A Phase 3 interventional study of Efgartigimod IV and Placebo IV in Generalized Myasthenia Gravis, gMG and Myasthenia Gravis, Generalized, sponsored by argenx. Active, not recruiting at 91 sites in 22 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-10.
Sponsored by argenx · Phase 3, Interventional, and Treatment
The primary purpose of this study is to measure the efficacy and safety of efgartigimod IV compared to placebo in participants with Acetylcholine Receptor Binding Antibody (AChR-Ab) seronegative Generalized Myasthenia Gravis (gMG). The study consists of a Part A where participants will be randomized to receive either efgartigimod IV or placebo IV and a Part B where participants completing part A will receive open-label efgartigimod IV. Participants will be in the study for up to (approximately) 3.5 years.
324 studies on the registry are indexed under Myasthenia Gravis; 146 are open to participants now.
This study's enrollment of 119 is above the median of 44 across 212 interventional studies indexed under Myasthenia Gravis.
Browse Myasthenia Gravis studies →argenx is the lead sponsor of 87 studies on the registry; 33 are open to participants now.
Of its 22 completed or terminated interventional studies of FDA-regulated products, 16 (73%) have results posted.
Counted across the registry records on this site, refreshed daily.
The participant has no known weakness in infancy and later develop fatigable weakness after aged 16 years and diagnosed with acquired gMG of both of the following:
Exclusion Criteria:
The complete list of exclusion criteria can be found in the protocol.
Patients receiving efgartigimod IV in both part A and part B
Biological: Efgartigimod IV
Patients receiving placebo during part A and receiving efgartigimod IV during part B
Biological: Efgartigimod IV · Other: Placebo IV
Intravenous infusion of efgartigimod
Intravenous infusion of placebo
MG-ADL Total Score Change From Baseline
The Myasthenia Gravis Activities of Daily Living (MG-ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (no symptoms) to 24 (most severe symptoms).
Time frame: Up to 29 days in part A
QMG Total Score Change From Baseline
The Quantitative Myasthenia Gravis (QMG) score includes 13 items that measure endurance or fatigability and accounts for fluctuations in disease state. The total score ranges from 0 (no symptoms) to 39 (highest disease severity).
Time frame: Up to 29 days in part A
Proportion of Participants Who Are Both MG-ADL and QMG Responders in Part A
A participant was an MG-ADL responder if there was a ≥2-point reduction in the MG-ADL total score compared with baseline that was maintained for at least 4 consecutive weeks (ie, at least 5 consecutive visits total), with the first reduction occurring no later than 1 week after the last administration of IMP in part A. A participant was a QMG responder if there was a ≥3-point reduction in the QMG total score compared with baseline that was maintained for at least 4 consecutive weeks (ie, at least 5 consecutive visits total), with the first reduction occurring no later than 1 week after the last administration of IMP in part A.
Time frame: Up to 8 weeks (part A)
Proportion of Participants With MSE
Minimal symptom expression (MSE) is defined as an MG-ADL total score of 0 or 1
Time frame: Up to 8 weeks (part A) + 3 years (part B)
Proportion of Participants Who Are MG-ADL Responders in Part A
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (no symptoms) to 24 (most severe symptoms). A participant was an MG-ADL responder if there was a ≥2-point reduction in the MG-ADL total score compared with baseline that was maintained for at least 4 consecutive weeks (ie, at least 5 consecutive visits total), with the first reduction occurring no later than 1 week after the last administration of IMP in part A.
Time frame: Up to 8 weeks (part A)
Proportion of Participants Who Are QMG Responders in Part A
The Quantitative myasthenia gravis (QMG) includes 13 items that measure endurance or fatigability and accounts for fluctuations in disease state. The total score ranges from 0 (no symptoms) to 39 (highest disease severity). A participant was a QMG responder if there was a ≥3-point reduction in the QMG total score compared with baseline that was maintained for at least 4 consecutive weeks (ie, at least 5 consecutive visits total), with the first reduction occurring no later than 1 week after the last administration of IMP in part A.
Time frame: Up to 8 weeks (part A)
Proportion of Participants Who Are Early MG-ADL Responders in Part A
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (no symptoms) to 24 (most severe symptoms). An Early MG-ADL responder is an MG-ADL responder who had an onset of an MG-ADL response no later than 2 weeks after the first administration of IMP in part A.
Time frame: Up to 8 weeks (part A)
MG-ADL Total Score Change From Baseline Over Time in Part A and Part A+B
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (no symptoms) to 24 (most severe symptoms).
Time frame: Up to 8 weeks (part A) + 3 years (part B)
MG-QoL15r Change From Baseline Over Time in Part A and Part A+B
The Myasthenia Gravis Quality of Life-15 revised (MG-QoL15r) is a patient-reported instrument that measures the impact of MG symptoms on quality of life. The total scores range from 0 (best outcome) to 30 (worst outcome).
Time frame: Up to 8 weeks (part A) + 3 years (part B)
EQ-5D-5L VAS Change From Baseline Over Time in Part A and Part A+B
The EQ-5D-5L is a participant-reported measure of health status developed by the EuroQol Group. The questionnaire comprises 5 dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Current health status is rated on vertical visual analog score (VAS) from 0 to 100, with a score of 0 corresponding to "the worst health you can imagine" and 100 corresponding to "the best health you can imagine."
Time frame: Up to 8 weeks (part A) + 3 years (part B)
Total IgG Concentrations Percent Changes From Baseline Over Time in Part A and Part A+B
Time frame: Up to 8 weeks (part A) + 3 years (part B)
This study was conducted at 109 sites across 20 countries. A total of 245 participants were screened, of whom 119 were randomized following approval by a diagnostic adjudication committee. Participants who were historically MuSK seropositive were not adjudicated. As the study is ongoing at the time of the results reporting deadline, the submitted results are limited to primary outcome and part A safety data. Remaining results (part B) will be reported within a year of global study completion.
| Milestone | Efgartigimod IV | Placebo |
|---|---|---|
| Started | 58 | 61 |
| Completed | 54 | 60 |
| Not completed | 4 | 1 |
| Withdrew: Withdrawal by subject | 2 | 0 |
| Withdrew: Meeting a protocol-specified criterion | 1 | 0 |
| Withdrew: Withdrawal of consent | 1 | 0 |
| Withdrew: Death | 0 | 1 |
The Myasthenia Gravis Activities of Daily Living (MG-ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (no symptoms) to 24 (most severe symptoms).
| points on a scale | Efgartigimod IV | Placebo |
|---|---|---|
| MG-ADL Total Score Change From Baseline | -3.35 (-3.98 to -2.72) | -1.90 (-2.51 to -1.28) |
The Quantitative Myasthenia Gravis (QMG) score includes 13 items that measure endurance or fatigability and accounts for fluctuations in disease state. The total score ranges from 0 (no symptoms) to 39 (highest disease severity).
Results for this outcome have not been posted.
A participant was an MG-ADL responder if there was a ≥2-point reduction in the MG-ADL total score compared with baseline that was maintained for at least 4 consecutive weeks (ie, at least 5 consecutive visits total), with the first reduction occurring no later than 1 week after the last administration of IMP in part A. A participant was a QMG responder if there was a ≥3-point reduction in the QMG total score compared with baseline that was maintained for at least 4 consecutive weeks (ie, at least 5 consecutive visits total), with the first reduction occurring no later than 1 week after the last administration of IMP in part A.
Results for this outcome have not been posted.
Minimal symptom expression (MSE) is defined as an MG-ADL total score of 0 or 1
Results for this outcome have not been posted.
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (no symptoms) to 24 (most severe symptoms). A participant was an MG-ADL responder if there was a ≥2-point reduction in the MG-ADL total score compared with baseline that was maintained for at least 4 consecutive weeks (ie, at least 5 consecutive visits total), with the first reduction occurring no later than 1 week after the last administration of IMP in part A.
Results for this outcome have not been posted.
The Quantitative myasthenia gravis (QMG) includes 13 items that measure endurance or fatigability and accounts for fluctuations in disease state. The total score ranges from 0 (no symptoms) to 39 (highest disease severity). A participant was a QMG responder if there was a ≥3-point reduction in the QMG total score compared with baseline that was maintained for at least 4 consecutive weeks (ie, at least 5 consecutive visits total), with the first reduction occurring no later than 1 week after the last administration of IMP in part A.
Results for this outcome have not been posted.
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (no symptoms) to 24 (most severe symptoms). An Early MG-ADL responder is an MG-ADL responder who had an onset of an MG-ADL response no later than 2 weeks after the first administration of IMP in part A.
Results for this outcome have not been posted.
The Myasthenia Gravis Activities of Daily Living (MG- ADL) scale is an 8-item instrument used to assess MG symptoms and their effects on daily activities. The total score ranges from 0 (no symptoms) to 24 (most severe symptoms).
Results for this outcome have not been posted.
The Myasthenia Gravis Quality of Life-15 revised (MG-QoL15r) is a patient-reported instrument that measures the impact of MG symptoms on quality of life. The total scores range from 0 (best outcome) to 30 (worst outcome).
Results for this outcome have not been posted.
The EQ-5D-5L is a participant-reported measure of health status developed by the EuroQol Group. The questionnaire comprises 5 dimensions: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. Current health status is rated on vertical visual analog score (VAS) from 0 to 100, with a score of 0 corresponding to "the worst health you can imagine" and 100 corresponding to "the best health you can imagine."
Results for this outcome have not been posted.
Results for this outcome have not been posted.
Collected over Available data included for Part A (up to 8 weeks).. Non-serious events are listed at a 5% frequency threshold.
| Group | Deaths | Serious | Other |
|---|---|---|---|
| Efgartigimod IV | 1/58 (1.7%) | 3/58 (5.2%) | 16/58 (27.6%) |
| Placebo | 1/61 (1.6%) | 1/61 (1.6%) | 14/61 (23%) |
| Event | Efgartigimod IV | Placebo |
|---|---|---|
| ANAEMIABlood and lymphatic system disorders | 1/58 | 0/61 |
| DIVERTICULUM INTESTINALGastrointestinal disorders | 1/58 | 0/61 |
| LOWER GASTROINTESTINAL HAEMORRHAGEGastrointestinal disorders | 1/58 | 0/61 |
| UPPER GASTROINTESTINAL HAEMORRHAGEGastrointestinal disorders | 1/58 | 0/61 |
| LOWER RESPIRATORY TRACT INFECTIONInfections and infestations | 1/58 | 0/61 |
| MYASTHENIA GRAVISNervous system disorders | 1/58 | 0/61 |
| MYASTHENIA GRAVIS CRISISNervous system disorders | 0/58 | 1/61 |
| Event | Efgartigimod IV | Placebo |
|---|---|---|
| HEADACHENervous system disorders | 3/58 | 7/61 |
| UPPER RESPIRATORY TRACT INFECTIONInfections and infestations | 5/58 | 3/61 |
| FATIGUEGeneral disorders | 2/58 | 5/61 |
| NAUSEAGastrointestinal disorders | 4/58 | 3/61 |
| URINARY TRACT INFECTIONInfections and infestations | 3/58 | 3/61 |
| Age, Continuous(Years) | Efgartigimod IV | Placebo | Total |
|---|---|---|---|
| Mean | 50.6 ± 13.44 | 51.7 ± 12.97 | 51.2 ± 13.16 |
| Sex: Female, Male(Participants) | Efgartigimod IV | Placebo | Total |
|---|---|---|---|
| Female | 44 | 46 | 90 |
| Male | 14 | 15 | 29 |
| Ethnicity (NIH/OMB)(Participants) | Efgartigimod IV | Placebo | Total |
|---|---|---|---|
| Hispanic or Latino | 4 | 2 | 6 |
| Not Hispanic or Latino | 53 | 55 | 108 |
| Unknown or Not Reported | 1 | 3 | 4 |
| Race/Ethnicity, Customized(Participants) | Efgartigimod IV | Placebo | Total |
|---|---|---|---|
| Asian | 8 | 8 | 16 |
| Black or African American | 1 | 2 | 3 |
| White | 48 | 46 | 94 |
| Other | 1 | 4 | 5 |
Documents are hosted by the registry — open the source record to download them.
This study is active, not recruiting, as verified in Nov 2025. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.
argenx