KNS-760704 [(6R)-4,5,6,7-tetrahydro-N6-propyl-2, 6-benzothiazole-diamine dihydrochloride monohydrate] for the treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis: exploring pathophysiology in the context of treatment

Amyotrophic lateral sclerosis (ALS) is a complex, neurodegenerative disorder in which alterations in structural, physiological, and metabolic parameters act synergistically. Over the last decade there has been a considerable focus on developing drugs to slow the progression of the disease. Despite this, only four disease-modifying therapies are approved in North America. Although additional research is required for a thorough understanding of ALS, we have accumulated a large amount of knowledge that could be better integrated into future clinical trials to accelerate drug development and provide patients with improved treatment options. It is likely that future, successful ALS treatments will take a multi-pronged therapeutic approach, targeting different pathways, akin to personalized medicine in oncology. In this review, we discuss the link between ALS pathophysiology and treatments, looking at the therapeutic failures as learning opportunities that can help us refine and optimize drug development.

Safety and Efficacy of Dexpramipexole in Eosinophilic Asthma (EXHALE): A randomized controlled trial

BACKGROUND

There is a need for new and effective oral asthma therapies. Dexpramipexole, an oral eosinophil-lowering drug, has not previously been studied in asthma.

OBJECTIVE

We sought to evaluate the safety and efficacy of dexpramipexole in lowering blood and airway eosinophilia in subjects with eosinophilic asthma.

METHODS

We performed a randomized, double-blind, placebo-controlled proof-of-concept trial in adults with inadequately controlled moderate to severe asthma and blood absolute eosinophil count (AEC) greater than or equal to 300/μL. Subjects were randomly assigned (1:1:1:1) to dexpramipexole 37.5, 75, or 150 mg BID (twice-daily) or placebo. The primary end point was the relative change in AEC from baseline to week 12. Prebronchodilator FEV1 week-12 change from baseline was a key secondary end point. Nasal eosinophil peroxidase was an exploratory end point.

RESULTS

A total of 103 subjects were randomly assigned to dexpramipexole 37.5 mg BID (N = 22), 75 mg BID (N = 26), 150 mg BID (N = 28), or placebo (N = 27). Dexpramipexole significantly reduced placebo-corrected AEC week-12 ratio to baseline, in both the 150-mg BID (ratio, 0.23; 95% CI, 0.12-0.43; P < .0001) and the 75-mg BID (ratio, 0.34; 95% CI, 0.18-0.65; P = .0014) dose groups, corresponding to 77% and 66% reductions, respectively. Dexpramipexole reduced the exploratory end point of nasal eosinophil peroxidase week-12 ratio to baseline in the 150-mg BID (median, 0.11; P = .020) and the 75-mg BID (median, 0.17; P = .021) groups. Placebo-corrected FEV1 increases were observed starting at week 4 (nonsignificant). Dexpramipexole displayed a favorable safety profile.

CONCLUSIONS

Dexpramipexole demonstrated effective eosinophil lowering and was well tolerated. Additional larger clinical trials are needed to understand the clinical efficacy of dexpramipexole in asthma.

The FDA-approved compound, pramipexole and the clinical-stage investigational drug, dexpramipexole, reverse chronic allodynia from sciatic nerve damage in mice, and alter IL-1β and IL-10 expression from immune cell culture

During the onset of neuropathic pain from a variety of etiologies, nociceptors become hypersensitized, releasing neurotransmitters and other factors from centrally-projecting nerve terminals within the dorsal spinal cord. Consequently, glial cells (astrocytes and microglia) in the spinal cord are activated and mediate the release of proinflammatory cytokines that act to enhance pain transmission and sensitize mechanical non-nociceptive fibers which ultimately results in light touch hypersensitivity, clinically observed as allodynia. Pramipexole, a D2/D3 preferring agonist, is FDA-approved for the treatment of Parkinson's disease and demonstrates efficacy in animal models of inflammatory pain. The clinical-stage investigational drug, R(+) enantiomer of pramipexole, dexpramipexole, is virtually devoid of D2/D3 agonist actions and is efficacious in animal models of inflammatory and neuropathic pain. The current experiments focus on the application of a mouse model of sciatic nerve neuropathy, chronic constriction injury (CCI), that leads to allodynia and is previously characterized to generate spinal glial activation with consequent release IL-1β. We hypothesized that both pramipexole and dexpramipexole reverse CCI-induced chronic neuropathy in mice, and in human monocyte cell culture studies (THP-1 cells), pramipexole prevents IL-1β production. Additionally, we hypothesized that in rat primary splenocyte culture, dexpramixole increases mRNA for the anti-inflammatory and pleiotropic cytokine, interleukin-10 (IL-10). Results show that following intravenous pramipexole or dexpramipexole, a profound decrease in allodynia was observed by 1 hr, with allodynia returning 24 hr post-injection. Pramipexole significantly blunted IL-1β protein production from stimulated human monocytes and dexpramipexole induced elevated IL-10 mRNA expression from rat splenocytes. The data support that clinically-approved compounds like pramipexole and dexpramipexole support their application as anti-inflammatory agents to mitigate chronic neuropathy, and provide a blueprint for future, multifaceted approaches for opioid-independent neuropathic pain treatment.

Dexpramipexole Attenuates White Matter Injury to Facilitate Locomotion and Motor Coordination Recovery via Reducing Ferroptosis after Intracerebral Hemorrhage

Deciphering the factors causing damage to white matter fiber bundles and exploring new strategies to alleviate white matter injury (WMI) is a promising treatment to improve neurological impairments after intracerebral hemorrhage (ICH). Ferroptosis usually occurs at perihematomal region and contributes to neuronal death due to reactive oxygen species (ROS) production. Dexpramipexole (DPX) easily crosses the blood brain barrier (BBB) and exerts antioxidative properties by reducing ROS production, while the role of DPX in ferroptosis after ICH remains elusive. Here, our results indicated that ferroptosis played a significant role in WMI resulting from iron and ROS accumulation around hematoma. Further evidence demonstrated that the administration of DPX decreased iron and ROS deposition to inhibit ferroptosis at perihematomal site. With the inhibition of ferroptosis, WMI was alleviated at perihematomal site, thereafter promoting locomotion and motor coordination recovery in mice after ICH. Subsequently, the results showcased that the expression of glutathione peroxidase 4 (GPX4) and ferroptosis suppressing protein 1 (FSP1) was upregulated with the administration of DPX. Collectively, the present study uncovers the underlying mechanism and elucidates the therapeutic effect of DPX on ICH, and even in other central nervous system (CNS) diseases with the presence of ferroptosis.

The Multifaceted Role of GPCRs in Amyotrophic Lateral Sclerosis: A New Therapeutic Perspective?

Amyotrophic lateral sclerosis (ALS) is a degenerating disease involving the motor neurons, which causes a progressive loss of movement ability, usually leading to death within 2 to 5 years from the diagnosis. Much effort has been put into research for an effective therapy for its eradication, but still, no cure is available. The only two drugs approved for this pathology, Riluzole and Edaravone, are onlyable to slow down the inevitable disease progression. As assessed in the literature, drug targets such as protein kinases have already been extensively examined as potential drug targets for ALS, with some molecules already in clinical trials. Here, we focus on the involvement of another very important and studied class of biological entities, G protein-coupled receptors (GPCRs), in the onset and progression of ALS. This workaimsto give an overview of what has been already discovered on the topic, providing useful information and insights that can be used by scientists all around the world who are putting efforts into the fight against this very important neurodegenerating disease.

The medicinal chemistry of mitochondrial dysfunction: a critical overview of efforts to modulate mitochondrial health

Mitochondria are subcellular organelles that perform a variety of critical biological functions, including ATP production and acting as hubs of immune and apoptotic signalling. Mitochondrial dysfunction has been extensively linked to the pathology of multiple neurodegenerative disorders, resulting in significant investment from the drug discovery community. Despite extensive efforts, there remains no disease modifying therapies for neurodegenerative disorders. This manuscript aims to review the compounds historically used to modulate the mitochondrial network through the lens of modern medicinal chemistry, and to offer a perspective on the evidence that relevant exposure was achieved in a representative model and that exposure was likely to result in target binding and engagement of pharmacology. We hope this manuscript will aid the community in identifying those targets and mechanisms which have been convincingly (in)validated with high quality chemical matter, and those for which an opportunity exists to explore in greater depth.

Dexpramipexole attenuates myocardial ischemia/reperfusion injury through upregulation of mitophagy

Reperfusion causes undesirable damage to the ischemic myocardium while restoring the blood flow. In this study, we evaluated the effects of dexpramipexole (DPX) on myocardial injury induced by ischemia/reperfusion (I/R) in-vivo and the hypoxia/reoxygenation (HR) in-vitro and examined the functional mechanisms of DPX. DPX protected cells against H/R-induced mitochondrial dysfunction and prevented H/R damage. Both myocardial infarct size and tissue damage due to I/R was reduced upon DPX treatment. We discovered that DPX enhanced mitophagy in-vivo and in-vitro, which was accompanied by enhanced expression of PINK1 and Parkin. Knock-down of PINK1 and Parkin by specific siRNAs reversed DPX-induced inhibition of myocardial I/R injury. These findings suggest that DPX might protect against myocardial injury via PINK1 and Parkin.

(S)-Pramipexole and Its Enantiomer, Dexpramipexole: A New Chemoenzymatic Synthesis and Crystallographic Investigation of Key Enantiomeric Intermediates

A new chemoenzymatic method has been developed for the synthesis of (S)- and (R)-N-(6-hydroxy-4,5,6,7-tetrahydrobenzo[d]thiazol-2-yl) acetamide, two key synthons for the preparation of (S)-pramipexole, an anti-Parkinson drug, and its enantiomer dexpramipexole, which is currently under investigation for the treatment of eosinophil-associated disorders. These two building blocks have been obtained in good yields and high enantiomeric excess (30% and >98% ee for the R-enantiomer, and 31% and >99% ee for the S- one) through a careful optimization of the reaction conditions, starting from the corresponding racemic mixture and using two consecutive irreversible transesterifications, catalyzed by Candida antarctica lipase type A. Single crystal X-ray analysis has been carried out to unambiguously define the stereochemistry of the two enantiomers, and to explore in depth their three-dimensional features.

From Riluzole to Dexpramipexole via Substituted-Benzothiazole Derivatives for Amyotrophic Lateral Sclerosis Disease Treatment: Case Studies

The 1,3-benzothiazole (BTZ) ring may offer a valid option for scaffold-hopping from indole derivatives. Several BTZs have clinically relevant roles, mainly as CNS medicines and diagnostic agents, with riluzole being one of the most famous examples. Riluzole is currently the only approved drug to treat amyotrophic lateral sclerosis (ALS) but its efficacy is marginal. Several clinical studies have demonstrated only limited improvements in survival, without benefits to motor function in patients with ALS. Despite significant clinical trial efforts to understand the genetic, epigenetic, and molecular pathways linked to ALS pathophysiology, therapeutic translation has remained disappointingly slow, probably due to the complexity and the heterogeneity of this disease. Many other drugs to tackle ALS have been tested for 20 years without any success. Dexpramipexole is a BTZ structural analog of riluzole and was a great hope for the treatment of ALS. In this review, as an interesting case study in the development of a new medicine to treat ALS, we present the strategy of the development of dexpramipexole, which was one of the most promising drugs against ALS.

Neuroprotection induced by dexpramipexole delays disease progression in a mouse model of progressive multiple sclerosis

BACKGROUND AND PURPOSE

Drugs able to counteract progressive multiple sclerosis (MS) represent a largely unmet therapeutic need. Even though the pathogenesis of disease evolution is still obscure, accumulating evidence indicates that mitochondrial dysfunction plays a causative role in neurodegeneration and axonopathy in progressive MS patients. Here, we investigated the effects of dexpramipexole, a compound with a good safety profile in humans and able to sustain mitochondria functioning and energy production, in a mouse model of progressive MS.

EXPERIMENTAL APPROACH

Female non-obese diabetic mice were immunized with MOG_35-55 . Functional, immune and neuropathological parameters were analysed during disease evolution in animals treated or not with dexpramipexole. The compound's effects on bioenergetics and neuroprotection were also evaluated in vitro.

KEY RESULTS

We found that oral treatment with dexpramipexole at a dose consistent with that well tolerated in humans delayed disability progression, extended survival, counteracted reduction of spinal cord mitochondrial DNA content and reduced spinal cord axonal loss of mice. Accordingly, the drug sustained in vitro bioenergetics of mouse optic nerve and dorsal root ganglia and counteracted neurodegeneration of organotypic mouse cortical cultures exposed to the adenosine triphosphate-depleting agents oligomycin or veratridine. Dexpramipexole, however, was unable to affect the adaptive and innate immune responses both in vivo and in vitro.

CONCLUSION AND IMPLICATION

The present findings corroborate the hypothesis that neuroprotective agents may be of relevance to counteract MS progression and disclose the translational potential of dexpramipexole to treatment of progressive MS patients as a stand-alone or adjunctive therapy.

A Therapeutic Role for the F1FO-ATP Synthase

Recently, the F₁F_O-ATP synthase, due to its dual role of life enzyme as main adenosine triphosphate (ATP) maker and of death enzyme, as ATP dissipator and putative structural component of the mitochondrial permeability transition pore (mPTP), which triggers cell death, has been increasingly considered as a drug target. Accordingly, the enzyme offers new strategies to counteract the increased antibiotic resistance. The challenge is to find or synthesize compounds able to discriminate between prokaryotic and mitochondrial F₁F_O-ATP synthase, exploiting subtle structural differences to kill pathogens without affecting the host. From this perspective, the eukaryotic enzyme could also be made refractory to macrolide antibiotics by chemically produced posttranslational modifications. Moreover, because the mitochondrial F₁F_O-ATPase activity stimulated by Ca²⁺ instead of by the natural modulator Mg²⁺ is most likely involved in mPTP formation, effectors preferentially targeting the Ca²⁺-activated enzyme may modulate the mPTP. If the enzyme involvement in the mPTP is confirmed, Ca²⁺-ATPase inhibitors may counteract conditions featured by an increased mPTP activity, such as neurodegenerative and cardiovascular diseases and physiological aging. Conversely, mPTP opening could be pharmacologically stimulated to selectively kill unwanted cells. On the basis of recent literature and promising lab findings, the action mechanism of F₁ and F_O inhibitors is considered. These molecules may act as enzyme modifiers and constitute new drugs to kill pathogens, improve compromised enzyme functions, and limit the deathly enzyme role in pathologies. The enzyme offers a wide spectrum of therapeutic strategies to fight at the molecular level diseases whose treatment is still insufficient or merely symptomatic.

Dexpramipexole enhances hippocampal synaptic plasticity and memory in the rat

Even though pharmacological approaches able to counteract age-dependent cognitive impairment have been highly investigated, drugs improving cognition and memory are still an unmet need. It has been hypothesized that sustaining energy dynamics within the aged hippocampus can boost memory storage by sustaining synaptic functioning and long term potentiation (LTP). Dexpramipexole (DEX) is the first-in-class compound able to sustain neuronal bioenergetics by interacting with mitochondrial F1Fo-ATP synthase. In the present study, for the first time we evaluated the effects of DEX on synaptic fatigue, LTP induction, learning and memory retention. We report that DEX improved LTP maintenance in CA1 neurons of acute hippocampal slices from aged but not young rats. However, we found no evidence that DEX counteracted two classic parameters of synaptic fatigue such as fEPSP reduction or the train area during the high frequency stimulation adopted to induce LTP. Interestingly, patch-clamp recordings in rat hippocampal neurons revealed that DEX dose-dependently inhibited (IC₅₀ 814 nM) the I_A current, a rapidly-inactivating K⁺ current that negatively regulates neuronal excitability as well as cognition and memory processes. In keeping with this, DEX counteracted both scopolamine-induced spatial memory loss in rats challenged in Morris Water Maze test and memory retention in rats undergoing Novel Object Recognition. Overall, the present study discloses the ability of DEX to boost hippocampal synaptic plasticity, learning and memory. In light of the good safety profile of DEX in humans, our findings may have a realistic translational potential to treatment of cognitive disorders.

Dexpramipexole as an oral steroid-sparing agent in hypereosinophilic syndromes

Hypereosinophilic syndromes (HESs) are a heterogeneous group of disorders characterized by peripheral eosinophilia and eosinophil-related end organ damage. Whereas most patients respond to glucocorticoid (GC) therapy, high doses are often necessary, and side effects are common. Dexpramipexole (KNS-760704), an orally bioavailable synthetic aminobenzothiazole, showed an excellent safety profile and was coincidentally noted to significantly decrease absolute eosinophil counts (AECs) in a phase 3 trial for amyotrophic lateral sclerosis. This proof-of-concept study was designed to evaluate dexpramipexole (150 mg orally twice daily) as a GC-sparing agent in HESs. Dual primary end points were (1) the proportion of subjects with ≥50% decrease in the minimum effective GC dose (MED) to maintain AEC <1000/μL and control clinical symptoms, and (2) the MED after 12 weeks of dexpramipexole (MEDD) as a percentage of the MED at week 0. Out of 10 subjects, 40% (95% confidence interval [CI], 12%, 74%) achieved a ≥50% reduction in MED, and the MEDD/MED ratio was significantly <100% (median, 66%; 95% CI, 6%, 98%; P = .03). All adverse events were self-limited, and none led to drug discontinuation. Affected tissue biopsy samples in 2 subjects showed normalization of pathology and depletion of eosinophils on dexpramipexole. Bone marrow biopsy samples after 12 weeks of dexpramipexole showed selective absence of mature eosinophils in responders. Dexpramipexole appears promising as a GC-sparing agent without apparent toxicity in a subset of subjects with GC-responsive HESs. Although the exact mechanism of action is unknown, preliminary data suggest that dexpramipexole may affect eosinophil maturation in the bone marrow. This study was registered at www.clinicaltrials.gov as #NCT02101138.

Energy metabolism in ALS: an underappreciated opportunity?

Amyotrophic lateral sclerosis (ALS) is a relentlessly progressive and fatal neurodegenerative disorder that primarily affects motor neurons. Despite our increased understanding of the genetic factors contributing to ALS, no effective treatment is available. A growing body of evidence shows disturbances in energy metabolism in ALS. Moreover, the remarkable vulnerability of motor neurons to ATP depletion has become increasingly clear. Here, we review metabolic alterations present in ALS patients and models, discuss the selective vulnerability of motor neurons to energetic stress, and provide an overview of tested and emerging metabolic approaches to treat ALS. We believe that a further understanding of the metabolic biology of ALS can lead to the identification of novel therapeutic targets.

Development and validation of a highly sensitive gradient chiral separation of pramipexole in human plasma by LC–MS/MS

Aim: Development of a high-sensitivity chiral LC–MS/MS method was required to evaluate a combination of pramipexole (S-PPX) and its enantiomer dexpramipexole (R-PPX) in a proposed clinical trial. The previously available methods suffered from low sensitivity for the (S)-enantiomer in the presence of the more abundant (R)-enantiomer. Based on the projected dosing regimen in the clinical trial, a 5000-fold improvement in sensitivity was required for the (S)-enantiomer. Methodology: Spiked human plasma samples were extracted by liquid–liquid extraction using ethyl acetate and injected onto a CHIRALPAK ID column under pH gradient conditions. Conclusion: An improved analytical method was developed and validated with a final LLQ for (S)-PPX of 0.1 ng/ml in the presence of 2000 ng/ml of (R)-PPX.

ALS Clinical Trials Review: 20 Years of Failure. Are We Any Closer to Registering a New Treatment?

Amyotrophic lateral sclerosis (ALS) is a devastating condition with an estimated mortality of 30,000 patients a year worldwide. The median reported survival time since onset ranges from 24 to 48 months. Riluzole is the only currently approved mildly efficacious treatment. Riluzole received marketing authorization in 1995 in the USA and in 1996 in Europe. In the years that followed, over 60 molecules have been investigated as a possible treatment for ALS. Despite significant research efforts, the overwhelming majority of human clinical trials (CTs) have failed to demonstrate clinical efficacy. In the past year, oral masitinib and intravenous edaravone have emerged as promising new therapeutics with claimed efficacy in CTs in ALS patients. Given their advanced phase of clinical development one may consider these drugs as the most likely near-term additions to the therapeutic arsenal available for patients with ALS. In terms of patient inclusion, CT with masitinib recruited a wider, more representative, less restrictive patient population in comparison to the only successful edaravone CT (edaravone eligibility criteria represents only 18% of masitinib study patients). The present manuscript reviews >50 CTs conducted in the last 20 years since riluzole was first approved. A special emphasis is put on the analysis of existing evidence in support of the clinical efficacy of edaravone and masitinib and the possible implications of an eventual marketing authorisation in the treatment of ALS.

N-Adamantyl-4-Methylthiazol-2-Amine Attenuates Glutamate-Induced Oxidative Stress and Inflammation in the Brain

In this study, we explored the possible mechanisms underlying the neuroprotective and anti-oxidative effects of N-adamantyl-4-methylthiazol-2-amine (KHG26693) against in vivo glutamate-induced toxicity in the rat cerebral cortex. Our results showed that pretreatment with KHG26693 significantly attenuated glutamate-induced elevation of lipid peroxidation, tumor necrosis factor-α, interferon gamma, IFN-γ, interleukin-1β, nitric oxide, reactive oxygen species, NADPH oxidase, caspase-3, calpain activity, and Bax. Furthermore, KHG26693 pretreatment attenuated key antioxidant parameters such as levels of superoxide dismutase, catalase, glutathione, and glutathione reductase. KHG26693 also attenuated the protein levels of inducible nitric oxide synthase, neuronal nitric oxide synthase, nuclear factor erythroid 2-related factor 2, heme oxygenase-1, and glutamate cysteine ligase catalytic subunit caused by glutamate toxicity. Finally, KHG26693 mitigated glutamate-induced changes in mitochondrial ATP level and cytochrome oxidase c. Thus, KHG26693 functions as neuroprotective and anti-oxidative agent against glutamate-induced toxicity through its antioxidant and anti-inflammatory activities in rat brain at least in part.

The targeted eosinophil-lowering effects of dexpramipexole in clinical studies

Dexpramipexole, an orally bioavailable small molecule previously under clinical development in amyotrophic lateral sclerosis, was observed during routine safety hematology monitoring to demonstrate pronounced, dose- and time-dependent eosinophil-lowering effects, with minor reductions on other leukocyte counts. Analysis of hematology lab values across two double-blind, randomized placebo-controlled clinical trials at total daily doses ranging from 50mg to 300mg demonstrated that dexpramipexole consistently and markedly lowered peripheral blood eosinophils. This effect developed after 1month on treatment, required 3-4months to reach its maximum, remained constant throughout treatment, and partially recovered to baseline levels upon drug withdrawal. All doses tested were well tolerated. The overall adverse event rate was similar for dexpramipexole and placebo, and notably with no increase in infection-related adverse events associated with eosinophil-lowering effects. Given the reliance on and insufficiency of off-label chronic corticosteroid therapy for hypereosinophilic syndromes and other eosinophilic-associated diseases (EADs), a need exists for less toxic, more effective, targeted therapeutic alternatives. Further clinical studies are underway to assess the eosinophil-lowering effect of dexpramipexole in the peripheral blood and target tissues of EAD patients and whether such reductions, if observed, produce clinically important benefits.

Metabolic Dysfunctions in Amyotrophic Lateral Sclerosis Pathogenesis and Potential Metabolic Treatments

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease primarily characterized by loss of motor neurons in brain and spinal cord. The death of motor neurons leads to denervation of muscle which in turn causes muscle weakness and paralysis, decreased respiratory function and eventually death. Growing evidence indicates disturbances in energy metabolism in patients with ALS and animal models of ALS, which are likely to contribute to disease progression. Particularly, defects in glucose metabolism and mitochondrial dysfunction limit the availability of ATP to CNS tissues and muscle. Several metabolic approaches improving mitochondrial function have been investigated in vitro and in vivo and showed varying effects in ALS. The effects of metabolic approaches in ALS models encompass delays in onset of motor symptoms, protection of motor neurons and extension of survival, which signifies an important role of metabolism in the pathogenesis of the disease. There is now an urgent need to test metabolic approaches in controlled clinical trials. In addition, more detailed studies to better characterize the abnormalities in energy metabolism in patients with ALS and ALS models are necessary to develop metabolically targeted effective therapies that can slow the progression of the disease and prolong life for patients with ALS.

Neuroprotective effects of N-adamantyl-4-methylthiazol-2-amine against amyloid β-induced oxidative stress in mouse hippocampus

We previously reported that N-adamantyl-4-methylthiazol-2-amine (KHG26693) suppresses amyloid beta (Aβ)-induced neuronal oxidative damage in cortical neurons. Here we investigated the mechanism and antioxidative function of KHG26693 in the hippocampus of Aβ-treated mice. KHG26693 significantly attenuated Aβ-induced TNF-α and IL-1β enhancements. KHG26693 decreased Aβ-mediated malondialdehyde formation, protein oxidation, and reactive oxygen species by decreasing the iNOS level. KHG26693 suppressed Aβ-induced oxidative stress through a mechanism involving glutathione peroxidase, catalase, and GSH attenuation. Aβ-induced MMP-2, cPLA2, and pcPLA2 expressions were almost completely attenuated by KHG26693 treatment, suggesting that Aβ-induced oxidative stress reduction by KHG26693 is, at least partly, caused by the downregulation of MMP-2 and cPLA2 activation. Compared with Aβ treatment, KHG26693 treatment upregulated Nrf2 and HO-1 expressions, suggesting that KHG26693 protects the brain from Aβ-induced oxidative damage, likely by maintaining redox balance through Nrf2/HO-1 pathway regulation. KHG26693 significantly attenuated Aβ-induced oxidative stress in the hippocampus of Aβ-treated mice.

N-Adamantyl-4-methylthiazol-2-amine suppresses amyloid β-induced neuronal oxidative damage in cortical neurons

Recently, we have reported that N-adamantyl-4-methylthiazol-2-amine (KHG26693) successfully reduced the production of oxidative stress in streptozotocin-induced diabetic rats and lipopolysaccharide-induced BV-2 microglial cells by increasing their antioxidant capacity. However, antioxidative effects of KHG26693 against Aβ (Aβ)-induced oxidative stress have not yet been reported. In the present study, we further investigated the antioxidative function of KHG26693 in Aβ-mediated primary cultured cortical neurons. We showed here that KHG26693 attenuated Aβ-induced cytotoxicity, increase of Bax/Bcl-2 ratio, elevation of caspase-3 expression, and impairment of mitochondrial membrane potential in cultured primary cortical neurons. KHG26693 also decreases the Aβ-mediated formation of malondialdehyde, reactive oxygen species, and NO production by decreasing nitric oxide synthase (iNOS) and NADPH oxidase level. Moreover, KHG26693 suppress the Aβ-induced oxidative stress through a possible mechanism involving attenuation of GSH and antioxidant enzyme activities such as glutathione reductase and glutathione peroxidase (GPx). Finally, pretreatment of cortical neurons with KHG26693 significantly reduced the Aβ-induced protein oxidation and nitration. To our knowledge, this is the first report, showing that KHG26693 significantly attenuates Aβ-induced oxidative stress in primary cortical neurons, and may prove attractive strategies to reduce Aβ-induced neural cell death.

Is Modulation of Oxidative Stress an Answer? The State of the Art of Redox Therapeutic Actions in Neurodegenerative Diseases

The central nervous system is particularly sensitive to oxidative stress due to many reasons, including its high oxygen consumption even under basal conditions, high production of reactive oxygen and nitrogen species from specific neurochemical reactions, and the increased deposition of metal ions in the brain with aging. For this reason, along with inflammation, oxidative stress seems to be one of the main inducers of neurodegeneration, causing excitotoxicity, neuronal loss, and axonal damage, ultimately being now considered a key element in the onset and progression of several neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, and hereditary spastic paraplegia. Thus, the present paper reviews the role of oxidative stress and of its mechanistic insights underlying the pathogenesis of these neurodegenerative diseases, with particular focus on current studies on its modulation as a potential and promising therapeutic strategy.

A retrospective review of the progress in amyotrophic lateral sclerosis drug discovery over the last decade and a look at the latest strategies

INTRODUCTION

Drug discovery for amyotrophic lateral sclerosis (ALS) has experienced a surge in clinical studies and remarkable preclinical milestones utilizing a variety of mutant superoxide dismutase 1 model systems. Of the drugs that were tested and showed positive preclinical effects, none demonstrated therapeutic benefits to ALS patients in clinical settings.

AREAS COVERED

This review discusses the advances made in drug discovery for ALS and highlights why drug development is proving to be so difficult. It also discusses how a closer look at both preclinical and clinical studies could uncover the reasons why these preclinical successes have yet to result in the availability of an effective drug for clinical use.

EXPERT OPINION

Valuable lessons from the numerous preclinical and clinical studies supply the biggest advantage in the monumental task of finding a cure for ALS. Obviously, a single design type for ALS clinical trials has not yielded success. The authors suggest a two-pronged approach that may prove essential to achieve clinical efficacy in the identification of novel targets and preclinical testing in multiple models to identify biomarkers that can function in diagnostic, predictive and prognostic roles, and changes to clinical trial design and patient recruitment criteria. The advancement of technology and invention of more powerful tools will further enhance the above. This will give rise to more sophisticated clinical trials with consideration of a range of criteria from: optimum dose, route of delivery, specific biomarkers, pharmacokinetics, pharmacodynamics and toxicology to biomarkers, timing for trial and patients' clinical status.

Potential therapeutic drugs and methods for the treatment of amyotrophic lateral sclerosis

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disorder caused by damage of motoneurons leading to paralysis state and long term disability. Riluzole is currently the only FDA-approved drug for the treatment of ALS. The proposed mechanisms of ALS include glutamate excitotoxicity, oxidative stress, mitochondrial dysfunction, protein aggregation, SOD1 accumulations, and neuronal death. In this review, we discuss potential biomarkers for the identification of patients with ALS. We further emphasize potential therapy involving the uses of neurotrophic factors such as IGFI, GDNF, VEGF, ADNF-9, colivelin and angiogenin in the treatment of ALS. Moreover, we described several existing drugs such as talampanel, ceftriaxone, pramipexole, dexpramipexole and arimoclomol potential compounds for the treatment of ALS. Interestingly, the uses of stem cell therapy and immunotherapy are promising for the treatment of ALS.

Antioxidative effects of ethyl 2-(3-(benzo[d]thiazol-2-yl)ureido)acetate against amyloid β-induced oxidative cell death via NF-κB, GSK-3β and β-catenin signaling pathways in cultured cortical neurons

We have previously shown that 2-(3-(benzo[d]thiazol-2-yl)ureido)acetate (KHG21834) attenuates amyloid beta(Aβ)25-35-induced apoptotic death and shows anti-inflammatory activity against Aβ25-35-induced microglial activation. However, antioxidative effects of KHG21834 against Aβ-induced oxidative stress have not yet been reported. In the present study, we investigated the antioxidative function of KHG21834 in primary cultured cortical neurons, to expand the potential therapeutic efficacy of KHG21834. Pretreatment with KHG21834 protected against Aβ-induced neuronal cell death and mitochondrial damage, and significantly restored GSH levels and the activities of catalase, superoxide dismutase, and glutathione peroxidase, and also suppressed the production of reactive oxygen species and protein oxidation. These results imply that KHG21834 may play a role in cellular defense mechanisms against Aβ-induced oxidative stress in cultured cortical neurons. Furthermore, KHG21834 significantly attenuated the effects of Aβ treatment on levels of NF-κB, β-catenin, and GSK-3β proteins in cortical neurons. Taken together, our results suggest that the antioxidant effects of KHG21834 may result at least in part from its ability to regulate the NF-κB, β-catenin, and GSK-3β signaling pathways. To our knowledge, this is the first report showing that KHG21834 significantly attenuates Aβ25-35-induced oxidative stress in primary cortical neurons, and provides novel insights into KHG21834 as a possible therapeutic agent for the treatment of Aβ-mediated neurotoxicity involving oxidative stress.

The mitochondrial complex V-associated large-conductance inner membrane current is regulated by cyclosporine and dexpramipexole

Inefficiency of oxidative phosphorylation can result from futile leak conductance through the inner mitochondrial membrane. Stress or injury may exacerbate this leak conductance, putting cells, and particularly neurons, at risk of dysfunction and even death when energy demand exceeds cellular energy production. Using a novel method, we have recently described an ion conductance consistent with mitochondrial permeability transition pore (mPTP) within the c-subunit of the ATP synthase. Excitotoxicity, reactive oxygen species-producing stimuli, or elevated mitochondrial matrix calcium opens the channel, which is inhibited by cyclosporine A and ATP/ADP. Here we show that ATP and the neuroprotective drug dexpramipexole (DEX) inhibited an ion conductance consistent with this c-subunit channel (mPTP) in brain-derived submitochondrial vesicles (SMVs) enriched for F1FO ATP synthase (complex V). Treatment of SMVs with urea denatured extramembrane components of complex V, eliminated DEX- but not ATP-mediated current inhibition, and reduced binding of [(14)C]DEX. Direct effects of DEX on the synthesis and hydrolysis of ATP by complex V suggest that interaction of the compound with its target results in functional conformational changes in the enzyme complex. [(14)C]DEX bound specifically to purified recombinant b and oligomycin sensitivity-conferring protein subunits of the mitochondrial F1FO ATP synthase. Previous data indicate that DEX increased the efficiency of energy production in cells, including neurons. Taken together, these studies suggest that modulation of a complex V-associated inner mitochondrial membrane current is metabolically important and may represent an avenue for the development of new therapeutics for neurodegenerative disorders.

Pharmacokinetics of renally excreted drug dexpramipexole in subjects with impaired renal function

This phase I, open-label, single-dose study evaluated the pharmacokinetics, safety, and tolerability of renally excreted drug dexpramipexole in subjects with normal and impaired renal function, i.e. mild, moderate, severe renal impairment, or end-stage renal disease (ESRD) requiring hemodialysis when matched by age and sex. Dexpramipexole area under the curves (AUCs), but not C_max, were significantly increased with the severity of renal impairment after a single dose administration. The geometric mean ratio of dose-normalized AUC_(0–72) was 1.4, 1.7, 2.7, and 4.5, respectively, in mild, moderate, severe renal impairment, and ESRD subjects when compared to healthy subjects. There was a strong association between renal function (eGFR) and dexpramipexole CLr. The slope (90% confidence interval(CI)) of eGFR and renal clearance (CLr) in the regression model was 3.1 (2.4, 3.7). Dexpramipexole elimination in ESRD subjects during both dialysis and non-dialysis (i.e., interval between dialysis) was insignificant. Single 75 mg and 150 mg doses of dexpramipexole were well tolerated, and the safety profile was comparable across renal function groups. Extensive drug accumulation may occur with repeated dosing in patients with significant renal impairment. It is recommended that dexpramipexole not to be given to patients with severe renal impairment or in those with ESRD.

Anti-inflammatory mechanisms of N-adamantyl-4-methylthiazol-2-amine in lipopolysaccharide-stimulated BV-2 microglial cells

The activation of microglia is crucially associated with the neurodegeneration observed in many neuroinflammatory pathologies, such as multiple sclerosis, Parkinson's disease, and Alzheimer's disease. We have examined various thiazole derivatives with the goal of developing new anti-neuroinflammatory drugs. Thiazole derivatives are attractive candidates for drug development, because they are efficiently synthesized and active against a number of disease organisms and conditions, including neurodegenerative disorders. The present study investigated the effects of a new compound, N-adamantyl-4-methylthiazol-2-amine (KHG26693), against lipopolysaccharide (LPS)-induced inflammation in cultured BV-2 microglial cells. KHG26693 suppressed several inflammatory responses in LPS-activated cells, as evidenced by decreased levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), hydrogen peroxide (H(2)O(2)), reactive oxygen species (ROS), nitric oxide (NO), and lipid peroxidation. These anti-inflammatory/antioxidative actions occurred as a result of the downregulation of NADPH oxidase (NOX), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) content, but not as a result of the upregulation of superoxide dismutase (SOD) or catalase activity. The pharmacological properties of KHG26693 were also facilitated via inhibition of both the cluster of differentiation 14 (CD14)/toll-like receptor 4 (TLR4)-dependent nuclear factor kappa B (NF-κB) signaling pathway and extracellular signal-regulated kinase (ERK) phosphorylation. Furthermore, KHG26693 successfully blocked the migration of LPS-activated microglia, most likely by modulating the ERK pathway. Taken together, these results demonstrate that the anti-inflammatory and antioxidative actions of KHG26693 are mediated, at least in part, through the control of microglial activation.

Therapeutic neuroprotective agents for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a fatal chronic neurodegenerative disease whose hallmark is proteinaceous, ubiquitinated, cytoplasmic inclusions in motor neurons and surrounding cells. Multiple mechanisms proposed as responsible for ALS pathogenesis include dysfunction of protein degradation, glutamate excitotoxicity, mitochondrial dysfunction, apoptosis, oxidative stress, and inflammation. It is therefore essential to gain a better understanding of the underlying disease etiology and search for neuroprotective agents that might delay disease onset, slow progression, prolong survival, and ultimately reduce the burden of disease. Because riluzole, the only Food and Drug Administration (FDA)-approved treatment, prolongs the ALS patient's life by only 3 months, new therapeutic agents are urgently needed. In this review, we focus on studies of various small pharmacological compounds targeting the proposed pathogenic mechanisms of ALS and discuss their impact on disease progression.

Rodent models of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterised by the degeneration of upper and lower motor neurons. Recent advances in our understanding of some of the genetic causes of ALS, such as mutations in SOD1, TARDBP, FUS and VCP have led to the generation of rodent models of the disease, as a strategy to help our understanding of the pathophysiology of ALS and to assist in the development of therapeutic strategies. This review provides detailed descriptions of TDP-43, FUS and VCP models of ALS, and summarises potential therapeutics which have been recently trialled in rodent models of the disease. This article is part of a Special Issue entitled: Animal Models of Disease.

Renal dopamine receptors, oxidative stress, and hypertension

Dopamine, which is synthesized in the kidney, independent of renal nerves, plays an important role in the regulation of fluid and electrolyte balance and systemic blood pressure. Lack of any of the five dopamine receptor subtypes (D1R, D2R, D3R, D4R, and D5R) results in hypertension. D1R, D2R, and D5R have been reported to be important in the maintenance of a normal redox balance. In the kidney, the antioxidant effects of these receptors are caused by direct and indirect inhibition of pro-oxidant enzymes, specifically, nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase, and stimulation of anti-oxidant enzymes, which can also indirectly inhibit NADPH oxidase activity. Thus, stimulation of the D2R increases the expression of endogenous anti-oxidants, such as Parkinson protein 7 (PARK7 or DJ-1), paraoxonase 2 (PON2), and heme oxygenase 2 (HO-2), all of which can inhibit NADPH oxidase activity. The D5R decreases NADPH oxidase activity, via the inhibition of phospholipase D2, and increases the expression of HO-1, another antioxidant. D1R inhibits NADPH oxidase activity via protein kinase A and protein kinase C cross-talk. In this review, we provide an overview of the protective roles of a specific dopamine receptor subtype on renal oxidative stress, the different mechanisms involved in this effect, and the role of oxidative stress and impairment of dopamine receptor function in the hypertension that arises from the genetic ablation of a specific dopamine receptor gene in mice.

[Amyotrophic lateral sclerosis: update on etiological treatment]

Amyotrophic lateral sclerosis is a rare neurodegenerative disease. It is characterized by motoneurons progressive degeneration. Associated with a paralysis of the legs, arms and the respiratory muscles, its evolution is lethal. Riluzole is the only drug available with an marketing authorisation (autorisation de mise sur le marché [AMM]) in this indication. In the beginning stages of the disease it demonstrated a modest efficacy by prolonging survival for a few months. Although the physiopathological mechanisms of this disease have not been totally solved, the progression of knowledge in recent years in this area led to the development of a large number of neuroprotective agents which showed effective results in animal models of ALS and which could be good candidates for the treatment of ALS. Several clinical trials have been conducted about antiglutamatergic, antioxidant, antiapoptotic agents and growing cell factors but they failed to demonstrate efficacy on survival or quality of life. Therefore, clinical trials using innovative therapeutics and stem cells are ongoing and offer more distant hope.

A small molecule screen in stem-cell-derived motor neurons identifies a kinase inhibitor as a candidate therapeutic for ALS

Amyotrophic lateral sclerosis (ALS) is a rapidly progressing neurodegenerative disease, characterized by motor neuron (MN) death, for which there are no truly effective treatments. Here, we describe a new small molecule survival screen carried out using MNs from both wild-type and mutant SOD1 mouse embryonic stem cells. Among the hits we found, kenpaullone had a particularly impressive ability to prolong the healthy survival of both types of MNs that can be attributed to its dual inhibition of GSK-3 and HGK kinases. Furthermore, kenpaullone also strongly improved the survival of human MNs derived from ALS-patient-induced pluripotent stem cells and was more active than either of two compounds, olesoxime and dexpramipexole, that recently failed in ALS clinical trials. Our studies demonstrate the value of a stem cell approach to drug discovery and point to a new paradigm for identification and preclinical testing of future ALS therapeutics.

Amyotrophic lateral sclerosis and the clinical potential of dexpramipexole

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative disorder that leads to progressive weakness from loss of motor neurons and death on average in less than 3 years after symptom onset. No clear causes have been found and just one medication, riluzole, extends survival. Researchers have identified some of the cellular processes that occur after disease onset, including mitochondrial dysfunction, protein aggregation, oxidative stress, excitotoxicity, inflammation, and apoptosis. Mitochondrial disease may be a primary event in neurodegeneration or occur secondary to other cellular processes, and may itself contribute to oxidative stress, excitotoxicity, and apoptosis. Clinical trials currently aim to slow disease progression by testing drugs that impact one or more of these pathways. While every agent tested in the 18 years after the approval of riluzole has been ineffective, basic and clinical research methods in ALS have become dramatically more sophisticated. Dexpramipexole (RPPX), the R(+) enantiomer of pramiprexole, which is approved for symptomatic treatment of Parkinson disease, carries perhaps the currently largest body of pre-and early clinical data that support testing in ALS. The neuroprotective properties of RPPX in various models of neurodegeneration, including the ALS murine model, may be produced through protective actions on mitochondria. Early phase trials in human ALS suggest that the drug can be taken safely by patients in doses that provide neuroprotection in preclinical models. A Phase III trial to test the efficacy of RPPX in ALS is underway.

Clinical utility of neuroprotective agents in neurodegenerative diseases: current status of drug development for Alzheimer's, Parkinson's and Huntington's diseases, and amyotrophic lateral sclerosis

INTRODUCTION

According to the definition of the Committee to Identify Neuroprotective Agents in Parkinson's Disease (CINAPS), "neuroprotection would be any intervention that favourably influences the disease process or underlying pathogenesis to produce enduring benefits for patients" [Meissner W, et al. Trends Pharmacol Sci 2004;25:249-253]. Preferably, neuroprotective agents should be used before or eventually during the prodromal phase of the diseases that could start decades before the appearance of symptoms. Although several symptomatic drugs are available, a disease-modifying agent is still elusive.

AREAS COVERED

The aim of the present review is to give an overview of neuroprotective agents being currently investigated for the treatment of AD, PD, HD and ALS in clinical phases.

EXPERT OPINION

Development of effective neuroprotective therapies resulting in clinically meaningful results is hampered by several factors in all research stages, both conceptual and methodological. Novel solutions might be offered by evaluation of new targets throughout clinical studies, therapies emerging from drug repositioning approaches, multi-target approaches and network pharmacology.

Effects of dexpramipexole on brain mitochondrial conductances and cellular bioenergetic efficiency

Cellular stress or injury can result in mitochondrial dysfunction, which has been linked to many chronic neurological disorders including amyotrophic lateral sclerosis (ALS) and Parkinson's disease (PD). Stressed and dysfunctional mitochondria exhibit an increase in large conductance mitochondrial membrane currents and a decrease in bioenergetic efficiency. Inefficient energy production puts cells, and particularly neurons, at risk of death when energy demands exceed cellular energy production. Here we show that the candidate ALS drug dexpramipexole (DEX; KNS-760704; ((6R)-4,5,6,7-tetrahydro-N6-propyl-2,6-benzothiazole-diamine) and cyclosporine A (CSA) inhibited increases in ion conductance in whole rat brain-derived mitochondria induced by calcium or treatment with a proteasome inhibitor, although only CSA inhibited calcium-induced permeability transition in liver-derived mitochondria. In several cell lines, including cortical neurons in culture, DEX significantly decreased oxygen consumption while maintaining or increasing production of adenosine triphosphate (ATP). DEX also normalized the metabolic profile of injured cells and was protective against the cytotoxic effects of proteasome inhibition. These data indicate that DEX increases the efficiency of oxidative phosphorylation, possibly by inhibition of a CSA-sensitive mitochondrial conductance.

Chronic inflammatory disorders and their redox control: from molecular mechanisms to therapeutic opportunities

A chronic inflammatory disease is a condition characterized by persistent inflammation. A number of human pathologies fall into this category, and a great deal of research has been conducted to learn more about their characteristics and underlying mechanisms. In many cases, a genetic component has been identified, but also external factors like food, smoke, or environmental pollutants can significantly contribute to worsen their symptoms. Accumulated evidence clearly shows that chronic inflammatory diseases are subjected to a redox control. Here, we shall review the identity, source, regulation, and biological activity of redox molecules, to put in a better perspective their key-role in cancer, diabetes, cardiovascular diseases, atherosclerosis, chronic obstructive pulmonary diseases, and inflammatory bowel diseases. In addition, the impact of redox species on autoimmune disorders (rheumatoid arthritis, systemic lupus erythematosus, psoriasis, and celiac disease) and neurodegenerative diseases (Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, and multiple sclerosis) will be discussed, along with their potential therapeutic implications as novel drugs to combat chronic inflammatory disorders.

Neuroprotective strategies involving ROS in Alzheimer disease

Alzheimer disease (AD) is a neurodegenerative disorder in which oxidative stress is a key hallmark. It occurs early in disease pathogenesis and can exacerbate its progression. Several causes of oxidative stress have been determined over the years. First, mitochondria play an important role in the generation and accumulation of free radicals. In addition to mitochondria, inflammation can also induce oxidative damage, especially via microglia, and microglia are also important for Aβ clearance. In AD, both mitochondrial function and inflammatory response are affected, leading to increased ROS formation and oxidative damage to lipid, proteins, and nucleic acids. Some other sources have also been identified. From these findings, various neuroprotective strategies against ROS-mediated damages have been elaborated in AD research. This review recapitulates some of the major strategies used to prevent oxidative stress and disease progression. Outcomes from in vitro and in vivo studies using models of AD are encouraging. However, only a few clinical trials have provided positive results in terms of slowing down cognitive decline. Nonetheless, there is still hope for improved compounds that would better target pathways implicated in ROS production. In fact, facilitating the endogenous antioxidant system by modulating transcription has great promise for AD therapy.

Dopamine and renal function and blood pressure regulation

Dopamine is an important regulator of systemic blood pressure via multiple mechanisms. It affects fluid and electrolyte balance by its actions on renal hemodynamics and epithelial ion and water transport and by regulation of hormones and humoral agents. The kidney synthesizes dopamine from circulating or filtered L-DOPA independently from innervation. The major determinants of the renal tubular synthesis/release of dopamine are probably sodium intake and intracellular sodium. Dopamine exerts its actions via two families of cell surface receptors, D1-like receptors comprising D1R and D5R, and D2-like receptors comprising D2R, D3R, and D4R, and by interactions with other G protein-coupled receptors. D1-like receptors are linked to vasodilation, while the effect of D2-like receptors on the vasculature is variable and probably dependent upon the state of nerve activity. Dopamine secreted into the tubular lumen acts mainly via D1-like receptors in an autocrine/paracrine manner to regulate ion transport in the proximal and distal nephron. These effects are mediated mainly by tubular mechanisms and augmented by hemodynamic mechanisms. The natriuretic effect of D1-like receptors is caused by inhibition of ion transport in the apical and basolateral membranes. D2-like receptors participate in the inhibition of ion transport during conditions of euvolemia and moderate volume expansion. Dopamine also controls ion transport and blood pressure by regulating the production of reactive oxygen species and the inflammatory response. Essential hypertension is associated with abnormalities in dopamine production, receptor number, and/or posttranslational modification.

SOD1 and TDP-43 animal models of amyotrophic lateral sclerosis: recent advances in understanding disease toward the development of clinical treatments

Amyotrophic lateral sclerosis (ALS) is a fatal motor neuron disease with no cure. Breakthroughs in understanding ALS pathogenesis came with the discovery of dominant mutations in the superoxide dismutase 1 gene (SOD1) and other genes, including the gene encoding transactivating response element DNA binding protein-43 (TDP-43). This has led to the creation of animal models to further our understanding of the disease and identify a number of ALS-causing mechanisms, including mitochondrial dysfunction, protein misfolding and aggregation, oxidative damage, neuronal excitotoxicity, non-cell autonomous effects and neuroinflammation, axonal transport defects, neurotrophin depletion, effects from extracellular mutant SOD1, and aberrant RNA processing. Here we summarise the SOD1 and TDP-43 animal models created to date, report on recent findings supporting the potential mechanisms of ALS pathogenesis, and correlate this understanding with current developments in the clinic.

Emerging targets and treatments in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron disease that is currently untreatable. Many compounds have been tested in laboratory-based models and in patients with ALS, but so far only one drug, riluzole, has shown efficacy, yet it only slightly slows disease progression. Several new insights into the causes of motor neuron death have led to the identification of some important novel targets for intervention. At no time have studies involved such a wide range of innovations and such advanced technologies. Many promising studies are underway to test potential targets that will hopefully translate into meaningful therapeutics for patients with ALS.

Noninvasive detection of brainstem and spinal cord axonal degeneration in an amyotrophic lateral sclerosis mouse model

Degeneration of motor neurons and their associated axons is a hallmark of amyotrophic lateral sclerosis, but reliable noninvasive lesion detection is lacking. In vivo diffusion tensor imaging was performed to evaluate neurodegeneration in the brainstem and cervical spinal cord of wild-type and G93A-SOD1 transgenic mice, an animal model of amyotrophic lateral sclerosis. A statistically significant reduction in the apparent diffusion coefficient was observed in the motor nuclei VII and XII of G93A-SOD1 transgenic mice relative to wild-type mice. No significant difference in diffusion anisotropy was observed in dorsal white or gray matter in cervical and lumbar segments of the spinal cord. In contrast, statistically significant decreases in axial diffusivity (diffusivity parallel to the axis of the spinal cord) and apparent diffusion coefficient were found in the ventrolateral white matter of G93A-SOD1 mice in both the cervical and lumbar spinal cord. The reduction in axial diffusivity, suggestive of axonal injury, in the white matter of the spinal cord of G93A-SOD1 mice was verified by immunostaining with nonphosphorylated neurofilament. The present study demonstrates that in vivo diffusion tensor imaging-derived axial diffusivity may be used to accurately evaluate axonal degeneration in an animal model of amyotrophic lateral sclerosis.