Low-dose rituximab treatment for new-onset generalized myasthenia gravis

Advancements and prospects of novel biologicals for myasthenia gravis: toward personalized treatment based on autoantibody specificities

Myasthenia gravis (MG) is an antibody-mediated autoimmune disease with a prevalence of 150-250 cases per million individuals. Autoantibodies include long-lived antibodies against the acetylcholine receptor (AChR), mainly of the IgG1 subclass, and IgG4, produced almost exclusively by short-lived plasmablasts, which are prevalent in muscle-specific tyrosine kinase (MuSK) myasthenia gravis. Numerous investigations have demonstrated that MG patients receiving conventional medication today still do not possess satisfactory symptom control, indicating a substantial disease burden. Subsequently, based on the type of the autoantibody and the pathogenesis, we synthesized the published material to date and reached a conclusion regarding the literature related to personalized targeted therapy for MG. Novel agents for AChR MG have shown their efficacy in clinical research, such as complement inhibitors, FcRn receptor antagonists, and B-cell activating factor (BAFF) inhibitors. Rituximab, a representative drug of anti-CD20 therapy, has demonstrated benefits in treatment of MuSK MG patients. Due to the existence of low-affinity antibodies or unidentified antibodies that are inaccessible by existing methods, the treatment for seronegative MG remains complicated; thus, special testing and therapy considerations are necessary. It may be advantageous to initiate the application of novel biologicals at an early stage of the disease. Currently, therapies can also be combined and individualized according to different types of antibodies. With such a wide range of drugs, how to tailor treatment strategies to patients with various conditions and find the most suitable solution for each MG profile are our necessary and urgent aims.

Treating myasthenia gravis beyond the eye clinic

Myasthenia gravis (MG) is one of the most well characterised autoimmune disorders affecting the neuromuscular junction with autoantibodies targeting the acetylcholine receptor (AChR) complex. The vast majority of patients present with ocular symptoms including double vision and ptosis, but may progress on to develop generalised fatiguable muscle weakness. Severe involvement of the bulbar muscles can lead to dysphagia, dysarthria and breathing difficulties which can progress to myasthenic crisis needing ventilatory support. Given the predominant ocular onset of the disease, it is important that ophthalmologists are aware of the differential diagnosis, investigations and management including evolving therapies. When the disease remains localised to the extraocular muscles (ocular MG) IgG1 and IgG3 antibodies against the AChR (including clustered AChR) are present in nearly 50% of patients. In generalised MG this is seen in nearly 90% patients. Other antibodies include those against muscle specific tyrosine kinase (MuSK) and lipoprotein receptor related protein 4 (LRP4). Even though decremental response on repetitive nerve stimulation is the most well recognised neurophysiological abnormality, single fibre electromyogram (SFEMG) in experienced hands is the most sensitive test which helps in the diagnosis. Initial treatment should be using cholinesterase inhibitors and then proceeding to immunosuppression using corticosteroids and steroid sparing drugs. Patients requiring bulbar muscle support may need rescue therapies including plasma exchange and intravenous immunoglobulin (IVIg). Newer therapeutic targets include those against the B lymphocytes, complement system, neonatal Fc receptors (FcRn) and various other elements of the immune system.

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.

Rituximab induces a transient fluctuation of peripheral and follicular helper T cells in neuromyelitis optica spectrum disorder

Autoreactive CD4+ helper T cells are implicated in the pathogenesis of neuromyelitis optica spectrum disorder (NMOSD). Both PD-1+CXCR5+CD4+ T follicular helper (Tfh) cells and PD-1+CXCR5-CD4+ T peripheral helper (Tph) cells can contribute to B-cell immune responses and the production of antibodies. Here we show the effect of B-cell depletion with rituximab on the homeostasis of Tfh cells, Tph cells and their subsets in patients with NMOSD. After rituximab treatment, total Tph cells, total Tfh cells, Tph17 cells, Tph17.1 cells, Tph1 cells, and Tfh1 cells tended to decrease at month 1, but gradually increased at month 6 and restored at month 12. Besides, Tph17.1 cells and Tfh17.1 cells were correlated with the proportion of CD19- antibody-secreting cells. Our data suggest that rituximab induced a fluctuation of proinflammatory Tph and Tfh subsets within one year after initiation of the treatment.

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.

Knowledge mapping of targeted immunotherapy for myasthenia gravis from 1998 to 2022: A bibliometric analysis

Background

The treatment of myasthenia gravis (MG) has advanced from steroids and traditional immunosuppressants to targeted immunotherapy. Targeted immunotherapy has been successfully employed in clinical practice in recent years. This study aimed to explore the emerging trend of targeted immunotherapy in MG and summarize the knowledge structure through bibliometric methods.

Methods

The Web of Science Core Collection database (WoSCC) was chosen to retrieve the literature on targeted immunotherapy for MG. Two bibliometric analysis software, VOSviewer and CiteSpace, and bibliometric online platform were mainly used to evaluate the contributions from countries/regions, institutions, journals, and authors through the construction and visualization of bibliometric networks. By systematically reviewing a knowledge domain, future research developments were determined. The R version 4.1.2 and Microsoft Excel 365 were used for statistical analysis.

Results

A total of 562 original articles and 262 reviews relevant to MG targeted immunotherapy were included. The number of publications on targeted immunotherapy for MG exhibited a two-phase advancement. The first stage showed a steady growth trend from 1998 to 2016, with an annual number of no more than 35 publications. The second stage revealed an explosive growth trend from 2017, reaching a peak number of publications in 2020. The United States ranked first in the number of publications, citations, and h-index. The author with the highest citation and h-index was Vincent A. And 28.03% of the articles were published in the top 10 journals. In addition to “myasthenia gravis”, the keyword with the highest consideration was “rituximab”, followed by “double-blind”, which indicate research hotspots gradually from basic research to clinical research over time, especially in the field of targeted immunotherapy. The MG treatment has entered a personalized precision treatment phase. Exploration into new target molecules and conducting high-quality randomized controlled trials on existing biological agents are the further research direction.

Conclusion

The current study summarized the global research trends concerning targeted immunotherapy for MG. Research interests gradually advanced from basic research to clinical research. MG treatment has entered a personalized precision treatment phase. Further investigations into new target molecules and high-quality randomized controlled trials on existing biological agents are required urgently to direct future immunotherapy research.

Individualized regimen of low-dose rituximab monotherapy for new-onset AChR-positive generalized myasthenia gravis

BACKGROUND

Generalized AChR-MG is an archetype of B cell-mediated autoimmune disorders, and use of biologic agent rituximab (RTX) for B cell depletion is generally limited to immunosuppressive therapy-refractory cases. However, benefit of RTX monotherapy and individualized regimen with optimal dosage in early stage of new-onset generalized AChR-MG still remains to be elucidated. In this retrospective study, we explore the efficacy and safety of personalized regimen of 100 mg low-dose rituximab monotherapy in treating new-onset generalized AChR-MG.

METHODS

Thirteen new-onset generalized AChR-MG patients were enrolled for the study, initiating RTX treatment from November 2017 to August 2020. The individualized low-dose RTX monotherapy protocol consisted of 100 mg induction treatment weekly with no more than three circles, followed by reinfusion (100 mg once) sequentially according to whether achieving primary endpoint and peripheral CD19 + B-cell repopulation ≥ 1% of total lymphocytes at each visit (every 3 months). Outcome measures included MGFA-PIS Minimal Manifestation (MM) or better status (primary endpoint), changes in QMG, MMT, MG-ADL and MGQOL-15 scores (secondary endpoint), as well as cholinesterase inhibitors dosage.

RESULTS

All 13 patients achieved the primary endpoint in parallel with significant improvement of QMG, MMT, MG-ADL MGQOL-15 scores, and reduction of cholinesterase inhibitors dose. A total of 52 visits were performed during follow-up, and only 10 assessments presenting peripheral CD19 + B-cell repopulation (≥ 1%) without "MM or better status" were followed by RTX reinfusions (100 mg once) for clinical remission. The total dosage of RTX was only 346.15 ± 96.74 mg (including 269.23 ± 63.04 mg for induction and 76.92 ± 59.91 mg for reinfusion), which seemed to be much lower than those dosages used in new-onset generalized AChR-MG as described previously. Moreover, compared with patients without thymoma, thymectomy markedly delayed initiation of RTX for patients with thymoma (log-rank test, p = 0.0002), but the delaying treatments showed no influence on the time for achieving primary outcome (log-rank test, p = 0.2517).

CONCLUSION

Our study firstly showed that individualized regimen of low-dose RTX monotherapy is effective and safe for early treatment of new-onset generalized AChR-MG, and practicable for directing RTX reinfusion and withdrawal. Moreover, the monotherapy protocol was also indicated to be extensively applicable in both new-onset AChR-MG with thymoma (thymectomy) and without thymoma.

Longitudinal treatment responsiveness on plasma neurofilament light chain and glial fibrillary acidic protein levels in neuromyelitis optica spectrum disorder

Background

Neurofilament light chain (NfL) and glial fibrilliary acidic protein (GFAP) have been suggested to be biomarkers of the pathophysiological process of neuromyelitis optica spectrum disorders (NMOSD), but the relationship between the plasma levels of these molecules with disease activity and treatment is incompletely understood.

Objective

To investigate the treatment effects of disease-modifying drugs on plasma neurofilament light chain (pNfL) and plasma glial fibrillary acidic protein (pGFAP) and explore the predictive value of pNfL and pGFAP in the activity of NMOSD.

Methods

pNfL and pGFAP levels were measured using single-molecule arrays in 72 patients with NMOSD and 38 healthy controls (HCs). Patients with NMOSD received tocilizumab (n = 29), rituximab (n = 23), oral prednisone (n = 16), and oral azathioprine or mycophenolate mofetil (n = 4).

Results

NMOSD patients had significantly higher pNfL and pGFAP levels than HCs (pNfL, 18.3 (11.2-39.3) versus 11.5 (7.0-23.3) pg/mL; p = 0.001; pGFAP, 149.7 (88.6-406.5) versus 68.7 (59.4-80.8) pg/mL; p < 0.001). Multivariable regression analyses indicated that baseline pNfL concentration was associated with age (p = 0.017), Expanded Disability Status Scale (EDSS) score (p = 0.002), and recent relapses (p < 0.001). Baseline pGFAP concentration was also associated with EDSS (p < 0.001) and recent relapses (p < 0.001). Compared with prednisone, tocilizumab and rituximab significantly reduced pNfL [tocilizumab, exp(β), 0.65; 95% confidence interval (CI), 0.56-0.75; p < 0.001; rituximab, exp(β), 0.79; 95% CI = 0.68-0.93; p = 0.005] and pGFAP levels [tocilizumab, exp(β), 0.64; 95% CI, 0.51-0.80; p < 0.001; rituximab, exp(β), 0.77; 95% CI, 0.61-0.98; p = 0.041] at the end of the study. The pNfL levels in the tocilizumab and rituximab groups were reduced to those of HCs [tocilizumab, 8.5 (7.06-17.90) pg/mL; p = 0.426; rituximab, 14.0 (9.94-21.80) pg/mL; p = 0.216]. However, the pGFAP levels did not decrease to those of HCs in NMOSD patients at the end of study [tocilizumab, 88.9 (63.4-131.8) pg/mL; p = 0.012; rituximab, 141.7 (90.8-192.7) pg/mL; p < 0.001].

Conclusion

pNfL and pGFAP may serve as biomarkers for NMOSD disease activity and treatment effects.

Retrospective analysis of safety and outcomes of rituximab for myasthenia gravis in patients ≥65 years old

INTRODUCTION/AIMS

Optimal management of myasthenia gravis (MG) in individuals ≥65 y old is unknown and patient factors may limit therapeutic choices. Safety and efficacy of rituximab in older patients with MG has not been well-studied.

METHODS

This retrospective study examined 40 patients (14 patients ≥65 y old) treated with rituximab for MG. The primary efficacy outcome was the proportion of patients reaching "Improved" or better on Myasthenia Gravis Foundation of America (MGFA) Post-Intervention Status (PIS) at 12 mo, compared between younger and older patients.

RESULTS

Ninety-two percent of patients ≥65 y old achieved MGFA PIS Improved or better at 12 mo compared to 69% of those <65 y old (P = .11). Median prednisone dose for the cohort decreased in the year following rituximab initiation (20 mg [interquartile range, 10-35] to 10 mg [0-13], P = .01). Non-refractory MG was predictive of favorable outcome, whereas age was not. Serious adverse events (SAEs) were similar between older and younger patients (21.4% vs. 30.8%, P = .715). No patients ≥65 y old required discontinuation of rituximab due to SAE. One death occurred in a patient <65 y old due to systemic inflammatory response syndrome.

DISCUSSION

At 12 mo following initiation of rituximab for MG, patients ≥65 y old experienced similarly high rates of improvement in their myasthenic symptoms as younger patients, without an increased risk of experiencing SAEs. Rituximab should be considered in the treatment paradigm in older patients and in non-refractory MG patients of any age.