RARE DISEASE
Alexander disease
Alexander disease
Alexander disease
Synonyms: AxD
Synonyms: AxD
Synonyms: AxD
Drug discovery
2
drugs
With orphan designations
Overview
Alexander disease is a rare, progressive leukodystrophy caused by dominant GFAP gene mutations, leading to astrocytic Rosenthal fibers and white matter degeneration. It manifests as infantile (most common), juvenile, or adult-onset forms, with symptoms including seizures, developmental regression, megalencephaly, swallowing difficulties, and spasticity. Diagnosis relies on MRI findings and genetic testing [1][5][6].
Burden
Infantile form: Median survival 14 years; adult-onset often progresses >25 years [7][9]
High care needs: 63% require feeding tubes; 47% develop scoliosis; 34% need respiratory support [7][9][13]
Economic impact: Chronic hospitalization, specialized equipment, and lost caregiver productivity [5][7][13]
Therapies
Symptomatic management: Antiseizure drugs (e.g., valproic acid, 95% effective for vomiting [3]), reflux medications, nutritional support [5][7][9]
Emerging therapies: Antisense oligonucleotides (ION373) reduce GFAP expression in trials, showing symptom reversal in preclinical models [11][14][19]
Supportive care: Multidisciplinary PT/OT/speech therapy, feeding tubes, and scoliosis/respiratory interventions [5][7][9]
Categories: rare genetic diseases, rare neurological diseases
Research Papers
106 drug discovery papers about Alexander disease, with 2 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
106 drug discovery papers about Alexander disease, with 2 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
gene therapies
2024-09-25 | Gene therapy for the leukodystrophies: From preclinical animal studies to clinical trials.
Leukodystrophies are progressive single gene disorders affecting the white matter of the brain. Several gene therapy trials are in progress to address the urgent unmet need for this patient population. We performed a comprehensive literature review of all gene therapy clinical trials listed in www.clinicaltrials.gov through August 2024, and the relevant preclinical studies that enabled clinical translation. Of the approximately 50 leukodystrophies described to date, only eight have existing gene therapy clinical trials: metachromatic leukodystrophy, X-linked adrenoleukodystrophy, globoid cell leukodystrophy, Canavan disease, giant axonal neuropathy, GM2 gangliosidoses, Alexander disease and Pelizaeus-Merzbacher disease. What led to the emergence of gene therapy trials for these specific disorders? What preclinical data or disease context was enabling? For each of these eight disorders, we first describe its pathophysiology and clinical presentation. We discuss the impact of gene therapy delivery route, targeted cell type, delivery modality, dosage, and timing on therapeutic efficacy. We note that use of allogeneic hematopoietic stem cell transplantation in some leukodystrophies allowed for an accelerated path to clinic even in the absence of available animal models. In other leukodystrophies, small and large animal model studies enabled clinical translation of experimental gene therapies. Human clinical trials for the leukodystrophies include ex vivo lentiviral gene delivery, in vivo AAV-mediated gene delivery, and intrathecal antisense oligonucleotide approaches. We outline adverse events associated with each modality focusing specifically on genotoxicity and immunotoxicity. We review monitoring and management of events related to insertional mutagenesis and immune responses. The data presented in this review show that gene therapy, while promising, requires systematic monitoring to account for the precarious disease biology and the adverse events associated with new technology.
2006-04-19 | Plectin regulates the organization of glial fibrillary acidic protein in Alexander disease.
Alexander disease (AxD) is a rare but fatal neurological disorder caused by mutations in the astrocyte-specific intermediate filament protein glial fibrillary acidic protein (GFAP). Histologically, AxD is characterized by cytoplasmic inclusion bodies called Rosenthal fibers (RFs), which contain GFAP, small heat shock proteins, and other undefined components. Here, we describe the expression of the cytoskeletal linker protein plectin in the AxD brain. RFs displayed positive immunostaining for plectin and GFAP, both of which were increased in the AxD brain. Co-localization, co-immunoprecipitation, and in vitro overlay analyses demonstrated direct interaction of plectin and GFAP. GFAP with the most common AxD mutation, R239C (RC GFAP), mainly formed abnormal aggregates in human primary astrocytes and murine plectin-deficient fibroblasts. Transient transfection of full-length plectin cDNA converted these aggregates to thin filaments, which exhibited diffuse cytoplasmic distribution. Compared to wild-type GFAP expression, RC GFAP expression lowered plectin levels in astrocytoma-derived stable transfectants and plectin-positive fibroblasts. A much higher proportion of total GFAP was found in the Triton X-insoluble fraction of plectin-deficient fibroblasts than in wild-type fibroblasts. Taken together, our results suggest that insufficient amounts of plectin, due to RC GFAP expression, promote GFAP aggregation and RF formation in AxD.
1999-05-01 | Formation of GFAP Cytoplasmic Inclusions in Astrocytes and Their Disaggregation by αB-Crystallin
In several neuropathological conditions, alphaB-crystallin and glial fibrillary acidic protein (GFAP) accumulate and form cytoplasmic inclusions in astrocytes. To explore the pathogenesis of the inclusions and the possible functions of the accumulated alphaB-crystallin, GFAP and alphaB-crystallin were overexpressed in cultured astrocytes by transient transfection. Human GFAP formed filamentous, cytoplasmic inclusions in mouse astrocytes, NIH3T3 cells, rat C6 glioma cells, and human U251 glioma cells. These human GFAP inclusions did not contain the endogenous vimentin or beta-tubulin, and the intermediate filament and microtubular networks of the transfected cells appeared normal. alphaB-crystallin and hsp25 were associated with the GFAP inclusions. Increasing intracellular alphaB-crystallin levels using recombinant adenoviruses, either before or after GFAP inclusions were formed, decreased the number of inclusion-bearing astrocytes and converted the human GFAP from an inclusion to a spread, filamentous form. These results suggest that alphaB-crystallin reorganizes abnormal intermediate filament aggregates into the normal filamentous network.
small molecules
2025-12-15 | Experimental Approaches for Biochemical Analysis of Glial Fibrillary Acidic Protein and Its Disease-associated Variants.
Glial Fibrillary Acidic Protein (GFAP) is a key intermediate filament protein critical for maintaining the structural integrity and function of astrocytes in the central nervous system. Mutations in GFAP are the root cause of Alexander disease (AxD), a rare and often fatal neurodegenerative disorder characterized by elevation of GFAP levels and accumulation of GFAP in the form of Rosenthal fibers. Here, we outline a comprehensive set of experimental approaches for the biochemical characterization of GFAP and its disease-causing variants. Using optimized expression and advanced purification techniques, we achieved high yields and purity of both wild-type and mutant GFAP proteins. Biochemical assays were employed to evaluate the effects of pathogenic mutations on filament assembly, solubility, and aggregation. Additionally, we explored the role of aberrant posttranslational modifications in GFAP aggregation and their impact on filament properties. This work advances our understanding of GFAP's role in AxD and lays a foundation for developing therapeutic strategies targeting GFAP dysfunction. Furthermore, the methodologies presented here serve as valuable tools for investigating the biochemical consequences of GFAP mutations and advancing interventions for GFAP-related disorders.
2025-09-29 | Description of the Hamburg Alexander Leukodystrophy Cohort—Insights into Practical Classification and the Care Situation
Background: Alexander disease (AxD) is a rare severe leukodystrophy that has no cure to date. A pathogenic gain-of-function variant in the GFAP gene affects the astrocytes and subsequently the function of the white matter in the CNS. Methods: We retrospectively analyzed the most frequent symptoms of nine AxD cases, classified them according to published classifications, and described the need of care and support. Results: The description of the courses of disease of nine cases with AxD reflects the broad spectrum of different phenotypes of AxD, with often occurring apnoea. Data about care and support for AxD patients indicate a high and heterogeneous need of support. Treatment with steroids reduced symptoms in two patients. Some patients showed lasting improvement during their course of disease. Conclusions: The course of AxD is very heterogeneous. Thus, we extracted relevant key features to describe the severity of the disease, namely feeding problems, epilepsy, age-appropriate motor function, failure to thrive, age-appropriate language and apnoea. We recommend early evaluation for clinical care and support. For some AxD patients, treatment with steroids may alleviate symptoms. Further development of efficient treatments is necessary.
2025-08-22 | Targeting astrocytic CLC2(CLCN2) restores myelin regeneration through inhibition of SPP1/CD44 signaling pathway in leukoencephalopathy.
Accumulating myelin damage and impaired remyelination are central pathological features of leukoencephalopathies, including Multiple Sclerosis and Alexander Disease, where astrocytes play essential roles in maintaining central nervous system homeostasis and mediating astrocyte-oligodendrocyte interactions. Chloride Ion Channel 2 (ClC-2), encoded by CLCN2, is functionally expressed in astrocytes and is likely critical to white matter integrity; however, its precise roles and interactions remain unclear. Clarifying the mechanisms by which astrocytic ClC-2 influences white matter is essential for developing treatments for CLCN2-related leukoencephalopathy (CC2L) and potentially other white matter disorders. In this study, we demonstrate that dysfunctional ClC-2 in astrocytes-derived from both mouse models and human-induced pluripotent stem cells (hiPSCs)-impairs oligodendrocyte lineage cell development in vitro and delays remyelination in vivo. Transcriptomic analyses identified SPP1 as a key inhibitory factor on remyelination, secreted from ClC-2-deficient astrocytes. This inhibition was validated through astrocyte-specific modulation of SPP1 expression, where overexpression exacerbated, and downregulation alleviated, demyelination effects. Furthermore, we discovered that SPP1 upregulation in astrocytes with abnormal ClC-2 negatively impacts remyelination by interacting with CD44 on oligodendrocyte progenitor cells. Finally, we confirmed that increased SPP1 expression and the resulting suppression of oligodendrocyte lineage cell development were also present in hiPSC-derived astrocytes harboring a CLCN2 mutation from a CC2L patient. Collectively, these findings reveal that astrocytic ClC-2 is intricately linked to white matter integrity through SPP1 regulation, positioning it as a potential therapeutic target for CC2L and other leukoencephalopathies.
2025-05-28 | Prevalence of Elevated Opening Pressure Measurements in Alexander Disease.
Alexander disease (AxD) is caused by a gain-of-function mutation in GFAP resulting in the formation of Rosenthal fibers, which are hypothesized to impair cerebrospinal fluid circulation, potentially resulting in increased ICP. We explored the prevalence of elevated intracranial pressure (ICP) in AxD. Patients with AxD underwent a neurological examination, lumbar puncture (LP) with opening pressure (OP) with legs flexed, and brain magnetic resonance imaging (MRI). Elevated OP was defined as >28 cm H2O. A neuroradiologist (masked to clinical data and OP) reviewed MRIs for imaging signs of elevated ICP (flattened posterior sclerae, enlarged optic nerve sheaths, partially empty sella, and dural sinus venous stenoses). Descriptive statistics included proportions of patients with elevated OP and MRI findings. Mixed effects logistic regression was used to explore associations with elevated OP. Sixty-nine LPs were performed in 43 patients; 21 (49%) patients had an elevated OP on at least one LP. Papilledema was not present among those with a concurrent undilated funduscopic examination. Although most patients were asymptomatic, two patients received acetazolamide for headache and vomiting with symptom benefit and reduced OP. There was no association between age and OP (P = 0.11). MRI features of increased ICP were primarily observed in those with elevated OP. Elevated OP with legs flexed and MRI features of increased ICP occur frequently in AxD, even in the absence of overt clinical signs. The implications of increased ICP on patient outcomes and whether asymptomatic elevated OP requires treatment need to be determined in AxD.
2025-05-07 | Bilateral vestibulopathy in Alexander disease type II- a case report.
Alexander disease (AxD) is rare leukodystrophy caused by a mutation in the glial fibrillary acidic protein (GFAP) gene. Astrocyte dysfunction leads to myelinization disturbances and white matter damage, resulting in distinct neurological symptoms and neuroradiological findings. Our patient, a 46-year old male, showed typical symptoms of AxD, including myoclonus of the soft palate, nystagmus, and cerebellar ataxia, as well as typical radiological findings found in AxD. The results of a device-based vestibular examination, including a video head-impulse test, showed a bilaterally decreased gain of vestibulo-ocular reflex of all semicircular canals suggestive of a bilateral vestibulopathy (BVP), a novel aspect of AxD. Symptomatic treatment of cerebellar ataxia and BVP with 4-aminopyridine (4-AP) led to an improvement of several device-examined vestibular parameters, but without subjective improvements in balance. This case report describes BVP in a patient suffering from AxD, a novel phenotype of the disease. In leukodystrophies, such as AxD, central vestibular symptoms should be assessed early on to evaluate the potential use of 4-AP.
cell therapies
2025-08-01 | 543. MODULATION OF BRAIN FUNCTIONS BY GLIAL RESET
Abstract Background Microglia actively regulate brain function through synaptic and neural network remodeling. Abnormalities in microglia modulate the regulation of these neurons and contribute to the etiology of psychiatric and neurodegenerative diseases. Therefore, we developed a strategy to replace microglia by resetting or transplanting microglia as a therapeutic strategy for these diseases and tested its therapeutic efficacy. Aims & Objectives The aim of of this study is to elucidate the impact of microglial replacement on the pathogenesis of animal models of disease. The objectives are: 1) to develop an accurate microglial replacement method, 2) to demonstrate in animal models that microglial replacement can be a therapeutic strategy for various brain diseases, and 3) to elucidate the molecular mechanisms of the therapeutic effects of microglial replacement. Method Microglia require colony stimulating factor 1 receptor (CSF1R) signaling for survival. We used two of microglia replacement methods: microglia removal/regeneration by turning CSF1R antagonists ON and OFF (reset) and microglia transplantation. The effects of microglial replacement were analyzed molecularly, biochemically, and behaviorally using mainly the Alexander disease (AxD) model. Results Microglial reset was enabled by turning ON/OFF of CSF1R antagonists (PLX5622 or PLX3397). Microglial transplantation was also possible by combining reset with tranasal microglial transplantation. In experiments with AxD model mice, removal of microglia exacerbated the disease, but reset of microglia improved the disease. Thus, it was shown that microglia have a protective effect against AxD pathology and that the effect is enhanced by replacement. RNA sequencing analysis revealed that the expression of various inflammatory molecules is upregulated in the AxD brain, and that microglial replacement dramatically suppresses these inflammatory effects. The effects of microglial replacement on mouse models of autism will also be reported. Discussion & Conclusions Microglia can be easily, safely, and reproducibly replaced by turning ON/OFF of CSF1R antagonists (Reset) and by microglia transplantation combined with the Reset and microglia intranasal transplantation. Microglial abnormalities have been observed in the brains of various animal models of brain diseases. Removal of these microglia alone does not necessarily result in improvement of the disease state. This is because microglia are heterogenous and play not only toxic but also beneficial roles. In fact, the replacement of microglia and restoring them to normality improved the disease state. Thus, microglial replacement may be a therapeutic strategy for various brain diseases, including the AxD model. In the case of the AxD model, the molecular mechanism of the therapeutic effect of microglia replacement was found to be mainly the inhibition of neuroinflammation.
2023-08-11 | A defined roadmap of radial glia and astrocyte differentiation from human pluripotent stem cells.
Human gliogenesis remains poorly understood, and derivation of astrocytes from human pluripotent stem cells (hPSCs) is inefficient and cumbersome. Here, we report controlled glial differentiation from hPSCs that bypasses neurogenesis, which otherwise precedes astrogliogenesis during brain development and in vitro differentiation. hPSCs were first differentiated into radial glial cells (RGCs) resembling resident RGCs of the fetal telencephalon, and modulation of specific cell signaling pathways resulted in direct and stepwise induction of key astroglial markers (NFIA, NFIB, SOX9, CD44, S100B, glial fibrillary acidic protein [GFAP]). Transcriptomic and genome-wide epigenetic mapping and single-cell analysis confirmed RGC-to-astrocyte differentiation, obviating neurogenesis and the gliogenic switch. Detailed molecular and cellular characterization experiments uncovered new mechanisms and markers for human RGCs and astrocytes. In summary, establishment of a glia-exclusive neural lineage progression model serves as a unique serum-free platform of manufacturing large numbers of RGCs and astrocytes for neuroscience, disease modeling (e.g., Alexander disease), and regenerative medicine.
2018-06-15 | Emerging Cellular and Molecular Strategies for Enhancing Central Nervous System (CNS) Remyelination
Myelination is critical for the normal functioning of the central nervous system (CNS) in vertebrates. Conditions in which the development of myelin is perturbed result in severely compromised individuals often with shorter lifespans, while loss of myelin in the adult results in a variety of functional deficits. Although some form of spontaneous remyelination often takes place, the repair process as a whole often fails. Several lines of evidence suggest it is feasible to develop strategies that enhance the capacity of the CNS to undergo remyelination and potentially reverse functional deficits. Such strategies include cellular therapies using either neural or mesenchymal stem cells as well as molecular regulators of oligodendrocyte development and differentiation. Given the prevalence of demyelinating diseases and their effects on the quality of life for affected individuals it is imperative that effective therapies are developed. Here we discuss some of the new approaches to CNS myelin repair that hold promise for reducing the burden of diseases characterized by myelin loss.
oligonucleotides
2026-05-13 | Industry Insights: Regulatory progress and AI-driven advances in nucleic acid therapeutics
Across March and April 2026, activity in the nucleic acid therapeutics field reflected broad regulatory momentum and continued clinical advancement across multiple RNA modalities. Regulatory highlights included US FDA Priority Review designations for Ionis' antisense oligonucleotide (ASO) zilganersen in Alexander disease, alongside EMA acceptance of GSK's marketing authorisation application for the ASO bepirovirsen in chronic hepatitis B. Clinical milestones featured first-in-human trials of novel modalities, including Alltrna's transfer RNA therapeutic AP003 and AIRNA's RNA-editing candidate AIR-001. AI-driven discovery also advanced, with Asimov launching an integrated RNA optimisation platform and ProQR partnering with Ginkgo Bioworks to scale high-throughput data generation for its RNA editing pipeline.
2026-03-04 | From scaffold to effector: reframing GFAP in neurodegeneration.
Neurodegenerative disorders impose a growing global burden, yet disease-modifying therapies remain limited. Glial fibrillary acidic protein (GFAP) has shifted from a passive astrocytic marker to an active effector that shapes neurodegenerative pathology. of Review: This review synthesizes mechanistic and translational evidence that defines GFAP as a proteoform-governed hub and highlights its value for biomarker-guided precision intervention. Key Scientific Concepts of Review: An extensive literature search across major databases was conducted using predefined keywords and strict inclusion criteria, covering mechanistic, pathological, and clinical studies. Evidence supports a GFAP proteoform code in which alternative splicing generates functionally distinct isoforms, and PTMs encode context-dependent assembly dynamics and signaling outputs. We summarize how GFAP proteoforms integrate cytoskeletal remodeling with inflammatory transcriptional programs (notably STAT3 and NF-κB), proteostasis stress, and mitochondrial dysfunction, thereby coupling astrocyte state transitions to neuronal vulnerability and synaptic impairment. Disease trajectories are context-specific: GFAP dysfunction drives primary toxicity in Alexander disease (AxD); in Alzheimer's disease (AD), isoform-specific mechanisms intersect with amyloidogenic machinery and track early preclinical astrocyte activation; and in frontotemporal dementia (FTD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), GFAP reflects inflammatory-metabolic coupling during progression. Translationally, ultrasensitive plasma assays reveal GFAP elevation years to decades before symptom onset, complementing NfL and amyloid/tau within AT(N)-oriented diagnostic frameworks. Therapeutically, we evaluate precision strategies beyond global suppression, including ASO-based modulation, targeting STAT3/NF-κB-driven reactive programs, and restoring proteostasis via chaperone/autophagy pathways. Future progress hinges on isoform-/PTM-specific probes, conformational sensors, and spatial proteomic atlases validated in prospective longitudinal cohorts. In conclusion, GFAP represents both a mechanistic driver and a scalable biomarker, offering a translationally actionable axis to advance precision medicine in neurodegeneration.
2023-11-30 | Alexander Disease: Scientific Advancement and Therapeutic Intervention in Rare Disease Research
Alexander Disease (AxD) is a rare, heritable white matter condition, or leukodystrophy, that helps to understand how collaborative, translational research can identify therapeutic options in a complex illness. AxD is a rare disease, first described in 1949, that affects approximately one in 2.7 million births. The disease hinders the function of the central nervous system (CNS) through the biotoxic overproduction of protein aggregates which cause the deterioration of the myelin sheath. Given the extreme rarity of AxD, disease-specific research is relatively limited, and there is no disease-modifying treatment currently available. At present, a clinical trial is underway to examine the safety and efficacy of Ionis Pharmaceuticals’ ION373, an Antisense Oligonucleotide (ASO), that has reported success in preventing the progression of AxD in mouse models. This paper reviews the key components of AxD, therapeutic designs for AxD, and ultimately suggests future directions to optimize the therapeutic approach. This review also aims to promote rare disease awareness, as scientific progress for conditions like Alexander Disease is achieved through advocacy and promotion.
2021-06-14 | NG2 and GFAP co-expression after differentiation in cells transfected with mutant GFAP and in undifferentiated glioma cells.
Alexander disease is a rare disorder caused by mutations in the gene coding for glial fibrillary acidic protein (GFAP). In a previous study, differentiation of neurospheres transfected with these mutations resulted in a cell type that expresses both GFAP and NG2. To determine the effect of molecular marker mutations in comparison to undifferentiated glioma cells simultaneously expressing GFAP and NG2. We used samples of human glioblastoma (GBM) and rat neurospheres transfected with GFAP mutations to analyse GFAP and NG2 expression after differentiation. We also performed an immunocytochemical analysis of neuronal differentiation for both cell types and detection of GFAP, NG2, vimentin, Olig2, and caspase-3 at 3 and 7 days from differentiation. Both the cells transfected with GFAP mutations and GBM cells showed increased NG2 and GFAP expression. However, expression of caspase-3-positive cells was found to be considerably higher in transfected cells than in GBM cells. Our results suggest that GFAP expression is not the only factor associated with cell death in Alexander disease. Caspase-3 expression and the potential role of NG2 in increasing resistance to apoptosis in cells co-expressing GFAP and NG2 should be considered in the search for new therapeutic strategies for the disease.
2020-10-13 | [Clinical characteristics and diagnostic criteria on Alexander disease].
Alexander disease (ALXDRD) is a primary astrocyte disease caused by glial fibrillary acidic protein (GFAP) gene mutation. ALXDRD had been clinically regarded as a cerebral white matter disease that affects only children for about 50 years since the initial report in 1949; however, in the early part of the 21st century, case reports of adult-onset ALXDRD with medulla and spinal cord lesions increased. Basic research on therapies to reduce abnormal GFAP accumulation, such as drug-repositioning and antisense oligonucleotide suppression, has recently been published. The accumulation of clinical data to advance understanding of natural history is essential for clinical trials expected in the future. In this review, I classified ALXDRD into two subtypes: early-onset and late-onset, and detail the clinical symptoms, imaging findings, and genetic characteristics as well as the epidemiology and historical changes in the clinical classification described in the literature. The diagnostic criteria based on Japanese ALXDRD patients that are useful in daily clinical practice are also mentioned.
gene therapies
2024-09-25 | Gene therapy for the leukodystrophies: From preclinical animal studies to clinical trials.
Leukodystrophies are progressive single gene disorders affecting the white matter of the brain. Several gene therapy trials are in progress to address the urgent unmet need for this patient population. We performed a comprehensive literature review of all gene therapy clinical trials listed in www.clinicaltrials.gov through August 2024, and the relevant preclinical studies that enabled clinical translation. Of the approximately 50 leukodystrophies described to date, only eight have existing gene therapy clinical trials: metachromatic leukodystrophy, X-linked adrenoleukodystrophy, globoid cell leukodystrophy, Canavan disease, giant axonal neuropathy, GM2 gangliosidoses, Alexander disease and Pelizaeus-Merzbacher disease. What led to the emergence of gene therapy trials for these specific disorders? What preclinical data or disease context was enabling? For each of these eight disorders, we first describe its pathophysiology and clinical presentation. We discuss the impact of gene therapy delivery route, targeted cell type, delivery modality, dosage, and timing on therapeutic efficacy. We note that use of allogeneic hematopoietic stem cell transplantation in some leukodystrophies allowed for an accelerated path to clinic even in the absence of available animal models. In other leukodystrophies, small and large animal model studies enabled clinical translation of experimental gene therapies. Human clinical trials for the leukodystrophies include ex vivo lentiviral gene delivery, in vivo AAV-mediated gene delivery, and intrathecal antisense oligonucleotide approaches. We outline adverse events associated with each modality focusing specifically on genotoxicity and immunotoxicity. We review monitoring and management of events related to insertional mutagenesis and immune responses. The data presented in this review show that gene therapy, while promising, requires systematic monitoring to account for the precarious disease biology and the adverse events associated with new technology.
2006-04-19 | Plectin regulates the organization of glial fibrillary acidic protein in Alexander disease.
Alexander disease (AxD) is a rare but fatal neurological disorder caused by mutations in the astrocyte-specific intermediate filament protein glial fibrillary acidic protein (GFAP). Histologically, AxD is characterized by cytoplasmic inclusion bodies called Rosenthal fibers (RFs), which contain GFAP, small heat shock proteins, and other undefined components. Here, we describe the expression of the cytoskeletal linker protein plectin in the AxD brain. RFs displayed positive immunostaining for plectin and GFAP, both of which were increased in the AxD brain. Co-localization, co-immunoprecipitation, and in vitro overlay analyses demonstrated direct interaction of plectin and GFAP. GFAP with the most common AxD mutation, R239C (RC GFAP), mainly formed abnormal aggregates in human primary astrocytes and murine plectin-deficient fibroblasts. Transient transfection of full-length plectin cDNA converted these aggregates to thin filaments, which exhibited diffuse cytoplasmic distribution. Compared to wild-type GFAP expression, RC GFAP expression lowered plectin levels in astrocytoma-derived stable transfectants and plectin-positive fibroblasts. A much higher proportion of total GFAP was found in the Triton X-insoluble fraction of plectin-deficient fibroblasts than in wild-type fibroblasts. Taken together, our results suggest that insufficient amounts of plectin, due to RC GFAP expression, promote GFAP aggregation and RF formation in AxD.
1999-05-01 | Formation of GFAP Cytoplasmic Inclusions in Astrocytes and Their Disaggregation by αB-Crystallin
In several neuropathological conditions, alphaB-crystallin and glial fibrillary acidic protein (GFAP) accumulate and form cytoplasmic inclusions in astrocytes. To explore the pathogenesis of the inclusions and the possible functions of the accumulated alphaB-crystallin, GFAP and alphaB-crystallin were overexpressed in cultured astrocytes by transient transfection. Human GFAP formed filamentous, cytoplasmic inclusions in mouse astrocytes, NIH3T3 cells, rat C6 glioma cells, and human U251 glioma cells. These human GFAP inclusions did not contain the endogenous vimentin or beta-tubulin, and the intermediate filament and microtubular networks of the transfected cells appeared normal. alphaB-crystallin and hsp25 were associated with the GFAP inclusions. Increasing intracellular alphaB-crystallin levels using recombinant adenoviruses, either before or after GFAP inclusions were formed, decreased the number of inclusion-bearing astrocytes and converted the human GFAP from an inclusion to a spread, filamentous form. These results suggest that alphaB-crystallin reorganizes abnormal intermediate filament aggregates into the normal filamentous network.
small molecules
2025-12-15 | Experimental Approaches for Biochemical Analysis of Glial Fibrillary Acidic Protein and Its Disease-associated Variants.
Glial Fibrillary Acidic Protein (GFAP) is a key intermediate filament protein critical for maintaining the structural integrity and function of astrocytes in the central nervous system. Mutations in GFAP are the root cause of Alexander disease (AxD), a rare and often fatal neurodegenerative disorder characterized by elevation of GFAP levels and accumulation of GFAP in the form of Rosenthal fibers. Here, we outline a comprehensive set of experimental approaches for the biochemical characterization of GFAP and its disease-causing variants. Using optimized expression and advanced purification techniques, we achieved high yields and purity of both wild-type and mutant GFAP proteins. Biochemical assays were employed to evaluate the effects of pathogenic mutations on filament assembly, solubility, and aggregation. Additionally, we explored the role of aberrant posttranslational modifications in GFAP aggregation and their impact on filament properties. This work advances our understanding of GFAP's role in AxD and lays a foundation for developing therapeutic strategies targeting GFAP dysfunction. Furthermore, the methodologies presented here serve as valuable tools for investigating the biochemical consequences of GFAP mutations and advancing interventions for GFAP-related disorders.
2025-09-29 | Description of the Hamburg Alexander Leukodystrophy Cohort—Insights into Practical Classification and the Care Situation
Background: Alexander disease (AxD) is a rare severe leukodystrophy that has no cure to date. A pathogenic gain-of-function variant in the GFAP gene affects the astrocytes and subsequently the function of the white matter in the CNS. Methods: We retrospectively analyzed the most frequent symptoms of nine AxD cases, classified them according to published classifications, and described the need of care and support. Results: The description of the courses of disease of nine cases with AxD reflects the broad spectrum of different phenotypes of AxD, with often occurring apnoea. Data about care and support for AxD patients indicate a high and heterogeneous need of support. Treatment with steroids reduced symptoms in two patients. Some patients showed lasting improvement during their course of disease. Conclusions: The course of AxD is very heterogeneous. Thus, we extracted relevant key features to describe the severity of the disease, namely feeding problems, epilepsy, age-appropriate motor function, failure to thrive, age-appropriate language and apnoea. We recommend early evaluation for clinical care and support. For some AxD patients, treatment with steroids may alleviate symptoms. Further development of efficient treatments is necessary.
2025-08-22 | Targeting astrocytic CLC2(CLCN2) restores myelin regeneration through inhibition of SPP1/CD44 signaling pathway in leukoencephalopathy.
Accumulating myelin damage and impaired remyelination are central pathological features of leukoencephalopathies, including Multiple Sclerosis and Alexander Disease, where astrocytes play essential roles in maintaining central nervous system homeostasis and mediating astrocyte-oligodendrocyte interactions. Chloride Ion Channel 2 (ClC-2), encoded by CLCN2, is functionally expressed in astrocytes and is likely critical to white matter integrity; however, its precise roles and interactions remain unclear. Clarifying the mechanisms by which astrocytic ClC-2 influences white matter is essential for developing treatments for CLCN2-related leukoencephalopathy (CC2L) and potentially other white matter disorders. In this study, we demonstrate that dysfunctional ClC-2 in astrocytes-derived from both mouse models and human-induced pluripotent stem cells (hiPSCs)-impairs oligodendrocyte lineage cell development in vitro and delays remyelination in vivo. Transcriptomic analyses identified SPP1 as a key inhibitory factor on remyelination, secreted from ClC-2-deficient astrocytes. This inhibition was validated through astrocyte-specific modulation of SPP1 expression, where overexpression exacerbated, and downregulation alleviated, demyelination effects. Furthermore, we discovered that SPP1 upregulation in astrocytes with abnormal ClC-2 negatively impacts remyelination by interacting with CD44 on oligodendrocyte progenitor cells. Finally, we confirmed that increased SPP1 expression and the resulting suppression of oligodendrocyte lineage cell development were also present in hiPSC-derived astrocytes harboring a CLCN2 mutation from a CC2L patient. Collectively, these findings reveal that astrocytic ClC-2 is intricately linked to white matter integrity through SPP1 regulation, positioning it as a potential therapeutic target for CC2L and other leukoencephalopathies.
2025-05-28 | Prevalence of Elevated Opening Pressure Measurements in Alexander Disease.
Alexander disease (AxD) is caused by a gain-of-function mutation in GFAP resulting in the formation of Rosenthal fibers, which are hypothesized to impair cerebrospinal fluid circulation, potentially resulting in increased ICP. We explored the prevalence of elevated intracranial pressure (ICP) in AxD. Patients with AxD underwent a neurological examination, lumbar puncture (LP) with opening pressure (OP) with legs flexed, and brain magnetic resonance imaging (MRI). Elevated OP was defined as >28 cm H2O. A neuroradiologist (masked to clinical data and OP) reviewed MRIs for imaging signs of elevated ICP (flattened posterior sclerae, enlarged optic nerve sheaths, partially empty sella, and dural sinus venous stenoses). Descriptive statistics included proportions of patients with elevated OP and MRI findings. Mixed effects logistic regression was used to explore associations with elevated OP. Sixty-nine LPs were performed in 43 patients; 21 (49%) patients had an elevated OP on at least one LP. Papilledema was not present among those with a concurrent undilated funduscopic examination. Although most patients were asymptomatic, two patients received acetazolamide for headache and vomiting with symptom benefit and reduced OP. There was no association between age and OP (P = 0.11). MRI features of increased ICP were primarily observed in those with elevated OP. Elevated OP with legs flexed and MRI features of increased ICP occur frequently in AxD, even in the absence of overt clinical signs. The implications of increased ICP on patient outcomes and whether asymptomatic elevated OP requires treatment need to be determined in AxD.
2025-05-07 | Bilateral vestibulopathy in Alexander disease type II- a case report.
Alexander disease (AxD) is rare leukodystrophy caused by a mutation in the glial fibrillary acidic protein (GFAP) gene. Astrocyte dysfunction leads to myelinization disturbances and white matter damage, resulting in distinct neurological symptoms and neuroradiological findings. Our patient, a 46-year old male, showed typical symptoms of AxD, including myoclonus of the soft palate, nystagmus, and cerebellar ataxia, as well as typical radiological findings found in AxD. The results of a device-based vestibular examination, including a video head-impulse test, showed a bilaterally decreased gain of vestibulo-ocular reflex of all semicircular canals suggestive of a bilateral vestibulopathy (BVP), a novel aspect of AxD. Symptomatic treatment of cerebellar ataxia and BVP with 4-aminopyridine (4-AP) led to an improvement of several device-examined vestibular parameters, but without subjective improvements in balance. This case report describes BVP in a patient suffering from AxD, a novel phenotype of the disease. In leukodystrophies, such as AxD, central vestibular symptoms should be assessed early on to evaluate the potential use of 4-AP.
cell therapies
2025-08-01 | 543. MODULATION OF BRAIN FUNCTIONS BY GLIAL RESET
Abstract Background Microglia actively regulate brain function through synaptic and neural network remodeling. Abnormalities in microglia modulate the regulation of these neurons and contribute to the etiology of psychiatric and neurodegenerative diseases. Therefore, we developed a strategy to replace microglia by resetting or transplanting microglia as a therapeutic strategy for these diseases and tested its therapeutic efficacy. Aims & Objectives The aim of of this study is to elucidate the impact of microglial replacement on the pathogenesis of animal models of disease. The objectives are: 1) to develop an accurate microglial replacement method, 2) to demonstrate in animal models that microglial replacement can be a therapeutic strategy for various brain diseases, and 3) to elucidate the molecular mechanisms of the therapeutic effects of microglial replacement. Method Microglia require colony stimulating factor 1 receptor (CSF1R) signaling for survival. We used two of microglia replacement methods: microglia removal/regeneration by turning CSF1R antagonists ON and OFF (reset) and microglia transplantation. The effects of microglial replacement were analyzed molecularly, biochemically, and behaviorally using mainly the Alexander disease (AxD) model. Results Microglial reset was enabled by turning ON/OFF of CSF1R antagonists (PLX5622 or PLX3397). Microglial transplantation was also possible by combining reset with tranasal microglial transplantation. In experiments with AxD model mice, removal of microglia exacerbated the disease, but reset of microglia improved the disease. Thus, it was shown that microglia have a protective effect against AxD pathology and that the effect is enhanced by replacement. RNA sequencing analysis revealed that the expression of various inflammatory molecules is upregulated in the AxD brain, and that microglial replacement dramatically suppresses these inflammatory effects. The effects of microglial replacement on mouse models of autism will also be reported. Discussion & Conclusions Microglia can be easily, safely, and reproducibly replaced by turning ON/OFF of CSF1R antagonists (Reset) and by microglia transplantation combined with the Reset and microglia intranasal transplantation. Microglial abnormalities have been observed in the brains of various animal models of brain diseases. Removal of these microglia alone does not necessarily result in improvement of the disease state. This is because microglia are heterogenous and play not only toxic but also beneficial roles. In fact, the replacement of microglia and restoring them to normality improved the disease state. Thus, microglial replacement may be a therapeutic strategy for various brain diseases, including the AxD model. In the case of the AxD model, the molecular mechanism of the therapeutic effect of microglia replacement was found to be mainly the inhibition of neuroinflammation.
2023-08-11 | A defined roadmap of radial glia and astrocyte differentiation from human pluripotent stem cells.
Human gliogenesis remains poorly understood, and derivation of astrocytes from human pluripotent stem cells (hPSCs) is inefficient and cumbersome. Here, we report controlled glial differentiation from hPSCs that bypasses neurogenesis, which otherwise precedes astrogliogenesis during brain development and in vitro differentiation. hPSCs were first differentiated into radial glial cells (RGCs) resembling resident RGCs of the fetal telencephalon, and modulation of specific cell signaling pathways resulted in direct and stepwise induction of key astroglial markers (NFIA, NFIB, SOX9, CD44, S100B, glial fibrillary acidic protein [GFAP]). Transcriptomic and genome-wide epigenetic mapping and single-cell analysis confirmed RGC-to-astrocyte differentiation, obviating neurogenesis and the gliogenic switch. Detailed molecular and cellular characterization experiments uncovered new mechanisms and markers for human RGCs and astrocytes. In summary, establishment of a glia-exclusive neural lineage progression model serves as a unique serum-free platform of manufacturing large numbers of RGCs and astrocytes for neuroscience, disease modeling (e.g., Alexander disease), and regenerative medicine.
2018-06-15 | Emerging Cellular and Molecular Strategies for Enhancing Central Nervous System (CNS) Remyelination
Myelination is critical for the normal functioning of the central nervous system (CNS) in vertebrates. Conditions in which the development of myelin is perturbed result in severely compromised individuals often with shorter lifespans, while loss of myelin in the adult results in a variety of functional deficits. Although some form of spontaneous remyelination often takes place, the repair process as a whole often fails. Several lines of evidence suggest it is feasible to develop strategies that enhance the capacity of the CNS to undergo remyelination and potentially reverse functional deficits. Such strategies include cellular therapies using either neural or mesenchymal stem cells as well as molecular regulators of oligodendrocyte development and differentiation. Given the prevalence of demyelinating diseases and their effects on the quality of life for affected individuals it is imperative that effective therapies are developed. Here we discuss some of the new approaches to CNS myelin repair that hold promise for reducing the burden of diseases characterized by myelin loss.
oligonucleotides
2026-05-13 | Industry Insights: Regulatory progress and AI-driven advances in nucleic acid therapeutics
Across March and April 2026, activity in the nucleic acid therapeutics field reflected broad regulatory momentum and continued clinical advancement across multiple RNA modalities. Regulatory highlights included US FDA Priority Review designations for Ionis' antisense oligonucleotide (ASO) zilganersen in Alexander disease, alongside EMA acceptance of GSK's marketing authorisation application for the ASO bepirovirsen in chronic hepatitis B. Clinical milestones featured first-in-human trials of novel modalities, including Alltrna's transfer RNA therapeutic AP003 and AIRNA's RNA-editing candidate AIR-001. AI-driven discovery also advanced, with Asimov launching an integrated RNA optimisation platform and ProQR partnering with Ginkgo Bioworks to scale high-throughput data generation for its RNA editing pipeline.
2026-03-04 | From scaffold to effector: reframing GFAP in neurodegeneration.
Neurodegenerative disorders impose a growing global burden, yet disease-modifying therapies remain limited. Glial fibrillary acidic protein (GFAP) has shifted from a passive astrocytic marker to an active effector that shapes neurodegenerative pathology. of Review: This review synthesizes mechanistic and translational evidence that defines GFAP as a proteoform-governed hub and highlights its value for biomarker-guided precision intervention. Key Scientific Concepts of Review: An extensive literature search across major databases was conducted using predefined keywords and strict inclusion criteria, covering mechanistic, pathological, and clinical studies. Evidence supports a GFAP proteoform code in which alternative splicing generates functionally distinct isoforms, and PTMs encode context-dependent assembly dynamics and signaling outputs. We summarize how GFAP proteoforms integrate cytoskeletal remodeling with inflammatory transcriptional programs (notably STAT3 and NF-κB), proteostasis stress, and mitochondrial dysfunction, thereby coupling astrocyte state transitions to neuronal vulnerability and synaptic impairment. Disease trajectories are context-specific: GFAP dysfunction drives primary toxicity in Alexander disease (AxD); in Alzheimer's disease (AD), isoform-specific mechanisms intersect with amyloidogenic machinery and track early preclinical astrocyte activation; and in frontotemporal dementia (FTD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS), GFAP reflects inflammatory-metabolic coupling during progression. Translationally, ultrasensitive plasma assays reveal GFAP elevation years to decades before symptom onset, complementing NfL and amyloid/tau within AT(N)-oriented diagnostic frameworks. Therapeutically, we evaluate precision strategies beyond global suppression, including ASO-based modulation, targeting STAT3/NF-κB-driven reactive programs, and restoring proteostasis via chaperone/autophagy pathways. Future progress hinges on isoform-/PTM-specific probes, conformational sensors, and spatial proteomic atlases validated in prospective longitudinal cohorts. In conclusion, GFAP represents both a mechanistic driver and a scalable biomarker, offering a translationally actionable axis to advance precision medicine in neurodegeneration.
2023-11-30 | Alexander Disease: Scientific Advancement and Therapeutic Intervention in Rare Disease Research
Alexander Disease (AxD) is a rare, heritable white matter condition, or leukodystrophy, that helps to understand how collaborative, translational research can identify therapeutic options in a complex illness. AxD is a rare disease, first described in 1949, that affects approximately one in 2.7 million births. The disease hinders the function of the central nervous system (CNS) through the biotoxic overproduction of protein aggregates which cause the deterioration of the myelin sheath. Given the extreme rarity of AxD, disease-specific research is relatively limited, and there is no disease-modifying treatment currently available. At present, a clinical trial is underway to examine the safety and efficacy of Ionis Pharmaceuticals’ ION373, an Antisense Oligonucleotide (ASO), that has reported success in preventing the progression of AxD in mouse models. This paper reviews the key components of AxD, therapeutic designs for AxD, and ultimately suggests future directions to optimize the therapeutic approach. This review also aims to promote rare disease awareness, as scientific progress for conditions like Alexander Disease is achieved through advocacy and promotion.
2021-06-14 | NG2 and GFAP co-expression after differentiation in cells transfected with mutant GFAP and in undifferentiated glioma cells.
Alexander disease is a rare disorder caused by mutations in the gene coding for glial fibrillary acidic protein (GFAP). In a previous study, differentiation of neurospheres transfected with these mutations resulted in a cell type that expresses both GFAP and NG2. To determine the effect of molecular marker mutations in comparison to undifferentiated glioma cells simultaneously expressing GFAP and NG2. We used samples of human glioblastoma (GBM) and rat neurospheres transfected with GFAP mutations to analyse GFAP and NG2 expression after differentiation. We also performed an immunocytochemical analysis of neuronal differentiation for both cell types and detection of GFAP, NG2, vimentin, Olig2, and caspase-3 at 3 and 7 days from differentiation. Both the cells transfected with GFAP mutations and GBM cells showed increased NG2 and GFAP expression. However, expression of caspase-3-positive cells was found to be considerably higher in transfected cells than in GBM cells. Our results suggest that GFAP expression is not the only factor associated with cell death in Alexander disease. Caspase-3 expression and the potential role of NG2 in increasing resistance to apoptosis in cells co-expressing GFAP and NG2 should be considered in the search for new therapeutic strategies for the disease.
2020-10-13 | [Clinical characteristics and diagnostic criteria on Alexander disease].
Alexander disease (ALXDRD) is a primary astrocyte disease caused by glial fibrillary acidic protein (GFAP) gene mutation. ALXDRD had been clinically regarded as a cerebral white matter disease that affects only children for about 50 years since the initial report in 1949; however, in the early part of the 21st century, case reports of adult-onset ALXDRD with medulla and spinal cord lesions increased. Basic research on therapies to reduce abnormal GFAP accumulation, such as drug-repositioning and antisense oligonucleotide suppression, has recently been published. The accumulation of clinical data to advance understanding of natural history is essential for clinical trials expected in the future. In this review, I classified ALXDRD into two subtypes: early-onset and late-onset, and detail the clinical symptoms, imaging findings, and genetic characteristics as well as the epidemiology and historical changes in the clinical classification described in the literature. The diagnostic criteria based on Japanese ALXDRD patients that are useful in daily clinical practice are also mentioned.
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Drug Discovery Landscape
2 orphan drug designations for Alexander disease.
2 orphan drug designations for Alexander disease.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
zilganersen | oligonucleotides | FDA | 2020-09-18 | — | Ionis Pharmaceuticals |
2'-O-(2-methoxyethyl)-D-ribose antisense oligonucleotide targeting glial fibrillary acidic protein messenger ribonucleic acid | oligonucleotides | EMA | 2019-10-17 | — | Ionis Development (Ireland) Limited |
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