Effect of efgartigimod on muscle group subdomains in participants with generalized myasthenia gravis: post hoc analyses of the phase 3 pivotal ADAPT study

BACKGROUND AND PURPOSE

Generalized myasthenia gravis (gMG) is a rare, chronic, neuromuscular autoimmune disease mediated by pathogenic immunoglobulin G (IgG) autoantibodies. Patients with gMG experience debilitating muscle weakness, resulting in impaired mobility, speech, swallowing, vision and respiratory function. Efgartigimod is a human IgG1 antibody Fc fragment engineered for increased binding affinity to neonatal Fc receptor. The neonatal Fc receptor blockade by efgartigimod competitively inhibits endogenous IgG binding, leading to decreased IgG recycling and increased degradation resulting in lower IgG concentration.

METHODS

The safety and efficacy of efgartigimod were evaluated in the ADAPT study. Key efficacy outcome measures included Myasthenia Gravis Activities of Daily Living (MG-ADL) and Quantitative Myasthenia Gravis (QMG) scores. Efgartigimod demonstrated significant improvement in both the MG-ADL and QMG scores. This post hoc analysis aimed to determine whether all subdomains of MG-ADL and QMG improved with efgartigimod treatment. Individual items of MG-ADL and QMG were grouped into four subdomains: bulbar, ocular, limb/gross motor and respiratory. Change from baseline over 10 weeks in each subdomain was calculated for each group.

RESULTS

Greater improvements from baseline were seen across MG-ADL subdomains in participants treated with efgartigimod compared with placebo. These improvements were typically observed 1 to 2 weeks after the first infusion and correlated with reductions in IgG. Similar results were observed across most QMG subdomains.

CONCLUSIONS

These post hoc analyses of MG-ADL and QMG subdomain data from ADAPT suggest that efgartigimod is beneficial in improving muscle function and strength across all muscle groups, leading to the observed efficacy in participants with gMG.

The Burden Patients with Myasthenia Gravis Experience in Terms of Breathing, Fatigue, Sleep, Mental Health, Discomfort and Usual Activities in Comparison to the General Population

INTRODUCTION

Myasthenia gravis (MG) is a rare neuromuscular disorder marked by a variable combination of weakness of eye, bulbar, respiratory, axial, and limb muscles. This study compared the experience of people with MG regarding breathing, fatigue, sleep, pain/discomfort, mental health, and usual activities with the general population.

METHODS

The MyRealWorld-MG digital, multinational study enrolled patients with MG and collected demographics, PROMIS-Dyspnea, PROMIS-Sleep Disturbance, FACIT-Fatigue, EQ-5D-5L, Health Utilities Index (HUI-3), Hospital Anxiety and Depression Scale (HADS), MG-Activities of Daily Living (MG-ADL), and MG-Quality-of-Life (MG-QoL-15r). Comparisons with the general population were based on PROMIS population norms, published literature, or on data from a digital, multinational, observational study which enrolled a representative sample of the general population (POPUP).

RESULTS

In MyRealWorld-MG (N = 2074), patients experienced higher intensity, frequency, and duration of PROMIS shortness of breath than a US population (p < 0.0001). Patients with MG had higher PROMIS-Sleep Disturbance scores than POPUP (53.7 vs 50.0, p < 0.0001), and 54.9% of patients had clinically severe FACIT-Fatigue scores vs 6.8% in POPUP (p < 0.0001). Among patients with MG, 69.6% and 18.5% had moderate-to-severe HADS-Anxiety and HADS-Depression compared to 20.3% and 6.9% in POPUP (p < 0.001). Statistically significant and strong associations were found between fatigue, sleep, dyspnea, usual activities, and emotions. All outcomes worsened with more severe disease.

CONCLUSION

A considerable burden was observed in this comparison of breathing, sleep, fatigue, mental health, and usual activities between patients with MG and the general population, using data from two international studies and published population norms. Even mildly affected patients had significantly worse outcomes than the general population.

People Diagnosed with Myasthenia Gravis have Lower health-related quality of life and Need More Medical and Caregiver Help in Comparison to the General Population: Analysis of Two Observational Studies

INTRODUCTION

Myasthenia gravis (MG) is a neuromuscular disease causing extreme muscular fatigue, triggering problems with vision, swallowing, speech, mobility, dexterity, and breathing. This analysis intended to estimate the health-related quality-of-life impact, the medical burden, and the need for caregiver help of people diagnosed with MG.

METHODS

MyRealWorld-MG (MRW) is an observational study among adults diagnosed with MG in 9 countries. The General Population Norms (POPUP) observational study enrolled representative members of the general population in 8 countries. In both digital studies, respondents entered personal characteristics and provided data on medical conditions, EQ-5D-5L, HUI3, MG-Activities of Daily Living (MG-ADL), sick leave, caregiver help, and medical care utilization.

RESULTS

In MRW (n = 1859), 58.4% of respondents had moderate-to-severe MG. Average utility values were lower in MRW versus POPUP (0.739 vs. 0.843 for EQ-5D-5L; 0.493 vs. 0.746 for HUI3), and declined with more severe disease (0.872, 0.707, 0.511 EQ-5D-5L utilities and 0.695, 0.443, 0.168 HUI3 utilities for mild, moderate, and severe MG, respectively). Taking sick leave in the past month was 2.6 times more frequent among people diagnosed with MG compared to the general population (34.4% vs. 13.2%) and four times more people diagnosed with MG reported needing help from a caregiver (34.8% vs. 8.3%). Use of medical care was twice as likely in MRW in comparison with POPUP (51.9% vs. 24.6%).

CONCLUSION

This direct comparison of people diagnosed with MG and the general population using two large international studies revealed significant negative impact of MG. Results were consistent across all outcomes, in all countries.

Association Between Myasthenia Gravis-Activities of Daily Living (MG-ADL) and EQ-5D-5L Utility Values: The Additional Effect of Efgartigimod on Utilities

INTRODUCTION

For patients with generalized myasthenia gravis (gMG), the association between symptom severity, often measured with the Myasthenia Gravis Activities of Daily Living (MG-ADL) instrument, and utility values is unknown.

METHODS

Data was analyzed from the phase 3 ADAPT trial, which included adult patients with gMG randomly assigned to treatment with efgartigimod + conventional therapy (EFG + CT) or placebo + CT (PBO + CT). MG-ADL total symptom scores and the EQ-5D-5L, a measure of health-related quality of life (HRQoL), were collected biweekly up to 26 weeks. Utility values were derived from the EQ-5D-5L data with the United Kingdom value set. Descriptive statistics were reported for MG-ADL and EQ-5D-5L at baseline and follow-up. A normal identity-link regression model estimated the association between utility and the eight MG-ADL items. A generalized estimating equations (GEE) model was estimated to predict utility based on the patient's MG-ADL score and treatment received.

RESULTS

A total of 167 patients (84 EFG + CT, 83 PBO + CT) contributed 167 baseline and 2867 follow-up measurements of MG-ADL and EQ-5D-5L. EFG + CT-treated patients experienced more improvements than PBO + CT-treated patients in most MG-ADL items and EQ-5D-5L dimensions, with the largest improvements observed in chewing, brushing teeth/combing hair, eyelid droop (MG-ADL); self-care, usual activities, mobility (EQ-5D-5L). The regression model indicated that individual MG-ADL items contributed differently to utility values, with the largest impact from brushing teeth/combing hair, rising from a chair, chewing, and breathing. The GEE model showed that each unit improvement in MG-ADL led to a statistically significant utility increase of 0.0233 (p < 0.001). In addition, a statistically significant improvement of 0.0598 (p = 0.0079) in utility was found for patients in the EFG + CT group compared to the PBO + CT group.

CONCLUSION

Among patients with gMG, improvements in MG-ADL were significantly associated with higher utility values. MG-ADL scores alone were not sufficient to capture the utility gained from efgartigimod therapy.

Patient-reported burden of myasthenia gravis: baseline results of the international prospective, observational, longitudinal real-world digital study MyRealWorld-MG

OBJECTIVES

Myasthenia gravis (MG) is a rare, chronic, autoimmune neuromuscular disease which can affect functional and mental aspects of health and health-related quality of life (HRQoL). This study aims to obtain detailed knowledge of the impact of MG on HRQoL in a broad population from the perspective of the patient.

DESIGN

Prospective, observational, digital, longitudinal real-world study.

SETTING

Adult patients with MG from seven countries (USA, Japan, Germany, UK, Italy, Spain and Canada) downloaded a mobile application onto their phones and entered data about themselves and their MG.

OUTCOME MEASURES

Data was collected using the following general and disease-specific patient-reported outcome measurements: EuroQol 5 Domains Health-Related Quality of Life Questionnaire (EQ-5D-5L), Myasthenia Gravis Activities of Daily Living (MG-ADL), Myasthenia Gravis Quality of Life 15-item revised scale (MG-QoL-15r), Hospital Anxiety and Depression Scale (HADS) and Health Utilities Index III (HUI3). Patients were categorised by their self-assessed Myasthenia Gravis Foundation of America (MGFA) class (I-V).

RESULTS

Baseline results of 841 participants (mean age 47 years, 70% women) are reported . The distribution across the MGFA classes was: 13.9%, 31.0%, 38.1%, 15.5% and 1.6% for classes I-V. The MGFA class was a strong predictor of all aspects of HRQoL, measured with disease-specific and with generic instruments. The domains in which patients with MG most frequently mentioned problems were usual activities, anxiety and depression, tiredness, breathing and vision. The mean total MG-ADL Score was positively associated with increasing MGFA classes: 2.7, 4.4, 6.3 and 8.4 for MGFA classes I-IV. Mean baseline EQ-5D-5L utility was also associated with MGFA classes and was 0.817, 0.766, 0.648 and 0.530 for MGFA class I-IV.

CONCLUSIONS

MG has a large impact on key aspects of health and HRQoL. The impact of this disease increases substantially with increasing disease severity.

Real-World Healthcare Resource Utilization and Cost Burden Assessment for Adults With Generalized Myasthenia Gravis in the United States

Introduction

Limited evidence exists for healthcare resource utilization (HCRU) and costs associated with generalized myasthenia gravis (gMG), a rare autoimmune disorder, for adults in the United States.

Methods

Adults with ≥1 diagnostic claim for MG between 2014 and 2019 were identified using Symphony Health's Integrated Dataverse®. Using a novel algorithm, HCRU and costs over 12 months following index dates were evaluated for patients with gMG including those with exacerbation events. For patients who experienced crisis events, HCRU and costs were analyzed during the 36 months preceding, during, and 12 months following the events.

Results

Mean HCRU and costs were higher for newly diagnosed patients compared with previously diagnosed patients (hospitalizations: 0.46 vs. 0.34; all-cause costs: $26,419.20 vs. $24,941.47; direct costs for gMG treatments: $9,890.37 vs. $9,186.47) and further increased for patients with exacerbation events (hospitalizations: 0.72; all-cause costs: $43,734.15; direct costs for gMG treatments: $21,550.02). For patients who experienced crisis events, HCRU and costs markedly increased during the 12 months immediately before the crisis event (hospitalizations: 1.35; all-cause costs: $49,236.68) compared with the 2 preceding years and increased further during the 12 months following the crisis index date (hospitalizations: 2.78; all-cause costs: $173,956.99). Cost increases were, in large part, attributed to treatments received.

Discussion

New diagnosis, exacerbation, and crisis events were drivers of HCRU and cost for patients with gMG. Particularly, high costs of gMG-specific medications associated with intervention for exacerbation and crisis events contributed to increased all-cause costs.