The 5th International Conference on Basic and Therapeutic Aspects of Botulinum and Tetanus Neurotoxins. Workshop review: assays and detection

The development of diagnostic tests for the botulinum neurotoxins is complicated by their extremely high potencies and the considerable diversity observed within the neurotoxin family. Current approaches for the detection of the toxins and the organism include amplified immunoassays and PCR techniques. Assays which exploit the biological activities within the botulinum toxins are also in development. These are based on both antibody and mass spectrometric techniques which measure the endopeptidase activities of the neurotoxins. This overview of the Assays and Detection Workshop of the 5th International Conference of on Basic and Therapeutic Aspects of Botulinum and Tetanus Neurotoxins discusses recent progress in the development of these assay systems and the issues that need to be overcome prior to their implementation.

Quantitative Muscle Analysis in FSHD Using Whole-Body Fat-Referenced MRI: Composite Scores for Longitudinal and Cross-Sectional Analysis

BACKGROUND AND OBJECTIVES

Facioscapulohumeral muscular dystrophy (FSHD) is a rare, debilitating disease characterized by progressive muscle weakness. MRI is a sensitive assessment of disease severity and progression. We developed a quantitative whole-body (WB) musculoskeletal MRI (WB-MSK-MRI) protocol analyzing muscles in their entirety. This study aimed to assess WB-MSK-MRI as a potential imaging biomarker providing reliable measurements of muscle health that capture disease heterogeneity and clinically meaningful composite assessments correlating with severity and more responsive to change in clinical trials.

METHODS

Participants 18 to 65 years, genetically confirmed FSHD1, clinical severity 2 to 4 (Ricci's scale, range 0-5), and ≥1 short tau inversion recovery (STIR)-positive lower extremity muscle eligible for needle biopsy enrolled at 6 sites; imaged twice 4 - 12 weeks apart. Volumetric analysis of muscle fat infiltration (MFI), muscle fat fraction (MFF), and lean muscle volume (LMV) in 18 (36 total) muscles from bilateral shoulder, proximal arm, trunk, and legs was performed after automated atlas-based segmentation followed by manual verification. A WB composite score, including muscles at highest risk for progression, and functional cross-sectional composites for correlation with relevant functional outcomes including timed up and go (TUG), FSHD-TUG, and reachable workspace (RWS) were developed.

RESULTS

Seventeen participants;16 follow-up MRIs performed at 52 days (range 36 to 85). Functional cross-sectional composites (MFF and MFI) showed moderate to strong correlations: TUG (rho=0.71, rho=0.83), FSHD-TUG (rho=0.73, rho=0.73), and RWS (left arm: rho=-0.71, rho=-0.53; right arm: rho=-0.61, rho=-0.65). WB composite variability:LMV_tot, coefficient of variation (CV) 1.9% and 3.4%; MFF_tot, within-subject standard deviation (S_w) 0.5% and 1.5%; MFI_tot, (S_w), 0.3% and 0.4% for normal and intermediate muscles respectively. CV and S_w were higher in intermediate (MFI≥0.10; MFF<0.50) than in normal (MFI<0.10, MFF<0.50) muscles.

DISCUSSION

We developed a WB-MSK-MRI protocol and composite measures that capture disease heterogeneity and assess muscle involvement as it correlates with FSHD-relevant clinical endpoints. Functional composites robustly correlate with functional assessments. Stability of the WB composite shows it could be an assessment of change in therapeutic clinical trials.

CLASSIFICATION OF EVIDENCE

This study provides Class II evidence that quantitative WB-MSK-MRI findings associate with FSHD1 severity measured using established functional assessments.

Safety and efficacy of losmapimod in facioscapulohumeral muscular dystrophy (ReDUX4): a randomised, double-blind, placebo-controlled phase 2b trial

BACKGROUND

Facioscapulohumeral muscular dystrophy is a hereditary progressive myopathy caused by aberrant expression of the transcription factor DUX4 in skeletal muscle. No approved disease-modifying treatments are available for this disorder. We aimed to assess the safety and efficacy of losmapimod (a small molecule that inhibits p38α MAPK, a regulator of DUX4 expression, and p38β MAPK) for the treatment of facioscapulohumeral muscular dystrophy.

METHODS

We did a randomised, double-blind, placebo-controlled phase 2b trial at 17 neurology centres in Canada, France, Spain, and the USA. We included adults aged 18-65 years with type 1 facioscapulohumeral muscular dystrophy (ie, with loss of repression of DUX4 expression, as ascertained by genotyping), a Ricci clinical severity score of 2-4, and at least one skeletal muscle judged using MRI to be suitable for biopsy. Participants were randomly allocated (1:1) to either oral losmapimod (15 mg twice a day) or matching placebo for 48 weeks, via an interactive response technology system. The investigator, study staff, participants, sponsor, primary outcome assessors, and study monitor were masked to the treatment allocation until study closure. The primary endpoint was change from baseline to either week 16 or 36 in DUX4-driven gene expression in skeletal muscle biopsy samples, as measured by quantitative RT-PCR. The primary efficacy analysis was done in all participants who were randomly assigned and who had available data for assessment, according to the modified intention-to-treat principle. Safety and tolerability were assessed as secondary endpoints. This study is registered at ClinicalTrials.gov, number NCT04003974. The phase 2b trial is complete; an open-label extension is ongoing.

FINDINGS

Between Aug 27, 2019, and Feb 27, 2020, 80 people were enrolled. 40 were randomly allocated to losmapimod and 40 to placebo. 54 (68%) participants were male and 26 (33%) were female, 70 (88%) were White, and mean age was 45·7 (SD 12·5) years. Least squares mean changes from baseline in DUX4-driven gene expression did not differ significantly between the losmapimod (0·83 [SE 0·61]) and placebo (0·40 [0·65]) groups (difference 0·43 [SE 0·56; 95% CI -1·04 to 1·89]; p=0·56). Losmapimod was well tolerated. 29 treatment-emergent adverse events (nine drug-related) were reported in the losmapimod group compared with 23 (two drug-related) in the placebo group. Two participants in the losmapimod group had serious adverse events that were deemed unrelated to losmapimod by the investigators (alcohol poisoning and suicide attempt; postoperative wound infection) compared with none in the placebo group. No treatment discontinuations due to adverse events occurred and no participants died during the study.

INTERPRETATION

Although losmapimod did not significantly change DUX4-driven gene expression, it was associated with potential improvements in prespecified structural outcomes (muscle fat infiltration), functional outcomes (reachable workspace, a measure of shoulder girdle function), and patient-reported global impression of change compared with placebo. These findings have informed the design and choice of efficacy endpoints for a phase 3 study of losmapimod in adults with facioscapulohumeral muscular dystrophy.

FUNDING

Fulcrum Therapeutics.

An open-label pilot study of losmapimod to evaluate the safety, tolerability, and changes in biomarker and clinical outcome assessments in participants with facioscapulohumeral muscular dystrophy type 1

INTRODUCTION

Facioscapulohumeral muscular dystrophy (FSHD) is a genetic disease caused by aberrant DUX4 expression, leading to progressive muscle weakness. No effective pharmaceutical treatment is available. Losmapimod, a small molecule selective inhibitor of p38 α/β MAPK, showed promising results in a phase 1 trial for the treatment of FSHD, prompting additional studies. We report the findings of an open-label phase 2 trial (NCT04004000) investigating the safety, tolerability, pharmacokinetics, pharmacodynamics, and exploratory efficacy of losmapimod in participants with FSHD1.

METHODS

This study was conducted at a single site in the Netherlands from August 2019 to March 2021, with an optional, ongoing open-label extension. Participants aged 18 to 65 years with FSHD1 took 15 mg of losmapimod twice daily for 52 weeks. Primary endpoints were measures of losmapimod safety and tolerability. Secondary endpoints were assessments of losmapimod pharmacokinetics and pharmacodynamics.

RESULTS

Fourteen participants were enrolled. No deaths, serious treatment-emergent adverse events (TEAEs), or discontinuations due to TEAEs were reported. Losmapimod achieved blood concentrations and target engagements that were previously associated with decreased DUX4 expression in vitro. Clinical outcome measures showed a trend toward stabilization or improvement.

CONCLUSIONS

Losmapimod was well tolerated and may be a promising new treatment for FSHD; a larger phase 3 study is ongoing.

Oral ribose supplementation in dystroglycanopathy: A single case study

Three forms of muscular dystrophy-dystroglycanopathies are linked to the ribitol pathway. These include mutations in the isoprenoid synthase domain-containing protein (ISPD), fukutin-related protein (FKRP), and fukutin (FKTN) genes. The aforementioned enzymes are required for generation of the ribitol phosphate linkage in the O-glycan of alpha-dystroglycan. Mild cases of dystroglycanopathy present with slowly progressive muscle weakness, while in severe cases the eyes and brain are also involved. Previous research showed that ribose increased the intracellular concentrations of cytidine diphosphate-ribitol (CDP-ribitol) and had a therapeutic effect. Here, we report the safety and effects of oral ribose supplementation during 6 months in a patient with limb girdle muscular dystrophy type 2I (LGMD2I) due to a homozygous FKRP mutation. Ribose was well tolerated in doses of 9 g or 18 g/day. Supplementation with 18 g of ribose resulted in a decrease of creatine kinase levels of 70%. Moreover, metabolomics showed a significant increase in CDP-ribitol levels with 18 g of ribose supplementation (p < 0.001). Although objective improvement in clinical and patient-reported outcome measures was not observed, the patient reported subjective improvement of muscle strength, fatigue, and pain. This case study indicates that ribose supplementation in patients with dystroglycanopathy is safe and highlights the importance for future studies regarding its potential effects.

Assessment of the burden of outpatient clinic and MRI-guided needle muscle biopsies as reported by patients with facioscapulohumeral muscular dystrophy

Muscle biopsies are used in clinical trials to measure target engagement of the investigational product. With many upcoming therapies for patients with facioscapulohumeral dystrophy (FSHD), the frequency of biopsies in FSHD patients is expected to increase. Muscle biopsies were performed either in the outpatient clinic using a Bergström needle (BN-biopsy) or in a Magnetic Resonance Imaging machine (MRI-biopsy). This study assessed the FSHD patients' experience of biopsies using a customized questionnaire. The questionnaire was sent to all FSHD patients who had undergone a needle muscle biopsy for research purposes, inquiring about biopsy characteristics and burden, and willingness to undergo a subsequent biopsy. Forty-nine of 56 invited patients (88%) completed the questionnaire, reporting on 91 biopsies. The median pain score (scale 0-10) during the procedure was 5 [2-8], reducing to 3 [1-5] and 2 [1-3] after one and 24 h, respectively. Twelve biopsies (13.2%) resulted in complications, eleven resolved within 30 days. BN-biopsies were less painful compared to MRI-biopsies (median NRS: 4 [2-6] vs. 7 [3-9], p = 0.001). The burden of needle muscle biopsies in a research setting is considerate and should not be underestimated. MRI-biopsies have a higher burden compared to BN-biopsies.

Living with facioscapulohumeral muscular dystrophy during the first two COVID-19 outbreaks: a repeated patient survey in the Netherlands

BACKGROUND

Patients with facioscapulohumeral dystrophy (FSHD) suffer from slowly progressive muscle weakness. Approximately 20% of FSHD patients end up wheelchair-dependent. FSHD patients benefit from physical activity to maintain their muscle strength as much as possible. The impact of the COVID-19 pandemic on the health of FSHD patients was unknown.

OBJECTIVE

This study assessed changes in daily care received, perceived psychosocial stress, and worsening of FSHD complaints in 2020. Furthermore, we compared COVID-19 infection incidence and severity of symptoms between FSHD patients and non-FSHD housemates.

METHODS

Three online survey rounds were sent out to all adult participants of the Dutch FSHD registry regarding daily care received, perceived psychosocial stress, COVID-19 infection rate, and COVID-19 symptoms severity. They also included COVID-19-related questions regarding the participants' housemates, which served as control group.

RESULTS

Participation rate was 210 (61%), 186 (54%), and 205 (59%) for survey 1, 2, and 3, respectively. Care reduction was reported by 42.7%, 40%, and 28.8% of the participants in the respective surveys. Perceived psychosocial stress increased in 44%, 30%, and 40% of the participants. Compared to the 197 non-FSHD housemates, the 213 FSHD patients reported more possibly COVID-19-related symptoms (27% vs. 39%, p = 0.017) of mostly minimal severity (63%). No difference in (possible) COVID-19 infection incidence rates was found (2.0% vs. 2.8%, p = 0.527).

CONCLUSIONS

The COVID-19 pandemic negatively impacted care received and increased perceived psychosocial stress in FSHD patients. However, COVID-19 infection incidence in FSHD patients was similar to their non-FSHD housemates.

The Dutch registry for facioscapulohumeral muscular dystrophy: Cohort profile and longitudinal patient reported outcomes

Facioscapulohumeral dystrophy (FSHD) is the second most prevalent inherited muscular disorder and currently lacks a pharmaceutical treatment. The Dutch FSHD Registry was initiated in 2015 as a result of an international collaboration on trial readiness. This paper presents the cohort profile and six years of follow-up data of the registered FSHD patients. At the time of self-registration and every six months thereafter, participants were invited to complete a digital survey of patient and disease characteristics and the Dutch versions of the Checklist Individual Strength (CIS20R), the Individualised Neuromuscular Quality of Life Questionnaire (INQoL), the Beck Depression Index - Primary Care and the McGill Pain Questionnaire. From March 2015 to March 2021, 373 participants completed at least one survey. At baseline, fatigue and muscle weakness were the most frequently reported symptoms (median CIS20R sumscore 77 [IQR 60-92], median INQoL Fatigue score 58 [IQR 42-68] and median INQoL weakness score 58 [IQR 42-68]). Pain was experienced most often in the head and shoulder region (193, 52%). Nineteen of the 23 (sub)sections of questionnaires showed no significant changes over time. We conclude that the Dutch FSHD Registry was successfully set up, enabling collection of longitudinal data and facilitating recruitment in several studies.

A 5-year natural history cohort of patients with facioscapulohumeral muscular dystrophy determining disease progression and feasibility of clinical outcome assessments for clinical trials

INTRODUCTION/AIMS

The number of clinical trials in facioscapulohumeral muscular dystrophy (FSHD) is expected to increase in the near future. There is a need for clinical outcome assessments (COAs) that can capture disease progression over the relatively short time span of a clinical trial. In this study, we report the natural progression of FSHD and determine the feasibility of COAs for clinical trials.

METHODS

Genetically confirmed FSHD patients underwent various COAs at baseline and after 5 years. COAs consisted of the Motor Function Measure (MFM), manual muscle testing using the Medical Research Council score, six-minute walk test, quantitative muscle strength assessment of the quadriceps muscle, clinical severity score, and FSHD evaluation score (FES). Statistical significance and the minimal clinically important difference (MCID) were calculated and power calculations were performed.

RESULTS

One hundred fifty-four symptomatic FSHD patients were included, with a mean (SD) age of 51.4 (14.6) years old. All COAs showed a minimal, yet statistically significant progression after 5 years. MCID was reached for the MFM Domain 1, MFM total score, and FES. These three COAs showed the lowest sample size requirements for clinical trials (185, 156, and 201 participants per group, respectively, for a trial duration of 2 years).

DISCUSSION

The captured FSHD disease progression rate in 5 years was generally minimal. The COAs in this study are not feasible for clinical trials with a duration of 2 years. Extended trial durations or novel outcome assessments might be necessary to improve trial feasibility in FSHD.

The participants' perspective on facioscapulohumeral muscular dystrophy trials in The Netherlands - A qualitative study

BACKGROUND

Facioscapulohumeral muscular dystrophy (FSHD) is a hereditary muscle disease without an available cure. The first trials with potentially disease-modifying therapies have started, including a phase ll open-label study and a phase lll double-blind randomized placebo-controlled trial assessing the safety and efficacy of losmapimod. Having a more in-depth understanding of the patient's experience of these trials will further enhance the design and recruitment of future trials.

OBJECTIVE

To explore the motivation, expectations, concerns, and experiences of FSHD patients in the first clinical trials in the Netherlands resulting in recommendations for future trials.

METHODS

Semi-structured interviews with participants of phase II and III losmapimod trials were conducted. The interview guide was based on previous conducted literature reviews and consultation of a patient representative. Participants were selected through convenience sampling. Four main themes were discussed: motivation for participation, expectations regarding study drug and trial visits, trial participation experience, and recommendations for future trials. The interviews were transcribed, anonymized, and analyzed using Atlas.ti version 23.1.1 using a deductive approach.

RESULTS

Thirteen participants were interviewed; six phase II participants and seven phase III participants. The primary motivations to participate concerned altruistic motives, contribute to science or improve their own health status. The participants had realistic expectations of the effect of the study drug before trial participation. Overall, participants were positive about their trial participation. Specifically, the personal and transparent communication within a trusting and dedicated trial team was appreciated. The phase III participants reported a higher than expected psychological burden on participating in a placebo-controlled trial. Recommendations consisted of more frequent updates on the overall progress and results of the trials.

CONCLUSIONS

This study presents the participants' perspective on FSHD trials, providing important key findings for future clinical trial design, study site practices and patient education.