in pictures and a few words
What it is and why it matters
Efgartigimod is a medicine for adults with the generalised form of myasthenia gravis, when not only the eye muscles are weak. Myasthenia gravis is a disease in which muscles poorly receive the nerve’s commands, and strength fades by evening.
- Given by drip or as an injection under the skin
- Later it was approved for one more nerve disease
What goes wrong in myasthenia
A nerve gives a muscle its command with a chemical signal. On the muscle, a kind of “socket” receives it. In myasthenia gravis the body makes antibodies — defence proteins — against this socket.
- The nerve sends the command, but nothing can receive it
- Strength is there in the morning and fades by evening
- An eyelid droops, vision doubles, chewing and swallowing are hard
Why antibodies live so long
An ordinary protein in the blood lives for hours, but antibodies live about three weeks. Cells have a service that saves them from being destroyed and sends them back into the blood.
- This makes sense: protection from infections should last
- But the service can’t tell helpful antibodies from harmful ones — it saves them all
How the medicine works
The medicine takes up all the places in this rescue service and holds on to them more tightly than ordinary antibodies. Antibodies no longer return to the blood and are broken down the usual way.
- There are fewer antibodies in the blood — harmful ones too
- The attack on the muscle “socket” weakens
Daily tasks got easier more often
In a study of adults with myasthenia gravis and antibodies against the muscle “socket”, everyday tasks became easier much more often than on a dummy treatment.
- The medicine was added to usual treatment, not used instead of it
- The main benefit is proven in people with exactly these antibodies
Tested in people. Tested in people: a study of adults with myasthenia gravis and antibodies against the muscle “socket”.
Tolerated no worse than a dummy
In the same study, there were no more unwanted effects on the medicine than on the dummy treatment. No more serious ones either.
- People stopped treatment equally often — on the medicine and on the dummy
- There were no deaths in the study
Tested in people. Tested in people: in the same study of adults with myasthenia gravis.
How treatment goes
Treatment runs in cycles: four doses, one a week, then a break. A new cycle starts when symptoms return, not by the calendar.
- An injection under the skin lowers antibodies as well as a drip
- It clears antibodies without a blood-cleaning machine
Vaccines and infections
The medicine lowers all antibodies, not just the harmful ones. So protection from infections weakens during treatment, and infections may happen more often.
- Vaccines are planned in advance, before treatment starts
- A doctor looks at any infection during treatment more carefully than usual
Important. With an active infection, treatment is put off until it clears.
Who should see a doctor first
Treatment is chosen only with a confirmed diagnosis and a known type of antibodies.
- This is planned treatment, not emergency help in a crisis — a sudden worsening
Important. Don’t stop your main treatment on your own: in studies the medicine was added to it.
In one sentence
The medicine stops the body from saving harmful antibodies — and in people with myasthenia gravis and antibodies against the muscle “socket”, everyday tasks became easier more often than on a dummy treatment.
- Overall tolerated no worse than a dummy, infections may be more frequent — vaccines in advance
Key points
Efgartigimod (Vyvgart, approved by the FDA in December 2021) is the first drug to block the FcRn receptor: it switches off the mechanism that rescues antibodies from destruction, and pathogenic antibodies are disposed of.
| Where | How it helps | What human trials showed |
|---|---|---|
| Generalised myasthenia gravis in adults with acetylcholine receptor antibodies | added to existing treatment, improves daily activities | ADAPT (Lancet Neurology, 2021), 167 patients, 77% with antibodies: an MG-ADL response in the first cycle — 68% versus 30% on placebo; odds ratio 4.95 (95% CI 2.21–11.53; p<0.0001) [1] |
| Tolerability | no worse than on placebo | in ADAPT adverse events — 77% versus 84% on placebo, serious ones 5% versus 8%; 4% in each group discontinued treatment; no deaths [1] |
| Subcutaneous form | an injection instead of an infusion | ADAPT-SC (Neurotherapeutics, 2024): non-inferior to intravenous dosing for IgG reduction [2] |
| Chronic inflammatory demyelinating polyneuropathy (CIDP) | indication extended in 2024 (ADHERE, Lancet Neurology, 2024) [3] | — |
How it helps
What Breaks in Myasthenia Gravis
A nerve commands a muscle chemically: it releases acetylcholine, and on the muscle the acetylcholine receptor — a kind of socket — receives it.
In myasthenia gravis the immune system makes antibodies against that socket. The nerve's command goes out, but there is nothing to receive it. Hence the characteristic picture: strength in the morning that fades by evening, a drooping eyelid, double vision, difficulty chewing and swallowing. In severe cases breathing is affected.
The key detail: the disease is sustained not by cells but by the antibodies themselves, circulating in the blood. So removing the antibodies helps — which is exactly the basis of plasma exchange, used in exacerbations for decades.
Why Antibodies Are So Long-Lived
An ordinary blood protein lasts hours. IgG antibodies last about three weeks. The reason is not molecular sturdiness but a separate rescue system.
Cells constantly take up whatever is in the blood, and captured proteins go for destruction. But IgG inside the cell binds the FcRn receptor, which carries it back out into the blood, past disposal.
Evolutionarily this is sensible: immune memory should last. But the system does not distinguish between an antibody protecting you from infection and one destroying your own muscle receptor. It rescues them all.
The Idea Behind the Drug
Efgartigimod is an antibody fragment altered to bind FcRn more tightly than ordinary IgG.
It occupies every rescue slot. The body's own antibodies can no longer return to the blood and are degraded by the usual route. IgG levels fall — and with them the quantity of pathogenic antibodies.
| Plasma exchange | Efgartigimod | |
|---|---|---|
| What it does | Mechanically removes antibodies from plasma | Switches off the mechanism that rescues them |
| Where it happens | In hospital, on a machine | An infusion, or an injection in subcutaneous form |
| Vascular access | Required | Not required |
| Selectivity | Removes everything | Lowers all IgG |
| Rhythm | By exacerbation | In cycles, as symptoms return |
How it is given
| Parameter | Detail |
|---|---|
| Route | Intravenous infusion or subcutaneous injection |
| Schedule | A cycle of 4 weekly administrations, then a break |
| When the next cycle starts | On returning symptoms, not by the calendar |
| Monitoring | Symptoms, IgG level, signs of infection |
| Vaccination | Planned in advance, before treatment starts |
The cyclical schedule is not a compromise but a consequence of the mechanism: the drug lowers antibody levels temporarily, the body gradually restores them, and treatment is repeated as symptoms return.
Who should see a doctor first
Who It Is Not For
▸Anyone who has had a severe allergic reaction to efgartigimod or any component of the product (anaphylaxis and a drop in blood pressure with fainting have been described). ▸Anyone with an active infection — treatment waits until it resolves. ▸As emergency care in a myasthenic crisis: this is scheduled therapy, not a resuscitation measure. ▸Anyone without a confirmed diagnosis and a defined antibody status: therapy is not chosen without them. ▸As a patient-initiated replacement for baseline therapy.
Bottom Line
▸A new point of attack: not suppressing immunity but switching off the system that prolongs antibody life. ▸Efficacy demonstrated in patients with acetylcholine receptor antibodies: 68% response versus 30% on placebo. ▸Tolerability in the trial was no worse than placebo, which is not obvious for such a mechanism. ▸The subcutaneous form replaced the infusion with an injection without losing the effect on IgG.
Treatment can be discussed at a consultation; the drug can be ordered here.
References
1. Howard JF Jr, et al. Safety, efficacy, and tolerability of efgartigimod in patients with generalised myasthenia gravis (ADAPT): a multicentre, randomised, placebo-controlled, phase 3 trial. Lancet Neurol. 2021;20(7):526–536. PMID 34146511
2. Howard JF Jr, et al. Subcutaneous efgartigimod PH20 in generalized myasthenia gravis: A phase 3 randomized noninferiority study (ADAPT-SC). Neurotherapeutics. 2024;21(5):e00378. PMID 39227284
3. Allen JA, et al. Safety, tolerability, and efficacy of subcutaneous efgartigimod in patients with chronic inflammatory demyelinating polyneuropathy (ADHERE). Lancet Neurol. 2024;23(10):1013–1024. PMID 39304241
4. VYVGART (efgartigimod alfa) — US Prescribing Information, argenx.
Caveats
What cannot be claimed yet:
▸That it is safer than classical immunosuppression over the long run — no head-to-head comparisons exist. ▸That it works in every form of myasthenia gravis: the main evidence comes from patients with acetylcholine receptor antibodies. ▸That other therapy can be stopped — in the trials efgartigimod was added to existing treatment, not substituted for it. ▸What the long-range consequences are of repeatedly lowering IgG over many years — that has not been measured on such timescales.
This material is for information only and does not replace a consultation with a doctor.
Key facts
- Efgartigimod (brand name Vyvgart, argenx) is the first drug to block the neonatal Fc receptor (FcRn); it was approved by the FDA in December 2021 for generalised myasthenia gravis.
- FcRn is the antibody recycling system: it is why IgG survives about three weeks. Efgartigimod is an antibody fragment that occupies FcRn with high affinity — so all IgG, the pathogenic ones included, begin to be degraded by the ordinary route.
- ADAPT (Lancet Neurology, 2021): 167 patients; among those with acetylcholine receptor antibodies, an MG-ADL response in the first cycle was achieved by 68% versus 30% on placebo (odds ratio 4.95; 95% CI 2.21–11.53; p<0.0001).
- Adverse events in ADAPT were not more frequent but less: 77% versus 84% on placebo, serious events 5% versus 8%, and there were no deaths; according to the US prescribing information, the drug may increase the risk of infections, so vaccinations are planned in advance.
- Treatment runs in cycles: four weekly administrations, then a break; in ADAPT-SC (Neurotherapeutics, 2024) the subcutaneous form proved non-inferior to intravenous dosing for IgG reduction, and in 2024 the indication was extended to CIDP (ADHERE, Lancet Neurology, 2024).
