Main Inclusion Criteria:

   1. Diagnosis of Myasthenia Gravis (MG) supported by a positive serologic test for
   anti-AChR or anti-MuSK antibodies at screening.

   2. Myasthenia Gravis Foundation of America (MGFA) clinical classification II to IV at
   screening.

   3. Myasthenia Gravis Activities of Daily Living (MG-ADL) total score of 6 or greater at
   screening, with at least 4 points attributed to nonocular items.

   4. If receiving immunosuppressive drugs (ie, mycophenolate mofetil, methotrexate,
   cyclosporine, tacrolimus, cyclophosphamide), therapy must be ongoing for at least 6
   months, with stable dosing ongoing for at least 3 months before screening.
   Participants receiving azathioprine must be on a stable dose for at least 6 months
   before screening.

   5. If receiving oral corticosteroids, therapy must be ongoing for at least 3 months, with
   a stable dose at least 1 month before screening. Corticosteroids, including
   dexamethasone, must be given as oral, daily or every-other-day therapy, as opposed to
   pulse therapy.

   6. If receiving cholinesterase inhibitors, therapy with a stable dose is required at
   least 2 weeks before screening.

   7. The doses of concomitant standard background therapy must be expected to remain stable
   throughout the study unless dose reduction is required due to toxicities. Allowed
   background therapy is defined as no more than a cholinesterase inhibitor ±
   corticosteroid ± 1 steroid-sparing immunosuppressive drug (limited to azathioprine,
   mycophenolate mofetil, methotrexate, cyclosporine, tacrolimus, or cyclophosphamide).
   Participants must be on at least one allowed background medication.

Main Exclusion Criteria:

   1. Presence of a thymoma (previous history of a fully encapsulated thymoma removed ≥ 12
   months before screening is allowed) or history of invasive thymic malignancy unless
   deemed cured by adequate treatment with no evidence of recurrence for ≥ 5 years before
   screening.

   2. History of thymectomy within 12 months before screening.

   3. MGFA class I or V.

   4. Received intravenous immunoglobulin (IVIg), subcutaneous immunoglobulin (SCIg), or
   plasmapheresis/plasma exchange within 4 weeks before screening, or an expectation that
   any therapy besides the participants standard background therapies may be used for
   treatment of MG (eg, a rescue therapy) between screening and dosing.

   5. Chronic obstructive pulmonary disease (COPD) or asthma with a pre-bronchodilatory
   forced expiratory volume in 1 second (FEV1) <50% of predicted normal.

   Note: FEV1 testing is required for participants suspected of having COPD or asthma.

   6. Received rituximab, belimumab, eculizumab, or any monoclonal antibody for
   immunomodulation within 6 months before first dosing. Participants with prior exposure
   to rituximab must have CD19 counts within the normal range at screening.

   7. Known autoimmune disease other than MG that could interfere with the course and
   conduct of the study.

   8. Received a live vaccine within 4 weeks before screening or has any live vaccination
   planned during the study.

   9. Opportunistic infection ≤12 weeks before initial study dosing or currently receiving
   treatment for a chronic opportunistic infection, such as tuberculosis (TB),
   pneumocystis pneumonia, cytomegalovirus, herpes simplex virus, herpes zoster, or
   atypical mycobacteria. A mild, localized herpes simplex infection within 12 weeks of
   study dosing is allowed, as long as the lesion has resolved without systemic therapy
   prior to Day 1.