This study is an open label, single center, prospective, 26 weeks study with descriptive analysis where IVIG is replaced by efgartigimod therapy. MG-ADL and MGQOL evaluations will occur weekly throughout the study to week 26.

Objectives:

To determine if efgartigimod is equivalent or non-inferior in efficacy to IVIG in the treatment of stable, acetylcholine receptor antibody positive, IVIG dependent myasthenia gravis patients.

To determine patient treatment preference between IVIG and efgartigimod in stable, IVIG dependent acetylcholine receptor antibody positive myasthenia gravis patients.

To determine the safety and tolerability of efgartigimod administered in a fixed regular dosing regimen over 6 months in stable IVIG dependent acetylcholine receptor antibody positive myasthenia gravis patients.

IVIG will be discontinued one week prior to the baseline visit (week 0) while other concurrent medications (non-steroidal immunosuppressive therapies (NSISTs), acetylcholinesterase (AChE) inhibitors or corticosteroids) for myasthenia will be kept unchanged for the duration of the study. The dose and frequency of efgartigimod treatment will be 10mg/kg (max of 1200mg) administered as a one-hour intravenous infusion every week x 4 infusions followed by a four-week break and repeated for a total four treatment cycles till week 24 and then followed by a two-week observation with an end of study visit at week 26.

Inclusion Criteria:

• 1. Signed informed consent. 2. Age 18-80 years 3. Acetylcholine receptor antibody positive, myasthenia gravis patients, with stable disease for the past four or more months. Stable disease is defined as no change in dosage or interval in IVIG treatments and without any significant change in clinical status.

  4. No modification or addition of NSISTs in the past six months 5. No modification or addition in corticosteroid therapy for the past three months 6. Myasthenia Gravis diagnosis was supported by abnormal neurotransmission test or history of improvement with AChE inhibitors.

  7. Receiving chronic regular IVIG treatments for myasthenia gravis for the past year or more.

Exclusion Criteria:

• 1. Patients with previous rituxan or eculizumab treatment or plasma exchange within the past six months 2. Patients with previous thymectomy within the past 3months 3. Patients that have active Hepatitis B, are seropositive for Hepatitis C or HIV or have latent, untreated or active TB or any other significant active infection 4. Patients that have at screening a serum IgG less than 6.0gm/L or a history of chronic hypogammaglobulinemia from any cause.

  5. Patients that are pregnant or considering becoming pregnant in the next 6 months.

  6. Patients with severe renal impairment (eGFR less than 30ml/min) 7. Patients who in the opinion of the investigator should not participate in the study.