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 p38ß 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.

Relationship Between Hand Function and Handheld Ultrasound Imaging in Inclusion Body Myositis.

OBJECTIVE: Ultrasound studies in inclusion body myositis (IBM) have reported a characteristic pattern of increased echointensity in the flexor digitorum profundus (FDP) with relative sparing of the flexor carpi ulnaris (FCU). We examined the relationship between echointensity of the FDP and FCU muscles and hand strength or patient-reported outcomes (PROs). METHODS: A total of 15 patients with IBM were recruited. Ultrasound images of the FDP and FCU muscles were obtained by a point-of-care ultrasound and graded using the modified Heckmatt score. Hand grip and neutral pinch strength were measured by dynamometry. PROs were assessed by the IBM Upper Extremity Function Scale. RESULTS: FDP and/or FCU modified Heckmatt score showed a significant relationship with grip, neutral pinch strength, and PROs. CONCLUSIONS: Point-of-care ultrasound examination of the forearm may serve as an extension of the neuromuscular examination. The semi-qualitative echointensity rating based on modified Heckmatt score seems to correlate well with the objective strength measurement and PROs.

Regional and bilateral MRI and gene signatures in facioscapulohumeral dystrophy: implications for clinical trial design and mechanisms of disease progression.

Identifying the aberrant expression of DUX4 in skeletal muscle as the cause of facioscapulohumeral dystrophy (FSHD) has led to rational therapeutic development and clinical trials. Several studies support the use of MRI characteristics and the expression of DUX4-regulated genes in muscle biopsies as biomarkers of FSHD disease activity and progression. We performed lower-extremity MRI and muscle biopsies in the mid-portion of the tibialis anterior (TA) muscles bilaterally in FSHD subjects and validated our prior reports of the strong association between MRI characteristics and expression of genes regulated by DUX4 and other gene categories associated with FSHD disease activity. We further show that measurements of normalized fat content in the entire TA muscle strongly predict molecular signatures in the mid-portion of the TA, indicating that regional biopsies can accurately measure progression in the whole muscle and providing a strong basis for inclusion of MRI and molecular biomarkers in clinical trial design. An unanticipated finding was the strong correlations of molecular signatures in the bilateral comparisons, including markers of B-cells and other immune cell populations, suggesting that a systemic immune cell infiltration of skeletal muscle might have a role in disease progression.

Lean tissue mass measurements by dual-energy X-ray absorptiometry and associations with strength and functional outcome measures in facioscapulohumeral muscular dystrophy.

Facioscapulohumeral muscular dystrophy (FSHD) is a slowly progressive disease of skeletal muscle. Dual energy X-ray absorptiometry (DEXA) is a widely available, cost-effective and sensitive technique for measuring whole body and regional lean tissue mass and has been used in prior clinical trials in neuromuscular diseases. The Clinical Trial Readiness to Solve Barriers to Drug Development in FSHD (ReSolve) study is a prospective, longitudinal, observational multisite study. We obtained concurrent DEXA scans and functional outcome measurements in 185 patients with FSHD at the baseline visit. We determined the associations between lean tissue mass in the upper and lower extremities and corresponding clinical outcome measures. There were moderate correlations between upper and lower extremity lean tissue mass and their corresponding strengths and function. Lean tissue mass obtained by DEXA scan may be useful as a biomarker in future clinical trials in FSHD.

Validation of the association between MRI and gene signatures in facioscapulohumeral dystrophy muscle: implications for clinical trial design.

Identifying the aberrant expression of DUX4 in skeletal muscle as the cause of facioscapulohumeral dystrophy (FSHD) has led to rational therapeutic development and clinical trials. Several studies support the use of MRI characteristics and the expression of DUX4-regulated genes in muscle biopsies as biomarkers of FSHD disease activity and progression, but reproducibility across studies needs further validation. We performed lower-extremity MRI and muscle biopsies in the mid-portion of the tibialis anterior (TA) muscles bilaterally in FSHD subjects and validated our prior reports of the strong association between MRI characteristics and expression of genes regulated by DUX4 and other gene categories associated with FSHD disease activity. We further show that measurements of normalized fat content in the entire TA muscle strongly predict molecular signatures in the mid-portion of the TA. Together with moderate-to-strong correlations of gene signatures and MRI characteristics between the TA muscles bilaterally, these results suggest a whole muscle model of disease progression and provide a strong basis for inclusion of MRI and molecular biomarkers in clinical trial design.

Correlations of disease severity outcome measures in inclusion body myositis.

This study aimed to evaluate the correlation between various outcome measures used to assess disease severity and progression in inclusion body myositis (IBM) clinical trials. A cross-sectional study, involving 51 IBM patients meeting the European Neuromuscular Center (ENMC) 2011 criteria for clinically defined or probable IBM, was completed at the University of California, Irvine. Clinical details, demographic data, and functional data including timed get up (TGU), manual muscle testing, hand grip, pinch dynamometry, as well as IBM functional rating scale (IBMFRS), modified Rankin score, forced vital capacity (FVC), and modified ocular bulbar facial respiratory scale (mOBFRS) were collected on all patients. Descriptive statistics and Pearson's r correlation were performed to analyze the data. Age of the patient did not correlate with any of the outcome measures. Greater severity of IBMFRS scores correlated with longer disease duration as well as greater severity for FVC, strength outcomes, TGU, modified Rankin, and mOBFRS. Additionally, TGU strongly correlated with muscle strength measurements, modified Rankin, and mOBFRS. mOBFRS moderately correlated with IBMFRS, muscle strength, FVC, TGU and modified Rankin score. We demonstrate moderate to strong correlations among the disease severity outcome measures in this study.

Quantitative muscle analysis in facioscapulohumeral muscular dystrophy using whole-body fat-referenced MRI: Protocol development, multicenter feasibility, and repeatability.

INTRODUCTION/AIMS: Functional performance tests are the gold standard to assess disease progression and treatment effects in neuromuscular disorders. These tests can be confounded by motivation, pain, fatigue, and learning effects, increasing variability and decreasing sensitivity to disease progression, limiting efficacy assessment in clinical trials with small sample sizes. We aimed to develop and validate a quantitative and objective method to measure skeletal muscle volume and fat content based on whole-body fat-referenced magnetic resonance imaging (MRI) for use in multisite clinical trials. METHODS: Subjects aged 18 to 65 years, genetically confirmed facioscapulohumeral muscular dystrophy 1 (FSHD1), clinical severity 2 to 4 (Ricci's scale, range 0-5), were enrolled at six sites and imaged twice 4-12 weeks apart with T1-weighted two-point Dixon MRI covering the torso and upper and lower extremities. Thirty-six muscles were volumetrically segmented using semi-automatic multi-atlas-based segmentation. Muscle fat fraction (MFF), muscle fat infiltration (MFI), and lean muscle volume (LMV) were quantified for each muscle using fat-referenced quantification. RESULTS: Seventeen patients (mean age ± SD, 49.4 years ±13.02; 12 men) were enrolled. Within-patient SD ranged from 1.00% to 3.51% for MFF and 0.40% to 1.48% for MFI in individual muscles. For LMV, coefficients of variation ranged from 2.7% to 11.7%. For the composite score average of all muscles, observed SDs were 0.70% and 0.32% for MFF and MFI, respectively; composite LMV coefficient of variation was 2.0%. DISCUSSION: We developed and validated a method for measuring skeletal muscle volume and fat content for use in multisite clinical trials of neuromuscular disorders.

Longitudinal study of MRI and functional outcome measures in facioscapulohumeral muscular dystrophy.

BACKGROUND: Facioscapulohumeral muscular dystrophy (FSHD) is a patchy and slowly progressive disease of skeletal muscle. For MRI to be a useful biomarker in an FSHD clinical trial, it should reliably detect changes over relatively short time-intervals (~ 1 year). We hypothesized that fatty change over the study course would be most likely in muscles already demonstrating disease progression, and that the degree of MRI burden would be correlated with function. METHODS: We studied 36 patients with FSHD and lower-extremity weakness at baseline. Thirty-two patients returned in our 12-month longitudinal observational study. We analyzed DIXON MRI images of 16 lower-extremity muscles in each patient and compared them to quantitative strength measurement and ambulatory functional outcome measures. RESULTS: There was a small shift to higher fat fractions in the summed muscle data for each patient, however individual muscles demonstrated much larger magnitudes of change. The greatest increase in fat fraction was observed in muscles having an intermediate fat replacement at baseline, with minimally (baseline fat fraction < 0.10) or severely (> 0.70) affected muscles less likely to progress. Functional outcome measures did not demonstrate marked change over the interval; however, overall MRI disease burden was correlated with functional outcome measures. Direct comparison of the tibialis anterior (TA) fat fraction and quantitative strength measurement showed a sigmoidal relationship, with steepest drop being when the muscle gets more than ~ 20% fatty replaced. CONCLUSIONS: Assessing MRI changes in 16 lower-extremity muscles across 1 year demonstrated that those muscles having an intermediate baseline fat fraction were more likely to progress. Ambulatory functional outcome measures are generally related to overall muscle MRI burden but remain unchanged in the short term. Quantitative strength measurement of the TA showed a steep loss of strength when more fatty infiltration is present suggesting that MRI may be preferable for following incremental change or modulation with drug therapy.

Clinical utility of anti-cytosolic 5'-nucleotidase 1A antibody in idiopathic inflammatory myopathies.

OBJECTIVE: To define the clinicopathologic features and diagnostic utility associated with anti-cytosolic 5'-nucleotidase 1A (NT5C1A) antibody seropositivity in idiopathic inflammatory myopathies (IIMs). METHODS: Anti-NT5C1A antibody status was clinically tested between 2014 and 2019 in the Washington University neuromuscular clinical laboratory. Using clinicopathologic information available for 593 patients, we classified them as inclusion body myositis (IBM), dermatomyositis, antisynthetase syndrome, immune-mediated necrotizing myopathy (IMNM), nonspecific myositis, or noninflammatory muscle diseases. RESULTS: Of 593 patients, anti-NT5C1A antibody was found in 159/249 (64%) IBM, 11/53 (21%) dermatomyositis, 7/27 (26%) antisynthetase syndrome, 9/76 (12%) IMNM, 20/84 (24%) nonspecific myositis, and 6/104 (6%) noninflammatory muscle diseases patients. Among patients with IBM, anti-NT5C1A antibody seropositive patients had more cytochrome oxidase-negative fibers compared with anti-NT5C1A antibody seronegative patients. Among 14 IBM patients initially negative for anti-NT5C1A antibody, three patients (21%) converted to positive. Anti-NT5C1A antibody seropositivity did not correlate with malignancy, interstitial lung disease, response to treatments in dermatomyositis, antisynthetase syndrome, and IMNM, or survival in IIMs. INTERPRETATION: Anti-NT5C1A antibody is associated with IBM. However, the seropositivity can also be seen in non-IBM IIMs and it does not correlate with any prognostic factors or survival.

Current Therapeutic Approaches in FSHD.

Facioscapulohumeral muscular dystrophy (FSHD) is one of the most common muscular dystrophies. Over the last decade, a consensus was reached regarding the underlying cause of FSHD allowing-for the first time-a targeted approach to treatment. FSHD is the result of a toxic gain-of-function from de-repression of the DUX4 gene, a gene not normally expressed in skeletal muscle. With a clear therapeutic target, there is increasing interest in drug development for FSHD, an interest buoyed by the recent therapeutic successes in other neuromuscular diseases. Herein, we review the underlying disease mechanism, potential therapeutic approaches as well as the state of trial readiness in the planning and execution of future clinical trials in FSHD.

Adapting MRI as a clinical outcome measure for a facioscapulohumeral muscular dystrophy trial of prednisone and tacrolimus: case report.

BACKGROUND: Facioscapulohumeral muscular dystrophy (FSHD) is a patchy and slowly progressive disease of skeletal muscle. MRI short tau inversion recovery (STIR) sequences of patient muscles often show increased hyperintensity that is hypothesized to be associated with inflammation. This is supported by the presence of inflammatory changes on biopsies of STIR-positive muscles. We hypothesized that the STIR positivity would normalize with targeted immunosuppressive therapy. CASE PRESENTATION: 45-year-old male with FSHD type 1 was treated with 12 weeks of immunosuppressive therapy, tacrolimus and prednisone. Tacrolimus was treated to a goal serum trough of > 5 ng/mL and prednisone was tapered every month. Quantitative strength exam, functional outcome measures, and muscle MRI were performed at baseline, week 6, and week 12. The patient reported subjective worsening as reflected in quantitative strength exam. The MRI STIR signal was slightly increased from 0.02 to 0.03 of total muscle; while the T1 fat fraction was stable. Functional outcome measures also were stable. CONCLUSIONS: Immunosuppressive therapy in refractive autoimmune myopathy in other contexts has been shown to reverse STIR signal hyperintensity, however this treatment did not reverse STIR signal in this patient with FSHD. In fact, STIR signal slightly increased throughout the treatment period. This is the first study of using MRI STIR and T1 fat fraction to follow treatment effect in FSHD. We find that STIR might not be a dynamic marker for suppressing inflammation in FSHD.

Effects of mexiletine on hyperexcitability in sporadic amyotrophic lateral sclerosis: Preliminary findings from a small phase II randomized controlled trial.

BACKGROUND: To collect preliminary data on the effects of mexiletine on cortical and axonal hyperexcitability in sporadic amyotrophic lateral sclerosis (ALS) in a phase 2 double-blind randomized controlled trial. METHODS: Twenty ALS subjects were randomized to placebo and mexiletine 300 or 600 mg daily for 4 wk and assessed by transcranial magnetic stimulation and axonal excitability studies. The primary endpoint was change in resting motor threshold (RMT). RESULTS: RMT was unchanged with 4 wk of mexiletine (combined active therapies) as compared to placebo, which showed a significant increase (P = .039). Reductions of motor evoked potential (MEP) amplitude (P = .013) and accommodation half-time (P = .002), secondary outcome measures of cortical and axonal excitability, respectively, were also evident at 4 wk on mexiletine. CONCLUSIONS: The relative stabilization of RMT in the treated subjects was unexpected and could be attributed to unaccounted sources of error or chance. However, a possible alternative cause is neuromodulation preventing an increase. The change in MEP amplitude and accommodation half-time supports the reduction of cortical and axonal hyperexcitability with mexiletine.

Optimizing hand-function patient outcome measures for inclusion body myositis.

Inclusion body myositis is the most commonly acquired myopathy after the age of 45. The slowly progressive and heterogeneous disorder is a challenge for measuring clinical trial efficacy. One current method for measuring progression utilizes the Inclusion Body Myositis-Functional Rating Scale. We have found that the upper extremity domain scores in the Inclusion Body Myositis-Functional Rating Scale do not consistently change until there is extreme loss of grip and finger flexor strength. Therefore, we performed a cross-sectional observational study of 83 inclusion body myositis patients and 38 controls recruited at the 2019 Annual Patient Conference of The Myositis Association. We evaluated new Inclusion Body Myositis Patient-Reported Outcome measures for upper extremity function modified from the NIH Patient-Reported Outcomes Measurement Information System as well as pinch and grip strength. We found that Patient-Reported Outcome measures hand-function have a higher correlation with pinch and grip strength than the Inclusion Body Myositis-Functional Rating Scale.

Longitudinal measures of RNA expression and disease activity in FSHD muscle biopsies.

Advances in understanding the pathophysiology of facioscapulohumeral dystrophy (FSHD) have led to the discovery of candidate therapeutics, and it is important to identify markers of disease activity to inform clinical trial design. For drugs that inhibit DUX4 expression, measuring DUX4 or DUX4-target gene expression might be an interim measure of drug activity; however, only a subset of FHSD muscle biopsies shows evidence of DUX4 expression. Our prior study showed that MRI T2-STIR-positive muscles had a higher probability of showing DUX4 expression than muscles with normal MRI characteristics. In the current study, we performed a 1-year follow-up assessment of the same muscle with repeat MRI and muscle biopsy. There was little change in MRI characteristics over the 1-year period and, similar to the initial evaluation, MRI T2-STIR-postive muscles had a higher expression of DUX4-regulated genes, as well as genes associated with inflammation, extracellular matrix and cell cycle. Compared to the initial evaluation, overall the level of expression in these gene categories remained stable over the 1-year period; however, there was some variability for each individual muscle biopsied. The pooled data from both the initial and 1-year follow-up evaluations identified several FSHD subgroups based on gene expression, as well as a set of genes-composed of DUX4-target genes, inflammatory and immune genes and cell cycle control genes-that distinguished all of the FSHD samples from the controls. These candidate markers of disease activity need to be replicated in independent datasets and, if validated, may provide useful measures of disease progression and response to therapy.

A cross-sectional study of hand function in inclusion body myositis: Implications for functional rating scale.

Inclusion body myositis (IBM) is a slowly progressive and heterogeneous disorder that is a challenge for measuring clinical trial efficacy. The current methods of measuring progression of the disease utilizes the Inclusion Body Myositis Functional Rating Scale, grip strength by dynamometer, and finger flexor strength. One of the hallmarks of the disease is selective deep finger flexor weakness. To date, no adequate data has been available to determine how well the Functional Rating Scale relates to this hallmark physical exam deficit. Our study is the first to investigate the degree of correlation between items pertaining to hand function in the Functional Rating Scale with measured grip and finger flexor strength in IBM patients. We have found a lower than expected correlation with finger flexor strength and even lower with grip strength. The current Functional Rating Scale will benefit from optimization to measure clinical progression more accurately.

MRI-informed muscle biopsies correlate MRI with pathology and DUX4 target gene expression in FSHD.

Facioscapulohumeral muscular dystrophy (FSHD) is a common, dominantly inherited disease caused by the epigenetic de-repression of the DUX4 gene, a transcription factor normally repressed in skeletal muscle. As targeted therapies are now possible in FSHD, a better understanding of the relationship between DUX4 activity, muscle pathology and muscle magnetic resonance imaging (MRI) changes is crucial both to understand disease mechanisms and for the design of future clinical trials. Here, we performed MRIs of the lower extremities in 36 individuals with FSHD, followed by needle muscle biopsies in safely accessible muscles. We examined the correlation between MRI characteristics, muscle pathology and expression of DUX4 target genes. Results show that the presence of elevated MRI short tau inversion recovery signal has substantial predictive value in identifying muscles with active disease as determined by histopathology and DUX4 target gene expression. In addition, DUX4 target gene expression was detected only in FSHD-affected muscles and not in control muscles. These results support the use of MRI to identify FSHD muscles most likely to have active disease and higher levels of DUX4 target gene expression and might be useful in early phase therapeutic trials to demonstrate target engagement in therapies aiming to suppress DUX4 expression.

Molecular Therapies for Muscular Dystrophies.

PURPOSE OF REVIEW: To construct a framework to understand the different molecular interventions for muscular dystrophy. RECENT FINDINGS: The recent approval of antisense oligonucleotides treatment for Duchenne muscular dystrophy and spinal muscular atrophy and current clinical trials using recombinant adeno-associated virus for the treatment of those diseases suggests that we are at a tipping point where we are able to treat and potentially cure muscular dystrophies. Understanding the basic molecular pathogenesis of muscular dystrophies and the molecular biology of the treatment allows for critical evaluation of the proposed therapies.

Neutral lipid storage disease with myopathy: Further phenotypic characterization of a rare PNPLA2 variant.

Neutral lipid storage disease with myopathy is a rare disorder of lipid metabolism caused by variants in the Patatin-Like Phospholipase Domain Containing 2 (PNPLA2) gene. Diagnosis is often delayed due to variable presentations, which is of concern due to increased risk of cardiomyopathy. Better phenotype-genotype characterization is necessary to improve speed and accuracy of diagnosis. Here, we describe a 32-year-old woman of Hmong descent with progressive muscle pain and weakness who had a muscle biopsy with characteristic features of a lipid storage myopathy. Genetic testing revealed a homozygous splice site variant in PNPLA2, c.757 + 1G > T. This case, in combination with the one previously reported case of this PNPLA2 variant, also in a family of Hmong descent, suggests this particular variant may be unique to the Hmong population, a Southeast Asian minority group living in the United States, who immigrated to the United States as refugees after the Vietnam War.

MRI change metrics of facioscapulohumeral muscular dystrophy: Stir and T1.

INTRODUCTION: MRI evaluation in facioscapulohumeral muscular dystrophy (FSHD) demonstrates fatty replacement and inflammation/edema in muscle. Our previous work demonstrated short T1 inversion recovery (STIR)-hyperintense (STIR+) signal in muscle 2 years before fatty replacement. We evaluated leg muscle STIR changes and fatty replacement within 14 months. METHODS: FSHD subjects received 2 MRI scans of thigh and calf over a 6.9- to 13.8-month interval. Quality of life measures were collected. One Radiologist rated muscle changes on a semi-quantitative scale. RESULTS: Fifteen subjects completed longitudinal imaging. Four STIR + muscles and 3 STIR-normal (STIR-) muscles were rated as progressing to fatty tissue over the study period. DISCUSSION: STIR + muscles with confluent regions of fat at baseline increased more in fat, while STIR- muscles had increases in septal-fat over the study period. These changes may reflect two phases of FSHD, demonstrating MRI sensitivity is weighted toward gross pathological phases of the disease. Muscle Nerve 57: 905-912, 2018.