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Evaluating Efgartigimod IV for Patients with Seronegative Generalized Myasthenia Gravis

A Randomized, Double-Blinded, Placebo-Controlled, Phase 3, Parallel-Group Design Study Evaluating the Efficacy and Safety of Efgartigimod IV in Adult Participants With Acetylcholine Receptor Binding Antibody Seronegative Generalized Myasthenia Gravis

Phase 3 Interventional argenx · NCT06298552

This study is testing if an intravenous treatment called efgartigimod can help adults with seronegative generalized myasthenia gravis feel better compared to a placebo.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment110 (estimated)
Ages18 Years and up
SexAll
Sponsorargenx Industry-sponsored
Locations91 sites (Scottsdale, Arizona and 90 other locations)
Trial IDNCT06298552 on ClinicalTrials.gov

What this trial studies

This study aims to assess the efficacy and safety of efgartigimod administered intravenously compared to a placebo in adults diagnosed with seronegative generalized myasthenia gravis. Participants will be randomized to receive either the treatment or placebo in the first part of the study, followed by an open-label treatment phase for those who complete the initial part. The study will also evaluate long-term efficacy, safety, and tolerability of the treatment. The goal is to provide a comprehensive understanding of how efgartigimod can impact this specific patient population.

Who should consider this trial

Good fit: Ideal candidates are adults aged 18 and older diagnosed with seronegative generalized myasthenia gravis who meet specific inclusion criteria.

Not a fit: Patients with other forms of myasthenia gravis or those who do not meet the eligibility criteria may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could significantly improve the management of seronegative generalized myasthenia gravis, offering new hope for patients with limited options.

How similar studies have performed: While this approach is novel for seronegative generalized myasthenia gravis, similar studies with efgartigimod in other conditions have shown promising results.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* The participant is at least 18 years of age and the local legal age of consent for clinical studies when signing the ICF.
* The participant is capable of providing signed informed consent and following with protocol requirements.
* The participant agrees to use contraceptive measures consistent with local regulations and the women of child-bearing potential (WOCBP) must have a negative serum pregnancy test result at screening and a negative urine pregnancy test result at baseline before receiving the study drug.
* 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:

  1. History of abnormal neuromuscular transmission demonstrated by single fiber electromyography or repetitive nerve stimulation (RNS) or is anti-muscle-specific kinase antibodies (MuSK-Ab) seropositive
  2. Either a history of positive edrophonium chloride test OR a demonstrated improvement in MG signs with treatments such as oral acetylcholinesterase (AChE) inhibitors, plasma exchange (PLEX), immunoabsorption, or intravenous immunoglobulin (IVIg)/ subcutaneous immunoglobulin (SCIg) treatment
* The participant is receiving a stable dose of MG therapy before screening that includes acetylcholinesterase (AChE) inhibitors, steroids, or nonsteroidal immunosuppressive therapies (NSISTs) in combination or alone.

Exclusion Criteria:

* Known autoimmune disease or any medical condition that would interfere with an accurate assessment of clinical symptoms of gMG or puts the participant at undue risk
* History of malignancy, cancer, unless considered cured by adequate treatment with no evidence of recurrence for ≥3 years. Adequately treated participants with the following cancers can be included at any time: Basal cell or squamous cell skin cancer, Carcinoma in situ of the cervix, Carcinoma in situ of the breast, Incidental histological findings of prostate cancer
* Clinically significant active infection that is not sufficiently resolved in the investigator's opinion or positive serum test at screening for active infection with any of the following: Hepatitis B virus (HBV), Hepatitis C virus (HCV), HIV
* Current participation in another interventional clinical study or previous participation in an efgartigimod clinical study and received at least 1 dose of the study drug
* Known hypersensitivity to study drug or one of its excipients (inactive ingredients)
* History of or current alcohol, drug, or medication abuse as assessed by the investigator
* Pregnant or lactating state or intention to become pregnant during the study
* Live or live-attenuated vaccine received \<4 weeks before screening
* Worsening muscle weakness secondary to concurrent infections or medications
* Received a thymectomy less than 3 months before screening or thymectomy is planned during the study
* Use of some medications before screening (more information is found in the protocol).

The complete list of exclusion criteria can be found in the protocol.

Where this trial is running

Scottsdale, Arizona and 90 other locations

+41 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Generalized Myasthenia Gravis
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.