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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., Competing Interests: Declaration of interests RT reports grants from and contracts with the US National Institutes of Health, fees for consulting, participation on a data safety monitoring board, and data review, and support for attending meetings from Fulcrum Therapeutics. KRW is an employee of the Novartis Institute for Biomedical Research, Novartis. JIH reports consulting fees from Vertex Therapeutics and Dyne Therapeutics. DGL reports receiving institutional support for the ReDUX4 clinical trial and grant funding for administrative support for FSHD Clinical Trials Research Network, a K23 Career Development grant (paid to institution) to fund an imaging study in facioscapulohumeral muscular dystrophy, honoraria for co-chairing the annual research meeting of the FSHD Society, and institutional funding for facioscapulohumeral muscular dystrophy natural history studies by the FSHD Clinical Trials Research Network. JMS reports grants from or contracts with the US National Institutes of Health, the Muscular Dystrophy Association, the FSHD Society, Friends of FSH Research, FSHD Canada, and the US Centers for Disease Control and Prevention; consulting fees from Fulcrum Therapeutics, Epic Bio, Dyne, Avidity, Roche, EcoR1, and Treat NMD Advisory Committee for Therapeutics; and stock and stock options in Dyne. LHW reports consulting fees from Fulcrum Therapeutics and Avidity Therapeutics, payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing, educational events, and attending meetings or travel from Fulcrum Therapeutics, and payment for participation on a data safety monitoring and advisory board from Syneos. AG reports consulting fees from Fulcrum, Quralis, AL-S Pharma, Mitsubishi Tanabe Pharma America, Amylyx, Alexion, and Cytokinetics and support for attending meetings or travel from Amylyx, Quralis, Mitsubishi Tanabe Pharma America, Alexion, and AL-S Pharma; she serves on the Board of AL-S Canada and has stock or stock options in Quralis. SS reports payment or honoraria for lectures, presentations, speakers bureaus, manuscript writing, and educational events from Lupin and Fulcrum Therapeutics, payment for expert testimony from Axelys and Ology, support for attending meetings or travel from UCB, Sanofi, Biogen, and Fulcrum Therapeutics, and support for participation in data safety monitoring and advisory boards from Sanofi, Biogen, Amicus, UCB, and Alexion. HL receives support from the Canadian Institutes of Health Research, Muscular Dystrophy Canada, the Canada Foundation for Innovation, and the Canada Research Chairs program. SG reports being contracted as study-site principal investigator and receiving study-related equipment for the ReDUX4 phase 2 and 3 clinical trials from Fulcrum Therapeutics. LJH reports receiving consulting fees from Myocea and HC Wainwright, and support for attending meetings or travel from the Solve FSHD Foundation. NJ reports employment as a contractor for Fulcrum Therapeutics, Dyne, Avidity, Avexis, Biogen, Triplet, AMO Pharma, ML Bio solutions, and Askbio, consulting fees from Dyne, Avidity, Novartis Gene Therapies, Fulcrum, Biogen, and participation on data safety monitoring and advisory board for Biogen Idec. SHS reports institutional support from Fulcrum Therapeutics, including for participation on an advisory board. BvE reports grants from or contracts with Prinses Beatrix Spierfonds, the Dutch FSHD Foundation, and Stichting Spieren voor Spieren, royalties or licenses from patent EP2012740236, and institutional payments for consulting and participation on data safety monitoring and advisory boards from Fulcrum Therapeutics, Facio, Avidity, Dyne, Arrowhead, Biomarin, Pepgen, and Teva. JK reports institutional payment for ReDUX4. PW and ODL report receiving support for attending meetings or travel from, and stock or stock options in, AMRA Medical. CM, DC, MLM, AA, and LAR were full-time employees of Fulcrum Therapeutics at the time of manuscript preparation and own stock or have stock options in Fulcrum Therapeutics. MLM also received travel support from Fulcrum Therapeutics. RJG reports being an employee, board member, and consultant for Fulcrum Therapeutics, and holds stock or stock options in the company. JGJ is an employee of Fulcrum Therapeutics. All other authors report no competing interests., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

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., (© The Author(s) 2024. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

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., Competing Interests: Declaration of Competing Interest LHW reports consultancy/advisory board for Fulcrum Therapeutics, Argenx, Avidity, Ultragenyx, PepGen, data safety monitoring board for Scholar Rock. KE has served on advisory boards or has received consulting fees from Biogen, Acceleron, PTC, Ionis Pharmaceuticals, Fulcrum Therapeutics, Dyne Therapeutics, Avidity Biosciences and Roche. RNT reports consultancy with Fulcrum Therapeutics, Arrowhead, Dyne Therapeutics, Acceleron, MT Pharma, miRecule, and Roche Pharma. JS has served as consultant for Arrowhead, ML Bio, MT Pharma, Epic Bio, Armatus; served on a Scientific Advisory or Data Safety Monitoring board for Dyne Therapeutics, Avidity, Fulcrum Therapeutics, Roche. PS has served as consultant for Sarepta, Genentech, Biogen, Alexion, Argenx, UCB; served on speakers’ bureaus for CSL Behring, Grifols, Alexion, Biogen, Genentech, Argenx, Catalyst. KRW is an employee of F. Hoffmann-La Roche Ltd. BE received research funding from Biogen, Genentech, Alexion, Pharnext, and Viela Bio and served as a consultant for Biogen, Genentech, and Argenx. NJ has received grant funding from NINDS (R01NS104010), NCATS (21TR003184), CDC (U01DD001242–02) and the FDA (7R01FD006071–02). He receives royalties from the CCMDHI and the CMTHI; receives research funds from Dyne, AveXis, Takeda, Sanofi Genzyme, Pepgen, Vertex Pharmaceuticals, Fulcrum Therapeutics, Sarepta, and AskBio; has provided consultation for Takeda, Pepgen, Arthex, AveXis, AMO Pharma, Fulcrum Therapeutics, Dyne, Avidity, and Vertex Pharmaceuticals. KM reports consultancy for Avidity Biosciences. RJB reports consultancy/advisory board for Aavanti Bio, Scholar Rock, Avexis, Pfizer, Reata, and Sarepta Therapeutics. SLO, MRP, MD have no disclosures., (Copyright © 2023. Published by Elsevier B.V.)

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., (© 2022 Wiley Periodicals LLC.)

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.

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.

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.

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., (© The Author(s) 2020. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)

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.

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., (© 2017 Wiley Periodicals, Inc.)

Facioscapulohumeral muscular dystrophy (FSHD) is a clinically recognizable and relatively common muscular dystrophy. It is inherited mostly as an autosomal dominant disease or in a minority of cases, in a digenic pattern. The disease manifestation is variable and most likely dependent on genetic and epigenetic factors. We review the history, epidemiology, clinical presentation, and genetics of the disease, present the recently elucidated molecular pathogenesis, discuss the pathology and the possible consequence of the inflammation seen in the muscle biopsies, and consider future treatments.