Short-term effect of low-dose rituximab on myasthenia gravis with muscle-specific tyrosine kinase antibody

Efgartigimod for induction and maintenance therapy in muscle-specific kinase myasthenia gravis

Background

The efficacy of efgartigimod in treating myasthenia gravis (MG) patients with muscle-specific kinase (MuSK) antibodies has not been demonstrated in the clinical trial, existing case reports, or observational studies.

Objectives

To evaluate the efficacy and safety of efgartigimod combined with immunotherapies such as tacrolimus or B-cell depleting agents, as maintenance treatment for MuSK-MG patients.

Design

This retrospective study included 14 MuSK-MG patients treated with efgartigimod at three tertiary hospitals from 2023 to 2024.

Methods

Data on the activities of daily living (ADL) scores, Quantitative Myasthenia Gravis scores, and the time reaching minimal symptom expression (MSE) were collected. The combined use of steroids, immunosuppressants, and rescue therapies, as well as the adverse event incidence, were also recorded.

Results

The mean age at first efgartigimod treatment was 55 ± 18 years old with a median follow-up time of 28 weeks. From baseline to week 4, MG-ADL scores decreased significantly from 10.1 ± 4.0 to 2.2 ± 3.1 (n = 14, p = 0.001). The majority of patients (92.9%) maintains a reduction of at least 2 points for more than 8 weeks. The median time to achieve MSE was 4 weeks, with 71.4% (10/14) of patients reaching MSE by week 12. In patients receiving CD20 B cell depleting therapy or tacrolimus as maintenance, the time-weighted average dosage of prednisone was 16 mg while that in those with prednisone alone was 37 mg. Of all the 14 patients, one developed an upper respiratory tract infection 4 weeks after rituximab (RTX), and one was infected with herpes zoster virus 13 weeks after RTX.

Conclusion

A single-cycle efgartigimod as an induction therapy, combined with immunotherapies such as tacrolimus or B cell depleting agents, as maintenance treatment, could benefit MuSK-MG patients.

Efficacy and safety of different dosages of rituximab for myasthenia gravis: a single-arm meta-analysis

BACKGROUND

Rituximab (RTX) is one of the treatment options for refractory myasthenia gravis (MG), yet the optimal dosing schedule remains undetermined. Our study aims to explore this issue and offer a valuable reference for clinical dosing.

METHODS

This is a single-arm meta-analysis. Studies in adults with myasthenia gravis published before 31 December 2023 were searched in PubMed, Web of Science, and other databases. Two primary effectiveness outcomes were analyzed: (1) Proportion of patients achieving minimal manifestation status (MMS) or better, (2) Change in Quantitative MG Score (QMGs) after RTX treatment. Safety outcomes included the incidence and description of serious adverse events (SAEs) and adverse events (AEs). Forest plots were generated to provide an overview and detailed combined effects. Publication bias was evaluated using funnel plots and the Egger test. Conventional dose refers to an RTX regimen similar to that used for the treatment of B-cell lymphoma: 375 mg/m2 per week for 4 weeks or 1000 mg for Weeks 1 and 3. Dosing regimens below the conventional dose in a treatment cycle are defined as low dose.

RESULTS

A total of 1037 MG patients received RTX treatment. Overall, 59.0% (95% CI: 48.2-69.8%, n = 599) of patients achieved MMS or better, with a mean decrease in QMGs of 6.81 (95% CI, -9.27 to -4.35, n = 222). The low-dose group showed a higher proportion of patients achieving MMS or better (76.6% vs 51.6%) and a more significant decrease in QMGs from baseline (-9.04 vs -3.62) compared to the conventional dose group (P < 0.01). Differences in the incidence of SAEs and AEs between the two groups were not significant (P > 0.05). Univariate meta-regression analyses showed that the dose administered was significantly associated with the proportion of MMS or better and the change in QMGs, whereas the proportion of Musk patients was not significantly associated with any of the outcomes. Stepwise logistic regression analyses showed that non-refractory MG, mild disease severity (MGFA classification), and low-dose were significant predictors for achieving an MMS or better prognosis, whereas for achieving improvement or better, only low dose was an independent predictor.

CONCLUSION

RTX can improve clinical symptoms, reduce QMGs in MG patients and the use of oral glucocorticoids and other immunosuppressants. The efficacy of low-dose RTX in treating MG patients is more effective than conventional-dose RTX and demonstrates a better safety profile. Mild disease severity, non-refractory MG, low dose, and MuSK-MG over AChR-MG predict better efficacy. Large randomized controlled trials are necessary to evaluate the efficacy and safety of RTX in MG patients and its various subtypes.

Efficacy and safety of rituximab in anti-MuSK myasthenia Gravis: a systematic review and meta-analysis

This systematic review and meta-analysis evaluated the effectiveness and safety of rituximab in patients with myasthenia gravis harboring antibodies to muscle-specific kinase (anti-MuSK). Four databases were searched from inception to December 23, 2023. We included adult patients (aged ≥ 18 years) who were diagnosed with anti-MuSK myasthenia gravis and who received rituximab. The outcomes assessed were the proportions of patients who achieved minimal manifestations or better and those who achieved complete stable remission or pharmacologic remission, according to the Myasthenia Gravis Foundation of America Postintervention Status (MGFA-PIS) scale at the last follow-up. Additional outcomes were mean glucocorticoid dose reduction and severe adverse events. Twelve studies with 111 participants were included. Overall, 82% (95% CI, 71‒91%; I2 = 30.12%, P = 0.15) of patients achieved MGFA-PIS minimal manifestations or better, and 56% (95% CI, 45‒67%; I2 = 0.00%, P = 0.60) achieved MGFA-PIS complete stable remission or pharmacologic remission. The mean reduction in the glucocorticoid dose was 17.15 mg (95% CI, 11.77‒22.53; I2 = 32.40%, P = 0.19). Only one patient developed osteomyelitis during rituximab treatment. This study demonstrated that rituximab is a safe and effective treatment for anti-MuSK myasthenia gravis, helping patients achieve minimal manifestations, complete stable remission, or pharmacologic remission with minimal serious adverse events.

Clinical and laboratory remission with rituximab in anti-MuSK-positive myasthenia gravis

BACKGROUND

Increasing data are available on the use and efficacy of rituximab (RTX) in patients with anti-muscle-specific tyrosine kinase (MuSK)-positive myasthenia gravis (MG), especially those steroid-dependent or unresponsive to traditional immunotherapies.

AIMS

We aimed to evaluate the clinical characteristics and treatment responses of adult patients with generalized anti-MuSK-positive MG treated with RTX.

METHODS

We retrospectively recruited 16 patients who were on RTX, between January 2010 and September 2023. RTX was given 1000 mg/day intravenously twice, two weeks apart. Maintenance treatment was administered at intervals of 3-6 months based on clinical evaluation. The outcome was assessed by Myasthenia Gravis Foundation of America (MGFA) and Myasthenia Gravis Status and Treatment Intensity (MGSTI) scores. Additionally, anti-MuSK antibody levels were retested after treatment in all patients except one.

RESULTS

Twelve patients were female. The mean age at disease onset was 35.3 ± 17.3 years. The median duration between disease onset and RTX administration was 2.4 years (min-max: 0.5-36.5 years). The worst MGFA class before RTX was between IIIb-V. After RTX treatment, 81.3% of patients achieved MGFA minimal manifestations or better and MGSTI level 1 or better. Anti-MuSK antibodies became negative in 12 patients, while they remained positive in three. The changes in antibody levels seemed associated with clinical outcomes.

CONCLUSIONS

RTX is an effective treatment in anti-MuSK-positive MG. Furthermore, our results support the inhibition of antibody production by RTX and we recommend monitoring anti-MuSK antibody titers to follow disease progression and treatment response.

Efficacy and safety of low-dose rituximab in the treatment of myasthenia gravis: a systemic review and meta-analysis

Background

Rituximab (RTX) is a monoclonal antibody that has been increasingly used in the treatment of myasthenia gravis (MG). In most studies, the therapeutic protocol of RTX has been similar to that adopted for B cell lymphoma, with an increasing number of studies aimed at exploring the efficacy of low-dose RTX in MG. However, the beneficial effects of low-dose RTX in MG remain a subject of critical debate.

Methods

This study was conducted following the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines. Two reviewers (Xishuai Yang and Bingxia Li) independently conducted searches across multiple databases, including PubMed, MEDLINE, EMBASE, Web of Science, Cochrane Library, and China National Knowledge Infrastructure (CNKI). A meta-analysis, utilizing representative forest plots, was performed to assess "Improved clinical status" and changes in the Quantitative Myasthenia Gravis (QMG) score before and after treatment.

Results

A total of 17 studies involving 292 patients were included in the meta-analysis. A noticeable improvement in clinical status was observed in 91% of patients at the final follow-up after therapy (95% CI: 84-96%, P < 0.001). The QMG score showed a significant reduction following the treatment, with a standardized mean difference (SMD) of -1.69 (95% CI: -2.21 to -1.16, Z = 6.29, P < 0.001). In the acetylcholine receptor antibody-positive myasthenia gravis (AChR-MG) group, 90% of patients achieved improved clinical status (95% CI: 80-97%, P < 0.001) and the QMG score significantly decreased after low-dose RTX treatment, with an SMD of -1.51 (95% CI: -0.80 to -2.21, Z = 4.50, P < 0.001). In the muscle-specific kinase antibody-positive myasthenia gravis (MuSK-MG) group, 97% of patients achieved improved clinical status (95% CI: 89-100%, P < 0.001). The QMG score also significantly decreased following low-dose RTX treatment, with an SMD of -2.31 (95% CI: -2.99 to -1.62, Z = 6.60, P < 0.001). Adverse effects were reported in 29 out of 207 patients (14%, including infusion reactions in 22 patients (10.1%), infections in three patients (1.45%), cytopenia in two patients (0.96%), eosinophilia in one patient (0.48%), and hemiplegia in one patient (0.48%). Additionally, one patient (0.48%) succumbed to complications from invasive thymoma.

Conclusion

Our meta-analysis shows that low-dose RTX is both effective and safe for treating MG.

Systematic Review Registration

PROSPERO, identifier: CRD42024509951.

Non-Coding RNAs in Myasthenia Gravis: From Immune Regulation to Personalized Medicine

Myasthenia gravis (MG) is an antibody-mediated autoimmune disorder characterized by altered neuromuscular transmission, which causes weakness and fatigability in the skeletal muscles. The etiology of MG is complex, being associated with multiple genetic and environmental factors. Over recent years, progress has been made in understanding the immunological alterations implicated in the disease, but the exact pathogenesis still needs to be elucidated. A pathogenic interplay between innate immunity and autoimmunity contributes to the intra-thymic MG development. Epigenetic changes are critically involved in both innate and adaptive immune response regulation. They can act as (i) pathological factors besides genetic predisposition and (ii) co-factors contributing to disease phenotypes or patient-specific disease course/outcomes. This article reviews the role of non-coding RNAs (ncRNAs) as epigenetic factors implicated in MG. Particular attention is dedicated to microRNAs (miRNAs), whose expression is altered in MG patients' thymuses and circulating blood. The long ncRNA (lncRNA) contribution to MG, although not fully characterized yet, is also discussed. By summarizing the most recent and fast-growing findings on ncRNAs in MG, we highlight the therapeutic potential of these molecules for achieving immune regulation and their value as biomarkers for the development of personalized medicine approaches to improve disease care.

Non-coding RNA and its network in the pathogenesis of Myasthenia Gravis

Myasthenia Gravis (MG) is a chronic autoimmune disease that primarily affects the neuromuscular junction, leading to muscle weakness in patients with this condition. Previous studies have identified several dysfunctions in thymus and peripheral blood mononuclear cells (PBMCs), such as the formation of ectopic germinal centers in the thymus and an imbalance of peripheral T helper cells and regulatory T cells, that contribute to the initiation and development of MG. Recent evidences suggest that noncoding RNA, including miRNA, lncRNA and circRNA may play a significant role in MG progression. Additionally, the network between these noncoding RNAs, such as the competing endogenous RNA regulatory network, has been found to be involved in MG progression. In this review, we summarized the roles of miRNA, lncRNA, and circRNA, highlighted their potential application as biomarkers in diagnosing MG, and discussed their potential regulatory networks in the abnormal thymus and PBMCs during MG development.

Long-term and low-dose rituximab treatment for chronic inflammatory demyelinating polyneuropathy

OBJECTIVE

To evaluate the efficacy and safety of a low-dose, long-term rituximab regimen in the treatment of idiopathic CIDP.

METHODS

This study included 15 CIDP patients treated with rituximab. Patients were administered 600 mg of rituximab intravenously every 6 months. Baseline evaluation was conducted before the initiation of rituximab treatment and subsequent evaluations were conducted 6 months after each rituximab infusion at on-site visits. Clinical improvement was objectively determined by improvement of scale score at least decrease ≥1 INCAT or mRS or increase ≥4 MRC or ≥8 cI-RODS after each infusion compared to baseline evaluation.

RESULTS

Fifteen CIDP patients were included and 10 of them were typical CIDP and five were distal CIDP. Nine in 15 (60%) patients after first infusion and three in six (50%) patients after second infusion exhibited significant clinical improvement compared to baseline evaluation. Additionally, rituximab facilitated a reduction or cessation of other medications in 73% of patients at last visit. The safety profile was favorable, with no reported adverse events.

CONCLUSION

Rituximab presents a promising therapeutic option for idiopathic CIDP, offering both efficacy and safety with a low-dose, long-term regimen.

Efficacy and safety of tocilizumab in patients with refractory generalized myasthenia gravis

BACKGROUND

We aimed to compare the efficacy of tocilizumab with conventional immunotherapy in refractory patients with acetylcholine receptor antibody-positive (AChR-Ab+) generalized myasthenia gravis (gMG).

METHODS

This single-center prospective cohort study was based on patients from an MG registry study in China and conducted from February 10, 2021 to March 31, 2022. Adult refractory patients with AChR-Ab+ gMG were assigned to tocilizumab or conventional immunotherapy groups. The primary efficacy outcome was the mean difference of MG activities of daily living (MG-ADL) change at weeks 4, 8, 12, 16, 20, 24 corresponding to that at the baseline between the two groups. A generalized estimating equation model was used for the primary outcome analysis. Safety was assessed based on adverse events.

RESULTS

Of 34 eligible patients, 20 (mean [standard deviation] age, 53.8 [21.9] years; 12 [60.0%] female) received tocilizumab and 14 received conventional immunotherapy (45.8 [18.0] years; 8 [57.1%] female). The tocilizumab group had greater reduction in MG-ADL score at week 4 (adjusted mean difference, -3.4; 95% CI, -4.7 to -2.0; p < 0.001) than the conventional immunotherapy group, with significant differences sustained through week 24 (adjusted mean difference, -4.5; 95% CI, -6.4 to -2.6; p < 0.001). At week 24, the proportion of patients achieving higher levels of MG-ADL (up to 7-point reduction) and QMG (up to 11-point reduction) scores improvement was significantly greater with tocilizumab. Tocilizumab had acceptable safety profiles without severe or unexpected safety issues.

CONCLUSION

Tocilizumab is safe and effective in improving the MG-ADL score and reducing prednisone dose in refractory AChR-Ab+ gMG, suggesting tocilizumab has the potential to be a valuable therapeutic option for such patients.

A predictive nomogram for short-term outcomes of myasthenia gravis patients treated with low-dose rituximab

BACKGROUND

This study aims to establish and validate a predictive nomogram for the short-term clinical outcomes of myasthenia gravis (MG) patients treated with low-dose rituximab.

METHODS

We retrospectively reviewed 108 patients who received rituximab of 600 mg every 6 months in Huashan Hospital and Tangdu Hospital. Of them, 76 patients from Huashan Hospital were included in the derivation cohort to develop the predictive nomogram, which was externally validated using 32 patients from Tangdu Hospital. The clinical response is defined as a ≥ 3 points decrease in QMG score within 6 months. Both clinical and genetic characteristics were included to screen predictors via multivariate logistic regression. Discrimination and calibration were measured by the area under the receiver operating characteristic curve (AUC-ROC) and Hosmer-Lemeshow test, respectively.

RESULTS

Disease duration (OR = 0.987, p = 0.032), positive anti-muscle-specific tyrosine kinase antibodies (OR = 19.8, p = 0.007), and genotypes in FCGR2A rs1801274 (AG: OR = 0.131, p = 0.024;GG:OR = 0.037, p = 0.010) were independently associated with clinical response of post-rituximab patients. The nomogram identified MG patients with clinical response with an AUC-ROC (95% CI) of 0.875 (0.798-0.952) in the derivation cohort and 0.741(0.501-0.982) in the validation cohort. Hosmer-Lemeshow test showed a good calibration (derivation: Chi-square = 3.181, p = 0.923; validation: Chi-square = 8.098, p = 0.424).

CONCLUSIONS

The nomogram achieved an optimal prediction of short-term outcomes in patients treated with low-dose rituximab.

Autoimmune central nervous system disorders: Antibody testing and its clinical utility

A rapidly expanding repertoire of neural antibody biomarkers exists for autoimmune central nervous system (CNS) disorders. Following clinical recognition of an autoimmune CNS disorder, the detection of a neural antibody facilitates diagnosis and informs prognosis and management. This review considers the phenotypes, diagnostic assay methodologies, and clinical utility of neural antibodies in autoimmune CNS disorders. Autoimmune CNS disorders may present with a diverse range of clinical features. Clinical phenotype should inform the neural antibodies selected for testing via the use of phenotype-specific panels. Both serum and cerebrospinal fluid (CSF) are preferred in the vast majority of cases but for some analytes either CSF (e.g. N-methyl-D-aspartate receptor [NMDA-R] IgG) or serum (e.g. aquaporin-4 [AQP4] IgG) specimens may be preferred. Screening using 2 methods is recommended for most analytes, particularly paraneoplastic antibodies. We utilize murine tissue-based indirect immunofluorescence assay (TIFA) with subsequent confirmatory protein-specific testing. The cellular location of the target antigen informs choice of confirmatory diagnostic assay (e.g. blot for intracellular antigens such as Hu; cell-based assay for cell surface targets such as leucine-rich glioma inactivated 1 [LGI1]). Titers of positive results have limited diagnostic utility with the exception of glutamic acid decarboxylase (GAD) 65 IgG autoimmunity, which is associated with neurological disease at higher values. While novel antibodies are typically discovered using established techniques such as TIFA and immunoprecipitation-mass spectrometry, more recent high-throughput molecular technologies (such as protein microarray and phage-display immunoprecipitation sequencing) may expedite the process of antibody discovery. Individual neural antibodies inform the clinician regarding the clinical associations, oncological risk stratification and tumor histology, the likely prognosis, and immunotherapy choice. In the era of neural antibody biomarkers for autoimmune CNS disorders, access to appropriate laboratory assays for neural antibodies is of critical importance in the diagnosis and management of these disorders.

Clinical Features and Prognostic Analysis of MuSK-Antibody-Positive Myasthenia Gravis versus Double-Seropositive Myasthenia Gravis: A Single-Center Study from Central South China

Purpose

To decipher the discrepancies between muscle-specific kinase antibody-positive myasthenia gravis (MuSK-MG) and double-seropositive myasthenia gravis (DSP-MG), and to determine prognostic factors for minimal manifestation status (MMS) achievement in MG patients with MuSK autoantibodies (MuSK-Ab).

Patients and Methods

A total of 34 MG patients seropositive for MuSK-Ab were enrolled in this study. The demographic and clinical features were compared between MuSK-MG (n = 28) and DSP-MG (n = 6) patients, and factors affecting MMS induction in all patients with MuSK-Ab were identified using Cox regression analysis.

Results

Compared to MuSK-MG patients, those with DSP-MG had similar clinical characteristics, except that they had a lower frequency of bulbar muscle involvement at nadir (50% vs 92.9%; P = 0.029) and higher proportions of comorbidities with diabetes mellitus (33.3% vs 0%; P = 0.027) and thymic abnormalities (33.3% vs 0%; P = 0.027). Higher MG Activities of Daily Living (MG-ADL) scores (HR = 0.16, 95% CI: 0.037-0.7, P = 0.015) and axial muscle involvement at nadir (HR = 0.39, 95% CI: 0.16-0.94, P = 0.035) were negative prognostic factors for MMS achievement in patients with MuSK-Ab regardless of acetylcholine receptor antibody (AChR-Ab) positivity. Multivariable Cox regression analysis further established higher MG-ADL scores at the nadir (HR = 0.19, 95% CI: 0.04-0.94; P = 0.042) as an independent risk factor for MMS achievement.

Conclusion

DSP-MG was comparable to MuSK-MG and could be considered a single entity in our cohort. In all MG patients with MuSK-Ab, a higher MG-ADL score at nadir may herald a lower chance of MMS achievement, with no observed potential effect of AChR-Ab presence.

The intricate dance of non-coding RNAs in myasthenia gravis pathogenesis and treatment

Myasthenia gravis (MG) stands as a perplexing autoimmune disorder affecting the neuromuscular junction, driven by a multitude of antibodies targeting postsynaptic elements. However, the mystery of MG pathogenesis has yet to be completely uncovered, and its heterogeneity also challenges diagnosis and treatment. Growing evidence shows the differential expression of non-coding RNAs (ncRNAs) in MG has played an essential role in the development of MG in recent years. Remarkably, these aberrantly expressed ncRNAs exhibit distinct profiles within diverse clinical subgroups and among patients harboring various antibody types. Furthermore, they have been implicated in orchestrating the production of inflammatory cytokines, perturbing the equilibrium of T helper 1 cells (Th1), T helper 17 cells (Th17), and regulatory T cells (Tregs), and inciting B cells to generate antibodies. Studies have elucidated that certain ncRNAs mirror the clinical severity of MG, while others may hold therapeutic significance, showcasing a propensity to return to normal levels following appropriate treatments or potentially foretelling the responsiveness to immunosuppressive therapies. Notably, the intricate interplay among these ncRNAs does not follow a linear trajectory but rather assembles into a complex network, with competing endogenous RNA (ceRNA) emerging as a prominent hub in some cases. This comprehensive review consolidates the landscape of dysregulated ncRNAs in MG, briefly delineating their pivotal role in MG pathogenesis. Furthermore, it explores their promise as prospective biomarkers, aiding in the elucidation of disease subtypes, assessment of disease severity, monitoring therapeutic responses, and as novel therapeutic targets.

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.

Effectiveness and safety of rituximab in autoimmune nodopathy: a single-center cohort study

Autoimmune nodopathy is a peripheral neuropathy characterized by acquired motor and sensory deficit with autoantibodies against the node of Ranvier or paranodal region in the peripheral nervous system. The clinical and pathological characteristics of the disease are distinct from that of chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), and the standard treatment for CIDP is partially effective. Rituximab is a chimeric monoclonal antibody which binds and depletes B cells in peripheral blood. This prospective observational study included 19 patients with autoimmune nodopathy. Participants received intravenous rituximab treatment 100 mg the first day and 500 mg the next day and given every 6 months. The Inflammatory Neuropathy Cause and Treatment (INCAT) disability score, Inflammatory Rasch-Built Overall Disability Scale (I-RODS), Medical Research Council (MRC) sum score, and Neuropathy Impairment Score (NIS) were collected at entry and before the rituximab infusion every 6 months. At the last visit, 94.7% (18/19) of the patients showed clinical improvement on either the INCAT, I-RODS, MRC, or NIS scale. After the first infusion, 9 patients (47.7%) showed improvement on the INCAT score, and 11 patients (57.9%) on cI-RODS. In patients who received more than one rituximab infusion, the improvement of INCAT score and cI-RODS at the last assessment was higher than that after the first infusion. We also observed tapered or withdrawn concomitant oral medications in these patients.

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.

A single low-dose rituximab infusion in severe chronic refractory myasthenia gravis in resource-limited settings

The benefits of multi-dose rituximab cycles in patients with refractory anti-muscle-specific kinase antibody myasthenia gravis (MuSK+MG) are well reported, although less consistently in anti-acetylcholine receptor antibody MG (AChR+MG). Responsivity data to single low-dose rituximab infusions for refractory autoimmune myasthenia, are limited. Here, observational outcomes using MG grading scores and prednisone doses, before and after at least six months of a single-dose infusion of rituximab, were audited in previously treatment-refractory MG patients in a resource-limited setting. Seventeen moderately-severe to severely symptomatic MG patients received single low-dose rituximab infusions (median 500-600 mg) after a median MG duration of 6 years; 13 individuals responded including 5/5 MuSK+MG, 7/10 AChR+MG and 1/2 double seronegative MG. Three (60%) MuSK+MG and three (30%) AChR+MG achieved persistent asymptomatic status. Although more MuSK+MG vs AChR+MG cases stopped prednisone (80% vs 20%, respectively), the prednisone doses in the AChR+MG group was significantly reduced ≥30% (p = 0.008) due to improved MG composite scores (p = 0.016) and with durable benefit (median 12 months). There were no differences between responders and non-responders in MG duration and age at infusion. These results suggest that a single low-dose rituximab infusion is worth trying in refractory MG, including AChR+MG patients, as some patients showed good and durable responses. These results are particularly relevant to resource-limited settings.

Effect of low-dose rituximab treatment on autoimmune nodopathy with anti-contactin 1 antibody

Background

Autoimmune nodopathy with anti-contactin-1 (CNTN1) responds well to rituximab instead of traditional therapies. Although a low-dose rituximab regimen was administered to patients with other autoimmune diseases, such as myasthenia gravis and neuromyelitis optica spectrum disorders, and satisfactory outcomes were obtained, this low-dose rituximab regimen has not been trialed in anti-CNTN1-positive patients.

Methods

Anti–CNTN1 nodopathy patients were enrolled in this prospective, open-label, self-controlled pilot study. A cell-based assay was used to detect anti-CNTN1 antibodies and their subclasses in both serum and cerebrospinal fluid. Clinical features were evaluated at baseline, 2 days, 14 days, and 6 months after single low-dose rituximab treatment (600 mg). The titers of the subclasses of anti-CNTN1 antibody and peripheral B cells were also evaluated at baseline, 2 days, and 6 months after the rituximab regimen.

Results

Two patients with anti–CNTN1 antibodies were enrolled. Both patients had neurological symptoms including muscle weakness, tremor, sensory ataxia, numbness and mild nephrotic symptoms. In the field of neurological symptoms, sensory ataxia markedly improved, and the titer of anti-CNTN1 antibody as well as CD19+ B cells decreased only two days following low-dose rituximab treatment. Other neurological symptoms improved within two weeks of rituximab treatment. At the 6-month follow-up, all neurological symptoms steadily improved with steroid reduction, and both the anti-CNTN1 antibody titer and CD19+ B cells steadily decreased. No adverse events were observed after this single low-dose rituximab treatment.

Conclusions

We confirmed the clinical efficacy of low-dose rituximab by B cell depletion in autoimmune nodopathy with anti-CNTN1 antibody. This rapid and long-lasting response suggests that low-dose rituximab is a promising option for anti-CNTN1 nodopathy.

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.

A Review on the Role of Non-Coding RNAs in the Pathogenesis of Myasthenia Gravis

Myasthenia gravis (MG) is an autoimmune condition related to autoantibodies against certain proteins in the postsynaptic membranes in the neuromuscular junction. This disorder has a multifactorial inheritance. The connection between environmental and genetic factors can be established by epigenetic factors, such as microRNAs (miRNAs) and long non-coding RNAs (lncRNAs). XLOC_003810, SNHG16, IFNG-AS1, and MALAT-1 are among the lncRNAs with a possible role in the pathoetiology of MG. Moreover, miR-150-5p, miR-155, miR-146a-5p, miR-20b, miR-21-5p, miR-126, let-7a-5p, and let-7f-5p are among miRNAs whose roles in the pathogenesis of MG has been assessed. In the current review, we summarize the impact of miRNAs and lncRNAs in the development or progression of MG.

Plasma cell biology: Foundations for targeted therapeutic development in transplantation

Solid organ transplantation is a life-saving procedure for patients with end-stage organ disease. Over the past 70 years, tremendous progress has been made in solid organ transplantation, particularly in T-cell-targeted immunosuppression and organ allocation systems. However, humoral alloimmune responses remain a major challenge to progress. Patients with preexisting antibodies to human leukocyte antigen (HLA) are at significant disadvantages in regard to receiving a well-matched organ, moreover, those who develop anti-HLA antibodies after transplantation face a significant foreshortening of renal allograft survival. Historical therapies to desensitize patients prior to transplantation or to treat posttransplant AMR have had limited effectiveness, likely because they do not significantly reduce antibody levels, as plasma cells, the source of antibody production, remain largely unaffected. Herein, we will discuss the significance of plasma cells in transplantation, aspects of their biology as potential therapeutic targets, clinical challenges in developing strategies to target plasma cells in transplantation, and lastly, novel approaches that have potential to advance the field.