RARE DISEASE
Kennedy disease
Kennedy disease
Kennedy disease
Synonyms: SBMA, SMAX1, X-linked BSMA, X-linked bulbospinal amyotrophy, X-linked bulbospinal muscular atrophy, X-linked spinal and bulbar muscular atrophy
Synonyms: SBMA, SMAX1, X-linked BSMA, X-linked bulbospinal amyotrophy, X-linked bulbospinal muscular atrophy, X-linked spinal and bulbar muscular atrophy
Synonyms: SBMA, SMAX1, X-linked BSMA, X-linked bulbospinal amyotrophy, X-linked bulbospinal muscular atrophy, X-linked spinal and bulbar muscular atrophy
Drug discovery
5
drugs
With orphan designations
Overview
Kennedy disease (KD), also known as spinal and bulbar muscular atrophy (SBMA), is a rare X-linked recessive neuromuscular disorder caused by a CAG trinucleotide repeat expansion in the androgen receptor gene. It manifests in adulthood (30–60 years) with progressive limb and bulbar muscle weakness, atrophy, tremors, dysphagia, and endocrine features (gynecomastia, hypogonadism). Slow progression preserves ambulatory capacity for decades, with near-normal lifespan but increased mortality from respiratory complications [1][2][5][6].
Therapies
Symptomatic management: Medications (e.g., leuprorelin for androgen suppression [7][11]), speech/swallowing therapy, physiotherapy, and assistive devices [1][5][13].
Experimental approaches: Small-molecule RNA modulators targeting mutant mRNA splicing (e.g., ReviR Therapeutics’ VoyageR platform [3]).
Categories: rare genetic diseases, rare infertility disorders, rare neurological diseases
Research Papers
344 drug discovery papers about Kennedy disease, with 3 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
344 drug discovery papers about Kennedy disease, with 3 first-in-class and 1 next-in-class emerging drug candidates forecasted to outperform the average preclinical success rate. Recent publications:
categories:
Small molecules
small molecules
2026-03-12 | A case of type 2 diabetes with spinal and bulbar muscular atrophy treated with oral semaglutide while sparing muscle reduction for two years: a case report with literature review.
Semaglutide has demonstrated beneficial effects in patients with type 2 diabetes; however, its long-term impact on skeletal muscle remains uncertain, particularly in individuals with multiple risk factors for muscle decline. We report a case of a 65-year-old man with type 2 diabetes who developed progressive proximal muscle weakness and was subsequently diagnosed with spinal and bulbar muscular atrophy (SBMA), for which leuprorelin therapy was initiated. Following treatment initiation, he exhibited worsened glycemic control, increased body weight and fat mass, along with reductions in both skeletal muscle mass and strength. At the age of 72, oral semaglutide was introduced. Over the following two years, improvements in glycemic parameters and reductions in fat mass were observed. Importantly, skeletal muscle mass and strength were relatively preserved, with only a minor annual decrease in muscle mass (- 0.1 kg/year), consistent with changes reported in previous studies of semaglutide-treated patients without neuromuscular conditions. To our knowledge, this is the first reported case describing the use of semaglutide in a patient with diabetes and SBMA under leuprorelin treatment, suggesting the potential utility of GLP-1 receptor agonists in managing metabolic parameters in individuals at high risk for muscle decline.
2026-03-10 | In silico Modeling for Small Molecule PRMT6 Inhibitors for the Treatment of Spinal Bulbar Muscular Atrophy (SBMA)
Spinal Bulbar Muscular Atrophy (SBMA), or Kennedy’s disease, is a rare, inherited neuromuscular disorder that leads to progressive muscle degeneration, weakness, and twitching. While it affects approximately 1 in 100,000 individuals worldwide, currently, there are no approved treatments for SBMA, leaving a substantial unmet medical need. Our program focuses on developing a novel therapeutic approach targeting PRMT6, a co-activator of the Androgen Receptor (AR) implicated in SBMA progression. The aim is to design a highly selective, brain-penetrant PRMT6 inhibitor targeting an allosteric site on the enzyme. Preliminary studies have shown that inhibiting PRMT6 reduces mutant AR activity and improves motor function in disease models. Here, we employ AI-guided in silico modeling to optimize the PRMT6 probe scaffold SGC6870 as a potential therapeutic for the treatment of SBMA. This workflow integrates computational drug design, medicinal chemistry, and molecular biology, with subsequent in vitro and in vivo ADME optimization of prioritized compounds. Table of key terms and definitions: Key term Definition PRMT6 Protein arginine methyltransferase 6, a transcriptional co-regulator Androgen receptor (AR) Type of nuclear receptor that is activated by binding any of the androgenic hormones, including testosterone and dihydrotestosterone, in the cytoplasm and then translocating into the nucleus SBMA X-linked, slowly progressive neuromuscular disorder that affects adult males, typically presenting with muscle weakness, bulbar dysfunction, and endocrine abnormalities SGC6870 A potent, selective and cell active allosteric inhibitor of PRMT6 S-adenosyl-L-methionine (SAM) Methyltransferase cofactor SAR Structure activity relationship ADME Absorption, Distribution, Metabolism and Excretion DMPK Drug metabolism and pharmacokinetics
2025-12-13 | Early pathogenesis of spinal and bulbar muscular atrophy uncovered by human iPSC-derived motor neurons highlights pathogenic neuropeptides as therapeutic targets
Abstract Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disorder caused by the expansion of the polyglutamine tract in the androgen receptor (AR). Motor neurons (MNs) derived from patient-specific induced pluripotent stem cells (iPSCs) robustl y recapitulated early SBMA phenotypes driven by endogenous mutant AR in the absence of testosterone (dihydrotestosterone) and detectable mutant AR aggregation. Notably, endoplasmic reticulum stress markedly exacerbated SBMA pathology. Cross-species integrative analyses of patient-derived neurons and spinal cords of transgenic mouse models revealed high expression of multiple disease-associated neuropeptides, including urotensin II (UTS2), in patient spinal MNs that was correlated with disease onset and progression in iPSC-derived MNs. Downstream signaling analyses of these neuropeptides revealed convergent molecular pathways whose pharmacological inhibition rescued cellular phenotypes. Together, these results establish a human disease model harboring endogenous mutant AR that closely reproduces early SBMA pathology and provides molecular leads for elucidating disease mechanisms and biomarkers and developing therapeutic targets.
2025-12-05 | Pathophysiological Mechanisms and Clinical Phenotypes of Kennedy Syndrome
Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy syndrome, is a rare X-linked neuromuscular disorder characterized by the progressive degeneration of lower motor neurons in the brainstem and spinal cord. The disease etiology originates from an unstable CAG trinucleotide repeat expansion within the first exon of the androgen receptor (AR) gene, resulting in an elongated polyglutamine tract. This mutation confers a toxic gain-of-function to the androgen receptor protein, which aggregates within the nucleus of motor neurons and muscles in a ligand-dependent manner, necessitating the presence of circulating androgens for phenotypic expression. Clinical presentation typically manifests in adult males during the fourth or fifth decade of life, encompassing proximal muscle weakness, bulbar palsy, fasciculations, and distinct endocrine disturbances such as gynecomastia and reduced fertility, reflecting a state of mild androgen insensitivity. Recent investigations have shifted the paradigm from a purely neuron-centric view to a broader neuromuscular perspective, implicating skeletal muscle as a primary site of toxicity. Current therapeutic options remain largely supportive, though elucidating the molecular cascades of transcriptional dysregulation, mitochondrial dysfunction, and impaired axonal transport has identified novel targets for disease-modifying interventions. This review discusses about molecular advances with clinical observation to delineate the current state of SBMA research
2025-11-19 | Therapeutic impact of leuprorelin acetate on spinal and bulbar muscular atrophy: pre- and post-marketing observational study.
Although leuprorelin acetate, a luteinizing hormone-releasing hormone agonist, has been approved based on short-term clinical trials conducted in Japan, its long-term efficacy on physical function remains unclear. We aimed to evaluate the long-term therapeutic efficacy of leuprorelin acetate using real-world clinical data through a self-controlled trend-shift analysis. The analysis included 91 genetically confirmed patients with spinal and bulbar muscular atrophy, with follow-up data collected before and after treatment initiation. The functional outcomes assessed included the revised amyotrophic lateral sclerosis functional rating scale (ALSFRS-R) and modified Norris scales, grip power, and serum creatinine levels. Leuprorelin acetate significantly slowed disease progression. For instance, the annual ALSFRS-R decline rate improved from approximately 0.5 points pre-treatment to 0.2 points post-treatment. The subgroup analysis supported the potential benefit of early intervention. These findings highlight the value of leveraging patient registries and post-marketing real-world data to evaluate treatment efficacy in slowly progressive diseases, such as SBMA, where traditional randomized controlled trials are often limited by insufficient statistical power to detect therapeutic efficacy. They also underscore the need for innovative methodologies to assess post-approval drug performance, paving the way for improved clinical outcomes for neurodegenerative diseases.
oligonucleotides
2026-05-07 | PGC-1α pathway dysregulation disrupts myofiber specification in a mouse model of SBMA.
Skeletal muscle pathology is a critical but poorly understood contributor to neuromuscular degeneration in spinal and bulbar muscular atrophy (SBMA), a CAG/polyglutamine (polyQ) expansion disorder caused by mutation in the androgen receptor (AR). Using a gene-targeted SBMA mouse model, we applied single-nucleus RNA sequencing to identify a disease-specific population of skeletal muscle myonuclei that replaced normal myonuclear subtypes. This transition was associated with dysregulation of the pathway governed by PGC-1α, a central regulator of myofiber specification and metabolic identity. PGC-1α dysfunction in SBMA muscle was age-, hormone-, and polyQ length-dependent and was partially rescued by subcutaneous delivery of AR-targeted antisense oligonucleotides. Integrated ChIP-seq and RNA-seq analyses revealed that aberrant PGC-1α activity promoted the expression of a distinct set of myofiber specification genes while downregulating those that define healthy Type IIb and Type IIx myonuclei. We propose a model in which this dysfunction arose downstream of polyQ-mediated sequestration of PGC-1α cofactors MEF2, CREB, and CBP, leading to transcriptional reprogramming and cellular dysfunction. These findings implicated PGC-1α dysregulation as a key event linking AR polyQ expansion to skeletal muscle degeneration and suggested a shared mechanism for polyQ-mediated muscle pathology across related neurodegenerative diseases.
2026-03-28 | Restoring early postnatal synaptic dysregulation rescues motor neuron degeneration in a mouse model of Spinal and Bulbar Muscular Atrophy.
Spinal and bulbar muscular atrophy (SBMA) is an adult-onset neurodegenerative disorder caused by expansion of a polyglutamine tract in the androgen receptor (AR). Here, we show that polyglutamine-expanded AR accumulates in the nucleus of motor neurons and induces aberrant upregulation of glutamatergic synaptic genes through dysfunction of the master transcriptional repressor REST during early postnatal development in a mouse model of SBMA (AR-97Q mice). Reducing mutant AR or restoring REST function using antisense oligonucleotides during the neonatal period attenuated the upregulation of glutamatergic synaptic genes and ameliorated the disease phenotype and histopathology in AR-97Q mice. Furthermore, we observed increased calcium activity in induced pluripotent stem cell-derived motor neurons from SBMA patients compared to those from healthy controls, reflecting neuronal hyperexcitability. Late-onset neurodegeneration in SBMA is attributable to early synaptic defects and the resulting hyperexcitability of motor neurons, which may represent therapeutic targets.
2026-01-19 | An acyclic nucleic acid-modified siRNA targeting CAG expansions for polyglutamine disease treatment.
Polyglutamine (polyQ) diseases are inherited neurological disorders caused by an expansion of the cytosine-adenine-guanine (CAG) repeat in the causative genes. These include Huntington's disease, spinal and bulbar muscular atrophy (SBMA), and spinocerebellar ataxias (SCAs). Clinical trials have been conducted using nucleic acid therapeutics to silence the causative gene for these diseases, but none have been approved for use. Furthermore, while oligonucleotides targeting the CAG repeats are an attractive therapeutic option, concomitant silencing of the wild-type allele with normal CAG repeats can result in neuronal dysfunction. In this study, we developed an acyclic serinol nucleic acid (SNA)-modified small interfering RNA (siRNA) targeting CAG repeats. We also evaluated the safety and efficacy of the siRNA in different mouse models of polyQ diseases. Intracerebroventricularly administered siRNA was widely distributed throughout the central nervous system, where it selectively silenced the alleles encoding polyQ proteins without affecting their wild-type counterparts. Consequently, the intranuclear aggregation of polyQ proteins was reduced in mouse models of SBMA and SCA type 3. The siRNA attenuated neuromuscular degeneration and improved the lifespan and motor function of the SBMA mice. These findings suggest that SNA-modified siRNAs targeting CAG repeats represent a promising approach for treating polyQ diseases.
2025-08-28 | Peripherally administered androgen receptor-targeted antisense oligonucleotide rescues spinal pathology in a murine SBMA model.
Degeneration of the neuromuscular system is a characteristic feature of spinal and bulbar muscular atrophy (SBMA), a CAG/polyglutamine (polyQ) expansion disorder caused by mutation in the androgen receptor (AR). Using a gene-targeted mouse model of SBMA, AR113Q mice, we demonstrate age-dependent degeneration of the neuromuscular system that initially manifests with muscle weakness and atrophy and progresses to include denervation of neuromuscular junctions and lower motor neuron soma atrophy. Using this model, we tested the hypothesis that therapeutic intervention targeting skeletal muscle during this period of disease progression arrests degeneration of the neuromuscular system. To accomplish this, AR-targeted antisense oligonucleotides were administered subcutaneously to symptomatic AR113Q mice to reduce expression of polyQ AR in peripheral tissues but not in the spinal cord. This intervention rescued muscle atrophy, neuromuscular junction innervation, lower motor neuron soma size, and survival in aged AR113Q mice. Single-nucleus RNA sequencing revealed age-dependent transcriptional changes in the AR113Q spinal cord during disease progression, which were mitigated by peripheral AR gene silencing. Our findings underscore the intricate interplay between peripheral tissues and the central nervous system in SBMA and emphasize the therapeutic effectiveness of peripheral gene knockdown in symptomatic disease.
2025-08-14 | Neuroaxonal Degeneration as a Converging Mechanism in Motor Neuron Diseases (MNDs): Molecular Insights into RNA Dysregulation and Emerging Therapeutic Targets.
Motor Neuron Diseases (MNDs) such as Amyotrophic Lateral Sclerosis (ALS), Primary Lateral Sclerosis (PLS), Hereditary Spastic Paraplegia (HSP), Spinal Muscular Atrophy with Respiratory Distress Type 1 (SMARD1), Multisystem Proteinopathy (MSP), Spinal and Bulbar Muscular Atrophy (SBMA), and ALS associated to Frontotemporal Dementia (ALS-FTD), have traditionally been studied as distinct entities, each one with unique genetic and clinical characteristics. However, emerging research reveals that these seemingly disparate conditions converge on shared molecular mechanisms that drive progressive neuroaxonal degeneration. This narrative review addresses a critical gap in the field by synthesizing the most recent findings into a comprehensive, cross-disease mechanisms framework. By integrating insights into RNA dysregulation, protein misfolding, mitochondrial dysfunction, DNA damage, kinase signaling, axonal transport failure, and immune activation, we highlight how these converging pathways create a common pathogenic landscape across MNDs. Importantly, this perspective not only reframes MNDs as interconnected neurodegenerative models but also identifies shared therapeutic targets and emerging strategies, including antisense oligonucleotides, autophagy modulators, kinase inhibitors, and immunotherapies that transcend individual disease boundaries. The diagnostic and prognostic potential of Neurofilament Light Chain (NfL) biomarkers is also emphasized. By shifting focus from gene-specific to mechanism-based approaches, this paper offers a much-needed roadmap for advancing both research and clinical management in MNDs, paving the way for cross-disease therapeutic innovations.
proteins
2025-07-18 | Targeting androgen receptor stability and degradation: approaches for developing a therapy for spinal and bulbar muscular atrophy.
Conformational changes of proteins can occur due to mutations or stress conditions, altering their functionality through loss of physiological or gain of pathological function. A Protein Quality Control (PQC) system exists in cells to deal with the accumulation of misfolded proteins and aggregates, comprising a network of chaperones and degradative pathways to refold or remove the aberrant proteins. Protein misfolding and PQC system impairment lead to a broad range of diseases, including neurodegenerative and neuromuscular disorders, among them spinal and bulbar muscular atrophy (SBMA). SBMA is a neuromuscular disorder caused by a polyglutamine expansion (polyQ) in the androgen receptor (AR) protein. Expanded AR (ARexp) is highly prone to misfolding and aggregation, leading to its accumulation in affected tissues. Here, we summarise the dynamics that control AR protein stability and its degradation in physiological conditions. Next, we recapitulate the current knowledge of the molecular mechanisms of SBMA pathogenesis involving the PQC system. Finally, we provide an overview of promising approaches to SBMA intervention involving the modulation of PQC system functions to reduce ARexp accumulation and its toxic effects in affected cells.
2023-06-05 | X-linked SBMA model mice display relevant non-neurological phenotypes and their expression of mutant androgen receptor protein in motor neurons is not required for neuromuscular disease.
X-linked spinal and bulbar muscular atrophy (SBMA; Kennedy's disease) is a rare neuromuscular disorder characterized by adult-onset proximal muscle weakness and lower motor neuron degeneration. SBMA was the first human disease found to be caused by a repeat expansion mutation, as affected patients possess an expanded tract of CAG repeats, encoding polyglutamine, in the androgen receptor (AR) gene. We previously developed a conditional BAC fxAR121 transgenic mouse model of SBMA and used it to define a primary role for skeletal muscle expression of polyglutamine-expanded AR in causing the motor neuron degeneration. Here we sought to extend our understanding of SBMA disease pathophysiology and cellular basis by detailed examination and directed experimentation with the BAC fxAR121 mice. First, we evaluated BAC fxAR121 mice for non-neurological disease phenotypes recently described in human SBMA patients, and documented prominent non-alcoholic fatty liver disease, cardiomegaly, and ventricular heart wall thinning in aged male BAC fxAR121 mice. Our discovery of significant hepatic and cardiac abnormalities in SBMA mice underscores the need to evaluate human SBMA patients for signs of liver and heart disease. To directly examine the contribution of motor neuron-expressed polyQ-AR protein to SBMA neurodegeneration, we crossed BAC fxAR121 mice with two different lines of transgenic mice expressing Cre recombinase in motor neurons, and after updating characterization of SBMA phenotypes in our current BAC fxAR121 colony, we found that excision of mutant AR from motor neurons did not rescue neuromuscular or systemic disease. These findings further validate a primary role for skeletal muscle as the driver of SBMA motor neuronopathy and indicate that therapies being developed to treat patients should be delivered peripherally.
2022-10-06 | The role of ubiquitination in spinal and bulbar muscular atrophy
Spinal and bulbar muscular atrophy (SBMA) is a neurodegenerative and neuromuscular genetic disease caused by the expansion of a polyglutamine-encoding CAG tract in the androgen receptor (AR) gene. The AR is an important transcriptional regulator of the nuclear hormone receptor superfamily; its levels are regulated in many ways including by ubiquitin-dependent degradation. Ubiquitination is a post-translational modification (PTM) which plays a key role in both AR transcriptional activity and its degradation. Moreover, the ubiquitin-proteasome system (UPS) is a fundamental component of cellular functioning and has been implicated in diseases of protein misfolding and aggregation, including polyglutamine (polyQ) repeat expansion diseases such as Huntington’s disease and SBMA. In this review, we discuss the details of the UPS system, its functions and regulation, and the role of AR ubiquitination and UPS components in SBMA. We also discuss aspects of the UPS that may be manipulated for therapeutic effect in SBMA.
2022-01-18 | Inhibition of Polyglutamine Misfolding with D-Enantiomeric Peptides Identified by Mirror Image Phage Display Selection
Nine heritable diseases are known that are caused by unphysiologically elongated polyglutamine tracts in human proteins leading to misfolding, aggregation and neurodegeneration. Current therapeutic strategies include efforts to inhibit the expression of the respective gene coding for the polyglutamine-containing proteins. There are, however, concerns that this may interfere with the physiological function of the respective protein. We aim to stabilize the protein's native conformation by D-enantiomeric peptide ligands to prevent misfolding and aggregation, shift the equilibrium between aggregates and monomers towards monomers and dissolve already existing aggregates into non-toxic and functional monomers. Here, we performed a mirror image phage display selection on the polyglutamine containing a fragment of the androgen receptor. An elongated polyglutamine tract in the androgen receptor causes spinal and bulbar muscular atrophy (SBMA). The selected D-enantiomeric peptides were tested for their ability to inhibit polyglutamine-induced androgen receptor aggregation. We identified D-enantiomeric peptide QF2D-2 (sqsqwstpqGkwshwprrr) as the most promising candidate. It binds to an androgen receptor fragment with 46 consecutive glutamine residues and decelerates its aggregation, even in seeded experiments. Therefore, QF2D-2 may be a promising drug candidate for SBMA treatment or even for all nine heritable polyglutamine diseases, since its aggregation-inhibiting property was shown also for a more general polyglutamine target.
2021-10-04 | ClC-2-like Chloride Current Alterations in a Cell Model of Spinal and Bulbar Muscular Atrophy, a Polyglutamine Disease.
Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by expansions of a polyglutamine (polyQ) tract in the androgen receptor (AR) gene. SBMA is associated with the progressive loss of lower motor neurons, together with muscle weakness and atrophy. PolyQ-AR is converted to a toxic species upon binding to its natural ligands, testosterone, and dihydrotestosterone (DHT). Our previous patch-clamp studies on a motor neuron-derived cell model of SBMA showed alterations in voltage-gated ion currents. Here, we identified and characterized chloride currents most likely belonging to the chloride channel-2 (ClC-2) subfamily, which showed significantly increased amplitudes in the SBMA cells. The treatment with the pituitary adenylyl cyclase-activating polypeptide (PACAP), a neuropeptide with a proven protective effect in a mouse model of SBMA, recovered chloride channel current alterations in SBMA cells. These observations suggest that the CIC-2 currents are affected in SBMA, an alteration that may contribute and potentially determine the pathophysiology of the disease.
gene therapies
2025-12-04 | Bone Fragility and Fracture Characteristics in Patients With Spinal and Bulbar Muscular Atrophy.
Spinal and bulbar muscular atrophy (SBMA) is a hereditary neuromuscular disorder linked to androgen receptor gene mutations, often associated with metabolic abnormalities. We aimed to investigate the incidence of fragility fractures and the underlying mechanisms in SBMA. Consecutive genetically confirmed SBMA patients and healthy controls (HC) were enrolled. We surveyed fracture history and assessed motor function, bone metabolism markers, and bone mineral density (BMD) using dual-energy X-ray absorptiometry. Longitudinal BMD changes were also analyzed between SBMA patients and HC. A total of 109 SBMA patients and 21 HC were included. Fragility fractures in SBMA patients were mainly observed in cortical bone-dominant regions. Their lower limb BMD was significantly reduced (SBMA 1.10 g/cm, HC 1.19 g/cm; p < 0.05) and further decreased overtime. Despite low bone resorption markers, bone formation markers showed no difference between the groups, suggesting that SBMA patients exhibit characteristics of low turnover osteoporosis. Serum 25-hydroxyvitamin D levels were lower in SBMA patients than in HC (15.4 ng/mL vs. 19.4 ng/mL; p < 0.01). Longitudinal analysis revealed that SBMA patients had a higher incidence of fragility fractures than HC (log-rank test, p < 0.05), with the first fragility fracture occurring 10 years after the onset of muscle weakness. Low baseline BMD was a predictor of fragility fractures (adjusted OR = 0.32; 95% CI: 0.17-0.60; p < 0.05). SBMA patients have a high fragility fracture incidence, particularly in cortical bone, with a progressive BMD decrease. Low bone turnover and vitamin D deficiency are associated with these fractures.
2025-09-17 | Conserved Aberrant Developmental Trajectories of Human and Mouse SBMA Motor Neurons
Spinal bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by a polyglutamine repeat expansion in the androgen receptor gene (AR). Lower motor neuron loss is a key feature of the disease, yet it remains poorly understood why these cells are affected. The transcriptional mechanisms underlying SBMA pathogenesis and how these evolve across developmental and disease stages remains incompletely defined. To elucidate the molecular mechanisms underlying motor neuron loss in SBMA, we first performed transcriptomic profiling of both induced pluripotent stem cell derived motor neurons (iPSC-MNs) generated from SBMA patients and laser-captured micro dissected motor neurons (LCM-MNs) from symptomatic AR100 SBMA mice. We compared differential gene expression between the two models to identify shared transcriptional programs. To address the temporal progression of molecular changes we conducted profiling at key stages of motor neurogenesis in the developing iPSC-MNs and at pre-symptomatic and end- stage disease in AR100 SBMA mice to elucidate the emergence of the transcriptional phenotype and the trajectory of the gene expression changes. We found significant transcriptional convergence between these two species. Notably, shared dysregulation was observed in pathways related to the spliceosome, the cell cycle and mitochondrial function. These transcriptional alterations emerged early in motor neurogenesis suggesting a developmental component to SBMA. Further in AR100 LCM-MNs we also observed disruption of mitochondrial and DNA damage repair pathways from pre-symptomatic to end stage disease. This study identifies conserved pathogenic mechanisms across two SBMA model systems and provides crucial insights into the molecular basis and temporal dynamics of SBMA progression which may help identify potential therapeutic targets for SBMA.
2025-02-07 | Therapeutic targeting of the polyglutamine androgen receptor in Spinal and Bulbar Muscular Atrophy.
Spinal and Bulbar Muscular Atrophy (SBMA) is a slowly progressive, X-linked, and sex-limited degenerative disorder affecting lower motor neurons and skeletal muscle which lacks disease-modifying therapies. This disease is caused by a CAG/polyglutamine (polyQ) tract expansion in the androgen receptor (AR) gene, and its pathogenesis is driven by toxic gain-of-function mechanisms. Affected men develop proximal limb and bulbar muscle weakness along with signs of partial androgen insensitivity. Toxicity of the polyQ AR is mediated by protein misfolding and nuclear translocation that follow ligand binding, resulting in the disruption of downstream homeostatic mechanisms. This review highlights what is known about disease pathogenesis and how this has been leveraged to test potential therapeutic approaches. The focus is on strategies that alleviate polyQ AR toxicity in SBMA, including those that alter AR function, diminish the expression of the encoding gene, or promote clearance of the misfolded, mutant protein. We discuss emerging strategies to mitigate polyQ AR toxicity, including gene editing, RNA targeted therapies, and efforts to harness proteostatic mechanisms. These promising approaches are discussed in the context of challenges for drug discovery efforts that are faced when attempting to treat a rare and slowly progressive neurodegenerative disorder.
2024-10-09 | CRISPR-Cas9 guided RNA-based model for the silencing of spinal bulbar muscular atrophy: A functional genetic disorder.
This study explores a novel therapeutic approach for spinal bulbar muscular atrophy (SBMA), a neurodegenerative disorder caused by a mutation in the Androgen Receptor (AR) gene. The aim is to investigate the potential of CRISPR-Cas9 technology in targeting the mutant AR gene to inhibit its production. The objectives include assessing the accuracy and efficacy of CRISPR-Cas9 guided RNAs in silencing the mutant gene and evaluating the feasibility of this approach as a treatment for SBMA. Computational and in-silico approaches are used to evaluate the feasibility of using CRISPR-Cas9 technology for treating SBMA. Computational analysis is used to design CRISPR-Cas9 guided RNAs targeting the mutant AR gene, assessing their on-target and off-target scores, GC content, and structural accuracy. In-silico simulations predict the potential therapeutic outcomes of the CRISPR-Cas9 approach in an artificial environment. Three guided RNA (gRNA) sequences were designed using the CHOPCHOP tool, targeting specific regions of the AR gene with high efficiency and 100% match. These gRNAs demonstrated effective targeting with minimal off-target scores and optimal GC content. Additionally, lentiCRISPR v2 plasmids were designed for the delivery of CRISPR materials, enabling high-efficiency multiplex genome editing of the AR gene. Thermodynamic ensemble predictions indicated favorable secondary structure stability of the designed gRNAs, further supporting their suitability for gene editing. The evaluation of designed gRNAs confirmed their strong binding ability to the target sequences, validating their potential as effective tools for genome editing. The study highlights the potential of CRISPR-Cas9 technology for targeting the Androgen Receptor gene associated with spinal bulbar muscular atrophy (SBMA). The findings support the feasibility of this approach for gene editing and suggest further exploration in preclinical and clinical settings. Recommendations include continued research to optimize CRISPR-Cas9 delivery methods and enhance specificity for therapeutic applications in SBMA.
2024-04-25 | Precise editing of pathogenic nucleotide repeat expansions in iPSCs using paired prime editor
Nucleotide repeat expansion disorders, a group of genetic diseases characterized by the expansion of specific DNA sequences, pose significant challenges to treatment and therapy development. Here, we present a precise and programmable method called prime editor-mediated correction of nucleotide repeat expansion (PE-CORE) for correcting pathogenic nucleotide repeat expansion. PE-CORE leverages a prime editor and paired pegRNAs to achieve targeted correction of repeat sequences. We demonstrate the effectiveness of PE-CORE in HEK293T cells and patient-derived induced pluripotent stem cells (iPSCs). Specifically, we focus on spinal and bulbar muscular atrophy and spinocerebellar ataxia type, two diseases associated with nucleotide repeat expansion. Our results demonstrate the successful correction of pathogenic expansions in iPSCs and subsequent differentiation into motor neurons. Specifically, we detect distinct downshifts in the size of both the mRNA and protein, confirming the functional correction of the iPSC-derived motor neurons. These findings highlight PE-CORE as a precision tool for addressing the intricate challenges of nucleotide repeat expansion disorders, paving the way for targeted therapies and potential clinical applications.
other
2025-11-24 | Exosome-rich mesenchymal stem cell secretome improves strength in patients with amyotrophic lateral sclerosis, Kennedy disease, congenital myasthenic syndrome and Lewy body dementia.
Amyotrophic lateral sclerosis (ALS), Lewy Body dementia (LBD), Kennedy disease (KD), and Congenital Myasthenic Syndrome (CMS) are progressive motor disorders for which no disease modifying treatment exists. ALS and LBD are uniformly, and often rapidly, fatal. No treatment of any kind has ever resulted in actual improvement for ALS patients; the best that has been achieved is minor slowing of their progression. Forty-one preclinical studies of intra-nasal instillation of mesenchymal stem cell exosomes have, however, demonstrated complete safety and efficacy for models of a variety of neurocognitive and motor disorders. We hypothesized that intranasal exosomes treatment in humans would be completely safe and also effective for the treatment of motor disorders such as ALS, LBD, KD and CMS. 18 patients with ALS, Kennedy Disease, Congenital Myasthenic Syndrome, or Lewy Body Dementia had 32 AlloEx Exosome® treatments to assess safety, attenuation of disease, and increase in strength and motor function. The study was conducted under the clinical trial NCT07105371 found at clinicaltrials.gov/study/NCT07105371. There were no adverse events of any kind reported among these treatments. All patients, except for one, achieved some degree of clinical and strength improvement; the longest improvement was recorded at the 6-month follow-up. Intranasally-instilled AlloEx Exosomes® are completely safe, attenuate progression, and improve strength in ALS, Kennedy Disease, CMS, and LBD.
2025-09-04 | Effective and safe use of alirocumab in spinal and bulbar muscular atrophy with high cardiovascular risk: a case report.
BACKGROUND: Spinal and bulbar muscular atrophy (SBMA) is a rare X-linked neuromuscular disorder characterized by progressive muscle weakness and endocrine abnormalities. Beyond its classic neurological presentation, SBMA is increasingly associated with metabolic and cardiovascular comorbidities, including dyslipidemia and insulin resistance. CASE REPORT: We present the case of a 54-year-old male with genetically confirmed SBMA and high cardiovascular risk, in whom statins and ezetimibe were contraindicated due to persistently elevated creatine kinase levels and underlying muscle involvement. Coronary CT angiography revealed subclinical atherosclerosis. Alirocumab, a PCSK9 inhibitor, was initiated at a dose of 150 mg every 2 weeks. After six months, LDL cholesterol was reduced by 54.9% without adverse effects or functional decline, and CK levels remained stable. CONCLUSIONS: This case highlights the potential role of PCSK9 inhibitors as a safe and effective lipid-lowering option in patients with neuromuscular disorders at high cardiovascular risk, for whom traditional therapies are not feasible. It also highlights the importance of integrated cardiovascular care in managing multisystem diseases, such as SBMA. https://www.europeanreview.org/wp/wp-content/uploads/Graphical-Abstract-2-1.jpg.
2025-08-05 | Spinal and bulbar muscular atrophy with hand tremors and chronic limb weakness, Kennedy disease.
Spinal and bulbar muscular atrophy (SBMA) is an X-linked neuromuscular disorder primarily affecting adult males due to the expansion of CAG repeats in the androgen receptor gene. It manifests as progressive lower motor neuropathy and androgen deficiency. A Japanese man in his late 50s presented with gradually progressive muscle weakness over 6 years. Examination revealed muscle weakness and atrophy in upper and lower limbs, decreased deep tendon reflexes, involuntary facial movements, bilateral finger tremors, tongue atrophy, fasciculations and bilateral gynaecomastia. Blood tests indicated elevated creatine kinase and mild hepatic dysfunction. Nerve conduction studies showed decreased sensory nerve action potentials, and electromyography demonstrated neurogenic changes. Genetic testing confirmed SBMA with 47 CAG repeats despite no family history. Treatment included leuprorelin acetate and rehabilitation using a wearable cyborg hybrid-assistive limb. As SBMA progresses slowly and symptoms like hand tremors and decreased serum creatinine precede significant weakness, early recognition is critical for diagnosis.
2024-06-12 | A case of SBMA presenting with myasthenic syndrome limited to a dropped head
Abstract A 76‐year‐old man with spinal and bulbar muscular atrophy (SBMA) developed an acute course of the dropped head with diurnal fluctuations that worsened in the evening. He was diagnosed with myasthenic syndrome based on a decreased response to repeated stimulation, as well as increased jitter and blocking on single‐fiber electromyography, indicating disturbed neuromuscular transmission. Dropped head symptom was successfully alleviated and maintained by immunotherapy. Although limited reports are available on SBMA cases accompanied by myasthenic syndrome and on the clinical impact of impaired neuromuscular transmission on SBMA, myasthenic syndrome may be a common condition and even a part of the phenotypic spectrum of SBMA. To our knowledge, this is the first case of SBMA comorbid with myasthenic syndrome limited to the dropped head.
2024-01-12 | Dysregulated synaptic gene expression in oligodendrocytes of spinal and bulbar muscular atrophy
Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by an expanded CAG repeat in the androgen receptor (AR) gene. To elucidate the cell type-specific temporal gene expression in SBMA, we performed single-nucleus RNA sequencing on the spinal cords of AR-97Q mice. Among all cell types, oligodendrocytes (OLs) had the highest number of differentially expressed genes before disease onset. Analysis of OL clusters suggested that pathways associated with cation channels and synaptic function were activated before disease onset, with increased output from OLs to neurons in AR-97Q mice compared to wild-type mice. These changes in the early stages were abrogated in the advanced stages. An OL cell model of SBMA showed phenotypes similar to those of AR-97Q mice at early stages, such as increased transcriptional changes in synapse organization. Our results indicate that the dysregulation of cell-to-cell communication has a major impact on the early pathology of SBMA and is a potential therapeutic target for SBMA.
small molecules
2026-03-12 | A case of type 2 diabetes with spinal and bulbar muscular atrophy treated with oral semaglutide while sparing muscle reduction for two years: a case report with literature review.
Semaglutide has demonstrated beneficial effects in patients with type 2 diabetes; however, its long-term impact on skeletal muscle remains uncertain, particularly in individuals with multiple risk factors for muscle decline. We report a case of a 65-year-old man with type 2 diabetes who developed progressive proximal muscle weakness and was subsequently diagnosed with spinal and bulbar muscular atrophy (SBMA), for which leuprorelin therapy was initiated. Following treatment initiation, he exhibited worsened glycemic control, increased body weight and fat mass, along with reductions in both skeletal muscle mass and strength. At the age of 72, oral semaglutide was introduced. Over the following two years, improvements in glycemic parameters and reductions in fat mass were observed. Importantly, skeletal muscle mass and strength were relatively preserved, with only a minor annual decrease in muscle mass (- 0.1 kg/year), consistent with changes reported in previous studies of semaglutide-treated patients without neuromuscular conditions. To our knowledge, this is the first reported case describing the use of semaglutide in a patient with diabetes and SBMA under leuprorelin treatment, suggesting the potential utility of GLP-1 receptor agonists in managing metabolic parameters in individuals at high risk for muscle decline.
2026-03-10 | In silico Modeling for Small Molecule PRMT6 Inhibitors for the Treatment of Spinal Bulbar Muscular Atrophy (SBMA)
Spinal Bulbar Muscular Atrophy (SBMA), or Kennedy’s disease, is a rare, inherited neuromuscular disorder that leads to progressive muscle degeneration, weakness, and twitching. While it affects approximately 1 in 100,000 individuals worldwide, currently, there are no approved treatments for SBMA, leaving a substantial unmet medical need. Our program focuses on developing a novel therapeutic approach targeting PRMT6, a co-activator of the Androgen Receptor (AR) implicated in SBMA progression. The aim is to design a highly selective, brain-penetrant PRMT6 inhibitor targeting an allosteric site on the enzyme. Preliminary studies have shown that inhibiting PRMT6 reduces mutant AR activity and improves motor function in disease models. Here, we employ AI-guided in silico modeling to optimize the PRMT6 probe scaffold SGC6870 as a potential therapeutic for the treatment of SBMA. This workflow integrates computational drug design, medicinal chemistry, and molecular biology, with subsequent in vitro and in vivo ADME optimization of prioritized compounds. Table of key terms and definitions: Key term Definition PRMT6 Protein arginine methyltransferase 6, a transcriptional co-regulator Androgen receptor (AR) Type of nuclear receptor that is activated by binding any of the androgenic hormones, including testosterone and dihydrotestosterone, in the cytoplasm and then translocating into the nucleus SBMA X-linked, slowly progressive neuromuscular disorder that affects adult males, typically presenting with muscle weakness, bulbar dysfunction, and endocrine abnormalities SGC6870 A potent, selective and cell active allosteric inhibitor of PRMT6 S-adenosyl-L-methionine (SAM) Methyltransferase cofactor SAR Structure activity relationship ADME Absorption, Distribution, Metabolism and Excretion DMPK Drug metabolism and pharmacokinetics
2025-12-13 | Early pathogenesis of spinal and bulbar muscular atrophy uncovered by human iPSC-derived motor neurons highlights pathogenic neuropeptides as therapeutic targets
Abstract Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disorder caused by the expansion of the polyglutamine tract in the androgen receptor (AR). Motor neurons (MNs) derived from patient-specific induced pluripotent stem cells (iPSCs) robustl y recapitulated early SBMA phenotypes driven by endogenous mutant AR in the absence of testosterone (dihydrotestosterone) and detectable mutant AR aggregation. Notably, endoplasmic reticulum stress markedly exacerbated SBMA pathology. Cross-species integrative analyses of patient-derived neurons and spinal cords of transgenic mouse models revealed high expression of multiple disease-associated neuropeptides, including urotensin II (UTS2), in patient spinal MNs that was correlated with disease onset and progression in iPSC-derived MNs. Downstream signaling analyses of these neuropeptides revealed convergent molecular pathways whose pharmacological inhibition rescued cellular phenotypes. Together, these results establish a human disease model harboring endogenous mutant AR that closely reproduces early SBMA pathology and provides molecular leads for elucidating disease mechanisms and biomarkers and developing therapeutic targets.
2025-12-05 | Pathophysiological Mechanisms and Clinical Phenotypes of Kennedy Syndrome
Spinal and bulbar muscular atrophy (SBMA), also known as Kennedy syndrome, is a rare X-linked neuromuscular disorder characterized by the progressive degeneration of lower motor neurons in the brainstem and spinal cord. The disease etiology originates from an unstable CAG trinucleotide repeat expansion within the first exon of the androgen receptor (AR) gene, resulting in an elongated polyglutamine tract. This mutation confers a toxic gain-of-function to the androgen receptor protein, which aggregates within the nucleus of motor neurons and muscles in a ligand-dependent manner, necessitating the presence of circulating androgens for phenotypic expression. Clinical presentation typically manifests in adult males during the fourth or fifth decade of life, encompassing proximal muscle weakness, bulbar palsy, fasciculations, and distinct endocrine disturbances such as gynecomastia and reduced fertility, reflecting a state of mild androgen insensitivity. Recent investigations have shifted the paradigm from a purely neuron-centric view to a broader neuromuscular perspective, implicating skeletal muscle as a primary site of toxicity. Current therapeutic options remain largely supportive, though elucidating the molecular cascades of transcriptional dysregulation, mitochondrial dysfunction, and impaired axonal transport has identified novel targets for disease-modifying interventions. This review discusses about molecular advances with clinical observation to delineate the current state of SBMA research
2025-11-19 | Therapeutic impact of leuprorelin acetate on spinal and bulbar muscular atrophy: pre- and post-marketing observational study.
Although leuprorelin acetate, a luteinizing hormone-releasing hormone agonist, has been approved based on short-term clinical trials conducted in Japan, its long-term efficacy on physical function remains unclear. We aimed to evaluate the long-term therapeutic efficacy of leuprorelin acetate using real-world clinical data through a self-controlled trend-shift analysis. The analysis included 91 genetically confirmed patients with spinal and bulbar muscular atrophy, with follow-up data collected before and after treatment initiation. The functional outcomes assessed included the revised amyotrophic lateral sclerosis functional rating scale (ALSFRS-R) and modified Norris scales, grip power, and serum creatinine levels. Leuprorelin acetate significantly slowed disease progression. For instance, the annual ALSFRS-R decline rate improved from approximately 0.5 points pre-treatment to 0.2 points post-treatment. The subgroup analysis supported the potential benefit of early intervention. These findings highlight the value of leveraging patient registries and post-marketing real-world data to evaluate treatment efficacy in slowly progressive diseases, such as SBMA, where traditional randomized controlled trials are often limited by insufficient statistical power to detect therapeutic efficacy. They also underscore the need for innovative methodologies to assess post-approval drug performance, paving the way for improved clinical outcomes for neurodegenerative diseases.
oligonucleotides
2026-05-07 | PGC-1α pathway dysregulation disrupts myofiber specification in a mouse model of SBMA.
Skeletal muscle pathology is a critical but poorly understood contributor to neuromuscular degeneration in spinal and bulbar muscular atrophy (SBMA), a CAG/polyglutamine (polyQ) expansion disorder caused by mutation in the androgen receptor (AR). Using a gene-targeted SBMA mouse model, we applied single-nucleus RNA sequencing to identify a disease-specific population of skeletal muscle myonuclei that replaced normal myonuclear subtypes. This transition was associated with dysregulation of the pathway governed by PGC-1α, a central regulator of myofiber specification and metabolic identity. PGC-1α dysfunction in SBMA muscle was age-, hormone-, and polyQ length-dependent and was partially rescued by subcutaneous delivery of AR-targeted antisense oligonucleotides. Integrated ChIP-seq and RNA-seq analyses revealed that aberrant PGC-1α activity promoted the expression of a distinct set of myofiber specification genes while downregulating those that define healthy Type IIb and Type IIx myonuclei. We propose a model in which this dysfunction arose downstream of polyQ-mediated sequestration of PGC-1α cofactors MEF2, CREB, and CBP, leading to transcriptional reprogramming and cellular dysfunction. These findings implicated PGC-1α dysregulation as a key event linking AR polyQ expansion to skeletal muscle degeneration and suggested a shared mechanism for polyQ-mediated muscle pathology across related neurodegenerative diseases.
2026-03-28 | Restoring early postnatal synaptic dysregulation rescues motor neuron degeneration in a mouse model of Spinal and Bulbar Muscular Atrophy.
Spinal and bulbar muscular atrophy (SBMA) is an adult-onset neurodegenerative disorder caused by expansion of a polyglutamine tract in the androgen receptor (AR). Here, we show that polyglutamine-expanded AR accumulates in the nucleus of motor neurons and induces aberrant upregulation of glutamatergic synaptic genes through dysfunction of the master transcriptional repressor REST during early postnatal development in a mouse model of SBMA (AR-97Q mice). Reducing mutant AR or restoring REST function using antisense oligonucleotides during the neonatal period attenuated the upregulation of glutamatergic synaptic genes and ameliorated the disease phenotype and histopathology in AR-97Q mice. Furthermore, we observed increased calcium activity in induced pluripotent stem cell-derived motor neurons from SBMA patients compared to those from healthy controls, reflecting neuronal hyperexcitability. Late-onset neurodegeneration in SBMA is attributable to early synaptic defects and the resulting hyperexcitability of motor neurons, which may represent therapeutic targets.
2026-01-19 | An acyclic nucleic acid-modified siRNA targeting CAG expansions for polyglutamine disease treatment.
Polyglutamine (polyQ) diseases are inherited neurological disorders caused by an expansion of the cytosine-adenine-guanine (CAG) repeat in the causative genes. These include Huntington's disease, spinal and bulbar muscular atrophy (SBMA), and spinocerebellar ataxias (SCAs). Clinical trials have been conducted using nucleic acid therapeutics to silence the causative gene for these diseases, but none have been approved for use. Furthermore, while oligonucleotides targeting the CAG repeats are an attractive therapeutic option, concomitant silencing of the wild-type allele with normal CAG repeats can result in neuronal dysfunction. In this study, we developed an acyclic serinol nucleic acid (SNA)-modified small interfering RNA (siRNA) targeting CAG repeats. We also evaluated the safety and efficacy of the siRNA in different mouse models of polyQ diseases. Intracerebroventricularly administered siRNA was widely distributed throughout the central nervous system, where it selectively silenced the alleles encoding polyQ proteins without affecting their wild-type counterparts. Consequently, the intranuclear aggregation of polyQ proteins was reduced in mouse models of SBMA and SCA type 3. The siRNA attenuated neuromuscular degeneration and improved the lifespan and motor function of the SBMA mice. These findings suggest that SNA-modified siRNAs targeting CAG repeats represent a promising approach for treating polyQ diseases.
2025-08-28 | Peripherally administered androgen receptor-targeted antisense oligonucleotide rescues spinal pathology in a murine SBMA model.
Degeneration of the neuromuscular system is a characteristic feature of spinal and bulbar muscular atrophy (SBMA), a CAG/polyglutamine (polyQ) expansion disorder caused by mutation in the androgen receptor (AR). Using a gene-targeted mouse model of SBMA, AR113Q mice, we demonstrate age-dependent degeneration of the neuromuscular system that initially manifests with muscle weakness and atrophy and progresses to include denervation of neuromuscular junctions and lower motor neuron soma atrophy. Using this model, we tested the hypothesis that therapeutic intervention targeting skeletal muscle during this period of disease progression arrests degeneration of the neuromuscular system. To accomplish this, AR-targeted antisense oligonucleotides were administered subcutaneously to symptomatic AR113Q mice to reduce expression of polyQ AR in peripheral tissues but not in the spinal cord. This intervention rescued muscle atrophy, neuromuscular junction innervation, lower motor neuron soma size, and survival in aged AR113Q mice. Single-nucleus RNA sequencing revealed age-dependent transcriptional changes in the AR113Q spinal cord during disease progression, which were mitigated by peripheral AR gene silencing. Our findings underscore the intricate interplay between peripheral tissues and the central nervous system in SBMA and emphasize the therapeutic effectiveness of peripheral gene knockdown in symptomatic disease.
2025-08-14 | Neuroaxonal Degeneration as a Converging Mechanism in Motor Neuron Diseases (MNDs): Molecular Insights into RNA Dysregulation and Emerging Therapeutic Targets.
Motor Neuron Diseases (MNDs) such as Amyotrophic Lateral Sclerosis (ALS), Primary Lateral Sclerosis (PLS), Hereditary Spastic Paraplegia (HSP), Spinal Muscular Atrophy with Respiratory Distress Type 1 (SMARD1), Multisystem Proteinopathy (MSP), Spinal and Bulbar Muscular Atrophy (SBMA), and ALS associated to Frontotemporal Dementia (ALS-FTD), have traditionally been studied as distinct entities, each one with unique genetic and clinical characteristics. However, emerging research reveals that these seemingly disparate conditions converge on shared molecular mechanisms that drive progressive neuroaxonal degeneration. This narrative review addresses a critical gap in the field by synthesizing the most recent findings into a comprehensive, cross-disease mechanisms framework. By integrating insights into RNA dysregulation, protein misfolding, mitochondrial dysfunction, DNA damage, kinase signaling, axonal transport failure, and immune activation, we highlight how these converging pathways create a common pathogenic landscape across MNDs. Importantly, this perspective not only reframes MNDs as interconnected neurodegenerative models but also identifies shared therapeutic targets and emerging strategies, including antisense oligonucleotides, autophagy modulators, kinase inhibitors, and immunotherapies that transcend individual disease boundaries. The diagnostic and prognostic potential of Neurofilament Light Chain (NfL) biomarkers is also emphasized. By shifting focus from gene-specific to mechanism-based approaches, this paper offers a much-needed roadmap for advancing both research and clinical management in MNDs, paving the way for cross-disease therapeutic innovations.
proteins
2025-07-18 | Targeting androgen receptor stability and degradation: approaches for developing a therapy for spinal and bulbar muscular atrophy.
Conformational changes of proteins can occur due to mutations or stress conditions, altering their functionality through loss of physiological or gain of pathological function. A Protein Quality Control (PQC) system exists in cells to deal with the accumulation of misfolded proteins and aggregates, comprising a network of chaperones and degradative pathways to refold or remove the aberrant proteins. Protein misfolding and PQC system impairment lead to a broad range of diseases, including neurodegenerative and neuromuscular disorders, among them spinal and bulbar muscular atrophy (SBMA). SBMA is a neuromuscular disorder caused by a polyglutamine expansion (polyQ) in the androgen receptor (AR) protein. Expanded AR (ARexp) is highly prone to misfolding and aggregation, leading to its accumulation in affected tissues. Here, we summarise the dynamics that control AR protein stability and its degradation in physiological conditions. Next, we recapitulate the current knowledge of the molecular mechanisms of SBMA pathogenesis involving the PQC system. Finally, we provide an overview of promising approaches to SBMA intervention involving the modulation of PQC system functions to reduce ARexp accumulation and its toxic effects in affected cells.
2023-06-05 | X-linked SBMA model mice display relevant non-neurological phenotypes and their expression of mutant androgen receptor protein in motor neurons is not required for neuromuscular disease.
X-linked spinal and bulbar muscular atrophy (SBMA; Kennedy's disease) is a rare neuromuscular disorder characterized by adult-onset proximal muscle weakness and lower motor neuron degeneration. SBMA was the first human disease found to be caused by a repeat expansion mutation, as affected patients possess an expanded tract of CAG repeats, encoding polyglutamine, in the androgen receptor (AR) gene. We previously developed a conditional BAC fxAR121 transgenic mouse model of SBMA and used it to define a primary role for skeletal muscle expression of polyglutamine-expanded AR in causing the motor neuron degeneration. Here we sought to extend our understanding of SBMA disease pathophysiology and cellular basis by detailed examination and directed experimentation with the BAC fxAR121 mice. First, we evaluated BAC fxAR121 mice for non-neurological disease phenotypes recently described in human SBMA patients, and documented prominent non-alcoholic fatty liver disease, cardiomegaly, and ventricular heart wall thinning in aged male BAC fxAR121 mice. Our discovery of significant hepatic and cardiac abnormalities in SBMA mice underscores the need to evaluate human SBMA patients for signs of liver and heart disease. To directly examine the contribution of motor neuron-expressed polyQ-AR protein to SBMA neurodegeneration, we crossed BAC fxAR121 mice with two different lines of transgenic mice expressing Cre recombinase in motor neurons, and after updating characterization of SBMA phenotypes in our current BAC fxAR121 colony, we found that excision of mutant AR from motor neurons did not rescue neuromuscular or systemic disease. These findings further validate a primary role for skeletal muscle as the driver of SBMA motor neuronopathy and indicate that therapies being developed to treat patients should be delivered peripherally.
2022-10-06 | The role of ubiquitination in spinal and bulbar muscular atrophy
Spinal and bulbar muscular atrophy (SBMA) is a neurodegenerative and neuromuscular genetic disease caused by the expansion of a polyglutamine-encoding CAG tract in the androgen receptor (AR) gene. The AR is an important transcriptional regulator of the nuclear hormone receptor superfamily; its levels are regulated in many ways including by ubiquitin-dependent degradation. Ubiquitination is a post-translational modification (PTM) which plays a key role in both AR transcriptional activity and its degradation. Moreover, the ubiquitin-proteasome system (UPS) is a fundamental component of cellular functioning and has been implicated in diseases of protein misfolding and aggregation, including polyglutamine (polyQ) repeat expansion diseases such as Huntington’s disease and SBMA. In this review, we discuss the details of the UPS system, its functions and regulation, and the role of AR ubiquitination and UPS components in SBMA. We also discuss aspects of the UPS that may be manipulated for therapeutic effect in SBMA.
2022-01-18 | Inhibition of Polyglutamine Misfolding with D-Enantiomeric Peptides Identified by Mirror Image Phage Display Selection
Nine heritable diseases are known that are caused by unphysiologically elongated polyglutamine tracts in human proteins leading to misfolding, aggregation and neurodegeneration. Current therapeutic strategies include efforts to inhibit the expression of the respective gene coding for the polyglutamine-containing proteins. There are, however, concerns that this may interfere with the physiological function of the respective protein. We aim to stabilize the protein's native conformation by D-enantiomeric peptide ligands to prevent misfolding and aggregation, shift the equilibrium between aggregates and monomers towards monomers and dissolve already existing aggregates into non-toxic and functional monomers. Here, we performed a mirror image phage display selection on the polyglutamine containing a fragment of the androgen receptor. An elongated polyglutamine tract in the androgen receptor causes spinal and bulbar muscular atrophy (SBMA). The selected D-enantiomeric peptides were tested for their ability to inhibit polyglutamine-induced androgen receptor aggregation. We identified D-enantiomeric peptide QF2D-2 (sqsqwstpqGkwshwprrr) as the most promising candidate. It binds to an androgen receptor fragment with 46 consecutive glutamine residues and decelerates its aggregation, even in seeded experiments. Therefore, QF2D-2 may be a promising drug candidate for SBMA treatment or even for all nine heritable polyglutamine diseases, since its aggregation-inhibiting property was shown also for a more general polyglutamine target.
2021-10-04 | ClC-2-like Chloride Current Alterations in a Cell Model of Spinal and Bulbar Muscular Atrophy, a Polyglutamine Disease.
Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by expansions of a polyglutamine (polyQ) tract in the androgen receptor (AR) gene. SBMA is associated with the progressive loss of lower motor neurons, together with muscle weakness and atrophy. PolyQ-AR is converted to a toxic species upon binding to its natural ligands, testosterone, and dihydrotestosterone (DHT). Our previous patch-clamp studies on a motor neuron-derived cell model of SBMA showed alterations in voltage-gated ion currents. Here, we identified and characterized chloride currents most likely belonging to the chloride channel-2 (ClC-2) subfamily, which showed significantly increased amplitudes in the SBMA cells. The treatment with the pituitary adenylyl cyclase-activating polypeptide (PACAP), a neuropeptide with a proven protective effect in a mouse model of SBMA, recovered chloride channel current alterations in SBMA cells. These observations suggest that the CIC-2 currents are affected in SBMA, an alteration that may contribute and potentially determine the pathophysiology of the disease.
gene therapies
2025-12-04 | Bone Fragility and Fracture Characteristics in Patients With Spinal and Bulbar Muscular Atrophy.
Spinal and bulbar muscular atrophy (SBMA) is a hereditary neuromuscular disorder linked to androgen receptor gene mutations, often associated with metabolic abnormalities. We aimed to investigate the incidence of fragility fractures and the underlying mechanisms in SBMA. Consecutive genetically confirmed SBMA patients and healthy controls (HC) were enrolled. We surveyed fracture history and assessed motor function, bone metabolism markers, and bone mineral density (BMD) using dual-energy X-ray absorptiometry. Longitudinal BMD changes were also analyzed between SBMA patients and HC. A total of 109 SBMA patients and 21 HC were included. Fragility fractures in SBMA patients were mainly observed in cortical bone-dominant regions. Their lower limb BMD was significantly reduced (SBMA 1.10 g/cm, HC 1.19 g/cm; p < 0.05) and further decreased overtime. Despite low bone resorption markers, bone formation markers showed no difference between the groups, suggesting that SBMA patients exhibit characteristics of low turnover osteoporosis. Serum 25-hydroxyvitamin D levels were lower in SBMA patients than in HC (15.4 ng/mL vs. 19.4 ng/mL; p < 0.01). Longitudinal analysis revealed that SBMA patients had a higher incidence of fragility fractures than HC (log-rank test, p < 0.05), with the first fragility fracture occurring 10 years after the onset of muscle weakness. Low baseline BMD was a predictor of fragility fractures (adjusted OR = 0.32; 95% CI: 0.17-0.60; p < 0.05). SBMA patients have a high fragility fracture incidence, particularly in cortical bone, with a progressive BMD decrease. Low bone turnover and vitamin D deficiency are associated with these fractures.
2025-09-17 | Conserved Aberrant Developmental Trajectories of Human and Mouse SBMA Motor Neurons
Spinal bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by a polyglutamine repeat expansion in the androgen receptor gene (AR). Lower motor neuron loss is a key feature of the disease, yet it remains poorly understood why these cells are affected. The transcriptional mechanisms underlying SBMA pathogenesis and how these evolve across developmental and disease stages remains incompletely defined. To elucidate the molecular mechanisms underlying motor neuron loss in SBMA, we first performed transcriptomic profiling of both induced pluripotent stem cell derived motor neurons (iPSC-MNs) generated from SBMA patients and laser-captured micro dissected motor neurons (LCM-MNs) from symptomatic AR100 SBMA mice. We compared differential gene expression between the two models to identify shared transcriptional programs. To address the temporal progression of molecular changes we conducted profiling at key stages of motor neurogenesis in the developing iPSC-MNs and at pre-symptomatic and end- stage disease in AR100 SBMA mice to elucidate the emergence of the transcriptional phenotype and the trajectory of the gene expression changes. We found significant transcriptional convergence between these two species. Notably, shared dysregulation was observed in pathways related to the spliceosome, the cell cycle and mitochondrial function. These transcriptional alterations emerged early in motor neurogenesis suggesting a developmental component to SBMA. Further in AR100 LCM-MNs we also observed disruption of mitochondrial and DNA damage repair pathways from pre-symptomatic to end stage disease. This study identifies conserved pathogenic mechanisms across two SBMA model systems and provides crucial insights into the molecular basis and temporal dynamics of SBMA progression which may help identify potential therapeutic targets for SBMA.
2025-02-07 | Therapeutic targeting of the polyglutamine androgen receptor in Spinal and Bulbar Muscular Atrophy.
Spinal and Bulbar Muscular Atrophy (SBMA) is a slowly progressive, X-linked, and sex-limited degenerative disorder affecting lower motor neurons and skeletal muscle which lacks disease-modifying therapies. This disease is caused by a CAG/polyglutamine (polyQ) tract expansion in the androgen receptor (AR) gene, and its pathogenesis is driven by toxic gain-of-function mechanisms. Affected men develop proximal limb and bulbar muscle weakness along with signs of partial androgen insensitivity. Toxicity of the polyQ AR is mediated by protein misfolding and nuclear translocation that follow ligand binding, resulting in the disruption of downstream homeostatic mechanisms. This review highlights what is known about disease pathogenesis and how this has been leveraged to test potential therapeutic approaches. The focus is on strategies that alleviate polyQ AR toxicity in SBMA, including those that alter AR function, diminish the expression of the encoding gene, or promote clearance of the misfolded, mutant protein. We discuss emerging strategies to mitigate polyQ AR toxicity, including gene editing, RNA targeted therapies, and efforts to harness proteostatic mechanisms. These promising approaches are discussed in the context of challenges for drug discovery efforts that are faced when attempting to treat a rare and slowly progressive neurodegenerative disorder.
2024-10-09 | CRISPR-Cas9 guided RNA-based model for the silencing of spinal bulbar muscular atrophy: A functional genetic disorder.
This study explores a novel therapeutic approach for spinal bulbar muscular atrophy (SBMA), a neurodegenerative disorder caused by a mutation in the Androgen Receptor (AR) gene. The aim is to investigate the potential of CRISPR-Cas9 technology in targeting the mutant AR gene to inhibit its production. The objectives include assessing the accuracy and efficacy of CRISPR-Cas9 guided RNAs in silencing the mutant gene and evaluating the feasibility of this approach as a treatment for SBMA. Computational and in-silico approaches are used to evaluate the feasibility of using CRISPR-Cas9 technology for treating SBMA. Computational analysis is used to design CRISPR-Cas9 guided RNAs targeting the mutant AR gene, assessing their on-target and off-target scores, GC content, and structural accuracy. In-silico simulations predict the potential therapeutic outcomes of the CRISPR-Cas9 approach in an artificial environment. Three guided RNA (gRNA) sequences were designed using the CHOPCHOP tool, targeting specific regions of the AR gene with high efficiency and 100% match. These gRNAs demonstrated effective targeting with minimal off-target scores and optimal GC content. Additionally, lentiCRISPR v2 plasmids were designed for the delivery of CRISPR materials, enabling high-efficiency multiplex genome editing of the AR gene. Thermodynamic ensemble predictions indicated favorable secondary structure stability of the designed gRNAs, further supporting their suitability for gene editing. The evaluation of designed gRNAs confirmed their strong binding ability to the target sequences, validating their potential as effective tools for genome editing. The study highlights the potential of CRISPR-Cas9 technology for targeting the Androgen Receptor gene associated with spinal bulbar muscular atrophy (SBMA). The findings support the feasibility of this approach for gene editing and suggest further exploration in preclinical and clinical settings. Recommendations include continued research to optimize CRISPR-Cas9 delivery methods and enhance specificity for therapeutic applications in SBMA.
2024-04-25 | Precise editing of pathogenic nucleotide repeat expansions in iPSCs using paired prime editor
Nucleotide repeat expansion disorders, a group of genetic diseases characterized by the expansion of specific DNA sequences, pose significant challenges to treatment and therapy development. Here, we present a precise and programmable method called prime editor-mediated correction of nucleotide repeat expansion (PE-CORE) for correcting pathogenic nucleotide repeat expansion. PE-CORE leverages a prime editor and paired pegRNAs to achieve targeted correction of repeat sequences. We demonstrate the effectiveness of PE-CORE in HEK293T cells and patient-derived induced pluripotent stem cells (iPSCs). Specifically, we focus on spinal and bulbar muscular atrophy and spinocerebellar ataxia type, two diseases associated with nucleotide repeat expansion. Our results demonstrate the successful correction of pathogenic expansions in iPSCs and subsequent differentiation into motor neurons. Specifically, we detect distinct downshifts in the size of both the mRNA and protein, confirming the functional correction of the iPSC-derived motor neurons. These findings highlight PE-CORE as a precision tool for addressing the intricate challenges of nucleotide repeat expansion disorders, paving the way for targeted therapies and potential clinical applications.
other
2025-11-24 | Exosome-rich mesenchymal stem cell secretome improves strength in patients with amyotrophic lateral sclerosis, Kennedy disease, congenital myasthenic syndrome and Lewy body dementia.
Amyotrophic lateral sclerosis (ALS), Lewy Body dementia (LBD), Kennedy disease (KD), and Congenital Myasthenic Syndrome (CMS) are progressive motor disorders for which no disease modifying treatment exists. ALS and LBD are uniformly, and often rapidly, fatal. No treatment of any kind has ever resulted in actual improvement for ALS patients; the best that has been achieved is minor slowing of their progression. Forty-one preclinical studies of intra-nasal instillation of mesenchymal stem cell exosomes have, however, demonstrated complete safety and efficacy for models of a variety of neurocognitive and motor disorders. We hypothesized that intranasal exosomes treatment in humans would be completely safe and also effective for the treatment of motor disorders such as ALS, LBD, KD and CMS. 18 patients with ALS, Kennedy Disease, Congenital Myasthenic Syndrome, or Lewy Body Dementia had 32 AlloEx Exosome® treatments to assess safety, attenuation of disease, and increase in strength and motor function. The study was conducted under the clinical trial NCT07105371 found at clinicaltrials.gov/study/NCT07105371. There were no adverse events of any kind reported among these treatments. All patients, except for one, achieved some degree of clinical and strength improvement; the longest improvement was recorded at the 6-month follow-up. Intranasally-instilled AlloEx Exosomes® are completely safe, attenuate progression, and improve strength in ALS, Kennedy Disease, CMS, and LBD.
2025-09-04 | Effective and safe use of alirocumab in spinal and bulbar muscular atrophy with high cardiovascular risk: a case report.
BACKGROUND: Spinal and bulbar muscular atrophy (SBMA) is a rare X-linked neuromuscular disorder characterized by progressive muscle weakness and endocrine abnormalities. Beyond its classic neurological presentation, SBMA is increasingly associated with metabolic and cardiovascular comorbidities, including dyslipidemia and insulin resistance. CASE REPORT: We present the case of a 54-year-old male with genetically confirmed SBMA and high cardiovascular risk, in whom statins and ezetimibe were contraindicated due to persistently elevated creatine kinase levels and underlying muscle involvement. Coronary CT angiography revealed subclinical atherosclerosis. Alirocumab, a PCSK9 inhibitor, was initiated at a dose of 150 mg every 2 weeks. After six months, LDL cholesterol was reduced by 54.9% without adverse effects or functional decline, and CK levels remained stable. CONCLUSIONS: This case highlights the potential role of PCSK9 inhibitors as a safe and effective lipid-lowering option in patients with neuromuscular disorders at high cardiovascular risk, for whom traditional therapies are not feasible. It also highlights the importance of integrated cardiovascular care in managing multisystem diseases, such as SBMA. https://www.europeanreview.org/wp/wp-content/uploads/Graphical-Abstract-2-1.jpg.
2025-08-05 | Spinal and bulbar muscular atrophy with hand tremors and chronic limb weakness, Kennedy disease.
Spinal and bulbar muscular atrophy (SBMA) is an X-linked neuromuscular disorder primarily affecting adult males due to the expansion of CAG repeats in the androgen receptor gene. It manifests as progressive lower motor neuropathy and androgen deficiency. A Japanese man in his late 50s presented with gradually progressive muscle weakness over 6 years. Examination revealed muscle weakness and atrophy in upper and lower limbs, decreased deep tendon reflexes, involuntary facial movements, bilateral finger tremors, tongue atrophy, fasciculations and bilateral gynaecomastia. Blood tests indicated elevated creatine kinase and mild hepatic dysfunction. Nerve conduction studies showed decreased sensory nerve action potentials, and electromyography demonstrated neurogenic changes. Genetic testing confirmed SBMA with 47 CAG repeats despite no family history. Treatment included leuprorelin acetate and rehabilitation using a wearable cyborg hybrid-assistive limb. As SBMA progresses slowly and symptoms like hand tremors and decreased serum creatinine precede significant weakness, early recognition is critical for diagnosis.
2024-06-12 | A case of SBMA presenting with myasthenic syndrome limited to a dropped head
Abstract A 76‐year‐old man with spinal and bulbar muscular atrophy (SBMA) developed an acute course of the dropped head with diurnal fluctuations that worsened in the evening. He was diagnosed with myasthenic syndrome based on a decreased response to repeated stimulation, as well as increased jitter and blocking on single‐fiber electromyography, indicating disturbed neuromuscular transmission. Dropped head symptom was successfully alleviated and maintained by immunotherapy. Although limited reports are available on SBMA cases accompanied by myasthenic syndrome and on the clinical impact of impaired neuromuscular transmission on SBMA, myasthenic syndrome may be a common condition and even a part of the phenotypic spectrum of SBMA. To our knowledge, this is the first case of SBMA comorbid with myasthenic syndrome limited to the dropped head.
2024-01-12 | Dysregulated synaptic gene expression in oligodendrocytes of spinal and bulbar muscular atrophy
Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by an expanded CAG repeat in the androgen receptor (AR) gene. To elucidate the cell type-specific temporal gene expression in SBMA, we performed single-nucleus RNA sequencing on the spinal cords of AR-97Q mice. Among all cell types, oligodendrocytes (OLs) had the highest number of differentially expressed genes before disease onset. Analysis of OL clusters suggested that pathways associated with cation channels and synaptic function were activated before disease onset, with increased output from OLs to neurons in AR-97Q mice compared to wild-type mice. These changes in the early stages were abrogated in the advanced stages. An OL cell model of SBMA showed phenotypes similar to those of AR-97Q mice at early stages, such as increased transcriptional changes in synapse organization. Our results indicate that the dysregulation of cell-to-cell communication has a major impact on the early pathology of SBMA and is a potential therapeutic target for SBMA.
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Drug Discovery Landscape
5 orphan drug designations for Kennedy disease.
5 orphan drug designations for Kennedy disease.
Drug | Therapy type | Regulator | Orphan designation | Approval | Sponsor |
|---|---|---|---|---|---|
3-(5-(2-Hydroxy-2-methylpropoxy)-6-methylpyrazin-2-yl)-1H-indole-7-carbonitrile | small molecules | EMA | 2024-10-11 | — | FGK Representative Service GmbH |
Insulin-like Growth Factor-1 | proteins | FDA | 2023-06-21 | — | Sarcomed AB |
geranylgeranylacetone | small molecules | FDA | 2020-06-26 | — | RNR BioMedical Inc. |
(1E,6E)-1,7-bis(3,4-dimethoxyphenyl)-4-cyclobutylmethyl-1,6-heptadiene-3,5-dione | small molecules | EMA | 2016-04-28 | — | ICON Clinical Research Limited |
1E,6E)-1,7-Bis(3,4-dimethoxyphenyl)-4-cyclobutylmethyl-1,6-heptadiene-3,5-dione or [(1E, 4Z,6E)-4-(cyclobutylmethyl)-1,7-bis(3,4-dimethoxyphenyl)-5-hydroxyhepta-1,4,6-trien-3-one] | small molecules | FDA | 2016-02-17 | — | AnnJi Pharmaceutical Co. Ltd. |
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