Cost of illness in Charcot-Marie-Tooth neuropathy: Results from Germany

Boosting BDNF in muscle rescues impaired axonal transport in a mouse model of DI-CMTC peripheral neuropathy

Charcot-Marie-Tooth disease (CMT) is a genetic peripheral neuropathy caused by mutations in many functionally diverse genes. The aminoacyl-tRNA synthetase (ARS) enzymes, which transfer amino acids to partner tRNAs for protein synthesis, represent the largest protein family genetically linked to CMT aetiology, suggesting pathomechanistic commonalities. Dominant intermediate CMT type C (DI-CMTC) is caused by YARS1 mutations driving a toxic gain-of-function in the encoded tyrosyl-tRNA synthetase (TyrRS), which is mediated by exposure of consensus neomorphic surfaces through conformational changes of the mutant protein. In this study, we first showed that human DI-CMTC-causing TyrRSE196K mis-interacts with the extracellular domain of the BDNF receptor TrkB, an aberrant association we have previously characterised for several mutant glycyl-tRNA synthetases linked to CMT type 2D (CMT2D). We then performed temporal neuromuscular assessments of YarsE196K mice modelling DI-CMT. We determined that YarsE196K homozygotes display a selective, age-dependent impairment in in vivo axonal transport of neurotrophin-containing signalling endosomes, phenocopying CMT2D mice. This impairment is replicated by injection of recombinant TyrRSE196K, but not TyrRSWT, into muscles of wild-type mice. Augmenting BDNF in DI-CMTC muscles, through injection of recombinant protein or muscle-specific gene therapy, resulted in complete axonal transport correction. Therefore, this work identifies a non-cell autonomous pathomechanism common to ARS-related neuropathies, and highlights the potential of boosting BDNF levels in muscles as a therapeutic strategy.

Are We Capturing the Socioeconomic Burden of Rare Genetic Disease? A Scoping Review of Economic Evaluations and Cost-of-Illness Studies

BACKGROUND AND OBJECTIVES

Rare diseases have a significant impact on patients, families, the health system, and society. Measuring the socioeconomic burden is crucial to valuing interventions for rare diseases. Healthcare system costs are significant, but so are costs to other government sectors, patients, families, and society. To understand the breadth of costs captured in rare disease studies, we examined the cost categories and elements of socioeconomic burden captured in published studies.

METHODS

A scoping review was conducted using five electronic databases to identify English language economic evaluations and cost-of-illness studies of interventions for rare diseases (2011-21). We mapped costs using a previously developed evidence-informed framework of socioeconomic burden costs for rare disease.

RESULTS

Of 4890 studies identified, 48 economic evaluations and 22 cost-of-illness studies were included. While 18/22 cost-of-illness studies utilized a societal perspective, only 7/48 economic evaluations incorporated societal costs. Most reported cost categories related to medical costs, with medication and hospitalizations being the most common elements for both study designs. Costs borne by patients, families, and society were reported less among economic evaluations than cost-of-illness studies. These included: productivity (10% vs 77%), travel/accommodation (6% vs 68%), government benefits (4% vs 18%), and family impacts (0% vs 50%).

CONCLUSIONS

Contrary to cost-of-illness analyses, most of the included economic evaluations did not account for the hidden burden of rare diseases, that is, costs borne by patients, families, and societies. Including these types of costs in future studies would provide a more comprehensive picture of the burden of disease, providing empirical data to inform how we value and make decisions regarding rare disease interventions, health policy, and resource allocation.

Cost of illness in inclusion body myositis: results from a cross-sectional study in Germany

BACKGROUND

Inclusion body myositis (IBM) is the most frequent type of myositis in elder patients with a slow chronic progression and refractory to treatment. Previous cost of illness (COI) studies in IBM used claims data to estimate direct costs in the US. No evidence exists globally on both direct and indirect costs in IBM from a societal perspective. We conducted a survey in patients registered in the German IBM patient registry. Self-developed items were used to assess the utilized healthcare resources and estimate the cost. The German Self-Administered Comorbidity Questionnaire (SCQ-D), the sIBM Physical Functioning Assessment (sIFA) and patient-reported measures for satisfaction and improvements in healthcare were applied for an explorative analysis.

RESULTS

In total, 82 patients completed the survey. We estimated the mean total annual per capita COI of US$102,682 (95% CI US$82,763-US$123,090) in 2021. 92.7% of the total COI were direct costs. Medical costs were similar to nonmedical costs, with substantial costs for pharmacotherapy and informal care. Depending on the prevalence estimate, the total national COI per year were US$42.7 million-US$213.7 million. Significant differences in total COI were identified for the degree of disability, marital and employment status (p < 0.05).

CONCLUSIONS

We identified remarkable and heterogenous cost in IBM. As informal care costs represented the most relevant cost driver, caregiver burden is a major factor in the patient journey. For the first time, comprehensive economic potentials were identified as a basis to improve the actual care situations and prioritizing future activities for research, pharmaceutical and digital product development as well as health politics.

Economic evaluation of Motor Neuron Diseases: a nationwide cross-sectional analysis in Germany

BACKGROUND AND OBJECTIVES

Motor Neuron Diseases (MND) are rare diseases but have a high impact on affected individuals and society. This study aims to perform an economic evaluation of MND in Germany.

METHODS

Primary patient-reported data were collected including individual impairment, the use of medical and non-medical resources, and self-rated Health-Related Quality of Life (HRQoL). Annual socio-economic costs per year as well as Quality-Adjusted Life Years (QALYs) were calculated.

RESULTS

404 patients with a diagnosis of Amyotrophic Lateral Sclerosis (ALS), Spinal Muscular Atrophy (SMA) or Hereditary Spastic Paraplegia (HSP) were enrolled. Total annual costs per patient were estimated at 83,060€ in ALS, 206,856€ in SMA and 27,074€ in HSP. The main cost drivers were informal care (all MND) and disease-modifying treatments (SMA). Self-reported HRQoL was best in patients with HSP (mean EuroQoL Five Dimension Five Level (EQ-5D-5L) index value 0.67) and lowest in SMA patients (mean EQ-5D-5L index value 0.39). QALYs for patients with ALS were estimated to be 1.89 QALYs, 23.08 for patients with HSP and 14.97 for patients with SMA, respectively. Cost-utilities were estimated as follows: 138,960€/QALY for ALS, 525,033€/QALY for SMA, and 49,573€/QALY for HSP. The main predictors of the high cost of illness and low HRQoL were disease progression and loss of individual autonomy.

CONCLUSION

As loss of individual autonomy was the main cost predictor, therapeutic and supportive measures to maintain this autonomy may contribute to reducing high personal burden and also long-term costs, e.g., care dependency and absenteeism from work.

A Retrospective Bayesian Design of Experiment (B-DOE) on Drug Reposition Candidates for Treatment of Charcot-Marie-Tooth Neuropathy

Bayesian design of experiment (B-DOE) uses the principle of Bayesian Epistemology that explain the evidence as a logical-probalistic coherence on the basis of rational degrees of belief (or degrees of confidence). The researcher has design the (B-DOE) using Multilevel Hierarchy (MH), and data that may be obtained at the weak to moderate evidence level (literature, biological. Mechanism, computational and retrospective) may be helpful to identify bioactive compounds for treating (CMT) and provide the knowledge on pathogenesis, prognostic of the disease and collective mechanism of drug of action. The investigators will classify the evidence on the basis of hierarchy as moderate and weak, which will ultimately help to study new promising bioactive compounds potentially able to solve some of the issues related to CMT.

Employment status of patients with Charcot-Marie-Tooth type 1A

Previous studies showed that being unemployed is associated with lower quality of life in patients with Charcot-Marie-Tooth type 1A (CMT1A). The aim of this study was to assess the differences between CMT1A patients capable of working and CMT1A patients incapable of working due to CMT1A. Forty-four patients with genetically confirmed CMT1A were included. Medical Research Council (MRC) Sum Score, Charcot-Marie-Tooth Neuropathy Score (CMTNS), CMT Examination Score (CMTES), Overall Neuropathy Limitations Scale (ONLS), Beck Depression Inventory (BDI), Krupp's Fatigue Severity Scale (FSS), and Falls Efficacy Score (FES) were used. Whole cohort was divided into two groups: 1. CMT1A patients capable of working (employed and unemployed not due to CMT) and 2. CMT1A patients incapable of working due to CMT1A (unemployed due to CMT and retired due to CMT). At time of testing, 38.6% patients were employed, 13.6% were unemployed due to CMT, 6.8% were unemployed but not due to CMT, and 40.9% were retired early due to disability caused by CMT. Patients retired due to CMT1A at the age of 43 ± 10 years. ONLS total score and physical work appeared as significant independent predictors of being incapable of working due to CMT1A. Patients incapable of working were almost four times more likely to have fatigue (OR = 3.7, 95% CI 1.0-13.1, p < 0.05) and 11 times more likely to have fear of falling (OR = 11.0, 95% CI 2.0-59.7, p < 0.01). Patients with more severe functional disability and physical type of job were most likely incapable of working due to CMT1A. Incapability of working was associated with fatigue and fear of falling.

Prevalence and incidence of neuromuscular conditions in the UK between 2000 and 2019: A retrospective study using primary care data

BACKGROUND

In the UK, large-scale electronic primary care datasets can provide up-to-date, accurate epidemiological information on rarer diseases, where specialist diagnoses from hospital discharges and clinic letters are generally well recorded and electronically searchable. Current estimates of the number of people living with neuromuscular disease (NMD) have largely been based on secondary care data sources and lacked direct denominators.

OBJECTIVE

To estimate trends in the recording of neuromuscular disease in UK primary care between 2000-2019.

METHODS

The Clinical Practice Research Datalink (CPRD) database was searched electronically to estimate incidence and prevalence rates (per 100,000) for a range of NMDs in each year. To compare trends over time, rates were age standardised to the most recent CPRD population (2019).

RESULTS

Approximately 13 million patients were actively registered in each year. By 2019, 28,230 active patients had ever received a NMD diagnosis (223.6), which was higher among males (239.0) than females (208.3). The most common classifications were Guillain-Barre syndrome (40.1), myasthenia gravis (33.7), muscular dystrophy (29.5), Charcot-Marie-Tooth (29.5) and inflammatory myopathies (25.0). Since 2000, overall prevalence grew by 63%, with the largest increases seen at older ages (≥65-years). However, overall incidence remained constant, though myasthenia gravis incidence has risen steadily since 2008, while new cases of muscular dystrophy fell over the same period.

CONCLUSIONS

Lifetime recording of many NMDs on primary care records exceed current estimates of people living with these conditions; these are important data for health service and care planning. Temporal trends suggest this number is steadily increasing, and while this may partially be due to better recording, it cannot be simply explained by new cases, as incidence remained constant. The increase in prevalence among older ages suggests increases in life expectancy among those living with NMDs may have occurred.

Charcot-Marie-tooth disease causing mutation (p.R158H) in pyruvate dehydrogenase kinase 3 (PDK3) affects synaptic transmission, ATP production and causes neurodegeneration in a CMTX6 C. elegans model

Charcot–Marie-Tooth (CMT) is a commonly inherited, non-fatal neurodegenerative disorder that affects sensory and motor neurons in patients. More than 90 genes are known to cause axonal and demyelinating forms of CMT. The p.R158H mutation in the pyruvate dehydrogenase kinase 3 (PDK3) gene is the genetic cause for an X linked form of axonal CMT (CMTX6). In vitro studies using patient fibroblasts and iPSC-derived motor neurons have shown that this mutation causes deficits in energy metabolism and mitochondrial function. Animal models that recapitulate pathogenic in vivo events in patients are crucial for investigating mechanisms of axonal degeneration and developing therapies for CMT. We have developed a C. elegans model of CMTX6 by knocking-in the p.R158H mutation in pdhk-2, the ortholog of PDK3. In addition, we have developed animal models overexpressing the wild type and mutant form of human PDK3 specifically in the GABAergic motor neurons of C. elegans. CMTX6 mutants generated in this study exhibit synaptic transmission deficits, locomotion defects and show signs of progressive neurodegeneration. Furthermore, the CMTX6 in vivo models display energy deficits that recapitulate the phenotype observed in patient fibroblasts and iPSC-derived motor neurons. Our CMTX6 animals represent the first in vivo model for this form of CMT and have provided novel insights into the cellular function and metabolic pathways perturbed by the p.R158H mutation, all the while closely replicating the clinical presentation observed in CMTX6 patients.

Updated review of therapeutic strategies for Charcot-Marie-Tooth disease and related neuropathies

Introduction: Charcot-Marie-Tooth disease (CMT) and related neuropathies represent the most prevalent inherited neuromuscular disorders. Nonetheless, there is still no pharmacological treatment available for any CMT type. However, the landscape is rapidly evolving and several novel approaches are providing encouraging results in preclinical studies and leading to clinical trials.Areas covered: The authors review the most promising therapies under study and the ongoing/planned clinical trials. Several approaches to address PMP22 overexpression underlying CMT1A, the most frequent subtype, are being tested. Gene silencing, targeting PMP22, and gene therapy, to introduce specific genes or to substitute or modulate defective ones, are being experimented in animal models. Compounds acting on ER stress, unfolded protein response, neuregulin pathways, phosphoinositides metabolism, axonal transport and degeneration, inflammation, polyol pathway, deoxysphingolipid metabolism, purine nucleotide pool are potential therapeutic candidates for different forms of CMT and related neuropathies.Expert opinion: We are getting closer to find effective therapies for CMT, but are far behind the exciting examples of other genetic neuromuscular disorders. The authors analyze the possible reasons for this gap and the way to fill it. Preclinical and clinical research is ongoing with coordinated efforts and they are confident that in the next few years we will see the first effective treatments.

The socioeconomic burden of facioscapulohumeral muscular dystrophy

BACKGROUND

Promising genetic therapies are being investigated in facioscapulohumeral muscular dystrophy (FSHD). However, the current cost of illness is largely unknown.

OBJECTIVE

This study aimed at determining the socioeconomic burden of FSHD.

METHODS

Adult patients with FSHD from the Dutch FSHD registry were invited to complete a questionnaire on medical consumption, work productivity and health-related quality of life (HR-QoL) using the EQ-5D-5L. Associated costs were calculated from a societal perspective. A generalized linear model was fitted to the data to investigate whether level of mobility was related to annual costs of illness.

RESULTS

172 patients with FSHD completed the questionnaire (response rate 65%). The per-patient annual direct medical costs of FSHD were estimated at €12,077, direct non-medical costs at €9179 and indirect costs at €5066, adding up to a total cost of illness of €26,322 per patient per year. The direct costs of illness were €21,256, approximately five times higher than the mean per-capita health expenditures in the Netherlands. Major cost-driving factors were formal home care and informal care. A decreased level of mobility was associated with higher direct costs of illness. HR-QoL was significantly reduced in patients with FSHD with a median health utility value of 0.63.

CONCLUSIONS

We show that FSHD is associated with substantial direct and indirect socioeconomic costs as well as a reduction in HR-QoL. These findings are important for health care decision makers and aids in allocation of research funds and evaluation of the cost-effectiveness of novel therapies.

Health-related Quality of Life and Satisfaction with German Health Care Services in Patients with Charcot-Marie-Tooth Neuropathy

BackgroundCharcot-Marie-Tooth (CMT) neuropathies entail a large group of diseases with different gene mutation patterns, which produce heterogeneous phenotypes. Although health-related quality of life (HRQOL) is significantly impaired, a comprehensive assessment of HRQOL in CMT patients in Germany considering phenotypical heterogeneity represented a research gap.ObjectiveThe aim was to assess HRQOL and the satisfaction with health care in CMT patients in Germany.MethodsCMT patients >  15 years with a genetically confirmed CMT subtype were recruited through a national CMT patient registry. HRQOL was assessed using the EQ-5D-5L questionnaire. Furthermore, subjective impairments in daily or work activities and satisfaction with health care were assessed using 4-point scales.ResultsHRQOL in CMT patients (n = 385) was impaired compared to the German population. Most patients reported problems in the dimension mobility (89.6%), pain/discomfort (89.4%) and usual activities (81.0%). Except for patients with hereditary neuropathy with liability to pressure palsy (HNPP), we found no differences in HRQOL between the CMT subtypes. 72.0%of CMT patients were satisfied with available health care services. However, patients reported to expect more CMT-specific knowledge and support as well as easier prescription and cost coverage procedures from health professionals and insurances.ConclusionsThe patient-reported outcomes in the assessed CMT cohort elucidate the need for more specific health care services that also address the heterogeneous phenotypes. Although the assessment has been limited to the German health services setting, insights may be applicable to CMT-specific care in other national settings.

Treating PMP22 gene duplication-related Charcot-Marie-Tooth disease: the past, the present and the future

Charcot-Marie-Tooth (CMT) disease is the most frequent inherited neuropathy, affecting 1/1500 to 1/10000. CMT1A represents 60%-70% of all CMT and is caused by a duplication on chromosome 17p11.2 leading to an overexpression of the Peripheral Myelin Protein 22 (PMP22). PMP22 gene is under tight regulation and small changes in its expression influences myelination and affect motor and sensory functions. To date, CMT1A treatment is symptomatic and classic pharmacological options have been disappointing. Here, we review the past, present, and future treatment options for CMT1A, with a special emphasis on the highly promising potential of PMP22-targeted small interfering RNA and antisense oligonucleotides.

Costs of illness in amyotrophic lateral sclerosis (ALS): a cross-sectional survey in Germany

Background

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disorder. Consequently, patients undergo a multidisciplinary treatment that often requires intensive use of medical resources. This study provides an estimate on the cost of illness depending on the clinical severity while also analysing the patients’ health-related quality of life.

Methods

Primary data from patients and caregivers was collected through a standardised questionnaire. Direct medical, direct non-medical and indirect costs were calculated using the latest German health economic guidelines. Patients were divided into five groups according to the King’s staging system. Health-related quality of life was assessed using EuroQoL Group EQ-5D-5L™ questionnaire. Influencing factors on both total cost and quality of life were examined.

Results

The mean annual total cost of illness was 78,256€ per patient while the lifetime cost per patient was estimated at 246,184€. The prevalence based total burden yearly therefore was 519,776,352€ in Germany. Nearly half of the costs were attributable to informal care. With increase of the clinical severity stage, costs rose and quality of life decreased. The score of the revised Amyotrophic Laterals Sclerosis Functional Rating Scale was identified as one major influencing factor on total costs, while subjective impairment in daily activities and classification into a care level as opposed to having no care level influenced patients’ quality of life.

Conclusion

It is essential to understand the socioeconomic burden of a disease. These data can be used to improve patient care standards and quality of life while also serving as a basis for cost-benefit analyses during the approval process of new treatments.