, is overviewed. The critical role of iron in nature as a redox engine is first described, as well as how primitive life forms and humans manage the metal. The problems that derive when iron homeostasis in humans is disrupted and the mechanism of the ensuing damage, uncontrolled Fenton chemistry, are discussed. The solution to the problem, chelator-mediated iron removal, is clear. Design options for the assembly of ligands that sequester and decorporate iron are reviewed, along with the shortcomings of the currently available therapeutics. The rationale for choosing desferrithiocin, a natural product iron chelator (a siderophore), as a platform for structure-activity relationship studies in the search for an orally active iron chelator is thoroughly developed. The study provides an excellent example of how to systematically reengineer a pharmacophore in order to overcome toxicological problems while maintaining iron clearing efficacy and has led to three ligands being evaluated in human clinical trials.

Novel chelators for cancer treatment: where are we now?

SIGNIFICANCE

Under normal circumstances, cellular iron levels are tightly regulated due to the potential toxic effects of this metal ion. There is evidence that tumors possess altered iron homeostasis, which is mediated by the perturbed expression of iron-related proteins, for example, transferrin receptor 1, ferritin and ferroportin 1. The de-regulation of iron homeostasis in cancer cells reveals a particular vulnerability to iron-depletion using iron chelators. In this review, we examine the absorption of iron from the gut; its transport, metabolism, and homeostasis in mammals; and the molecular pathways involved. Additionally, evidence for alterations in iron processing in cancer are described along with the perturbations in other biologically important transition metal ions, for example, copper(II) and zinc(II). These changes can be therapeutically manipulated by the use of novel chelators that have recently been shown to be highly effective in terms of inhibiting tumor growth.

RECENT ADVANCES

Such chelators include those of the thiosemicarbazone class that were originally thought to target only ribonucleotide reductase, but are now known to have multiple effects, including the generation of cytotoxic radicals.

CRITICAL ISSUES

Several chelators have shown marked anti-tumor activity in vivo against a variety of solid tumors. An important aspect is the toxicology and the efficacy of these agents in clinical trials.

FUTURE DIRECTIONS

As part of the process of the clinical assessment of the new chelators, an extensive toxicological assessment in multiple animal models is essential for designing appropriate dosing protocols in humans.

Deferiprone reduces amyloid-β and tau phosphorylation levels but not reactive oxygen species generation in hippocampus of rabbits fed a cholesterol-enriched diet

Accumulation of amyloid-β (Aβ) peptide and the hyperphosphorylation of tau protein are major hallmarks of Alzheimer's disease (AD). The causes of AD are not well known but a number of environmental and dietary factors are suggested to increase the risk of developing AD. Additionally, altered metabolism of iron may have a role in the pathogenesis of AD. We have previously demonstrated that cholesterol-enriched diet causes AD-like pathology with iron deposition in rabbit brain. However, the extent to which chelation of iron protects against this pathology has not been determined. In this study, we administered the iron chelator deferiprone in drinking water to rabbits fed with a 2% cholesterol diet for 12 weeks. We found that deferiprone (both at 10 and 50 mg/kg/day) significantly decreased levels of Aβ40 and Aβ42 as well as BACE1, the enzyme that initiates cleavage of amyloid-β protein precursor to yield Aβ. Deferiprone also reduced the cholesterol diet-induced increase in phosphorylation of tau but failed to reduce reactive oxygen species generation. While deferiprone treatment was not associated with any change in brain iron levels, it was associated with a significant reduction in plasma iron and cholesterol levels. These results demonstrate that deferiprone confers important protection against hypercholesterolemia-induced AD pathology but the mechanism(s) may involve reduction in plasma iron and cholesterol levels rather than chelation of brain iron. We propose that adding an antioxidant therapy to deferiprone may be necessary to fully protect against cholesterol-enriched diet-induced AD-like pathology.

Design and synthesis of fluorinated iron chelators for metabolic study and brain uptake

A range of fluorinated 3-hydroxypyridin-4-ones has been synthesized where fluorine or fluorinated substituent was attached at 2- or 5- position of the pyridine ring in order to improve chemical and biological properties of 3-hydroxypyridin-4-ones. The synthetic route is different from conventional counterparts where a functional group is introduced to a preformed 3-hydroxypyridin-4-one ring. Herein, we introduce a novel method which starts with a fluorine containing precursor and the two hydroxyl groups at 3- and 4- positions of the pyridine ring are introduced at a later stage. The pK(a) values of the free ligands and the affinity constants of their iron complexes demonstrate that the presence of fluorine dramatically alters the values. The distribution coefficient values of the free ligands and corresponding iron(III) complexes between 1-octanol and MOPS buffer (pH 7.4) are also influenced. Glucuronidation and oxidation studies of selected fluorinated 3-hydroxypyridin-4-ones demonstrate that some such fluorinated compounds have clear advantage over deferiprone in that they are metabolized more slowly. Blood-brain barrier permeability studies indicated that although lipophilicity influences the permeability it is not the only factor. Two of the selected seven fluorinated 3-hydroxypyridin-4-ones have improved brain distribution when compared with deferiprone.

Synthesis and characterization of a triazine dendrimer that sequesters iron(III) using 12 desferrioxamine B groups

The synthesis of a third generation triazine dendrimer, 1, containing multiple, iron-sequestering desferrioxamine B (DFO) groups is described. Benzoylation of the hydroxamic acid groups of DFO and formation of a reactive dichlorotriazine provide the intermediate for reaction with the second generation dendrimer displaying twelve amines. This strategy further generalizes the 'functional monomer' approach to generate biologically active triazine dendrimers. Dendrimer 1 is prepared in seven steps in 35% overall yield and displays 12 DFO groups making it 56% drug by weight. Spectrophotometric titrations (UV-vis) show that 1 sequesters iron(III) atoms with neither cooperativity nor significant interference from the dendrimer backbone. Evidence from NMR spectroscopy and mass spectrometry reveals a limitation to this functional monomer approach: trace amounts of O-to-N acyl migration from the protected hydroxamic acids to the amine-terminated dendrimer occurs during the coupling step leading to N-benzoylated dendrimers displaying fewer than 12 DFO groups.

Efficacy and safety of deferiprone (Ferriprox), an oral iron-chelating agent, in pediatric patients

Background

Iron overload is a predictable and life-threatening complication in patients dependent on the regular transfusion of RBCs. The aims of this study were to investigate the efficacy and safety of deferiprone in a variety of pediatric hematologic and/or oncologic patients with a high iron overload.

Methods

Seventeen patients (age: 1.1-20.4 years; median: 10.6 years) from 7 hospitals who were treated with deferiprone from 2006 to 2009 were enrolled in this study. Medical records of enrolled patients were reviewed retrospectively.

Results

Serum ferritin levels were 4,677.8±1,130.9 µg/L at baseline compared to 3,363.9±1,149.7 µg/L at the end of deferiprone treatment (P=0.033). Only 1 patient developed neutropenia as a complication.

Conclusion

Deferiprone treatment is relatively safe for pediatric patients suffering from various hematologic and oncologic diseases that require RBC transfusions as part of treatment. However, the potential development of critical complications such as agranulocytosis and/or neutropenia remains a concern.

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.

Liver Fibrosis and Iron Levels During Long-Term Deferiprone Treatment of Thalassemia Major Patients

Deferiprone (L1) is an orally active iron-chelation agent that is being evaluated as a treatment for iron overload in thalassemia major. Although some reports have concluded that LI may exacerbate hepatic fibrosis and the deterioration of liver function in thalassemia patients, other studies have reported no detrimental effects. In view of these serious concerns regarding the hepatic toxicity of LI, a Taiwanese group of beta-thalassemia (thal) patients with the longest known duration of LI therapy and who had provided liver biopsies, were enrolled in this study. From April 1999 to July 2004, the 17 enrolled thalassemia major patients had been on L1 therapy for as long as 19 to 60 months. Two liver biopsies from each of the 17 patients were received at the China Medical University Hospital, Taichung, Taiwan. Serum alanine aminotransferase (ALT), viral serological studies for hepatitis B and hepatitis C, iron scores and fibrosis scores were available at the beginning of the study and at the time of the second biopsy. Overall, the 17 patients received L1 therapy continuously for a mean period of 3.3 years. With the exception of two patients, fibrosis scores decreased in all patients after LI therapy. Three patients had increased iron scores after therapy of L1 and 11 patients had increased ALT levels; increased ALT levels occurred more frequently in hepatitis C positive patients. In this study, most thalassemia major patients had no progression of hepatic fibrosis or increased liver iron stores during long-term LI therapy.

Deferiprone or Deferoxaminevs. Combination Therapyin Patients with β-Thalassemia Major: A Case Studyin Taiwan

Deferiprone (L1) has been recommended as an effective oral chelation therapy for patients with beta-thalassemia major (TM). From 1999 to 2004, 114 patients with TM from five treatment centers were enrolled in this program: iron (Fe) was chelated with L1 in 57 patients, deferoxamine (DFO) in 26, and combined L1/DFO therapy in 31. We found that serum ferritin (SF) was significantly lower in nine patients receiving L1 for more than 5 years (p = 0.04), 22 patients receiving L1 for 1-2 years (p < 0.01) and 31 receiving the combined therapy (p = 0.01), yet significantly higher in those receiving DFO only (p < 0.01). One patient showed transient neutropenia; arthropathy in one patient and gastrointestinal upset in two were noted, with no significant change in alanine aminotransferase (ALT) level. Of 17 patients who were submitted to a liver biopsy, 15 showed no significant change in hepatic fibrosis scores after therapy with L1. None of the 88 patients, including 31 who received the combined therapy, have abandoned oral L1 treatment due to adverse effects. Results of this study proved that L1 or combined therapy with L1 and DFO is effective in reducing SP; incidence of adverse events was low in patients with TM.

Effect of iron-chelator deferiprone on the in vitro growth of staphylococci

The standard iron-chelator deferoxamine is known to prevent the growth of coagulase-negative staphylococci (CoNS) which are major pathogens in iron-overloaded patients. However, we found that deferoxamine rather promotes the growth of coagulase-positive Staphylococcus aureus. Accordingly, we tested whether deferiprone, a new clinically-available iron-chelator, can prevent the growth of S. aureus strains as well as CoNS. Deferiprone did not at least promote the growth of all S. aureus strains (n=26) and CoNS (n=27) at relatively low doses; moreover, it could significantly inhibit the growth of all staphylococci on non-transferrin-bound-iron and the growth of all CoNS on transferrin-bound iron at relatively high doses. At the same doses, it did not at least promote the growth of all S. aureus strains on transferrin-bound-iron. These findings indicate that deferiprone can be useful to prevent staphylococcal infections, as well as to improve iron overload, in iron-overloaded patients.

Synthesis, spectroscopic and biological aspects of iron(II) complexes

Five novel coordinated complexes of iron(II) with ciprofloxacin and neutral bidentate ligands have been prepared and characterized using elemental analyses, magnetic measurements, IR spectra, UV-VIS spectral, thermogravimetric analyses, 1H-NMR and 13C-NMR. The antimicrobial activity of the individual ligands, metal salt and metal complexes with respect to Bacillus subtilis, Escherichia coli, Bacillus cereus, Staphylococcus aureus, Salmonella typhi, Serratia marcescens, Aspergillus niger, Aspergillus flavus and Lasiodiplodia theobromae were evaluated by the agar-plate technique in comparison to reference standard drugs (ofloxacin, levofloxacin and fluconozole). Binding of the complexes to DNA was studied and is discussed.

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.

Chelation of bismuth by combining desferrioxamine and deferiprone in rats

Consumption and production of bismuth compounds are increasing, however, a little information on the toxic effect and also the effective method in removal of bismuth compounds are available. The present research aimed to characterize the potential efficiency of two chelators after bismuth administration for 55 days following two dose levels of 20 and 40 mg/kg body weight daily to male rats. However, we found abnormalities after bismuth administration in clinical signs, such as body weight, kidneys and liver damages, a black line on gums and skin reactions. Furthermore, the hypothesis that the two chelators might be more efficient as combined therapy than as single therapy in removing bismuth from the body was considered. Along this line, two known chelators deferiprone (1, 2-dimethy1-3-hydroxypyride-4-one, L1) and desferrioxamine (DFO) were chosen and tested in the acute rat model. Chelators were given orally (L1) or intraperitoneally (DFO) as a single or combined therapy for the period of a week. Doses of L1 and DFO were 110 mg/kg body weight in experiments. Bismuth and iron concentrations in various tissues were determined by graphite furnace and flame atomic absorption spectrometry, respectively. The combined chelation therapy results show that DFO and L1 are able to remove bismuth ions from the body, whereas iron concentration returned to the normal level and symptoms are also decreased. DFO was more effective than L1 in reducing bismuth concentration in tissues. The efficiency of DFO + L1 is more than DFO or L1 in removing bismuth from organs. Our results are indicative that the design procedure might be useful for preliminary in-vivo testing of the efficiency of chelating agents. Results of combined chelators’ treatment should be confirmed in a different experimental model before extrapolation to other systems. This testing procedure of course does not provide all the relevant answers for efficiency of chelating agents in bismuth toxicity.

The Fenton Activity of Iron(III) in the Presence of Deferiprone

Hydroxyl radical production from a range of clinically relevant iron chelators in the presence of hydrogen peroxide was measured using the deoxyribose oxidation assay. Hydroxyl radical production from an iron complex is dependent on whether the ligand is able to completely surround the iron, thereby preventing access of reductants to the coordinated iron cation. The partially coordinated [(deferiprone)(2)Fe(III)](+) complex is able to generate hydroxyl radicals in the presence of oxidants, whereas the fully coordinated [(deferiprone)(3)Fe(III)](0) complex is not. Hydroxyl radical production from iron(III)deferiprone complexes is dependent on the molar ratio of iron to deferiprone, which, in turn, affects the speciation of the complex. Mass spectrometry data have confirmed the presence of the [(deferiprone)(2)Fe(III)](+) complex in aqueous solution. Hydroxyl radical production from the [(deferiprone)(2)Fe(III)](+) complex is maximal in the presence of equimolar ascorbate and hydrogen peroxide and is abolished in the absence of hydrogen peroxide. Under biological conditions, any [(deferiprone)(2)Fe(III)](+) complex formed intracellularly will be rapidly reduced by ascorbate. The resulting unstable iron(II) complex will dissociate to hexa-aquo iron(II), a major component of the endogenous intracellular labile iron pool.