Blocking somatic repeat expansion and lowering huntingtin by RNAi synergize to attenuate Huntington's disease pathogenesis in mice.

Emerging Pharmacological Therapies for Huntington's Disease: Translational Insights from Recent Clinical Trials.

Huntington's disease [HD] is a progressive, autosomal dominant neurodegenerative disorder caused by a pathogenic CAG repeat expansion in the HTT gene, resulting in mutant huntingtin [mHTT] protein accumulation, neuronal dysfunction, and selective neurodegeneration. Current pharmacological management remains largely symptomatic, with no approved therapies capable of modifying disease progression. In recent years, however, significant advances in molecular neuroscience and translational medicine have accelerated the development of disease-modifying strategies targeting the underlying pathogenic mechanisms of HD. This review synthesizes emerging pharmacological therapies with a particular focus on insights derived from recent and ongoing clinical trials. Key therapeutic approaches discussed include gene-silencing technologies such as antisense oligonucleotides, RNA interference, and CRISPRCas9- based strategies, as well as small-molecule modulators targeting mutant huntingtin aggregation, proteostasis, autophagy, mitochondrial dysfunction, and neuroinflammation. In addition, advances in symptomatic treatments addressing motor, cognitive, and psychiatric manifestations are reviewed. The article critically examines translational challenges encountered in clinical development, including blood-brain barrier penetration, allele selectivity, dosing paradigms, patient heterogeneity, biomarker integration, and ethical considerations associated with irreversible genetic interventions. Lessons learned from both successful and failed trials highlight the importance of precision medicine approaches, biomarker-guided trial designs, and combination therapies targeting multiple pathogenic pathways. Collectively, this review provides an updated and clinically relevant overview of the evolving HD therapeutic landscape and outlines key considerations for translating molecular advances into effective and safe pharmacological interventions.

CRISPR-Cas9-based therapies for Huntington’s disease and Friedreich’s ataxia: mechanisms, advances, and future perspectives

Hepatic huntingtin loss drives an acute phase response and liver injury in multiple mouse models

Multiple therapeutic strategies are being developed to slow Huntington’s disease (HD) progression through targeted reduction of huntingtin (HTT) protein or mRNA. Despite HTT’s discovery over 30 years ago, its cellular functions remain incompletely understood, and the long-term consequences of HTT-lowering therapies remain unclear. We previously demonstrated that hepatic HTT loss in mice disrupts hepatocyte zonation and metabolism. Here, we investigate the physiological consequences of hepatic Htt loss. Across multiple models of Htt loss—including ubiquitous and hepatocyte-specific genetic knockouts and a therapeutically relevant Htt-targeting siRNA—there was elevated expression of IL-6/STAT3-driven acute phase response genes. Single-nucleus RNA sequencing reveals a zonal pattern of hepatocyte stress, most highly upregulated in pericentral hepatocytes, and identifies a distinct pericentral cluster of stressed hepatocytes that was enriched ∼9.6-fold following Htt knockout. Histological examination reveals that Htt loss results in increased hepatic pathology, including hepatic intranuclear inclusions, apoptosis, and necrosis, as well as prevalence of granulomas. Transcriptomic analysis reveals significant upregulation of metallothionein genes following Htt loss, as confirmed by elevated plasma metallothionein-1 (MT1) levels in knockout mice. These findings underscore important safety considerations for HTT-lowering therapies and suggest candidate biomarkers for monitoring hepatic off-target effects in clinical trials.

In vivo CRISPR base editing for treatment of Huntington's disease.

Huntington's disease (HD) is a fatal neurodegenerative disorder caused by an expanded CAG repeat within exon 1 of the huntingtin (HTT) gene, resulting in a mutant protein that drives neuronal dysfunction and loss. A key event in the pathogenesis of HD is proteolytic cleavage of mutant HTT, which generates aggregation-prone N-terminal fragments that contribute to toxicity. Strategies that prevent this process thus hold therapeutic potential. Here we develop CRISPR base editors that generate proteolysis-resistant HTT isoforms by disrupting the splice acceptor of HTT exon 13, an exon that encodes critical proteolytic cleavage sites implicated in N-terminal fragment production. When delivered to the striatum of an HD rodent model, these editors reduced HTT fragment formation, decreased aggregation, improved functional deficits and attenuated brain atrophy. Collectively, these results demonstrate the potential of base editing and splice-site modulation to mitigate mutant HTT toxicity in HD.

Structure-function dissection of huntingtin exon 1 identifies a PRD-driven modifier of neuronal toxicity in Huntington’s disease

The Huntingtin gene (HTT) contains a conserved, yet expandable CAG repeat within exon 1. While the pathogenic expansion in Huntington’s Disease (HD) is well studied, the role of surrounding domains remains unclear. Using genome-edited mini-organoids and neurons, we dissected HTT exon 1 and found species-specific toxicity: the human variant caused more severe deficits than the mouse. Swapping the proline-rich domain (PRD) - the most divergent region - revealed its key role: the mouse PRD mitigated, while the human PRD worsened neuronal phenotypes. Omics profiling showed that pathogenic human exon 1 induced broad protein dysregulation, largely reversed by mouse PRD replacement. Bioinformatics implicated the actin cytoskeleton and transcriptional coactivator MKL2/MRTFB. We validated MKL2/MRTFB dysregulation in HD models and showed that restoring its expression rescued neuronal abnormalities. These findings highlight the PRD’s contribution to HD toxicity and point to MKL2/MRTFB and the cytoskeleton as candidate mediators.

Huntington's disease in the era of somatic instability, biomarkers, and targeted therapies: A narrative review.

Huntington's disease (HD) is a progressive, autosomal dominant neurodegenerative disorder caused by cytosine-adenine-guanine (CAG) trinucleotide repeat expansion in the huntingtin gene (HTT), resulting in mutant huntingtin (mHTT) with toxic gain-of-function and partial loss of normal huntingtin function. This narrative review summarizes recent advances in genetics, pathophysiology, clinical features, diagnostic assessment, biomarkers, and therapeutic development. Genetic testing demonstrating an expanded HTT CAG repeat is the definitive diagnostic test and should be interpreted with genetic counseling and attention to allele categories. Pathophysiologically, HD involves CAG instability, age-dependent somatic expansion in vulnerable neurons, transcriptional dysregulation, proteostasis failure, mitochondrial dysfunction, excitotoxicity, and neuroinflammation, leading primarily to degeneration of striatal medium spiny neurons and later cortical involvement. Clinically, HD can begin from juvenile to late-adult life and manifests with motor, cognitive, psychiatric, and behavioral symptoms that evolve from premanifest biological change to functional decline. Current clinical care relies on symptom-directed treatment, whereas quantitative neuroimaging, cerebrospinal fluid biomarkers are mainly used for research and trial enrichment. Symptomatic management includes vesicular monoamine transporter type 2 inhibitors, antipsychotics, rehabilitation, nutritional support, and multidisciplinary care. Emerging disease-modifying approaches include HTT-lowering, somatic expansion inhibition, and gene-based therapies, but efficacy depends on target selectivity, timing, delivery route, dose, and patient selection.