Resistant myasthenia gravis and rituximab: A monocentric retrospective study of 28 patients

Rituximab alone is as effective as associated with steroids on naive patients with generalized myasthenia gravis

INTRODUCTION

Rituximab (RTX) has been proven effective in managing refractory generalized myasthenia gravis (MG), and its use is increasing worldwide. MG stabilization may initially require oral corticosteroid (CS) therapy, but its long-term side effects require the shortest duration of treatment. We studied the clinical effectiveness and usefulness of corticosteroids associated with RTX compared to RTX alone on MG remission.

METHODS

In a monocentric retrospective cohort in the Nice University Hospital, we compared naïve MG patients treated with RTX as first-line therapy alone (G1) or associated with CS (G2). After the RTX induction, we evaluated efficacy with the Osserman score (OS) and the requirement for any rescue therapy (IVIg or plasmapheresis).

RESULTS

Sixty-eight patients were treated with RTX, of which 19 (27.94%) benefited from an association with at least 0.5 mg/kg of corticosteroids. RTX-CS patients were more severe than RTX alone (OS for G1: 74.1 and G2: 64.94, p = 0.044). However, OS at 3 (83.44 and 83.12, p = 0.993), 6 (88.69 and 86.36, p = 0.545), 9 (82.91 and 85.73, p = 0.563), and 12 months (86.6 and 88.69, p = 0.761) from the treatment induction were similar. Rescue therapy following RTX induction was significantly higher for the RTX-CS (20.41% and 47.37%, p = 0.037). Regarding safety, adverse event rates were similar in the two groups (0% and 14.29%, p = 0.178).

CONCLUSION

We suggest that RTX alone is as effective as RTX-CS in MG patients, indicating that avoiding steroids could reduce side effects, decrease rescue therapies, and not affect MG outcomes.

Drug-Induced Progressive Multifocal Leukoencephalopathy (PML): A Systematic Review and Meta-Analysis

INTRODUCTION

Progressive multifocal leukoencephalopathy (PML) was first described among patients affected by hematological or solid tumors. Following the human immunodeficiency virus (HIV) epidemic, people living with HIV have represented most cases for more than a decade. With the diffusion of highly active antiretroviral therapy, this group progressively decreased in favor of patients undergoing treatment with targeted therapy/immunomodulators. In this systematic review and meta-analysis, the objective was to assess which drugs are most frequently related to PML development, and report the incidence of drug-induced PML through a meta-analytic approach.

METHODS

The electronic databases MEDLINE, EMBASE, ClinicalTrials.gov, Web of Science and the Canadian Agency for Drugs and Technologies in Health Database (CADTH) were searched up to May 10, 2022. Articles that reported the risk of PML development after treatment with immunomodulatory drugs, including patients of both sexes under the age of 80 years, affected by any pathology except HIV, primary immunodeficiencies or malignancies, were included in the review. The incidence of drug-induced PML was calculated based on PML cases and total number of patients observed per 100 persons and the observation time. Random-effect metanalyses were conducted for each drug reporting pooled incidence with 95% confidence intervals (CI) and median (interquartile range [IQR]) of the observation time. Heterogeneity was measured by I2 statistics. Publication bias was examined through funnel plots and Egger's test.

RESULTS

A total of 103 studies were included in the systematic review. In our analysis, we found no includible study reporting cases of PML during the course of treatment with ocrelizumab, vedolizumab, abrilumab, ontamalimab, teriflunomide, daclizumab, inebilizumab, basiliximab, tacrolimus, belimumab, infliximab, firategrast, disulone, azathioprine or danazole. Dalfampridine, glatiramer acetate, dimethyl fumarate and fingolimod show a relatively safe profile, although some cases of PML have been reported. The meta-analysis showed an incidence of PML cases among patients undergoing rituximab treatment for multiple sclerosis (MS) of 0.01 cases/100 persons (95% CI - 0.08 to 0.09; I2 = 20.4%; p = 0.25) for a median observation period of 23.5 months (IQR 22.1-42.1). Treatment of MS with natalizumab carried a PML risk of 0.33 cases/100 persons (95% CI 0.29-0.37; I2 = 50%; p = 0.003) for a median observation period of 44.1 months (IQR 28.4-60) and a mean number of doses of 36.3 (standard deviation [SD] ± 20.7). When comparing data about patients treated with standard interval dosing (SID) and extended interval dosing (EID), the latter appears to carry a smaller risk of PML, that is, 0.08 cases/100 persons (95% CI 0.0-0.15) for EID versus 0.3 cases/100 persons (95% CI 0.25-0.34) for SID.

CONCLUSIONS

A higher risk of drug-related PML in patients whose immune system is not additionally depressed by means of neoplasms, HIV or concomitant medications is found in the neurological field. This risk is higher in MS treatment, and specifically during long-term natalizumab therapy. While this drug is still routinely prescribed in this field, considering the efficacy in reducing MS relapses, in other areas it could play a smaller role, and be gradually replaced by other safer and more recently approved agents.

Rituximab as a sole steroid-sparing agent in generalized myasthenia gravis: Long-term outcomes

BACKGROUND

Rituximab, a B-cell depleting monoclonal antibody, represents an option for the treatment of refractory myasthenia gravis (MG). Its use is more established in muscle-specific tyrosine kinase positive (MuSK +) patients, while its role in managing acetylcholine receptor positive (AChR +), or double seronegative (DSN) patients, remains less clear. This study evaluates the long-term effectiveness and safety of rituximab in MG of various serotypes.

METHODS

We conducted an open-label study of MG patients receiving rituximab. Adults with generalized refractory MG, either anti-AChR + or DSN, and anti-MuSK + , refractory or not, who had follow-up > 12 months were selected. Change in quantitative myasthenia gravis (QMG) score at last follow-up, compared with baseline was a primary outcome, as well as factors affecting response to treatment. Secondary outcomes included, long-term safety, the steroid-sparing effect and relapse rates post-rituximab.

RESULTS

Thirty patients (16 anti-AChR + , 6 anti-MuSK + , 8 DSN) followed for a mean of 33.3 months were included. Mean scores pre-rituximab compared to last follow-up significantly decreased (p < 0.001), from 11 ± 4.1 to 4.3 ± 3.8, and from 1.9 to 0.3 regarding QMG and relapse rate per patient/year, respectively, while in 93.1% a daily steroid dose ≤ 10 mg was achieved. Antibody status was the only factor independently influencing several endpoints. Throughout the study period no crises or deaths occurred.

CONCLUSION

The present study supports that rituximab is an effective and well tolerated treatment for refractory anti-AChR + and DSN MG patients, while anti-MuSK + remains the group experiencing the greater benefits.

Promising efficacy of Low-Dose rituximab in Muscle specific kinase antibody positive Myasthenia Gravis

AIMS

The study aims to evaluate the efficacy of low dose rituximab (RTX) in patients with muscle-specific kinase antibody positive myasthenia gravis (MuSK-MG).

METHODS

This is a single-center, retrospective study. A total of 10 patients with MuSK-MG were admitted to the Department of Neurology, First Hospital, Shanxi Medical University, between April 2021 to April 2023. Of them, 9 patients had been treated with low dose RTX (500 mg every 6 month) and recruited in this study. The clinical information, including the severity before and after RTX treatment, were collected from the medical records. Clinical effectiveness was assessed by Myasthenia Gravis Foundation of America (MGFA)-postintervention status (PIS), MG-related activities of daily living (MG-ADL), Quantitative Myasthenia Gravis (QMG) scores, Myasthenia Gravis Quality of Life 15-item revised (MG-QOL15r), dosage of steroid at the end of follow up.

RESULTS

All nine patients showed clinical improvement at the final follow-up after low-dose RTX treatment. The mean dose of prednisolone decreased significantly from 50 mg at baseline to 18.33 mg at the last follow-up (z = -3.417, p = 0.001). The administration of low-dose RTX treatment led to significant improvements in ADL levels (Z = -2.675, P < 0.01), QMG score levels (Z = -2.371, P < 0.05) and QOL-15r levels (Z = -2.547, P < 0.01) at last visit.

CONCLUSION

Low-dose RTX is effective for treating MuSK-MG patients. Longer-term follow-up and larger-scale studies are needed to provide further evidence.

Rituximab treatment in myasthenia gravis

Myasthenia gravis (MG) is a chronic autoimmune disease mediated by antibodies against post-synaptic proteins of the neuromuscular junction. Up to 10%-30% of patients are refractory to conventional treatments. For these patients, rituximab has been used off-label in the recent decades. Rituximab is a monoclonal antibody against the CD20 protein that leads to B cell depletion and to the synthesis of new antibody-secreting plasma cells. Although rituximab was created to treat B-cell lymphoma, its use has widely increased to treat autoimmune diseases. In MG, the benefit of rituximab treatment in MuSK-positive patients seems clear, but a high variability in the results of observational studies and even clinical trials has been reported for AChR-positive patients. Moreover, few evidence has been reported in seronegative MG and juvenile MG and some questions about regimen of administration or monitoring strategies, remains open. In this review, we intend to revise the available literature on this topic and resume the current evidence of effectiveness of Rituximab in MG, with special attention to results on every MG subtype, as well as the administration protocols, monitoring strategies and safety profile of the drug.

Long-Term Efficacy and Safety of Low-Dose Rituximab in Patients with Refractory Myasthenia Gravis

INTRODUCTION

Rituximab is a monoclonal chimeric antibody against CD20+ B cells. We aimed to assess the long-term efficacy and safety of CD20+ B cell-guided treatment with low-dose rituximab in refractory myasthenia gravis patients.

METHODS

Patients with refractory myasthenia gravis treated with rituximab for more than 2 years were included. Rituximab was administered when CD20+ B cells were greater than 1%. We analysed the efficacy of rituximab, treatment interval, side effects, prognosis, and treatment course.

RESULTS

A total of 22 patients were included. All patients received 2-12 doses of rituximab, and the median follow-up time was 48.5 months. The scores of the Myasthenia Gravis Activities of Daily Living and Myasthenia Gravis Composite were significantly lower than those at baseline (p < 0.05). MGFA-PIS was significantly improved in 21 (95.45%) patients and 14 (63.64%) patients have reached MGFA-PIS minimal manifestations. The average daily dose of prednisone and pyridostigmine bromide and the proportion of immunosuppressants were significantly lower (p < 0.05). Seven patients suffered from 14 worsenings. Eight patients terminated rituximab due to good efficacy. Most patients tolerated rituximab well, although 1 patient had opportunistic infection and hypogammaglobulinemia, 1 patient had an intracranial mass.

CONCLUSION

Long-term CD20+ B-cell-guided low-dose rituximab showed good efficacy and tolerance in patients with refractory myasthenia gravis.

Immunotherapies in MuSK-positive Myasthenia Gravis; an IgG4 antibody-mediated disease

Muscle-specific kinase (MuSK) Myasthenia Gravis (MG) represents a prototypical antibody-mediated disease characterized by predominantly focal muscle weakness (neck, facial, and bulbar muscles) and fatigability. The pathogenic antibodies mostly belong to the immunoglobulin subclass (Ig)G4, a feature which attributes them their specific properties and pathogenic profile. On the other hand, acetylcholine receptor (AChR) MG, the most prevalent form of MG, is characterized by immunoglobulin (Ig)G1 and IgG3 antibodies to the AChR. IgG4 class autoantibodies are impotent to fix complement and only weakly bind Fc-receptors expressed on immune cells and exert their pathogenicity via interfering with the interaction between their targets and binding partners (e.g. between MuSK and LRP4). Cardinal differences between AChR and MuSK-MG are the thymus involvement (not prominent in MuSK-MG), the distinct HLA alleles, and core immunopathological patterns of pathology in neuromuscular junction, structure, and function. In MuSK-MG, classical treatment options are usually less effective (e.g. IVIG) with the need for prolonged and high doses of steroids difficult to be tapered to control symptoms. Exceptional clinical response to plasmapheresis and rituximab has been particularly observed in these patients. Reduction of antibody titers follows the clinical efficacy of anti-CD20 therapies, a feature implying the role of short-lived plasma cells (SLPB) in autoantibody production. Novel therapeutic monoclonal against B cells at different stages of their maturation (like plasmablasts), or against molecules involved in B cell activation, represent promising therapeutic targets. A revolution in autoantibody-mediated diseases is pharmacological interference with the neonatal Fc receptor, leading to a rapid reduction of circulating IgGs (including autoantibodies), an approach already suitable for AChR-MG and promising for MuSK-MG. New precision medicine approaches involve Chimeric autoantibody receptor T (CAAR-T) cells that are engineered to target antigen-specific B cells in MuSK-MG and represent a milestone in the development of targeted immunotherapies. This review aims to provide a detailed update on the pathomechanisms involved in MuSK-MG (cellular and humoral aberrations), fostering the understanding of the latest indications regarding the efficacy of different treatment strategies.

Novel Immunotherapies for Myasthenia Gravis

Myasthenia gravis (MG), a prototype autoimmune neurological disease, had its therapy centred on corticosteroids, non-steroidal broad-spectrum immunotherapy and cholinesterase inhibitors for several decades. Treatment-refractory MG and long-term toxicities of the medications have been major concerns with the conventional therapies. Advances in the immunology and pathogenesis of MG have ushered in an era of newer therapies which are more specific and efficacious. Complement inhibitors and neonatal Fc receptor blockers target disease-specific pathogenic mechanisms linked to myasthenia and have proven their efficacy in pivotal clinical studies. B cell-depleting agents, specifically rituximab, have also emerged as useful for the treatment of severe MG. Many more biologicals are in the pipeline and in diverse stages of development. This review discusses the evidence for the novel therapies and the specific issues related to their clinical use.

Long-Term Remission With Low-Dose Rituximab in Myasthenia Gravis: A Retrospective Study

OBJETIVE

Rituximab (RTX) is a therapeutic option, for patients with myasthenia gravis (MG) not responding to conventional immunosuppressive treatment. In this cohort, we evaluated long-term efficacy of RTX in the treatment of refractory generalized MG.

METHODS

A retrospective study was performed in adult patients with refractory generalized MG and at least 24 months of follow-up, between January/2015 and October/2021. The Myasthenia Gravis Status and Treatment Intensity Score was used to assess outcomes, and CD19/CD20+ B-cell counts were monitored.

RESULTS

Sixteen patients with MG (8 antiacetylcholine receptor+ and 8 muscle-specific antikinase+; mean age 45.5 ± 16.2 years) treated with low-dose RTX protocols were included. CD19/CD20 levels remained undetectable 12 months after induction, and no new relapses were observed during follow-up.

CONCLUSIONS

Low-dose RTX infusions were sufficient to achieve undetectable CD19/20 cell counts and sustained clinical remission. In low and middle-income countries, the impact of low-dose RTX therapy represents a paradigm shift in decision-making for long-term treatment.

Rituximab in Myasthenia Gravis- Experience from a Low- and Middle-Income Country (LMIC) Setting

BACKGROUND

Myasthenia gravis (MG) is an immune-mediated disorder of the neuromuscular junction. About 10% are refractory to immunosuppressive therapy.

AIMS

To analyze the response of patients with generalized MG to rituximab.

METHODS AND MATERIALS

A retrospective review of patients with MG who received rituximab was carried out (n = 13, M:F = 6:7, mean age: 44.84 ± 15.73 years). Myasthenia Gravis Foundation of America (MGFA), MGFA post-intervention status (MGFA-PIS), and Myasthenia Gravis Status and Treatment Intensity (MGSTI) were assessed before and after rituximab.

RESULTS

The duration of MG was 104.07 ± 92.25 months. Before rituximab, the MGFA was IIA/IIB/IIIA/IIIB/IVB/V in 1/1/2/6/2/1 patients and MGSTI was four in eight patients and six in three patients. The mean duration of follow up was 20.92 ± 14.06 months (range, 4 to 42 months). Dose reduction or discontinuation of cholinesterase inhibitors could be achieved 12 patients. Complete stable remission (CSR) and pharmacologic remission (PR) were achieved in one and four patients respectively and five patients had minimal manifestations. Most patients attained level 0, 1 or 2 MGSTI at last follow up. No rituximab infusion-related adverse events were noted. Three patients had exacerbation of MG between one to five weeks after rituximab administration. Three patients died, one each due to a cardiac event unrelated to MG or treatment, complications related to myasthenic crisis, and coronavirus disease.

CONCLUSIONS

Rituximab was effective in bringing about remission in MG and can be considered as a first-line agent. However, it has to be administered under close supervision as some patients develop exacerbation of MG akin to steroid-induced worsening.

Efficacy and Safety of Low-Dose Rituximab in Anti-MuSK Myasthenia Gravis Patients: A Retrospective Study

PURPOSE

To evaluate the efficacy and safety of low dosages of rituximab (RTX) in the treatment of MuSK-antibody-positive MG patients.

PATIENTS AND METHODS

We retrospectively analyzed the data of MuSK-antibody-positive MG patients who were treated with low dosages of RTX from January 2018 to October 2021. The long-term treatment response to RTX was assessed by Myasthenia Gravis Foundation of America (MGFA) post-interventional status (PIS), Myasthenia Gravis Status and Treatment Intensity (MGSTI), dosage of steroid, MG-related activities of daily living (MG-ADL) and myasthenic muscle score (MMS) at the end of follow-up.

RESULTS

Clinical improvement was observed in all eight patients with follow-up for 8 to 29 months after treatment. At the last visit, complete stable remission had been achieved in one patient, pharmacologic remission in three patients, minimal manifestations status in three patients and improved in one patient based on the MGFA-PIS criteria. MGSTI level 2 or better had been reached in six (75%) patients at the last visit. The steroid dosage decreased from 60 mg at baseline to 15 mg at the last follow-up (p = 0.011). The average MG-ADL score decreased from 11 (range 7 to 15) to 0 (range 0 to 3; p = 0.011), and the MMS improved from 38.5 (range 24 to 60) to 100 (range 90 to 100; p = 0.012). These differences were all statistically significant. During RTX treatment and subsequent follow-up, 1 patient reported minor post-infusion malaise.

CONCLUSION

Low-dose RTX is effective and safe for treating anti-MuSK antibody positive MG patients. A long-term response is observed after treatment. Larger prospective studies are required to provide further evidence.

Rituximab in the Management of Refractory Myasthenia Gravis and Variability of Its Efficacy in Anti-MuSK Positive and Anti-AChR Positive Myasthenia Gravis

Myasthenia gravis affects the neuromuscular junction of the skeletal muscles. It results in muscle weakness involving skeletal muscles (diaphragm, extraocular muscles) and myasthenic crisis. Treatment options for myasthenia gravis management have expanded, including azathioprine, corticosteroids, plasma exchange, and tacrolimus. Unfortunately, a few cases of myasthenia gravis don't respond to conventional treatment modalities. Monoclonal antibodies, rituximab (RTX), are novel treatments that have garnered interest as of late due to their efficacy within the patient population presented with refractory form myasthenia gravis. This review aims to showcase how RTX is an effective treatment within different forms of myasthenia gravis. A limited review was performed using databases that include PubMed and Google Scholar. The following keywords were used: "myasthenia gravis," "rituximab," "monoclonal antibody," "anti-AChR antibody," and "refractory myasthenia." The review focused on case reports, human studies, or research surveys based on the inclusion criteria of human studies involving participants more than 18 years of age and published in English literature. Out of 69 articles, 14 were duplicates, and 29 were relevant and met the inclusion criteria. The findings from the study demonstrate that patients with refractory myasthenia gravis responded well to RTX treatment. Furthermore, RTX has been shown to decrease corticosteroid dependence, induce sustained remission, and have a favorable response to anti-MuSK antibody positive myasthenia gravis compared to anti-AChR antibody positive myasthenia gravis. This literature review suggests that patients with refractory myasthenia gravis can benefit from rituximab; however, it has a variable response in different forms of myasthenia gravis.

Effectiveness and Safety of Rituximab for Refractory Myasthenia Gravis: A Systematic Review and Single-Arm Meta-Analysis

Background and Objective: Myasthenia gravis (MG) is an autoimmune neuromuscular disease. Nearly 10-30% of patients with MG are refractory to conventional therapy. Rituximab (RTX), a monoclonal antibody targeting CD20, is increasingly used in autoimmune disorders. We performed a systematic review and meta-analysis to evaluate the effectiveness and safety of RTX for refractory MG. Methods: Studies published between January 1, 2000 and January 17, 2021 were searched in PubMed, EMBASE, Cochrane Library, and ClincalTrails.gov. Primary outcomes included proportion of patients achieving minimal manifestation status (MMS) or better and quantitative MG (QMG) score change from baseline. Secondary outcomes were glucocorticoids (GC) doses change from baseline and proportion of patients discontinuing oral immunosuppressants. Results: A total of 24 studies involving 417 patients were included in the meta-analysis. An overall 64% (95% confidence interval, 49-77%) of patients achieved MMS or better. The estimated reduction of QMG score was 1.55 (95% confidence interval, 0.88-2.22). The mean reduction of GC doses was 1.46 (95% confidence interval, 1.10-1.82). The proportion of patients discontinuing oral immunosuppressants was 81% (95% confidence interval, 66-93%). Subgroup analyses showed that the proportion of patients achieving MMS or better and discontinuing oral immunosuppressants was higher in MuSK-MG group than those in AChR-MG group. Improvement was more pronounced in patients with mild to moderate MG compared to those with severe MG. Moreover, the efficacy appeared to be independent of the dose of RTX. 19.6% of patients experienced adverse events, most of which were mild to moderate. Only one patient developed progressive multifocal leukoencephalopathy. Conclusions: RTX can alleviate the symptom of weakness, decrease QMG score and reduce the doses of steroids and non-steroid immunosuppressive agents in refractory MG. It is well-tolerated with few severe adverse events. Randomized controlled trials are urgently needed to study the efficacy of RTX in treating refractory MG and to identify the characteristics of patients who might respond well to RTX.

Eculizumab in refractory generalized myasthenia gravis previously treated with rituximab: subgroup analysis of REGAIN and its extension study

INTRODUCTION/AIMS

Individuals with refractory generalized myasthenia gravis (gMG) who have a history of rituximab use and experience persistent symptoms represent a population with unmet treatment needs. The aim of this analysis was to evaluate the efficacy and safety of eculizumab in patients with refractory anti-acetylcholine receptor antibody-positive (AChR⁺ ) gMG previously treated with rituximab.

METHODS

This post hoc subgroup analysis of the phase 3 REGAIN study (NCT01997229) and its open-label extension (OLE; NCT02301624) compared baseline characteristics, safety, and response to eculizumab in participants who had previously received rituximab with those who had not. Rituximab use was not permitted within the 6 months before screening or during REGAIN/OLE.

RESULTS

Of 125 REGAIN participants, 14 had received rituximab previously (7 received placebo and 7 received eculizumab). In the previous-rituximab group, 57% had used at least four other immunosuppressants compared with 16% in the no-previous-rituximab group. Myasthenia Gravis Activities of Daily Living total scores from eculizumab baseline to week 130 of eculizumab treatment improved in both the previous-rituximab and no-previous-rituximab groups (least-squares mean -4.4, standard error of the mean [SEM] 1.0 [n = 9] and least-squares mean -4.6, SEM 0.3 [n = 67], respectively; difference = 0.2, 95% confidence interval -1.88 to 2.22). In addition, in both groups, most patients who were treated with eculizumab for 130 weeks achieved a Myasthenia Gravis Foundation of America post-intervention status of minimal manifestations (66.7% and 65.0%, respectively). The eculizumab safety profile was similar between groups and consistent with its established profile.

DISCUSSION

Eculizumab is an effective therapy for patients with refractory AChR⁺ gMG, irrespective of whether they had received rituximab treatment previously.

Evaluation of outcome measures for myasthenia gravis subgroups

INTRODUCTION

Disease evaluation and long-term follow-up of myasthenia gravis (MG) patients rely on disease-specific measures. We evaluated four widely used MG-specific assessments, and compared the response to disease change in different MG subgroups.

METHODS

We used the Cronbach's α coefficient to test reliability, Pearson correlation coefficients to test construct validity, as well as one-way ANOVA and independent-sample t-tests to access discriminant validity. Analyses of similar items between QMG and MG-ADL included paired-sample t-tests and mean score comparisons. Pearson correlation coefficients were used to describe the correlation between changes of QMG, MG-ADL, MG-QOL15r and MGC. The Wilcoxon matched-pairs signed-ranks test was performed to compare the outcomes.

RESULTS

872 MG patients were enrolled. QMG, MG-ADL, MG-QOL15r, and MGC all exhibited high reliability. All four scales displayed good discriminant validity according to the MGFA classification and MGC score. MG-ADL showed significant differences between patients grouped by age and gender, and MG-QOL15r showed significant differences between patients grouped by age. Analyses of similar items showed that MG-ADL achieved higher scores in bulbar items, whereas QMG produced higher scores in limb items. For patients in remission or minimal manifestation status, QMG exhibited significantly greater improvement than MG-QOL15r. In patients of MGFA I, II, III, and IV, QMG showed significantly greater improvement than MG-ADL.

CONCLUSIONS

Patient-reported scale is an important supplement for a given period. MG-ADL has a better response to severe disease, and MG-QOL15r is more comprehensive for patients in remission or minimal manifestation status.

Heterogeneity in myasthenia gravis: considerations for disease management

Introduction: Myasthenia gravis is a rare disease of the neuromuscular junction and a prototype of B cell-driven immunopathology. Pathogenic antibodies target post-synaptic transmembrane proteins, most commonly the nicotinic acetylcholine receptor and the muscle-specific tyrosine kinase, inducing end-plate alterations and neuromuscular transmission impairment. Several clinical subtypes are distinct on the basis of associated antibodies, age at symptom onset, thymus pathology, genetic factors, and weakness distribution. These subtypes have distinct pathogenesis that can account for different responses to treatment. Conventional therapy is based on the use of symptomatic agents, steroids, immunosuppressants and thymectomy. Of late, biologics have emerged as effective therapeutic options.Areas covered: In this review, we will discuss the management of myasthenia gravis in relation to its phenotypic and biological heterogeneity, in the light of recent advances in the disease immunopathology, new diagnostic tools, and results of clinical trialsExpert opinion: Clinical management is shaped on serological subtype, and patient age at onset, lifestyle and comorbidities, balancing therapeutic needs and safety. Although reliable biomarkers predictive of clinical and biologic outcome are still lacking, recent developments promise a more effective and safe treatment. Disease subtyping according to serological testing and immunopathology is crucial to the appropriateness of clinical management.

Rituximab in Myasthenia Gravis - Where do we stand?

Introduction: Myasthenia gravis (MG) is an antibody-mediated disease with diverse serology and clinical presentation. Currently, MG is managed by untargeted immunomodulatory agents. About 15% patients are refractory to these therapies. Several novel and targeted treatments are on the horizon. Rituximab, a monoclonal antibody, is reported to be highly effective with widespread oof-label usage in MG, particularly in patients with antibody against muscle-specific kinase or refractory disease. However, a recent trial showed negative results. Compared to conventional oral immunosuppressive therapies used in MG, Rituximab has several benefits. Regular hematological monitoring is not required though serious side effects can occur. Current status of Rituximab in MG and newer immunosuppressants is discussed.Areas explored: Biologic features, clinical effectiveness, safety profile, and newer preparations of Rituximab.Expert opinion: Rituximab provides a promising option for management of MG, particularly in patients with muscle-specific kinase antibodies or those with refractory disease. Several knowledge gaps remain due to scarcity of data from randomized controlled studies. Despite lack of regulatory approval Rituximab has found widespread usage in MG. Large, well-designed studies are needed to assess the comparative efficacy of Rituximab and its optimal regimen in MG.

Memory B Cells Predict Relapse in Rituximab-Treated Myasthenia Gravis

Myasthenia gravis can be efficiently treated with rituximab but there is no consensus regarding administration and dose schedules in this indication. No marker has yet been described to predict the clinical relapse of patients. Our objective was to identify the B cell subpopulations predicting clinical relapse in patients suffering from generalized myasthenia gravis and treated with rituximab. Clinical and biological data of 34 patients followed between 2016 and 2019 were prospectively collected every 3 months. Using multiparameter flow cytometry, we assessed the percentage in leucocytes of lymphocytes and several B cell subpopulations measured in residual disease conditions. CD19+ were also measured in non-residual disease conditions. Clinical examinations were performed by neurologists using the Osserman score. Clinical relapse occurred in 14 patients (41%). No patients required ICU or ventilatory assistance. The mean improvement of the Osserman score was 17.18 (3-45) after the first rituximab treatment (p < 0.0001). The mean delay between the first rituximab maintenance cycle and clinical relapse was 386.8 days. At the time of relapse, CD27+ increased (p = 0.0006) with AUC = 0.7654, while CD19+ did not. At a threshold of 0.01%, the sensitivity and specificity of CD19+CD27+ were 75.8% and 72.8%, respectively, and the positive and negative predictive values were 28.0% and 95.6%, respectively. The percentage of memory B cells in whole blood cells can accurately predict clinical relapse in myasthenia gravis patients treated with rituximab. This monitoring allows physicians to tailor rituximab administration and to decrease the number of infusions over time.

Efficacy and safety of different dosages of rituximab for refractory generalized AChR myasthenia gravis: A meta-analysis

BACKGROUND

Rituximab (RTX) is a mouse-human chimeric anti-CD20 monoclonal antibody and has been increasingly used for preventing relapses in myasthenia gravis (MG). However, the appropriate dose for maximizing the beneficial effects in refractory MG with acetylcholine receptor (AChR) autoantibody is a long-standing and critical debating question.

METHODS

We performed a meta-analysis to evaluate the efficacy and safety of the different doses of RTX in 260 refractory AChR-MG patients.

RESULTS

The AChR-MG patients were divided into low or routine RTX dose groups. An overall proportion of 77% (p = 0.000) AChR-MG patients demonstrated improved clinical status as indicated by the Myasthenia Gravis Foundation of America post-intervention scale (MGFA-PIS). There were 77.1% patients showed improved clinical status in lower dose of RTX group (p = 0.000) and 76.8% in routine protocol group (p = 0.000). Although we found there was no significant difference in the proportion of AChR-MG patients with improved clinical status or adverse reactions between the two groups, adverse reactions might be lower in the lower dose RTX group.

CONCLUSION

Most of refractory MG patients with anti-AChR autoantibody were well responsive and tolerated to RTX treatment. Repeated application of lower dose of RTX was effective and might be more appropriate for refractory AChR-MG patients with potential lower side effects.

Treatment of refractory myasthenia gravis by double-filtration plasmapheresis and rituximab: A case series of nine patients and literature review

INTRODUCTION

Myasthenia gravis (MG) is an autoimmune disease mediated by circulating autoantibodies (anti-AchR, anti-MuSK, etc.). More than 20% of myasthenic patients are refractory to conventional treatments (plasma exchange, IVIg, steroids, azathioprine, mycophenolate mofetil). Rituximab (B-lymphocyte-depleting anti-CD20) and apheresis (double-filtration plasmapheresis [DFPP] and immunoadsorption [IA]) are interesting therapeutic alternatives.

METHODS

This monocentric pilot study included nine refractory myasthenic patients (March 2018 to May 2020) treated by DFPP and/or IA associated with rituximab (375 mg/m² ). Clinical responses were assessed using the Myasthenia Gravis Foundation of America (MGFA) score.

RESULTS

Average age of patients was 53 ± 17 years. Gender ratio (M/F) was 3:6. The combination of apheresis and rituximab reduced median MGFA score from IV to II after 12 months of follow-up. Clinical improvement assessed by MGFA score was sustained in the long-term for all patients, during an average follow-up of 14 ± 9 months, allowing them to be self-sufficient and out sick-leave. The median number of apheresis sessions was 7 (5-30). The dose of prednisolone was reduced in two patients from 40 mg/d and 30 mg/d to 7.5 mg/d and 10 mg/d, respectively. It was stopped in a patient who was taking 30 mg/d. No infectious, bleeding, or thrombosis complications were noted.

CONCLUSION

The combination of rituximab and DFPP was effective to treat refractory MG.

International Consensus Guidance for Management of Myasthenia Gravis: 2020 Update

Objective

To update the 2016 formal consensus-based guidance for the management of myasthenia gravis (MG) based on the latest evidence in the literature.

Methods

In October 2013, the Myasthenia Gravis Foundation of America appointed a Task Force to develop treatment guidance for MG, and a panel of 15 international experts was convened. The RAND/UCLA appropriateness method was used to develop consensus recommendations pertaining to 7 treatment topics. In February 2019, the international panel was reconvened with the addition of one member to represent South America. All previous recommendations were reviewed for currency, and new consensus recommendations were developed on topics that required inclusion or updates based on the recent literature. Up to 3 rounds of anonymous e-mail votes were used to reach consensus, with modifications to recommendations between rounds based on the panel input. A simple majority vote (80% of panel members voting “yes”) was used to approve minor changes in grammar and syntax to improve clarity.

Results

The previous recommendations for thymectomy were updated. New recommendations were developed for the use of rituximab, eculizumab, and methotrexate as well as for the following topics: early immunosuppression in ocular MG and MG associated with immune checkpoint inhibitor treatment.

Conclusion

This updated formal consensus guidance of international MG experts, based on new evidence, provides recommendations to clinicians caring for patients with MG worldwide.

Patient-acceptable symptom states in myasthenia gravis

Objectives

To estimate patient-acceptable symptom state (PASS) cut points for myasthenia gravis (MG) health scales.

Methods

We conducted an electronic survey that included the Myasthenia Gravis Impairment Index (MGII), EuroQol 5-Dimension (EQ5D), and a simple PASS question. PASS-anchored thresholds were estimated for the MGII questionnaire through receiver operating characteristic curves. We used the MGII PASS cut point in a validation cohort of 257 patients to estimate PASS thresholds for other clinically relevant health scales such as the Quantitative Myasthenia Gravis Scale (QMGS), Myasthenia Gravis Activities of Daily Living (MG-ADL), Myasthenia Gravis Composite (MGC), and Myasthenia Quality of Life (MG-QoL15).

Results

One hundred twenty-four of ≈250 invited patients answered the electronic survey (49% response rate), and 80 considered their current symptom state acceptable (PASS-positive). They had lower MGII scores than PASS-negative patients (7.76 ± 9.37 vs 25.0 ± 13.7, p < 0.0001) and better EQ5D scores (0.86 ± 0.17 vs 0.69 ± 0.18, p < 0.0001). The MGII questionnaire threshold for PASS was ≤10 points. With the use of this threshold in an independent dataset of 257 patients, all patients in remission or minimal manifestation status were PASS-positive. In addition, some patients in Classes I, II, and IIIA also achieved PASS status. PASS thresholds for the QMGS, MG-ADL, MGC, and MG-QoL15 were ≤7, 2, 3, and 8 points, respectively.

Conclusions

We have estimated thresholds for commonly used myasthenia health scales reflecting patient-acceptable states in patients with MG. These thresholds indicate a global state of well being, rather than a change in scores, or being better. Therefore, PASS thresholds can be used as secondary endpoints for myasthenia research.

MuSK-Associated Myasthenia Gravis: Clinical Features and Management

Muscle-specific tyrosine kinase (MuSK) myasthenia gravis (MG) is a rare, frequently more severe, subtype of MG with different pathogenesis, and peculiar clinical features. The prevalence varies among countries and ethnic groups, affecting 5–8% of all MG patients. MuSK-MG usually has an acute onset affecting mainly the facial-bulbar muscles. The symptoms usually progress rapidly, within a few weeks. Early respiratory crises are frequent. The disease may lead to generalized muscle weakness up to muscle atrophy. The main bulbar involvement, the absence of significant thymus alterations, and the association with HLA class II DR14, DR16, and DQ5 alleles have been confirmed. Atypical onset, such as ocular involvement, lack of symptom fluctuations, acetylcholinesterase inhibitors failure, and negative results of electrophysiologic testing, if not specifically performed in the mainly involved muscle groups, makes MuSK-MG diagnosis challenging. In most cases, steroids are effective. Conventional immunosuppressants are not commonly able to replace steroids in maintaining a satisfactory long-term control of symptoms. However, the majority of MuSK-MG patients are refractory to treatment. In these cases, the use of rituximab showed promising results, resulting in sustained symptom control.

Rituximab in AChR subtype of myasthenia gravis: systematic review

Myasthenia gravis (MG) is a chronic autoimmune disorder of the neuromuscular junction characterised by an autoantibody against acetylcholine receptor (AChR-Ab), autoantibody against muscle-specific kinase (MuSK-Ab), lipoprotein-related protein 4 or agrin in the postsynaptic membrane at the neuromuscular junction. Many patients are resistant to conventional treatment and effective therapies are needed. Rituximab (RTX) is a monoclonal antibody directed against CD20 antigen on B cells which has been successfully employed in anti-MuSK-Ab+MG, but the efficacy in anti-AChR-Ab+MG is still debated. The purpose of this systematic review was to describe the best evidence for RTX in the acetylcholine receptor subtype. The authors undertook a literature search during the period of 1999-2019 according to the Preferred Reporting Items for Systematic Reviews and Meta-Analys methodology, employing (myasthenia)+(gravis)+(RTX) as search terms. The analysis was confined to studies that include at least five patients with confirmed anti-AChR-Ab+MG. Thirteen studies have been selected, showing a good safety. The data obtained were heterogeneous in terms of posology, administration scheme and patients' evaluation, ranging from a minimum of two to a maximum of three cycles. RTX led to a sustained clinical improvement with prolonged time to relapse, in parallel to a reduction or discontinuation of other immunosuppressive therapies. Treatment with RTX appears to work in some but not all patients with anti-AChR-Ab+MG, but randomised controlled trials are needed. Future studies should take into account the subtype of MG and employ reliable measures of outcome and severity focusing on how to identify patients who may benefit from the treatment. Trial registration number: NCT02110706.

Use of rituximab in muscle-specific tyrosine kinase antibody-positive myasthenia gravis: Preliminary observations from a tertiary care center in Northern India

OBJECTIVES:

Approximately 10%–15% of patients with myasthenia gravis (MG) are refractory to standard treatment. A sizable chunk of these patients is due to muscle-specific tyrosine kinase (MuSK) antibody-positive MG which often runs a severe course with frequent relapses and poor response to conventional treatment. We report six patients with refractory MuSK-positive MG who responded well to the treatment with rituximab.

PATIENTS AND METHODS:

In this prospective institute-based observational study, we report six MuSK antibody-positive MG patients, who did not achieve remission with standard treatment and were later started on rituximab infusion.

RESULTS:

There was a significant clinical improvement in all patients after starting rituximab.

CONCLUSION:

Rituximab is an effective immunomodulatory therapy in MuSK antibody-positive MG patients who are not responding to the standard treatment.

Immunotherapy in myasthenia gravis in the era of biologics

No consensus has been reached on the ideal therapeutic algorithm for myasthenia gravis (MG). Most patients with MG require induction therapy with high doses of corticosteroids and maintenance with an immunosuppressant. Severe cases and acute worsening require intravenous immunoglobulin or plasmapheresis before oral immunosuppressants start having an effect. However, biologics are emerging as important therapeutic tools that promise to provide better corticosteroid sparing effects than standard treatments and can even induce remission. In particular, eculizumab, a monoclonal antibody against complement C5, has been approved by the FDA for refractory MG on the basis of a phase III trial. Rituximab, an anti-CD20 monoclonal antibody that depletes peripheral B cells, has also been effective in many large uncontrolled series, although was not in a small phase III trial. Whether the newer anti-CD20 agents ocrelizumab, ofatumumab, obinutuzumab, ublituximab or inebilizumab will be more effective remains unclear. Belimumab, an antibody against the B cell trophic factor BAFF, was ineffective in phase III trials, and efgartigimod, which depletes antibodies, was effective in a phase II study. Some anti-cytokine agents relevant to MG immunopathogenesis also seem promising. Checkpoint inhibitors can trigger MG in some patients, necessitating early intervention. Increased availability of new biologics provides targeted immunotherapies and the opportunities to develop more specific therapies.

Low-dose rituximab every 6 months for the treatment of acetylcholine receptor-positive refractory generalized myasthenia gravis

INTRODUCTION

In this prospective, open-label study we explore the effectiveness of low-dose rituximab every 6 months in treating refractory generalized myasthenia gravis (GMG).

METHODS

Twelve patients with acetylcholine receptor (AChR)-positive refractory GMG were enrolled for the study. The primary endpoint was the change in quantitative myasthenia gravis (QMG) score from baseline to the study end. Secondary endpoints included changes in manual muscle testing (MMT), MG-Related Activities of Daily Living (MG-ADL), and 15-item Quality-of-Life (MGQOL-15) scores, as well as prednisolone reduction.

RESULTS

MG decreased from 18.25 ± 4.03 to 8.42 ± 3.99 (P = .0001), MMT from 27.50 ± 17.78 to 4.58 ± 4.34 (P = .0001), ADL from 8.50 ± 2.84 to 1.17 ± 1.27 (P < .0001), MGQOL-15 from 37.25 ± 13.78 to 17.50 ± 9.73 (P = .0015), and prednisolone dose from 29.38 ± 11.92 mg/day to 8.86 ± 1.88 mg/day (P ≤ .01).

DISCUSSION

Low-dose rituximab every 6 months is effective in treating refractory GMG patients.

Myasthenia gravis

Myasthenia gravis (MG) is an autoimmune disease caused by antibodies against the acetylcholine receptor (AChR), muscle-specific kinase (MuSK) or other AChR-related proteins in the postsynaptic muscle membrane. Localized or general muscle weakness is the predominant symptom and is induced by the antibodies. Patients are grouped according to the presence of antibodies, symptoms, age at onset and thymus pathology. Diagnosis is straightforward in most patients with typical symptoms and a positive antibody test, although a detailed clinical and neurophysiological examination is important in antibody-negative patients. MG therapy should be ambitious and aim for clinical remission or only mild symptoms with near-normal function and quality of life. Treatment should be based on MG subgroup and includes symptomatic treatment using acetylcholinesterase inhibitors, thymectomy and immunotherapy. Intravenous immunoglobulin and plasma exchange are fast-acting treatments used for disease exacerbations, and intensive care is necessary during exacerbations with respiratory failure. Comorbidity is frequent, particularly in elderly patients. Active physical training should be encouraged.

Understanding the burden of refractory myasthenia gravis

Myasthenia gravis (MG) is an autoantibody-mediated disease that compromises the acetylcholine receptors or associated structures of the postsynaptic membrane of the neuromuscular junction. This leads to impaired neuromuscular transmission and subsequent fluctuating fatigability and weakness of ocular, bulbar, and limb skeletal muscles. Over the past few decades, there have been significant advances in our understanding of the disease pathophysiology and improvements in prognosis due to intensive care medicine and immunomodulation. Despite this, an estimated 10-20% of patients with MG do not achieve an adequate response, are intolerant to conventional treatment, or require chronic treatment with intravenous immunoglobulins or plasma separation procedures. Such patients are regarded as having MG that is 'refractory' to treatment and may represent a distinct clinical subgroup. Because the majority of patients with MG have well-controlled disease, the burden of illness in the minority with refractory disease is poorly understood and may be underestimated. However, clinically these patients are liable to experience extreme fatigue, considerable disability owing to uncontrolled symptoms, and frequent myasthenic crises and hospitalizations. Both acute adverse effects and an increased risk of comorbidity from treatment regimens may contribute to reduced quality of life. As yet, little is known concerning the impact of refractory MG on mental health and health-related quality of life. This review aims to highlight the burden of disease and unmet needs in patients with refractory MG.

Italian recommendations for the diagnosis and treatment of myasthenia gravis

Myasthenia gravis is a well-treatable disease, in which a prompt diagnosis and an adequate management can achieve satisfactory control of symptoms in the great majority of patients. Improved knowledge of the disease pathogenesis has led to recognition of patient subgroups, according to associated antibodies, age at onset and thymus pathology, and to a more personalized treatment. When myasthenia gravis is suspected on clinical grounds, diagnostic confirmation relies mainly on the detection of specific antibodies. Neurophysiological studies and, to a lesser extent, clinical response to cholinesterase inhibitors support the diagnosis in seronegative patients. In these cases, the differentiation from congenital myasthenia can be challenging. Treatment planning must consider weakness extension and severity, disease subtype, thymus pathology, together with patient characteristics and comorbidities. Since most subjects with myasthenia gravis require long-term immunosuppressive therapy, surveillance of expected and potential adverse events is critical. For patients refractory to conventional immunosuppression, the use of biologic agents is highly promising. These recommendations are addressed to non-experts on neuromuscular transmission disorders. The diagnostic procedures and therapeutic approaches hereafter described are largely accessible in Italy.

Myasthenia gravis: new developments in research and treatment

PURPOSE OF REVIEW

Myasthenia gravis, a rare disorder of the neuromuscular transmission, is increasingly acknowledged as a syndrome more than as a single disease. This review summarizes recent advances in pathophysiology which confirm the disease heterogeneity, and may help find disease-targeted and patient-targeted therapies.

RECENT FINDINGS

Antibodies to the acetylcholine receptor, the muscle-specific tyrosine kinase and the lipoprotein receptor protein 4, characterize disease subtypes with distinct clinical traits and immune-pathogenic mechanisms. Genome-wide approaches have identified susceptibility loci within genes that participate in the immune response. Regulatory T and B cells appear to be defective in myasthenia gravis. In patients with acetylcholine receptor antibodies, thymectomy associated with prednisone proved more effective than prednisone alone in a multicenter randomized trial. New therapeutic options target B cells, B-cell growth factors and complement inhibition, and are currently reserved for patients with refractory disease.

SUMMARY

In the recent past, there has been an active search for new antigens in myasthenia gravis, whereas clinical and experimental studies have provided new insights of crucial pathways in immune regulation, which might become the targets of future therapeutic interventions.

An imbalance between regulatory T cells and T helper 17 cells in acetylcholine receptor-positive myasthenia gravis patients

A chronic autoimmune disease, myasthenia gravis (MG) is characterized in 85% of patients by antibodies directed against the acetylcholine receptor (AChR) located at the neuromuscular junction. The functional and effective balance between regulatory T cells (T_reg cells) and effector T cells (T_eff cells) is lost in the hyperplastic thymus of MG patients with antibodies specific for the AChR (AChR⁺ MG patients). The objective of this review is to describe how T_reg cells and inflammatory T cells participate in this imbalance and contribute to induce a chronic inflammatory state in the MG thymus. We discuss the origins and characteristics of T_reg cells and their reported dysfunctions in AChR⁺ MG patients. We also review the inflammatory condition observed in MG thymus, including overexpression of interleukin (IL)-1β, IL-6, and IL-23, cytokines that promote the differentiation of T helper 17 (T_H 17) cells and the expression of IL-17. We summarize the preclinical models used to determine the implication of expression of cytokines, such as IL-6, IL-12 (IL-23 subunit), IL-17, and interferon γ to the development of experimental autoimmune MG. Finally, we suggest that biological agents, such as humanized monoclonal antibodies that target the IL-23/T_H 17 pathway, should be investigated in the context of MG, as they have proven efficiency in other autoimmune diseases.

Myasthenia gravis with antibodies to MuSK: an update

Myasthenia gravis with antibodies to the muscle-specific tyrosine kinase (MuSK⁺ MG) is a rare disease with distinctive pathogenic mechanisms and clinical features. An acute onset and predominant bulbar muscle weakness are very common and highly suggestive of the disease. On the other hand, a more indolent course, atypical ocular presentation, and signs of cholinergic hyperactivity may complicate the diagnosis. Though MuSK⁺ MG is still a severe disease, over the years we have observed a steady reduction in the rate of respiratory crisis and a significant improvement in the clinical outcome, both likely related to earlier diagnosis and timely treatment. Despite the improved management, MuSK⁺ MG patients tend to remain dependent on long-term immunosuppressive treatment and may develop permanent disabling weakness. In uncontrolled studies, B cell depletion with rituximab proved effective in most patients with refractory disease, inducing prolonged clinical responses associated with a sustained reduction of serum antibody levels. Promising results from experimental studies and case reports suggest that both 3,4-diaminopyridine and albuterol may be effective as symptomatic agents.