#MSDCon2024

Multiple sulfatase deficiency (MSD) is an ultra-rare, fatal neurodegenerative disorder with emerging therapeutic options. This includes an AAV9-based approach recently funded through the Foundation for the NIH Bespoke Gene Therapy Program (PIs Adang, Ahrens-Nicklas) as well as a drug repurposing strategy in Europe (PI: Schlotawa, Remedi4All). MSD is the result of dysfunctional sulfatase activation by SUMF1-encoded formylglycine-generating enzyme (FGE). The resulting phenotype arises from the combined of loss of activity of all sulfatases, although the primary neurologic impact is from loss of the enzymes associated with mucopolysaccharidosis III (MPS IIIA/D) and metachromatic leukodystrophy (MLD). The spectrum of neurologic disease includes a common subtype with stereotyped regression during the toddler years, similar to late infantile MLD. Children also experience an accumulating burden of systemic disease, which can include ichthyosis, hepatosplenomegaly, and dysostosis multiplex. With several investigational drug candidates undergoing clinical planning, there is an urgent unmet need to identify optimal patient-centric clinical endpoints.

Our prior work defined distinct phenotypes of MSD (severe and attenuated), which correlate with genotype and a novel biomarker, glucosaminoglycan non-reducing ends (GAG-NREs). Despite its rarity, we have enrolled more than 40 children in our ongoing natural history study, which represents a large proportion of the known global population. This ongoing study includes collection of historical medical records, longitudinal administration of clinical outcome assessments (COA) in parallel with the collection of biospecimens. This work leverages the resources of the Rare Disease Clinical Research Network (RDCRN)-funded Global Leukodystrophy Initiative Clinical Trials Network (GLIA-CTN), which supports the regulatory infrastructure of the MSD natural history study. The disease severity and complexity of MSD requires a patient-centric approaches for clinical trial design, utilizing concepts of interest most meaningful to patients and families.

Sulfatases catalyze essential cellular reactions, including degradation of glycosaminoglycans (GAGs). All sulfatases are post-translationally activated by the formylglycine generating enzyme (FGE) which is deficient in Multiple Sulfatase Deficiency (MSD), a neurodegenerative lysosomal storage disease. Historically, patients were presumed to be deficient of all sulfatase activities; however, a more nuanced relationship is emerging. Each sulfatase may differ in their degree of post-translational modification by FGE, which may influence the phenotypic spectrum of MSD. Here, we evaluate if residual sulfatase activity and accumulating GAG patterns distinguish cases from controls and stratify clinical severity groups in MSD. We quantify sulfatase activities and GAG accumulation using three complementary methods in MSD participants. Sulfatases differed greatly in their tolerance of reduction in FGE-mediated activation. Enzymes that degrade heparan sulfate (HS) demonstrated lower residual activities than those that act on other GAGs. Similarly, HS-derived urinary GAG subspecies preferentially accumulated, distinguished cases from controls, and correlated with disease severity. Accumulation patterns of specific sulfatase substrates in MSD provide fundamental insights into sulfatase regulation and will serve as much-needed biomakers for upcoming clinical trials. This work highlights that biomarker investigation of an ultra-rare disease can simultaneously inform our understanding of fundamental biology and advance clinical trial readiness efforts.

Encoded by the SUMF1 gene, the Formylglycine Generating Enzyme (FGE) is inactivated by mutation in virtually all Multiple Sulfatase Deficiency (MSD) cases. These mutations generally reduce the stability of FGE, preventing it to adopt a functional fold and perform its normal cellular function, that is the downstream activation of the sulfatases enzymes by post-translational modification. FGE inactivation is a hallmark of MSD.

Our work focuses on the search of ligands binding at the surface of FGE. We hypothesise that these ligands, when optimised, will act as “pharmacological chaperones” or “molecular plasters”, stabilising the fold and function of FGE mutants found in MSD, and reactivating their cellular function. With our collaborators, we have combined compounds screening assays to identify hit molecules as starting points, molecular modelling and chemical synthesis for synthetic optimisation, and cellular assays to determine the cellular mode of action and therapeutic potential of the new molecules/compounds identified. We will present our progress and recent results in our search of small molecule reactivators of FGE, along with the challenges encountered and future opportunities. We will disclose our recent findings on the “druggability” of FGE using fragment screening and X-ray crystallography, and our latest efforts to use this knowledge for the assembly of higher affinity ligands to stabilise FGE. Finally, we will also discuss the design/preparation/evaluation of Tazarotene and Bexarotene derivatives, two previously FDA approved drugs which were recently shown to upregulate FGE activity (though via a distinct/indirect cellular mechanism) an structure-activity relationship (SAR) data gathered to date.

The Newborn Screening system is complex with many stakeholders involved, and it can be difficult to know where families can make a difference. Learn more about Newborn Screening (including details about how the system works), why coalition building with the Metachromatic Leukodystrophy community will be critical for MSD, and how a collaborative approach can change everything.

Multiple Sulfatase Deficiency (MSD) is an ultra-rare lysosomal storage disorder (LSD)caused by mutations in the SUMF1 gene. The SUMF1 gene encodes formylglycine-generated enzyme (FGE), the protein responsible for activating all sulfatases in the cell. The reduction or complete loss of FGE causes detrimental accumulation of sulfated substrates in the lysosome, including glycosaminoglycans (GAGs), sulfolipids, and steroid sulfates. Neurological regression is a primary clinical feature of MSD, which suggests that neural cell types are particularly intolerant to dysfunctional lysosomal flux. Therapeutics targeting MSD are currently limited, and there is an urgent need for a reproducible in vitro model of MSD that recapitulates biochemical phenotypes seen in the patient population. To fulfill this need, we recently generated NGN2-induced neurons (NGN2-iN) from induced pluripotent stemcells (iPSC) derived from a patient with MSD. We use a battery of biochemical and molecular techniques to demonstrate that our model reproduces biochemical phenotypes associated with MSD. Patient NGN2-iN display hallmark pathology of MSD seen in humans, including reduced activity of multiple sulfatases and lysosomal accumulation as compared to isogenic controls. Over time, these neuronsalso demonstrate progressive accumulation of GAG subspecies associated with mucopolysaccharidosis type III. Interestingly, these phenotypes worsen in more mature (Day 11) MSD NGN2-iN, as compared to immature (Day 3) MSD NGN2-iN andiPSCs. This observation suggests that neurons are selectively vulnerable to the loss of FGE, and that dysfunction worsens over neuronal maturation. We anticipate that our model will be utilized to compare the selective vulnerability of individual CNS cell types, further our current understanding of MSD pathophysiology, and ultimately aid the development of therapeutics.

Over 10,000 known diseases are characterized as “rare” affecting fewer than 200,000 people in the United States. Collectively, these diseases affect about 30 million people in the United States – a significant proportion of the population. About 80% of rare diseases are monogenic where known alterations in a single gene are responsible for the clinical manifestations that result in significant morbidity and mortality. Monogenic diseases are potential candidates for gene therapies because the defective gene can be corrected or replaced thereby restoring gene function and stopping or reversing the disease state. Gene therapies have the potential to provide long-term benefit for patients where there currently is no treatment – a prospect that would be transformational in the treatment of many serious and life-threatening rare disorders.

The Bespoke Gene Therapy Consortium (BGTC) was formed by the Foundation for the National Institutes of Health (FNIH) as part of the Accelerating Medicines Partnership® programs to address the challenge of developing AAV gene therapies for diseases of no commercial interest. It brings together 35 member organizations, including the NIH, FDA, life sciences / biopharmaceutical companies, nonprofits, and patient advocacy groups to collaborate in a pre-competitive space. These partners possess extensive experience in designing, developing and manufacturing AAV-based gene therapies for use in clinical trials.

One objective of the BGTC is to streamline navigation of the regulatory pathway for AAV gene therapies.

To achieve this objective, BGTC has developed a Regulatory Playbook, which is a collection of resources and best practices that reflect a sponsor’s typical regulatory journey from research and development (R&D) to pre-clinical through clinical development and ID preparation/submission. BGTC released playbook version 1.0 on February 6, 2024 to provide an initial framework for gene therapy developers. Subsequent playbook versions will incorporate learnings from up to eight rare disease clinical trials being that are part of the BGTC portfolio. With the BGTC leading the charge and drawing upon the collective experience, expertise, and passion of the scientific community, this playbook aims to serve as a guiding light, enabling researchers and developers to bring safe, effective, and transformative gene therapies to patients in need.

Multiple Sulfatase Deficiency (MSD) is an ultra-rare lysosomal storage disorder associated with pathogenic variants in the SUMF1 gene, which is required for sulfatase activation. Despite the known severity of disease, the impact of MSD on affected children, caregivers, and their family is uncharacterized.

Nineteen families affected by MSD participated in our assessments. The Vineland Adaptive Behavior Scales (VABS-3) was administered by a child neurologist to caregivers in the context of an affected individual’s in-person or remote research encounter. Health-related quality of life (HRQOL) surveys were collected electronically, including the Caregiver Priorities and Child Health Index of Life with Disabilities (CPCHILD), Pediatric Quality of Life Inventory Generic Core Scales (PedsQL GC), PedsQL Family Impact Module (FIM), and the Traumatic Brain Injury Caregiver Quality of Life (CareQOL) questionnaires.

All clinical outcome measures demonstrated a range of performance. Most caregivers assessed their children as severely affected (VABS-3 <40 Standard Score across all Domains and Adaptive Behavior Composite Score: n=10/19; 52.63%), with the lowest median scores in the Communication and Motor Skills domains. The Communication domain’s mean performance was significantly lower than the Socialization and Daily Living Skills domains. The Motor Skills domain was significantly lower than the Socialization domain only. The CPCHILD (n=12) identified items within the Comfort and Emotions and Overall Health domains as top priorities when preserving affected individuals’ quality of life. The Comfort and Emotions domain’s mean performance was significantly higher than all other domains. The CPCHILD overall HRQOL remained high (median 80%, IQR 50%). The PedsQL GC (n=14) demonstrated higher mean performance in the Emotional than the School/Work domain only. The CareQOL (n=15) identified caregivers’ significantly higher frequency of a sense of loss for the affected individual and feelings of entrapment. The PedsQL FIM (n=13) demonstrated that there was no significant difference between family functioning and parent HRQOL performance.

In this study, we demonstrated that MSD has profound, global effects on both affected individuals and their caregivers as measured by the VABS-3 and HRQOL surveys. This data will be integral to identifying Health Concepts and related Concept of Interests to inform future clinical trial design.

The assay for newborn screening of MLD is well developed. A pilot study on 30,000 newborns in Washington state found 1 case of high prognosis for MLD, no false positives. Data shows that 40 out of 40 newborn blood spots from patients who were diagnosed with MLD tested positive in this assay suggesting that the false negative rate is essentially zero. Subsequently, pilot studies have started in UK, France, Italy, Germany, and Austria. In Germany, 4 cases with high prognosis for MLD were identified, those with early onset disease proceeded toward treatment channels.

Newborn screening for MLD can be readily multiplexed using mass spectrometry with other lysosomal diseases that have been recently added to expanded newborn screening panels. Reagents including quality control materials are available for use by newborn screening laboratories.

Limited data suggest that MSD patients will be picked up during newborn screening of MLD, but additional data using newborn blood spots is important to confirm this observation.

Multiple Sulfatase Deficiency (MSD) is a rare autosomal recessive disorder characterized by deficient enzymatic activity of all known sulfatase. MSD patients frequently carried two loss of function mutations in the SUMF1 gene, encoding a sulfatase modifying factor which activates 17 different sulfatases. MSD patients shown common features of mucopolysaccharidosis, and metachromatic leukodystrophy, including neurologic impairments, developmental delay, and visceromegaly. There are currently no approved therapies for MSD patients. Gene therapy may provide a meaningful and long-term therapeutic benefit for MSD patients by delivering a functional copy of the SUMF1 gene to patient cells. We developed a self-complementary vector encoding a codon-optimized human SUMF1 gene (scAAV9/SUMF1), the unaltered design of which could be appropriate for human use. Using a severe Sumf1 knock-out (KO) mouse model of MSD, we tested the benefits of treatment with our vector in mice shortly after birth and later in the disease course by administering virus into the cerebrospinal fluid (CSF) alone or in combination with an intravenous injection. CSF administration of scAAV9/SUMF1 was sufficient to rescue early lethality, normalize behavior and improve newly identified visual and cardiac dysfunctions in KO mice, even when given at an advanced disease stage. We found dose-dependent and long-term restoration of sulfatase activity in tissues, which is accompanied by decreased accumulation of glycosaminoglycans, lysosomal defects and neuroinflammation in the brain. Even at the highest dose tested, scAAV9/SUMF1 was well-tolerated without toxicity from high transgenic SUMF1 expression in KO and wild-type mice or in rats that were treated as part of a GLP-toxicology study. Overall, our preclinical results attest to the safety of scAAV9/SUMF1 delivery and predict a benefit of this treatment to MSD patients.

AAV9/SUMF1 gene therapy is being considered as a treatment for Multiple Sulfatase Deficiency. A GLP toxicology study to evaluate the safety of AAV9/SUMF1 in rats, following lumbar intrathecal (IT) or cisterna magna (ICM) administration, was carried out by Charles River Laboratories. Cohorts consisted of 5 males and 5 females, injected with AAV9/SUMF1 (5E11, 2E12, and 4.8E12 vg/rat IT, as well as 2E12 vg/rat ICM), and animals were examined twice daily for mortality/moribundity along with a detailed clinical examination and weight acquisition performed weekly. Cohorts were sacrificed at 29 days to evaluate tolerability of AAV9/SUMF1 at the peak of transgene expression for acute toxicities. A long-term cohort was sacrificed at 181 days post-administration to evaluate signs of long-term adverse effects and/or possible resolution of short-term findings. Overall, the study conclusion was that AAV9/SUMF1 was well-tolerated across both time points and all doses. No difference was seen in the findings of the IT versus ICM groups. Findings are as follows for each dose group at the day 29 time point: 5E11 vg: low-grade spinal nerve root degeneration. 2E12 vg: Minimal severity inflammation/degeneration of lumbar and thoracic dorsal root ganglia (DRG), occasional spinal nerve root degeneration, and low-grade white matter degeneration. 4.8E12 vg: Similar histology findings as with the 2×1012 vg IT group, but trending slightly higher incidence/severity (occasional moderate severity findings); also minor maturation delays in peripheral sensory nerve conduction were observed, but graded as negligible and not neuropathic. All findings were partially or fully resolved by day 181.

With the announcement of the Bespoke Grant in May 2023, which will fund Phase I/II clinical trials for AAV9 gene therapy, the United MSD Foundation has an opportunity to examine its funding strategy for MSD research projects. Inspired by the Sanfilippo Children’s Foundation’s Global Research Roadmap, the Foundation has begun drafting its own Research Strategy Map to guide its funding over the next 5 years. The first draft of this Research Strategy Map will be presented and the patient family and research communities will have an opportunity to respond and shape the final document.

REMEDi4ALL (repurposing medicines for all) is an European Union-funded research initiative to aimed to create a sustainable and globally connected platform and drive forward the repurposing of medicines in Europe. The REMEDi4ALL consortium (https://remedi4all.org/) brings together a unique combination of expertise to address the complexities of drug repurposing with capacities accessible to the research community. Led by EATRIS, the European infrastructure for translational medicine (Ussi et al., 2017), (Gilliland et al., 2016), (https://eatris.eu/), 24 organizations have joined forces to build a alleviate systemic bottlenecks in drug repurposing. It aims to construct an integrated platform encompassing advanced drug research facilities with clinical and translational research expertise, clinical operations, patient engagement methodologies, education & training, regulatory experts, health technology assessment, building a globally connected community of practice that will also include a network of funders.

As a disease-agnostic and patient-centric platform, REMEDi4ALL has the potential to boost drug repurposing or repositioning of already approved, discontinued, shelved or investigational therapeutics by improving the ecosystem in Europe as well as globally. Its ultimate aim is to unlock the full potential drug repurposing by reducing development times and costs for new therapeutic opportunities for conditions with high unmet need.

REMEDi4ALL launched in late 2022 with 4 initial drug repurposing projects, including one focused on MSD, in various development stages and addressing different challenges in drug repurposing (e.g., drug screening, reformulation, combination therapy and multinational clinical trials) and in different disease areas (e.g., oncology, infectious disease, ultra-rare genetic diseases). The philosophy of the platform is to work with multidisciplinary teams in a targeted and patient-centric manner and for each project focus on the critical path to bring an existing drug substance or drug product through the approval process and into clinical practice.

Gilliland, C. T., Zuk, D., Kocis, P., Johnson, M., Hay, S., Hajduch, M., et al. (2016). Putting translational science on to a global stage. Nat Rev Drug Discov 15, 217–8. doi: 10.1038/nrd.2016.33.

Ussi, A. E., de Kort, M., Coussens, N. P., Aittokallio, T., and Hajduch, M. (2017). In Search of System-Wide Productivity Gains – The Role of Global Collaborations in Preclinical Translation. Clin Transl Sci 10, 423–425. doi: 10.1111/cts.12498.

Background:
The key defect in Multiple Sulfatase Deficiency (MSD) is the loss of function of an essential protein called formylglycine-generating enzyme (FGE). In MSD patients, mutations in the gene coding for FGE compromise FGE’s function, often due to incorrect protein folding and low intracellular protein stability. We want to develop drug candidates that stabilize FGE in cells and thereby rescue its function. The binding of a small molecule to a protein often increases the protein’s stability. Hence, we plan to develop small molecule drugs that bind to FGE and stabilize its structure. Such molecules are called pharmacological chaperones. Pharmacological chaperones have recently become a treatment option for other lysosomal storage diseases. For example, Migalastat was approved for treatment of Fabry’s disease.

Results:
We use purified FGE protein to search for very small molecules, so-called fragments, which snuggly bind to grooves on the surface of FGE. So far, we have tested around 600 fragments and found more than two dozen fragments that bind to FGE. Fragments are smaller than usual drugs and their binding to FGE is generally not strong enough to result in sufficient stabilization of FGE. Therefore, the small fragments serve as starting point for optimization into larger and tighter-binding drug-like molecules. Our collaborators from medicinal chemistry perform this optimization. For efficient optimization, structural information about the interaction between the fragments and FGE is essential. X-ray crystallography, the method that we use to search for FGE-binding fragments, does reveal where on FGE a small molecule binds and which atoms of the molecule are presumably important for the binding. Our experiments showed that most of the fragments bind to one of four specific sites on FGE. Three of these sites are different from the active site, suggesting that their binding will not impair FGE’s normal function, i.e. the activation of its sulfatase substrates. Our results suggest that FGE should be druggable, i.e. the development of pharmacological chaperones should be possible in principle. Moreover, the almost 30 fragments that we found to bind to FGE and the detailed visualization of their binding mode is a treasure trove for medicinal chemists to rationally design larger optimized molecules that will eventually be tested for their therapeutic effect in cell culture or in animal models for MSD.

Background:
Multiple sulfatase deficiency (MSD) is an ultra-rare, inherited lysosomal storage disorder characterized by the functional deficiency of all sulfatase enzymes. MSD is caused by mutations in the gene SUMF1, encoding a sulfatase modifying factor that activates 17 downstream sulfatases. MSD patients present with combined features of single-sulfatase disorders such as the mucopolysaccharidoses and metachromatic leukodystrophy (MLD). Currently, there are no disease-modifying therapies for MSD. We aimed to develop ex vivo gene therapy with hematopoietic stem cell transplant for MSD, as this approach has proven successful for related disorders.

Methods:
We designed lentiviral vectors encoding either 1) SUMF1 or 2) a downstream sulfatase ARSA that is greatly implicated in the disease. ARSA ex vivo gene therapy is approved by the EMA for MLD and has the potential to be repurposed for patients with MSD.

Results:
In vitro, MSD patient fibroblasts transduced with the lentiviral vectors demonstrated improved biochemical phenotypes including rescue of sulfatase activities and glycosaminoglycan (GAG) accumulation. In vivo, both lentiviral vectors proved efficacious in rescuing biochemical and behavioral phenotypes in MSD mice that underwent hematopoietic stem cell transplant with ex vivo gene therapy. To further augment outcomes, we co-transduced MSD patient fibroblasts with both SUMF1 and ARSA vectors and found that co-expressing these transgenes greatly enhanced biochemical rescue in vitro. We will present the results of our ongoing work evaluating the efficacy of this innovative dual-transgene approach in MSD mice after ex vivo gene therapy.

Background:
Multiple sulfatase deficiency (MSD) is an exceptionally rare neurodegenerative disorder due to the absence or deficiency of 17 known cellular sulfatases. Two siblings with attenuated MSD underwent hematopoietic cell transplantation (HCT), evaluating the possibility of lysosomal enzymatic cross-correction from the donor cells.

Methods:
A retrospective data analysis was done on the two siblings who underwent HCT. The data collected included biomarkers including urine glycosaminoglycans, urine sulfatides, untargeted metabolomics in plasma and enzyme assays. The data from neuropsychology evaluation was also collected up to 3 years after HCT.

Results:
Biochemical correction of all the previously deficient enzyme activity in the leukocytes was evident within 3 months post HCT. Urine heparan and dermatan sulfate along with urine sulfatides were normal in the pre and post HCT samples due to the milder phenotype. While single, unique biomarkers were not identified for MSD, multiple consistent metabolic perturbations across patients were noted. Specifically, glycerophospholipids constituted the predominant category of perturbed sub-pathways in both siblings. Arylsulfates and fatty acids and derivatives, exhibited substantial perturbations, representing the second or third largest proportion of perturbed metabolites across the siblings. Additionally, energy-related sub-pathways such as bile acids, cholesterols, sterols, nucleotides, and various amino acids were disrupted. Notably, the relative levels of disruption across these sub-pathways between the siblings are consistent. These results indicate that MSD induces a broad state of metabolic dysregulation. The impact of HCT were monitored by comparing metabolomic profiles pre- and post-HCT. An almost instant neutralization effect introduced by HCT was observed. The correction of abnormalities was further quantitatively analyzed in every sequential post-HCT samples, while the initial post-HCT samples collected at 3 months showed a significant correction, with more than 70% of abnormal concentration levels falling within the normal range. This correction persisted in subsequent post-HCT samples, demonstrating the effectiveness of HCT. These finding align with the biochemical enzyme corrections observed in the patients.

Conclusion:
These data suggest biochemical benefit post-transplant, although the clinical implication of these corrections are unknown, particularly in the context of the siblings’ attenuated phenotype. Long-term follow-up is necessary to evaluate the therapeutic benefit of HCT in MSD.

Despite growing efforts Multiple Sulfatase Deficiency (MSD, MIM #272200) is still an untreatable disease with a high unmet need for a therapy. Among different approaches like gene therapy and haematopoietic stem cell transplantation identification of small molecules has been a part of the MSD research strategy for therapy development. The fastest way towards a therapy for a yet untreatable condition can be repurposing or repositioning of existing drugs, originally designed and licensed for a different disease entity. Knowledge on formulation, toxicity, dose, safety, and unwanted effects saves time and costs on lengthy processes of pharmacological, pre-clinical, and early clinical development and sometimes post marketing observations.

A high throughput drug screening on MSD patient derived cells identified tazarotene, a third generation retinoic acid derivative, to reverse disease pathology in-vitro. Tazarotene is currently licensed for topical treatment of plaque psoriasis and acne but has been investigated as an oral treatment for the same indications until 2004 in phase I-III trials with approximately 1500 participants. Tazarotene in its oral formulation has been proven and effective for the given indication. Nevertheless it has not benn licensed by the FDA because of likely severe unwanted effects inert to the pharmacological group of retinoids and the lack of trials showing benefit over already existing, licensed retinoids.

Tazarotene for its use in MSD has been chosen as a demonstrator projects by a consortium funded by the European Union, REMEDI4ALL, consisting of 24 members from academia, industry, patient organisations, and regulators. REMEDI4ALL promotes drug re-purposing for various diseases including rare diseases. With the help of REMEDI4ALL a crucial target product profile and gap analysis paved the way for a reformulation, evaluation and production of oral tazarotene for its use in MSD patients, collaboration with pharma industry for access on existing toxicity, pre-clinical, and clinical data on oral tazarotene for reference and regulatory purposes, trial design and study protocol. The efforts cumulated in a first scientific advice meeting with regulators ultimately leading to the first clinical trial in MSD patients supposed to start by the end of 2024.

Background:
Leukodystrophies are rare genetic disorders affecting myelination. Emerging therapeutics primarily target the pre-symptomatic population, but there is a knowledge gap on the impact of disease across the lifespan. To address this, we propose a standardized approach to performing retrospective natural history studies using existing medical records.

Methods:
As part of Global Leukodystrophy Initiative Clinical Trials Network (GLIA-CTN), we developed Standard Operating Procedures (SOPs) that delineated all study processes related to staff training, source documentation, and data sharing. Additionally, the SOP detailed the standardized approach to data extraction including diagnosis, clinical presentation, and medical events, such as age at gastrostomy tube placement. The key variables for extraction were selected through face validity, and common electronic case report forms (eCRF) across leukodystrophies were created to collect analyzable data. To enhance the depth of the data, clinical notes are extracted into “original” and “imputed” encounters, with imputed encounter referring to a historic event (e.g., loss of ambulation 3 months prior). Retrospective Functional Assessments are assigned by child neurologists, using a blinded dual-rater approach and any discrepancies are adjudicated by a third rater. Upon completion of extraction, data source verification is performed. Data missingness was evaluated using statistics.

Results:
To date, the records from 922 subjects have undergone this process across the GLIA-CTN database and this includes 300 subjects with Metachromatic leukodystrophy, 220 with Aicardi Goutières Syndrome, 167 with Pelizaeus-Merzbacher Disease, 25 with Multiple Sulfatase Deficiency, and 210 with Hypomyelination with Atrophy of Basal Ganglia and Cerebellum.

Conclusion:
The proposed methodology will enable us to leverage existing medical records to accrue subjects and capture clinical information, specifically pre-symptomatic data, on a large cohort of subjects in a shorter duration. This robust data collection will enable— (i) greater understanding of clinical course across leukodystrophies, and (ii) robust, regulatory-standard data applicable as historic controls in clinical trials.