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