Treatment of Friedreich's ataxia

Efficacy and Safety of Leriglitazone in Patients With Friedreich Ataxia

Background and Objectives

Friedreich ataxia (FRDA) is an autosomal recessive ataxia with no approved treatments. Leriglitazone is a selective peroxisome proliferator–activated receptor γ agonist that crosses the blood-brain barrier and, in preclinical models, improved mitochondrial function and energy production. We assessed effects of leriglitazone in patients with FRDA in a proof-of-concept study.

Methods

In this double-blind, randomized controlled trial, eligible participants (age 12–60 years) had genetically confirmed FRDA, a Scale for the Assessment and Rating of Ataxia (SARA) total score <25, and a SARA item 1 score of 2–6, inclusive. Key exclusion criteria were age at FRDA onset ≥25 years and history of cardiac dysfunction. Participants were randomly assigned (2:1) to receive a daily, oral, individualized dose of leriglitazone or placebo for 48 weeks. The primary endpoint was the change from baseline to week 48 in spinal cord area (C2-C3) (measured by MRI). Secondary endpoints included the change from baseline to week 48 in iron accumulation in the dentate nucleus (quantitative susceptibility mapping) and totalN-acetylaspartate to myo-inositol (tNAA/mIns) ratio.

Results

Overall, 39 patients were enrolled (mean age 24 years; 43.6% women; mean time since symptom onset 10.5 years): 26 patients received leriglitazone (20 completed) and 13 received placebo (12 completed). There was no difference between groups in spinal cord area from baseline to week 48 (least-squares [LS] mean change [standard error (SE)]: leriglitazone, −0.39 [0.55] mm2; placebo, 0.08 [0.72] mm2;p= 0.61). Iron accumulation in the dentate nucleus was greater with placebo (LS mean change [SE]: leriglitazone, 0.10 [1.33] ppb; placebo, 4.86 [1.84] ppb;p= 0.05), and a numerical difference was seen in tNAA/mIns ratio (LS mean change [SE]: leriglitazone, 0.03 [0.02]; placebo, −0.02 [0.03];p= 0.25). The most frequent adverse event was peripheral edema (leriglitazone 73.1%, placebo 0%).

Discussion

The primary endpoint of change in spinal cord area was not met. Secondary endpoints provide evidence supporting proof of concept for leriglitazone mode of action and, with acceptable safety data, support larger studies in patients with FRDA.

Trial Registration Information

ClinicalTrials.gov:NCT03917225; EudraCT: 2018-004405-64; submitted April 17, 2019; first patient enrolled April 2, 2019.clinicaltrials.gov/ct2/show/NCT03917225?term=NCT03917225&draw=2&rank=1.

Classification of Evidence

This study provides Class I evidence that individualized dosing of leriglitazone, compared with placebo, is not associated with changes in spinal cord area in patients with FRDA.

Effect of diazoxide on Friedreich ataxia models

Friedreich ataxia (FRDA) is an inherited recessive disorder caused by a deficiency in the mitochondrial protein frataxin. There is currently no effective treatment for FRDA available, especially for neurological deficits. In this study, we tested diazoxide, a drug commonly used as vasodilator in the treatment of acute hypertension, on cellular and animal models of FRDA. We first showed that diazoxide increases frataxin protein levels in FRDA lymphoblastoid cell lines, via the mammalian target of rapamycin (mTOR) pathway. We then explored the potential therapeutic effect of diazoxide in frataxin-deficient transgenic YG8sR mice and we found that prolonged oral administration of 3 mpk/d diazoxide was found to be safe, but produced variable effects concerning efficacy. YG8sR mice showed improved beam walk coordination abilities and footprint stride patterns, but a generally reduced locomotor activity. Moreover, they showed significantly increased frataxin expression, improved aconitase activity, and decreased protein oxidation in cerebellum and brain mitochondrial tissue extracts. Further studies are needed before this drug should be considered for FRDA clinical trials.

Frataxin deficiency impairs mitochondrial biogenesis in cells, mice and humans

Friedreich's ataxia (FRDA) is a neurodegenerative disease caused by inherited deficiency of the mitochondrial protein Frataxin (FXN), which has no approved therapy and is an area in which biomarkers are needed for clinical development. Here, we investigated the consequences of FXN deficiency in patient-derived FRDA fibroblast cell models, the FRDA mouse model KIKO, and in whole blood collected from patients with FRDA. We observed decreased mitochondrial copy number in all the three FRDA models tested: cells, mice and patient blood. In addition, we observed 40% residual mitochondrial gene expression in FRDA patient blood. These deficiencies of mitochondrial biogenesis in FRDA cells and patient blood are significantly correlated with FXN expression, consistent with the idea that the decreased mitochondrial biogenesis is a consequence of FXN deficiency. The observations appear relevant to the FRDA pathophysiological mechanism, as FXN-dependent deficiency in mitochondrial biogenesis and consequent mitochondrial bioenergetic defect could contribute to the neurodegenerative process. The observations may also have translational potential, as mitochondrial biogenesis could now be followed as a clinical biomarker of FRDA as a correlate of disease severity, progression, and therapeutic effect. Also, mitochondrial copy number in blood is objective, scalar and more investigator-independent than clinical-neurological patient rating scales. Thus, FXN deficiency causes mitochondrial deficiency in FRDA cells, the KIKO mouse model, and in whole blood of patients with FRDA, and this deficiency could potentially be used in clinical trial design.

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.

Increasing frataxin gene expression with histone deacetylase inhibitors as a therapeutic approach for Friedreich's ataxia

The genetic defect in Friedreich's ataxia (FRDA) is the expansion of a GAA·TCC triplet in the first intron of the FXN gene, which encodes the mitochondrial protein frataxin. Previous studies have established that the repeats reduce transcription of this essential gene, with a concomitant decrease in frataxin protein in affected individuals. As the repeats do not alter the FXN protein coding sequence, one therapeutic approach would be to increase transcription of pathogenic FXN genes. Histone posttranslational modifications near the expanded repeats are consistent with heterochromatin formation and FXN gene silencing. In an effort to find small molecules that would reactivate this silent gene, histone deacetylase inhibitors were screened for their ability to up-regulate FXN gene expression in patient cells and members of the pimelic 2-aminobenzamide family of class I histone deacetylase inhibitors were identified as potent inducers of FXN gene expression and frataxin protein. Importantly, these molecules up-regulate FXN expression in human neuronal cells derived from patient-induced pluripotent stem cells and in two mouse models for the disease. Preclinical studies of safety and toxicity have been completed for one such compound and a phase I clinical trial in FRDA patients has been initiated. Furthermore, medicinal chemistry efforts have identified improved compounds with superior pharmacological properties.