Efficacy and Safety of IGIV-C in Corticosteroid Dependent Patients With Generalized Myasthenia Gravis

Inclusion Criteria: * Anti-acetylcholine receptor antibody positive * Confirmed diagnosis of generalized MG historically meeting the clinical criteria for diagnosis of MG defined by the Myasthenia Gravis Foundation of America (MGFA) classification of Class II, III, IV, or V historically * At Screening, subjects may have symptoms controlled by CS or were MGFA Class II-IVa inclusive (Class IVb and Class V excluded). Subjects who only have a history of ocular MG may not enroll. * On systemic CS for a minimum period of at least 3 months and on a stable CS dose of \>=15 mg/day and \<=60 mg/day (prednisone equivalent) for the month prior to Screening. * Had a tapering CS dose that the study investigator considered to be appropriate. * At least 1 previous completed attempt to taper CS in order to minimize CS dose (lowest feasible dose based on observed MG signs and symptoms) Exclusion Criteria: * Any dose change in concomitant immunosuppressant therapy, other than CS, in the prior 6 months * Any change in CS dose or acetylcholinesterase inhibitor (e.g., pyridostigmine) dose in the 1 month prior to Screening * A 3-point change in Quantitative Myasthenia Gravis score, increased or decreased, between the Screening/Week -3 (Visit 0) and Baseline (Week 0 \[Visit 1\]) * Any episode of myasthenic crisis (MC) in the 1 month prior to Screening, or (at any time in the past) MC or hospitalization for MG exacerbation associated with a previous CS taper attempt * 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 prior to Screening * Rituximab, belimumab, eculizumab or any monoclonal antibody used for immunomodulation within the past 12 months prior to Screening * Have received immune globulin treatment given by IV, subcutaneous, or intramuscular route within the last 3 months prior to Screening * Received plasma exchange performed within the last 3 months prior to Screening * History of anaphylactic reactions or severe reactions to any blood-derived product * History of recent (within the last year) myocardial infarction or stroke * Uncontrolled congestive heart failure; embolism; or historically documented (within the last year) electrocardiogram changes indicative of myocardial ischemia or atrial fibrillation * Current known hyperviscosity or hypercoagulable state * Currently receiving anti-coagulation therapy. Oral anti-platelet agents are allowed (e.g., aspirin, clopidogrel, ticlopidine) * Females of child-bearing potential who are pregnant, have a positive serum pregnancy test, breastfeeding, or are unwilling to practice a highly effective method of contraception throughout the study. * Renal impairment * Aspartate aminotransferase or alanine aminotransferase levels exceeding more than 2.5 times the upper limit of normal for the expected normal range for the testing laboratory. * Hemoglobin (Hb) levels \<9 g/dL