A Study to Evaluate the Efficacy and Safety of IGIV-C in Symptomatic Subjects With Generalized Myasthenia Gravis

Inclusion Criteria: * Anti-acetylcholine receptor (AChR) antibody positive * Confirmed diagnosis of generalized myasthenia gravis (MG). * Myasthenia Gravis Foundation of America (MGFA) classification of Class II, III, or IVa inclusive at Screening. * QMG \>= 10 at Screening. Note: Subjects who only have a history of ocular MG may not enroll. * Receiving standard of care MG treatment at a stable dose consisting of any one of the following for the time intervals delineated below (time intervals apply to medications and maintenance of stable dose level): 1. Cholinesterase inhibitor (pyridostigmine or equivalent) for at least 2 weeks prior to Screening and no immunosuppressants 2. Cholinesterase inhibitor (pyridostigmine or equivalent) for at least 2 weeks prior to Screening AND/OR only one of the following: 1. Prednisone (up to 60 mg/day or equivalent) for at least 2 months prior to Screening, OR 2. Azathioprine for at least 6 months prior to Screening, OR 3. Mycophenolate mofetil for at least 6 months prior to Screening, OR 4. Methotrexate for at least 6 months prior to Screening, OR 5. Cyclosporine or tacrolimus for at least 3 months prior to Screening 3. Cholinesterase inhibitor (pyridostigmine or equivalent) for at least 2 weeks prior to Screening AND/OR prednisone (up to 60 mg/day or equivalent) for at least one month prior to Screening and only one of the following: 1. Azathioprine for at least 6 months prior to Screening, OR 2. Mycophenolate mofetil for at least 6 months prior to Screening, OR 3. Methotrexate for at least 6 months prior to Screening, OR 4. Cyclosporine or tacrolimus for at least 3 months prior to Screening Exclusion Criteria: * Have received cyclophosphamide or any other immunosuppressive agent apart from the ones allowed per inclusion criteria within the past 6 months * Any change in MG treatment regimen between Screening (Week -3, Visit 0) and Baseline (Week 0, Visit 1) * Greater than two point change in QMG score, increased or decreased, between Screening (Week -3, Visit 0) and Baseline (Week 0, Visit 1) * Any episode of myasthenic crisis in the one month prior to Screening * Evidence of malignancy within the past 5 years (non-melanoma skin cancer, carcinoma in situ of cervix is allowed) or thymoma potentially requiring surgical intervention during the course of the trial (intent to perform thymectomy) * Thymectomy within the preceding 6 months * Rituximab, belimumab, eculizumab or any monoclonal antibody used for immunomodulation within the past 12 months * Have received immune globulin (Ig) treatment given by intravenous (IV), subcutaneous, or intramuscular route within the last 3 months * Current known hyperviscosity or hypercoagulable state * Currently receiving anti-coagulation therapy (vitamin K antagonists, nonvitamin K antagonist oral anticoagulants \[e.g., dabigatran etexilate, rivaroxaban, edoxaban, and apixaban\], parenteral anticoagulants \[e.g., fondaparinux\]). Note that oral anti-platelet agents are allowed (e.g., aspirin, clopidogrel, ticlodipine) * Documented diagnosis of thrombotic complications to polyclonal intravenous immunoglobulin (IVIg) therapy in the past * History of recent (within the last year) myocardial infarction or stroke * Uncontrolled congestive heart failure; embolism; or historically documented (within the last year) electrocardiogram (ECG) changes indicative of myocardial ischemia or atrial fibrillation * History of chronic alcoholism or illicit drug abuse (addiction) in the 12 months preceding the Screening/Week -3 (Visit 0) * Plasma exchange (PLEX) performed within the last 3 months * Renal impairment (i.e., serum creatinine exceeds more than 1.5 times the upper limit of normal \[ULN\] for the expected normal range for the testing laboratory). * Hemoglobin levels less than 9 g per dL