A Randomized, Double-Blind, Placebo-Controlled, Multicenter Phase 3 Trial to Evaluate the Efficacy,
Safety and Tolerability of ARGX-113 in Patients with Myasthenia Gravis Having Generalized Muscle
Weakness.

Generalized myasthenia gravis (gMG) is an autoimmune disorder. It is caused by
an error in the transmission of nerve impulses to muscles. It occurs when
normal communication between the nerve and muscle is interrupted at the
neuromuscular junction (the place where nerve cells connect with the muscles
they control). The treatment of gMG is based on a variety of medications and
medical procedures used either alone or in combination. Since the majority of
already existing treatment options can give side-effects in patients while not
always giving the symptom control needed there is room for improvement.
ARGX-113 wants to be an alternative or addition to the existing therapies
offering more specific modulation of the immune system with less side-effects.

A previous study with ARGX-113 involving 24 patients diagnosed with gMG, has
shown that 75% of the patients treated with ARGX-113 experienced relief in
their symptoms for at least 6 weeks compared with only 25% of patients who
received a placebo.

Primary Objective:
- Efficacy of ARGX-113 as assessed by the percentage of "Myasthenia Gravis
Activities of Daily Living (MG-ADL) responders" in the acetylcholine receptor
(AChR)- antibody (Ab) seropositive population.

Secondary Objectives:
1. Efficacy of ARGX-113 as assessed by the percentage of "QMG responders" in
the AChR-Ab seropositive population.
2. Efficacy of ARGX-113 as assessed by the percentage of "MG-ADL responders" in
the overall population (AChR-Ab seropositive and AChRAb
seronegative patients).
3. Efficacy of ARGX-113 as assessed by the percentage of time that patients
show a "clinically meaningful improvement" in total MG-ADL
score during the trial in the AChR-Ab seropositive population.
4. Duration of response
5. Onset of efficacy of ARGX-113 as assessed by the percentage of "early MG-ADL
responders" in the AChR-Ab seropositive population.
6. Safety and tolerability of ARGX-113 in the overall population and in
subgroups.

This is a randomized, double-blind, placebo-controlled, multicenter Phase 3
trial to evaluate the efficacy, safety, tolerability, quality of life and
impact on normal daily activities of ARGX-113 in patients with gMG.

The patient will be randomly assigned to 1 of the following treatment groups:
* The study drug ARGX-113 (10 milligrams per kilogram of body weight [10
mg/kg], with a maximum of 1200 mg)
* Placebo

For full details see table 1 in the protocol (schedule of assessments) page
13-16

The patient participation in this study will last approximately 28 weeks.
During this time the patient will visit the hospital approximately 19 times.
The screening visit and the treatment visits will take about 3-4 hours. The
other hospital visits will take about 2 hours.

During these visits the following tests and procedures will take place:
- physical examinations will be done and questions will be asked about medical
history.
- ECGs will be done
- weight, height, blood pressure, temperature, heartbeat will be measured
- blood and urine sampling will be taken.
- The research physician will also test female pa rticipants of childbearing
potential for pregnancy.
- Subjects need to complete several questionnaires that will evaluate the
Efficacy and quality of life and for an Suicidality assessment

Possible side effects that are already known are described in the IB and
patient information letter.