A new HPLC UV validated method for therapeutic monitoring of deferasirox in thalassaemic patients

Deferasirox: A comprehensive drug profile

Deferasirox is an iron-chelating drug developed by Novartis company for treatment of diseases accompanied by chronic iron overload; such as β-thalassemia or sickle cell diseases. Owing to its advantages such as high affinity, specificity and wide therapeutic window, it is considered as first line treatment. The current chapter describes the physicochemical characteristics, mode of action, pharmacokinetics, therapeutic applications and synthetic methods for deferasirox. Moreover, it includes Fourier transform infrared spectrometry (FTIR) and nuclear magnetic resonance spectroscopy (NMR) analysis for its functional groups. In addition, the selected analytical methods are summarized to aid the analysts in their routine analysis of deferasirox.

Quality by design approach for green HPLC method development for simultaneous analysis of two thalassemia drugs in biological fluid with pharmacokinetic study

This work implements a combined experimental approach of analytical quality-by-design (AQbD) and green analytical chemistry (GAC) to develop an HPLC method for simultaneous determination of the two thalassemia drugs, deferasirox (DFX) and deferiprone (DFP), in biological fluid for the first time. This integration was designed to maximize efficiency and minimize environmental impacts, as well as energy and solvent consumption. To accomplish this goal, an analytical quality-by-design approach was performed, beginning with quality risk assessment and scouting analysis, followed by Placket-Burman design screening for five chromatographic parameters. Critical method parameters were thoroughly recognized and then optimized by using a two levels-three factors custom experimental design to evaluate the optimum conditions that achieved the highest resolution with acceptable peak symmetry within the shortest run time. The desirability function was used to define the optimal chromatographic conditions, and the optimal separation was achieved using an XBridge® HPLC RP-C18 (4.6 × 250 mm, 5 μm) column with ethanol : acidic water at pH 3.0 adjusted by phosphoric acid in the ratio of (70 : 30, v/v) as the mobile phase at a flow rate of 1 mL min^-1 with UV detection at 225 nm at a temperature of 25 °C. Linearity was obtained over the concentration range of 0.30-20.00 μg mL^-1 and 0.20-20.00 μg mL^-1 for DFX and DFP, respectively, using 20.00 μg mL^-1 ibuprofen (IBF) as an internal standard. The established method's greenness profile was evaluated and measured using various assessment tools, and the developed method was green. For the validation of the developed method, FDA recommendations were followed, and all the results obtained met the acceptance criteria. The suggested method was successfully used to study the pharmacokinetic parameters of DFX and DFP in rat plasma. Due to the substantial increase in bioavailability of the two iron chelating drugs, the results from this study strongly recommend their co-administration.

Stable Luminescent Poly(Allylaminehydrochloride)-Templated Copper Nanoclusters for Selectively Turn-Off Sensing of Deferasirox in β-Thalassemia Plasma

Highly stable and facile one-pot copper nanoclusters (Cu NCs) coated with poly(allylamine hydrochloride) (PAH) have been synthesized for selectively sensing deferasirox (DFX) in β-thalassemia plasma. DFX is an important drug used for treating iron overloading in β-thalassemia, but needs to be monitored due to certain toxicity. In this study, the PAH-Cu NCs showed highly stable fluorescence with emission wavelengths at 450 nm. The DFX specifically interacted with the copper nanocluster to turn off the fluorescence of the PAH-Cu NCs, and could be selectively quantified through the fluorescence quenching effect. The linear range of DFX in plasma analyzed by PAH-Cu NCs was 1.0-100.0 µg/mL (r = 0.985). The relative standard deviation (RSD) and relative error (RE) were lower than 6.51% and 7.57%, respectively, showing excellent reproducibility of PAH-Cu NCs for sensing DFX in plasma. This method was also successfully applied for an analysis of three clinical plasma samples from β-thalassemia patients taking DFX. The data presented high similarity with that obtained through a capillary electrophoresis method. According to the results, the PAH-Cu NCs could be used as a tool for clinically sensing DFX in human plasma for clinical surveys.

Pharmacological and clinical evaluation of deferasirox formulations for treatment tailoring

Deferasirox (DFX) is the newest among three different chelators available to treat iron overload in iron-loading anaemias, firstly released as Dispersible Tablets (DT) and more recently replaced by Film-Coated Tablets (FCT). In this retrospective observational study, pharmacokinetics, pharmacodynamics, and safety features of DFX treatment were analyzed in 74 patients that took both formulations subsequently under clinical practice conditions. Bioavailability of DFX FCT compared to DT resulted higher than expected [C_max: 99.5 (FCT) and 69.7 (DT) μMol/L; AUC: 1278 (FCT) and 846 (DT), P < 0.0001]. DFX FCT was also superior in scalability among doses. After one year of treatment for each formulation, no differences were observed between the treatments in the overall iron overload levels; however, DFX FCT but not DT showed a significant dose–response correlation [Spearman r (dose-serum ferritin variation): − 0.54, P < 0.0001]. Despite being administered at different dosages, the long-term safety profile was not different between formulations: a significant increase in renal impairment risk was observed for both treatments and it was reversible under strict monitoring (P < 0.002). Altogether, these data constitute a comprehensive comparison of DFX formulations in thalassaemia and other iron-loading anaemias, confirming the effectiveness and safety characteristics of DFX and its applicability for treatment tailoring.

Sensitive determination of deferasirox in blood of patients with thalassemia using dispersive liquid-liquid microextraction based on solidification of floating organic drop followed by HPLC-UV

Deferasirox is an oral iron chelator that has been on the market since 2005 and has been a suitable replacement for injectable chelators. It is important to check the amount of this drug in the blood of patients due to side effects. In this study, a new dispersive liquid-liquid microextraction based on solidification of floating drganic drop (DLLME - SFO) was applied to the extraction of deferasirox in the blood of patients with thalassemia prior to its analysis by high-performance liquid chromatography-ultraviolet detection (HPLC - UV). In this method, two long alcohols of the normal chain are mixed in a particular ratio, and then it is injected into the sample solution, which is on the magnetic stirrer. In this case, the mixture of the two alcohol changes to new double-solvent aggregate. This new double-solvent system is used as an extractant, which has a higher extraction power than any of its components alone. Under the optimum conditions, the calibration graph was linear in the rage of 0.2-200 μg L^-1 with detection limit of 0.06 μg L^-1. Repeatability (intra-day) and reproducibility (inter-day) of method based on seven replicate measurements of 100.0 μg L^-1of deferasirox were 3.8 % and 5.7 %, respectively. The results showed that DLLME - SFO is a very simple, inexpensive, environmental friendly, sensitive and efficient analytical method for the determination of trace amount of drugs in biological samples and suitable results were obtained.

Review of Chromatographic Methods Coupled with Modern Detection Techniques Applied in the Therapeutic Drugs Monitoring (TDM)

Therapeutic drug monitoring (TDM) is a tool used to integrate pharmacokinetic and pharmacodynamics knowledge to optimize and personalize various drug therapies. The optimization of drug dosing may improve treatment outcomes, reduce toxicity, and reduce the risk of developing drug resistance. To adequately implement TDM, accurate and precise analytical procedures are required. In clinical practice, blood is the most commonly used matrix for TDM; however, less invasive samples, such as dried blood spots or non-invasive saliva samples, are increasingly being used. The choice of sample preparation method, type of column packing, mobile phase composition, and detection method is important to ensure accurate drug measurement and to avoid interference from matrix effects and drug metabolites. Most of the reported procedures used liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) techniques due to its high selectivity and sensitivity. High-performance chromatography with ultraviolet detection (HPLC-UV) methods are also used when a simpler and more cost-effective methodology is desired for clinical monitoring. The application of high-performance chromatography with fluorescence detection (HPLC-FLD) with and without derivatization processes and high-performance chromatography with electrochemical detection (HPLC-ED) techniques for the analysis of various drugs in biological samples for TDM have been described less often. Before chromatographic analysis, samples were pretreated by various procedures-most often by protein precipitation, liquid-liquid extraction, and solid-phase extraction, rarely by microextraction by packed sorbent, dispersive liquid-liquid microextraction. The aim of this article is to review the recent literature (2010-2020) regarding the use of liquid chromatography with various detection techniques for TDM.

Determination of Iron Chelating Agents by Analytical Methods: A Review

Acute iron poisoning and chronic iron overload consequences in significant morbidity and mortality worldwide. Treatment of acute iron poisoning and chronic iron overload can be challenging and care providers are often tackled with management dilemmas. Iron chelating agents are commonly prescribed for patients with iron deficiency anemia. In this review article, different analytical techniques are reported used for qualitative and quantitative analysis of iron chelating agents like, deferiprone, deferoxamine, and deferasirox. Efforts are taken to collect all related articles published till October 2018. This review discusses all analytical methods, its advantages and disadvantages as well as its applications. This article will help you to know about basic analytical techniques as well as advanced hyphenated techniques practiced for determination of iron chelating agents in different matrices. The techniques discussed in this review follow the ICH guidelines for method validation.

Role of CYP1A1, ABCG2, CYP24A1 and VDR gene polymorphisms on the evaluation of cardiac iron overload in thalassaemia patients

OBJECTIVES

Iron-burden-induced arrhythmia and heart failure are among the leading causes of morbidity and mortality in β-thalassaemia major patients. T2* cardiac magnetic resonance remains the only reliable noninvasive method for the heart iron excess assessment. We explored the role of single nucleotide polymorphisms involved in vitamin D metabolism, transport and activity and in deferasirox (DFX) metabolism on cardiac iron burden.

PATIENTS AND METHODS

One hundred and five β-thalassaemia patients, treated with DFX, were enrolled in the present study. Drug plasma Ctrough was measured by a high-performance liquid chromatography-ultraviolet method. Allelic discrimination was carried out using the real-time PCR.

RESULTS

CYP1A1*1189 CC, ABCG2 421 GA, CYP24A1 8620 GG and VDR TaqI CC single nucleotide polymorphisms influenced T2* values. Age, serum ferritin, ABCG2 421 GA, ABCG2 1194 +928 TC/CC, CYP24A1 22776 TT and VDR TaqI TC/CC were retained in linear regression model.

CONCLUSION

Our results suggested, for the first time, the role of DFX and vitamin D pharmacogenetics on cardiac iron overload.

The effect of vitamin D pathway genes and deferasirox pharmacogenetics on liver iron in thalassaemia major patients

Monitoring and treating iron overload is crucial in transfusion-dependent thalassaemia patients. Liver stiffness measurement by transient elastography and T2* magnetic resonance imaging represent non-invasive ways to evaluate the adequacy of the iron chelation treatment. We explored the role of single nucleotide polymorphisms involved in vitamin D metabolism, transport and activity, and in deferasirox metabolism on liver iron burden parameters. One-hundred and five beta-thalassaemia patients, treated with deferasirox, have been enrolled. Drug plasma C_trough and AUC were measured by a HPLC-UV method. Allelic discrimination was performed by real-time PCR. Age, UGT1A1-364 CT/TT and CYP27B1 -1260 GT/TT positively predicted liver stiffness values. Deferasirox dose and serum ferritin negatively predicted T2* data, whereas age and CYP2D6 1457 GG genotype positively influenced these values. The discoveries of this research may be useful for personalized medicine and the proposed method could be applied in patients with hereditary hemochromatosis and myelodysplastic syndromes.

Iron handling by the human kidney: glomerular filtration and tubular reabsorption both contribute to urinary iron excretion

In physiological conditions, circulating iron can be filtered by the glomerulus and is almost completely reabsorbed by the tubular epithelium to prevent urinary iron wasting. Increased urinary iron concentrations have been associated with renal injury. However, it is not clear whether increased urinary iron concentrations in patients are the result of increased glomerular iron filtration and/or insufficient tubular iron reabsorption and if these processes contribute to renal injury. We measured plasma and urine iron parameters and urinary tubular injury markers in healthy human subjects ( n = 20), patients with systemic iron overload ( n = 20), and patients with renal tubular dysfunction ( n = 18). Urinary iron excretion parameters were increased in both patients with systemic iron overload and tubular dysfunction, whereas plasma iron parameters were only increased in patients with systemic iron overload. In patients with systemic iron overload, increased urinary iron levels were associated with elevated circulating iron, as indicated by transferrin saturation (TSAT), and increased body iron, as suggested by plasma ferritin concentrations. In patients with tubular dysfunction, enhanced urinary iron and transferrin excretion were associated with distal tubular injury as indicated by increased urinary glutathione S-transferase pi 1-1 (GSTP1-1) excretion. In systemic iron overload, elevated urinary iron and transferrin levels were associated with increased injury to proximal tubules, indicated by increased urinary kidney injury marker 1 (KIM-1) excretion. Our explorative study demonstrates that both glomerular filtration of elevated plasma iron levels and insufficient tubular iron reabsorption could increase urinary iron excretion and cause renal injury.

Effect of pharmacogenetic markers of vitamin D pathway on deferasirox pharmacokinetics in children

OBJECTIVES

Patients with β-thalassemia major have extremely low vitamin D levels, owing to reduced intestinal absorption, subicteric tint, and/or iron-induced higher pigmentation. We investigated whether some polymorphisms within the VDR, CYP24A1, CYP27B1, and GC genes could play a role in deferasirox pharmacokinetics in a cohort of pediatric patients.

PATIENTS AND METHODS

Eighteen children with β-thalassemia were enrolled. Drug plasma concentrations at the end of dosing interval (Ctrough) and after 0, 2, 4, 6, and 24 h of drug administration were measured by a HPLC-UV method. Allelic discrimination for VDR (TaqI, FokI, BsmI, Cdx2, and ApaI), CYP24A1 (22776, 3999 and 8620), CYP27B1 (2838 and -1260), and GC (1296) single nucleotide polymorphisms was performed by real-time PCR.

RESULTS

CYP24A1 8620 AG/GG group negatively predicted Ctrough in regression analysis (P=0.012). ApaI AA genotype resulted as a negative predictor of Ctrough (P=0.025) and area under the concentration curve (P=0.007); FoKI CC genotype remained as area under the concentration curve positive predictor (P=0.008) and TC/CC group as half-life (t1/2) (P=0.003) and volume of distribution (Vd) (P=0.011) negative one; TaqI TC/CC was retained as a negative predictor of drug maximum concentration (Cmax) (P=0.004). Moreover, GC 1296 TG/GG seemed able to predict lower time to reach drug maximum concentration (Tmax) (P=0.033).

CONCLUSION

Our preliminary experience suggested the potential usefulness of vitamin D pharmacogenetic to better understand deferasirox interindividual variability, also in pediatric patients.

Role of CYP24A1, VDR and GC gene polymorphisms on deferasirox pharmacokinetics and clinical outcomes

β-Thalassemia patients develop deficiency in vitamin D absorption and liver hydroxylation, resulting in extremely low calcitriol levels. We explored the role of single-nucleotide polymorphisms (SNPs) involved in vitamin D metabolism, transport and activity on deferasirox pharmacokinetics and outcomes (effectiveness trough levels (C_trough) and the area under the curve (AUC) cutoffs of 20 μg ml^-1 and 360 μg ml^-1 h^-1, respectively; nonresponse AUC limit of 250 μg ml^-1 h^-1). Ninety-nine β-thalassemic patients were enrolled. Drug plasma C_trough and AUC were measured by the high-performance liquid chromatography system coupled with an ultraviolet determination method. Allelic discrimination for VDR, CYP24A1, CYP27B1 and GC gene SNPs was performed by real-time PCR. CYP24A1 22776 TT significantly influenced C_min and negatively predicted it in regression analysis. CYP24A1 3999 CC was associated with C_trough and C_min and was a negative predictor of T_max, whereas CYP24A1 8620 GG seemed to have a role in C_trough, AUC, t_1/2 and C_min, and was an AUC negative predictor factor. Considering treatment outcome, Cdx2 and GC 1296 were retained in regression analysis as AUC efficacy cutoff negative predictors.

Preconditioning of adipose tissue-derived mesenchymal stem cells with deferoxamine increases the production of pro-angiogenic, neuroprotective and anti-inflammatory factors: Potential application in the treatment of diabetic neuropathy

Diabetic neuropathy (DN) is one of the most frequent and troublesome complications of diabetes mellitus. Evidence from diabetic animal models and diabetic patients suggests that reduced availability of neuroprotective and pro-angiogenic factors in the nerves in combination with a chronic pro-inflammatory microenvironment and high level of oxidative stress, contribute to the pathogenesis of DN. Mesenchymal stem cells (MSCs) are of great interest as therapeutic agents for regenerative purposes, since they can secrete a broad range of cytoprotective and anti-inflammatory factors. Therefore, the use of the MSC secretome may represent a promising approach for DN treatment. Recent data indicate that the paracrine potential of MSCs could be boosted by preconditioning these cells with an environmental or pharmacological stimulus, enhancing their therapeutic efficacy. In the present study, we observed that the preconditioning of human adipose tissue-derived MSCs (AD-MSCs) with 150μM or 400μM of the iron chelator deferoxamine (DFX) for 48 hours, increased the abundance of the hypoxia inducible factor 1 alpha (HIF-1α) in a concentration dependent manner, without affecting MSC morphology and survival. Activation of HIF-1α led to the up-regulation of the mRNA levels of pro-angiogenic factors like vascular endothelial growth factor alpha and angiopoietin 1. Furthermore this preconditioning increased the expression of potent neuroprotective factors, including nerve growth factor, glial cell-derived neurotrophic factor and neurotrophin-3, and cytokines with anti-inflammatory activity like IL4 and IL5. Additionally, we observed that these molecules, which could also be used as therapeutics, were also increased in the secretome of MSCs preconditioned with DFX compared to the secretome obtained from non-preconditioned cells. Moreover, DFX preconditioning significantly increased the total antioxidant capacity of the MSC secretome and they showed neuroprotective effects when evaluated in an in vitro model of DN. Altogether, our findings suggest that DFX preconditioning of AD-MSCs improves their therapeutic potential and should be considered as a potential strategy for the generation of new alternatives for DN treatment.

Deferasirox pharmacogenetic influence on pharmacokinetic, efficacy and toxicity in a cohort of pediatric patients

AIM

We aimed to evaluate the influence of genetic polymorphisms involved in deferasirox metabolism and transport on its pharmacokinetics and treatment toxicity, in a cohort of β-thalassaemic children.

PATIENTS & METHODS

Drug plasma concentrations were measured by a HPLC-UV method. Allelic discrimination for UGT1A1, UGT1A3, CYP1A1, CYP1A2, CYP2D6, MRP2 and BCRP1 polymorphisms was performed by real-time PCR.

RESULTS

CYP1A1 rs2606345AA influenced C_trough (p = 0.001) and t_1/2 (p = 0.042), CYP1A1 rs4646903TC/CC (p = 0.005) and BCRP1 rs2231142GA/AA (p = 0.005) influenced T_max and CYP2D6 rs1135840CG/GG influenced C_max (p = 0.044). UGT1A1 rs887829TT (p = 0.002) and CYP1A2 rs762551CC (p = 0.019) resulted as predictive factor of ferritin levels and CYP1A1 rs2606345CA/AA (p = 0.021) and CYP1A2 rs762551AC/CC (p = 0.027) of liver iron concentration.

CONCLUSION

Our data suggest the usefulness of deferasirox pharmacogenetics in pediatric treatment optimization.

Deferasirox pharmacokinetics evaluation in a woman with hereditary haemochromatosis and heterozygous β-thalassaemia

We present the deferasirox pharmacokinetics evaluation of a female patient on iron chelation, for the interesting findings from her genetic background (hereditary haemochromatosis and heterozygous β-thalassaemia) and clinical history (ileostomy; iron overload from transfusions). Drug plasma concentrations were measured by an HPLC-UV validated method, before and after ileum resection. Area under deferasirox concentration curve over 24h (AUC) values were determined by the mixed log-linear rule, using Kinetica software. AUC was low also with high deferasirox dose as well as tolerability. Non invasive tissue iron quantification by magnetic resonance imaging or superconducting quantum interference device were prevented by a metal hip replacement. Good efficacy and normalisation of iron markers was obtained on long term. Therapeutic drug monitoring in patient in critical conditions may help to understand reasons for non response and set individualised treatment.

Deferasirox pharmacokinetic and toxicity correlation in β-thalassaemia major treatment

OBJECTIVES

Deferasirox adverse effects include the following: gastrointestinal disturbance, mild elevations in serum creatinine levels and intermittent proteinuria; these events are dose-dependent and reversible with drug discontinuation, but this solution can lead to an inadequate iron chelation. For these reasons, interindividual variability of drug plasma concentration could help the clinical management of deferasirox dosage. We sought to describe deferasirox plasma exposure in a cohort of 60 adult patients.

METHODS

A fully validated chromatographic method was used to quantify deferasirox concentration in plasma collected from β-thalassaemia adult patients. Samples obtained before and after 2, 4, 6 and 24 h drug administration were evaluated. Associations between variables were tested using the Pearson test.

KEY FINDINGS

Concerning pharmacokinetic parameters, a higher interindividual variability was shown. A positive correlation was found between deferasirox area under the concentration curve over 24 h and serum creatinine (r = 0.314; P = 0.018) and between area and drug dose (r = 0.311; P = 0.016). Moreover, a negative correlation resulted among area under the concentration curve over 24 h and serum ferritin (r = -0.291; P = 0.026) and among drug half-life and its dose (r = -0.319; P = 0.013).

CONCLUSIONS

Treatment decision based on the individual characteristics could strongly contribute to minimize toxicity and increase efficacy of deferasirox therapy.

Deferasirox pharmacokinetic evaluation in β-thalassaemia paediatric patients

OBJECTIVES

Iron chelation in the transfusion-dependent anaemias management is essential to prevent end-organ damage and to improve survival. Deferasirox is a once-daily orally active tridentate selective iron chelator which pharmacokinetic disposition could influence treatment efficacy and toxicity. Therapeutic drug monitoring is an important tool for optimizing drug utilization and doses.

METHODS

A fully validated chromatographic method was used to quantify deferasirox concentration in plasma collected from paediatric patients with β-thalassaemia. Samples obtained after 5 days of washout or in naïve patients before and after 2, 4, 6 and 24 h drug administration were evaluated.

KEY FINDINGS

Associations between variables were tested using the Pearson test. Twenty paediatric patients were enrolled; they were mainly men (13.65%), with median age of 6.35 years and body mass index of 15.45 kg/m² . Concerning pharmacokinetic parameters, a higher interindividual variability was shown. A positive, but not significant, correlation (r = 0.363; P = 0.115) was found between deferasirox area under the concentration curve over 24 h (AUC) and drug dose.

CONCLUSIONS

Monitoring plasma deferasirox concentrations appears beneficial for guiding appropriate patient treatment, enhancing effectiveness and minimizing toxicity.

Role of pharmacogenetics on deferasirox AUC and efficacy

AIM

We evaluated deferasirox pharmacokinetic according to SNPs in genes involved in its metabolism and elimination. Moreover, we defined a plasma area under the curve cut-off value predicting therapy response.

PATIENTS & METHODS

Allelic discrimination was performed by real-time PCR. Drug plasma concentrations were measured by a high performance liquid chromatography system coupled with an ultraviolet method.

RESULTS

Pharmacokinetic parameters were significantly influenced by UGT1A1 rs887829C>T, UGT1A3 rs1983023C>T and rs3806596A>G SNPs. Area under the curve cut-off values of 360 μg/ml/h for efficacy were here defined and 250 μg/ml/h for nonresponse was reported. UGT1A3 rs3806596GG and ABCG2 rs13120400CC genotypes were factors able to predict efficacy, whereas UGT1A3 rs3806596GG was a nonresponse predictor.

CONCLUSION

These data show how screening patient's genetic profile may help clinicians to optimize iron chelation therapy with deferasirox.

Influence of single-nucleotide polymorphisms on deferasirox C trough levels and effectiveness

Deferasirox (DFX) is the only once-daily oral chelator for iron overload and its pharmacokinetic has been related with response to therapy. Our aim was to evaluate DFX plasma concentrations according to single-nucleotide polymorphisms in genes involved in its metabolism (UGT1A1, UGT1A3, CYP1A1, CYP1A2 and CYP2D6) and elimination (MRP2 and BCRP1). Further aim was to define a plasma concentration cutoff value predicting an adequate response to therapy. Plasma concentrations were determined at the end of dosing interval (C trough) using an high-performance liquid chromatography-ultraviolet method. Allelic discrimination was performed by real-time PCR. C trough levels were influenced by UGT1A1C>T rs887829, CYP1A1C>A rs2606345, CYP1A2A>C rs762551, CYP1A2C>T rs2470890 and MRP2G>A rs2273697 polymorphisms. A DFX plasma efficacy cutoff value of 20,000 ng ml(-1) was identified; CYP1A1C>A rs2606345 AA and CYP1A2C>T rs2470890 TT genotypes may predict this value, suggesting a negative predictive role in therapy efficacy. Our data suggest the feasibility of a pharmacogenetic-based DFX dose personalization.

Determination of deferasirox plasma concentrations: do gender, physical and genetic differences affect chelation efficacy?

OBJECTIVES

Bioavailability of deferasirox (DFX) is significantly affected by the timing of administration relative to times and to composition of meals. Its elimination half-life is also highly variable - in some patients as a result of gene polymorphisms. Understanding whether deferasirox plasma levels are related to specific characteristics of patients could help physicians to devise a drug regimen tailored the individual patient.

METHODS

We analyzed deferasirox plasma concentrations (CDFX ) in 80 patients with transfusion-dependent anemias, such as thalassemia, by a high performance liquid chromatography (HPLC) assay. We used a multivariate linear regression model to find significant associations between CDFX and clinical/demographical characteristics of patients. All patients were genotyped for UGT1A1.

RESULTS

Fifty-six patients were female, 24 were male, the great majority (88%) affected by β-thalassemia, and 15 were children and adolescents. No statistical correlation was detectable between CDFX and DFX dose (P = 0.6). Age, time from last drug intake to blood sampling, and ferritin levels in the 6 months before study initiation were significantly and inversely associated with CDFX in univariate analysis. In the multivariate analysis, the only two factors independently and inversely associated with CDFX levels were time from last drug intake to blood sampling and ferritin levels (P = 0.006). A significant inverse correlation (P = 0.03) was observed between CDFX and UGT1A1*28 gene polymorphism, but only in patients with levels of lean body mass (LBM) below the median (P for interaction = 0.05).

CONCLUSIONS

The results could indicate that a higher plasma DFX concentration could be associated with greater chelation efficacy. As a correlation between dose and CDFX was not demonstrated, it seems useful to monitor the concentrations to optimize and determine the most appropriate dose for each patient. Interesting results emerged from the analysis of genetic and physical characteristics of patients: LBM was a borderline significant effect modifier of the relationship between UGT1A1 polymorphisms and CDFX . Individual patient-tailored dosing of DFX should help to improve iron chelation efficacy and to reduce dose-dependent drug toxicity.