For all arms: - Medically stable on the basis of physical examination, medical history, vital signs, clinical laboratory tests, and 12-lead electrocardiogram (ECG) performed at screening - Diagnosis of myasthenia gravis (MG) with generalized muscle weakness meeting the clinical criteria for generalized MG (gMG) as defined by the Myasthenia gravis foundation of America (MGFA) clinical classification class II a/b, III a/b, or IV a/b at screening and positive for acetylcholine receptor (AChR) antibodies - Myasthenia Gravis-Activities of Daily Living (MG-ADL) score of greater than or equal to (>=) 5 with less than (<) 50% of symptoms coming from ocular MG-ADL sub-scores at study screening and baseline (Day 1) visits Criteria specific to Arms 1 and 2 only: - Has suboptimal response to current stable therapy for gMG according to the investigator or has discontinued corticosteroids and/or immunosuppressants/immunomodulators including eculizumab or other novel approved immune agents at least 4 weeks prior to baseline due to intolerance or lack of efficacy Criteria specific to Arm 3: - Treatment with efgartigimod IV or subcutaneous (SC) for >=1 cycle, and the final cycle is consistent with local label

• Any confirmed or suspected clinical immunodeficiency syndrome not related to treatment of his/her gMG, or has a family history of congenital or hereditary immunodeficiency unless confirmed absent in the participant - Had a thymectomy within 1 year prior to baseline, or thymectomy is planned during the study - Currently has a malignancy or has a history of malignancy within 3 years before baseline Criteria specific to Arms 1 and 2 only: - Has received treatment for MG with an FcRn-targeting therapy Criteria specific to Arm 3 only: - Is currently taking IgG monoclonal antibody therapeutics, or Fc-conjugated therapeutic agents, including factor or enzyme replacement, with the exception of efgartigimod