Trial of Deferiprone in Parkinson's Disease

BACKGROUND

Iron content is increased in the substantia nigra of persons with Parkinson's disease and may contribute to the pathophysiology of the disorder. Early research suggests that the iron chelator deferiprone can reduce nigrostriatal iron content in persons with Parkinson's disease, but its effects on disease progression are unclear.

METHODS

We conducted a multicenter, phase 2, randomized, double-blind trial involving participants with newly diagnosed Parkinson's disease who had never received levodopa. Participants were assigned (in a 1:1 ratio) to receive oral deferiprone at a dose of 15 mg per kilogram of body weight twice daily or matched placebo for 36 weeks. Dopaminergic therapy was withheld unless deemed necessary for symptom control. The primary outcome was the change in the total score on the Movement Disorder Society-sponsored revision of the Unified Parkinson's Disease Rating Scale (MDS-UPDRS; range, 0 to 260, with higher scores indicating more severe impairment) at 36 weeks. Secondary and exploratory clinical outcomes at up to 40 weeks included measures of motor and nonmotor disability. Brain iron content measured with the use of magnetic resonance imaging was also an exploratory outcome.

RESULTS

A total of 372 participants were enrolled; 186 were assigned to receive deferiprone and 186 to receive placebo. Progression of symptoms led to the initiation of dopaminergic therapy in 22.0% of the participants in the deferiprone group and 2.7% of those in the placebo group. The mean MDS-UPDRS total score at baseline was 34.3 in the deferiprone group and 33.2 in the placebo group and increased (worsened) by 15.6 points and 6.3 points, respectively (difference, 9.3 points; 95% confidence interval, 6.3 to 12.2; P<0.001). Nigrostriatal iron content decreased more in the deferiprone group than in the placebo group. The main serious adverse events with deferiprone were agranulocytosis in 2 participants and neutropenia in 3 participants.

CONCLUSIONS

In participants with early Parkinson's disease who had never received levodopa and in whom treatment with dopaminergic medications was not planned, deferiprone was associated with worse scores in measures of parkinsonism than those with placebo over a period of 36 weeks. (Funded by the European Union Horizon 2020 program; FAIRPARK-II ClinicalTrials.gov number, NCT02655315.).

Evaluation of the efficacy and safety of deferiprone compared with deferasirox in paediatric patients with transfusion-dependent haemoglobinopathies (DEEP-2): a multicentre, randomised, open-label, non-inferiority, phase 3 trial

BACKGROUND

Transfusion-dependent haemoglobinopathies require lifelong iron chelation therapy with one of the three iron chelators (deferiprone, deferasirox, or deferoxamine). Deferasirox and deferiprone are the only two oral chelators used in adult patients with transfusion-dependent haemoglobinopathies. To our knowledge, there are no randomised clinical trials comparing deferiprone, a less expensive iron chelator, with deferasirox in paediatric patients. We aimed to show the non-inferiority of deferiprone versus deferasirox.

METHODS

DEEP-2 was a phase 3, multicentre, randomised trial in paediatric patients (aged 1 month to 18 years) with transfusion-dependent haemoglobinopathies. The study was done in 21 research hospitals and universities in Italy, Egypt, Greece, Albania, Cyprus, Tunisia, and the UK. Participants were receiving at least 150 mL/kg per year of red blood cells for the past 2 years at the time of enrolment, and were receiving deferoxamine (<100 mg/kg per day) or deferasirox (<40 mg/kg per day; deferasirox is not registered for use in children aged <2 years so only deferoxamine was being used in these patients). Any previous chelation treatment was permitted with a 7-day washout period. Patients were randomly assigned 1:1 to receive orally administered daily deferiprone (75-100 mg/kg per day) or daily deferasirox (20-40 mg/kg per day) administered as dispersible tablets, both with dose adjustment for 12 months, stratified by age (<10 years and ≥10 years) and balanced by country. The primary efficacy endpoint was based on predefined success criteria for changes in serum ferritin concentration (all patients) and cardiac MRI T2-star (T2*; patients aged >10 years) to show non-inferiority of deferiprone versus deferasirox in the per-protocol population, defined as all randomly assigned patients who received the study drugs and had available data for both variables at baseline and after 1 year of treatment, without major protocol violations. Non-inferiority was based on the two-sided 95% CI of the difference in the proportion of patients with treatment success between the two groups and was shown if the lower limit of the two-sided 95% CI was greater than -12·5%. Safety was assessed in all patients who received at least one dose of study drug. This study is registered with EudraCT, 2012-000353-31, and ClinicalTrials.gov, NCT01825512.

FINDINGS

435 patients were enrolled between March 17, 2014, and June 16, 2016, 393 of whom were randomly assigned to a treatment group (194 to the deferiprone group; 199 to the deferasirox group). 352 (90%) of 390 patients had β-thalassaemia major, 27 (7%) had sickle cell disease, five (1%) had thalassodrepanocytosis, and six (2%) had other haemoglobinopathies. Median follow-up was 379 days (IQR 294-392) for deferiprone and 381 days (350-392) for deferasirox. Non-inferiority of deferiprone versus deferasirox was established (treatment success in 69 [55·2%] of 125 patients assigned deferiprone with primary composite efficacy endpoint data available at baseline and 1 year vs 80 [54·8%] of 146 assigned deferasirox, difference 0·4%; 95% CI -11·9 to 12·6). No significant difference between the groups was shown in the occurrence of serious and drug-related adverse events. Three (2%) cases of reversible agranulocytosis occurred in the 193 patients in the safety analysis in the deferiprone group and two (1%) cases of reversible renal and urinary disorders (one case of each) occurred in the 197 patients in the deferasirox group. Compliance was similar between treatment groups: 183 (95%) of 193 patients in the deferiprone group versus 192 (97%) of 197 patients in the deferisirox group.

INTERPRETATION

In paediatric patients with transfusion-dependent haemoglobinopathies, deferiprone was effective and safe in inducing control of iron overload during 12 months of treatment. Considering the need for availability of more chelation treatments in paediatric populations, deferiprone offers a valuable treatment option for this age group.

FUNDING

EU Seventh Framework Programme.

Action of iron chelator on intramyocardial hemorrhage and cardiac remodeling following acute myocardial infarction

Intramyocardial hemorrhage is an independent predictor of adverse outcomes in ST-segment elevation myocardial infarction (STEMI). Iron deposition resulting from ischemia-reperfusion injury (I/R) is pro-inflammatory and has been associated with adverse remodeling. The role of iron chelation in hemorrhagic acute myocardial infarction (AMI) has never been explored. The purpose of this study was to investigate the cardioprotection offered by the iron-chelating agent deferiprone (DFP) in a porcine AMI model by evaluating hemorrhage neutralization and subsequent cardiac remodeling. Two groups of animals underwent a reperfused AMI procedure: control and DFP treated (N = 7 each). A comprehensive MRI examination was performed in healthy state and up to week 4 post-AMI, followed by histological assessment. Infarct size was not significantly different between the two groups; however, the DFP group demonstrated earlier resolution of hemorrhage (by T2* imaging) and edema (by T2 imaging). Additionally, ventricular enlargement and myocardial hypertrophy (wall thickness and mass) were significantly smaller with DFP, suggesting reduced adverse remodeling, compared to control. The histologic results were consistent with the MRI findings. To date, there is no effective targeted therapy for reperfusion hemorrhage. Our proof-of-concept study is the first to identify hemorrhage-derived iron as a therapeutic target in I/R and exploit the cardioprotective properties of an iron-chelating drug candidate in the setting of AMI. Iron chelation could potentially serve as an adjunctive therapy in hemorrhagic AMI.

Abstract 848: The Iron Chelator Deferiprone Clears Hemorrhagic Byproducts Following Acute Myocardial Infarction in a Swine Model of Ischemia-Reperfusion

Current treatments for myocardial infarction (MI) aim to remove the vascular occlusion and reperfuse the infarcted tissue. While reperfusion can salvage myocardium, it can also increase damage to the unsalvageable tissue, one mechanism of which is hemorrhage; the resulting blood and iron deposits increase edema and inflammation. We hypothesize that removing these iron deposits with the iron chelating drug deferiprone (DFP) will reduce inflammation and lead to faster healing post-MI.

Using a swine model of ischemia-reperfusion, pigs were administered either DFP or saline for four weeks post-MI. Cardiac MRI tracked heart function, infarct progression (via late gadolinium enhancement), hemorrhage (via T2* imaging), and edema (via T2 imaging) at baseline and 1 day, 1 week, and 4 weeks post-MI. Animals were then sacrificed and hearts were processed for histology.

Treatment with DFP decreased the presence of iron in the infarct compared to saline by one week post-MI, as shown by increased T2* values. DFP treatment also decreased end diastolic wall swelling, suggesting less inflammation post-MI. To support this, T2 values and histology both revealed trends toward less edema with DFP. Histology also showed trended increases in fibroblast proliferation and collagen deposition at four weeks post-MI in the treatment group, consistent with a faster resolution to scar. Ventricular remodeling (by ventricular volumes), infarct size (by MRI, histology and blood Troponin I levels), and infarct transmurality were all unaffected, but contractile function improved with DFP treatment: ejection fraction and wall thickening both improved faster.

In conclusion, DFP treatment successfully reduced hemorrhagic iron within the infarct as compared to saline, indicating a clearing of the iron byproducts. Treatment also decreased wall swelling, suggesting reduced inflammation, and improved contractile function. In the infarct, reduced swelling could indicate faster remodeling and a faster resolution to scar, and histology confirms a more progressed scar structure with DFP treatment. Overall, iron chelation appears to be a promising therapy that could reduce the negative effects of hemorrhage and speed the functional recovery of patients post-MI.

Safety and efficacy of deferiprone for pantothenate kinase-associated neurodegeneration: a randomised, double-blind, controlled trial and an open-label extension study

BACKGROUND

Pantothenate kinase-associated neurodegeneration (PKAN) is a rare genetic disorder characterised by progressive generalised dystonia and brain iron accumulation. We assessed whether the iron chelator deferiprone can reduce brain iron and slow disease progression.

METHODS

We did an 18-month, randomised, double-blind, placebo-controlled trial (TIRCON2012V1), followed by a pre-planned 18-month, open-label extension study, in patients with PKAN in four hospitals in Germany, Italy, England, and the USA. Patients aged 4 years or older with a genetically confirmed diagnosis of PKAN, a total score of at least 3 points on the Barry-Albright Dystonia (BAD) scale, and no evidence of iron deficiency, neutropenia, or abnormal hepatic or renal function, were randomly allocated (2:1) to receive an oral solution of either deferiprone (30 mg/kg per day divided into two equal doses) or placebo for 18 months. Randomisation was done with a centralised computer random number generator and with stratification based on age group at onset of symptoms. Patients were allocated to groups by a randomisation team not masked for study intervention that was independent of the study. Patients, caregivers, and investigators were masked to treatment allocation. Co-primary endpoints were the change from baseline to month 18 in the total score on the BAD scale (which measures severity of dystonia in eight body regions) and the score at month 18 on the Patient Global Impression of Improvement (PGI-I) scale, which is a patient-reported interpretation of symptom improvement. Efficacy analyses were done on all patients who received at least one dose of the study drug and who provided a baseline and at least one post-baseline efficacy assessment. Safety analyses were done for all patients who received at least one dose of the study drug. Patients who completed the randomised trial were eligible to enrol in a single-arm, open-label extension study of another 18 months, in which all participants received deferiprone with the same regimen as the main study. The trial was registered on ClinicalTrials.gov, number NCT01741532, and EudraCT, number 2012-000845-11.

FINDINGS

Following a screening of 100 prospective patients, 88 were randomly assigned to the deferiprone group (n=58) or placebo group (n=30) between Dec 13, 2012, and April 21, 2015. Of these, 76 patients completed the study (49 in the deferiprone group and 27 in the placebo group). After 18 months, the BAD score worsened by a mean of 2·48 points (SE 0·63) in patients in the deferiprone group versus 3·99 points (0·82) for patients in the control group (difference -1·51 points, 95% CI -3·19 to 0·16, p=0·076). No subjective change was detected as assessed by the PGI-I scale: mean scores at month 18 were 4·6 points (SE 0·3) for patients in the deferiprone group versus 4·7 points (0·4) for those in the placebo group (p=0·728). In the extension study, patients continuing deferiprone retained a similar rate of disease progression as assessed by the BAD scale (1·9 points [0·5] in the first 18 months vs 1·4 points [0·4] in the second 18 months, p=0·268), whereas progression in patients switching from placebo to deferiprone seemed to slow (4·4 points [1·1] vs 1·4 points [0·9], p=0·021). Patients did not detect a change in their condition after the additional 18 months of treatment as assessed by the PGI-I scale, with mean scores of 4·1 points [0·2] in the deferiprone-deferiprone group and of 4·7 points [0·3] in the placebo-deferiprone group. Deferiprone was well tolerated and adverse events were similar between the treatment groups, except for anaemia, which was seen in 12 (21%) of 58 patients in the deferiprone group, but was not seen in any patients in the placebo group. No patient discontinued therapy because of anaemia, and three discontinued because of moderate neutropenia. There was one death in each group of the extension study and both were secondary to aspiration. Neither of these events was considered related to deferiprone use.

INTERPRETATION

Deferiprone was well tolerated, achieved target engagement (lowering of iron in the basal ganglia), and seemed to somewhat slow disease progression at 18 months, although not significantly, as assessed by the BAD scale. These findings were corroborated by the results of an additional 18 months of treatment in the extension study. The subjective PGI-I scale was largely unchanged during both study periods, indicating that might not be an adequate tool for assessment of disease progression in patients with PKAN. Our trial provides the first indication of a decrease in disease progression in patients with neurodegeneration with brain iron accumulation. The extensive information collected and long follow-up of patients in the trial will improve the definition of appropriate endpoints, increase the understanding of the natural history, and thus help to shape the design of future trials in this ultra-orphan disease.

FUNDING

European Commission, US Food and Drug Administration, and ApoPharma Inc.

Brain iron chelation by deferiprone in a phase 2 randomised double-blinded placebo controlled clinical trial in Parkinson's disease

Parkinson's disease (PD) is associated with increased iron levels in the substantia nigra (SNc). This study evaluated whether the iron chelator, deferiprone, is well tolerated, able to chelate iron from various brain regions and improve PD symptomology. In a randomised double-blind, placebo controlled trial, 22 early onset PD patients, were administered deferiprone, 10 or 15 mg/kg BID or placebo, for 6 months. Patients were evaluated for PD severity, cognitive function, depression rating and quality of life. Iron concentrations were assessed in the substantia nigra (SNc), dentate and caudate nucleus, red nucleus, putamen and globus pallidus by T2* MRI at baseline and after 3 and 6 months of treatment. Deferiprone therapy was well tolerated and was associated with a reduced dentate and caudate nucleus iron content compared to placebo. Reductions in iron content of the SNc occurred in only 3 patients, with no changes being detected in the putamen or globus pallidus. Although 30 mg/kg deferiprone treated patients showed a trend for improvement in motor-UPDRS scores and quality of life, this did not reach significance. Cognitive function and mood were not adversely affected by deferiprone therapy. Such data supports more extensive clinical trials into the potential benefits of iron chelation in PD.

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.

Deferiprone-induced agranulocytosis: 20 years of clinical observations

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

A Study of Patient Responses to a Perceived Change in Salbutamol Metered Dose Inhalers

Experience in the clinic reveals that some patients have attributed negative changes in their respiratory health status to generic substitution of inhaled medications, even though — from a pharmacological perspective — therapeutic equivalence would be expected. The objective of this study was to evaluate patient-reported changes in efficacy or toxicity following a perceived switch of an inhaled drug product. Forty-eight patients with air flow limitation had their usual brand of salbutamol metered-dose inhaler (MDI) replaced for one week with a new MDI. Patients were not informed that the replacement MDI was exactly the same brand as their usual MDI, and the product identity was disguised by a label. Forced expiratory volume in one second, respiratory symptoms and MDI use were compared between the week when the patients knew they were using their usual brand of MDI and the week they were using the perceived new MDI. Patient MDI preference was assessed at the end of the study. Even though there was no change in the brand of salbutamol MDI, 46 per cent of patients thought that the new MDI was better at managing their symptoms, 27 per cent thought that the new MDI was worse and 27 per cent perceived no difference (p<0.05 for rejecting the null hypothesis that all responses would be for no difference). Seventy per cent of patients stated that they had a preference for one MDI over the other, even though there had been no change in inhaler. Factors other than product differences are likely to be responsible for patient claims of changes in respiratory health status subsequent to generics substitution with inhaled medications when equivalent products are used. If such changes are reported following the introduction of a new generic product, the changes may be incorrectly attributed to the new product, confounding the ability to assess the quality of the new product in post-marketing evaluation.

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.

Drug-Based Lead Discovery: The Novel Ablative Antiretroviral Profile of Deferiprone in HIV-1-Infected Cells and in HIV-Infected Treatment-Naive Subjects of a Double-Blind, Placebo-Controlled, Randomized Exploratory Trial

Antiretrovirals suppress HIV-1 production yet spare the sites of HIV-1 production, the HIV-1 DNA-harboring cells that evade immune detection and enable viral resistance on-drug and viral rebound off-drug. Therapeutic ablation of pathogenic cells markedly improves the outcome of many diseases. We extend this strategy to HIV-1 infection. Using drug-based lead discovery, we report the concentration threshold-dependent antiretroviral action of the medicinal chelator deferiprone and validate preclinical findings by a proof-of-concept double-blind trial. In isolate-infected primary cultures, supra-threshold concentrations during deferiprone monotherapy caused decline of HIV-1 RNA and HIV-1 DNA; did not allow viral breakthrough for up to 35 days on-drug, indicating resiliency against viral resistance; and prevented, for at least 87 days off-drug, viral rebound. Displaying a steep dose-effect curve, deferiprone produced infection-independent deficiency of hydroxylated hypusyl-eIF5A. However, unhydroxylated deoxyhypusyl-eIF5A accumulated particularly in HIV-infected cells; they preferentially underwent apoptotic DNA fragmentation. Since the threshold, ascertained at about 150 μM, is achievable in deferiprone-treated patients, we proceeded from cell culture directly to an exploratory trial. HIV-1 RNA was measured after 7 days on-drug and after 28 and 56 days off-drug. Subjects who attained supra-threshold concentrations in serum and completed the protocol of 17 oral doses, experienced a zidovudine-like decline of HIV-1 RNA on-drug that was maintained off-drug without statistically significant rebound for 8 weeks, over 670 times the drug's half-life and thus clearance from circulation. The uniform deferiprone threshold is in agreement with mapping of, and crystallographic 3D-data on, the active site of deoxyhypusyl hydroxylase (DOHH), the eIF5A-hydroxylating enzyme. We propose that deficiency of hypusine-containing eIF5A impedes the translation of mRNAs encoding proline cluster ('polyproline')-containing proteins, exemplified by Gag/p24, and facilitated by the excess of deoxyhypusine-containing eIF5A, releases the innate apoptotic defense of HIV-infected cells from viral blockade, thus depleting the cellular reservoir of HIV-1 DNA that drives breakthrough and rebound.

TRIAL REGISTRATION

ClinicalTrial.gov NCT02191657.

Cp/Heph mutant mice have iron-induced neurodegeneration diminished by deferiprone

Brain iron accumulates in several neurodegenerative diseases and can cause oxidative damage, but mechanisms of brain iron homeostasis are incompletely understood. Patients with mutations in the cellular iron-exporting ferroxidase ceruloplasmin (Cp) have brain iron accumulation causing neurodegeneration. Here, we assessed the brains of mice with combined mutation of Cp and its homolog hephaestin. Compared to single mutants, brain iron accumulation was accelerated in double mutants in the cerebellum, substantia nigra, and hippocampus. Iron accumulated within glia, while neurons were iron deficient. There was loss of both neurons and glia. Mice developed ataxia and tremor, and most died by 9 months. Treatment with the oral iron chelator deferiprone diminished brain iron levels, protected against neuron loss, and extended lifespan. Ferroxidases play important, partially overlapping roles in brain iron homeostasis by facilitating iron export from glia, making iron available to neurons. Above: Iron (Fe) normally moves from capillaries to glia to neurons. It is exported from the glia by ferroportin (Fpn) with ferroxidases ceruloplasmin (Cp) and/or Hephaestin (Heph). Below: In mice with mutation of Cp and Heph, iron accumulates in glia, while neurons have low iron levels. Both neurons and glia degenerate and mice become ataxic unless given an iron chelator.

Deferiprone in Friedreich ataxia: a 6-month randomized controlled trial

OBJECTIVE

We conducted a 6-month, randomized, double-blind, placebo-controlled study to assess safety, tolerability, and efficacy of deferiprone in Friedreich ataxia (FRDA).

METHODS

Seventy-two patients were treated with deferiprone 20, 40, or 60mg/kg/day or placebo, divided into 2 daily doses. Safety was the primary objective; secondary objectives included standardized neurological assessments (Friedreich Ataxia Rating Scale [FARS], International Cooperative Ataxia Rating Scale [ICARS], 9-Hole Peg Test [9HPT], Timed 25-Foot Walk, Low-Contrast Letter Acuity), general functional status (Activities of Daily Living), and cardiac assessments.

RESULTS

Deferiprone was well tolerated at 20mg/kg/day, whereas more adverse events occurred in the 40mg/kg/day than in the placebo group. The 60mg/kg/day dose was discontinued due to worsening of ataxia in 2 patients. One patient on deferiprone 20mg/kg/day experienced reversible neutropenia, but none developed agranulocytosis. Deferiprone-treated patients receiving 20 or 40mg/kg/day showed a decline in the left ventricular mass index, compared to an increase in the placebo-treated patients. Patients receiving 20mg/kg/day of deferiprone had no significant change in FARS, similar to the placebo-treated patients, whereas those receiving 40mg/kg/day had worsening in FARS and ICARS scores. The lack of deterioration in the placebo arm impaired the ability to detect any potential protective effect of deferiprone. However, subgroup analyses in patients with less severe disease suggested a benefit of deferiprone 20mg/kg/day on ICARS, FARS, kinetic function, and 9HPT.

INTERPRETATION

This study demonstrated an acceptable safety profile of deferiprone at 20mg/kg/day for the treatment of patients with FRDA. Subgroup analyses raise the possibility that, in patients with less severe disease, deferiprone 20mg/kg/day may reduce disease progression, whereas higher doses appear to worsen ataxia.

The oral iron chelator deferiprone protects against systemic iron overload-induced retinal degeneration in hepcidin knockout mice

PURPOSE

To investigate the retinal-protective effects of the oral iron chelator deferiprone (DFP) in mice lacking the iron regulatory hormone hepcidin (Hepc). These Hepc knockout (KO) mice have age-dependent systemic and retinal iron accumulation leading to retinal degeneration.

METHODS

Hepc KO mice were given DFP in drinking water from age 6 to 18 months. They were then compared to Hepc KO mice not receiving DFP by fundus imaging, electroretinography (ERG), histology, immunofluorescence, and quantitative PCR to investigate the protective effect of DFP against retinal and retinal pigment epithelial (RPE) degeneration.

RESULTS

In Hepc KO mice, DFP diminished RPE depigmentation and autofluorescence on fundus imaging. Autofluorescence in the RPE layer in cryosections was significantly diminished by DFP, consistent with the fundus images. Immunolabeling with L-ferritin and transferrin receptor antibodies showed a decreased signal for L-ferritin in the inner retina and RPE cells and an increased signal for transferrin receptor in the inner retina, indicating diminished retinal iron levels with DFP treatment. Plastic sections showed that photoreceptor and RPE cells were well preserved in Hepc KO mice treated with DFP. Consistent with photoreceptor protection, the mRNA level of rhodopsin was significantly higher in retinas treated with DFP. The mRNA levels of oxidative stress-related genes heme oxygenase-1 and catalase were significantly lower in DFP-treated Hepc KO retinas. Finally, ERG rod a- and b- and cone b-wave amplitudes were significantly higher in DFP-treated mice.

CONCLUSIONS

Long-term treatment with the oral iron chelator DFP diminished retinal and RPE iron levels and oxidative stress, providing significant protection against retinal degeneration caused by chronic systemic iron overload in Hepc KO mice. This indicates that iron chelation could be a long-term preventive treatment for retinal disease involving iron overload and oxidative stress.

Drug-induced reactivation of apoptosis abrogates HIV-1 infection

HIV-1 blocks apoptosis, programmed cell death, an innate defense of cells against viral invasion. However, apoptosis can be selectively reactivated in HIV-infected cells by chemical agents that interfere with HIV-1 gene expression. We studied two globally used medicines, the topical antifungal ciclopirox and the iron chelator deferiprone, for their effect on apoptosis in HIV-infected H9 cells and in peripheral blood mononuclear cells infected with clinical HIV-1 isolates. Both medicines activated apoptosis preferentially in HIV-infected cells, suggesting that the drugs mediate escape from the viral suppression of defensive apoptosis. In infected H9 cells, ciclopirox and deferiprone enhanced mitochondrial membrane depolarization, initiating the intrinsic pathway of apoptosis to execution, as evidenced by caspase-3 activation, poly(ADP-ribose) polymerase proteolysis, DNA degradation, and apoptotic cell morphology. In isolate-infected peripheral blood mononuclear cells, ciclopirox collapsed HIV-1 production to the limit of viral protein and RNA detection. Despite prolonged monotherapy, ciclopirox did not elicit breakthrough. No viral re-emergence was observed even 12 weeks after drug cessation, suggesting elimination of the proviral reservoir. Tests in mice predictive for cytotoxicity to human epithelia did not detect tissue damage or activation of apoptosis at a ciclopirox concentration that exceeded by orders of magnitude the concentration causing death of infected cells. We infer that ciclopirox and deferiprone act via therapeutic reclamation of apoptotic proficiency (TRAP) in HIV-infected cells and trigger their preferential elimination. Perturbations in viral protein expression suggest that the antiretroviral activity of both drugs stems from their ability to inhibit hydroxylation of cellular proteins essential for apoptosis and for viral infection, exemplified by eIF5A. Our findings identify ciclopirox and deferiprone as prototypes of selectively cytocidal antivirals that eliminate viral infection by destroying infected cells. A drug-based drug discovery program, based on these compounds, is warranted to determine the potential of such agents in clinical trials of HIV-infected patients.

Cost-utility analysis of deferiprone for the treatment of β-thalassaemia patients with chronic iron overload: a UK perspective

BACKGROUND

Patients with β-thalassaemia major experience chronic iron overload due to regular blood transfusions. Chronic iron overload can be treated using iron-chelating therapies such as desferrioxamine (DFO), deferiprone (DFP) and deferasirox (DFX) monotherapy, or DFO-DFP combination therapy.

OBJECTIVES

This study evaluated the relative cost effectiveness of these regimens over a 5-year timeframe from a UK National Health Service (NHS) perspective, including personal and social services.

METHODS

A Markov model was constructed to evaluate the cost effectiveness of the treatment regimens over 5 years. Based on published randomized controlled trial evidence, it was assumed that all four treatment regimens had a comparable effect on serum ferritin concentration (SFC) and liver iron concentration (LIC), and that DFP was more effective for reducing cardiac morbidity and mortality. Published utility scores for route of administration were used, with subcutaneously administered DFO assumed to incur a greater quality of life (QoL) burden than the oral chelators DFP and DFX. Healthcare resource use, drug costs (2010/2011 costs), and utilities associated with adverse events were also considered, with the effect of varying all parameters assessed in sensitivity analysis. Incremental costs and quality-adjusted life-years (QALYs) were calculated for each treatment, with cost effectiveness expressed as incremental cost per QALY. Assumptions that DFP conferred no cardiac morbidity, mortality, or morbidity and mortality benefit were also explored in scenario analysis.

RESULTS

DFP was the dominant strategy in all scenarios modelled, providing greater QALY gains at a lower cost. Sensitivity analysis showed that DFP dominated all other treatments unless the QoL burden associated with the route of administration was greater for DFP than for DFO, which is unlikely to be the case. DFP had >99 % likelihood of being cost effective against all comparators at a willingness-to-pay threshold of £20,000 per QALY.

CONCLUSIONS

In this analysis, DFP appeared to be the most cost-effective treatment available for managing chronic iron overload in β-thalassaemia patients. Use of DFP in these patients could therefore result in substantial cost savings.

The Oral Iron Chelator Deferiprone Protects Against Retinal Degeneration Induced through Diverse Mechanisms

PURPOSE

To investigate the effect of the iron chelator deferiprone (DFP) on sodium iodate (NaIO₃)-induced retinal degeneration and on the hereditary retinal degeneration caused by the rd6 mutation.

METHODS

Retinas from NaIO₃-treated C57BL/6J mice, with or without DFP cotreatment, were analyzed by histology, immunofluorescence, and quantitative PCR to investigate the effect of DFP on retinal degeneration. To facilitate photoreceptor quantification, we developed a new function of MATLAB to perform this task in a semiautomated fashion. Additionally, rd6 mice treated with or without DFP were analyzed by histology to assess possible protection.

RESULTS

In NaIO₃-treated mice, DFP protected against retinal degeneration and significantly decreased expression of the oxidative stress-related gene heme oxygenase-1 and the complement gene C3. DFP treatment partially protected against NaIO₃-induced reduction in the levels of mRNAs encoded by visual cycle genes rhodopsin (Rho) and retinal pigment epithelium-specific 65 kDa protein (Rpe65), consistent with the morphological data indicating preservation of photoreceptors and RPE, respectively. DFP treatment also protected photoreceptors in rd6 mice.

CONCLUSIONS

The oral iron chelator DFP provides significant protection against retinal degeneration induced through different modalities. This suggests that iron chelation could be useful as a treatment for retinal degeneration even when the main etiology does not appear to be iron dysregulation.

TRANSLATIONAL RELEVANCE

These data provide proof of principle that the oral iron chelator DFP can protect the retina against diverse insults. Further testing of DFP in additional animal retinal degeneration models at a range of doses is warranted.

The Oral Iron Chelator Deferiprone Protects Against Retinal Degeneration Induced through Diverse Mechanisms

PURPOSE

To investigate the effect of the iron chelator deferiprone (DFP) on sodium iodate (NaIO₃)-induced retinal degeneration and on the hereditary retinal degeneration caused by the rd6 mutation.

METHODS

Retinas from NaIO₃-treated C57BL/6J mice, with or without DFP cotreatment, were analyzed by histology, immunofluorescence, and quantitative PCR to investigate the effect of DFP on retinal degeneration. To facilitate photoreceptor quantification, we developed a new function of MATLAB to perform this task in a semiautomated fashion. Additionally, rd6 mice treated with or without DFP were analyzed by histology to assess possible protection.

RESULTS

In NaIO₃-treated mice, DFP protected against retinal degeneration and significantly decreased expression of the oxidative stress-related gene heme oxygenase-1 and the complement gene C3. DFP treatment partially protected against NaIO₃-induced reduction in the levels of mRNAs encoded by visual cycle genes rhodopsin (Rho) and retinal pigment epithelium-specific 65 kDa protein (Rpe65), consistent with the morphological data indicating preservation of photoreceptors and RPE, respectively. DFP treatment also protected photoreceptors in rd6 mice.

CONCLUSIONS

The oral iron chelator DFP provides significant protection against retinal degeneration induced through different modalities. This suggests that iron chelation could be useful as a treatment for retinal degeneration even when the main etiology does not appear to be iron dysregulation.

TRANSLATIONAL RELEVANCE

These data provide proof of principle that the oral iron chelator DFP can protect the retina against diverse insults. Further testing of DFP in additional animal retinal degeneration models at a range of doses is warranted.

The oral iron chelator deferiprone protects against iron overload-induced retinal degeneration

PURPOSE

Iron-induced oxidative stress may exacerbate age-related macular degeneration (AMD). Ceruloplasmin/Hephaestin double-knockout (DKO) mice with age-dependent retinal iron accumulation and some features of AMD were used to test retinal protection by the oral iron chelator deferiprone (DFP).

METHODS

Cultured retinal pigment epithelial (ARPE-19) cells and mice were treated with DFP. Transferrin receptor mRNA (Tfrc), an indicator of iron levels, was quantified by qPCR. In mice, retinal oxidative stress was assessed by mass spectrometry, and degeneration by histology and electroretinography.

RESULTS

DFP at 60 μM decreased labile iron in ARPE-19 cells, increasing Tfrc and protecting 70% of cells against a lethal dose of H(2)O(2). DFP 1 mg/mL in drinking water increased retinal Tfrc mRNA 2.7-fold after 11 days and also increased transferrin receptor protein. In DKOs, DFP over 8 months decreased retinal iron levels to 72% of untreated mice, diminished retinal oxidative stress to 70% of the untreated level, and markedly ameliorated retinal degeneration. DFP was not retina toxic in wild-type (WT) or DKO mice, as assessed by histology and electroretinography.

CONCLUSIONS

Oral DFP was not toxic to the mouse retina. It diminished retinal iron levels and oxidative stress and protected DKO mice against iron overload-induced retinal degeneration. Further testing of DFP for retinal disease involving oxidative stress is warranted.

Pharmacokinetic disposition of the oral iron chelator deferiprone in the white leghorn chicken

Deferiprone is a bidentate oral iron chelator used for the treatment of transfusional iron overload in people. The purpose of this study was to determine the pharmacokinetic disposition of deferiprone in the white leghorn chicken as a potential model upon which to base therapeutic regimens for the treatment of iron storage disease (hemochromatosis) in affected avian species. A suspension of deferiprone (DFP) was administered orally at a single dose of 50 mg/kg to 10 birds that were iron-loaded (IL-DFP) and 10 non--iron-loaded control birds (NIL-DFP). After a 30-day washout period, 5 birds from the NIL-DFP group were used for a bioavailability study of deferiprone administered intravenously at the same dose. Blood samples were collected at varying intervals over a 24-hour period and were analyzed for deferiprone by high-performance liquid chromatography, then plasma concentration versus time curves were developed. Deferiprone was rapidly absorbed from the gastrointestinal tract of the chicken, with plasma concentrations effective for iron chelation in humans (>20 micromol/L) maintained for at least 8 hours after oral dosing. The half-life (mean +/- SD) of the orally administered deferiprone in the IL-DFP and NIL-DFP groups was 2.91 +/- 0.78 hours and 3.61 +/- 0.90 hours, respectively, and was 2.42 +/- 0.24 hours for deferiprone administered intravenously. The mean oral bioavailability was 93%. Deferiprone is well absorbed and widely distributed in the chicken, with a longer half-life than reported in mammals.

Thiol Proteases: Inhibitors and Potential Therapeutic Targets

A better understanding of the biological roles and the pathological consequences of thiol-dependent enzymes has emerged in recent years, and hence considerable progress has been made in identifying and delineating cysteine proteases that can be considered promising drug targets from those involved in housekeeping functions. Cysteine proteases have been implicated in a wide variety of disease processes ranging from cardiovascular, inflammatory, viral and immunological disorders to cancer. The first milestone in drug development of cysteine protease inhibitors has probably been reached, as IDN-6556 (a broad spectrum caspase inhibitor) has recently received Orphan Drug label by the U.S. Food and Drug Administration for use in the treatment of the patients undergoing liver transplantation and other solid organ transplantation. IDN-6556, which blocks apoptosis, is in Phase II human clinical trial in patients undergoing liver transplantation. In addition, more than ten cysteine protease inhibitors are presently at various phases of clinical development/trials for diverse diseases. This review emphasises on the new development from the literature reports since the year 2000 in the exploration of potential cysteine proteases as prospective drug targets, and the investigation of promising inhibitors that can potentially be developed for the treatment of human diseases. Transglutaminases, another class of thiol-dependent enzymes, are not discussed here.

Transport kinetics of iron chelators and their chelates in Caco-2 cells

PURPOSE

Caco-2 monolayers were used to contrast the bidirectional transport of iron chelators and their chelates and to estimate fundamental kinetics associated with their intestinal absorption.

METHODS

Bidirectional transport was studied at 37 degrees C and pH 7.4 using 500-microM concentrations. Monolayer integrity was tested via transepithelial electrical resistance and sodium fluorescein permeability. Apical and basolateral analysis provided mass balance evidence. Apparent permeability coefficient (P(app)) served to rank and compare molecules and estimate in vivo bioavailability. Model-dependent rate constants defined cellular influx and efflux.

RESULTS

1) P(app) ranked in decreasing order for chelators from directional transport studies were CP363 > deferiprone> ICL670 > CP502 > deferoxamine (DFO). 2) Fe(CP502)(3), Fe(ICL670)(2), and FeDFO were not measurable in receiving chambers, whereas Fe(deferiprone)(3) and Fe(CP363)(3) were detected in both directions. 3) CP363 was transported significantly faster from the basolateral to the apical direction than the converse. 4) Mass balance of donor and receiver chambers gave approximately 100% recovery in all cases. 5) Kinetic analysis supports the view that the Caco-2 chelator efflux constants are generally greater than their influx constants.

CONCLUSIONS

Caco-2 cells are useful in screening iron chelators and chelates and estimating bioavailabilities. Structure and distribution coefficients partially predict passive transport through Caco-2 monolayers.

Validated HPLC assay for iron determination in biological matrices based on ferrioxamine formation

A simple, robust and reproducible HPLC method has been developed and validated for iron determination in biological matrices. It is based on chelation with desferrioxamine (DFO) and the measurement of the chelate ferrioxamine (FO). The method was developed to permit monitoring of iron bio-kinetics and estimation of iron status in experimental animals. The chromatography was performed on a stainless steel XTerra MS C18 column (Waters; 250 mm x 4.6 mm i.d., 5 microm) using a gradient of Tris-HCl buffer (10mM, pH 5) and acetonitrile. The method was validated in terms of selectivity, linearity (0.3-80 nmol on-column), limit of detection (0.2 nmol on-column), low limit of quantification (0.3 nmol on-column), recovery (91-102%), intra- and inter-day reproducibility, stability, and robustness. The method's universal applicability was illustrated by monitoring plasma and heart iron kinetic profiles in rats after a single intraperitoneal (i.p.) injection of 200mg/kg iron dextran.

Medicinal chemistry and properties of 1,2,4-thiadiazoles

1,2,4-Thiadiazole is a distinctive class of small heterocyclic thiol trapping agents that serve as an interesting pharmacophore in the design of inhibitors targeting the cysteine residues of proteins. X-Ray crystal structures of enzyme-inhibitor complex indicate that the cysteine thiol reacts with the N-S bond of the thiadiazole moiety to form a disulfide bond resulting in the inactivation of the enzymes. This review addresses the medicinal chemistry and various properties of 1,2,4-thiadiazoles in their potential as new electrophilic "warheads" for targeting the cysteine residues of biomolecules (e.g, H+/K+ ATPase), and cysteine-dependent enzymes (e.g., cathepsin B and transglutaminase).

3-Substituted imidazo[1,2-d][1,2,4]-thiadiazoles: a novel class of factor XIIIa inhibitors

A new class of selective FXIIIa inhibitors with a bicyclic [1,2,4]-thiadiazole pharmacophore is described. At 160 muM, compound 8 caused 50% reduction in fibrin gamma-chain cross-linking and suppressed the polymerization of alpha chains in platelet-depleted human plasma clots. Fibrinolysis rates in response to tissue plasminogen activator were directly proportional to the concentration of 8 in plasma at the time of clotting.

Pharmacokinetic studies of a novel 1,2,4-thiadiazole derivative, inhibitor of Factor XIIIa, in the rabbit by a validated HPLC method

Activated Factor XIII (FXIIIa) stabilizes fibrin clot by covalent cross-linking of fibrin strands in the fibrin, making it resistant to physiological and pharmacologically induced fibrinolysis. Inhibition of Factor XIIIa offers a novel approach to treatment of thrombosis. Selected derivatives of 1,2,4-thiadiazoles, presently in discovery and development, may offer new treatment strategies as inhibitors of Factor XIIIa. In order to evaluate its pharmacokinetic (PK) profile and to facilitate the selection of drug candidates for drug discovery and development process, we developed and validated a simple and selective reversed-phase high-performance liquid chromatographic method (RP-HPLC) with UV detection for the determination of N-[6-(imidazo[1,2-d][1,2,4]thiadiazol-3-ylamino)hexyl]-2-nitrobenzensulfonamide (5624) in rabbit plasma. The plasma protein precipitation and sample preparation was achieved by using acetonitrile, followed by organic phase evaporation to dryness and the residue reconstitution in the mobile phase. The 5624 recovery from the plasma was about 90%. Chromatography was performed on a C18 column using a gradient of acetonitrile in water as a mobile phase. A chemically related compound, N-[6-(imidazo[1,2-d][1,2,4]thiadiazol-3-ylamino)hexyl]naphthalene-1-sulfonamide (5422), was used as an internal standard. Limit of detection (LOD), based on signal to noise ratio>3, was 0.2 microM (on-column amount of about 7 ng), while limit of quantification (LOQ), based on signal to noise ratio>10, was 0.5 microM (on-column amount of about 20 ng). The plasma samples for the PK study were collected at defined time points during and after 5624 slow intravenous infusion (25 mg/kg) to male White New Zealand rabbits and analyzed by RP-HPLC method. The PK parameters, such as half-life, volume of distribution, total clearance, elimination rate constant etc., were determined. The PK profile of 5624 offered insights in the design and development of additional new compounds, derivatives of 1,2,4-thiadiazole, with desired PK properties.

Metabolic and pharmacokinetic evaluation of a Novel 3-hydroxypyridinone iron chelator, CP502, in the rat

A recently synthesized 3-hydroxypyridinone derivative with an amido function at the 2-position, CP502 (1,6-dimethyl-3-hydroxy-4-(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride), exhibited high in vitro iron chelating potency (pFe3+ =21.7). It was targeted as a new iron-chelating candidate for further development in early pre-clinical testing. To evaluate its pharmacokinetics, including oral bioavailability, metabolic and disappearance profiles, studies were conducted in Sprague Dawley male rats. A single 150 mg/kg intravenous and oral dose was given to male Sprague Dawley rats (N=6, B.Wt. 250g). The rats were placed in metabolic cages and fasted overnight before the dosing. Venous blood samples (200 microL per withdrawal) were collected at defined time points before (blank) and up to 28 h post administration. Urine and feces were collected before dosing (blank) and in 24 h intervals up to 72 h post administration. Plasma CP502 concentration versus time profiles were consistent with two-compartment distribution, and the oral bioavailability approached 100%. Total clearance and mean residence time (i.v.) were 1.02 L/kg/h and 1.10 h, respectively. Simultaneous computer fitting yielded V1 and Vss estimates of 0.96 L/kg and 1.74 L/kg, respectively. CP502 was mainly excreted unchanged via urine (45.29+/-9.40 % of total dose) or as glucuronide (6.46+/-1.22% of total dose). High iron chelation potential and favorable pharmacokinetic and metabolic profiles indicate that CP502 is a promising candidate for further development.

Improved high-performance liquid chromatographic method for the pharmacokinetic studies of a novel iron chelator, CP502, in rats

An improved reverse-phase high-performance liquid chromatographic method (RP-HPLC) for the determination of a novel iron chelator CP502 (1,6-dimethyl-3-hydroxy-4-(1H)-pyridinone-2-carboxy-(N-methyl)-amide hydrochloride) in rat plasma, urine and feces was developed and validated. The separation was performed on a polymeric column using a mobile phase composed of 1mM ethylenediaminetetra-acetic acid disodium salt (EDTA), acetonitrile, methanol and methylene chloride. Separation of CP502 from plasma, urine or feces endogenous compounds was achieved by gradient elution. Retention times of CP502 and its major metabolite (glucuronide) were about 13 and 4 min, respectively. The method was validated in terms of limit of detection (LOD), limit of quantification (LOQ), selectivity (endogenous from plasma, urine or feces), linearity, extraction recovery, robustness (column selection, mobile phase composition, detection mode, internal standard (IS) selection, analyte stability), day-to-day reproducibility and system suitability (repeatability, peak symmetry and resolution). The method is applicable to bioavailability and pharmacokinetic studies of CP502 in rats.

Chromosomal aberration frequencies in patients with thalassaemia major undergoing therapy with deferiprone and deferoxamine in a comparative crossover study

Measurements of chromosomal aberrations were made in 10 thalassaemia major patients treated long-term with deferiprone (at least 5 years) and compared with an equal number of patients matched for age, sex and iron overload, treated long-term with deferoxamine. Two blood samples were collected from each patient, 7 and 20 days after a transfusion episode, and the frequency of chromosomal aberrations (gaps, breaks and exchanges) in the patients' circulating lymphocytes analysed in both samples using standard cytogenetic staining techniques. The frequency of reciprocal translocations was also analysed using fluorescence in situ hybridization. Relatively low frequencies of cells with stable and unstable aberrations were seen at both sampling times in all patients, with no statistically significant differences between sexes. Chromosomal aberrations were less frequent in patients treated long-term with deferiprone than in patients treated with deferoxamine, although the difference did not reach statistical significance. After the second blood sample had been collected, all patients had their iron chelation therapy switched to the other chelator. Patients treated long-term with deferiprone had their therapy switched to deferoxamine and patients treated long-term with deferoxamine had their therapy switched to deferiprone. After the switch, two further blood samples were collected 7 and 20 days after transfusion for each of the next two transfusion cycles in all patients. Analysis of the post-switch samples also revealed a slightly higher frequency of chromosomal aberrations during therapy with deferoxamine than with deferiprone at all time points. A small, but statistically significant, increase in cells with aberrations was observed at the first post-switch assessment in the group of patients whose therapy was switched from deferiprone to deferoxamine, whereas the switch from deferoxamine to deferiprone was associated with a decrease in the frequency of chromosomal aberrations. The results of the study demonstrate that, in a clinical setting, deferiprone has no greater clastogenic activity than that of deferoxamine.

Iron chelator research: past, present, and future

The occurrence of in vivo iron toxicity in the human body can be categorized into iron overload and non-iron overload conditions. Iron overload conditions are common in beta-thalassemia and hereditary hemochromatosis patients, and anthracycline mediated cardiotoxicity is an example of a non-iron overload condition in cancer patients, in which the toxicity is iron-dependent. While hundreds of iron chelators have been evaluated in animal studies, only a few have been studied in humans. Examples of iron chelator drugs are desferrioxamine (DFO), deferiprone (L1), and dexrazoxane (ICRF 187). The compound ICL670 has completed phase II clinical trials and a phase III trial is planned in 2003. Triapine is currently in phase II clinical trial as an anticancer agent. CP502, GT56-252, NaHBED, and MPB0201 are examples of new chelators in preclinical/clinical development. In the past decade, many new viable utilities for iron chelators have been reported. This includes the use of iron chelators as antiviral, photoprotective, antiproliferative, and antifibrotic agents. This review will focus on the status of drug development for the treatment of iron overload in patients with beta-thalassemia and the potential use of iron chelators in the prevention and treatment of other diseases.

Impairment of pyruvate dehydrogenase activity by acetaldehyde

The facial features that are characteristic of fetal alcohol syndrome (FAS) are strikingly similar to those seen in pyruvate dehydrogenase (PDH) deficiency. Furthermore, alcohol-induced central nervous system insult results in midline anomalies such as agenesis of the corpus callosum, which has also been described in several metabolic diseases, including PDH deficiency. The purpose of this work was to examine the effect of acetaldehyde on PDH in vitro. The activity of PDH was measured in the presence of acetaldehyde (10 microM-1 mM) by measuring the formation of the reduced form of nicotinamide-adenine dinucleotide at 340 nm. Pyruvate dehydrogenase was separated by using the sodium dodecyl sulfate-polyacrylamide gel electrophoresis technique after incubation with [1,2-(14)C]-acetaldehyde to detect the formation of covalent adducts autoradiographically. The effect of acetaldehyde on the phosphorylation of the complex was also determined autoradiographically after incubating of PDH with (32)P-adenosine triphosphate. The results of this study show that acetaldehyde impairs PDH activity by a mixed inhibition type mechanism (Kic=62.4+/-25.7 microM, Kiu=225+/-68 microM), which is not a result of the formation of covalent adducts with PDH, nor of a stimulation of phosphorylation or inactivation of the complex. Because PDH levels are low throughout development and that the competition between pyruvate and acetaldehyde may be enhanced due to ethanol-induced lowering of ambient pyruvate concentrations, we conclude that impairment of PDH may have a significant effect on the developing fetus.

Dose-Response Relationship and Reproducibility of the Fall in Exhaled Nitric Oxide After Inhaled Beclomethasone Dipropionate Therapy in Asthma Patients

STUDY OBJECTIVES

The fractional concentration of exhaled nitric oxide (FENO) is a marker of asthmatic airway inflammation. We determined the dose response and the reproducibility of the FENO fall following inhaled beclomethasone dipropionate (iBDP) therapy in nonsteroid-treated asthmatic patients.

STUDY DESIGN

Study A: For four 1-week periods (period 1 to period 4), the following regimens were administered in sequential order to 15 nonsteroid-treated asthmatic patients: period 1, placebo; period 2, 100 microg/d of iBDP; period 3, 400 microg/D of iBDP; and period 4, 800 microg/d of iBDP. Spirometry, FENO, and provocative concentration of methacholine resulting in a 20% fall in FEV(1) (PC(20)) were measured at each of five visits (visit 1 to visit 5). Study B: During four periods, 12 nonsteroid-treated asthmatic patients received placebo treatment for 7 days (period 1), 200 microg/d of iBDP for 14 days (period 2), washout on placebo treatment until the FENO was within 15% of baseline (period 3), and 200 microg/d of iBDP for 14 days (period 4).

RESULTS

Study A: Mean FEV(1) rose progressively from 3.10 L (visit 1) to 3.41 L (visit 5; p = 0.001). All iBDP doses caused a significant FEV(1) rise compared to placebo treatment, but with no significant separation of doses using FEV(1). FENO geometric mean (95% confidence limits) fell progressively from 103.5 parts per billion (ppb) (78.5 to 136.7) to 37.4 ppb (29.1 to 48.0) from visit 1 to visit 5 (p = 0.001). All doses of iBDP resulted in a significant change in FENO from placebo treatment, but with significant separation of only the 100-microg and 800-microg doses by FENO. Geometric mean (95% confidence limits) PC(20) rose progressively from 0.01 mg/mL (0.00 to 0.19) to 0.48 mg/mL (0.01 to 8.1) from visit 1 to visit 5 (p = 0.002). All doses of iBDP resulted in a significant change in PC(20) from baseline or placebo treatment, but with no significant separation of active iBDP doses using PC(20). Study B: FENO fell from 111.56 ppb (80.3 to 155.1) to 66.3 ppb (49.2 to 89.5; p < 0.001) from period 1 to period 2, and from 110.2 ppb (79.3 to 153.1) to 61.7 ppb (42.9 to 88.8; p < 0.001) from period 3 to period 4. There were no significant differences between FENO in period 1 and period 3 (p = 0.83) or between period 2 and period 4 (p = 0.220).

CONCLUSIONS

FENO was superior to FEV(1) and PC(20) in separating doses of iBDP. The fall in FENO after two identical administrations of iBDP separated by placebo washout was highly reproducible.

High-performance liquid chromatographic assays for a second-generation novel oral iron chelator (APCP363) and their application to pharmacokinetic studies in rats

Sensitive and specific HPLC assays for APCP363 in biological matrices (rat plasma, urine and feces) were developed. The recovery of APCP363 ranged from 81.2 to 99.9% in plasma, from 82.1 to 92.8% in urine, and from 65 to 68% in feces. Standard deviations were below 10% for all analyses. The limits of quantitation were 0.1, 10 and 30 microg/ml in plasma, urine and feces, respectively. The HPLC assays, which are the first reports for APCP363 analysis in biological matrices, have been successfully applied to preliminary pharmacokinetic studies in rats. The stool assay is the first non-radiolabeled method for hydroxypyridinones in feces.

Dissolution and in vivo evidence of differences in reference products: impact on development of generic drugs

The WHO List of International Comparator Pharmaceutical Products (CPP) For Equivalence Assessment of Interchangeable Multi-Source (Generic) Products will address an important issue in developing new generic drugs because it will identify the 'correct' reference product. This list will reduce unnecessary clinical studies in jurisdictions requiring new generics to be compared with brand products sold locally. Eventually, by employing the CPP, there will be a world-wide standard for brand and generic drugs, assuring the same level of quality internationally. The strategy of a single global reference is meritorious, but there are several hurdles to overcome. Most important is that the same brand may differ in dissolution and/or bioavailability in various jurisdictions, including some drugs with a narrow therapeutic index like phenytoin. Several examples are provided in this manuscript. This issue of regional differences has relevance, not only to the WHO list, but also to the matter of how safety and efficacy was established for that product in the first place. Normally, phase III clinical studies are conducted on a product manufactured in a single site, set to one standard. If the product differs in bioavailability in different jurisdictions, one is left with the question: 'which product has remained true to the original formulation?' Alternatively, if safety and efficacy is maintained with all formulations, then one is faced with the question: 'are the criteria currently employed for bioequivalence unnecessarily restrictive?'

Hypothetical framework for enhanced renal tubular secretion of drugs in cystic fibrosis

Several clinical studies demonstrate reduced serum concentrations of renally excreted drugs in patients with cystic fibrosis (CF). To explain this phenomenon, we propose a model supporting increased proximal tubular secretion of certain drugs in individuals with CF. We hypothesize that the chloride channel located on the apical surface of renal proximal tubular cells and controlled by the cystic fibrosis transmembrane conductance regulator (CFTR) operates suboptimally in CF patients, and that the abnormal CFTR decreases Cl- reabsorption, resulting in an increased concentration of Cl- in the tubular lumen. We postulate that, in an effort to maintain homeostasis, luminal Cl- moves intracellularly in exchange for organic anions. The result of stimulating this anion exchanger is an increased rate of organic anion secretion by the renal tubule. Hence, due to enhanced tubular secretion, individuals with CF demonstrate increased tubular clearance of organic anion drugs, resulting in lower steady state serum concentrations.

High variability in drug pharmacokinetics complicates determination of bioequivalence: experience with verapamil

PURPOSE

For the assessment of bioequivalence it is assumed that drug clearance in each subject on each of the study days is the same and any observed differences in AUC and/or Cmax between a brand and generic formulation are due to differences in bioavailability. We hypothesized that this assumption was invalid for highly variable drugs such as verapamil and tested it by comparing bioavailability for the brand vs itself.

METHODS

To avoid any contribution from potential formulation differences, we evaluated bioavailability for isoptin SR 240 mg tablets in 9 healthy volunteers on 2 occasions separated by 1 week as part of a larger study. A validated HPLC assay was used to measure serial blood samples over 36 hours.

RESULTS

The AUC0-1 varied 3.8 fold among subjects and 5/9 subjects had > 30% difference in AUC0-1 on the 2 days. After log transformation, the mean AUC0-1 +/- %cv (ng.h/mL) on Occasion 1 (878 +/- 38) was 23% greater (p = 0.031) than on Occasion 2 (713 +/- 41). The 90% confidence interval of Occasion 1/Occasion 2 was 106-143%. The Cmax varied > 9 fold (30-278 ng/mL) among subjects. The intrasubject difference between days ranged from -46% to +298%. The 90% confidence interval was 72-152% for Cmax. Since the same lot of Isoptin was used in the same subjects on 2 occasions, the observed differences must be due to biological variability in verapamil pharmacokinetics, not formulation differences.

CONCLUSIONS

The intra-subject biological variability complicates bio-equivalence assessment and can lead to an erroneous assumption of bioinequivalence.

Comparisons between oral and intraperitoneal 1,25-dihydroxyvitamin D3 therapy in children treated with peritoneal dialysis

Recent studies in adults have suggested that parenteral 1,25-dihydroxyvitamin D3 (1,25[OH]2D3) may have advantages over oral therapy in the management of renal osteodystrophy. The purpose of this study was to determine whether there were clear differences between oral and IP 1,25(OH)2D3 treatments in children who did not pose a treatment problem. Seven children (5 males, 2 females, aged 1.8 to 16 years, median 4.8 years) undergoing peritoneal dialysis were initially treated with oral 1,25(OH)2D3 for a one month equilibration period They were randomly assigned to 3 months of either oral or intraperitoneal (IP) therapy with 1,25(OH)2D3 followed by 3-months-treatment using the alternative route. No significant differences in serum creatinine, phosphate, or parathyroid hormone concentrations were found between the different routes of administration in the patients. No significant differences in height standard deviation scores or renal osteodystrophy scores were found over the six-month study. Paired oral and IP pharmacokinetic studies were performed on these 7 patients and 2 other children who had been treated for at least 2 months using either oral or IP 1,25(OH)2D3. Serum was taken prior to one of the usual 1,25(OH)2D3 doses and 0.5, 1.5, 3, 6, and 24 h afterward. The highest measured concentrations of 1,25(OH)2D3 were found at 1.5 h for both oral and IP treatments (mean Cmax [SD]: oral 116 [23] pmol/l, IP 121 [24] pmol/l, p > 0.05). The AUC's for oral and IP therapy were similar (1701 [276] and 1645 [301] pmol/h/l, respectively). In the paired pharmacokinetic studies no significant differences were found between oral and IP treatments for the serum half life (27.4 [11.6] h and 19.2 [8.1] h, respectively) and total body clearance (15.3 [2.1] h and 18.4 [3.3] h, respectively) of 1,25(OH)2D3. In children who respond appropriately to oral 1,25(OH)2D3 there is no biological advantage to the use of IP 1,25(OH)2D3.

Neonatal withdrawal syndrome: associated drugs and pharmacologic management

Use of addicting drugs among women during pregnancy exposes newborns to potentially serious disorders. A group of symptoms referred to as neonatal withdrawal syndrome (NWS) may occur in infants born to mothers addicted to certain drugs because, at birth, the infants suddenly are cut off from the drug supply. Classes of drugs that cause NWS are those that produce addiction in adults, including the opioids (heroin, methadone, morphine), barbiturates, alcohol, and benzodiazepines. Many of the manifestations of NWS occur regardless of the class of drug, including irritability, hyperactivity, abnormal sleep pattern, high-pitched cry, tremor, vomiting, diarrhea, weight loss, and failure to gain weight. The fact that these symptoms are nonspecific makes it difficult to identify NWS unless it is specifically looked for. The onset, duration, and severity of the disorder differ based on such factors as the addictive drug used, time and amount of mother's last dose, and rate of elimination of the drug from the newborn. Pharmacologic intervention may be required to control severe symptoms and signs. The most common drugs used to modify withdrawal are phenobarbital, paregoric, chlorpromazine, and diazepam. Treatment is complicated by conflicting information on the effectiveness of various agents.

Are current pediatric dose recommendations for intravenous theophylline appropriate?

Theophylline, a first-line antiasthma drug, is often associated with severe toxicity even when taken in the recommended schedule. Theophylline toxicity has been associated with upper respiratory tract infections (URTI) due to reduced total-body clearance of theophylline. Some researchers believe this inhibition stems from a direct effect of viruses, but others postulate it is a result of the fever. We examined whether current theophylline dose recommendations are appropriate for children with acute asthma with a concurrent URTI. We also wished to elucidate whether the viral infection or the fever inhibits theophylline clearance. A total of 2254 medical records of asthmatic children admitted to The Hospital for Sick Children in Toronto were reviewed between 1987 and 1990. Clearance rate was calculated as the ratio between the infused dose rate and measured steady-state concentrations. Subsequently, these clearance rates were used to calculate steady-state concentrations that would be achieved by the recommended dose rates of theophylline. Reduced theophylline clearance was associated with the presence of URTI (p = 0.029) but not fever. Age correlated significantly with theophylline clearance (p = 0.027). If these children were to receive the recommended intravenous dose rate of theophylline, two-thirds of them would achieve steady-state serum concentrations above 15 mg/L, and one-third would achieve concentrations above 20 mg/L. Reevaluation of the present recommended theophylline dose rate is needed, as the majority of children requiring intravenous theophylline have a concurrent URTI with compromised total-body clearance. A correction factor of 60% is recommended to adjust the dose rate during an URTI. If utilized by prescribing physicians, it may reduce theophylline toxicity during an URTI episode.

Use of an isolated in situ canine lung perfusion model to evaluate dopamine clearance by the lung

An isolated in situ lung perfusion model was used to assess dopamine clearance by the lungs in 12 dogs. The preparation consisted of a closed perfusion system in situ, in which systemic arterial blood supply was interrupted. Blood flow to the lungs was maintained at presurgery flow rates. The inflow was restricted to the lungs by the pulmonary arteries and outflow was limited to the pulmonary veins. Pulmonary artery pressure, temperature and pO2 were maintained at physiological levels. After confirmation of a stable base line, one of 3 doses (1, 2, or 5 micrograms/kg/min) of dopamine was infused over 30 min to achieve steady-state blood concentrations, then blood samples were drawn at specified times during and after the infusion. Dopamine plasma concentrations were analyzed by high performance liquid chromatography with electrochemical detection. Dose-dependent disposition of dopamine was observed in both plasma concentration-time profiles and in clearance (20.3 +/- 9.6 ml/min/kg at 5 micrograms/kg/min vs. 41.6 +/- 19.1 ml/min/kg at 1 micrograms/kg/min, P = 0.038). A sham experiment revealed that the blood in this experimental preparation contributed less than 10% to the total clearance of dopamine. This study revealed that our isolated in situ model is an excellent method to evaluate the role of the lungs in drug removal. Furthermore, it confirmed that the lungs contribute to the clearance of dopamine from the body.

Ciprofloxacin in patients with mycobacterial infections: experience in 15 patients

In vitro and animal investigations have demonstrated the antimycobacterial activity of some fluoroquinolones, including ciprofloxacin, but information regarding their clinical usefulness in mycobacterial infections is sparse. This article presents treatment results of 11 patients with tuberculosis and 4 with atypical mycobacterial infections. They were treated with combinations of ciprofloxacin and one or two other antituberculosis agents. Susceptibility of the infecting organisms to ciprofloxacin was determined in 14 of the 15 patients: in 12 of them, minimum inhibitory concentrations ranged between 0.31 and 1.25 micrograms/mL, suggesting a good level of activity. Serum concentrations of ciprofloxacin, sampled one hour after dosing and measured by a specific HPLC assay, revealed considerable variability (range 0.22-8.41 micrograms/mL). Serial plasma samples taken under controlled conditions suggested that a decreased rate of absorption was responsible for low one-hour concentrations in one of the subjects. Adverse reactions to ciprofloxacin were few and included nausea in four patients, crystalluria in one, and febrile reaction in another. A satisfactory response in terms of clinical and radiologic improvement, bacteriologic conversion, and absence of relapse was seen in 13 of the 14 patients who completed an adequate course of therapy. A controlled clinical trial of this promising antimycobacterial agent is needed.

Effects of cisapride in patients with cystic fibrosis and distal intestinal obstruction syndrome

In a double-blind, placebo-controlled, crossover trial, we investigated the effects of the prokinetic drug cisapride in patients with cystic fibrosis and chronic recurrent distal intestinal obstruction syndrome (DIOS). After a baseline period, 17 patients (12.9 to 34.9 years; 12 boys) received, in random order, cisapride (7.5 to 10 mg) and placebo three times daily by mouth, each for 6 months. Gastrointestinal symptoms (flatulence, abdominal pain, fullness, abdominal distension, nausea, anorexia, heartburn, diarrhea, vomiting and regurgitation) were scored three times monthly and physical examinations assessed. At baseline and at each 6-month period, assessment included food intake for 7 days, 3-day stool collection, pulmonary function tests, and abdominal radiographs. During cisapride therapy compared with placebo, there were significant reductions in flatulence (p less than 0.005), fullness, and nausea (p less than 0.05). Patients with the worst symptom scores benefited most from cisapride. With cisapride, 12 patients felt better and three worse (p less than 0.05); physicians judged 11 patients improved and two worse (p less than 0.05). No side effects were noted. There were no significant differences between cisapride and placebo periods in nutritional status, x-ray scores, pulmonary function, food intake (fat, protein, calories), stool size and consistency, and fecal losses of fat, bile acids, chymotrypsin, and calories. For acute episodes of DIOS, intestinal lavage was needed 6 times in 4 patients during treatment with cisapride, and 11 times in 6 patients receiving placebo. In comparison with unselected patients with cystic fibrosis and pancreatic insufficiency who were receiving enzyme supplements and who had no distal intestinal obstruction, fecal fat losses (percentage of intake) were almost twice as high in the study group with DIOS (31.2 +/- 20.6% vs 16.2 +/- 17.6%; p less than 0.01). We conclude that in the dosage used, long-term treatment with cisapride appears to improve chronic abdominal symptoms in patients with cystic fibrosis and DIOS, but fails to abolish the need for intestinal lavage. Cisapride treatment had no effect on digestion and nutritional status of cystic fibrosis patients with pancreatic insufficiency.

Angiotensin converting enzyme inhibitor therapy to decrease microalbuminuria in normotensive children with insulin-dependent diabetes mellitus

It has been proposed that lowering glomerular pressure in children with insulin-dependent diabetes mellitus will reduce microalbuminuria and that this reduction may preserve renal function. We therefore conducted a double-blind, placebo-controlled, crossover trial to compare 3 months of treatment with the angiotensin converting enzyme inhibitor captopril (0.9 mg/kg/day), and 3 months of placebo administration to 12 normotensive adolescents with insulin-dependent diabetes mellitus, 11 with microalbuminuria (albumin excretion rate of 15 to 200 micrograms/min) and one with early overt nephropathy. Mean age (+/- SD) was 14.4 +/- 1.7 years, and disease duration was 5.1 +/- 2.5 years. Albumin excretion rate decreased significantly during captopril therapy (baseline 78 +/- 114 micrograms/min; mean of monthly measurements 38 +/- 55 micrograms/min vs placebo 78 +/- 140 micrograms/min; p less than 0.001). During captopril therapy, albumin excretion was reduced by 41 +/- 44% and decreased in 10 of 12 subjects, but was unchanged in two, one with a borderline albumin excretion rate (16.3 micrograms/min) and one with diabetes of short duration (2.9 years). Plasma renin activity rose significantly during captopril therapy, and mean arterial pressure decreased slightly (placebo 81 +/- 7 mm Hg; captopril 76 +/- 5 mm Hg; p = 0.004). After 3 months of captopril treatment, glomerular filtration rate and renal plasma flow did not change significantly. Hemoglobin Alc values remained stable during the study. The only side effect of captopril was diarrhea in one patient. We conclude that, in the short term, captopril is effective in decreasing albumin excretion rate in normotensive children with insulin-dependent diabetes mellitus and microalbuminuria, without significant side effects. Longer trials are indicated in an attempt to delay or prevent overt nephropathy.

Pharmacokinetic analysis of cloxacillin loss in children undergoing major surgery with massive bleeding

To determine the magnitude of cloxacillin loss during surgical procedures involving significant blood loss and high fluid replacement, we compared the pharmacokinetics of cloxacillin in children during craniomaxillofacial surgery with the disposition of the drug in healthy young adult volunteers with intact circulation. Blood loss during craniofacial operations may exceed blood volume, in some cases by as much as three times. Hemodynamic replacement with electrolyte solutions and blood products, which do not contain the drug, further dilute cloxacillin concentrations. In the patients that we studied, mean drug loss was estimated at 71%. Cloxacillin concentrations in serum fell below the lower range of the MIC for Staphylococcus aureus during significant portions of the surgical procedures. Thus, the traditional dosing of cloxacillin during prolonged operations with massive blood loss is inadequate. A more frequent dosing interval or priming of all replacement fluids with the drug may be required to maintain therapeutic levels. Our findings suggest that massive blood loss is likely to have a dramatic effect on the level of any drug with a small distribution volume. If such a drug is essential to the patient's well-being (e.g., antibiotics, antiarrhythmics, and anticonvulsants), it must be replaced promptly.

Pharmacokinetics of drugs in cystic fibrosis

Considerable work has been conducted on patients with CF to clearly demonstrate enhanced clearances of many, but not all drugs. The precise mechanisms for enhanced drug clearance in CF remain to be elucidated, and it will be important to examine the two major organs of drug elimination, the kidney and liver, for answers to these questions. Although it has not been studied to date, the role of the lung as a contributor to enhanced drug clearance in CF needs to be considered as well. In the liver it appears that both hepatic biotransformation as well as biliary excretion may be enhanced. In the kidney, there is enhanced CL of acidic drugs, but variable findings for cationic and zwitterionic drugs. The latter finding can be explained on the basis of the pKa of the drugs and the urine pH. It would be most appealing if enhanced renal and nonrenal clearance of drugs in CF could be attributed to a common single defect. At this time, there is no obvious candidate, although altered transmembrane transport would represent a place to start.