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Amyotrophic lateral sclerosis (ALS) is a devastating disease caused by degeneration of motor neurons. As with all major neurodegenerative disorders, development of disease-modifying therapies has proven challenging for multiple reasons. Nevertheless, ALS is one of the few neurodegenerative diseases for which disease-modifying therapies are approved. Significant discoveries and advances have been made in ALS preclinical models, genetics, pathology, biomarkers, imaging and clinical readouts over the last 10–15 years. At the same time, novel therapeutic paradigms are being applied in areas of high unmet medical need, including neurodegenerative disorders. These developments have evolved our knowledge base, allowing identification of targeted candidate therapies for ALS with diverse mechanisms of action. In this Review, we discuss how this advanced knowledge, aligned with new approaches, can enable effective translation of therapeutic agents from preclinical studies through to clinical benefit for patients with ALS. We anticipate that this approach in ALS will also positively impact the field of drug discovery for neurodegenerative disorders more broadly.Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease affecting motor neurons. In their Review, Shaw and colleagues provide a comprehensive picture of the various pathological mechanisms involved in this complex disease, and discuss the deep and diverse pipeline under development to tackle these processes. They highlight advances in ALS translational research that might be broadly applicable to other neurodegenerative disorders.

Amyotrophic lateral sclerosis (ALS) is characterized by degeneration of motor neurons in the central nervous system (CNS). Mutations in the metalloenzyme SOD1 are associated with inherited forms of ALS and cause a toxic gain of function thought to be mediated by dimer destabilization and misfolding. SOD1 binds two Cu and two Zn ions in its homodimeric form. We have applied native ambient mass spectrometry imaging to visualize the spatial distributions of intact metal-bound SOD1 G93A complexes in SOD1 G93A transgenic mouse spinal cord and brain sections and evaluated them against disease pathology. The molecular specificity of our approach reveals that metal-deficient SOD1 G93A species are abundant in CNS structures correlating with ALS pathology whereas fully metalated SOD1 G93A species are homogenously distributed. Monomer abundance did not correlate with pathology. We also show that the dimer-destabilizing post-translational modification, glutathionylation, has limited influence on the spatial distribution of SOD1 dimers. In this work, protein-metal complexes implicated in the pathogenesis of amyotrophic lateral sclerosis were mapped by mass spectrometry imaging. Metal-deficient hSOD1G93A complexes were revealed to be localised with disease pathology in the spinal cord and brain.

The majority of preclinical studies in ALS have relied on transgenic models with overexpression of mutant human superoxide dismutase 1 (SOD1), widely regarded to have failed in terms of translation of therapeutic effects. However, there are still no widely accepted models of other genetic subtypes of ALS. The majority of patients show ubiquitinated cytoplasmic inclusions of TAR DNA binding protein of 43 kilodaltons (TDP-43) in spinal motor neurons at the end stage of disease and a small proportion have mutations in TARDBP , the gene encoding TDP-43. TDP-43 transgenic mouse models have been produced, but have not been widely adopted. Here, we characterised one of these models available from the Jackson Laboratory in detail. Compared to TDP-43 WT mice, TDP-43 Q331K mice had 43% less hindlimb muscle mass at 6 months and a 73% reduction in hindlimb compound muscle action potential at 8 months of age. Rotarod and gait analysis indicated motor system decline with elevated weight gain. At the molecular level, the lack of TDP-43 cellular pathology was confirmed with a surprising increase in nuclear TDP-43 in motor neurons. Power analysis indicated group sizes of 12–14 mice are needed to detect 10–20% changes in measured parameters with a power of 80%, providing valid readouts for preclinical testing. Overall, this model may represent a useful component of multi-model pre-clinical therapeutic studies for ALS.

Gene therapies are promising for diseases previously considered incurable. Adeno-associated virus serotype 9 (AAV9) demonstrates remarkable tropism for motor neurons (MNs) and represents an exciting candidate to target genetic causes of motor neuron diseases like amyotrophic lateral sclerosis (ALS). However, systemic delivery risks immunogenicity and off-target effects, therefore localised delivery to the CNS is advantageous. We assessed MN transduction in wild-type post-natal mice using AAV9-controlled, cytomegalovirus-promoter driven, enhanced GFP expression. Intra-cisterna magna (ICM) and intra-cerebroventricular (ICV) methods were compared. Four weeks post-delivery, GFP positivity in MN and astrocytes were quantified via immunohistochemical approaches and viral genome copy number determined by qPCR. All delivery methods achieved high MN transduction in lumbar spinal cord (> 68%). Unilateral ICV delivery provided the highest and most consistent levels (89 ± 3%), and minimal peripheral viral copies. ICV delivery resulted in higher astrocytic transduction, most notably in the cortex. Brainstem MN transduction was high with all methods (> 55%). We failed to find evidence of neuronal transduction in motor cortex. Viral genome copies trended higher in spinal cord and brainstem with ICV approaches, however further work is required to understand how bilateral repeated dose delivery leads to more profound increases. Whilst several routes of administration into cerebrospinal fluid exist, direct comparisons for targeting MNs in vivo remain limited. Overall, all methods of CNS-directed delivery result in high levels of motor neuron transduction in the lumbar spinal cord and brainstem, but not in motor cortex. Unilateral ICV appears to provide the best balance between consistent, high levels of transduction and low off-target effects. However, ICM might be the better option if seeking to avoid astrocytic transduction.

Induced pluripotent stem cell (iPSC)-derived motor neurons (MNs) offer a promising model system for understanding motor neuron diseases (MNDs) and advancing drug discovery. However, variability in differentiation outcomes presents a major barrier to reproducibility and model reliability. This study evaluates a widely adopted small molecule protocol for MN differentiation to quantify variability and identify its sources within an industrial setting. Analysing data from 15 differentiation sets across 8 cell lines, we found that non-genetic factors – particularly induction set and operator – were the predominant sources of variability, outweighing the contribution from cell line genetics. We further demonstrated that iPSC genomic instability, as assessed by a targeted RT-qPCR assay for common karyotypic abnormalities, significantly affected differentiation efficiency and purity. Cultures derived from genomically stable iPSCs exhibited reduced variance and improved MN marker expression profiles. These findings support routine genomic assessment of iPSCs as a practical and effective strategy to enhance the reliability of iPSC-derived MN models, thereby improving their utility in preclinical MND research and therapeutic development.

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegenerative condition where loss of motor neurons within the brain and spinal cord leads to muscle atrophy, weakness, paralysis and ultimately death within 3–5 years from onset of symptoms. The specific molecular mechanisms underlying the disease pathology are not fully understood and neuroprotective treatment options are minimally effective. In recent years, stem cell transplantation as a new therapy for ALS patients has been extensively investigated, becoming an intense and debated field of study. In several preclinical studies using the SOD1 G93A mouse model of ALS, stem cells were demonstrated to be neuroprotective, effectively delayed disease onset and extended survival. Despite substantial improvements in stem cell technology and promising results in preclinical studies, several questions still remain unanswered, such as the identification of the most suitable and beneficial cell source, cell dose, route of delivery and therapeutic mechanisms. This review will cover publications in this field and comprehensively discuss advances, challenges and future direction regarding the therapeutic potential of stem cells in ALS, with a focus on mesenchymal stem cells. In summary, given their high proliferation activity, immunomodulation, multi-differentiation potential, and the capacity to secrete neuroprotective factors, adult mesenchymal stem cells represent a promising candidate for clinical translation. However, technical hurdles such as optimal dose, differentiation state, route of administration, and the underlying potential therapeutic mechanisms still need to be assessed.

GLP-1 receptor agonists used for the treatment of diabetes, have shown some neuroprotective effects in cellular and animal models of Alzheimer’s disease (AD) and Parkinson’s disease (PD). There are currently few studies investigating GLP-1 receptor agonists in the treatment of ALS, where these neuroprotective effects may be beneficial. Here we investigate the effects of liraglutide, a GLP-1 receptor agonist, in two well characterised transgenic mouse models of ALS (SOD1 G93A and TDP-43 Q331K ) to determine if liraglutide could be a potential treatment in ALS patients. Doses of liraglutide previously shown to have efficacy in AD and PD mouse models were used. Behavioural testing was carried out to ascertain the effect of liraglutide on disease progression. Immunohistochemical analysis of tissue was used to determine any neuroprotective effects on the CNS. We found that liraglutide dosed animals showed no significant differences in disease progression when compared to vehicle dosed animals in either the SOD1 G93A or TDP-43 Q331K mouse models of ALS. We also observed no changes in motor neuron counts or glial activation in lumbar spinal cords of liraglutide treated mice compared to vehicle dosed mice. Overall, we found no evidence to support clinical evaluation of liraglutide as a potential candidate for the treatment of ALS.

Amyotrophic lateral sclerosis (ALS) is a poorly treated multifactorial neurodegenerative disease associated with multiple cell types and subcellular organelles. As with other multifactorial diseases, it is likely that drugs will need to target multiple disease processes and cell types to be effective. We review here the role of Janus kinase (JAK)/Signal transducer and activator of transcription (STAT) signalling in ALS, confirm the association of this signalling with fundamental ALS disease processes using the BenevolentAI Knowledge Graph, and demonstrate that inhibitors of this pathway could reduce the ALS pathophysiology in neurons, glia, muscle fibres, and blood cells. Specifically, we suggest that inhibition of the JAK enzymes by approved inhibitors known as Jakinibs could reduce STAT3 activation and modify the progress of this disease. Analysis of the Jakinibs highlights baricitinib as a suitable candidate due to its ability to penetrate the central nervous system and exert beneficial effects on the immune system. Therefore, we recommend that this drug be tested in appropriately designed clinical trials for ALS.

Oxidative stress appears to be a key feature of many neurodegenerative diseases either as a cause or consequence of disease. A range of molecules are subject to oxidation, but in particular, proteins are an important target and measure of oxidative stress. Proteins are subject to a range of oxidative modifications at reactive cysteine residues, and depending on the level of oxidative stress, these modifications may be reversible or irreversible. A range of experimental approaches has been developed to characterize cysteine oxidation of proteins. In particular, mass spectrometry-based proteomic methods have emerged as a powerful means to identify and quantify cysteine oxidation sites on a proteome scale; however, their application to study neurodegenerative diseases is limited to date. Here we provide a guide to these approaches and highlight the under-exploited utility of these methods to measure oxidative stress in neurodegenerative diseases for biomarker discovery, target engagement and to understand disease mechanisms.

C9orf72-related amyotrophic lateral sclerosis (ALS)/frontotemporal dementia (FTD) has proven difficult to model in mice. Liu et al. (2016) reported a bacterial artificial chromosome (BAC) transgenic mouse displaying behavioural, motor and pathological abnormalities. This was followed by multiple laboratories independently refuting and confirming phenotypes. A proposed explanation centred on the use of different FVB background lines (from The Jackson Laboratory and Janvier Labs). We studied C9orf72 BAC mice on both backgrounds and found significantly elevated levels of dipeptide repeat proteins, but no evidence of a transgene-associated phenotype. We observed seizures and a gradual decline in functional performance in transgenic and non-transgenic mice, irrespective of genetic background. The phenotype was in keeping with the so-called ‘space cadet syndrome’. Our findings indicate that the differences previously reported are not due to C9orf72 status and highlight the importance of using genetic backgrounds that do not confound interpretation of neurodegenerative phenotypes.