Study of Intraventricular Cerliponase Alfa for CLN2 Disease

Genetic Testing to Inform Epilepsy Treatment Management From an International Study of Clinical Practice

Importance

It is currently unknown how often and in which ways a genetic diagnosis given to a patient with epilepsy is associated with clinical management and outcomes.

Objective

To evaluate how genetic diagnoses in patients with epilepsy are associated with clinical management and outcomes.

Design, Setting, and Participants

This was a retrospective cross-sectional study of patients referred for multigene panel testing between March 18, 2016, and August 3, 2020, with outcomes reported between May and November 2020. The study setting included a commercial genetic testing laboratory and multicenter clinical practices. Patients with epilepsy, regardless of sociodemographic features, who received a pathogenic/likely pathogenic (P/LP) variant were included in the study. Case report forms were completed by all health care professionals.

Exposures

Genetic test results.

Main Outcomes and Measures

Clinical management changes after a genetic diagnosis (ie, 1 P/LP variant in autosomal dominant and X-linked diseases; 2 P/LP variants in autosomal recessive diseases) and subsequent patient outcomes as reported by health care professionals on case report forms.

Results

Among 418 patients, median (IQR) age at the time of testing was 4 (1-10) years, with an age range of 0 to 52 years, and 53.8% (n = 225) were female individuals. The mean (SD) time from a genetic test order to case report form completion was 595 (368) days (range, 27-1673 days). A genetic diagnosis was associated with changes in clinical management for 208 patients (49.8%) and usually (81.7% of the time) within 3 months of receiving the result. The most common clinical management changes were the addition of a new medication (78 [21.7%]), the initiation of medication (51 [14.2%]), the referral of a patient to a specialist (48 [13.4%]), vigilance for subclinical or extraneurological disease features (46 [12.8%]), and the cessation of a medication (42 [11.7%]). Among 167 patients with follow-up clinical information available (mean [SD] time, 584 [365] days), 125 (74.9%) reported positive outcomes, 108 (64.7%) reported reduction or elimination of seizures, 37 (22.2%) had decreases in the severity of other clinical signs, and 11 (6.6%) had reduced medication adverse effects. A few patients reported worsening of outcomes, including a decline in their condition (20 [12.0%]), increased seizure frequency (6 [3.6%]), and adverse medication effects (3 [1.8%]). No clinical management changes were reported for 178 patients (42.6%).

Conclusions and Relevance

Results of this cross-sectional study suggest that genetic testing of individuals with epilepsy may be materially associated with clinical decision-making and improved patient outcomes.

Treatment of CLN1 disease with a blood-brain barrier penetrating lysosomal enzyme

Neuronal ceroid lipofuscinosis type 1(CLN1 disease) is a rare autosomal recessive lysosomal storage disease caused by genetic defects of palmitoyl protein thioesterase-1(PPT1), leading to accumulation of lipofuscin granules in brain and progressive neurodegeneration. Psychomotor regression, seizures, loss of vision, and movement disorder begin in infancy and result in early death. Currently, no disease-modifying therapy is available.

We report a 68-month-old boy with CLN1 treated on a compassionate use basis weekly for 26 months with a PPT1 enzyme fused to an anti-insulin receptor antibody (AGT-194), thereby enabling penetration of the blood-brain barrier (BBB). During treatment, no side effects were observed, while seizure frequency decreased, life quality improved, and the boy's general condition remained stable.

This case documents for the first time that treatment of CLN1 is principally feasible by an intravenous BBB penetrating enzyme replacement therapy using PPT1 fused with the human insulin receptor. Monitoring of side effects raised no unacceptable or unexpected safety concerns.Observed improvement of life quality related to ameliorated epilepsy control raises hope that further robust clinical trials including patients in earlier stages of disease will show positive results.

Cross-species efficacy of enzyme replacement therapy for CLN1 disease in mice and sheep

CLN1 disease, also called infantile neuronal ceroid lipofuscinosis (NCL) or infantile Batten disease, is a fatal neurodegenerative lysosomal storage disorder resulting from mutations in the CLN1 gene encoding the soluble lysosomal enzyme palmitoyl-protein thioesterase 1 (PPT1). Therapies for CLN1 disease have proven challenging because of the aggressive disease course and the need to treat widespread areas of the brain and spinal cord. Indeed, gene therapy has proven less effective for CLN1 disease than for other similar lysosomal enzyme deficiencies. We therefore tested the efficacy of enzyme replacement therapy (ERT) by administering monthly infusions of recombinant human PPT1 (rhPPT1) to PPT1-deficient mice (Cln1-/-) and CLN1R151X sheep to assess how to potentially scale up for translation. In Cln1-/- mice, intracerebrovascular (i.c.v.) rhPPT1 delivery was the most effective route of administration, resulting in therapeutically relevant CNS levels of PPT1 activity. rhPPT1-treated mice had improved motor function, reduced disease-associated pathology, and diminished neuronal loss. In CLN1R151X sheep, i.c.v. infusions resulted in widespread rhPPT1 distribution and positive treatment effects measured by quantitative structural MRI and neuropathology. This study demonstrates the feasibility and therapeutic efficacy of i.c.v. rhPPT1 ERT. These findings represent a key step toward clinical testing of ERT in children with CLN1 disease and highlight the importance of a cross-species approach to developing a successful treatment strategy.

Therapeutic Management of COVID-19 in a Pediatric Patient with Neurodegenerative CLN2 Disease and ICV-Enzyme Replacement Therapy: A Case Report

The 12 years old male patient presented here suffers from neuronal ceroid lipofuscinoses 2 (CLN2) (MIM# 204500) and receives intracerebroventricular enzyme replacement therapy (ICV-ERT) every 14 days. After the emergence of the coronavirus disease 2019 (COVID-19) pandemic, routine care of children and adolescents with rare chronic diseases has become challenging. Although, in general, children do not develop severe COVID-19, when severe acute respiratory syndrome coronavirus 2 infection was detected by polymerase chain reaction-screening examination in our CLN2 patient before hospital admission for ICV-ERT, he was regarded to be at risk. Upon diagnosis, the patient developed respiratory deterioration symptoms and was admitted to our pediatric intensive care unit to receive oxygen, remdesivir, and steroids. As far as we know, this is the first CLN2 patient receiving intraventricular enzyme therapy with COVID-19 who required intensive care treatment and specific therapy.

Developmental and epileptic encephalopathies - therapeutic consequences of genetic testing

Developmental and epileptic encephalopathies comprise a heterogeneous group of monogenic neurodevelopmental disorders characterized by early-onset seizures, marked epileptic activity and abnormal neurocognitive development. The identification of an increasing number of underlying genetic alterations and their pathophysiological roles in cellular signaling drives the way toward novel precision therapies. The implementation of novel treatments that target the underlying mechanisms gives hope for disease modification that will improve not only the seizure burden but also the neurodevelopmental outcome of affected children. So far, beneficial effects are mostly reported in individual trials and small numbers of patients. There is a need for international collaborative studies to define the natural history and relevant outcome measures and to test novel pharmacological approaches.

Evolving therapies in neuronopathic LSDs: opportunities and challenges

Lysosomal storage disorders (LSD) are multisystemic progressive disorders caused by genetic mutations involving lysosomal function. While LSDs are individually considered rare diseases, the overall true prevalence of these disorders is likely higher than our current estimates. More than two third of the LSDs have associated neurodegeneration and the neurological phenotype often defines the course of the disease and treatment outcomes. Addressing the neurological involvement in LSDs has posed a significant challenge in the rapidly evolving field of therapies for these diseases. In this review, we summarize current approaches and clinical trials available for patients with neuronopathic lysosomal storage disorders, exploring the opportunities and challenges that have emerged with each of these.

The glymphatic system: Current understanding and modeling

We review theoretical and numerical models of the glymphatic system, which circulates cerebrospinal fluid and interstitial fluid around the brain, facilitating solute transport. Models enable hypothesis development and predictions of transport, with clinical applications including drug delivery, stroke, cardiac arrest, and neurodegenerative disorders like Alzheimer's disease. We sort existing models into broad categories by anatomical function: Perivascular flow, transport in brain parenchyma, interfaces to perivascular spaces, efflux routes, and links to neuronal activity. Needs and opportunities for future work are highlighted wherever possible; new models, expanded models, and novel experiments to inform models could all have tremendous value for advancing the field.

Long-term neurological and psychiatric outcomes in patients with aromatic l-amino acid decarboxylase deficiency

INTRODUCTION

l-amino acid decarboxylase deficiency (AADCD) is an ultrarare autosomal recessive defect of biogenic amine synthesis that presents with early-onset encephalopathy progressing to severe neurological impairment and intellectual disability. We aimed to explore neurocognitive and behavioral profiles associated with AADCD and possible factors predicting outcome in more detail.

METHODS

Nine AADCD patients (23.2 ± 10.3 years; range 8-40) underwent systematic clinical and neuropsychological assessment. Diagnostic levels of CSF 5-hydroxyindolacetic acid (5-HIAA) and homovanillic acid (HVA), and DDC genotype (as ascertained by American College of Medical Genetics and Genomics grading) were included in the data analysis.

RESULTS

All AADCD patients were affected by intellectual disability and psychiatric disorders. Movement disorders included parkinsonism-dystonia, dysarthria, and oculogyric crises. CSF 5-HIAA and HVA levels at diagnosis had a significant influence on adaptive behavior and executive function performance. Patients homozygous for DDC pathogenetic variants showed lower CSF 5-HIAA and HVA levels and higher Unified Parkinson's Disease Rating Scale scores. The disease showed a self-limiting clinical course with partial improvement under pharmacological treatment (B6 and dopamine mimetic drugs).

CONCLUSIONS

Patients with AADCD suffer from neuropsychological and psychopathological impairment, which may be improved but not reversed under the present therapeutic approach. However, cognitive functioning should be specifically examined in order to avoid its underestimation on the basis of movement disorder severity. Genotype and biogenic amine level at diagnosis have an important prognostic value.

An Optimized Comparative Proteomic Approach as a Tool in Neurodegenerative Disease Research

Recent advances in proteomic technologies now allow unparalleled assessment of the molecular composition of a wide range of sample types. However, the application of such technologies and techniques should not be undertaken lightly. Here, we describe why the design of a proteomics experiment itself is only the first step in yielding high-quality, translatable results. Indeed, the effectiveness and/or impact of the majority of contemporary proteomics screens are hindered not by commonly considered technical limitations such as low proteome coverage but rather by insufficient analyses. Proteomic experimentation requires a careful methodological selection to account for variables from sample collection, through to database searches for peptide identification to standardised post-mass spectrometry options directed analysis workflow, which should be adjusted for each study, from determining when and how to filter proteomic data to choosing holistic versus trend-wise analyses for biologically relevant patterns. Finally, we highlight and discuss the difficulties inherent in the modelling and study of the majority of progressive neurodegenerative conditions. We provide evidence (in the context of neurodegenerative research) for the benefit of undertaking a comparative approach through the application of the above considerations in the alignment of publicly available pre-existing data sets to identify potential novel regulators of neuronal stability.

Modelling Neurological Diseases in Large Animals: Criteria for Model Selection and Clinical Assessment

Issue: The impact of neurological disorders is recognised globally, with one in six people affected in their lifetime and few treatments to slow or halt disease progression. This is due in part to the increasing ageing population, and is confounded by the high failure rate of translation from rodent-derived therapeutics to clinically effective human neurological interventions. Improved translation is demonstrated using higher order mammals with more complex/comparable neuroanatomy. These animals effectually span this translational disparity and increase confidence in factors including routes of administration/dosing and ability to scale, such that potential therapeutics will have successful outcomes when moving to patients. Coupled with advancements in genetic engineering to produce genetically tailored models, livestock are increasingly being used to bridge this translational gap. Approach: In order to aid in standardising characterisation of such models, we provide comprehensive neurological assessment protocols designed to inform on neuroanatomical dysfunction and/or lesion(s) for large animal species. We also describe the applicability of these exams in different large animals to help provide a better understanding of the practicalities of cross species neurological disease modelling. Recommendation: We would encourage the use of these assessments as a reference framework to help standardise neurological clinical scoring of large animal models.

Drug delivery for neuronopathic lysosomal storage diseases: evolving roles of the blood brain barrier and cerebrospinal fluid

Whereas significant strides have been made in the treatment of lysosomal storage diseases (LSDs), the neuronopathy associated with these diseases remains impervious mainly because of the blood-brain barrier (BBB), which prevents delivery of large molecules to the brain. However, 100 years of research on the BBB since its conceptualization have clarified many of its functional and structural characteristics, spurring recent endeavors to deliver therapeutics across it to treat central nervous system (CNS) disorders, including neuronopathic LSDs. Along with the BBB, the cerebrospinal fluid (CSF) also functions to protect the microenvironment of the CNS, and it is therefore deeply involved in CNS disorders at large. Recent research aimed at developing therapeutics for neuronopathic LSDs has uncovered a number of critical roles played by the CSF that require further clarification. This review summarizes the most up-to-date understanding of the BBB and the CSF acquired during the development of therapeutics for neuronopathic LSDs, and highlights some of the associated challenges that require further research.

Therapeutic Strategies For Tay-Sachs Disease

Tay-Sachs disease (TSD) is an autosomal recessive disease that features progressive neurodegenerative presentations. It affects one in 100,000 live births. Currently, there is no approved therapy or cure. This review summarizes multiple drug development strategies for TSD, including enzyme replacement therapy, pharmaceutical chaperone therapy, substrate reduction therapy, gene therapy, and hematopoietic stem cell replacement therapy. In vitro and in vivo systems are described to assess the efficacy of the aforementioned therapeutic strategies. Furthermore, we discuss using MALDI mass spectrometry to perform a high throughput screen of compound libraries. This enables discovery of compounds that reduce GM2 and can lead to further development of a TSD therapy.

The role of lysosomal cathepsins in neurodegeneration: Mechanistic insights, diagnostic potential and therapeutic approaches

Lysosomes are ubiquitous organelles with a fundamental role in maintaining cellular homeostasis by mediating degradation and recycling processes. Cathepsins are the most abundant lysosomal hydrolyses and are responsible for the bulk degradation of various substrates. A correct autophagic function is essential for neuronal survival, as most neurons are post-mitotic and thus susceptible to accumulate cellular components. Increasing evidence suggests a crucial role of the lysosome in neurodegeneration as a key regulator of aggregation-prone and disease-associated proteins, such as α-synuclein, β-amyloid and huntingtin. Particularly, alterations in lysosomal cathepsins CTSD, CTSB and CTSL can contribute to the pathogenesis of neurodegenerative diseases as seen for neuronal ceroid lipofuscinosis, synucleinopathies (Parkinson's disease, Dementia with Lewy Body and Multiple System Atrophy) as well as Alzheimer's and Huntington's disease. In this review, we provide an overview of recent evidence implicating CTSD, CTSB and CTSL in neurodegeneration, with a special focus on the role of these enzymes in α-synuclein metabolism. In addition, we summarize the potential role of lysosomal cathepsins as clinical biomarkers in neurodegenerative diseases and discuss potential therapeutic approaches by targeting lysosomal function.

Intrathecal delivery and its applications in leptomeningeal disease

Intrathecal delivery (IT) of opiates into the cerebrospinal fluid (CSF) for anesthesia and pain relief has been used clinically for decades, but this relatively straightforward approach of bypassing the blood-brain barrier has been underutilized for other indications because of its lack of utility in delivering small lipid-soluble drugs. However, emerging evidence suggests that IT drug delivery be an efficacious strategy for the treatment of cancers in which there is leptomeningeal spread of disease. In this review, we discuss CSF flow dynamics and CSF clearance pathways in the context of intrathecal delivery. We discuss human and animal studies of several new classes of therapeutic agents-cellular, protein, nucleic acid, and nanoparticle-based small molecules-that may benefit from IT delivery. The complexity of the CSF compartment presents several key challenges in predicting biodistribution of IT-delivered drugs. New approaches and strategies are needed that can overcome the high rates of turnover in the CSF to reach specific tissues or cellular targets.

A Historical Review of Brain Drug Delivery

The history of brain drug delivery is reviewed beginning with the first demonstration, in 1914, that a drug for syphilis, salvarsan, did not enter the brain, due to the presence of a blood-brain barrier (BBB). Owing to restricted transport across the BBB, FDA-approved drugs for the CNS have been generally limited to lipid-soluble small molecules. Drugs that do not cross the BBB can be re-engineered for transport on endogenous BBB carrier-mediated transport and receptor-mediated transport systems, which were identified during the 1970s-1980s. By the 1990s, a multitude of brain drug delivery technologies emerged, including trans-cranial delivery, CSF delivery, BBB disruption, lipid carriers, prodrugs, stem cells, exosomes, nanoparticles, gene therapy, and biologics. The advantages and limitations of each of these brain drug delivery technologies are critically reviewed.

Natural history of MRI brain volumes in patients with neuronal ceroid lipofuscinosis 3: a sensitive imaging biomarker

PURPOSE

Grey matter (GM) atrophy due to neuronal loss is a striking feature of patients with CLN3 disease. A precise and quantitative description of disease progression is needed in order to establish an evaluation tool for current and future experimental treatments. In order to develop a quantitative marker to measure brain volume outcome, we analysed the longitudinal volumetric development of GM, white matter (WM) and lateral ventricles and correlated those with the clinical course.

METHODS

One hundred twenty-two MRI scans of 35 patients (21 females; 14 males; age 15.3 ± 4.8 years) with genetically confirmed CLN3 disease were performed. A three-dimensional T1-weighted sequence was acquired with whole brain coverage. Volumetric segmentation of the brain was performed with the FreeSurfer image analysis suite. The clinical severity was assessed by the Hamburg jNCL score, a disease-specific scoring system.

RESULTS

The volumes of supratentorial cortical GM and supratentorial WM, cerebellar GM, basal ganglia/thalamus and hippocampus significantly (r =  - 0.86 to - 0.69, p < 0.0001) decreased with age, while the lateral ventricle volume increased (r = 0.68, p < 0.0001). Supratentorial WM volume correlated poorer with age (r =  - 0.56, p = 0.0001). Supratentorial cortical GM volume showed the steepest (4.6% (± 0.2%)) and most uniform decrease with strongest correlation with age (r =  - 0.86, p < 0.0001). In addition, a strong correlation with disease specific clinical scoring existed for the supratentorial cortical GM volume (r = 0.85, p =  < 0.0001).

CONCLUSION

Supratentorial cortical GM volume is a sensitive parameter for assessment of disease progression even in early and late disease stages and represents a potential reliable outcome measure for evaluation of experimental therapies.

Treatment of Neuronopathic Mucopolysaccharidoses with Blood-Brain Barrier-Crossing Enzymes: Clinical Application of Receptor-Mediated Transcytosis

Enzyme replacement therapy (ERT) has paved the way for treating the somatic symptoms of lysosomal storage diseases (LSDs), but the inability of intravenously administered enzymes to cross the blood-brain barrier (BBB) has left the central nervous system (CNS)-related symptoms of LSDs largely impervious to the therapeutic benefits of ERT, although ERT via intrathecal and intracerebroventricular routes can be used for some neuronopathic LSDs (in particular, mucopolysaccharidoses). However, the considerable practical issues involved make these routes unsuitable for long-term treatment. Efforts have been made to modify enzymes (e.g., by fusing them with antibodies against innate receptors on the cerebrovascular endothelium) so that they can cross the BBB via receptor-mediated transcytosis (RMT) and address neuronopathy in the CNS. This review summarizes the various scientific and technological challenges of applying RMT to the development of safe and effective enzyme therapeutics for neuronopathic mucopolysaccharidoses; it then discusses the translational and methodological issues surrounding preclinical and clinical evaluation to establish RMT-applied ERT.

Reversal of neuroinflammation in novel GS model mice by single i.c.v. administration of CHO-derived rhCTSA precursor protein

Galactosialidosis (GS) is a lysosomal cathepsin A (CTSA) deficiency. It associates with a simultaneous decrease of neuraminidase 1 (NEU1) activity and sialylglycan storage. Central nervous system (CNS) symptoms reduce the quality of life of juvenile/adult-type GS patients, but there is no effective therapy. Here, we established a novel GS model mouse carrying homozygotic Ctsa IVS6+1g→a mutation causing partial exon 6 skipping with concomitant deficiency of Ctsa/Neu1. The GS mice developed juvenile/adult GS-like symptoms, such as gargoyle-like face, edema, proctoprosia due to sialylglycan accumulation, and neurovisceral inflammation, including activated microglia/macrophage appearance and increase of inflammatory chemokines. We produced human CTSA precursor proteins (proCTSA), a homodimer carrying terminal mannose 6-phosphate (M6P)-type N-glycans. The CHO-derived proCTSA was taken up by GS patient-derived fibroblasts via M6P receptors and delivered to lysosomes. Catalytically active mature CTSA showed a shorter half-life due to intralysosomal proteolytic degradation. Following single i.c.v. administration, proCTSA was widely distributed, restored the Neu1 activity, and reduced the sialylglycans accumulated in brain regions. Moreover, proCTSA suppressed neuroinflammation associated with reduction of activated microglia/macrophage and up-regulated Mip1α. The results show therapeutic effects of intracerebrospinal enzyme replacement utilizing CHO-derived proCTSA and suggest suppression of CNS symptoms.

Lysosomal Proteomics Links Disturbances in Lipid Homeostasis and Sphingolipid Metabolism to CLN5 Disease

CLN5 disease (MIM: 256731) represents a rare late-infantile form of neuronal ceroid lipofuscinosis (NCL), caused by mutations in the CLN5 gene that encodes the CLN5 protein (CLN5p), whose physiological roles stay unanswered. No cure is currently available for CLN5 patients and the opportunities for therapies are lagging. The role of lysosomes in the neuro-pathophysiology of CLN5 disease represents an important topic since lysosomal proteins are directly involved in the primary mechanisms of neuronal injury occurring in various NCL forms. We developed and implemented a lysosome-focused, label-free quantitative proteomics approach, followed by functional validations in both CLN5-knockout neuronal-like cell lines and Cln5-/- mice, to unravel affected pathways and modifying factors involved in this disease scenario. Our results revealed a key role of CLN5p in lipid homeostasis and sphingolipid metabolism and highlighted mutual NCL biomarkers scored with high lysosomal confidence. A newly generated cln5 knockdown zebrafish model recapitulated most of the pathological features seen in NCL disease. To translate the findings from in-vitro and preclinical models to patients, we evaluated whether two FDA-approved drugs promoting autophagy via TFEB activation or inhibition of the glucosylceramide synthase could modulate in-vitro ROS and lipid overproduction, as well as alter the locomotor phenotype in zebrafish. In summary, our data advance the general understanding of disease mechanisms and modifying factors in CLN5 disease, which are recurring in other NCL forms, also stimulating new pharmacological treatments.

Visual perception and macular integrity in non-classical CLN2 disease

PURPOSE

Patients with CLN2 suffer from epileptic seizures, rapid psychomotor decline and vision loss in early childhood. The aim of the study was to provide longitudinal ophthalmic data of patients with confirmed genetic mutation and non-classical disease course, marked by later onset, protracted progression and prolonged life span.

METHODS

Prospective, observational study to assess visual acuity, retinal features (Weil Cornell Ophthalmic Score), central retinal thickness (CRT) measured by optical coherence tomography and general disease progression (Hamburg CLN2 motor language score) in non-classical CLN2 patients.

RESULTS

All patients received intracerebroventricular enzyme replacement therapy with cerliponase alfa. Mean age at last follow-up was 12.4 years; mean follow-up time 2.6 years. All cases demonstrated a stable Hamburg motor language CLN2 Score and Weill Cornell LINCL Ophthalmic Severity Score. Visual function remained stable in 4/6 patients, 2/6 patients showed a decrease, 4/6 cases had a stable CRT and 2/6 showed a reduction of CRT. One patient showed a massive macular thinning and low vision. A correlation with a specific mutation or age could not be verified.

DISCUSSION

The presented longitudinal study characterizes the variable ocular involvement in non-classical CLN2 disease and contributes to the natural history description. The functional and morphologic data outline the necessity of regular ophthalmic examination. Ocular phenotyping and description of retinal degeneration in non-classical CLN2 disease.

New paradigms for the treatment of pediatric monogenic epilepsies: Progressing toward precision medicine

Despite the availability of 28 antiseizure medications (ASMs), one-third of people with epilepsy fail to achieve sustained freedom from seizures. Clinical outcome is even poorer for children with developmental and epileptic encephalopathies (DEEs), many of which are due to single-gene mutations. Discovery of causative genes, however, has paved the way to understanding the molecular mechanism underlying these epilepsies, and to the rational application, or development, of precision treatments aimed at correcting the specific functional defects or their consequences. This article provides an overview of current progress toward precision medicine (PM) in the management of monogenic pediatric epilepsies, by focusing on four different scenarios, namely (a) rational selection of ASMs targeting specifically the underlying pathogenetic mechanisms; (b) development of targeted therapies based on novel molecules; (c) use of dietary treatments or food constituents aimed at correcting specific metabolic defects; and (d) repurposing of medications originally approved for other indications. This article is part of the Special Issue "Severe Infantile Epilepsies".

Recent Insight into the Genetic Basis, Clinical Features, and Diagnostic Methods for Neuronal Ceroid Lipofuscinosis

Neuronal ceroid lipofuscinoses (NCLs) are a group of rare, inherited, neurodegenerative lysosomal storage disorders that affect children and adults. They are traditionally grouped together, based on shared clinical symptoms and pathological ground. To date, 13 autosomal recessive gene variants, as well as one autosomal dominant gene variant, of NCL have been described. These genes encode a variety of proteins, whose functions have not been fully defined; most are lysosomal enzymes, transmembrane proteins of the lysosome, or other organelles. Common symptoms of NCLs include the progressive loss of vision, mental and motor deterioration, epileptic seizures, premature death, and, in rare adult-onset cases, dementia. Depending on the mutation, these symptoms can vary, with respect to the severity and onset of symptoms by age. Currently, all forms of NCL are fatal, and no curative treatments are available. Herein, we provide an overview to summarize the current knowledge regarding the pathophysiology, genetics, and clinical manifestation of these conditions, as well as the approach to diagnosis.

International League Against Epilepsy classification and definition of epilepsy syndromes with onset at a variable age: position statement by the ILAE Task Force on Nosology and Definitions

The goal of this paper is to provide updated diagnostic criteria for the epilepsy syndromes that have a variable age of onset, based on expert consensus of the International League Against Epilepsy Nosology and Definitions Taskforce (2017-2021). We use language consistent with current accepted epilepsy and seizure classifications and incorporate knowledge from advances in genetics, electroencephalography, and imaging. Our aim in delineating the epilepsy syndromes that present at a variable age is to aid diagnosis and to guide investigations for etiology and treatments for these patients.

Ppt1-deficiency dysregulates lysosomal Ca++ homeostasis contributing to pathogenesis in a mouse model of CLN1 disease

Inactivating mutations in the PPT1 gene encoding palmitoyl-protein thioesterase-1 (PPT1) underlie the CLN1 disease, a devastating neurodegenerative lysosomal storage disorder. The mechanism of pathogenesis underlying CLN1 disease has remained elusive. PPT1 is a lysosomal enzyme, which catalyzes the removal of palmitate from S-palmitoylated proteins (constituents of ceroid lipofuscin) facilitating their degradation and clearance by lysosomal hydrolases. Thus, it has been proposed that Ppt1-deficiency leads to lysosomal accumulation of ceroid lipofuscin leading to CLN1 disease. While S-palmitoylation is catalyzed by palmitoyl acyltransferases (called ZDHHCs), palmitoyl-protein thioesterases (PPTs) depalmitoylate these proteins. We sought to determine the mechanism by which Ppt1-deficiency may impair lysosomal degradative function leading to infantile neuronal ceroid lipofuscinosis pathogenesis. Here, we report that in Ppt1^-/- mice, which mimic CLN1 disease, low level of inositol 3-phosphate receptor-1 (IP3R1) that mediates Ca⁺⁺ transport from the endoplasmic reticulum to the lysosome dysregulated lysosomal Ca⁺⁺ homeostasis. Intriguingly, the transcription factor nuclear factor of activated T-cells, cytoplasmic 4 (NFATC4), which regulates IP3R1-expression, required S-palmitoylation for trafficking from the cytoplasm to the nucleus. We identified two palmitoyl acyltransferases, ZDHHC4 and ZDHHC8, which catalyzed S-palmitoylation of NFATC4. Notably, in Ppt1^-/- mice, reduced ZDHHC4 and ZDHHC8 levels markedly lowered S-palmitoylated NFATC4 (active) in the nucleus, which inhibited IP3R1-expression, thereby dysregulating lysosomal Ca⁺⁺ homeostasis. Consequently, Ca⁺⁺ -dependent lysosomal enzyme activities were markedly suppressed. Impaired lysosomal degradative function impaired autophagy, which caused lysosomal storage of undigested cargo. Importantly, IP3R1-overexpression in Ppt1^-/- mouse fibroblasts ameliorated this defect. Our results reveal a previously unrecognized role of Ppt1 in regulating lysosomal Ca⁺⁺ homeostasis and suggest that this defect contributes to pathogenesis of CLN1 disease.

Blood-brain barrier delivery for lysosomal storage disorders with IgG-lysosomal enzyme fusion proteins

The majority of lysosomal storage diseases affect the brain. Treatment of the brain with intravenous enzyme replacement therapy is not successful, because the recombinant lysosomal enzymes do not cross the blood-brain barrier (BBB). Biologic drugs, including lysosomal enzymes, can be re-engineered for BBB delivery as IgG-enzyme fusion proteins. The IgG domain of the fusion protein is a monoclonal antibody directed against an endogenous receptor-mediated transporter at the BBB, such as the insulin receptor or the transferrin receptor. This receptor transports the IgG across the BBB, in parallel with the endogenous receptor ligand, and the IgG acts as a molecular Trojan horse to ferry into brain the lysosomal enzyme genetically fused to the IgG. The IgG-enzyme fusion protein is bi-functional and retains both high affinity binding for the BBB receptor, and high lysosomal enzyme activity. IgG-lysosomal enzymes are presently in clinical trials for treatment of the brain in Mucopolysaccharidosis.

Recombinant pro-CTSD (cathepsin D) enhances SNCA/α-Synuclein degradation in α-Synucleinopathy models

Parkinson disease (PD) is a neurodegenerative disorder characterized by the abnormal intracellular accumulation of SNCA/α-synuclein. While the exact mechanisms underlying SNCA pathology are not fully understood, increasing evidence suggests the involvement of autophagy as well as lysosomal deficiencies. Because CTSD (cathepsin D) has been proposed to be the major lysosomal protease involved in SNCA degradation, its deficiency has been linked to the presence of insoluble SNCA conformers in the brain of mice and humans as well as to the transcellular transmission of SNCA aggregates. We here postulate that SNCA degradation can be enhanced by the application of the recombinant human proform of CTSD (rHsCTSD). Our results reveal that rHsCTSD is efficiently endocytosed by neuronal cells, correctly targeted to lysosomes and matured to an enzymatically active protease. In dopaminergic neurons derived from induced pluripotent stem cells (iPSC) of PD patients harboring the A53T mutation within the SNCA gene, we confirm the reduction of insoluble SNCA after treatment with rHsCTSD. Moreover, we demonstrate a decrease of pathological SNCA conformers in the brain and within primary neurons of a ctsd-deficient mouse model after dosing with rHsCTSD. Boosting lysosomal CTSD activity not only enhanced SNCA clearance in human and murine neurons as well as tissue, but also restored endo-lysosome and autophagy function. Our findings indicate that CTSD is critical for SNCA clearance and function. Thus, enzyme replacement strategies utilizing CTSD may also be of therapeutic interest for the treatment of PD and other synucleinopathies aiming to decrease the SNCA burden.Abbreviations: aa: amino acid; SNCA/α-synuclein: synuclein alpha; APP: amyloid beta precursor protein; BBB: blood brain barrier; BF: basal forebrain; CBB: Coomassie Brilliant Blue; CLN: neuronal ceroid lipofuscinosis; CNL10: neuronal ceroid lipofuscinosis type 10; Corr.: corrected; CTSD: cathepsin D; CTSB: cathepsin B; DA: dopaminergic; DA-iPSn: induced pluripotent stem cell-derived dopaminergic neurons; dox: doxycycline; ERT: enzyme replacement therapy; Fx: fornix, GBA/β-glucocerebrosidase: glucosylceramidase beta; h: hour; HC: hippocampus; HT: hypothalamus; i.c.: intracranially; IF: immunofluorescence; iPSC: induced pluripotent stem cell; KO: knockout; LAMP1: lysosomal associated membrane protein 1; LSDs: lysosomal storage disorders; MAPT: microtubule associated protein tau; M6P: mannose-6-phosphate; M6PR: mannose-6-phosphate receptor; MB: midbrain; mCTSD: mature form of CTSD; neurofil.: neurofilament; PD: Parkinson disease; proCTSD: proform of CTSD; PRNP: prion protein; RFU: relative fluorescence units; rHsCTSD: recombinant human proCTSD; SAPC: Saposin C; SIM: structured illumination microscopy; T-insol: Triton-insoluble; T-sol: Triton-soluble; TEM: transmission electron microscopy, TH: tyrosine hydroxylase; Thal: thalamus.

An Idealized Clinicogenomic Registry to Engage Underrepresented Populations Using Innovative Technology

Current best practices in tumor registries provide a glimpse into a limited time frame over the natural history of disease, usually a narrow window around diagnosis and biopsy. This creates challenges meeting public health and healthcare reimbursement policies that increasingly require robust documentation of long-term clinical trajectories, quality of life, and health economics outcomes. These challenges are amplified for underrepresented minority (URM) and other disadvantaged populations, who tend to view the institution of clinical research with skepticism. Participation gaps leave such populations underrepresented in clinical research and, importantly, in policy decisions about treatment choices and reimbursement, thus further augmenting health, social, and economic disparities. Cloud computing, mobile computing, digital ledgers, tokenization, and artificial intelligence technologies are powerful tools that promise to enhance longitudinal patient engagement across the natural history of disease. These tools also promise to enhance engagement by giving participants agency over their data and addressing a major impediment to research participation. This will only occur if these tools are available for use with all patients. Distributed ledger technologies (specifically blockchain) converge these tools and offer a significant element of trust that can be used to engage URM populations more substantively in clinical research. This is a crucial step toward linking composite cohorts for training and optimization of the artificial intelligence tools for enhancing public health in the future. The parameters of an idealized clinical genomic registry are presented.

Value of genetic testing for pediatric epilepsy: Driving earlier diagnosis of CLN2 Batten disease

This study assessed the effectiveness of genetic testing in shortening the time to diagnosis of late infantile neuronal ceroid lipofuscinosis type 2 (CLN2) disease. Individuals who received epilepsy gene panel testing through Behind the Seizure^®, a sponsored genetic testing program (Cohort A), were compared to children outside of the sponsored testing program during the same period (Cohort B). Two cohorts were analyzed: children aged ≥24 to ≤60 months with unprovoked seizure onset at ≥24 months between December 2016 and January 2020 (Cohort 1) and children aged 0 to ≤60 months at time of testing with unprovoked seizure onset at any age between February 2019 and January 2020 (Cohort 2). The diagnostic yield in Cohort 1A (n = 1814) was 8.4% (n = 153). The TPP1 diagnostic yield within Cohort 1A was 2.9‐fold higher compared to Cohort 1B (1.0%, n = 18/1814 vs. .35%, n = 8/2303; p = .0157). The average time from first symptom to CLN2 disease diagnosis was significantly shorter than previously reported (9.8 vs. 22.7 months, p < .001). These findings indicate that facilitated access to early epilepsy gene panel testing helps to increase diagnostic yield for CLN2 disease and shortens the time to diagnosis, enabling earlier intervention.

Experimental Therapeutic Approaches for the Treatment of Retinal Pathology in Neuronal Ceroid Lipofuscinoses

The neuronal ceroid lipofuscinoses (NCLs) are a group of childhood-onset neurodegenerative lysosomal storage disorders mainly affecting the brain and the retina. In the NCLs, disease-causing mutations in 13 different ceroid lipofuscinoses genes (CLN) have been identified. The clinical symptoms include seizures, progressive neurological decline, deterioration of motor and language skills, and dementia resulting in premature death. In addition, the deterioration and loss of vision caused by progressive retinal degeneration is another major hallmark of NCLs. To date, there is no curative therapy for the treatment of retinal degeneration and vision loss in patients with NCL. In this review, the key findings of different experimental approaches in NCL animal models aimed at attenuating progressive retinal degeneration and the decline in retinal function are discussed. Different approaches, including experimental enzyme replacement therapy, gene therapy, cell-based therapy, and immunomodulation therapy were evaluated and showed encouraging therapeutic benefits. Recent experimental ocular gene therapies in NCL animal models with soluble lysosomal enzyme deficiencies and transmembrane protein deficiencies have shown the strong potential of gene-based approaches to treat retinal dystrophies in NCLs. In CLN3 and CLN6 mouse models, an adeno-associated virus (AAV) vector-mediated delivery of CLN3 and CLN6 to bipolar cells has been shown to attenuate the retinal dysfunction. Therapeutic benefits of ocular enzyme replacement therapies were evaluated in CLN2 and CLN10 animal models. Since brain-targeted gene or enzyme replacement therapies will most likely not attenuate retinal neurodegeneration, there is an unmet need for treatment options additionally targeting the retina in patients with NCL. The long-term benefits of these therapeutic interventions aimed at attenuating retinal degeneration and vision loss in patients with NCL remain to be investigated in future clinical studies.

Characterization of neurological disease progression in a canine model of CLN5 neuronal ceroid lipofuscinosis

Golden Retriever dogs with a frameshift variant in CLN5 (c.934_935delAG) suffer from a progressive neurodegenerative disorder analogous to the CLN5 form of neuronal ceroid lipofuscinosis (NCL). Five littermate puppies homozygous for the deletion allele were identified prior to the onset of disease signs. Studies were performed to characterize the onset and progression of the disease in these dogs. Neurological signs that included restlessness, unwillingness to cooperate with the handlers, and proprioceptive deficits first became apparent at approximately 12 months of age. The neurological signs progressed over time and by 21 to 23 months of age included general proprioceptive ataxia, menace response deficits, aggressive behaviors, cerebellar ataxia, intention tremors, decreased visual tracking, seizures, cognitive decline, and impaired prehension. Due to the severity of these signs, the dogs were euthanized between 21 and 23 months of age. Magnetic resonance imaging revealed pronounced progressive global brain atrophy with a more than sevenfold increase in the volume of the ventricular system between 9.5 and 22.5 months of age. Accompanying this atrophy were pronounced accumulations of autofluorescent inclusions throughout the brain and spinal cord. Ultrastructurally, the contents of these inclusions were found to consist primarily of membrane‐like aggregates. Inclusions with similar fluorescence properties were present in cardiac muscle. Similar to other forms of NCL, the affected dogs had low plasma carnitine concentrations, suggesting impaired carnitine biosynthesis. These data on disease progression will be useful in future studies using the canine model for therapeutic intervention studies.

Aggregation chimeras provide evidence of in vivo intercellular correction in ovine CLN6 neuronal ceroid lipofuscinosis (Batten disease)

The neuronal ceroid lipofuscinoses (NCLs; Batten disease) are fatal, mainly childhood, inherited neurodegenerative lysosomal storage diseases. Sheep affected with a CLN6 form display progressive regionally defined glial activation and subsequent neurodegeneration, indicating that neuroinflammation may be causative of pathogenesis. In this study, aggregation chimeras were generated from homozygous unaffected normal and CLN6 affected sheep embryos, resulting in seven chimeric animals with varied proportions of normal to affected cells. These sheep were classified as affected-like, recovering-like or normal-like, based on their cell-genotype ratios and their clinical and neuropathological profiles. Neuropathological examination of the affected-like animals revealed intense glial activation, prominent storage body accumulation and severe neurodegeneration within all cortical brain regions, along with vision loss and decreasing intracranial volumes and cortical thicknesses consistent with ovine CLN6 disease. In contrast, intercellular communication affecting pathology was evident at both the gross and histological level in the normal-like and recovering-like chimeras, resulting in a lack of glial activation and rare storage body accumulation in only a few cells. Initial intracranial volumes of the recovering-like chimeras were below normal but progressively recovered to about normal by two years of age. All had normal cortical thicknesses, and none went blind. Extended neurogenesis was evident in the brains of all the chimeras. This study indicates that although CLN6 is a membrane bound protein, the consequent defect is not cell intrinsic. The lack of glial activation and inflammatory responses in the normal-like and recovering-like chimeras indicate that newly generated cells are borne into a microenvironment conducive to maturation and survival.

Cerebrospinal fluid neurofilament light chain levels in CLN2 disease patients treated with enzyme replacement therapy normalise after two years on treatment

Classic late infantile neuronal ceroid lipofuscinosis (CLN2 disease) is caused by a deficiency of tripeptidyl-peptidase-1. In 2017, the first CLN2 enzyme replacement therapy (ERT) cerliponase alfa (Brineura) was approved by the FDA and EMA. The CLN2 disease clinical rating scale (CLN2 CRS) was developed to monitor loss of motor function, language and vision as well as frequency of generalised tonic clonic seizures. Using CLN2 CRS in an open label clinical trial it was shown that Brineura slowed down the progression of CLN2 symptoms.

Neurofilament light chain (NfL) is a protein highly expressed in myelinated axons. An increase of cerebrospinal fluid (CSF) and blood NfL is found in a variety of neuroinflammatory, neurodegenerative, traumatic, and cerebrovascular diseases. We analysed CSF NfL in CLN2 patients treated with Brineura to establish whether it can be used as a possible biomarker of response to therapy. Newly diagnosed patients had CSF samples collected and analysed at first treatment dose and up to 12 weeks post-treatment to look at acute changes. Patients on a compassionate use programme who were already receiving ERT for approximately 1yr had CSF samples collected and NfL analysed over the following 1.3 years (2.3 years post-initiation of ERT) to look at long-term changes.

All newly diagnosed patients we investigated with classical late infantile phenotype had high NfL levels >2000 pg/ml at start of treatment. No significant change was observed in NfL up to 12 weeks post-treatment. After one year of ERT, two out of six patients still had high NfL levels, but all patients showed a continued decrease, and all had low NfL levels after two years on ERT. NfL levels appear to correspond and predict improved clinical status of patients on ERT and could be useful as a biomarker to monitor neurodegeneration and verify disease modification in CLN2 patients on ERT.

Glial Dysfunction and Its Contribution to the Pathogenesis of the Neuronal Ceroid Lipofuscinoses

While significant efforts have been made in developing pre-clinical treatments for the neuronal ceroid lipofuscinoses (NCLs), many challenges still remain to bring children with NCLs a cure. Devising effective therapeutic strategies for the NCLs will require a better understanding of pathophysiology, but little is known about the mechanisms by which loss of lysosomal proteins causes such devastating neurodegeneration. Research into glial cells including astrocytes, microglia, and oligodendrocytes have revealed many of their critical functions in brain homeostasis and potential contributions to neurodegenerative diseases. Genetically modified mouse models have served as a useful platform to define the disease progression in the central nervous system across NCL subtypes, revealing a wide range of glial responses to disease. The emerging evidence of glial dysfunction questions the traditional “neuron-centric” view of NCLs, and would suggest that directly targeting glia in addition to neurons could lead to better therapeutic outcomes. This review summarizes the most up-to-date understanding of glial pathologies and their contribution to the pathogenesis of NCLs, and highlights some of the associated challenges that require further research.

Advancing the Research and Development of Enzyme Replacement Therapies for Lysosomal Storage Diseases

With the increasing interest in developing gene therapies for rare diseases, it is easy to overlook that there are numerous rare lysosomal storage diseases (LSD) with treatments that have been approved by regulatory agencies in the United States and Europe. These primarily consist of enzyme replacement therapies (ERT), which are recombinant human proteins that are delivered for the life of the patient via different routes and may have distinct safety and distribution advantages over gene therapies. The research and development of ERT is a lengthy and expensive process, which is usually performed in academic laboratories before transfer to pharmaceutical companies and is hence a process ripe for disruption. There may still be considerable scientific and investment potential for ERT, however we need to develop a pipeline of proteins analogous to what has been created in some open science efforts as well as apply technologies to decrease manufacturing costs. In this Perspective, we illustrate the opportunity to fill the rare LSD treatment gap with ERTs while gene therapies are in development for these life-shortening diseases.

Diagnostic approach in adult-onset neurometabolic diseases

Neurometabolic diseases are a group of individually rare but numerous and heterogeneous genetic diseases best known to paediatricians. The more recently reported adult forms may present with phenotypes strikingly different from paediatric ones and may mimic other more common neurological disorders in adults. Furthermore, unlike most neurogenetic diseases, many neurometabolic diseases are treatable, with both conservative and more recent innovative therapeutics. However, the phenotypical complexity of this group of diseases and the growing number of specialised biochemical tools account for a significant diagnostic delay and underdiagnosis. We reviewed all series and case reports of patients with a confirmed neurometabolic disease and a neurological onset after the age of 10 years, with a focus on the 36 treatable ones, and classified these diseases according to their most relevant clinical manifestations. The biochemical diagnostic approach of neurometabolic diseases lays on the use of numerous tests studying a set of metabolites, an enzymatic activity or the function of a given pathway; and therapeutic options aim to restore the enzyme activity or metabolic function, limit the accumulation of toxic substrates or substitute the deficient products. A quick diagnosis of a treatable neurometabolic disease can have a major impact on patients, leading to the stabilisation of the disease and cease of repeated diagnostic investigations, and allowing for familial screening. For the aforementioned, in addition to an exhaustive and clinically meaningful review of these diseases, we propose a simplified diagnostic approach for the neurologist with the aim to help determine when to suspect a neurometabolic disease and how to proceed in a rational manner. We also discuss the place of next-generation sequencing technologies in the diagnostic process, for which deep phenotyping of patients (both clinical and biochemical) is necessary for improving their diagnostic yield.

Neuronal Ceroid Lipofuscinosis: The Multifaceted Approach to the Clinical Issues, an Overview

The main aim of this review is to summarize the current state-of-art in the field of childhood Neuronal Ceroid Lipofuscinosis (NCL), a group of rare neurodegenerative disorders. These are genetic diseases associated with the formation of toxic endo-lysosomal storage. Following a brief historical review of the evolution of NCL definition, a clinically-oriented approach is used describing how the early symptoms and signs affecting motor, visual, cognitive domains, and including seizures, may lead clinicians to a rapid molecular diagnosis, avoiding the long diagnostic odyssey commonly observed. We go on to focus on recent advances in NCL research and summarize contributions to knowledge of the pathogenic mechanisms underlying NCL. We describe the large variety of experimental models which have aided this research, as well as the most recent technological developments which have shed light on the main mechanisms involved in the cellular pathology, such as apoptosis and autophagy. The search for innovative therapies is described. Translation of experimental data into therapeutic approaches is being established for several of the NCLs, and one drug is now commercially available. Lastly, we show the importance of palliative care and symptomatic treatments which are still the main therapeutic interventions.

Pacemaker Implantation in Juvenile Neuronal Ceroid Lipofuscinosis (CLN3)–A Long-Term Follow-Up Study

It is well documented that deteriorating heart function due to deposition of ceroid lipopigment is a significant co-morbidity in Juvenile Neuronal Ceroid Lipofuscinosis (CLN3 disease) although the exact disease mechanisms remain unknown in any NCL form. An increasing frequency of cardiac conduction disorders including severe bradycardia and sinus arrest is seen in the late teens, as is a left ventricular hypertrophy in the early 20s. Only a few case reports of pacemaker implantation have been published, and so far, no long-term follow-up study exists. As new treatment options emerge, more patients will live longer and the need for pacemaker will likely increase, why knowledge of long-term outcome is needed. In the present study, we present the course of six patients from the original Danish CLN3-heart population study (n = 29) published in 2011 in whom pacemaker implantation was indicated from a cardiac point of view. In two cases, the families deselected pacemaker implantation. In four males, aged 19-29 years, all having a good general condition, a dual-chamber pacemaker (St. Jude Medical™ Accent/Assurity MRI™) was implanted in general anesthesia without any complications. At follow-up 9 years later, three were still alive. According to the parents' opinion they still have a good quality of life, now 26, 30, and 36 years old. Pacemaker treatment is safe and may have great impact on quality of life. However, the medical indication for pacemaker treatment is relative and it is important that various aspects, including the patient's general condition and family preferences, are thoroughly discussed before making the final decision.

Rare diseases - rare outcomes: Assessing communication abilities for the developmental and epileptic encephalopathies

OBJECTIVE

Developmental and epileptic encephalopathies (DEE) entail moderate to profound communication and other impairments that are poorly measured by typical clinical outcomes assessments (COA). We examined the potential of alternative approaches, specifically, the use of raw scores and COAs outside of their intended age ranges.

METHODS

In a cross-sectional survey, 120 parents of children with Dravet Syndrome, Lennox-Gastaut syndrome, KCNQ2-DEE, KCNB1-DEE, and SCN2A-DEE (ages 1-35 years) completed the Adaptive Behavior Assessment System-3 for ages 0-5 years, modified checklist for autism (mCHAT), communication and social behavior scales (CSBS), communication matrix (CM), and several parent-reported classifiers of communication. Adaptive Behavior Assessment System communication and social raw scores were the primary and adjunctive outcomes. Floor and ceiling effects, dispersion and convergence with related measures were assessed with appropriate parametric and nonparametric statistical techniques.

RESULTS

Median chronological age (CA) was 8.7 years (Interquartile range (IQR): 5.3-13.5). Adaptive Behavior Assessment Systemcommunication and social age equivalents were 12.5 months (IQR 7.5-28) and 16.5 months (IQR 9-31). Most raw scores corresponded to standardized scores indicating performance <3 standard deviations below the general population mean. Adaptive Behavior Assessment System raw scores demonstrated minimal floor and ceiling effects (<1-2.5%). In linear regression models, scores correlated with age under 6 years (communication, p = 0.001; social, p = 0.003) but significantly flattened out thereafter. Scores varied substantially by DEE group (both p < 0.001) and decreased with higher convulsive seizure frequency (communication, p = 0.01, social, p = 0.02). There was good convergence with mCHAT, CSBS, and CM scores (all r > 0.8).

SIGNIFICANCE

Raw scores and out-of-range COAs may provide measures that are sensitive at the very limited levels of functioning typical of profoundly impaired, older patients with DEEs. To ensure that targeted trial outcomes are responsive to meaningful change, development of these approaches will be essential to clinical trial readiness for novel therapies for rare DEEs.

Plasma neurofilament light, glial fibrillary acidic protein and lysosphingolipid biomarkers for pharmacodynamics and disease monitoring of GM2 and GM1 gangliosidoses patients

GM2 and GM1 gangliosidoses are genetic, neurodegenerative lysosomal sphingolipid storage disorders. The earlier the age of onset, the more severe the clinical presentation and progression, with infantile, juvenile and late-onset presentations broadly delineated into separate phenotypic subtypes. Gene and substrate reduction therapies, both of which act directly on sphingolipidosis are entering clinical trials for treatment of these disorders. Simple to use biomarkers for disease monitoring are urgently required to support and expedite these clinical trials. Here, lysosphingolipid and protein biomarkers of sphingolipidosis and neuropathology respectively, were assessed in plasma samples from 33 GM2 gangliosidosis patients, 13 GM1 gangliosidosis patients, and compared to 66 controls. LysoGM2 and lysoGM1 were detectable in 31/33 GM2 gangliosidosis and 12/13 GM1 gangliosidosis patient samples respectively, but not in any controls. Levels of the axonal damage marker Neurofilament light (NF-L) were highly elevated in both GM2 and GM1 gangliosidosis patient plasma samples, with no overlap with controls. Levels of the astrocytosis biomarker Glial fibrillary acidic protein (GFAP) were also elevated in samples from both patient populations, albeit with some overlap with controls. In GM2 gangliosidosis patient plasma NF-L, Tau, GFAP and lysoGM2 were all most highly elevated in infantile onset patients, indicating a relationship to severity and phenotype. Plasma NF-L and liver lysoGM2 were also elevated in a GM2 gangliosidosis mouse model, and were lowered by treatment with a drug that slowed disease progression. These results indicate that lysosphingolipids and NF-L/GFAP have potential to monitor pharmacodynamics and pathogenic processes respectively in GM2 and GM1 gangliosidoses patients.

Natural History Studies in NCL and Their Expanding Role in Drug Development: Experiences From CLN2 Disease and Relevance for Clinical Trials

Conducting clinical trials in rare diseases is challenging. In trials that aim to use natural history control cohorts for evaluation of efficacy, lack of data on natural history of disease prolongs development of future therapies significantly. Therefore, collection of valid natural history data in clinical settings is needed to advance drug development. These data need to fulfill requirements on type of collection, quantifiable measures on the course of disease, verification and monitoring as well as compliance to strict data protection and sharing policies. Disease registries can be a source for patient data. Late-infantile CLN2 disease is characterized by rapid psychomotor decline and epilepsy. Natural-history data of 140 genotype-confirmed CLN2 patients from two independent, international cohorts were analyzed in a natural history study. Both datasets included quantitative ratings with disease-specific clinical scores. Among 41 patients for whom longitudinal assessments spanning an extended disease course were available within the DEM-CHILD DB (an international NCL disease patient database, NCT04613089), a rapid loss of motor and language abilities was documented in quantitative detail. Data showed that the course of disease in late-infantile CLN2 disease is highly predictable with regard to the loss of language and motor function and that the results were homogeneous across multiple and international sites. These data were accepted by EMA and FDA as valid natural-history controls for the evaluation of efficacy in experimental therapies for CLN2 disease and led to an expedited approval of intracerebroventricular enzyme replacement therapy with cerliponase alpha in May 2017.

Neurophysiological Findings in Neuronal Ceroid Lipofuscinoses

Neuronal ceroid lipofuscinoses (NCLs) are a heterogeneous group of neurodegenerative diseases, characterized by progressive cerebral atrophy due to lysosomal storage disorder. Common clinical features include epileptic seizures, progressive cognitive and motor decline, and visual failure, which occur over different time courses according to subtypes. During the latest years, many advances have been done in the field of targeted treatments, and in the next future, gene therapies and enzyme replacement treatments may be available for several NCL variants. Considering that there is rapid disease progression in NCLs, an early diagnosis is crucial, and neurophysiological features might have a key role for this purpose. Across the different subtypes of NCLs, electroencephalogram (EEG) is characterized by a progressive deterioration of cerebral activity with slowing of background activity and disappearance of spindles during sleep. Some types of heterogeneous abnormalities, diffuse or focal, prevalent over temporal and occipital regions, are described in many NCL variants. Photoparoxysmal response to low-frequency intermittent photic stimulation (IPS) is a typical EEG finding, mostly described in CLN2, CLN5, and CLN6 diseases. Visual evoked potentials (VEPs) allow to monitor the visual functions, and the lack of response at electroretinogram (ERG) reflects retinal neurodegeneration. Taken together, EEG, VEPs, and ERG may represent essential tools toward an early diagnosis of NCLs.

[Precision medicine in pediatric neurology exemplified by the new treatment forms]

BACKGROUND

In recent years the possibilities for molecular diagnostics and treatment of rare childhood diseases have greatly improved. The first gene-modifying drugs have now been approved, leading to a new era of precision treatment in pediatric neurology.

OBJECTIVE

This article describes the dynamic developments of precision medicine in pediatric neurology in the areas of prevention, diagnostics and targeted treatment.

DISCUSSION

The paradigm shift as a result of precision medicine is based on a treatment approach focused more strongly on the individual and the corresponding unique characteristics. Modern methods of genetic and molecular diagnostics are used to accurately describe and characterize affected children, complemented by a precise description of the clinical phenotype. Nevertheless, the success of the best individual treatment strategy derived from this information is often dependent on the time of diagnosis. Therefore, methods for disease prevention, particularly newborn screening programs, become increasingly more important to achieve the best possible success of novel therapies even before the onset of disease symptoms. In addition to a precise stratification of therapies, special attention should be paid in the future to the consideration of the individual perspective of patients and parents/guardians. Furthermore, a normative framework for a quality-ensured application of gene-modifying therapies in the German healthcare system must be created.

Aberrant upregulation of the glycolytic enzyme PFKFB3 in CLN7 neuronal ceroid lipofuscinosis

CLN7 neuronal ceroid lipofuscinosis is an inherited lysosomal storage neurodegenerative disease highly prevalent in children. CLN7/MFSD8 gene encodes a lysosomal membrane glycoprotein, but the biochemical processes affected by CLN7-loss of function are unexplored thus preventing development of potential treatments. Here, we found, in the Cln7∆ex2 mouse model of CLN7 disease, that failure in autophagy causes accumulation of structurally and bioenergetically impaired neuronal mitochondria. In vivo genetic approach reveals elevated mitochondrial reactive oxygen species (mROS) in Cln7∆ex2 neurons that mediates glycolytic enzyme PFKFB3 activation and contributes to CLN7 pathogenesis. Mechanistically, mROS sustains a signaling cascade leading to protein stabilization of PFKFB3, normally unstable in healthy neurons. Administration of the highly selective PFKFB3 inhibitor AZ67 in Cln7∆ex2 mouse brain in vivo and in CLN7 patients-derived cells rectifies key disease hallmarks. Thus, aberrant upregulation of the glycolytic enzyme PFKFB3 in neurons may contribute to CLN7 pathogenesis and targeting PFKFB3 could alleviate this and other lysosomal storage diseases.

Impact of the COVID-19 pandemic on access to the cerliponase alfa managed access agreement in England for CLN2 treatment

BACKGROUND

Cerliponase alfa, an enzyme replacement therapy for neuronal ceroid lipofuscinosis type 2 (CLN2), is currently available in England through a managed access agreement (MAA). It is administered every 2 weeks via an intracerebroventricular device. Here we report qualitative research with families of children with CLN2 disease and healthcare professionals (HCPs) who run the MAA, to understand how access to cerliponase alfa via the MAA at Great Ormond Street Hospital (GOSH) in London, and the overall management of CLN2 disease, was affected during the coronavirus disease 2019 (COVID-19) pandemic.

METHODS

Telephone interviews were conducted with nine families, representing 11 children with CLN2 disease, and two HCPs in November and December 2020.

RESULTS

Children had received cerliponase alfa treatment for a mean (SD) of 23.1 ± 24.7 months (7.1 ± 4.6 months in the MAA). Families travelled 7-398 km for treatment (mean 210 ± 111 km). Treatment with cerliponase alfa was designated "essential" by GOSH and continued as normal during the pandemic but with extra safety precautions, and no children missed any treatments. Families were highly motivated to continue treatment, despite considerable anxiety about the risk of coronavirus infection from travelling and staying overnight but were reassured by communications from GOSH and the safety precautions put in place. Support therapy services were widely compromised, causing families concern about deterioration in their children's condition. Families were confused about COVID-19 testing and shielding, and were unclear whether children with CLN2 disease were vulnerable to COVID-19.

CONCLUSIONS

Looking forward, advice for children with CLN2 disease should be specific and tailored, taking into account the family unit. Support therapies should be considered essential alongside cerliponase alfa treatment.

Intravitreal gene therapy restores the autophagy-lysosomal pathway and attenuates retinal degeneration in cathepsin D-deficient mice

Loss of vision due to progressive retinal degeneration is a hallmark of neuronal ceroid lipofuscinoses (NCL), a group of fatal neurodegenerative lysosomal storage diseases. Enzyme substitution therapies represent promising treatment options for NCLs caused by dysfunctions of soluble lysosomal enzymes. Here, we compared the efficacy of a cell-based enzyme substitution strategy and a gene therapy approach to attenuate the retinal pathology in cathepsin D- (CTSD) deficient mice, an animal model of CLN10 disease. Levels of enzymatically active CTSD in mutant retinas were significantly higher after an adeno-associated virus vector-mediated CTSD transfer to retinal glial cells and retinal pigment epithelial cells than after intravitreal transplantations of a CTSD overexpressing clonal neural stem cell line. In line with this finding, the gene therapy treatment restored the disrupted autophagy-lysosomal pathway more effectively than the cell-based approach, as indicated by a complete clearance of storage, significant attenuation of lysosomal hypertrophy, and normalized levels of the autophagy marker sequestosome 1/p62 and microtubule-associated protein 1 light chain 3-II. While the cell-based treatment did not prevent the rapidly progressing loss of various retinal cell types, the gene therapy approach markedly attenuated retinal degeneration as demonstrated by a pronounced rescue of photoreceptor cells and rod bipolar cells.