Efficacy of Omaveloxolone in Friedreich's Ataxia: Delayed-Start Analysis of the MOXIe Extension

Relative Bioavailability of Omaveloxolone When Capsules Are Sprinkled Over and Mixed in Applesauce Compared With Administration as Intact Omaveloxolone Capsules: A Phase 1, Randomized, Open-Label, Single-Dose, Crossover Study in Healthy Adults

Omaveloxolone (SKYCLARYS®) is approved for the treatment of Friedreich ataxia (FA) in patients aged ≥16 years in the United States and European Union (EU). The recommended dosage is 150 mg administered orally once daily as three 50-mg capsules. However, some patients with FA may have oropharyngeal dysphagia or difficulty swallowing whole capsules; therefore, alternate method(s) of administration are needed. A Phase 1 clinical study in 32 healthy volunteers evaluated the relative bioavailability, safety, and tolerability of a single dose of omaveloxolone when capsule contents were sprinkled on and mixed in applesauce compared to when taken as intact capsules. Palatability when sprinkled on and mixed in applesauce was assessed with a questionnaire. After a single 150-mg dose, the peak and overall exposures of omaveloxolone were similar irrespective of administration method, with the 90% CIs of the geometric least squares mean ratio (%) for maximum plasma concentration (Cmax), AUC0-t, and AUC0-∞ within the 80% to 125% reference intervals. Omaveloxolone was absorbed more slowly as intact capsules (median tmax, 10 h) compared with sprinkled capsule contents over applesauce (median tmax, 6 h). With chronic daily administration of omaveloxolone to treat FA, the 4-h difference in tmax is not considered clinically relevant. Sprinkled omaveloxolone capsule contents on applesauce were well tolerated, with acceptable palatability and no serious adverse events. Given the similar systemic exposure when capsules were swallowed whole, sprinkling omaveloxolone capsule contents on and mixing in applesauce is a feasible alternative method of administering omaveloxolone and has been included in both the United States and EU prescribing information.

Exploring mitochondrial biomarkers for Friedreich's ataxia: a multifaceted approach

This study presents an in-depth analysis of mitochondrial enzyme activities in Friedreich's ataxia (FA) patients, focusing on the Electron Transport Chain complexes I, II, and IV, the Krebs Cycle enzyme Citrate Synthase, and Coenzyme Q10 levels. It examines a cohort of 34 FA patients, comparing their mitochondrial enzyme activities and clinical parameters, including disease duration and cardiac markers, with those of 17 healthy controls. The findings reveal marked reductions in complexes II and, specifically, IV, highlighting mitochondrial impairment in FA. Additionally, elevated Neurofilament Light Chain levels and cardiomarkers were observed in FA patients. This research enhances our understanding of FA pathophysiology and suggests potential biomarkers for monitoring disease progression. The study underscores the need for further clinical trials to validate these findings, emphasizing the critical role of mitochondrial dysfunction in FA assessment and treatment.

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.

CRPD frontiers in movement disorders Therapeutics: From evidence to treatment and applications: Addressing Patients' Needs in the Management of the Ataxias

The genetic ataxias have no cures and no proven ways to delay progression (no disease-modifying therapies). The acquired ataxias may have treatments that address the underlying cause and may slow or stop progression, but will not reverse damage already sustained. The idiopathic ataxias (of unknown genetic or acquired cause) also have no proven disease-modifying therapies. However, for all patients with ataxia of any cause, there is always something that can be done to improve quality of life-treat associated symptoms, provide information and resources, counsel patient and family, help with insurance and disability concerns, be available to listen and answer the many questions they will have.

Evaluating mFARS in pediatric Friedreich's ataxia: Insights from the FACHILD study

OBJECTIVES

Friedreich ataxia (FRDA) is a rare genetic disorder caused by mutations in the FXN gene, leading to progressive coordination loss and other symptoms. The recently approved omaveloxolone targets this condition but is limited to patients over 16 years of age, highlighting the need for pediatric treatments due to the disorder's early onset and more rapid progression in children. This population also experiences increased non-neurological complications; the FACHILD study aimed to augment and expand the knowledge about the natural history of the disease and clinical outcome assessments for trials in children in FRDA.

METHODS

The study enrolled 108 individuals aged 7-18 years with a confirmed FRDA diagnosis, with visits occurring from October 2017 to November 2022 across three institutions. Several measures were introduced to minimize the impact of the COVID-19 pandemic, including virtual visits. Outcome measures centered on the mFARS score and its subscores, and data were analyzed using mixed models for repeated measures. For context and to avoid misinterpretation, the analysis was augmented with data from patients enrolled in the Friedreich's Ataxia Clinical Outcome Measures Study.

RESULTS

Results confirmed the general usefulness of the mFARS score in children, but also highlighted issues, particularly with the upper limb subscore (FARS B). Increased variability, limited homogeneity across study subgroups, and potential training effects might limit mFARS application in clinical trials in pediatric populations.

INTERPRETATION

The FARS E (Upright Stability) score might be a preferred outcome measure in this patient population.

Inhibiting the Keap1/Nrf2 Protein-Protein Interaction with Protein-Like Polymers

Successful and selective inhibition of the cytosolic protein-protein interaction (PPI) between nuclear factor erythroid 2-related factor 2 (Nrf2) and Kelch-like ECH-associating protein 1 (Keap1) can enhance the antioxidant response, with the potential for a therapeutic effect in a range of settings including in neurodegenerative disease (ND). Small molecule inhibitors have been developed, yet many have off-target effects, or are otherwise limited by poor cellular permeability. Peptide-based strategies have also been attempted to enhance specificity, yet face challenges due to susceptibility to degradation and lack of cellular penetration. Herein, these barriers are overcome utilizing a polymer-based proteomimetics. The protein-like polymer (PLP) consists of a synthetic, lipophilic polymer backbone displaying water soluble Keap1-binding peptides on each monomer unit forming a brush polymer architecture. The PLPs are capable of engaging Keap1 and displacing the cellular protective transcription factor Nrf2, which then translocates to the nucleus, activating the antioxidant response element (ARE). PLPs exhibit increased Keap1 binding affinity by several orders of magnitude compared to free peptides, maintain serum stability, are cell-penetrant, and selectively activate the ARE pathway in cells, including in primary cortical neuronal cultures. Keap1/Nrf2-inhibitory PLPs have the potential to impact the treatment of disease states associated with dysregulation of oxidative stress, such as NDs.

Mitochondria: A source of potential biomarkers for non-communicable diseases

Mitochondria, as an endosymbiont of eukaryotic cells, controls multiple cellular activities, including respiration, reactive oxygen species production, fatty acid synthesis, and death. Though the majority of functional mitochondrial proteins are translated through a nucleus-controlled process, very few of them (∼10%) are translated within mitochondria through their own machinery. Germline and somatic mutations in mitochondrial and nuclear DNA significantly impact mitochondrial homeostasis and function. Such modifications disturbing mitochondrial biogenesis, metabolism, or mitophagy eventually resulted in cellular pathophysiology. In this chapter, we discussed the impact of mitochondria and its dysfunction on several non-communicable diseases like cancer, diabetes, neurodegenerative, and cardiovascular problems. Mitochondrial dysfunction and its outcome could be screened by currently available omics-based techniques, flow cytometry, and high-resolution imaging. Such characterization could be evaluated as potential biomarkers to assess the disease burden and prognosis.

Pharmacotherapeutic strategies for Friedreich Ataxia: a review of the available data

INTRODUCTION

Friedreich ataxia (FRDA) is a rare autosomal recessive disease, marked by loss of coordination as well as impaired neurological, endocrine, orthopedic, and cardiac function. There are many symptomatic medications for FRDA, and many clinical trials have been performed, but only one FDA-approved medication exists.

AREAS COVERED

The relative absence of the frataxin protein (FXN) in FRDA causes mitochondrial dysfunction, resulting in clinical manifestations. Currently, the only approved treatment for FRDA is an Nrf2 activator called omaveloxolone (Skyclarys). Patients with FRDA also rely on various symptomatic medications for treatment. Because there is only one approved medication for FRDA, clinical trials continue to advance in FRDA. Although some trials have not met their endpoints, many current and upcoming clinical trials provide exciting possibilities for the treatment of FRDA.

EXPERT OPINION

The approval of omaveloxolone provides a major advance in FRDA therapeutics. Although well tolerated, it is not curative. Reversal of deficient frataxin levels with gene therapy, protein replacement, or epigenetic approaches provides the most likely prospect for enduring, disease-modifying therapy in the future.

A Milestone in the Treatment of Ataxias: Approval of Omaveloxolone for Friedreich Ataxia

The exciting news about the US FDA approval of omaveloxolone as the first-ever drug to be approved for an inherited ataxia is welcome news for patients and families that deal with this devastating disease as well as for health care providers and investigators with an interest in this and other rare diseases. This event is the culmination of long and fruitful collaboration between patients, their families, clinicians, laboratory researchers, patient advocacy organizations, industry, and regulatory agencies. The process has generated intense discussion about outcome measures, biomarkers, trial design, and the nature of approval process for such diseases. It also has brought hope and enthusiasm for increasingly better therapies for genetic diseases in general.

Omaveloxolone for the treatment of Friedreich ataxia: clinical trial results and practical considerations

INTRODUCTION

Omavaloxolone, an NRF2 activator, recently became the first drug approved specifically for the treatment of Friedreich ataxia (FRDA). This landmark achievement provides a background for a review of the detailed data leading to the approval.

AREAS COVERED

The authors review the data from the 4 major articles on FRDA in the context of the authors' considerable (>1000 patients) experience in treating individuals with FRDA. The data is presented in the context not only of its scientific meaning but also in the practical context of therapy in FRDA.

EXPERT OPINION

Omaveloxolone provides a significant advance in the treatment of FRDA that is likely to be beneficial in a majority of the FRDA population. The data suggesting a benefit is consistent, and adverse issues are relatively modest. The major remaining questions are the subgroups that are most responsive and how long the beneficial effects will remain significant in FRDA patients.

A multi-faceted approach to unravel coding and non-coding gene fusions and target chimeric proteins in ataxia

Ataxia represents a heterogeneous group of neurodegenerative disorders characterized by a loss of balance and coordination, often resulting from mutations in genes vital for cerebellar function and maintenance. Recent advances in genomics have identified gene fusion events as critical contributors to various cancers and neurodegenerative diseases. However, their role in ataxia pathogenesis remains largely unexplored. Our study Hdelved into this possibility by analyzing RNA sequencing data from 1443 diverse samples, including cell and mouse models, patient samples, and healthy controls. We identified 7067 novel gene fusions, potentially pivotal in disease onset. These fusions, notably in-frame, could produce chimeric proteins, disrupt gene regulation, or introduce new functions. We observed conservation of specific amino acids at fusion breakpoints and identified potential aggregate formations in fusion proteins, known to contribute to ataxia. Through AI-based protein structure prediction, we identified topological changes in three high-confidence fusion proteins-TEN1-ACOX1, PEX14-NMNAT1, and ITPR1-GRID2-which could potentially alter their functions. Subsequent virtual drug screening identified several molecules and peptides with high-affinity binding to fusion sites. Molecular dynamics simulations confirmed the stability of these protein-ligand complexes at fusion breakpoints. Additionally, we explored the role of non-coding RNA fusions as miRNA sponges. One such fusion, RP11-547P4-FLJ33910, showed strong interaction with hsa-miR-504-5p, potentially acting as its sponge. This interaction correlated with the upregulation of hsa-miR-504-5p target genes, some previously linked to ataxia. In conclusion, our study unveils new aspects of gene fusions in ataxia, suggesting their significant role in pathogenesis and opening avenues for targeted therapeutic interventions.Communicated by Ramaswamy H. Sarma.

Emerging antioxidant therapies in Friedreich's ataxia

Friedreich's ataxia (FRDA) is a rare childhood neurologic disorder, affecting 1 in 50,000 Caucasians. The disease is caused by the abnormal expansion of the GAA repeat sequence in intron 1 of the FXN gene, leading to the reduced expression of the mitochondrial protein frataxin. The disease is characterised by progressive neurodegeneration, hypertrophic cardiomyopathy, diabetes mellitus and musculoskeletal deformities. The reduced expression of frataxin has been suggested to result in the downregulation of endogenous antioxidant defence mechanisms and mitochondrial bioenergetics, and the increase in mitochondrial iron accumulation thereby leading to oxidative stress. The confirmation of oxidative stress as one of the pathological signatures of FRDA led to the search for antioxidants which can be used as therapeutic modality. Based on this observation, antioxidants with different mechanisms of action have been explored for FRDA therapy since the last two decades. In this review, we bring forth all antioxidants which have been investigated for FRDA therapy and have been signed off for clinical trials. We summarise their various target points in FRDA disease pathway, their performances during clinical trials and possible factors which might have accounted for their failure or otherwise during clinical trials. We also discuss the limitation of the studies completed and propose possible strategies for combinatorial therapy of antioxidants to generate synergistic effect in FRDA patients.

Structural modification of C2-substituents on 1,4-bis(arylsulfonamido)benzene or naphthalene-N,N'-diacetic acid derivatives as potent inhibitors of the Keap1-Nrf2 protein-protein interaction

The Keap1-Nrf2-ARE signaling pathway is an attractive therapeutic target for the prevention and treatment of oxidative stress-associated diseases by activating the cellular expression of cytoprotective enzymes and proteins. Small molecule inhibitors can directly disrupt the Keap1-Nrf2 protein-protein interaction (PPI), resulting in elevated levels of Nrf2 protein and subsequent stimulation of related antioxidant responses. Previously, we found that 1,4-bis(arylsulfonamido)benzene or naphthalene-N,N'-diacetic acid derivatives with an ether type C2-substituent on the benzene or naphthalene core exhibited potent inhibitory activities with IC50's in the submicromolar or nanomolar range. We here describe a more detailed structure-activity relationship study around the C2 substituents containing various polar linkers shedding new insight on their binding interactions with the Keap1 Kelch domain. The key observation from our findings is that the substituents at the C2-position of the benzene or naphthalene scaffold impact their inhibitory potencies in biochemical assays as well as activities in cell culture. The biochemical FP and TR-FRET assays revealed that the naphthalene derivatives 17b and 18 with an additional carboxylate at the C2 were the most active inhibitors against Keap1-Nrf2 PPI. In the cell-based assay, the two compounds were shown to be potent Nrf2 activators of the transcription of the Nrf2-dependent genes, such as HMOX2, GSTM3, and NQO1.

Omaveloxolone: a groundbreaking milestone as the first FDA-approved drug for Friedreich ataxia

Friedreich ataxia (FA) is an inherited autosomal recessive neurodegenerative disease (NDD) characterized primarily by progressive sensory and spinocerebellar ataxia associated with hypertrophic cardiomyopathy. FA is due to an intronic GAA repeat expansion within the frataxin gene (FXN) leading to reduced levels of frataxin (FXN) which causes mitochondrial dysfunction, production of reactive oxygen species (ROS), and altered iron metabolism. To date there is no resolutive cure for FA; however, the FDA has recently approved omaveloxolone - a potent activator of nuclear factor erythroid 2-related factor 2 (NRF2) - as the first treatment for FA. We discuss herein the urgency to find a resolutive cure for NDDs that will most probably be achieved via combinatorial therapy targeting multiple disease pathways, and how omavaloxolone serves as an example for future treatments.

Mitochondrial proteome research: the road ahead

Mitochondria are multifaceted organelles with key roles in anabolic and catabolic metabolism, bioenergetics, cellular signalling and nutrient sensing, and programmed cell death processes. Their diverse functions are enabled by a sophisticated set of protein components encoded by the nuclear and mitochondrial genomes. The extent and complexity of the mitochondrial proteome remained unclear for decades. This began to change 20 years ago when, driven by the emergence of mass spectrometry-based proteomics, the first draft mitochondrial proteomes were established. In the ensuing decades, further technological and computational advances helped to refine these 'maps', with current estimates of the core mammalian mitochondrial proteome ranging from 1,000 to 1,500 proteins. The creation of these compendia provided a systemic view of an organelle previously studied primarily in a reductionist fashion and has accelerated both basic scientific discovery and the diagnosis and treatment of human disease. Yet numerous challenges remain in understanding mitochondrial biology and translating this knowledge into the medical context. In this Roadmap, we propose a path forward for refining the mitochondrial protein map to enhance its discovery and therapeutic potential. We discuss how emerging technologies can assist the detection of new mitochondrial proteins, reveal their patterns of expression across diverse tissues and cell types, and provide key information on proteoforms. We highlight the power of an enhanced map for systematically defining the functions of its members. Finally, we examine the utility of an expanded, functionally annotated mitochondrial proteome in a translational setting for aiding both diagnosis of mitochondrial disease and targeting of mitochondria for treatment.

Red Flags in Primary Mitochondrial Diseases: What Should We Recognize?

Primary mitochondrial diseases (PMDs) are complex group of metabolic disorders caused by genetically determined impairment of the mitochondrial oxidative phosphorylation (OXPHOS). The unique features of mitochondrial genetics and the pivotal role of mitochondria in cell biology explain the phenotypical heterogeneity of primary mitochondrial diseases and the resulting diagnostic challenges that follow. Some peculiar features ("red flags") may indicate a primary mitochondrial disease, helping the physician to orient in this diagnostic maze. In this narrative review, we aimed to outline the features of the most common mitochondrial red flags offering a general overview on the topic that could help physicians to untangle mitochondrial medicine complexity.

Longitudinal changes of SARA scale in Friedreich ataxia: Strong influence of baseline score and age at onset

BACKGROUND

The Scale for Assessment and Rating of Ataxia (SARA) is widely used in different types of ataxias and has been chosen as the primary outcome measure in the European natural history study for Friedreich ataxia (FA).

METHODS

To assess distribution and longitudinal changes of SARA scores and its single items, we analyzed SARA scores of 502 patients with typical-onset FA (<25 years) participating in the 4-year prospective European FA Consortium for Translational Studies (EFACTS). Pattern of disease progression was determined using linear mixed-effects regression models. The chosen statistical model was re-fitted in order to estimate parameters and predict disease progression. Median time-to-change and rate of score progression were estimated using the Kaplan-Meier method and weighted linear regression models, respectively.

RESULTS

SARA score at study enrollment and age at onset were the major predictive factors of total score progression during the 4-year follow-up. To a less extent, age at evaluation also influenced the speed of SARA progression, while disease duration did not improve the prediction of the statistical model. Temporal dynamics of total SARA and items showed a great variability in the speed of score increase during disease progression. Gait item had the highest annual progression rate, with median time for one-point score increase of 1 to 2 years.

INTERPRETATION

Analyses of statistical properties of SARA suggest a variable sensitivity of the scale at different disease stages, and provide important information for population selection and result interpretation in future clinical trials.

Clinical Reasoning: A 48-Year-Old Man With Spasticity and Progressive Ataxia

A 48-year-old man was referred to the movement disorders clinic for 10 years of progressive slurred speech, spasticity, limb incoordination, and wide-based gait. Extensive neurologic workup was inconclusive, including serum and CSF testing, neuroimaging, EMG/NCS, exome sequencing, and mitochondrial testing. An ataxia repeat expansion panel ultimately revealed the final diagnosis. In this report, we review the clinical characteristics of a rare, late-onset, autosomal recessive cerebellar ataxia and discuss the importance of pursuing targeted gene testing to avoid diagnostic delays, especially as new treatments for this and other genetic diseases become available.

Inborn Errors of Metabolism with Ataxia: Current and Future Treatment Options

A number of hereditary ataxias are caused by inborn errors of metabolism (IEM), most of which are highly heterogeneous in their clinical presentation. Prompt diagnosis is important because disease-specific therapies may be available. In this review, we offer a comprehensive overview of metabolic ataxias summarized by disease, highlighting novel clinical trials and emerging therapies with a particular emphasis on first-in-human gene therapies. We present disease-specific treatments if they exist and review the current evidence for symptomatic treatments of these highly heterogeneous diseases (where cerebellar ataxia is part of their phenotype) that aim to improve the disease burden and enhance quality of life. In general, a multimodal and holistic approach to the treatment of cerebellar ataxia, irrespective of etiology, is necessary to offer the best medical care. Physical therapy and speech and occupational therapy are obligatory. Genetic counseling is essential for making informed decisions about family planning.

A potent phosphodiester Keap1-Nrf2 protein-protein interaction inhibitor as the efficient treatment of Alzheimer's disease

The Keap1-Nrf2 pathway has been established as a therapeutic target for Alzheimer's disease (AD). Directly inhibiting the protein-protein interaction (PPI) between Keap1 and Nrf2 has been reported as an effective strategy for treating AD. Our group has validated this in an AD mouse model for the first time using the inhibitor 1,4-diaminonaphthalene NXPZ-2 with high concentrations. In the present study, we reported a new phosphodiester containing diaminonaphthalene compound, POZL, designed to target the PPI interface using a structure-based design strategy to combat oxidative stress in AD pathogenesis. Our crystallographic verification confirms that POZL shows potent Keap1-Nrf2 inhibition. Remarkably, POZL showed its high in vivo anti-AD efficacy at a much lower dosage compared to NXPZ-2 in the transgenic APP/PS1 AD mouse model. POZL treatment in the transgenic mice could effectively ameliorate learning and memory dysfunction by promoting the Nrf2 nuclear translocation. As a result, the oxidative stress and AD biomarker expression such as BACE1 and hyperphosphorylation of Tau were significantly reduced, and the synaptic function was recovered. HE and Nissl staining confirmed that POZL improved brain tissue pathological changes by enhancing neuron quantity and function. Furthermore, it was confirmed that POZL could effectively reverse Aβ-caused synaptic damage by activating Nrf2 in primary cultured cortical neurons. Collectively, our findings demonstrated that the phosphodiester diaminonaphthalene Keap1-Nrf2 PPI inhibitor could be regarded as a promising preclinical candidate of AD.

NRF2 activation suppresses motor neuron ferroptosis induced by the SOD1G93A mutation and exerts neuroprotection in amyotrophic lateral sclerosis

The progressive neurodegenerative disease amyotrophic lateral sclerosis (ALS) is caused by a decline in motor neuron function, resulting in worsened motor impairments, malnutrition, respiratory failure and mortality, and there is a lack of effective clinical treatments. The exact mechanism of motor neuronal degeneration remains unclear. Previously, we reported that ferroptosis, which is characterized by the accumulation of lipid peroxide and glutathione depletion in an iron-dependent manner, contributed to motor neuronal death in ALS cell models with the hSOD1^G93A (human Cu/Zn-superoxide dismutase) gene mutation. In this study, we further explored the role of ferroptosis in motor neurons and its regulation in mutant hSOD1^G93A cell and mouse models. Our results showed that ferroptosis was activated in hSOD1^G93A NSC-34 cells and mouse models, which was accompanied by decreased nuclear retention of nuclear factor erythroid 2-related factor 2 (NRF2) and downregulation of solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4) levels. Moreover, RTA-408, an NRF2 activator, inhibited ferroptosis in hSOD1^G93A NSC-34 cells by upregulating the protein expression of SLC7A11 and GPX4. Moreover, hSOD1^G93A mice treated with RTA-408 showed obvious improvements in body weight and motor function. Our study demonstrated that ferroptosis contributed to the toxicity of motor neurons and that activating NRF2 could alleviate neuronal degeneration in ALS with the hSOD1^G93A mutation.

Omaveloxolone: First Approval

Omaveloxolone (SKYCLARYS™) is an orally active, small molecule semi-synthetic triterpenoid drug that increases antioxidant activity, which is being developed by Reata Pharmaceuticals, Inc. for the treatment of Friedreich's ataxia. In patients with Friedreich's ataxia, the nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathway is suppressed, which is associated with oxidative stress, mitochondrial dysfunction and damage to cells, including central and peripheral neurones. The Nrf2 pathway may be activated by omaveloxolone as it blocks the ubiquitination and degradation of Nrf2. Omaveloxolone was approved in February 2023 in the USA for the treatment of Friedreich's ataxia. This article summarizes the milestones in the development of omaveloxolone leading to this first approval for the treatment of Friedreich's ataxia in adults and adolescents aged 16 years and older.

The KEAP1-NRF2 System and Neurodegenerative Diseases

Significance: Central nervous system (CNS) diseases are disorders of the brain and/or spinal cord and include neurodegenerative diseases such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis. Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor belonging to the cap-n-collar family that harbors a unique basic leucine zipper motif and plays as a master regulator of homeostatic responses. Recent Advances: Kelch-like ECH-associated protein 1 (KEAP1) is an adaptor of the Cullin3 (CUL3)-based ubiquitin E3 ligase that enhances the ubiquitylation of NRF2, which promotes the degradation of NRF2 to suppress its transcriptional activity in the absence of stress. Cysteine residues of KEAP1 are modified under stress conditions, and NRF2 degradation is attenuated, allowing it to accumulate and induce the expression of target genes. This regulatory system is referred to as the KEAP1-NRF2 system and plays a central role in protecting cells against various stresses. NRF2 also negatively regulates the expression of inflammatory cytokine and chemokine genes and suppresses pathological inflammation. As oxidative stress, inflammation, and proteostasis are known to contribute to neurodegenerative diseases, the KEAP1-NRF2 system is an attractive target for the treatment of these diseases. Critical Issues: In mouse models of neurodegenerative diseases, Nrf2 depletion exacerbates symptoms and enhances oxidative damage and inflammation in the CNS. In contrast, chemical or genetic NRF2 activation improves these symptoms. Indeed, the NRF2-activating chemical dimethyl fumarate is now widely used for the clinical treatment of MS. Future Directions: The KEAP1-NRF2 system is a promising therapeutic target for neurodegenerative diseases.