A Study of TAK-079 in People With Generalized Myasthenia Gravis

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.