Treatment resistance in inclusion body myositis: the role of mast cells.

Inclusion body myositis is the commonest acquired myopathy in those over 50 years of age. Although it is classified as an idiopathic inflammatory myopathy and the most frequent finding on muscle biopsy in inclusion body myositis is an endomysial inflammatory infiltrate, it is clinically distinct from other myositis, including a lack of response to immunosuppressive medication. Neurogenic changes are commonly reported in inclusion body myositis and inflammatory changes are observed in muscle following neurogenic injury. The objective of our study was to explore whether neurogenic inflammation plays a role in the pathogenesis of inclusion body myositis, possibly explaining its resistance to immunosuppression. The number of mast cells and presence of neuropeptides, substance P and calcitonin gene-related peptide, were assessed in 48 cases of inclusion body myositis, 11 cases of steroid responsive myositis, two cases of focal myositis associated with neurogenic injury, and ten normal controls. The number of mast cells in inclusion body myositis focal and myositis associated to neurogenic injury were significantly greater than that observed in steroid responsive myositis. Our findings suggest that neurogenic inflammation mediated through mast cells may play a role in the pathogenesis of inclusion body myositis, and focal myositis associated to neurogenic injury, and thus, explain in some part its lack of response to immunosuppressive treatments.

VCP activator reverses nuclear proteostasis defects and enhances TDP-43 aggregate clearance in multisystem proteinopathy models.

Pathogenic variants in valosin-containing protein (VCP) cause multisystem proteinopathy (MSP), a disease characterized by multiple clinical phenotypes including inclusion body myopathy, Paget's disease of the bone, and frontotemporal dementia (FTD). How such diverse phenotypes are driven by pathogenic VCP variants is not known. We found that these diseases exhibit a common pathologic feature: ubiquitinated intranuclear inclusions affecting myocytes, osteoclasts, and neurons. Moreover, knock-in cell lines harboring MSP variants show a reduction in nuclear VCP. Given that MSP is associated with neuronal intranuclear inclusions comprised of TDP-43 protein, we developed a cellular model whereby proteostatic stress results in the formation of insoluble intranuclear TDP-43 aggregates. Consistent with a loss of nuclear VCP function, cells harboring MSP variants or cells treated with VCP inhibitor exhibited decreased clearance of insoluble intranuclear TDP-43 aggregates. Moreover, we identified 4 compounds that activate VCP primarily by increasing D2 ATPase activity, where pharmacologic VCP activation appears to enhance clearance of insoluble intranuclear TDP-43 aggregate. Our findings suggest that VCP function is important for nuclear protein homeostasis, that impaired nuclear proteostasis may contribute to MSP, and that VCP activation may be a potential therapeutic by virtue of enhancing the clearance of intranuclear protein aggregates.

Effect of sirolimus on muscle in inclusion body myositis observed with magnetic resonance imaging and spectroscopy.

BACKGROUND: Finding sensitive clinical outcome measures has become crucial in natural history studies and therapeutic trials of neuromuscular disorders. Here, we focus on 1-year longitudinal data from quantitative magnetic resonance imaging (MRI) and phosphorus magnetic resonance spectroscopy (31P MRS) in a placebo-controlled study of sirolimus for inclusion body myositis (IBM), also examining their links to functional, strength, and clinical parameters in lower limb muscles. METHODS: Quantitative MRI and 31P MRS data were collected at 3 T from a single site, involving 44 patients (22 on placebo, 22 on sirolimus) at baseline and year-1, and 21 healthy controls. Assessments included fat fraction (FF), contractile cross-sectional area (cCSA), and water T2 in global leg and thigh segments, muscle groups, individual muscles, as well as 31P MRS indices in quadriceps or triceps surae. Analyses covered patient-control comparisons, annual change assessments via standard t-tests and linear mixed models, calculation of standardized response means (SRM), and exploration of correlations between MRI, 31P MRS, functional, strength, and clinical parameters. RESULTS: The quadriceps and gastrocnemius medialis muscles had the highest FF values, displaying notable heterogeneity and asymmetry, particularly in the quadriceps. In the placebo group, the median 1-year FF increase in the quadriceps was 3.2% (P < 0.001), whereas in the sirolimus group, it was 0.7% (P = 0.033). Both groups experienced a significant decrease in cCSA in the quadriceps after 1 year (P < 0.001), with median changes of 12.6% for the placebo group and 5.5% for the sirolimus group. Differences in FF and cCSA changes between the two groups were significant (P < 0.001). SRM values for FF and cCSA were 1.3 and 1.4 in the placebo group and 0.5 and 0.8 in the sirolimus group, respectively. Water T2 values were highest in the quadriceps muscles of both groups, significantly exceeding control values in both groups (P < 0.001) and were higher in the placebo group than in the sirolimus group. After treatment, water T2 increased significantly only in the sirolimus group's quadriceps (P < 0.01). Multiple 31P MRS indices were abnormal in patients compared to controls and remained unchanged after treatment. Significant correlations were identified between baseline water T2 and FF at baseline and the change in FF (P < 0.001). Additionally, significant correlations were observed between FF, cCSA, water T2, and functional and strength outcome measures. CONCLUSIONS: This study has demonstrated that quantitative MRI/31P MRS can discern measurable differences between placebo and sirolimus-treated IBM patients, offering promise for future therapeutic trials in idiopathic inflammatory myopathies such as IBM.

272nd ENMC international workshop: 10 Years of progress - revision of the ENMC 2013 diagnostic criteria for inclusion body myositis and clinical trial readiness. 16-18 June 2023, Hoofddorp, The Netherlands.

Since the publication of the 2013 European Neuromuscular Center (ENMC) diagnostic criteria for Inclusion Body Myositis (IBM), several advances have been made regarding IBM epidemiology, pathogenesis, diagnostic tools, and clinical trial readiness. Novel diagnostic tools include muscle imaging techniques such as MRI and ultrasound, and serological testing for cytosolic 5'-nucleotidase-1A antibodies. The 272nd ENMC workshop aimed to develop new diagnostic criteria, discuss clinical outcome measures and clinical trial readiness. The workshop started with patient representatives highlighting several understudied symptoms and the urge for a timely diagnosis. This was followed by presentations from IBM experts highlighting the new developments in the field. This report is composed of two parts, the first part providing new diagnostic criteria on which consensus was achieved. The second part focuses on the use of outcome measures in clinical practice and clinical trials, highlighting current limitations and outlining the goals for future studies.

Safety and efficacy of arimoclomol for inclusion body myositis: a multicentre, randomised, double-blind, placebo-controlled trial.

BACKGROUND: Inclusion body myositis is the most common progressive muscle wasting disease in people older than 50 years, with no effective drug treatment. Arimoclomol is an oral co-inducer of the cellular heat shock response that was safe and well-tolerated in a pilot study of inclusion body myositis, reduced key pathological markers of inclusion body myositis in two in-vitro models representing degenerative and inflammatory components of this disease, and improved disease pathology and muscle function in mutant valosin-containing protein mice. In the current study, we aimed to assess the safety, tolerability, and efficacy of arimoclomol in people with inclusion body myositis. METHODS: This multicentre, randomised, double-blind, placebo-controlled study enrolled adults in specialist neuromuscular centres in the USA (11 centres) and UK (one centre). Eligible participants had a diagnosis of inclusion body myositis fulfilling the European Neuromuscular Centre research diagnostic criteria 2011. Participants were randomised (1:1) to receive either oral arimoclomol 400 mg or matching placebo three times daily (1200 mg/day) for 20 months. The randomisation sequence was computer generated centrally using a permuted block algorithm with randomisation numbers masked to participants and trial staff, including those assessing outcomes. The primary endpoint was the change from baseline to month 20 in the Inclusion Body Myositis Functional Rating Scale (IBMFRS) total score, assessed in all randomly assigned participants, except for those who were randomised in error and did not receive any study medication, and those who did not meet inclusion criteria. Safety analyses included all randomly assigned participants who received at least one dose of study medication. This trial is registered with ClinicalTrials.gov, number NCT02753530, and is completed. FINDINGS: Between Aug 16, 2017 and May 22, 2019, 152 participants with inclusion body myositis were randomly assigned to arimoclomol (n=74) or placebo (n=78). One participant was randomised in error (to arimoclomol) but not treated, and another (assigned to placebo) did not meet inclusion criteria. 150 participants (114 [76%] male and 36 [24%] female) were included in the efficacy analyses, 73 in the arimoclomol group and 77 in the placebo group. 126 completed the trial on treatment (56 [77%] and 70 [90%], respectively) and the most common reason for treatment discontinuation was adverse events. At month 20, mean IBMFRS change from baseline was not statistically significantly different between arimoclomol and placebo (-3·26, 95% CI -4·15 to -2·36 in the arimoclomol group vs -2·26, -3·11 to -1·41 in the placebo group; mean difference -0·99 [95% CI -2·23 to 0·24]; p=0·12). Adverse events leading to discontinuation occurred in 13 (18%) of 73 participants in the arimoclomol group and four (5%) of 78 participants in the placebo group. Serious adverse events occurred in 11 (15%) participants in the arimoclomol group and 18 (23%) in the placebo group. Elevated transaminases three times or more of the upper limit of normal occurred in five (7%) participants in the arimoclomol group and one (1%) in the placebo group. Tubulointerstitial nephritis was observed in one (1%) participant in the arimoclomol group and none in the placebo group. INTERPRETATION: Arimoclomol did not improve efficacy outcomes, relative to placebo, but had an acceptable safety profile in individuals with inclusion body myositis. This is one of the largest trials done in people with inclusion body myositis, providing data on disease progression that might be used for subsequent clinical trial design. FUNDING: US Food and Drug Administration Office of Orphan Products Development and Orphazyme.

Myasthenia gravis with inclusion body myositis: A case report.

We present the case of a 75-year-old man diagnosed with myasthenia gravis (MG) based on lower leg weakness and ptosis for the past 2 months before admission to our hospital. The patient was anti-acetylcholine receptor antibody-positive at admission. He was treated with pyridostigmine bromide and prednisolone, which improved the ptosis, but the lower leg muscle weakness remained. An additional lower leg magnetic resonance imaging examination suggested myositis. Inclusion body myositis (IBM) was diagnosed after a subsequent muscle biopsy. Although MG is often associated with inflammatory myopathy, IBM is rare. There is no effective treatment for IBM, but various treatment possibilities have recently been proposed. This case emphasises that myositis complications, including IBM, should be considered when elevated creatine kinase levels are observed and conventional treatments do not address chronic muscle weakness.

Antibody Therapies in Autoimmune Inflammatory Myopathies: Promising Treatment Options.

Inflammatory myopathies, including polymyositis (PM), dermatomyositis (DM), inclusion body myositis (IBM), necrotizing myopathy (NM), antisynthetase syndrome (ASS) and overlap myositis (OM), in short myositis, are rare diseases. All forms of myositis have progressive muscle weakness in common, with each subtype characterized by different autoantibody profiles, histological findings and extramuscular manifestations. Due to better understanding of the pathogenesis of the muscle inflammation in myositis, new molecular pathways for targeted therapy have been discovered. Current therapies aim at different components of the innate or the adaptive immune response. Additionally, non-inflammatory mechanisms in myositis have come into focus as possible treatment targets. The use of therapeutical antibodies in myositis has been examined in various clinical studies, several of them randomized controlled ones: Depletion of B-cells by rituximab has been established as treatment of refractory myositis. IVIG, an antibody therapy in the wider sense, has now been licensed for DM following a recent positive clinical trial. Negative study results were reported in randomized trials with infliximab, sifalimumab and bimagrumab. Studies on basiliximab and eculizumab are currently underway, and are expected to yield results in a couple of years. Despite some promising results of clinical studies with antibody therapy in myositis, further research is crucial to optimize the treatment for this debilitating disease and to find treatment alternatives for treatment-refractory patients.

Sirolimus leads to rapid and sustained clinical improvement of motor deficits in a patient with inclusion body myositis.

BACKGROUND AND PURPOSE: To provide further evidence for sirolimus, a mammalian target of rapamycin inhibitor, as a treatment strategy for patients with inclusion body myositis (IBM). METHODS: We acquired longitudinal clinical data and immunological assessments of CD8+ T-cell subsets in peripheral blood for evaluation of potential anti-inflammatory treatment effects of sirolimus. RESULTS: Therapy with sirolimus 2 mg/day by mouth led to rapid and sustained clinical improvement of motor symptoms for an observation period of more than 1 year. Treatment was well tolerated, with no occurrence of adverse effects. We did not observe a meaningful alteration of CD8+ T-cell subsets in our patient after 9 and 12 months compared to baseline. CONCLUSIONS: The significant and persistent clinical improvement highlights the use of sirolimus as a potential treatment option in patients with IBM. In light of the lack of immunological treatment effects observed for cytotoxic CD8+ T cells, further studies should investigate the potential myoprotective effects of sirolimus.

Botulinum toxin treatment improves dysphagia in patients with oculopharyngeal muscular dystrophy and sporadic inclusion body myositis.

OBJECTIVE: Dysphagia can be troublesome in sporadic inclusion body myositis (sIBM) and oculopharyngeal muscular dystrophy (OPMD), but no established treatment exists. Cricopharyngeal muscle botulinum toxin injection has at case level been reported to be effective. We evaluated safety and efficacy of botulinum toxin injections in the cricopharyngeal muscle in patients with dysphagia due to sIBM or OPMD. METHODS: Participants were included from our outpatient clinic. Cricopharyngeal constriction was confirmed by laryngoscopy. After EMG confirmation of needle placement in the cricopharyngeal muscle, botulinum toxin A was injected in awake patients. An individualized dose of 5-10 units of botulinum toxin A was applied initially and titrated up a maximum of 3 times. Outcome measures were change in dysphagia questionnaire, timed cold-water swallow test and subjective dysphagia status (worse, unchanged, improved). Due to the need for individualized dosing and a limited number of available patients, an uncontrolled, un-blinded design was used. RESULTS: Thirteen patients, 3 with OPMD, received at least 1 injection. In the dysphagia questionnaire, all but 2 subjects, none with subjective worsening, improved (p < 0.001). Subjectively, seven felt an improvement, 4 no change and 2 a worsening. No overall change was seen the timed cold-water swallow test. No serious adverse events were observed. CONCLUSION: Botulinum toxin injection of the cricopharyngeal muscle in patients with OPMD and sIBM had a beneficial effect on dysphagia in most of the treated patients. Two of 13 patients experienced a temporary worsening not reflected in dysphagia score. Limitations are the un-blinded and un-randomized design and subjective assessments methods. PROSPECTIVE TRIAL REGISTRATION: EudraCT-number: 2014-002210-23.