Neurological effects of recombinant human erythropoietin in Friedreich's ataxia: a clinical pilot trial

Therapeutic Biomarkers in Friedreich's Ataxia: a Systematic Review and Meta-analysis

Although a large array of biomarkers have been investigated in Friedreich's ataxia (FRDA) trials, the optimal biomarker for assessing disease progression or therapeutic benefit has yet to be identified. We searched PubMed, MEDLINE, and EMBASE databases up to June 2023 for any original study (with ≥ 5 participants and ≥ 2 months' follow-up) reporting the effect of therapeutic interventions on any clinical, cardiac, biochemical, patient-reported outcome measures, imaging, or neurophysiologic biomarker. We also explored the biomarkers' ability to detect subtle disease progression in untreated patients. The pooled standardized mean difference (SMD) was calculated using a random-effects model. The study's protocol was registered in PROSPERO (CRD42022319196). In total, 43 studies with 1409 FRDA patients were included in the qualitative synthesis. A statistically significant improvement was observed in Friedreich Ataxia Rating Scale scores [combining Friedreich Ataxia Rating Scale (FARS) and modified FARS (mFARS): SMD =  - 0.32 (- 0.62 to - 0.02)] following drugs that augment mitochondrial function in a sensitivity analysis. Left ventricular mass index (LVMI) was improved significantly [SMD =  - 0.34 (- 0.5 to - 0.18)] after 28.5 months of treatment with drugs that augment mitochondrial function. However, LVMI remained stable [SMD = 0.05 (- 0.3 to 0.41)] in untreated patients after 6-month follow-up. None of the remaining biomarkers changed significantly following any treatment intervention nor during the natural disease progression. Nevertheless, clinical implications of these results should be interpreted with caution because of low to very low quality of evidence. Further randomized controlled trials of at least 24 months' duration using a biomarker toolbox rather than a single biomarker are warranted.

Recent Advances in the Treatment Strategies of Friedreich's Ataxia: A Review of Potential Drug Candidates and their Underlying Mechanisms

BACKGROUND

Friedreich's Ataxia (FRDA) is a rare hereditary neurodegenerative disorder characterized by progressive ataxia, cardiomyopathy, and diabetes. The disease is caused by a deficiency of frataxin, a mitochondrial protein involved in iron-sulfur cluster synthesis and iron metabolism.

OBJECTIVE

This review aims to summarize recent advances in the development of treatment strategies for FRDA, with a focus on potential drug candidates and their mechanisms of action.

METHODS

A comprehensive literature search was conducted using various authentic scientific databases to identify studies published in the last decade that investigated potential treatment strategies for FRDA. The search terms used included "Friedreich's ataxia", "treatment", "drug candidates", and "mechanisms of action".

RESULTS

To date, only one drug got approval from US-FDA in the year 2023; however, significant developments were achieved in FRDA-related research focusing on diverse therapeutic interventions that could potentially alleviate the symptoms of this disease. Several promising drug candidates have been identified for the treatment of FRDA, which target various aspects of frataxin deficiency and aim to restore frataxin levels, reduce oxidative stress, and improve mitochondrial function. Clinical trials have shown varying degrees of success, with some drugs demonstrating significant improvements in neurological function and quality of life in FRDA patients.

CONCLUSION

While there has been significant progress in the development of treatment strategies for FRDA, further research is needed to optimize these approaches and identify the most effective and safe treatment options for patients. The integration of multiple therapeutic strategies may be necessary to achieve the best outcomes in FRDA management.

Friedreich ataxia: clinical features and new developments

Friedreich's ataxia (FRDA), a neurodegenerative disease characterized by ataxia and other neurological features, affects 1 in 50,000-100,000 individuals in the USA. However, FRDA also includes cardiac, orthopedic and endocrine dysfunction, giving rise to many secondary disease characteristics. The multifaceted approach for clinical care has necessitated the development of disease-specific clinical care guidelines. New developments in FRDA include the advancement of clinical drug trials targeting the NRF2 pathway and frataxin restoration. Additionally, a novel understanding of gene silencing in FRDA, reflecting a variegated silencing pattern, will have applications to current and future therapeutic interventions. Finally, new perspectives on the neuroanatomy of FRDA and its developmental features will refine the time course and anatomical targeting of novel approaches.

Drug Repositioning in Friedreich Ataxia

Friedreich ataxia is a rare neurodegenerative disorder caused by insufficient levels of the essential mitochondrial protein frataxin. It is a severely debilitating disease that significantly impacts the quality of life of affected patients and reduces their life expectancy, however, an adequate cure is not yet available for patients. Frataxin function, although not thoroughly elucidated, is associated with assembly of iron-sulfur cluster and iron metabolism, therefore insufficient frataxin levels lead to reduced activity of many mitochondrial enzymes involved in the electron transport chain, impaired mitochondrial metabolism, reduced ATP production and inefficient anti-oxidant response. As a consequence, neurons progressively die and patients progressively lose their ability to coordinate movement and perform daily activities. Therapeutic strategies aim at restoring sufficient frataxin levels or at correcting some of the downstream consequences of frataxin deficiency. However, the classical pathways of drug discovery are challenging, require a significant amount of resources and time to reach the final approval, and present a high failure rate. Drug repositioning represents a viable alternative to boost the identification of a therapy, particularly for rare diseases where resources are often limited. In this review we will describe recent efforts aimed at the identification of a therapy for Friedreich ataxia through drug repositioning, and discuss the limitation of such strategies.

Emerging therapies in Friedreich's Ataxia

INTRODUCTION

Friedreich's ataxia (FRDA) is a progressive, neurodegenerative disease that results in gait and limb ataxia, diabetes, cardiac hypertrophy, and scoliosis. At the cellular level, FRDA results in the deficiency of frataxin, a mitochondrial protein that plays a vital role in iron homeostasis and amelioration of oxidative stress. No cure currently exists for FRDA, but exciting therapeutic developments which target different parts of the pathological cascade are on the horizon.

AREAS COVERED

Areas covered include past and emerging therapies for FRDA, including antioxidants and mitochondrial-related agents, nuclear factor erythroid-derived 2-related factor 2 (Nrf2) activators, deuterated polyunsaturated fatty acids, iron chelators, histone deacetylase (HDAC) inhibitors, trans-activator of transcription (TAT)-frataxin, interferon gamma (IFNγ), erythropoietin, resveratrol, gene therapy, and anti-sense oligonucleotides (ASOs), among others.

EXPERT OPINION

While drug discovery has been challenging, new and exciting prospective treatments for FRDA are currently on the horizon, including pharmaceutical agents and gene therapy. Agents that enhance mitochondrial function, such as Nrf2 activators, dPUFAs and catalytic antioxidants, as well as novel methods of frataxin augmentation and genetic modulation will hopefully provide treatment for this devastating disease.

New developments in pharmacotherapy for Friedreich ataxia

Introduction: Friedreich ataxia (FRDA), a rare disease caused by the deficiency of the mitochondrial matrix protein frataxin, affects roughly 1 in 50,000 individuals worldwide. Current and emerging therapies focus on reversing the deleterious effects of such deficiency including mitochondrial augmentation and increasing frataxin levels, providing the possibility of treatment options for this physiologically complex, multisystem disorder. Areas covered: In this review article, the authors discuss the current and prior in vivo and in vitro research studies related to the treatment of FRDA, with a particular interest in future implications of each therapy. Expert opinion: Since the discovery of FXN in 1996, multiple clinical trials have occurred or are currently occurring; at a rapid pace for a rare disease. These trials have been directed at the augmentation of mitochondrial function and/or alleviation of symptoms and are not regarded as potential cures in FRDA. Either a combination of therapies or a drug that replaces or increases the pathologically low levels of frataxin better represent potential cures in FRDA.

Erythropoietin and Friedreich Ataxia: Time for a Reappraisal?

Friedreich ataxia (FRDA) is a rare neurological disorder due to deficiency of the mitochondrial protein frataxin. Frataxin deficiency results in impaired mitochondrial function and iron deposition in affected tissues. Erythropoietin (EPO) is a cytokine which was mostly known as a key regulator of erythropoiesis until cumulative evidence showed additional neurotrophic and neuroprotective properties. These features offered the rationale for advancement of EPO in clinical trials in different neurological disorders in the past years, including FRDA. Several mechanisms of action of EPO may be beneficial in FRDA. First of all, EPO exposure results in frataxin upregulation in vitro and in vivo. By promoting erythropoiesis, EPO influences iron metabolism and induces shifts in iron pool which may ameliorate conditions of free iron excess and iron accumulation. Furthermore, EPO signaling is crucial for mitochondrial gene activation and mitochondrial biogenesis. Up to date nine clinical trials investigated the effects of EPO and derivatives in FRDA. The majority of these studies had a proof-of-concept design. Considering the natural history of FRDA, all of them were too short in duration and not powered for clinical changes. However, these studies addressed significant issues in the treatment with EPO, such as (1) the challenge of the dose finding, (2) stability of frataxin up-regulation, (3) continuous versus intermittent stimulation with EPO/regimen, or (4) tissue changes after EPO exposure in humans in vivo (muscle biopsy, brain imaging). Despite several clinical trials in the past, no treatment is available for the treatment of FRDA. Current lines of research focus on gene therapy, frataxin replacement strategies and on regulation of key metabolic checkpoints such as NrF2. Due to potential crosstalk with all these mechanisms, interventions on the EPO pathway still represent a valuable research field. The recent development of small EPO mimetics which maintain cytoprotective properties without erythropoietic action may open a new era in EPO research for the treatment of FRDA.

Safety, pharmacodynamics, and potential benefit of omaveloxolone in Friedreich ataxia

Objective

Previous studies have demonstrated that suppression of Nrf2 in Friedreich ataxia tissues contributes to excess oxidative stress, mitochondrial dysfunction, and reduced ATP production. Omaveloxolone, an Nrf2 activator and NF-kB suppressor, targets dysfunctional inflammatory, metabolic, and bioenergetic pathways. The dose-ranging portion of this Phase 2 study assessed the safety, pharmacodynamics, and potential benefit of omaveloxolone in Friedreich ataxia patients (NCT02255435).

Methods

Sixty-nine Friedreich ataxia patients were randomized 3:1 to either omaveloxolone or placebo administered once daily for 12 weeks. Patients were randomized in cohorts of eight patients, at dose levels of 2.5-300 mg/day.

Results

Omaveloxolone was well tolerated, and adverse events were generally mild. Optimal pharmacodynamic changes (noted by changes in ferritin and GGT) were observed at doses of 80 and 160 mg/day. No significant changes were observed in the primary outcome, peak work load in maximal exercise testing (0.9 ± 2.9 W, placebo corrected). At the 160 mg/day dose, omaveloxolone improved the secondary outcome of the mFARS by 3.8 points versus baseline (P = 0.0001) and by 2.3 points versus placebo (P = 0.06). Omaveloxolone produced greater improvements in mFARS in patients that did not have musculoskeletal foot deformity (pes cavus). In patients without this foot deformity, omaveloxolone improved mFARS by 6.0 points from baseline (P < 0.0001) and by 4.4 points versus placebo (P = 0.01) at the 160 mg/day.

Interpretation

Treatment of Friedreich ataxia patients with omaveloxolone at the optimal dose level of 160 mg/day appears to improve neurological function. Therefore, omaveloxolone treatment is being examined in greater detail at 150 mg/day for Friedreich ataxia.

Progress in the treatment of Friedreich ataxia

Friedreich ataxia (FRDA) is a progressive neurological disorder affecting approximately 1 in 29,000 individuals of European descent. At present, there is no approved pharmacological treatment for this condition however research into treatment of FRDA has advanced considerably over the last two decades since the genetic cause was identified. Current proposed treatment strategies include decreasing oxidative stress, increasing cellular frataxin, improving mitochondrial function as well as modulating frataxin controlled metabolic pathways. Genetic and cell based therapies also hold great promise. Finally, physical therapies are being explored as a means of maximising function in those affected by FRDA.

Erythropoietin and small molecule agonists of the tissue-protective erythropoietin receptor increase FXN expression in neuronal cells in vitro and in Fxn-deficient KIKO mice in vivo

Friedreich's ataxia (FA) is a progressive neurodegenerative disease caused by reduced levels of the mitochondrial protein frataxin (FXN). Recombinant human erythropoietin (rhEPO) increased FXN protein in vitro and in early clinical studies, while no published reports evaluate rhEPO in animal models of FA. STS-E412 and STS-E424 are novel small molecule agonists of the tissue-protective, but not the erythropoietic EPO receptor. We find that rhEPO, STS-E412 and STS-E424 increase FXN expression in vitro and in vivo. RhEPO, STS-E412 and STS-E424 increase FXN by up to 2-fold in primary human cortical cells and in retinoic-acid differentiated murine P19 cells. In primary human cortical cells, the increase in FXN protein was accompanied by an increase in FXN mRNA, detectable within 4 h. RhEPO and low nanomolar concentrations of STS-E412 and STS-E424 also increase FXN in normal and FA patient-derived PBMC by 20%-40% within 24 h, an effect that was comparable to that by HDAC inhibitor 4b. In vivo, STS-E412 increased Fxn mRNA and protein in wild-type C57BL6/j mice. RhEPO, STS-E412, and STS-E424 increase FXN expression in the heart of FXN-deficient KIKO mice. In contrast, FXN expression in the brains of KIKO mice increased following treatment with STS-E412 and STS-E424, but not following treatment with rhEPO. Unexpectedly, rhEPO-treated KIKO mice developed severe splenomegaly, while no splenomegaly was observed in STS-E412- or STS-E424-treated mice. RhEPO, STS-E412 and STS-E424 upregulate FXN expression in vitro at equal efficacy, however, the effects of the small molecules on FXN expression in the CNS are superior to rhEPO in vivo.

Pharmacological therapeutics in Friedreich ataxia: the present state

INTRODUCTION

Friedreich ataxia (FRDA) is a progressive, inherited, neurodegenerative disease for which there is currently no cure or approved treatment. FRDA is caused by deficits in the production and expression of frataxin, a protein found in the mitochondria that is most likely responsible for regulating iron-sulfur cluster enzymes within the cell. A decrease in frataxin causes dysfunction of adenosine triphosphate synthesis, accumulation of mitochondrial iron, and other events leading to downstream cellular dysfunction. Areas covered: Therapeutic development for FRDA currently focuses on improving mitochondrial function and finding ways to increase frataxin expression. Additionally, the authors will review potential approaches aimed at iron modulation and genetic modulation. Finally, gene therapy is progressing rapidly and is being explored as a treatment for FRDA. Expert commentary: The collection of multiple therapeutic approaches provides many possible ways to treat FRDA. Although the mitochondrial approaches are not thought to be curative, as the primary frataxin deficit will remain, they may still produce improvements in quality of life and slowing of progression. Therapies aimed at frataxin restoration are more likely to truly modify the disease, with gene therapy as the best possibility to alter the course of the disease from both a cardiac and neurological perspective.

Stability of erythropoietin repackaging in polypropylene syringes for clinical use

Introduction: Epoetin alfa (Eprex®) is a subcutaneous, injectable formulation of short half-life recombinant human erythropoietin (rHuEPO). To current knowledge there are no published studies regarding the stability of rHuEPO once repackaging occurs (r-EPO) for clinical trial purposes. Materials and methods: We assessed EPO concentration in Eprex® and r-EPO syringes at 0, 60, 90, and 120 days after repackaging in polypropylene syringes. R-EPO was administered to 56 patients taking part in a clinical trial in Friedreich Ataxia. Serum EPO levels were measured at baseline and 48 h after r-EPO administration. Results: No differences were found between r-EPO and Eprex® syringes, but both globally decreased in total EPO content during storage at 4 °C. Patients receiving r-EPO had similar levels in EPO content as expected from previous trials in Friedreich Ataxia and from pharmacokinetics studies in healthy volunteers. Discussion: We demonstrate that repackaging of EPO does not alter its concentration if compared to the original product (Eprex®). This is true both for repackaging procedures and for the stability in polypropylene tubes. The expiration date of r-EPO can be extended from 1 to 4 months after repackaging, in accordance with pharmacopeia rules.

Milestones in Friedreich ataxia: more than a century and still learning

Friedreich ataxia (FRDA) is the most common autosomal recessive ataxia worldwide. This review highlights the main clinical features, pathophysiological mechanisms, and therapeutic approaches for FRDA patients. The disease is characterized by a combination of neurological involvement (ataxia and neuropathy), cardiomyopathy, skeletal abnormalities, and glucose metabolism disturbances. FRDA is caused by expanded guanine-adenine-adenine (GAA) triplet repeats in the first intron of the frataxin gene (FXN), resulting in reduction of messenger RNA and protein levels of frataxin in different tissues. The molecular and metabolic disturbances, including iron accumulation, lead to pathological changes characterized by spinal cord and dorsal root ganglia atrophy, dentate nucleus atrophy without global cerebellar volume reduction, and hypertrophic cardiomyopathy. DNA analysis is the hallmark for the diagnosis of FRDA. There is no specific treatment to stop the disease progression in FRDA patients. However, a number of drugs are under investigation. Therapeutic approaches intend to improve mitochondrial functioning and to increase FXN expression.

Consensus clinical management guidelines for Friedreich ataxia

Friedreich ataxia (FRDA), a multisystem autosomal recessive condition, is the most common inherited ataxia in Caucasians, affecting approximately 1 in 29,000 individuals. The hallmark clinical features of FRDA include progressive afferent and cerebellar ataxia, dysarthria, impaired vibration sense and proprioception, absent tendon reflexes in lower limbs, pyramidal weakness, scoliosis, foot deformity and cardiomyopathy. Despite significant progress in the search for disease modifying agents, the chronic progressive nature of FRDA continues to have a profound impact on the health and well-being of people with FRDA. At present there is no proven treatment that can slow the progression or eventual outcome of this life-shortening condition. Thirty-nine expert clinicians located in Europe, Australia, Canada and USA critically appraised the published evidence related to FRDA clinical care and provided this evidence in a concise manner. Where no published data specific to FRDA existed, recommendations were based on data related to similar conditions and/or expert consensus. There were 146 recommendations developed to ensure best practice in the delivery of health services to people with FRDA. Sixty-two percent of recommendations are based on expert opinion or good practice indicating the paucity of high-level quality clinical studies in this area. Whilst the development of these guidelines provides a critical first step in the provision of appropriate clinical care for people with FRDA, it also highlights the urgency of undertaking high-quality clinical studies that will ensure the delivery of optimum clinical management and intervention for people with FRDA.

Treatment for speech disorder in Friedreich ataxia and other hereditary ataxia syndromes

BACKGROUND

Hereditary ataxia syndromes can result in significant speech impairment, a symptom thought to be responsive to treatment. The type of speech impairment most commonly reported in hereditary ataxias is dysarthria. Dysarthria is a collective term referring to a group of movement disorders affecting the muscular control of speech. Dysarthria affects the ability of individuals to communicate and to participate in society. This in turn reduces quality of life. Given the harmful impact of speech disorder on a person's functioning, treatment of speech impairment in these conditions is important and evidence-based interventions are needed.

OBJECTIVES

To assess the effects of interventions for speech disorder in adults and children with Friedreich ataxia and other hereditary ataxias.

SEARCH METHODS

On 14 October 2013, we searched the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL, MEDLINE, EMBASE, CINAHL Plus, PsycINFO, Education Resources Information Center (ERIC), Linguistics and Language Behavior Abstracts (LLBA), Dissertation Abstracts and trials registries. We checked all references in the identified trials to identify any additional published data.

SELECTION CRITERIA

We considered for inclusion randomised controlled trials (RCTs) or quasi-RCTs that compared treatments for hereditary ataxias with no treatment, placebo or another treatment or combination of treatments, where investigators measured speech production.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials for inclusion, extracted data and assessed the risk of bias of included studies using the standard methodological procedures expected by The Cochrane Collaboration. The review authors collected information on adverse effects from included studies. We did not conduct a meta-analysis as no two studies utilised the same assessment procedures within the same treatment.

MAIN RESULTS

Fourteen clinical trials, involving 721 participants, met the criteria for inclusion in the review. Thirteen studies compared a pharmaceutical treatment with placebo (or a low dose of the intervention), in heterogenous groups of degenerative cerebellar ataxias. Three compounds were studied in two trials each: a levorotatory form of 5-hydroxytryptophan (L-5HT), idebenone and thyrotropin-releasing hormone tartrate (TRH-T); each of the other compounds (riluzole, varenicline, buspirone, betamethasone, coenzyme Q10 with vitamin E, α-tocopheryl quinone and erythropoietin) were studied in one trial. The 14th trial, involving a mixed group of participants with spinocerebellar ataxia, compared the effectiveness of nonspecific physiotherapy and occupational therapy within an inpatient hospital setting to no treatment. No studies utilised traditional speech therapies. We defined the primary outcome measure in this review as the percentage change (improvement) in overall speech production immediately following completion of the intervention or later, measured by any validated speech assessment tool. None of the trials included speech as a primary outcome or examined speech using any validated speech assessment tool. Eleven studies reported speech outcomes derived from a subscale embedded within disease rating scales. The remaining three studies used alternative assessments to measure speech, including mean time to produce a standard sentence, a subjective rating of speech on a 14-point analogue scale, patient-reported assessment of the impact of dysarthria on activities of daily living and acoustic measures of syllable length. One study measured speech both subjectively as part of a disease rating scale and with further measures of speech timing. Three studies utilised the Short Form-36 Health Survey (SF-36) and one used the Child Health Questionnaire as measures of general quality of life. A further study utilised the Functional Independence Measure to assess functional health.Five studies reported statistically significant improvement on an overall disease rating scale in which a speech subscale was included. Only three of those studies provided specific data on speech performance; all were comparisons with placebo. Improvements in overall disease severity were observed with α-tocopheryl quinone; however, no significant changes were found on the speech subscale in a group of individuals with Friedreich ataxia. A statistically significant improvement in speech according to a speech disorders subscale was observed with betamethasone. Riluzole was found to have a statistically significant effect on speech in a group of participants with mixed hereditary, sporadic and unknown origin ataxias. No significant differences were observed between treatment and placebo in any other pharmaceutical study. A statistically significant improvement in functional independence occurred at the end of the treatment period in the rehabilitation study compared to the delayed treatment group but these effects were not present 12 to 24 weeks after treatment. Of the four studies that assessed quality of life, none found a significant effect. A variety of minor adverse events were reported for the 13 pharmaceutical therapies, including gastrointestinal side effects and nausea. Serious adverse effects were reported in two participants in one of the L-5HT trials (participants discontinued due to gastrointestinal effects), and in four participants (three taking idebenone, one taking placebo) in the idebenone studies. Serious adverse events with idebenone were gastrointestinal side effects and, in people with a previous history of these events, chest pain and idiopathic thrombocytopenic purpura. The rehabilitation study did not report any adverse events.We considered six studies to be at high risk of bias in some respect. We suspected inadequate blinding of participants or assessors in four studies and poor randomisation in a further two studies. There was a high risk of reporting bias in two studies and attrition bias in four studies. Only one study had a low risk of bias across all criteria. Taken together with other limitations of the studies relating to the validity of the measurement scales used, we downgraded the quality of the evidence for many of the outcomes to low or very low.

AUTHORS' CONCLUSIONS

There is insufficient and low or very low quality evidence from either RCTs or observational studies to determine the effectiveness of any treatment for speech disorder in any of the hereditary ataxia syndromes.

Consensus paper: management of degenerative cerebellar disorders

Treatment of motor symptoms of degenerative cerebellar ataxia remains difficult. Yet there are recent developments that are likely to lead to significant improvements in the future. Most desirable would be a causative treatment of the underlying cerebellar disease. This is currently available only for a very small subset of cerebellar ataxias with known metabolic dysfunction. However, increasing knowledge of the pathophysiology of hereditary ataxia should lead to an increasing number of medically sensible drug trials. In this paper, data from recent drug trials in patients with recessive and dominant cerebellar ataxias will be summarized. There is consensus that up to date, no medication has been proven effective. Aminopyridines and acetazolamide are the only exception, which are beneficial in patients with episodic ataxia type 2. Aminopyridines are also effective in a subset of patients presenting with downbeat nystagmus. As such, all authors agreed that the mainstays of treatment of degenerative cerebellar ataxia are currently physiotherapy, occupational therapy, and speech therapy. For many years, well-controlled rehabilitation studies in patients with cerebellar ataxia were lacking. Data of recently published studies show that coordinative training improves motor function in both adult and juvenile patients with cerebellar degeneration. Given the well-known contribution of the cerebellum to motor learning, possible mechanisms underlying improvement will be outlined. There is consensus that evidence-based guidelines for the physiotherapy of degenerative cerebellar ataxia need to be developed. Future developments in physiotherapeutical interventions will be discussed including application of non-invasive brain stimulation.

A longitudinal VBM study monitoring treatment with erythropoietin in patients with Friedreich ataxia

Background

Recombinant human erythropoietin (rhuEPO) has received considerable attention because of its neuroprotective properties. It has recently been reported that rhuEPO increases frataxin levels in combination with clinical improvement in rhuEPO treated patients with Friedreich ataxia (FRDA).

Purpose

To determine possible therapy dependent intracranial volume changes after treatment with rhuEPO using voxel-based morphometry (VBM).

Material and Methods

Nine FRDA patients were scanned on the same 1.5-Tesla MRI scanner before and after treatment with rhuEPO. FRDA patients received 5000 IU rhuEPO thrice weekly subcutaneously for a time period of 8 weeks followed by 2000 IU thrice weekly over 6 months. To test for re-test reliability a control group of 12 healthy volunteers were scanned twice on the same scanner without rhuEPO treatment. Neurological state was defined by the Friedreich Ataxia Rating Scale (FARS) and the Scale for the Assessment and Rating of Ataxia (SARA). Statistical parametric mapping software was used for image processing and statistical analysis.

Results

When comparing follow-up scans after rhuEPO treatment with baseline scans (P <0.001 uncorrected) an increase of gray matter volume was observed bilaterally in the Pulvinar and the posterior parietal cortex. Moreover, clinical improvement detected using specific Ataxia scores correlated with VBM results in the pulvinar.

Conclusion

Given the limitation of a small sample size, our study confirms previous findings that MRI may serve as reliable biomarker in neurodegenerative diseases as well as in monitoring of microstructural changes representing disease progression and/or therapy effects.

Erythropoietin and the heart: physiological effects and the therapeutic perspective

Erythropoietin (Epo) has been thought to act exclusively on erythroid progenitor cells. The identification of Epo receptor (EpoR) in non-haematopoietic cells and tissues including neurons, astrocytes, microglia, immune cells, cancer cell lines, endothelial cells, bone marrow stromal cells, as well as cells of myocardium, reproductive system, gastrointestinal tract, kidney, pancreas and skeletal muscle indicates that Epo has pleiotropic actions. Epo shows signals through protein kinases, anti-apoptotic proteins and transcription factors. In light of interest of administering recombinant human erythropoietin (rhEpo) and its analogues for limiting infarct size and left ventricular (LV) remodelling after acute myocardial infarction (AMI) in humans, the foremost studies utilising rhEpo are reviewed. The putative mechanisms involved in Epo-induced cardioprotection are related to the antiapoptotic, anti-inflammatory and angiogenic effects of Epo. Thus, cardioprotective potentials of rhEpo are reviewed in this article by focusing on clinical applicability. An overview of non-haematopoietic Epo analogues, which are a reliable alternative to the classic EpoR agonists and may prevent undesired side effects, is also provided.

Clinical neurogenetics: friedreich ataxia

Friedreich ataxia is the most common autosomal recessive ataxia. It is a progressive neurodegenerative disorder, typically with onset before 20 years of age. Signs and symptoms include progressive ataxia, ascending weakness and ascending loss of vibration and joint position senses, pes cavus, scoliosis, cardiomyopathy, and arrhythmias. There are no disease-modifying medications to either slow or halt the progression of the disease, but research investigating therapies to increase endogenous frataxin production and decrease the downstream consequences of disrupted iron homeostasis is ongoing. Clinical trials of promising medications are underway, and the treatment era of Friedreich ataxia is beginning.

Iron depletion induced by bloodletting and followed by rhEPO administration as a therapeutic strategy in progressive multiple sclerosis: a pilot, open-label study with neurophysiological measurements

OBJECTIVES

To evaluate the concept that iron depletion (ID) induced by bloodletting and followed by recombinant human erythropoietin (rhEPO) administration could be a therapeutic strategy in progressive multiple sclerosis (PMS) and that it could be assessed by neurophysiological measurements.

PATIENTS AND METHODS

In four patients with PMS, bloodletting was performed until ID was induced, and then rhEPO was administered (300 UI/kg/week). The changes induced by the treatment were assessed by clinical scores, biological tests, and neurophysiological study of cortical excitability using transcranial magnetic stimulation techniques.

RESULTS

The treatment was well tolerated except for muscle cramps and one popliteal vein thrombosis in a patient confined to chair. ID was obtained within 28 weeks and was associated with endogenous production of EPO. No bloodletting was further required during a six-month period after introduction of rhEPO. At the end of the follow-up (up to one year), fatigue and walking capacities tended to improve in two patients. Neurophysiological changes were characterized by an increased cortical excitability, including a decrease of motor thresholds and an enhancement of intracortical facilitation and cerebellothalamocortical inhibition.

CONCLUSIONS

The combined ID-rhEPO therapy could authorize a prolonged administration of rhEPO in PMS patients, able to modify cortical excitability of the glutamatergic and gabaergic circuits. These preliminary data are encouraging to design a larger, controlled therapeutical trial to assess the value of such a strategy to improve functional symptoms in PMS patients, and maybe to prevent axonal degeneration. Neurophysiological measurements based on cortical excitability studies could provide sensitive parameters to evaluate treatment-induced changes in this context.

White matter changes in patients with friedreich ataxia after treatment with erythropoietin

BACKGROUND AND PURPOSE

Erythropoietin (EPO) has received growing attention because of its neuroregenerative properties. Preclinical and clinical evidence supports its therapeutic potential in brain conditions like stroke, multiple sclerosis, and schizophrenia. Also, in Friedreich ataxia, clinical improvement after EPO therapy was shown. The aim of this study was to assess possible therapy-associated brain white matter changes in these patients.

METHODS

Nine patients with Friedreich ataxia underwent Diffusion Tensor Imaging (DTI) before and after EPO treatment. Tract-based spatial statistics was used for longitudinal comparison.

RESULTS

We detected widespread longitudinal increase in fractional anisotropy and axial diffusivity (D||) in cerebral hemispheres bilaterally (P < .05, corrected), while no changes were observed within the cerebellum, medulla oblongata, and pons.

CONCLUSIONS

To the best of our knowledge, this is the first DTI study to investigate the effects of EPO in a neurodegenerative disease. Anatomically, the diffusivity changes appear disease unspecific, and their biological underpinnings deserve further study.

Erythropoietin in Friedreich ataxia

In Friedreich ataxia (FRDA), several candidate substances including erythropoietin (EPO) focus on increase in the amount of frataxin and aim to counteract the consequences of frataxin deficiency. Evidence for recombinant human erythropoietin (rHuEPO) in FRDA is based on in vitro studies using mouse neuronal cell lines, human fibroblasts, cardiomyocytes, and primary lymphocytes from FRDA patients or control subjects which showed a dose-dependent increase of frataxin after incubation with different erythropoietins. The mechanism by which EPO induces frataxin increase remains to be elucidated, but may involve post-transcriptional and/or post-translational modifications of frataxin or alterations in frataxin half-life and metabolism. In vivo data on rHuEPO's ability to increase frataxin in FRDA patients is contradictory as studies on the effect of EPO derivatives in FRDA differ in treatment regimen, sample size, and duration. Open-label studies indicate for sustained frataxin increase, decrease of oxidative stress, and clinical improvement in FRDA patients after administration of rHuEPO. Two randomized controlled studies found acceptable safety and tolerability of EPO derivatives in FRDA. Secondary outcome measures, however, such as frataxin up-regulation and clinical efficacy were not met. This review will focus on (i) pre-clinical work on erythropoietins in FRDA and (ii) clinical studies in FRDA patients exposed to erythropoietins.

Bioenergetics of the calf muscle in Friedreich ataxia patients measured by 31P-MRS before and after treatment with recombinant human erythropoietin

Friedreich ataxia (FRDA) is caused by a GAA repeat expansion in the FXN gene leading to reduced expression of the mitochondrial protein frataxin. Recombinant human erythropoietin (rhuEPO) is suggested to increase frataxin levels, alter mitochondrial function and improve clinical scores in FRDA patients. Aim of the present pilot study was to investigate mitochondrial metabolism of skeletal muscle tissue in FRDA patients and examine effects of rhuEPO administration by phosphorus 31 magnetic resonance spectroscopy (31P MRS). Seven genetically confirmed FRDA patients underwent 31P MRS of the calf muscles using a rest-exercise-recovery protocol before and after receiving 3000 IU of rhuEPO for eight weeks. FRDA patients showed more rapid phosphocreatine (PCr) depletion and increased accumulation of inorganic phosphate (Pi) during incremental exercise as compared to controls. After maximal exhaustive exercise prolonged regeneration of PCR and slowed decline in Pi can be seen in FRDA. PCr regeneration as hallmark of mitochondrial ATP production revealed correlation to activity of complex II/III of the respiratory chain and to demographic values. PCr and Pi kinetics were not influenced by rhuEPO administration. Our results confirm mitochondrial dysfunction and exercise intolerance due to impaired oxidative phosphorylation in skeletal muscle tissue of FRDA patients. MRS did not show improved mitochondrial bioenergetics after eight weeks of rhuEPO exposition in skeletal muscle tissue of FRDA patients.

Trial Registration

EU Clinical Trials Register2008-000040-13

Effects of acetyl-DL-leucine in patients with cerebellar ataxia: a case series

No existing medication has yet been shown to convincingly improve cerebellar ataxia. Therefore, the identification of new drugs for its symptomatic treatment is desirable. The objective of this case series was to evaluate the efficacy of treatment of cerebellar ataxia with the amino acid acetyl-DL-leucine (Tanganil). Thirteen patients (eight males, median age 51 years) with degenerative cerebellar ataxia of different etiologies (SCA1/2, ADCA, AOA, SAOA) were treated with acetyl-DL-leucine (5 g/day) without titration for 1 week. Motor function was evaluated by changes in the Scale for the Rating and Assessment of Ataxia (SARA) and in the Spinocerebellar Ataxia Functional Index (SCAFI) during treatment compared to a baseline examination. Quality of life (EuroQol-5D-3L) and side effects were also assessed. Mean total SARA decreased remarkably (p = 0.002) from a baseline of 16.1 ± 7.1 to 12.8 ± 6.8 (mean ± SD) on medication. There were also significant improvements in sub-scores for gait (p = 0.022), speech (p = 0.007), finger-chase (p = 0.042), nose-finger-test (p = 0.035), rapid-alternating-movements (p = 0.002) and heel-to-shin (p = 0.018). Furthermore, patients showed better performance in the SCAFI consisting of the 8-m-walking-time (8 MW, p = 0.003), 9-Hole-Peg-Test of the dominant hand (9HPTD, p = 0.011) and the PATA rate (p = 0.005). Quality of life increased during treatment (p = 0.003). No side effects were reported. In conclusion, acetyl-DL-leucine significantly improved ataxic symptoms without side effects and therefore showed a good risk-benefit profile. These findings need to be confirmed in placebo-controlled trials.

Development of frataxin gene expression measures for the evaluation of experimental treatments in Friedreich's ataxia

BACKGROUND

Friedreich ataxia is a progressive neurodegenerative disorder caused by GAA triplet repeat expansions or point mutations in the FXN gene and, ultimately, a deficiency in the levels of functional frataxin protein. Heterozygous carriers of the expansion express approximately 50% of normal frataxin levels yet manifest no clinical symptoms, suggesting that therapeutic approaches that increase frataxin may be effective even if frataxin is raised only to carrier levels. Small molecule HDAC inhibitor compounds increase frataxin mRNA and protein levels, and have beneficial effects in animal models of FRDA.

METHODOLOGY/PRINCIPAL FINDINGS

To gather data supporting the use of frataxin as a therapeutic biomarker of drug response we characterized the intra-individual stability of frataxin over time, determined the contribution of frataxin from different components of blood, compared frataxin measures in different cell compartments, and demonstrated that frataxin increases are achieved in peripheral blood mononuclear cells. Frataxin mRNA and protein levels were stable with repeated sampling over four and 15 weeks. In the 15-week study, the average CV was 15.6% for protein and 18% for mRNA. Highest levels of frataxin in blood were in erythrocytes. As erythrocytes are not useful for frataxin assessment in many clinical trial situations, we confirmed that PBMCs and buccal swabs have frataxin levels equivalent to those of whole blood. In addition, a dose-dependent increase in frataxin was observed when PBMCs isolated from patient blood were treated with HDACi. Finally, higher frataxin levels predicted less severe neurological dysfunction and were associated with slower rates of neurological change.

CONCLUSIONS/SIGNIFICANCE

Our data support the use of frataxin as a biomarker of drug effect. Frataxin levels are stable over time and as such a 1.5 to 2-fold change would be detectable over normal biological fluctuations. Additionally, our data support buccal cells or PBMCs as sources for measuring frataxin protein in therapeutic trials.

Radial diffusivity in the cerebellar peduncles correlates with clinical severity in Friedreich ataxia

Friedreich ataxia (FRDA) is a common inherited ataxia, caused by an expanded GAA repeat sequence in the Frataxin (FXN) gene. The proprioceptive system, which enters the cerebellum through the cerebellar peduncles, is a primary focus of pathology. In this study, we investigate the relationship of clinical and genetic data with diffusion-tensor imaging (DTI) indices reflecting white matter integrity of the cerebellar peduncles. Nine FRDA patients underwent DTI. After between-subject registration using tract-based spatial statistics, a white matter atlas was used for computing average values of DTI indices in the regions of interest. These were the inferior, middle and superior cerebellar peduncles (ICP, MCP, SCP). For Bonferroni correction, significance threshold was set to p < 0.0056. We found that radial diffusivity (D(⊥)) within the ICP significantly correlated with scores on the Friedreich Ataxia Rating Scale (FARS, Spearman's ρ = 0.883, p = 0.0016, all two-sided) and, at trend level, with number of trinucleotide repeats (ρ = 0.812, p = 0.008). D(⊥) in the SCP correlated with scores on the Scale for the Assessment and Rating of Ataxia (SARA, ρ = 0.867, p = 0.0025). These findings support the role of DTI, and especially D(⊥), as an informative biomarker in FRDA.

Pharmacological screening using an FXN-EGFP cellular genomic reporter assay for the therapy of Friedreich ataxia

Friedreich ataxia (FRDA) is an autosomal recessive disorder characterized by neurodegeneration and cardiomyopathy. The presence of a GAA trinucleotide repeat expansion in the first intron of the FXN gene results in the inhibition of gene expression and an insufficiency of the mitochondrial protein frataxin. There is a correlation between expansion length, the amount of residual frataxin and the severity of disease. As the coding sequence is unaltered, pharmacological up-regulation of FXN expression may restore frataxin to therapeutic levels. To facilitate screening of compounds that modulate FXN expression in a physiologically relevant manner, we established a cellular genomic reporter assay consisting of a stable human cell line containing an FXN-EGFP fusion construct, in which the EGFP gene is fused in-frame with the entire normal human FXN gene present on a BAC clone. The cell line was used to establish a fluorometric cellular assay for use in high throughput screening (HTS) procedures. A small chemical library containing FDA-approved compounds and natural extracts was screened and analyzed. Compound hits identified by HTS were further evaluated by flow cytometry in the cellular genomic reporter assay. The effects on FXN mRNA and frataxin protein levels were measured in lymphoblast and fibroblast cell lines derived from individuals with FRDA and in a humanized GAA repeat expansion mouse model of FRDA. Compounds that were established to increase FXN gene expression and frataxin levels included several anti-cancer agents, the iron-chelator deferiprone and the phytoalexin resveratrol.

Recent advances in the genetics of cerebellar ataxias

The hereditary cerebellar ataxias are a clinically and genetically heterogeneous group of disorders that primarily affect the cerebellum; often there are additional features such as neuropathy, cognitive decline, or maculopathy that help define the clinical subtype of ataxia. They are commonly classified according to their mode of inheritance into autosomal dominant, autosomal recessive, X-linked, and mitochondrial forms. Great advances have been made in understanding the genetics of cerebellar ataxias in the last 15 years. At least 36 different forms of ADCA are known, 20 autosomal-recessive, two X-linked, and several forms of ataxia associated with mitochondrial defects are known to date. However, in about 40 % of suspected genetically determined ataxia cases, the underlying genetic defect remains undetermined. Although the majority of disease genes have been found in the last two decades, over the last 2 years the genetics has undergone a methodological revolution. New DNA sequencing technologies are enabling us to investigate the whole or large targeted proportions of the genome in a rapid, affordable, and comprehensive way. Exome and targeted sequencing has recently identified four new genes causing ataxia: TGM6, ANO10, SYT14, and rundataxin. This approach is likely to continue to discover new ataxia genes and make screening of existing genes more effective. Translating the genetic findings into isolated and overlapping disease pathways will help stratify patient groups and identify therapeutic targets for ataxia that have so far remained undiscovered.

Friedreich ataxia clinical outcome measures: natural history evaluation in 410 participants

Friedreich ataxia is an autosomal recessive neurodegenerative disorder characterized by ataxia, dysarthria, and areflexia. The authors report the progress of a large international noninterventional cohort (n = 410), tracking the natural history of disease progression using the neurologic examination-based Friedreich Ataxia Rating Scale. The authors analyzed the rate of progression with cross-sectional analysis and longitudinal analysis over a 2-year period. The Friedreich Ataxia Rating Scale captured disease progression when used at 1 and 2 years following initial evaluation, with a lower ratio of standard deviation of change to mean change over 2 years of evaluation. However, modeling of disease progression identified substantial ceiling effects in the Friedreich Ataxia Rating Scale, suggesting this measure is most useful in subjects before maximal deficit is approached.

Therapeutic developments in Friedreich ataxia

Friedreich ataxia is an inherited, severe, progressive neuro- and cardiodegenerative disorder for which there currently is no approved therapy. Friedreich ataxia is caused by the decreased expression and/or function of frataxin, a mitochondrial matrix protein that binds iron and is involved in the formation of iron-sulfur clusters. Decreased frataxin function leads to decreased iron-sulfur cluster formation, mitochondrial iron accumulation, cytosolic iron depletion, oxidative stress, and mitochondrial dysfunction. Cloning of the disease gene for Friedreich ataxia and elucidation of many aspects of the biochemical defects underlying the disorder have led to several major therapeutic initiatives aimed at increasing frataxin expression, reversing mitochondrial iron accumulation, and alleviating oxidative stress. These initiatives are in preclinical and clinical development and are reviewed herein.

A review of Friedreich ataxia clinical trial results

There are now 21 agents or classes of therapeutic agents in the Friedreich ataxia research pipeline (http://www.curefa.org/pipeline.html) that have been developed in the 15 years since the discovery of the frataxin gene, with the ongoing characterization of its mutations and the resulting molecular pathology. Twenty-four studies are currently posted on ClinicalTrials.gov. Twenty-seven works discussing the results of clinical trials in Friedreich ataxia have been published. In 2010, 42 public (National Institutes of Health) and private (Friedreich Ataxia Research Alliance, Muscular Dystrophy Association, and National Ataxia Foundation) grants were funded for translational and clinical research in Friedreich ataxia. Millions of dollars from public, private, and industry-based initiatives have been dedicated to research in Friedreich ataxia therapeutics. Despite this vigorous international effort, there is as yet no proven disease-modifying therapy for Friedreich ataxia.

Unanswered questions in Friedreich ataxia

During the past 15 years, the pace of research advancement in Friedreich ataxia has been rapid. The abnormal gene has been discovered and its gene product characterized, leading to the development of new evidence-based therapies. Still, various unsettled issues remain that affect clinical trials. These include the level of frataxin deficiency needed to cause disease, the mechanism by which frataxin-deficient mitochondrial dysfunction leads to symptomatology, and the reason selected cells are most affected in Friedreich ataxia. In this review, we summarize these questions and propose testable hypotheses for their resolution.

miR-886-3p levels are elevated in Friedreich ataxia

Friedreich ataxia (FRDA) is the most common inherited ataxia caused primarily by an intronic GAA.TTC triplet repeat expansion in the frataxin (FXN) gene. FXN RNA and protein levels are reduced in patients leading to progressive gait and limb ataxia, sensory loss, reduced tendon reflexes, dysarthria, absent lower limb reflexes, and loss of position and vibration sense. Neurological manifestations ensue from primary loss of dorsal root ganglia neurons and their associated axons ascending centrally in the spinal cord and peripherally in large myelinated nerves. Small noncoding RNAs such as microRNAs have been shown to be dysregulated in neurodegenerative diseases such as Alzheimer's and Huntington's disease. Here we report that hsa-miR-886-3p (miR-886-3p) was increased in patient cells as well as peripheral patient blood samples. Selective reduction in miR-886-3p by an anti-miR led to elevation of FXN message and protein levels without associated changes in histone marks at the FXN locus. Nevertheless, derepression of frataxin by a histone deacetylase inhibitor leads to a decrease in miR-886-3p. These results outline involvement of a small RNA, miR-886-3p in FRDA and a novel therapeutic approach to this disease using an anti-miR-886-3p.

Erythropoietin in Friedreich ataxia: no effect on frataxin in a randomized controlled trial

BACKGROUND

Friedreich ataxia is a rare disease caused by GAA-trinucleotide-repeat expansions in the frataxin gene, leading to marked reduction of qualitatively normal frataxin protein. Recently, human recombinant erythropoietin was reported to increase frataxin levels in patients with Friedreich ataxia.

METHODS

We performed a 6-month, randomized placebo-controlled, double-blind, dose-response pilot trial to assess the safety and efficacy of erythropoietin in increasing frataxin levels. Sixteen adult patient with Friedreich ataxia were randomly assigned to erythropoietin (n = 11) or matching placebo (n = 5). All patients continued Idebenone treatment (5 mg/kg/day). Treatment consisted of a 6-month scaling-up phase, in which erythropoietin was administered intravenously at the following doses: 20,000 IU every 3 weeks, 40,000 IU every 3 weeks, and 40,000 IU every 2 weeks.

RESULTS

Erythropoietin treatment was safe and well tolerated, but did not result in any significant hematological, clinical, or biochemical effects in Friedreich ataxia patients.

Effects of erythropoietin on frataxin levels and mitochondrial function in Friedreich ataxia--a dose-response trial

Friedreich ataxia (FRDA) is an autosomal recessive inherited neurodegenerative disorder leading to reduced expression of the mitochondrial protein frataxin. Previous studies showed frataxin upregulation in FRDA following treatment with recombinant human erythropoietin (rhuEPO). Dose-response interactions between frataxin and rhuEPO have not been studied until to date. We administered escalating rhuEPO single doses (5,000, 10,000 and 30,000 IU) in monthly intervals to five adult FRDA patients. Measurements of frataxin, serum erythropoietin levels, iron metabolism and mitochondrial function were carried out. Clinical outcome was assessed using the "Scale for the assessment and rating of ataxia". We found maximal erythropoietin serum concentrations 24 h after rhuEPO application which is comparable to healthy subjects. Frataxin levels increased significantly over 3 months, while ataxia rating did not reveal clinical improvement. All FRDA patients had considerable ferritin decrease. NADH/NAD ratio, an indicator of mitochondrial function, increased following rhuEPO treatment. In addition to frataxin upregulation in response to continuous low-dose rhuEPO application shown in previous studies, our results indicate for a long-lasting frataxin increase after single high-dose rhuEPO administration. To detect frataxin-derived neuroprotective effects resulting in clinically relevant improvement, well-designed studies with extended time frame are required.

Correlation of frataxin content in blood and skeletal muscle endorses frataxin as a biomarker in Friedreich ataxia

BACKGROUND

Friedreich ataxia is an autosomal recessive disorder caused by mutations in the frataxin gene, leading to reduced levels of the mitochondrial protein frataxin. Assays to quantitatively measure frataxin in peripheral blood have been established. To determine the validity of frataxin as a biomarker for clinical trials, we assessed frataxin in clinically affected tissue.

METHODS

In 7 patients with Friedreich ataxia, frataxin content was measured in blood and skeletal muscle before and after treatment with recombinant human erythropoietin, applying the electrochemiluminescence immunoassay.

RESULTS

We found frataxin content to be correlated in peripheral blood mononuclear cells and skeletal muscle in drug-naive patients with Friedreich ataxia. The correlation of frataxin content in both compartments remained significant after 8 weeks of treatment. Skeletal-muscle frataxin values correlated with ataxia using the Scale for the Assessment and Rating of Ataxia score.

CONCLUSIONS

Our results endorse frataxin measurements in peripheral blood cells as a valid biomarker in Friedreich ataxia.

Friedreich's ataxia: past, present and future

Friedreich's ataxia (FRDA) is an autosomal recessive inherited disorder characterized by progressive gait and limb ataxia, dysarthria, areflexia, loss of vibratory and position sense, and a progressive motor weakness of central origin. Additional features include hypertrophic cardiomyopathy and diabetes. Large GAA repeat expansions in the first intron of the FXN gene are the most common mutation underlying FRDA. Patients show severely reduced levels of a FXN-encoded mitochondrial protein called frataxin. Frataxin deficiency is associated with abnormalities of iron metabolism: decreased iron-sulfur cluster (ISC) biogenesis, accumulation of iron in mitochondria and depletion in the cytosol, enhanced cellular iron uptake. Some models have also shown reduced heme synthesis. Evidence for oxidative stress has been reported. Respiratory chain dysfunction aggravates oxidative stress by increasing leakage of electrons and the formation of superoxide. In vitro studies have demonstrated that Frataxin deficient cells not only generate more free radicals, but also show a reduced capacity to mobilize antioxidant defenses. The search for experimental drugs increasing the amount of frataxin is a very active and timely area of investigation. In cellular and in animal model systems, the replacement of frataxin function seems to alleviate the symptoms or even completely reverse the phenotype. Therefore, drugs increasing the amount of frataxin are attractive candidates for novel therapies. This review will discuss recent findings on FRDA pathogenesis, frataxin function, new treatments, as well as recent animal and cellular models. Controversial aspects are also discussed.

Combined therapy with idebenone and deferiprone in patients with Friedreich's ataxia

Iron chelators are a new therapeutical approach for patients with Friedreich's ataxia, on the basis that oxidative cell damage that occurs in these patients is due to the increasing deposits of mitochondrial iron pools. The objective of the study was to evaluate the effects of the combined therapy of idebenone and low oral doses of deferiprone on the neurological signs and cardiac function parameters. This study was designed as a prospective open-label single-arm study. Twenty Friedreich's ataxia patients were treated with idebenone (20 mg/kg/day) and deferiprone (20 mg/kg/day) for 11 months. Patients were evaluated before the start and throughout the study with the International Cooperative Ataxia Rating Scale (ICARS) scores, echocardiographic measurements and MRI (magnetic resonance imaging) techniques to asses brain iron deposits in the dentate nucleus. No significant differences were observed in total ICARS scores when comparing baseline status and the end of the study in the whole group of patients. Posture and gait scores increased significantly after 11 months of therapy (Wilcoxon's test, p = 0.04) and kinetic function improved significantly (Wilcoxon's test, p = 0.015). Echocardiography data showed a significant reduction of the interventricular septum thickness (Wilcoxon's test, p = 0.04) and in the left ventricular mass index (Wilcoxon's test, p = 0.038) after the start of the therapy. The MRI values in the dentate nucleus showed a statistically significant reduction (Wilcoxon's test p = 0.007) between baseline conditions and after 11 months of the therapy. Combined therapy with idebenone and deferiprone in patients with FDRA indicates a stabilizing effect in neurologic dysfunctions due to an improvement in the kinetic functions, with a worsening of gait and posture scores. Heart hypertrophy parameters and iron deposits in dentate nucleus improved significantly. Combined therapy was well tolerated with mild side effects, apart from the risk of neutropenia and progressive reduction of plasma iron parameters.

Blood cells from Friedreich ataxia patients harbor frataxin deficiency without a loss of mitochondrial function

Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by GAA triplet expansions or point mutations in the FXN gene on chromosome 9q13. The gene product called frataxin, a mitochondrial protein that is severely reduced in FRDA patients, leads to mitochondrial iron accumulation, Fe-S cluster deficiency and oxidative damage. The tissue specificity of this mitochondrial disease is complex and poorly understood. While frataxin is ubiquitously expressed, the cellular phenotype is most severe in neurons and cardiomyocytes. Here, we conducted comprehensive proteomic, metabolic and functional studies to determine whether subclinical abnormalities exist in mitochondria of blood cells from FRDA patients. Frataxin protein levels were significantly decreased in platelets and peripheral blood mononuclear cells from FRDA patients. Furthermore, the most significant differences associated with frataxin deficiency in FRDA blood cell mitochondria were the decrease of two mitochondrial heat shock proteins. We did not observe profound changes in frataxin-targeted mitochondrial proteins or mitochondrial functions or an increase of apoptosis in peripheral blood cells, suggesting that functional defects in these mitochondria are not readily apparent under resting conditions in these cells.