401
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What is in the Neuromuscular Junction Literature? J Clin Neuromuscul Dis 2018; 20:76-84. [PMID: 30439753 DOI: 10.1097/cnd.0000000000000218] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
This update begins with myasthenia gravis and the roles of anti-agrin and cortactin antibodies. Regarding diagnosis, a report on repeated ice pack testing is highlighted as are several reports on the close correlation of electrodiagnostic testing with clinical features and the response to treatment. The incidence of head drop and associated clinical and ventilatory features are gleaned from a retrospective study. We also discuss a study that assessed the predominantly symmetric and conjugate ocular findings in MuSK-myasthenia gravis. Other topics that are covered include quality of life and preoperative risk. We then summarize the positive treatment trials of subcutaneous immunoglobulin and eculizumab. Turning to Lambert-Eaton Myasthenic Syndrome, we report on an epidemiologic study performed on the veteran affairs population, the results of the DAPPER study of 3, 4 diaminopyridine, and look to the future for other treatment options involving calcium gating modifiers.
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402
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Koike H, Nishi R, Ikeda S, Kawagashira Y, Iijima M, Katsuno M, Sobue G. Ultrastructural mechanisms of macrophage-induced demyelination in CIDP. Neurology 2018; 91:1051-1060. [PMID: 30429275 DOI: 10.1212/wnl.0000000000006625] [Citation(s) in RCA: 61] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 07/18/2018] [Indexed: 11/15/2022] Open
Abstract
Chronic inflammatory demyelinating polyneuropathy (CIDP) is a form of chronic neuropathy that is presumably caused by heterogeneous immune-mediated processes. Recent advances in the search for autoantibodies against components expressed at nodal regions, such as the nodes of Ranvier and paranodes, have substantially contributed to clarifying the pathogenesis of CIDP in a subpopulation of patients. In particular, immunoglobulin G4 (IgG4) antibodies to paranodal junction proteins, including neurofascin-155 and contactin-1, have attracted the attention of researchers. Paranodal dissection resulting from the attachment of IgG4 at paranodal junctions and the absence of macrophage-induced demyelination are characteristic pathologic features in patients who have these antibodies. By contrast, the mechanisms of neuropathy in cases with classical macrophage-induced demyelination remain unclear despite the long-standing recognition of this process in CIDP. In addition to complement-dependent damage provoked by autoantibodies, recent studies have shed light on antibody-dependent phagocytosis by macrophages without participation of complements. However, a direct association between specific autoantibodies and macrophage-induced demyelination has not been reported. Electron microscopic examination of longitudinal sections of sural nerve biopsy specimens suggested that macrophages recognize specific sites of myelinated fibers as the initial target of demyelination. The site that macrophages select to initiate myelin breakdown is located around the nodal regions in some patients and internode in others. Hence, it seems that the components that distinguish between the nodal regions and internode play a pivotal role in the behavior of macrophages that initiate phagocytosis of myelin. Further studies are needed to elucidate the mechanisms underlying macrophage-induced demyelination from this perspective.
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Affiliation(s)
- Haruki Koike
- From the Department of Neurology (H.K., R.N., S.I., Y.K., M.I., M.K., G.S.) and Research Division of Dementia and Neurodegenerative Disease (G.S.), Nagoya University Graduate School of Medicine, Japan.
| | - Ryoji Nishi
- From the Department of Neurology (H.K., R.N., S.I., Y.K., M.I., M.K., G.S.) and Research Division of Dementia and Neurodegenerative Disease (G.S.), Nagoya University Graduate School of Medicine, Japan
| | - Shohei Ikeda
- From the Department of Neurology (H.K., R.N., S.I., Y.K., M.I., M.K., G.S.) and Research Division of Dementia and Neurodegenerative Disease (G.S.), Nagoya University Graduate School of Medicine, Japan
| | - Yuichi Kawagashira
- From the Department of Neurology (H.K., R.N., S.I., Y.K., M.I., M.K., G.S.) and Research Division of Dementia and Neurodegenerative Disease (G.S.), Nagoya University Graduate School of Medicine, Japan
| | - Masahiro Iijima
- From the Department of Neurology (H.K., R.N., S.I., Y.K., M.I., M.K., G.S.) and Research Division of Dementia and Neurodegenerative Disease (G.S.), Nagoya University Graduate School of Medicine, Japan
| | - Masahisa Katsuno
- From the Department of Neurology (H.K., R.N., S.I., Y.K., M.I., M.K., G.S.) and Research Division of Dementia and Neurodegenerative Disease (G.S.), Nagoya University Graduate School of Medicine, Japan
| | - Gen Sobue
- From the Department of Neurology (H.K., R.N., S.I., Y.K., M.I., M.K., G.S.) and Research Division of Dementia and Neurodegenerative Disease (G.S.), Nagoya University Graduate School of Medicine, Japan
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403
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Abstract
Acquired Myasthenia Gravis (MG) is a neuromuscular disease caused by autoantibodies against components of the neuromuscular junction. It is a prototype organ-specific autoimmune disease with well-defined antigenic targets mainly the nicotinic acetylcholine receptor (AChR). Patients suffer from fluctuating, fatigable muscle weakness that worsens with activity and improves with rest. Various therapeutic strategies have been used over the years to alleviate MG symptoms. These strategies aim at improving the transmission of the nerve impulse to muscle or at lowering the immune system with steroids or immunosuppressant drugs. Nevertheless, MG remains a chronic disease and symptoms tend to persist in many patients, some being or becoming refractory over time. In this review, based on recent experimental data on MG or based on results from clinical trials for other autoimmune diseases, we explore new potential therapeutic approaches for MG patients, going from non-specific approaches with the use of stem cells with their anti-inflammatory and immunosuppressive properties to targeted therapies using monoclonal antibodies specific for cell-surface antigens or circulating molecules.
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Affiliation(s)
- Anthony Behin
- APHP, Centre de Référence des Maladies Neuromusculaires Nord/Est/Ile-de-France, Institut de Myologie, GH Pitié-Salpêtrière, Paris, France.,AIM, Institut de Myologie, Paris, France
| | - Rozen Le Panse
- INSERM U974, Paris, France.,UPMC Sorbonne Université, Paris, France.,AIM, Institut de Myologie, Paris, France
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404
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Abstract
Autoimmune myasthenia gravis (MG) is a neuromuscular junction disorder marked clinically by fatigable muscle weakness and serologically by the presence of autoantibodies against acetylcholine receptors (AChRs), muscle-specific kinase (MuSK), or lipoprotein-related protein 4 (LPR4). Over the past few decades, the mortality of patients with MG has seen a dramatic decline secondary to evolving interventions in critical care and medical management. In the past 2 to 3 years, there have been several changes in standard of care for the treatment of MG. These changes include confirmation of the benefit of thymectomy versus medical management alone in AChR patients and a new US Food and Drug Administration-approved medication for refractory MG. There are also several exciting new prospective drugs in the pipeline, which are in different stages of clinical trial testing.
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Affiliation(s)
- Allison Jordan
- Department of Neurology, The Ohio State Wexner Medical Center, Columbus, Ohio, USA
| | - Miriam Freimer
- Department of Neurology, The Ohio State Wexner Medical Center, Columbus, Ohio, USA
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405
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Harris CL, Pouw RB, Kavanagh D, Sun R, Ricklin D. Developments in anti-complement therapy; from disease to clinical trial. Mol Immunol 2018; 102:89-119. [PMID: 30121124 DOI: 10.1016/j.molimm.2018.06.008] [Citation(s) in RCA: 55] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Revised: 06/04/2018] [Accepted: 06/06/2018] [Indexed: 02/06/2023]
Abstract
The complement system is well known for its role in innate immunity and in maintenance of tissue homeostasis, providing a first line of defence against infection and playing a key role in flagging apoptotic cells and debris for disposal. Unfortunately complement also contributes to pathogenesis of a number of diseases; in some cases driving pathology, and in others amplifying or exacerbating the inflammatory and damaging impact of non-complement disease triggers. The role of complement in pathogenesis of an expanding number of diseases has driven industry and academia alike to develop an impressive arsenal of anti-complement drugs which target different proteins and functions of the complement cascade. Evidence from genetic and biochemical analyses, combined with improved identification of complement biomarkers and supportive data from sophisticated animal models of disease, has driven a drug development landscape in which the indications selected for clinical trial cluster in three 'target' tissues: the kidney, eye and vasculature. While the disease triggers may differ, complement activation and amplification is a common feature in many diseases which affect these three tissues. An abundance of drugs are in clinical development, some show favourable progression whereas others experience significant challenges. However, these hurdles in themselves drive an ever-evolving portfolio of 'next-generation' drugs with improved pharmacokinetic and pharmacodynamics properties. In this review we discuss the indications which are in the drug development 'spotlight' and review the relevant indication validation criteria. We present current progress in clinical trials, highlighting successes and difficulties, and look forward to approval of a wide selection of drugs for use in man which give clinicians choice in mechanistic target, modality and route of delivery.
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Affiliation(s)
- Claire L Harris
- Complement Therapeutics Research Group, Institute of Cellular Medicine, Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK; National Renal Complement Therapeutics Centre, Building 26, Royal Victoria Infirmary, Queen Victoria Road, Newcastle upon Tyne, NE1 4LP, UK.
| | - Richard B Pouw
- Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, CH-4056, Basel, Switzerland
| | - David Kavanagh
- Complement Therapeutics Research Group, Institute of Cellular Medicine, Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK; National Renal Complement Therapeutics Centre, Building 26, Royal Victoria Infirmary, Queen Victoria Road, Newcastle upon Tyne, NE1 4LP, UK
| | - Ruyue Sun
- Complement Therapeutics Research Group, Institute of Cellular Medicine, Medical School, Newcastle University, Framlington Place, Newcastle upon Tyne, NE2 4HH, UK
| | - Daniel Ricklin
- Department of Pharmaceutical Sciences, University of Basel, Klingelbergstrasse 50, CH-4056, Basel, Switzerland.
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406
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Macpherson A, Liu X, Dedi N, Kennedy J, Carrington B, Durrant O, Heywood S, van den Elsen J, Lawson ADG. The rational design of affinity-attenuated OmCI for the purification of complement C5. J Biol Chem 2018; 293:14112-14121. [PMID: 30030376 PMCID: PMC6130949 DOI: 10.1074/jbc.ra118.004043] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 07/03/2018] [Indexed: 12/04/2022] Open
Abstract
Complement component C5 is the target of the mAb eculizumab and is the focus of a sustained drug discovery effort to prevent complement-induced inflammation in a range of autoimmune diseases. The immune evasion protein OmCI binds to and potently inactivates C5; this tight-binding interaction can be exploited to affinity-purify C5 protein from serum, offering a vastly simplified protocol compared with existing methods. However, breaking the high-affinity interaction requires conditions that risk denaturing or activating C5. We performed structure-guided in silico mutagenesis to identify prospective OmCI residues that contribute significantly to the binding affinity. We tested our predictions in vitro, using site-directed mutagenesis, and characterized mutants using a range of biophysical techniques, as well as functional assays. Our biophysical analyses suggest that the C5–OmCI interaction is complex with potential for multiple binding modes. We present single mutations that lower the affinity of OmCI for C5 and combinations of mutations that significantly decrease or entirely abrogate formation of the complex. The affinity-attenuated forms of OmCI are suitable for affinity purification and allow elution under mild conditions that are nondenaturing or activating to C5. We present the rational design, biophysical characterization, and experimental validation of affinity-reduced forms of OmCI as tool reagents to enable the affinity purification of C5.
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Affiliation(s)
- Alex Macpherson
- From the UCB-Celltech, Slough SL1 3WE, United Kingdom and .,the Department of Biology and Biochemistry, University of Bath, Bath BA2 7AX, United Kingdom
| | - Xiaofeng Liu
- From the UCB-Celltech, Slough SL1 3WE, United Kingdom and
| | - Neesha Dedi
- From the UCB-Celltech, Slough SL1 3WE, United Kingdom and
| | | | | | - Oliver Durrant
- From the UCB-Celltech, Slough SL1 3WE, United Kingdom and
| | - Sam Heywood
- From the UCB-Celltech, Slough SL1 3WE, United Kingdom and
| | - Jean van den Elsen
- the Department of Biology and Biochemistry, University of Bath, Bath BA2 7AX, United Kingdom
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407
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Abstract
Myasthenia gravis is a relatively common neuromuscular disorder, with ocular myasthenia gravis being a subset defined as myasthenia gravis limited to the orbicularis, levator, and extraocular muscles. Patients with ocular myasthenia gravis can have disabling diplopia or functional blindness from ptosis and in most cases treatment is required. Like generalized myasthenia gravis, there are a variety of treatments available that include pyridostigmine, immunosuppression, intravenous immunoglobulin, plasmapheresis, thymectomy, lid crutches, ptosis surgery, and extraocular muscle surgery. Unfortunately, there is limited data on the use of individual treatments in ocular myasthenia gravis and no data comparing treatments. Using a combination of available data on treatment of generalized myasthenia gravis, data on treatment of ocular myasthenia gravis, best practices, and clinical experience we will provide a rational framework for treatment of ocular myasthenia gravis.
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Affiliation(s)
- Wayne T Cornblath
- Departments of Ophthalmology & Visual Sciences and Neurology, W.K. Kellogg Eye Center, University of Michigan, MI
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408
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Wang S, Breskovska I, Gandhy S, Punga AR, Guptill JT, Kaminski HJ. Advances in autoimmune myasthenia gravis management. Expert Rev Neurother 2018; 18:573-588. [PMID: 29932785 PMCID: PMC6289049 DOI: 10.1080/14737175.2018.1491310] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
INTRODUCTION Myasthenia gravis (MG) is an autoimmune neuromuscular disorder with no cure and conventional treatments limited by significant adverse effects and variable benefit. In the last decade, therapeutic development has expanded based on improved understanding of autoimmunity and financial incentives for drug development in rare disease. Clinical subtypes exist based on age, gender, thymic pathology, autoantibody profile, and other poorly defined factors, such as genetics, complicate development of specific therapies. Areas covered: Clinical presentation and pathology vary considerably among patients with some having weakness limited to the ocular muscles and others having profound generalized weakness leading to respiratory insufficiency. MG is an antibody-mediated disorder dependent on autoreactive B cells which require T-cell support. Treatments focus on elimination of circulating autoantibodies or inhibition of effector mechanisms by a broad spectrum of approaches from plasmapheresis to B-cell elimination to complement inhibition. Expert commentary: Standard therapies and those under development are disease modifying and not curative. As a rare disease, clinical trials are challenged in patient recruitment. The great interest in development of treatments specific for MG is welcome, but decisions will need to be made to focus on those that offer significant benefits to patients.
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Affiliation(s)
- Shuhui Wang
- Department of Neurology, George Washington University, Washington DC 20008
| | - Iva Breskovska
- Department of Neurology, George Washington University, Washington DC 20008
| | - Shreya Gandhy
- Department of Neurology, George Washington University, Washington DC 20008
| | - Anna Rostedt Punga
- Department of Neuroscience, Clinical Neurophysiology, Uppsala University, Uppsala, Sweden
| | - Jeffery T. Guptill
- Department of Neurology, Duke University Medical Center, Durham, North Carolina, USA
| | - Henry J. Kaminski
- Department of Neurology, George Washington University, Washington DC 20008
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409
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Modrego PJ. Myasthenia gravis: the unmet needs of a paradigmatic autoimmune disease. Neurodegener Dis Manag 2018; 8:137-139. [PMID: 29943694 DOI: 10.2217/nmt-2018-0014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Affiliation(s)
- Pedro J Modrego
- Department of Neurology, Hospital Miguel Servet, Isabel la católica 1-3. Zaragoza -50009, Spain
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410
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Landon-Cardinal O, Friedman D, Guiguet M, Laforêt P, Heming N, Salort-Campana E, Jouen F, Allenbach Y, Boyer O, Chatenoud L, Eymard B, Sharshar T, Benveniste O. Efficacy of Rituximab in Refractory Generalized anti-AChR Myasthenia Gravis. J Neuromuscul Dis 2018; 5:241-249. [DOI: 10.3233/jnd-180300] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Océane Landon-Cardinal
- AP-HP, Hôpital Pitié-Salpêtrière, Department of Internal Medicine and ClinicalImmunology, Inflammation-Immunopathology-Biotherapy Department (I2B), East Paris Neuromuscular Diseases Reference Center, Inserm U974, Sorbonne Université, Paris 6, Paris, France
| | - Diane Friedman
- Department of IntensiveCare, Raymond Poincare University Hospital, Garches, France
| | - Marguerite Guiguet
- Sorbonne Université, UPMC UnivParis 06, INSERM, Institut Pierre Louis d’Epidemiologie et de Santé Publique (IPLESP UMRS 1136), F75013, Paris, France
| | - Pascal Laforêt
- AP-HP, Hôpital Pitié-Salpêtrière, Department of Neurology, EastParis Neuromuscular Diseases Reference Center, Université Pierre et Marie Curie, Paris 6, Paris, France
| | - Nicholas Heming
- Department of IntensiveCare, Raymond Poincare University Hospital, Garches, France
| | | | - Fabienne Jouen
- Rouen University Hospital, Department of Immunology, Inserm U905, NormandieUniv, IRIB, Rouen, France
| | - Yves Allenbach
- AP-HP, Hôpital Pitié-Salpêtrière, Department of Internal Medicine and ClinicalImmunology, Inflammation-Immunopathology-Biotherapy Department (I2B), East Paris Neuromuscular Diseases Reference Center, Inserm U974, Sorbonne Université, Paris 6, Paris, France
| | - Olivier Boyer
- Rouen University Hospital, Department of Immunology, Inserm U905, NormandieUniv, IRIB, Rouen, France
| | - Lucienne Chatenoud
- Université Paris Descartes, Sorbonne Paris Cité, Paris, France, and INSERM U1151, CNRS UMR 8253, INEM Hôpital Necker-Enfants Malades, Paris, France
| | - Bruno Eymard
- AP-HP, Hôpital Pitié-Salpêtrière, Department of Neurology, EastParis Neuromuscular Diseases Reference Center, Université Pierre et Marie Curie, Paris 6, Paris, France
| | - Tarek Sharshar
- Department of IntensiveCare, Raymond Poincare University Hospital, Garches, France
| | - Olivier Benveniste
- AP-HP, Hôpital Pitié-Salpêtrière, Department of Internal Medicine and ClinicalImmunology, Inflammation-Immunopathology-Biotherapy Department (I2B), East Paris Neuromuscular Diseases Reference Center, Inserm U974, Sorbonne Université, Paris 6, Paris, France
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411
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Vissing J, O'Brien F, Wang JJ, Howard JF. Correlation between myasthenia gravis-activities of daily living (MG-ADL) and quantitative myasthenia gravis (QMG) assessments of anti-acetylcholine receptor antibody-positive refractory generalized myasthenia gravis in the phase 3 regain study. Muscle Nerve 2018; 58:E21-E22. [PMID: 29684239 DOI: 10.1002/mus.26152] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Revised: 04/17/2018] [Accepted: 04/20/2018] [Indexed: 11/07/2022]
Affiliation(s)
- John Vissing
- Copenhagen Neuromuscular Center, Department of Neurology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - Fanny O'Brien
- Alexion Pharmaceuticals, New Haven, Connecticut, USA
| | | | - James F Howard
- Department of Neurology, University of North Carolina, Chapel Hill, North Carolina, USA
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412
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Tong O, Delfiner L, Herskovitz S. Pain, Headache, and Other Non-motor Symptoms in Myasthenia Gravis. Curr Pain Headache Rep 2018; 22:39. [DOI: 10.1007/s11916-018-0687-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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413
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Dimachkie MM, Barohn RJ. Fifty Key Publications on Myasthenia Gravis and Related Disorders. Neurol Clin 2018; 36:xiii-xvii. [PMID: 29655457 DOI: 10.1016/j.ncl.2018.03.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Mazen M Dimachkie
- Professor & Director, Neuromuscular Division, Executive Vice Chairman & Vice Chairman for Research Programs Department of Neurology, Associate Director, Institute for Neurological Discoveries, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 2012, Kansas City, KS 66160, USA.
| | - Richard J Barohn
- Gertrude and Dewey Ziegler Professor of Neurology, University Distinguished Professor Vice Chancellor for Research, President of the Research Institute, Director, Frontiers: University of Kansas Clinical, & Translational Science Institute, University of Kansas Medical Center, 3901 Rainbow Boulevard, Mail Stop 2012, Kansas City, KS 66160, USA.
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414
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Distinct representation of muscle weakness in QMG and MG-ADL – Authors' reply. Lancet Neurol 2018; 17:205-206. [DOI: 10.1016/s1474-4422(18)30036-x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Revised: 01/24/2018] [Accepted: 01/24/2018] [Indexed: 11/21/2022]
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415
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Engel-Nitz NM, Boscoe A, Wolbeck R, Johnson J, Silvestri NJ. Burden of illness in patients with treatment refractory myasthenia gravis. Muscle Nerve 2018; 58:99-105. [PMID: 29486521 DOI: 10.1002/mus.26114] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Revised: 02/23/2018] [Accepted: 02/25/2018] [Indexed: 11/06/2022]
Abstract
INTRODUCTION This study assessed the clinical burden of refractory myasthenia gravis (MG), relative to nonrefractory MG. METHODS Rates of myasthenic crises, exacerbations, inpatient hospitalizations, and emergency room (ER) visits over a 1-year period were measured for 403 refractory, 3,811 nonrefractory, and 403 non-MG control patients from two administrative health plan databases. RESULTS Compared with nonrefractory patients, a significantly greater percentage of refractory patients had at least one myasthenic crisis (21.3% vs. 6.1%; P < 0.001) and at least one exacerbation (71.2% vs. 32.4%; P < 0.001) over a 1-year period. Refractory patients were also significantly more likely to be hospitalized and/or have an ER visit than nonrefractory patients and non-MG controls (P < 0.001 for all). DISCUSSION Refractory MG patients have significantly greater clinical burden and are more likely to utilize intensive healthcare resources than nonrefractory patients. Furthermore, refractory patients may be at greater risk of crises throughout the disease course than previous studies have suggested. Muscle Nerve, 2018.
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Affiliation(s)
- Nicole M Engel-Nitz
- Health Economics and Outcomes Research, Optum, 11000 Optum Circle, Eden Prairie, Minnesota, USA, 55344
| | - Audra Boscoe
- Alexion Pharmaceuticals, Lexington, Massachusetts, USA
| | - Ryan Wolbeck
- Health Economics and Outcomes Research, Optum, 11000 Optum Circle, Eden Prairie, Minnesota, USA, 55344
| | - Jonathan Johnson
- Health Economics and Outcomes Research, Optum, 11000 Optum Circle, Eden Prairie, Minnesota, USA, 55344
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416
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Mantegazza R, Antozzi C. When myasthenia gravis is deemed refractory: clinical signposts and treatment strategies. Ther Adv Neurol Disord 2018; 11:1756285617749134. [PMID: 29403543 PMCID: PMC5791553 DOI: 10.1177/1756285617749134] [Citation(s) in RCA: 114] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Accepted: 11/21/2017] [Indexed: 01/03/2023] Open
Abstract
The prognosis for patients with myasthenia gravis (MG) has improved significantly over the past half century, including substantial reductions in mortality and morbidity. However, approximately 10% of patients fails to respond adequately to current therapies and are considered treatment refractory, or treatment intolerant, and up to 80% have disease that fails to achieve complete stable remission. Although patients with autoantibodies to muscle-specific tyrosine kinase (anti-MuSK positive) are more likely to become treatment refractory than those with autoantibodies to the acetylcholine receptor (anti-AChR positive), each of these serotypes is substantially represented in the refractory MG population. Other risk factors for becoming treatment refractory include history of thymoma or thymectomy and female sex. A modified treatment algorithm for MG is proposed: patients who have disease that fails to respond to the stepwise approach to therapy, are treatment intolerant, or who require chronic rescue measures despite ongoing therapy, should be considered treatment refractory and emerging therapies should be considered. Three emerging monoclonal antibody-based therapies are discussed: the anti-B-cell agent rituximab; the terminal complement activation inhibitor eculizumab; and belimumab, which targets B-cell activating factor. Increased understanding of molecular pathophysiology and accurate antibody subtyping in MG should lead to the use of new therapeutic agents and successful management of treatment-refractory patients.
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Affiliation(s)
- Renato Mantegazza
- Department of Neuroimmunology and Neuromuscular Diseases, Fondazione Istituto Neurologico Carlo Besta, Via Celoria, 11, 20133 Milan, Italy
| | - Carlo Antozzi
- Department of Neuroimmunology and Neuromuscular Diseases, Fondazione Istituto Neurologico Carlo Besta, Milan, Italy
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417
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Howard JF. Myasthenia gravis: the role of complement at the neuromuscular junction. Ann N Y Acad Sci 2017; 1412:113-128. [PMID: 29266249 DOI: 10.1111/nyas.13522] [Citation(s) in RCA: 105] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 09/12/2017] [Accepted: 09/13/2017] [Indexed: 12/11/2022]
Abstract
Generalized myasthenia gravis (gMG) is a rare autoimmune disorder characterized by skeletal muscle weakness caused by disrupted neurotransmission at the neuromuscular junction (NMJ). Approximately 74-88% of patients with gMG have acetylcholine receptor (AChR) autoantibodies. Complement plays an important role in innate and antibody-mediated immunity, and activation and amplification of complement results in the formation of membrane attack complexes (MACs), lipophilic proteins that damage cell membranes. The role of complement in gMG has been demonstrated in animal models and patients. Studies in animals lacking specific complement proteins have confirmed that MAC formation is required to induce experimental autoimmune MG (EAMG) and NMJ damage. Complement inhibition in EAMG models can prevent disease induction and reverse its progression. Patients with anti-AChR+ MG have autoantibodies and MACs present at NMJs. Damaged NMJs are associated with more severe disease, fewer AChRs, and MACs in synaptic debris. Current MG therapies do not target complement directly. Eculizumab is a humanized monoclonal antibody that inhibits cleavage of complement protein C5, preventing MAC formation. Eculizumab treatment improved symptoms compared with placebo in a phase II study in patients with refractory gMG. Direct complement inhibition could preserve NMJ physiology and muscle function in patients with anti-AChR+ gMG.
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Affiliation(s)
- James F Howard
- Department of Neurology, University of North Carolina, Chapel Hill, North Carolina
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418
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Eculizumab: a treatment option for myasthenia gravis? Lancet Neurol 2017; 16:947-948. [DOI: 10.1016/s1474-4422(17)30363-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 10/06/2017] [Accepted: 10/10/2017] [Indexed: 11/23/2022]
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