VCP/p97 inhibitor CB-5083 modulates muscle pathology in a mouse model of VCP inclusion body myopathy

Background Pathogenic gain of function variants in Valosin-containing protein (VCP) cause a unique disease characterized by inclusion body myopathy with early-onset Paget disease of bone and frontotemporal dementia (also known as Multisystem proteinopathy (MSP)). Previous studies in drosophila models of VCP disease indicate treatment with VCP inhibitors mitigates disease pathology. Earlier-generation VCP inhibitors display off-target effects and relatively low therapeutic potency. New generation of VCP inhibitors needs to be evaluated in a mouse model of VCP disease. In this study, we tested the safety and efficacy of a novel and potent VCP inhibitor, CB-5083 using VCP patient-derived myoblast cells and an animal model of VCP disease. Methods First, we analyzed the effect of CB-5083 in patient-derived myoblasts on the typical disease autophagy and TDP-43 profile by Western blot. Next, we determined the maximum tolerated dosage of CB-5083 in mice and treated the 2-month-old VCPR155H/R155H mice for 5 months with 15 mg/kg CB-5083. We analyzed motor function monthly by Rotarod; and we assessed the end-point blood toxicology, and the muscle and brain pathology, including autophagy and TDP-43 profile, using Western blot and immunohistochemistry. We also treated 12-month-old VCPR155H/+ mice for 6 months and performed similar analysis. Finally, we assessed the potential side effects of CB-5083 on retinal function, using electroretinography in chronically treated VCPR155H/155H mice. Results In vitro analyses using patient-derived myoblasts confirmed that CB-5083 can modulate expression of the proteins in the autophagy pathways. We found that chronic CB-5083 treatment is well tolerated in the homozygous mice harboring patient-specific VCP variant, R155H, and can ameliorate the muscle pathology characteristic of the disease. VCP-associated pathology biomarkers, such as elevated TDP-43 and p62 levels, were significantly reduced. Finally, to address the potential adverse effect of CB-5083 on visual function observed in a previous oncology clinical trial, we analyzed retinal function in mice treated with moderate doses of CB-5083 for 5 months and documented the absence of permanent ocular toxicity. Conclusions Altogether, these findings suggest that long-term use of CB-5083 by moderate doses is safe and can improve VCP disease-associated muscle pathology. Our results provide translationally relevant evidence that VCP inhibitors could be beneficial in the treatment of VCP disease.

Phenotypic diversity in an international Cure VCP Disease registry

Background Dominant mutations in valosin-containing protein (VCP) gene cause an adult onset inclusion body myopathy, Paget’s disease of bone, and frontotemporal dementia also termed multisystem proteinopathy (MSP). The genotype-phenotype relationships in VCP-related MSP are still being defined; in order to understand this better, we investigated the phenotypic diversity and patterns of weakness in the Cure VCP Disease Patient Registry. Methods Cure VCP Disease, Inc. was founded in 2018 for the purpose of connecting patients with VCP gene mutations and researchers to help advance treatments and cures. Cure VCP Disease Patient Registry is maintained by Coordination of Rare Diseases at Sanford. The results of two questionnaires with a 5-point Likert scale questions regarding to patients’ disease onset, symptoms, and daily life were obtained from 59 participants (28 males and 31 females) between June 2018 and May 2020. Independent of the registry, 22 patients were examined at the Cure VCP Disease annual patient conference in 2019. Results In the questionnaires of the registry, fifty-three patients (90%) reported that they were with inclusion body myopathy, 17 patients (29%) with Paget’s disease of bone, eight patients (14%) with dementia, two patients (3%) with amyotrophic lateral sclerosis, and a patient with parkinsonism. Thirteen patients (22%) reported dysphagia and 25 patients (42%) reported dyspnea on exertion. A self-reported functional rating scale for motor function identified challenges with sit to stand (72%), walking (67%), and climbing stairs (85%). Thirty-five (59%) patients in the registry answered that their quality of life is more than good. As for the weakness pattern of the 22 patients who were evaluated at the Cure VCP Disease annual conference, 50% of patients had facial weakness, 55% had scapular winging, 68% had upper proximal weakness, 41% had upper distal weakness, 77% had lower proximal, and 64% had lower distal weakness. Conclusions The Cure VCP Disease Patient Registry is useful for deepening the understanding of patient daily life, which would be a basis to develop appropriate clinical outcome measures. The registry data is consistent with previous studies evaluating VCP patients in the clinical setting. Patient advocacy groups are essential in developing and maintaining disease registries.

Hereditary inclusion body myopathy: a clinical and genetic review

Introduction. Inclusion body myositis represents the most common acquired myopathy in clinical practice in patients over 50 years old. Despite classical approach to this myopathy as an inflammatory disorder, a muscle degenerative disorder is now considered the main mechanism linked to these vacuolar myopathies. Hereditary presentations, although quite rare, represent an expanding and underrecognized group in clinical practice. Objective. perform a structured review of the current literature regarding hereditary inclusion body myopathies. Method. review of U.S. NLM PubMed and MEDLINE database of original articles, case reports, case series and review articles including the terms “inclusion body myositis” OR “inclusion body myopathy” AND “genetics” OR “hereditary”. Results. We present in this article a wide review regarding the main clinical, imaging, pathophysiological, genetic and therapeutic aspects related to hereditary myopathies linked to seven different clinical and genetic presentations (GNE, MATR3, VCP, SQSTM1, MYH2, HNRNPA2B1 and HNRNPA1). Conclusion. Hereditary inclusion body myopathy is associated with at least 7 distinct clinic and genetic monogenic forms.

A Natural History Study of VCP Associated Vacuolar Myopathy in a Patient with the Common R155H Mutation

Background: IBMPFD (Inclusion Body Myopathy associated with Paget disease of the bone and Frontotemporal Dementia) is an autosomal dominant inherited disease caused by VCP gene mutations. Very little natural history data exists on this disease. We report a patient with a significant family history of IBMPFD associated with the common R155H mutation in the VCP gene. Objective: This study will address the lack of long-term data for muscle strength, and respiratory function in IBMPFD. The hypothesis is that detailed analysis in a single patient will provide meaningful natural history data in IBMPFD, a progressive neurodegenerative disease. Method: Regression analysis was performed across multiple parameters related to myopathy including dynamometry, MRC scale, IBM functional rating scale, pulmonary function studies and sleep quality. Results: Measurements of this patient highlight progressive generalized weakness in proximal and distal regions, decline in pulmonary function, and asymmetrical strength differences of the upper extremities. Measurements over five years revealed an overall deterioration with a slope of -1.13 and R2 value of 0.77. Conclusion: This unique data derived from long-term evaluations in a patient provides the first report of the rate of progression of muscle weakness and pulmonary function deterioration in VCP associated inclusion body myopathy.