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

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.

Clinical Outcome Assessments and Biomarkers in Charcot-Marie-Tooth Disease

Charcot-Marie-Tooth disease (CMT) encompasses a diverse group of genetic forms of inherited peripheral neuropathy and stands as the most common hereditary neurologic disease worldwide. At present, no disease-modifying treatments exist for any form of CMT. However, promising therapeutic strategies are rapidly emerging, necessitating careful consideration of clinical outcome assessments (COAs) and clinical trial design. In this review, we discuss the challenges and successes over the past 2 decades in efforts to design and validate COAs and disease biomarkers of CMT. Natural history studies and completed clinical trials have underscored the limitations of early clinical scales for CMT, including the neuropathy impairment score, overall neuropathy limitation scale, and CMT neuropathy score. These studies prompted the development of newer, psychometrically supported scales including the CMT neuropathy score version 2, CMT pediatric scale, CMT infant scale, CMT functional outcome measure, and CMT health index. Although promising, many of these scales have yet to be formally tested in longitudinal studies. Given inherent challenges of relying solely on COAs in slowly progressive forms of CMT, there is growing recognition of the need for objective disease biomarkers that could serve as surrogate end points in clinical trials. Among these, MRI muscle fat fraction in the lower extremities has proven the most responsive biomarker to date, although its relationship to functional outcomes and its performance in treatment trials remain uncertain. Serum biomarkers including neurofilament light, transmembrane protease serine 5, specific microRNAs, neural cell adhesion molecule 1, and growth and differentiation factor 15 reliably distinguish patients with CMT from controls, but their responsiveness to effective therapies also remains unknown. Although the optimal combination of outcome measures in CMT has yet to be established, many of the most promising COAs and biomarkers are now being put to the test in ongoing clinical trials. These early studies will also help address other critical clinical trial considerations, such as patient selection and enrollment targets, which will become increasingly important in this exciting new era of bringing the first disease-modifying treatments to people living with CMT.

Relationship Between Quantitative Magnetic Resonance Imaging Measures and Functional Changes in Patients With Duchenne Muscular Dystrophy

INTRODUCTION/AIMS

Improved methodologies to monitor the progression of Duchenne muscular dystrophy (DMD) are needed, especially in the context of clinical trials. We report changes in muscle magnetic resonance imaging (MRI) parameters in participants with DMD, including changes in lean muscle volume (LMV), muscle fat fraction (MFF), and muscle fat infiltration (MFI) and their relationship to changes in functional parameters.

METHODS

MRI data were obtained as part of a clinical study (NCT02310763) of domagrozumab, an antibody-targeting myostatin that negatively regulates skeletal muscle mass. This post hoc analysis evaluated participants with Dixon MRI data and corresponding functional data at baseline and weeks 49 and 97. Images were analyzed to evaluate changes in adductors, hamstrings, and quadriceps.

RESULTS

There was a positive correlation between increases in LMV and function. LMV changes in adductors (R = 0.51) and quadriceps (R = 0.54) showed a stronger correlation with function than LMV changes in hamstrings (R = 0.30). There was a negative correlation between MFF and MFI, respectively, and function in adductors (R = -0.57, R = -0.42), quadriceps (R = -0.59, R = -0.50), and hamstrings (R = -0.53, R = -048). Participants with preserved North Star Ambulatory Assessment scores had high total LMV (LMVtot) and low total MFI (MFItot). Low ratios of LMVtot to MFItot, or participants with small LMVtot and high MFItot, appeared to have a rapid decline in function and loss of ambulation.

DISCUSSION

These findings support the use of MRI biomarkers as potential surrogate endpoints in clinical trials of patients with DMD.

TRIAL REGISTRATION

ClinicalTrials.gov identifiers: NCT02310763.

The journey of p38 MAP kinase inhibitors: From bench to bedside in treating inflammatory diseases

The p38 mitogen-activated protein kinase (MAPK) pathway is pivotal in regulating inflammatory responses and has emerged as a key target for the development of small-molecule inhibitors aimed at treating inflammatory diseases. In arthritis, especially rheumatoid arthritis (RA), the p38 MAPK pathway contributes to chronic inflammation and joint destruction by promoting the production of pro-inflammatory cytokines. Preclinical studies have shown that small-molecule inhibitors targeting the p38 MAPK pathway hold significant promise, exhibiting the potential to reduce inflammation and preserve joint integrity. Targeting this pathway presents a novel therapeutic approach to mitigating inflammation. This review traces the evolution of p38 MAP kinase inhibitors from initial laboratory studies to clinical candidates, underscoring their potential to significantly alter the treatment approach for inflammatory diseases.

Temporal variation in p38-mediated regulation of DUX4 in facioscapulohumeral muscular dystrophy

Facioscapulohumeral muscular dystrophy (FSHD) is a degenerative muscle disease caused by loss of epigenetic silencing and ectopic reactivation of the embryonic double homeobox protein 4 gene (DUX4) in skeletal muscle. The p38 MAP kinase inhibitor losmapimod is currently being tested in FSHD clinical trials due to the finding that p38 inhibition suppresses DUX4 expression in preclinical models. However, the role of p38 in regulating DUX4 at different myogenic stages has not been investigated. We used genetic and pharmacologic tools in FSHD patient-derived myoblasts/myocytes to explore the temporal role of p38 in differentiation-induced DUX4 expression. Deletion of MAPK14/11 or inhibition of p38α/β caused a significant reduction in early differentiation-dependent increases in DUX4 and DUX4 target gene expression. However, in MAPK14/11 knockout cells, there remains a differentiation-associated increase in DUX4 and DUX4 target gene expression later in differentiation. Furthermore, pharmacologic inhibition of p38α/β only partially decreased DUX4 and DUX4 target gene expression in late differentiating myotubes. In xenograft studies, p38α/β inhibition by losmapimod failed to suppress DUX4 target gene expression in late FSHD xenografts. Our results show that while p38 is critical for DUX4 expression during early myogenesis, later in myogenesis a significant level of DUX4 expression is independent of p38α/β activity.

Therapeutic Strategy and Clinical Path of Facioscapulohumeral Muscular Dystrophy: Review of the Current Literature

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal dominant genetic disease, which is caused by the mistaken expression of double homeobox protein 4 protein 4 (DUX4) in skeletal muscle. Patients with FSHD are usually accompanied by degenerative changes in the face, shoulders, and upper muscles, gradually accumulating in the lower limb muscles. The severity of patients is quite different, and most patients end up using wheelchairs and losing their self-care ability. At present, the exploration of treatment strategies for FSHD has shifted from relieving symptoms to gene therapy, which brings hope to the future of patients, but the current gene therapy is only in the clinical trial stage. Here, we conducted a comprehensive search of the relevant literature using the keywords FSHD, DUX4, and gene therapy methods including ASOs, CRISPR, and RNAi in the PubMed and Web of Science databases. We discussed the current advancements in treatment strategies for FSHD, as well as ongoing preclinical and clinical trials related to FSHD. Additionally, we evaluated the advantages and limitations of various gene therapy approaches targeting DUX4 aimed at correcting the underlying genetic defect.

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.