A Phase 3 Study to Evaluate the Efficacy and Safety of Efgartigimod IV in Patients With Acetylcholine Receptor Binding Antibody Seronegative Generalized Myasthenia Gravis

Inclusion Criteria:

• The participant is at least 18 years of age and the local legal age of consent forclinical studies when signing the ICF.

• The participant is capable of providing signed informed consent and following withprotocol requirements.

• The participant agrees to use contraceptive measures consistent with localregulations and the women of child-bearing potential (WOCBP) must have a negativeserum pregnancy test result at screening and a negative urine pregnancy test resultat baseline before receiving the study drug.

• The participant has no known weakness in infancy and later develop fatigableweakness after aged 16 years and diagnosed with acquired gMG of both of thefollowing:

1. History of abnormal neuromuscular transmission demonstrated by single fiberelectromyography or repetitive nerve stimulation (RNS) or isanti-muscle-specific kinase antibodies (MuSK-Ab) seropositive

2. Either a history of positive edrophonium chloride test OR a demonstratedimprovement in MG signs with treatments such as oral acetylcholinesterase (AChE) inhibitors, plasma exchange (PLEX), immunoabsorption, or intravenousimmunoglobulin (IVIg)/ subcutaneous immunoglobulin (SCIg) treatment

• The participant is receiving a stable dose of MG therapy before screening thatincludes acetylcholinesterase (AChE) inhibitors, steroids, or nonsteroidalimmunosuppressive therapies (NSISTs) in combination or alone.

Exclusion Criteria:

• Known autoimmune disease or any medical condition that would interfere with anaccurate assessment of clinical symptoms of gMG or puts the participant at unduerisk

• History of malignancy, cancer, unless considered cured by adequate treatment with noevidence of recurrence for ≥3 years. Adequately treated participants with thefollowing cancers can be included at any time: Basal cell or squamous cell skincancer, Carcinoma in situ of the cervix, Carcinoma in situ of the breast, Incidentalhistological findings of prostate cancer

• Clinically significant active infection that is not sufficiently resolved in theinvestigator's opinion or positive serum test at screening for active infection withany of the following: Hepatitis B virus (HBV), Hepatitis C virus (HCV), HIV

• Current participation in another interventional clinical study or previousparticipation in an efgartigimod clinical study and received at least 1 dose of thestudy 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 theinvestigator

• 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 plannedduring the study

• Use of some medications before screening (more information is found in theprotocol).

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