Connor J. Lewis

GM1 gangliosidosis is an inherited, progressively neurodegenerative lysosomal storage disorder with no approved therapy. We report 5-year safety and 3-year clinical, biochemical, and neuroimaging efficacy outcomes following expanded-access intravenous AAV9-GLB1 gene therapy in GT01, a 6-10-year-old female with juvenile-onset GM1 gangliosidosis. During participation in a natural history study before gene transfer, GT01 developed seizures, dysarthria, loss of ambulation, and progressive neurodegeneration. She received a single intravenous administration of AAV9-GLB1 at 1.5×10 ¹³ vector genomes per kilogram of body weight. Early improvements included the resolution of dysphagia, increased interactions with others, assisted ambulation, and gains in specific domains of adaptive functioning. She was seizure-free without anti-epileptic drugs 18 months post dosing with sustained seizure freedom at the study completion. Cerebrospinal fluid concentrations of GM1 ganglioside and H3N2b (a pentasaccharide biomarker indicative of biochemical improvement in this disorder) concentrations decreased by 50% and β-galactosidase reached normal activity. Brain, thalamic, and net fiber tract volume assessed by differential tractography increased and ventriculomegaly improved three years post-dosing. These results indicate that meaningful benefit can be achieved even in advanced neurologic disease.

Due to shared ß-hexosamindase A deficiencies and significant clinical overlap, the predominating subtypes of late-onset GM2 gangliosidosis, late-onset Tay-Sachs (LOTS) and late-onset Sandhoff disease (LOSD) have been considered essentially indistinguishable. However, growing evidence supports several distinctions between the two entities. We highlight these distinctions through the cross-sectional evaluation of 27 (21 LOTS and 6 LOSD) late-onset GM2 gangliosidosis participants. Study protocol included physical examinations, assessments of gait, balance, muscle strength, ataxia, and nerve conduction velocities, and brain magnetic resonance imaging. Lower limb weakness and later development of upper limb weakness was highly prevalent in both diseases. Accompanying gait disturbances, balance issues, and dysmetria were also prevalent in both cohorts. Strength evaluations showed weakness in both the LOTS and LOSD cohorts compared to controls primarily impacting extensor muscles. In contrast, BARS scores for dysarthria and oculomotor dysfunction were present and heterogenous in LOTS participants and absent in LOSD participants. Twenty-four percent of LOTS participants and none of the LOSD participants had a history of neuropsychiatric symptoms. Cerebellar volume including lobules V and VI were lower in LOTS compared to LOSD and normative data. However, severe length-dependent sensory neuropathy was present in all LOSD participants but not in LOTS participants. The finding of lower cerebellar volume in LOTS suggests the distinctive features of the LOTS phenotype are related to cerebellar dysfunction. However, the cause of the phenotypic differences between LOTS and LOSD remains a mystery, and the molecular and biochemical basis for the dichotomy requires further investigation.

Background: GM1 gangliosidosis is an inherited, progressive, and fatal neurodegenerative lysosomal storage disorder with no approved treatment. In this study, we present the first use of MRI-based predicted brain age in GM1 gangliosidosis aimed at assessing the neuronal degeneration in this cohort. Methods: We calculated a predicted brain age and Brain Structures Age Gap Estimation (BSAGE) for 81 MRI scans from 41 Type II (26 juvenile and 15 late-infantile) GM1 gangliosidosis patients and 897 MRI scans from 556 neurotypical controls (NC) utilizing BrainStructuresAges , a machine learning MRI analysis pipeline. Results: NC shows whole-brain aging at a rate of 0.83 per chronological year compared with 1.57 in juvenile GM1 patients and 12.25 in late-infantile GM1 patients. Accelerated and distinct brain aging is observed throughout midbrain structures, including the thalamus and caudate nucleus, hindbrain structures, including the cerebellum and brainstem, and the ventricles in juvenile and late-infantile GM1 patients compared to NC, reflecting neurodegeneration from disease progression. Cross-sectional evaluations of BSAGE for the whole brain show an average BSAGE = 35.50 years in the late-infantile cohort, 21.19 years in the juvenile cohort, and 0.03 years in NC. Predicted brain age and BSAGE both correlate with cross-sectional and longitudinal clinical outcome assessments. Conclusions: Predicted brain age accurately reflects the neurodegenerative clinical trajectories of the Type II GM1 disease subtypes. Correlations with clinical outcome assessments indicate evaluations of predicted brain aging may be an important candidate neuroimaging outcome measure for clinical trials in GM1 gangliosidosis.

GM1 gangliosidosis, caused by biallelic variants in GLB1, results from deficiency of lysosomal β-galactosidase, which degrades GM1 ganglioside. This fatal neurodegenerative disease currently has no effective therapy. In a phase 1-2, open-label, dose-escalation study, we assessed immunosuppression and a single intravenous infusion of adeno-associated virus serotype 9 (AAV9) encoding β-galactosidase in children with type II GM1 gangliosidosis with late-infantile or juvenile onset. The primary end point was safety. Secondary end points included changes from baseline in the cerebrospinal fluid (CSF) GM1 ganglioside concentration and β-galactosidase activity, clinical assessments (including the Clinical Global Impression-Improvement [CGI-I] score, assessed on a scale from 1 [very much improved] to 7 [very much worse]), and neuroimaging patterns. Nine participants were enrolled. Over a 3-year period, 124 adverse events occurred, 30 of which (8 gastrointestinal events, 21 laboratory abnormalities associated with inflammation, and 1 tachycardia event) were deemed by the investigator as being possibly, probably, or definitely related to the gene therapy. Five serious adverse events occurred, including vomiting that led to hospitalization in one participant, which was attributed to the gene therapy. Serum aspartate and alanine aminotransferase levels increased in all participants and returned to baseline levels by 18 months. In all participants, the CSF β-galactosidase level increased and CSF GM1 ganglioside level decreased. Expressive communication and gross motor scores appeared stable, but fine motor and receptive communication scores decreased. The median CGI-I score was 3 (indicating minimal improvement) at 2 years and 4 (indicating no change) at 3 years; in historical controls, scores have been shown to increase (indicating worsening) over time. Neuroimaging showed patterns consistent with reduced rates of cerebral atrophy and favorable changes in myelination as compared with baseline. In this study involving nine participants with type II GM1 gangliosidosis, a single infusion of AAV9 encoding β-galactosidase was associated with adverse events, including severe vomiting in one participant and elevated liver-enzyme levels in all participants. Secondary end-point results suggested improvements in biochemical markers and neuroimaging patterns and stable or reduced rates of developmental deterioration in some measures. (Funded by the National Human Genome Research Institute and others; ClinicalTrials.gov number, NCT03952637.).

The dual rAAVrh8-HEXA and rAAVrh8-HEXB vector can restore central nervous system hexosaminidase (Hex) enzyme activity, decrease GM2 levels in cerebrospinal fluid and rescue phenotypic consequences of GM2 gangliosidosis, Tay-Sachs and Sandhoff diseases in animal models following simultaneous bi-thalamic (BiT) injections. Following up on an n = 2 expanded access trial, we initiated a phase 1/2, single-dose, dose-escalation of combined BiT, intra-cisterna magna and intrathecal infusion in children with Tay-Sachs and Sandhoff diseases (six infantile, three juvenile). The BiT injection volume and vector dose were doubled between four cohorts, with the lowest dose matching the earlier expanded access trial. Cerebrospinal fluid HexA enzyme activity, serum total Hex activity and GM2 levels showed a dose-dependent biochemical correction of the disease. Serum Hex activity surpassed 40 nmol h^-1 ml^-1, two times the lower limit of normal, and neuroimaging demonstrated increased fiber tracts. Correction was greatest at 12 weeks, but in decline by 24 weeks postdosing. Infantile patients experienced global clinical stabilization and prolonged oral feeding without aspiration until 3-3.5 years. Seizures had a later onset, were less frequent, less severe and more responsive to anti-convulsant medication. Adverse events were rare in infantile patients, but worsening dystonia was observed in juvenile patients, who were excluded from ongoing enrollment. ClinicalTrials.gov registration: NCT04669535 and NCT06614569 .

AIM To define the natural history of diffusion tensor imaging (DTI) in Chediak-Higashi Disease (CHD) participants in relation to normative development. Methods Twenty-five DTI scans from 15 CHD participants were compared with 100 DTI scans from 100 neurotypical controls (NC). Comparisons were evaluated for DTI metrics including fractional anisotropy (FA), and mean, axial, and radial diffusivity (MD, AD, RD, respectively). Correlational tractography was also performed to identify group differences between CHD and NC. Results Pediatric CHD participants had DTI metrics similar to NC, however, progressive pathogenic increases in MD, AD, and RD were observed in CHD participants compared to NC in white matter pathways of the whole brain, corpus callosum, and cerebellum. Correlational fiber tractography identified fiber tracts with decreased FA, and increased MD, AD, and RD in CHD compared to NC. Interpretation Progressive deviations in DTI metrics highlight the progressive neurodegeneration of CHD. Aberrations in cerebellar white matter is reflective of the clinical neurologic phenotype of CHD including cerebellar dysfunction and cognitive decline. The corollary of progressive aberrations in DTI metrics and progressive clinical neurodegeneration suggest DTI may be a suitable neuroimaging marker for CHD. Future studies should evaluate functional magnetic resonance imaging and volumetric studies in this cohort.

The two predominating subtypes of late-onset GM2 gangliosidosis are late-onset Tay-Sachs (LOTS) and late-onset Sandhoff disease (LOSD). Due to shared deficiencies of ß-hexosamindase A and significant clinical overlap, the two diseases have been considered indistinguishable. However, a growing body of evidence supports the notion of several distinctions between the two diseases. In this study, we highlight these distinctions through the cross-sectional evaluation of 27 late-onset GM2 gangliosidosis participants. Twenty-one participants with LOTS and 6 with LOSD were included in this study. We performed physical examinations alongside assessments for gait, balance, muscle strength, ataxia, nerve conduction velocities, and analyzed brain magnetic resonance imaging. Lower limb weakness (95% in LOTS, 100% in LOSD) and later development of upper limb weakness (90% in LOTS, 83% in LOSD) was highly prevalent in both cohorts. Accompanying gait disturbances, balance issues, and dysmetria (as assessed by the brief ataxia rating scale [BARS]) were also prevalent in both cohorts. Strength testing for the quadriceps and hamstrings demonstrated weakness in both cohorts, primarily impacting extensor muscles. Supratentorial gray and white matter volumes in both cohorts were similar to normative data. In contrast, BARS scores for dysarthria and oculomotor dysfunction were present and heterogenous in LOTS participants and absent in LOSD participants. 24% of LOTS participants and none of the LOSD participants had a history of neuropsychiatric symptoms. Cerebellar volume including lobules V and VI were lower in LOTS compared to LOSD and normative data. However, length dependent sensory neuropathy was present in all LOSD participants but absent in LOTS participants. Dysfunction of the posterior cerebellum (lobules VI, VII, and IX) has been shown to cause cerebellar cognitive affective syndrome (CCAS), that includes cognitive and behavioral disturbances. Furthermore, cerebellar dysfunction of lobules V and VI has been linked to dysarthric speech, and dysfunction of the posterior cerebellum has been linked to oculomotor symptoms. The finding of low cerebellar lobule volumes in LOTS, suggests the distinctive features of the LOTS phenotype are related to cerebellar dysfunction. However, the sensory symptoms unique to LOSD remains a mystery. The molecular and biochemical basis for the dichotomy between the LOTS and LOSD phenotypes requires further investigation.

Background: GM1 gangliosidosis, caused by biallelic variants in GLB1 , results from deficiency of lysosomal β-galactosidase, the enzyme primarily responsible for degradation of GM1 ganglioside. This progressive neurodegenerative disease is uniformly fatal with no approved therapies, but preclinical studies utilizing gene therapy have shown promising results. Methods: This phase 1-2 open label dose escalation study utilized a single intravenous administration of adeno-associated virus serotype 9 (AAV9) encoding β-galactosidase in the first nine enrolled Type II GM1 gangliosidosis participants. The primary endpoint was safety after 3 years; secondary and exploratory efficacy outcomes included cerebrospinal fluid (CSF) GM1 ganglioside and β-galactosidase, clinical assessments, and neuroimaging changes. Results: One serious adverse event was attributed to the vector, i.e., vomiting requiring rehospitalization for IV hydration. Serum aspartate and alanine aminotransferase levels increased following gene transfer but returned to baseline by 18 months. Per protocol analysis found stability in Vineland Expressive Communication and Gross Motor and significant declines in Fine Motor and Receptive Communication. Median CGI-Improvement scores at 2 and 3 years after gene transfer were “minimally improved” or “no change”. CSF β-galactosidase increased and GM1 ganglioside decreased in all participants. MRI showed improved myelination by differential tractography and declines in cerebral atrophy. MRS showed reduced loss of N -acetylaspartate+ N -acetylaspartyl glutamate (NAA) compared with historical controls. Conclusions: A single IV infusion of AAV9 encoding β-galactosidase was well-tolerated among the first nine Type II GM1 gangliosidosis participants. Secondary and exploratory outcomes suggested improvements in biochemical markers and neuroimaging and stabilized or reduced rates of developmental deterioration ( NCT03952637 ).

Background: Diffuse low-grade gliomas (dLGG) are rare slow growing brain tumors. Symptoms associated with dLGG typically include seizures, hemiparesis, ataxia, behavioral changes, headaches, and tremors. In this study, we present the case of a thirteen-year-old male admitted to the National Institutes of Health (NIH) Undiagnosed Diseases Program (UDP). To the best of our knowledge, this is one of the only documented cases of an adult-type dLGG diagnosed in a pediatric patient with monitoring of tumor progression for nearly a decade prior to diagnosis. Case presentation: The patient presented with a history of progressive signal abnormalities on brain magnetic resonance imaging (MRI), refractory to treatment attention deficit hyperactivity disorder (ADHD) and Oppositional Defiant Disorder (ODD), headaches, irritability, and difficulties sleeping. His detailed neurological exam was normal. Following six years of repeated MRI demonstrating increasing infiltrative tumor mass effect throughout gray and white matter, a brain biopsy was performed. The brain biopsy showed white and gray matter with mildly hypercellular areas, and tumor DNA sequencing showed the presence of a canonical IDH1 mutation. A “watch and wait” approach was adopted resulting from discussions between the patient and his family alongside the medical team with repeated quarterly brain MRI to monitor symptoms and tumor growth. Conclusion: While behavioral and psychiatric changes are common in brain tumor patients, they typically present alongside neurological symptoms which emphasizes the difficulty in diagnosing cases like this patient’s. Low-grade malignancies should be part of the differential diagnosis in cases with progressive multifocal white matter lesions, despite the absence of the typical neurological focal signs.

GM1 gangliosidosis is an ultra-rare inherited neurodegenerative lysosomal storage disorder caused by biallelic mutations in the GLB1 gene. GM1 is uniformly fatal and has no approved therapies, although clinical trials investigating gene therapy as a potential treatment for this condition are underway. Novel outcome measures or markers demonstrating the longitudinal effects of GM1 and potential recovery due to therapeutic intervention are urgently needed to establish efficacy of potential therapeutics. One promising tool is differential tractography, a novel imaging modality utilizing serial diffusion tensor imaging to quantify longitudinal changes in white matter microstructure. In this study, we present the novel use of differential tractography in quantifying the progression of GM1 alongside age-matched neurotypical controls. We analysed 113 diffusion tensor imaging scans from 16 GM1 patients and 32 age-matched neurotypical controls to investigate longitudinal changes in white matter pathology. GM1 patients showed white matter degradation evident by both the number and size of fibre tract loss. In contrast, neurotypical controls showed longitudinal white matter improvements as evident by both the number and size of fibre tract growth. We also corroborated these findings by documenting significant correlations between clinical global impression scores of clinical presentations and our differential tractography derived metrics in our GM1 cohort. Specifically, GM1 patients who lost more neuronal fibre tracts also had a worse clinical presentation. This result demonstrates the utility of differential tractography as a marker for disease progression in GM1 patients with potential extension to other neurodegenerative diseases and therapeutic intervention.