Long-term efficacy and safety of leflunomide combined with low-dose prednisone in treatment of myasthenia gravis: a retrospective study.

BACKGROUND: Leflunomide and low-dose prednisone (0.25 mg/kg/day) (LEF + Pred) rapidly improved the clinical symptoms of myasthenia gravis (MG) patients. Here, we aimed to analyze the long-term efficacy and safety of LEF + Pred in MG patients. METHODS: This retrospective cohort study enrolled MG patients treated with LEF + Pred in our center between 2012 and 2020. We reviewed all the MG patients continuously treated with LEF + Pred for more than 1 year. MG activities of daily living (MG-ADL) profile score and quantitative MG scale (QMG) score in each clinical follow-up visits were collected for the efficacy analysis. The laboratory testing results of MG patients, the relevant chief complain and physical examination results in each follow-up visits were collected for the safety evaluation. RESULTS: In total, 103 patients were examined. Effective treatment was achieved in 58.3% of patients after 1 month and in 88.4% after 12 months. Overall, 63 patients (61.2%) exhibited only minimal manifestations after 12 months of treatment. The average MG-ADL score decreased from 6.0 to 1.0, while the average QMG score decreased from 10.0 to 4.0. The decrease in MG-ADL and QMG scores of patients with generalized MG was more pronounced than those of the ocular MG patients. Patients with MG who had a thymectomy had a smaller decrease in MG-ADL and QMG scores than those who did not have a thymectomy. Sixteen adverse effects associated with LEF + Pred were observed; none was severe. CONCLUSIONS: Long-term LEF + Pred therapy could considerably improve clinical symptoms in MG patients while being well tolerated with just few side effects.

Is myasthenia gravis a contraindication for botulinum toxin?

Botulinum toxin (BTX) is a neurotoxin that has been used to treat various disorders and has also become a popular choice for cosmetic indications, yet traditionally, myasthenia gravis (MG) is considered a contraindication for BTX. To determine whether BTX should be avoided in MG patients, clinical data from our MG and dystonia specialist clinic were analyzed retrospectively. In addition, a systematic literature review was conducted to identify all published cases associated with the co-existence of MG and BTX treatments. Here, we described one patient from our clinic, who received BTX injections before being given MG diagnosis. After the literature review, 8 cases with subclinical MG previously treated with BTX for dystonia or cosmetic reasons ("BTX injections before MG diagnosis") were identified. Markedly, 8 out of 8 (100%) patients developed obvious muscle weakness. In contrast, 10 patients presenting MG as comorbidity had received BTX for dystonia or overactive bladder ("BTX injection after MG diagnosis"), and 8 out of 10 (80%) experienced improved symptoms through appropriate dose modifications and adequate treatment for MG before receiving BTX injections. These findings support that, under proper management of co-existing MG, BTX could be used safely and successfully in patients presenting MG comorbidities in the future.

Leflunomide ameliorates experimental autoimmune myasthenia gravis by regulating humoral and cellular immune responses.

Leflunomide, an immunosuppressive disease-modifying anti-rheumatic drug (DMARD), is widely used in the treatment of rheumatoid arthritis (RA), psoriatic arthritis (PA) as well as multiple sclerosis. However, its role in myasthenia gravis (MG) has not yet been clearly explored. Here, we investigated the effect of leflunomide on experimental autoimmune myasthenia gravis (EAMG) in vivo and in vitro. The results demonstrated that leflunomide alleviated the severity of EAMG associated with reduced serum total anti-acetylcholine receptor (AChR) IgG levels. During the development of EAMG, the increase of follicular helper T cells (Tfh) 1, Tfh 17 cells and decrease of follicular regulatory T cells (Tfr) were reversely altered after leflunomide administration. Our work further found that leflunomide might inhibit Tfh cells through the IL-21/STAT3 pathway to reduce the secretion of antibodies by B cells. In addition, leflunomide rebuilt the balance of Th1/Th2/Th17/Treg subsets. These results suggested that leflunomide ameliorated EAMG severity by regulating humoral immune responses and Th cell profiles thereby providing a novel effective treatment strategy for MG.

Circulating Th1/17 cells serve as a biomarker of disease severity and a target for early intervention in AChR-MG patients.

Interleukin-17-expressing CD4+ T helper 17 (Th17) cells are considered to be critical regulators of thymic inflammation in AChR-MG patients. However, Th17 cells are functionally heterogeneous and circulating Th17 subsets are incompletely understood in AChR-MG patients. Here, we studied characteristics of Th17 subsets in peripheral blood from treatment-naïve AChR-MG patients, patients treated with immunosuppressants, as well as healthy controls. We found increased frequencies of circulating Th1-like Th17 (Th1/17) (IFN-γ + IL-17 + CD4 + CD3+) cells, which declined earlier than conventional Th17 (IFN-γ - IL-17 + CD4 + CD3+) cells in patients who respond well to immunosuppression treatment. Additionally, circulating Th1/17 cell frequencies were found to correlate positively with disease severity. Further, compared to conventional Th17 cells, Th1/17 cells showed an elevated expression of IFNG, TBX21, IL23R, CSF2, and a reduced expression of AHR and IL10. Taken together, our results suggest circulating Th1/17 cells may serve as a biomarker of disease severity and provide a strong rationale for early intervention in AChR-MG patients.

Quantitative features and clinical significance of two subpopulations of AChR-specific CD4+ T cells in patients with myasthenia gravis.

Acetylcholine receptor (AChR)-specific CD4+ T cells play a driving role in myasthenia gravis (MG) by regulating the production of autoantibodies. However, the quantitative features of AChR-specific T cells and their clinical significance in MG are unclear. In this study, we adopted standard and cultured enzyme-linked immunosorbent spot (ELISPOT) assays to quantify subpopulations of AChR-specific CD4+ T cells in MG patients, and evaluate their correlation with clinical characteristics. The results showed that Th1- and Th17-AChR-specific CD4+ T cells were detectable by standard and cultured ELISPOT assay respectively, with higher levels observed in MG patients comparing with healthy controls. The number of Th17-AChR-specific CD4+ T cells was positively correlated with anti-AChR antibody titer and quantitative MG score and may have latent capacity to reflect responses to immunosuppressants. These results highlight the differences in quantitative features of AChR-specific CD4+ T cells and imply Th17-AChR-specific CD4+ T cells can serve as a biomarker in MG.

AChR myasthenia gravis switching to MuSK or double antibody positive myasthenia gravis in two children and literature review.

Muscle-specific tyrosine kinase antibody (MuSK-Ab) and acetylcholine receptor antibody (AChR-Ab) coexistence in myasthenia gravis (MG) is very rare. In this report, two children with AChR-Ab switching to double antibody positive MG (DP-MG) or MuSK-Ab positive MG (MuSK-MG) are described. Six similar cases were found in the literature via online database search. Therefore, this study describes eight patients in total, six female and two male. The average age of onset was 7.25 ± 5.95 years. Four AChR-MG patients switched to DP-MG with no known precipitating factor and four switched after thymectomy (two to MuSK-MG and two to DP-MG). After the serological switch, the patients transitioned to the phenotype of MuSK-MG and responded poorly to cholinesterase inhibitors and well to corticosteroids and plasma exchange.

Hospital and healthcare insurance system record-based epidemiological study of myasthenia gravis in southern and northern China.

OBJECTIVE: This is the first cross-region epidemiological study of myasthenia gravis (MG) in China. We estimated the incidence, prevalence, and medical costs of MG in southern China and explored the differences between the southern and northern Chinese populations. METHODS: We collected and analyzed records from 20 hospitals in the southern city, Guangzhou, 13 hospitals in the northern city, Harbin, and two healthcare insurance systems: job based and residence based in Guangzhou during 2000-2017. RESULTS: (1) The estimated annual incidence of MG was 1.55-3.66 per 100,000, and the estimated prevalence of MG was 2.19-11.07 per 100,000 in southern China based on insurance records. (2) The proportion of hospitalized MG patients in the south-based hospital records was three times as high as that in the north-based hospital records. (3) Female MG prevalence was significantly higher than male MG prevalence in Guangzhou, while the similar gender difference in Harbin was not statistically significant due to higher variation in earlier years. (4) The average expense was $35-42 for each outpatient service and $2526-2673 for each hospitalization expense in the south. (5) Contrary to the increase of insurance-based estimate of MG prevalence, the proportion of hospitalized MG patients did not increase over the years, suggesting rising awareness and utilization of health insurance. CONCLUSIONS: The southern MG population had a significantly higher prevalence and a lower response threshold to medication than the northern MG population. These results are calling for further investigations on the genetic, cultural, and environmental variations of the Chinese MG populations between north and south.

Imbalance of the two main circulating dendritic cell subsets in patients with myasthenia gravis.

Although it is well documented that circulating dendritic cells (DCs) have specialized features during many kinds of physiological and pathological conditions, there are few reports about the features of DCs in the peripheral blood of myasthenia gravis (MG) patients. We investigated the quantitative and component features of DCs and their implications in MG. Peripheral blood samples from different kinds of MG patients were collected and their clinical characteristics were recorded. Using flow cytometry, we distinguished circulating DC subsets [plasmacytoid DCs (pDCs) and myeloid DCs (mDCs)] and enumerated their densities in peripheral blood. Absolute numbers of circulating pDCs were significantly decreased in naïve MG patients compared with healthy controls, resulting in a markedly lower ratio of the pDC to mDC percentage in total circulating DCs (pDCs/mDCs), suggesting an imbalance in the proportions of the two main circulating DC subsets. The clinical status of MG patients was improved after drug treatment, together with increased pDCs/mDCs. In a longitudinal follow-up, we observed that circulating mDCs were significantly reduced after 1 month of therapy with a corticosteroid and immunosuppressant, resulting in recovery of pDCs/mDCs. Although the exact meaning of the proportion change in circulating DC subsets is unknown, pDCs/mDCs might reflect the balance between the autoimmune response and immune tolerance of a patient. Moreover, changes in pDCs/mDCs during treatment might be a promising marker to predict the efficacy of a specific drug used for MG patients.

Influence of Drug Properties and Formulation on In Vitro Drug Release and Biowaiver Regulation of Oral Extended Release Dosage Forms.

Bioequivalence (BE) studies are often required to ensure therapeutic equivalence for major product and manufacturing changes. Waiver of a BE study (biowaiver) is highly desired for such changes. Current regulatory guidelines allow for biowaiver of proportionally similar lower strengths of an extended release (ER) product provided it exhibits similar dissolution to the higher strength in multimedia. The objective of this study is to demonstrate that (1) proportionally similar strengths of ER tablets exhibiting similar in vitro dissolution profiles do not always assure BE and (2) different strengths that do not meet the criteria for dissolution profile similarity may still be bioequivalent. Four marketed ER tablets were used as model drug products. Higher and lower (half) strength tablets were prepared or obtained from commercial source. In vitro drug release was compared using multi-pH media (pH 1.2, 4.5, 6.8) per regulatory guidance. In vivo performance was assessed based on the available in vivo BE data or established in vitro-in vivo relationships. This study demonstrated that the relationship between in vitro dissolution and in vivo performance is complex and dependent on the characteristics of specific drug molecules, product design, and in vitro test conditions. As a result, proportionally similar strengths of ER dosage forms that meet biowaiver requirements per current regulatory guidelines cannot ensure bioequivalence in all cases. Thus, without an established relationship between in vitro and in vivo performance, granting biowaiver based on passing in vitro tests may result in the approval of certain bioinequivalent products, presenting risks to patients. To justify any biowaiver using in vitro test, it is essential to understand the effects of drug properties, formulation design, product characteristics, test method, and its in vivo relevance. Therefore, biowaiver requirements of different strengths of ER dosage forms specified in the current regulatory guidance should be reevaluated to assure consistent safety and efficacy among different strengths.