Therapeutic Plasma Exchange Versus FcRn Inhibition in Autoimmune Disease

Efgartigimod as a fast-acting add-on therapy in manifest and impending myasthenic crisis: A single-center case series

Efgartigimod was the first-in-class neonatal Fc receptor antagonist approved for the treatment of acetylcholine receptor antibody positive (AChR+), Myasthenia Gravis Foundation of America (MGFA) Class II-IV generalized myasthenia gravis (gMG) patients. As a novel therapy, the clinical experiences are still lacking, especially for the use of efgartigimod in manifest and impending myasthenic crisis (IMC). We reported three AChR+, gMG patients, two with myasthenic crisis (MC) and one with IMC, treated with efgartigimod. MGFA class, MG-Activity of Daily Living score (MG-ADL), Quantitative MG score (QMG), and Muscle Research Council sum score (MRC), concentration of anti-AChR antibody, IgG, globulin, and albumin, subsets of T and B lymphocyte were evaluated or measured before, during and after efgartigimod treatment. All patients showed fast and robust response to efgartigimod with marked improvement in MGFA, MG-ADL, QMG, and MRC scores. Patient 1 did not respond effectively to IVIg but was successfully rescued by add-on efgartigimod. She extubated at 7 days after the first infusion and got rid of NIV after 14-days treatment. Patient 2 and patient 3 directly used efgartigimod when symptoms were not ameliorated by adjusting of oral drugs. Patient 2 wean from BiPAP at seven days after the first infusion. Patient 3 in IMC status, overcame the severe dysphagia at three days after the first infusion. Clinical symptoms continued to improve 1-2 weeks after discharge. Concentration of anti-AChR antibody, IgG and globulin were remarkably reduced by efgartigimod treatment. Our study supported that efgartigimod could act as a fast-acting rescue therapy for patients with MC or IMC. Larger studies from multicenter are required to provide further evidence.

The changing landscape of autoantibody testing in myasthenia gravis in the setting of novel drug treatments

Acquired myasthenia gravis (MG) is an autoimmune disease targeting the specific proteins in the postsynaptic muscle membrane. 50% of ocular and 80% of generalized MG have acetylcholine receptor antibodies (AChR Abs). 1-10% of MG patients have antibodies against muscle-specific kinase (MuSK), and 2-50 % of seronegative MG cases have antibodies against lipoprotein-receptor-related protein4 antibodies (LRP4 Abs). Serological testing is crucial for diagnosing and determining the appropriate therapeutic approach for MG patients. The radioimmunoprecipitation assay (RIPA) method is a historical standard test for detecting the AChR Abs and MuSK Abs. While it has nearly 100% specificity in the AChR Abs detection, its sensitivity is between 50--92%. The sensitivity and specificity of RIPA for detecting MuSK Abs is much lower. The fixed and live Cell-Based assays (f-CBA and L- CBA) have higher sensitivity than RIPA. With advancements in the serological diagnosis and management of MG, we now recommend a complete reflex testing algorithm on the first pretreatment sample of a suspected MG patient, starting with the binding and blocking assays for AChR Abs by RIPA and/ or f-CBA. If AChR Ab is negative, then reflex to MuSK Abs by RIPA and/ or CBAs. If AChR and MuSK Abs are negative, then use clustered L-CBA by request.

Current state and potential applications of neonatal Fc receptor (FcRn) inhibitors in hematologic conditions

The neonatal fragment crystallizable (Fc) receptor (FcRn) transports IgG across mucosal surfaces and the placenta and protects IgG from degradation. Numerous clinical trials are investigating therapeutic FcRn inhibition for various immune-mediated neuromuscular and rheumatologic conditions; however, FcRn inhibition also represents a potential therapy for IgG-mediated hematologic conditions (e.g., immune thrombocytopenia, autoimmune hemolytic anemia, immune thrombotic thrombocytopenic purpura, acquired hemophilia, red blood cell/platelet alloimmunization). Current evidence derived from both in vitro and in vivo studies suggests that FcRn inhibitors effectively reduce total IgG levels without impacting its production or altering the levels of other immunoglobulin isotypes. Moreover, the risk of serious adverse events, including serious infections, appears to be lower than that seen with other commonly used immunomodulatory/immunosuppressive therapies, albeit in the setting of limited clinical trial data. Ultimately, additional clinical trials that include varied patient populations are required prior to incorporating these agents into standard treatment algorithms for most hematologic conditions. However, based on the pathophysiology of IgG-mediated hematologic disorders and the mechanism of action of FcRn inhibitors, these agents may represent a future novel therapeutic strategy for patients with hematologic conditions caused by IgG antibodies.

Therapeutic Plasma Exchange in AChR-Ab Positive Generalized Myasthenia Gravis: A Real World Study About Its Early Response

Background

Since there is no clear priority or selection principle in the guidelines for myasthenia crisis, therapeutic plasma exchange (TPE) and intravenous immunoglobulin are often administered randomly. However, it should be more prudent in taking TPE due to its higher cost and risk. Studying its early response factors is crucial for managing myasthenia crisis and can improve medical and economic benefits.

Methods

A prospective observational study was conducted, and patients classified as having "impending myasthenia crisis" or experiencing a myasthenia crisis and treated by TPE were included. The primary endpoint was the response after TPE. Univariate logistic regression analysis and repeated measurement were performed to analyze factors related to TPE efficacy.

Results

A total of 30 patients who treated with TPE as their fast-acting treatments were enrolled. After TPE, those whose QMGs and/or MGCs decreased by ≥5 points or ≥30% of the baseline were judged as "response group", accounting for 66.67% (20/30). Respiratory symptoms had a response rate of 72.00% (18/25), showing the most remarkable improvement. Meanwhile, extraocular symptoms were the least sensitive, with only 8.00% (2/25) showing efficacy. Thymoma (100.00% vs 50.00%, P=0.002) and a high concentration of AChR-Ab (37.37 nmol/L vs 25.4 nmol/L, P=0.039) were common in the early response group. Repeated measures showed significant changes in AChR-Ab and CD19+ B cells before and after TPE (all with P < 0.05). After treatment, the CD19+ B cells tended to decrease in the response group.

Discussion

These results indicated that, for AChR-Ab positive generalized MG, TPE can quickly improve respiratory symptoms. Thymoma and a high concentration of AChR-Ab before TPE predict an early better response. Additionally, TPE may work by decreasing AChR-Ab levels and inducing immune regulation. Future prospective and randomized controlled studies are needed.

Case report: Recovery from refractory myasthenic crisis to minimal symptom expression after add-on treatment with efgartigimod

Myasthenic crisis, a life-threatening exacerbation of myasthenia gravis, is a significant clinical challenge, particularly when refractory to standard therapies. Here, we described a case of myasthenic crisis in which the patient transitioned from refractory myasthenic crisis to minimal symptom expression after receiving add-on treatment with efgartigimod, a novel neonatal Fc receptor antagonist. A 54 years-old woman who was diagnosed with anti-acetylcholine receptor antibody-positive myasthenia gravis experienced respiratory failure necessitating mechanical ventilation. Despite aggressive treatment with plasmapheresis, intravenous immunoglobulins, and high-dose corticosteroids, her condition continued to deteriorate, culminating in persistent myasthenic crisis. Efgartigimod was administered as salvage therapy. Remarkable improvement in neuromuscular function was observed within days, allowing for successful weaning from mechanical ventilation. Over the subsequent weeks, the patient's symptoms continued to ameliorate, ultimately reaching a state of minimal symptom expression. Serial assessments of her serum anti-acetylcholine receptor antibody titer showed a consistent decline in parallel with this clinical improvement. This case highlights efgartigimod's potential as an effective therapeutic option for refractory myasthenic crisis, offering new hope for patients facing this life-threatening condition.