Efgartigimod Alfa

Efgartigimod alfa is a prescription medicine for autoimmune diseases in which the body makes harmful antibodies against itself. It does not touch the cells that make those antibodies. Instead it blocks a receptor called the neonatal Fc receptor (FcRn), which normally rescues one class of antibody, immunoglobulin G (IgG), from being broken down. With the neonatal Fc receptor blocked, the body clears its immunoglobulin G faster, and the level in the blood falls — the harmful autoantibodies along with the useful ones.

It was the first medicine of this kind to be approved anywhere. This page explains how the recycling system works and how it was discovered, the approvals by the United States Food and Drug Administration (FDA), the European Medicines Agency (EMA) and Japan, what each main trial found — including the trials that found no benefit — the side effects and safety facts on the label, and the other medicines in the same class. The Myasthenia Gravis and Chronic Inflammatory Demyelinating Polyneuropathy pages describe the diseases themselves; the Edelman and Porter page explains the antibody structure this drug is built from.

Table of Contents

  1. What Efgartigimod Alfa Is
  2. How the Antibody Recycling System Works
  3. From a 1964 Theory to a Drug Target
  4. The First Studies in People
  5. The Approvals and Their Dates
  6. Generalized Myasthenia Gravis Trials
  7. The Under-the-Skin Form With Hyaluronidase
  8. Chronic Inflammatory Demyelinating Polyneuropathy Trials
  9. Immune Thrombocytopenia: One Positive and One Null Trial
  10. Pemphigus: An Early Signal and a Null Phase 3 Trial
  11. Other Diseases Under Study
  12. Side Effects and Infections
  13. Vaccines and Other Antibody Medicines
  14. Pregnancy
  15. Other Medicines That Block the Same Receptor
  16. What Is Not Known
  17. Key Research Papers
  18. Connections
  19. Featured Videos

What Efgartigimod Alfa Is

An antibody is shaped like the letter Y. The two arms grab a target; the stem, called the Fc region (the “fragment, crystallizable”), is the part the body’s own receptors hold on to. Efgartigimod alfa is only the stem. The United States label describes it as a fragment of human immunoglobulin G1, made of two identical protein chains of 227 amino acids each, joined together, with a weight of about 54 kilodaltons — roughly a third of a whole antibody. It is produced in cultured hamster ovary cells, the standard factory cell for antibody medicines.

The stem has been engineered with a few changed amino acids so that it sticks to the neonatal Fc receptor much more tightly than a natural antibody does. The researchers who tested it in people for the first time described it as an engineered fragment that competes with the body’s own immunoglobulin G for the receptor. Because it has no arms, it does not bind any target of its own; its whole job is to occupy the receptor.

It is given in two ways. One version is a drip into a vein. The other is an injection under the skin, mixed with an enzyme called hyaluronidase that loosens the tissue under the skin for a day or two so a larger volume can be absorbed. The word “alfa” in the name only marks it as a manufactured protein; the United States label adds a four-letter suffix to the name of each version, as it does for all biological medicines.

How the Antibody Recycling System Works

Immunoglobulin G survives in the blood far longer than most other proteins, and the reason is the neonatal Fc receptor. Cells lining the blood vessels constantly swallow small sips of blood plasma into tiny bubbles inside the cell. As the bubble turns acidic, the neonatal Fc receptor grabs any immunoglobulin G inside it by the stem. Whatever the receptor holds is carried back to the cell surface and released into the blood again. Whatever it does not hold goes on to the cell’s recycling bin, the lysosome, and is broken down.

The same receptor has a second job, which gave it its name. In the placenta, and in the gut of newborn rats, it carries the mother’s immunoglobulin G across to the baby, which is how a newborn starts life with its mother’s protection.

Efgartigimod alfa fills the receptor so that it can no longer rescue the body’s own immunoglobulin G. The immunoglobulin G then goes to the lysosome and is broken down, and the level in the blood falls within days. The drug lowers all immunoglobulin G, whatever it is aimed at: the autoantibodies that cause the disease, and the protective antibodies left by past infections and vaccines. In the first study in people it did not change the other antibody classes, such as immunoglobulin A and immunoglobulin M. Once the drug is stopped, the level climbs back as the body’s antibody-making cells, which were never touched, keep producing.

From a 1964 Theory to a Drug Target

In 1964 the biologist F. W. R. Brambell and two colleagues published a theoretical model in Nature to explain two puzzles: why immunoglobulin G survives so much longer in the blood than other proteins, and why it is broken down faster when its level is high. Brambell proposed that cells carry a limited number of “protection receptors” that catch immunoglobulin G and return it to the blood; when the receptors are full, the extra immunoglobulin G is destroyed. He later described a similar, saturable receptor carrying antibodies across the newborn gut.

The gut receptor was found first. In 1989 Simister and Mostov purified the Fc receptor from the gut lining of newborn rats, cloned its gene, and showed that it is built like the class I major histocompatibility complex proteins that display fragments of protein to the immune system, paired with a small protein called beta-2-microglobulin. They wrote that this was the first time a function had been assigned to a molecule related to those proteins.

In 1996 Junghans and Anderson showed that the two receptors Brambell had imagined were the same molecule. In mice whose gene for this receptor system had been knocked out, immunoglobulin G was broken down 10 times faster and its level was correspondingly lower, while immunoglobulin A was unchanged. The receptor that ferries antibodies to the newborn turned out to be the receptor that protects immunoglobulin G throughout life.

Engineers then learned to change how tightly an antibody stem holds the receptor. In 1997 a team increased the receptor grip of a mouse antibody fragment by changing amino acids at three positions near the receptor contact site and found that the fragment lasted longer in mice’s blood. In 2005 Vaccaro, Ward and colleagues went the other way: they engineered a human antibody stem to bind the receptor with higher affinity and less dependence on acidity, so that it held on and would not let go. In mice it blocked the receptor and caused a rapid fall in the animals’ own immunoglobulin G. The authors named such blockers “Abdegs”, for antibodies that enhance immunoglobulin G degradation, and suggested they might be useful in antibody-driven diseases. Efgartigimod alfa is a molecule of this kind.

The First Studies in People

The first study in humans, published in 2018, was a randomized, double-blind, placebo-controlled trial in 62 healthy volunteers who received rising single and repeated doses by vein. A single dose lowered immunoglobulin G by up to 50%; repeated dosing lowered it by an average of 75% from the starting level. About 8 weeks after the last dose, immunoglobulin G had returned to its starting level. The drug did not change albumin, the blood’s main protein, or the antibody classes other than immunoglobulin G, and no serious side effects related to the infusions were seen. Cynomolgus monkeys given the drug showed the same fast, specific fall in immunoglobulin G.

A small phase 2 trial in generalized myasthenia gravis followed, published in 2019. Twenty-four adults with antibodies against the acetylcholine receptor, the muscle receptor that myasthenia gravis attacks, were randomized, 12 to the drug and 12 to placebo, on top of their usual treatment. The trial gave 4 doses of 10 mg per kilogram of body weight over 3 weeks. There were no serious or severe side effects. Every treated patient had a rapid fall in total immunoglobulin G and in the acetylcholine receptor antibodies, and 75% showed a rapid and long-lasting improvement on all four disease scales used.

The Approvals and Their Dates

These are regulatory facts, taken from the FDA’s own announcement and database, the EMA’s public assessment page and a published approval summary.

The current European authorisation, per the EMA page, covers adults with generalized myasthenia gravis who have acetylcholine receptor antibodies, given as an add-on to standard treatment, by vein or under the skin, and the under-the-skin form on its own for adults with progressive or relapsing chronic inflammatory demyelinating polyneuropathy after earlier treatment with corticosteroids or immunoglobulins.

Generalized Myasthenia Gravis Trials

In myasthenia gravis the immune system makes antibodies that block the signal from nerve to muscle, so muscles tire and weaken with use — drooping eyelids, double vision, trouble swallowing, weak arms and legs, and in a crisis, weak breathing muscles. “Generalized” means it reaches beyond the eye muscles.

ADAPT, the phase 3 trial

ADAPT, published in The Lancet Neurology in 2021, enrolled 167 adults at 56 centres in 15 countries in North America, Europe and Japan, all already on at least one myasthenia gravis treatment. They were randomized to the drug or placebo, given as 4 weekly infusions per cycle; the trial gave 10 mg per kilogram, and further cycles were given only when symptoms returned, no sooner than 8 weeks after the previous cycle began. 129 of the patients (77%) had acetylcholine receptor antibodies. Among them, 44 of 65 on the drug (68%) were responders in the first cycle — at least a 2-point improvement on the Myasthenia Gravis Activities of Daily Living scale, held for at least 4 weeks — compared with 19 of 64 on placebo (30%).

Side effects were reported in 77% of the drug group and 84% of the placebo group. The most common were headache (29% versus 28%) and colds (12% versus 18%). Serious side effects occurred in 5% on the drug and 8% on placebo. There were no deaths.

Long-term and dosing studies

In the open-label extension ADAPT+, 145 people received the drug, for a mean of 548 days of study time and up to 17 treatment cycles. Improvement appeared as early as one week after the first infusion, in people with and without acetylcholine receptor antibodies. People with these antibodies who were followed for at least a year needed a median of 5 cycles a year. The most common side effects were headache (24.8%), COVID-19 (15.2%) and colds (13.8%). Because this extension had no placebo group, it shows how the drug performed over time, not how it compared with no drug.

ADAPT NXT, a smaller open-label trial in 69 adults with acetylcholine receptor antibodies, compared fixed cycles with an infusion every other week after a first cycle. Both schedules gave similar improvements over 21 weeks, and minimal symptoms (a daily living score of 0 to 1) were reached by 47.1% and 44.2% of participants.

Myasthenia gravis without acetylcholine receptor antibodies

Some people with generalized myasthenia gravis have no acetylcholine receptor antibodies. The current United States label describes a randomized, double-blind, placebo-controlled study in 119 such adults: 61% had none of the three known myasthenia gravis antibodies, 34% had antibodies against a muscle protein called muscle-specific tyrosine kinase, and 5% had antibodies against a protein called LRP4. After 4 weekly infusions, the daily living score improved more on the drug than on placebo, by an average of 1.46 points, a statistically significant difference.

The Under-the-Skin Form With Hyaluronidase

An infusion by vein takes about an hour at a clinic. The under-the-skin form combines the drug with a version of the human hyaluronidase enzyme called PH20. Hyaluronidase breaks down hyaluronan, the gel between cells under the skin; the label states the effect is temporary and the tissue recovers within 24 to 48 hours.

The ADAPT-SC trial compared the two forms in adults with generalized myasthenia gravis. One group was given 4 weekly injections of 1,000 mg under the skin, the other 4 weekly infusions of 10 mg per kilogram by vein. The main measure was the fall in total immunoglobulin G after 4 weeks, and the injection was found to be no worse than the infusion. Symptom improvement appeared as early as one week in both groups and peaked at week 4, and the long-term extension found results like those of ADAPT. Approval of the injection was based on matching the drug effect of the infusion, not on a new placebo-controlled trial.

The current United States label lists a prefilled syringe that a patient or caregiver can inject, given over 20 to 30 seconds, and a vial given by a health professional through a small needle set over 30 to 90 seconds. Injection site reactions occurred in at least 15% of people with myasthenia gravis and chronic inflammatory demyelinating polyneuropathy who were given this form.

Chronic Inflammatory Demyelinating Polyneuropathy Trials

In chronic inflammatory demyelinating polyneuropathy, the immune system damages the myelin coating of the nerves in the arms and legs, causing weakness and numbness that slowly worsen or come and go. The usual treatments are corticosteroids, immunoglobulin from donated blood, and plasma exchange. The ADHERE paper notes that around a third of patients do not respond to the current treatments.

ADHERE

ADHERE, published in The Lancet Neurology in 2024, was a phase 2 trial at 146 sites in Asia-Pacific, Europe and North America. People whose disease had clearly worsened entered stage A and were given 1,000 mg under the skin every week for up to 12 weeks, without a placebo group. Of 322 participants, 214 (66%) showed confirmed improvement. In stage B, 221 of those who improved were randomized to keep taking the drug or to switch to placebo for up to 48 weeks. Relapse occurred in 31 of 111 on the drug (27.9%) and in 59 of 110 on placebo (53.6%), a hazard ratio of 0.39 for relapse.

Side effects were reported in 63% of people in stage A, with serious ones in 7%. In stage B they occurred in 64% on the drug and 56% on placebo, and serious ones in 5% of each group. There were three deaths: two in stage A, which the investigators judged not related or unlikely to be related to the drug, and one in the placebo group.

A design point matters here. ADHERE tested whether people who had already responded to the drug did better staying on it than coming off it. It did not compare the drug with immunoglobulin, corticosteroids or plasma exchange, and the authors wrote that further studies are needed on longer-term effects and on how it compares with the existing treatments.

ADHERE+

An interim report of the open-label extension, published in 2026, covered 228 people with up to 187.3 weeks of treatment (mean 58.0 weeks). Longer exposure did not increase the rate of side effects (75.0%) or of severe ones (18.0%), and infections stayed infrequent regardless of immunoglobulin G level. People who had responded in stage A showed lasting improvement in disability scores and in grip strength (17.5 kilopascals) at week 36 of the extension, whichever group they had been in during stage B.

Immune Thrombocytopenia: One Positive and One Null Trial

In primary immune thrombocytopenia, antibodies mark the blood’s platelets for destruction, so the platelet count falls and bruising and bleeding follow. The Thrombocytopenia page covers the condition.

ADVANCE IV, by vein

ADVANCE IV, published in The Lancet in 2023, randomized 131 adults (86 to the drug, 45 to placebo) at 71 sites in Asia, Europe and North America. They had long-standing disease — a mean of 10.6 years since diagnosis — and 67% had already had at least three earlier treatments. The trial gave 10 mg per kilogram by vein. Among those with chronic disease, 17 of 78 on the drug (22%) reached a sustained platelet response, a count of at least 50,000 for at least 4 of the last 6 weeks, compared with 2 of 40 on placebo (5%). The most common side effects in both groups were headache (16% versus 13%), blood in the urine (16% versus 16%) and pinpoint skin bleeds (15% versus 27%).

ADVANCE SC, under the skin

The under-the-skin form did not repeat that result. ADVANCE SC, published in 2026, randomized 207 adults, two to one, to 1,000 mg weekly or placebo; most (92.8%) had chronic disease and 74.9% had had at least three earlier treatments. The primary goal was reached by 17 of 124 on the drug (13.7%) and 11 of 68 on placebo (16.2%), so superiority was not shown for the primary or any secondary goal. The authors reported that platelet counts rose more than expected on placebo and less than expected on the drug. Side effects were mostly mild to moderate and similar between groups.

None of the United States labels lists immune thrombocytopenia as a use.

Pemphigus: An Early Signal and a Null Phase 3 Trial

Pemphigus vulgaris and pemphigus foliaceus are blistering diseases in which immunoglobulin G antibodies attack desmogleins, the proteins that hold skin cells together. The Pemphigus Vulgaris page describes them.

An open-label phase 2 trial, published in 2022, enrolled 34 people with mild to moderate disease. Disease control came early in 28 of 31 (90%), after a median of 17 days, and with longer treatment plus a low dose of prednisone, 14 of 22 (64%) reached complete clinical remission within 2 to 41 weeks. There was no placebo group.

The phase 3 trial, ADDRESS, published in October 2026, was randomized and double-blind. It enrolled 222 people with moderate to severe pemphigus at 82 sites in 20 countries; everyone took prednisone, and 147 also received the drug under the skin while 75 received placebo. By week 30, complete remission on a low prednisone dose was reached by 44 of 124 with pemphigus vulgaris on the drug (35.5%) and 20 of 66 on placebo (30.3%), a difference that was not statistically significant. Total prednisone use was the same in both groups. The drug lowered total immunoglobulin G and the anti-desmoglein antibodies quickly, but this did not translate into better skin scores. Side effects occurred in 89.1% on the drug and 76.0% on placebo; serious ones in 12.2% and 13.3%. No one died. The authors concluded that the drug did not show clinical benefit over corticosteroids alone at 30 weeks.

Other Diseases Under Study

The 2022 approval summary listed trials of the drug in bullous pemphigoid, chronic inflammatory demyelinating polyneuropathy, immune thrombocytopenia, autoimmune myositis and pemphigus. The Bullous Pemphigoid page notes the class as a possible approach in that disease.

In Sjögren’s disease, which dries the eyes and mouth, a small phase 2 proof-of-concept trial published in 2026 randomized 34 adults to weekly infusions or placebo for 24 weeks. On a composite of five measures, 45.5% on the drug responded on at least three, against 11.1% on placebo. The trial was not designed to test a formal statistical hypothesis, and the authors called for a phase 3 trial. Side effects were reported in 87.0% on the drug and 63.6% on placebo, all mild or moderate.

The range of diseases tried follows from the mechanism: the drug lowers immunoglobulin G as a whole, and each of these diseases involves immunoglobulin G autoantibodies. The null pemphigus and under-the-skin thrombocytopenia trials show that lowering the antibodies does not always improve the disease.

Side Effects and Infections

The United States label lists the most common side effects in myasthenia gravis, seen in at least 10% of patients, as respiratory tract infections, headache and urinary tract infection. In the main myasthenia gravis study described on the label, urinary tract infections occurred in 10% on the drug versus 5% on placebo, and respiratory tract infections in 33% versus 29%. Below-normal white blood cell counts were more frequent on the drug (12% versus 5%), as were low lymphocyte counts (28% versus 19%) and low neutrophil counts (13% versus 6%); most infections and blood count changes were mild to moderate.

The label lists three warnings:

The EMA summary lists injection site reactions such as rash, itching and pain, and infections of the nose and throat, as affecting more than 1 in 10 people, and urinary tract infections as affecting up to 1 in 10.

A pooled 2025 analysis of 715 people in trials of myasthenia gravis, immune thrombocytopenia and chronic inflammatory demyelinating polyneuropathy, covering more than 850 years of follow-up, found that rates of severe and serious infections were comparable between the drug and placebo, and that side effects did not rise with longer use. The drug did not lower albumin or raise LDL cholesterol in that analysis. Hospitals treat signs of serious infection — high fever, shortness of breath, confusion — and signs of anaphylaxis, such as throat swelling or trouble breathing, as urgent.

Vaccines and Other Antibody Medicines

Because the drug lowers all immunoglobulin G, it also lowers the protective antibodies from past vaccines. A 2022 study measured this in people with pemphigus and myasthenia gravis. Antibodies against tetanus, chickenpox-shingles virus and pneumococcus fell to about the same degree as total immunoglobulin G, but tetanus and chickenpox-shingles antibodies stayed above the minimum protective level in most patients (10 of 12, or 83%, and 14 of 15, or 93%). Protective antibodies returned to their starting levels after treatment stopped. People with myasthenia gravis who received flu, pneumococcal or COVID-19 vaccines while on the drug still made new antibodies against them.

A 2026 phase 1 trial gave healthy adults a 23-type pneumococcal polysaccharide vaccine either just before the last of 4 weekly infusions, 2 weeks after it, or with placebo. All groups made new antibodies against all 23 types, even when the vaccine was given at the lowest point of immunoglobulin G; a normal response was seen in 9 of 10, 6 of 11 and 4 of 12 participants respectively. This was an exploratory study with small groups.

The United States label states that live vaccines are not recommended during treatment, and its instructions are to review age-appropriate vaccines before a new treatment cycle. It also warns that the drug may lower the levels and effect of other medicines that rely on the same receptor — immunoglobulin from donated blood, monoclonal antibodies, and other drugs containing a human immunoglobulin G stem. A practical consequence noted on the label is that such medicines may need close monitoring for reduced effect when given together.

Pregnancy

The United States label states that there are no available data on the use of efgartigimod alfa during pregnancy. In rats and rabbits given doses by vein of up to 100 mg per kilogram a day throughout organ formation — 3 and 10 times the human dose by weight — there were no adverse effects on the developing young. A pregnancy exposure registry follows outcomes in people treated while pregnant, and the EMA lists a worldwide post-authorisation safety study of mothers, fetuses and infants exposed in pregnancy or breastfeeding.

The label explains two expected effects. Antibody medicines cross the placenta more as pregnancy goes on, mostly in the third trimester, so the drug may reach the fetus. And because it lowers the mother’s immunoglobulin G, the newborn is expected to receive less of the mother’s protective antibodies; the label notes that the risks and benefits of live vaccines in infants exposed in the womb are weighed for this reason.

A 2023 review of myasthenia gravis in pregnancy, written by specialists, placed efgartigimod with other monoclonal antibody drugs as treatments its authors would use in pregnancy only when strictly necessary, and described immunoglobulin from donated blood and plasma exchange as safe during pregnancy. The same receptor biology is being used on purpose in a different setting: a related FcRn blocker, nipocalimab, was given in a 2024 trial to block the transfer of harmful maternal antibodies to the fetus (see below).

Other Medicines That Block the Same Receptor

Efgartigimod alfa was the first FcRn blocker approved. The three below are monoclonal antibodies aimed at the receptor, rather than antibody stems; the batoclimab trial, for example, describes it as a fully human anti-FcRn monoclonal antibody.

All four lower immunoglobulin G by the same route, so the infection, vaccine and drug-interaction points above apply to the class as a whole. They differ in structure and in how they are given.

What Is Not Known

Decisions about medicines for these diseases belong with the treating specialist.

Key Research Papers

  1. Brambell FW, Hemmings WA, Morris IG. A theoretical model of gamma-globulin catabolism. Nature. 1964;203:1352-4. PubMed PMID: 14207307
  2. Simister NE, Mostov KE. An Fc receptor structurally related to MHC class I antigens. Nature. 1989;337(6203):184-7. PubMed PMID: 2911353
  3. Junghans RP, Anderson CL. The protection receptor for IgG catabolism is the beta2-microglobulin-containing neonatal intestinal transport receptor. Proc Natl Acad Sci U S A. 1996;93(11):5512-6. PubMed PMID: 8643606
  4. Ghetie V, Popov S, Borvak J, Radu C, Matesoi D, Medesan C, et al. Increasing the serum persistence of an IgG fragment by random mutagenesis. Nat Biotechnol. 1997;15(7):637-40. PubMed PMID: 9219265
  5. Vaccaro C, Zhou J, Ober RJ, Ward ES. Engineering the Fc region of immunoglobulin G to modulate in vivo antibody levels. Nat Biotechnol. 2005;23(10):1283-8. PubMed PMID: 16186811
  6. Ulrichts P, Guglietta A, Dreier T, van Bragt T, Hanssens V, Hofman E, et al. Neonatal Fc receptor antagonist efgartigimod safely and sustainably reduces IgGs in humans. J Clin Invest. 2018;128(10):4372-4386. PubMed PMID: 30040076
  7. Howard JF Jr, Bril V, Burns TM, Mantegazza R, Bilinska M, Szczudlik A, et al. Randomized phase 2 study of FcRn antagonist efgartigimod in generalized myasthenia gravis. Neurology. 2019;92(23):e2661-e2673. PubMed PMID: 31118245
  8. Howard JF Jr, Bril V, Vu T, Karam C, Peric S, Margania T, 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. PubMed PMID: 34146511
  9. Heo YA. Efgartigimod: First Approval. Drugs. 2022;82(3):341-348. PubMed PMID: 35179720
  10. Howard JF Jr, Bril V, Vu T, Karam C, Peric S, De Bleecker JL, et al. Long-term safety, tolerability, and efficacy of efgartigimod (ADAPT+): interim results from a phase 3 open-label extension study in participants with generalized myasthenia gravis. Front Neurol. 2023;14:1284444. PubMed PMID: 38318236
  11. Howard JF Jr, Vu T, Li G, Korobko D, Smilowski M, Liu L, et al. Subcutaneous efgartigimod PH20 in generalized myasthenia gravis: A phase 3 randomized noninferiority study (ADAPT-SC) and interim analyses of a long-term open-label extension study (ADAPT-SC+). Neurotherapeutics. 2024;21(5):e00378. PubMed PMID: 39227284
  12. Habib AA, Claeys KG, Bril V, Hussain Y, Gwathmey K, Sahagian G, et al. ADAPT NXT: Fixed Cycles or Every-Other-Week IV Efgartigimod in Generalized Myasthenia Gravis. Ann Clin Transl Neurol. 2025;12(6):1162-1170. PubMed PMID: 40223516
  13. Allen JA, Lin J, Basta I, Dysgaard T, Eggers C, Guptill JT, et al. Safety, tolerability, and efficacy of subcutaneous efgartigimod in patients with chronic inflammatory demyelinating polyradiculoneuropathy (ADHERE): a multicentre, randomised-withdrawal, double-blind, placebo-controlled, phase 2 trial. Lancet Neurol. 2024;23(10):1013-1024. PubMed PMID: 39304241
  14. Allen JA, Istas G, Kuwabara S, Mole T, Querol L, Rinaldi S, et al. Long-Term Safety and Efficacy of Efgartigimod PH20 in Chronic Inflammatory Demyelinating Polyradiculoneuropathy: ADHERE/ADHERE+ Trial Interim Analysis. J Peripher Nerv Syst. 2026;31(3):e70140. PubMed PMID: 42463457
  15. Broome CM, McDonald V, Miyakawa Y, Carpenedo M, Kuter DJ, Al-Samkari H, et al. Efficacy and safety of the neonatal Fc receptor inhibitor efgartigimod in adults with primary immune thrombocytopenia (ADVANCE IV): a multicentre, randomised, placebo-controlled, phase 3 trial. Lancet. 2023;402(10413):1648-1659. PubMed PMID: 37778358
  16. Cooper N, Broome CM, Miyakawa Y, McDonald V, Al-Samkari H, Khelif A, et al. Efficacy and Safety of Subcutaneous Efgartigimod PH20 in Adults With Primary Immune Thrombocytopenia (ADVANCE SC): A Multicenter, Randomized, Double-Blinded, Placebo-Controlled, Phase 3 Trial. Am J Hematol. 2026;101(7):1494-1506. PubMed PMID: 41943179
  17. Goebeler M, Bata-Csörgő Z, De Simone C, Didona B, Remenyik E, Reznichenko N, et al. Treatment of pemphigus vulgaris and foliaceus with efgartigimod, a neonatal Fc receptor inhibitor: a phase II multicentre, open-label feasibility trial. Br J Dermatol. 2022;186(3):429-439. PubMed PMID: 34608631
  18. Joly P, Murrell DF, Aoyama Y, Caux F, De D, Flouri M, et al. Efficacy and safety of subcutaneous efgartigimod with prednisone in moderate-to-severe pemphigus (ADDRESS): a global, phase III, randomised controlled, double-blind trial. Br J Dermatol. 2026;195(5):750-762. PubMed PMID: 42723554
  19. Peene I, Verstappen GM, Arends S, Kroese FGM, De Boeck K, Achten H, et al. Efgartigimod in Sjögren's disease: a phase 2, randomised, placebo-controlled, parallel-group, double-blinded, proof-of-concept study (RHO). Ann Rheum Dis. 2026;85(7):1341-1350. PubMed PMID: 41997805
  20. Gwathmey KG, Broome CM, Goebeler M, Murai H, Bata-Csörgo Z, Newland AC, et al. Safety profile of efgartigimod from global clinical trials across multiple immunoglobulin G-mediated autoimmune diseases. Expert Rev Clin Immunol. 2025;21(5):627-638. PubMed PMID: 40296516
  21. Guptill JT, Sleasman JW, Steeland S, Sips M, Gelinas D, de Haard H, et al. Effect of FcRn antagonism on protective antibodies and to vaccines in IgG-mediated autoimmune diseases pemphigus and generalised myasthenia gravis. Autoimmunity. 2022;55(8):620-631. PubMed PMID: 36036539
  22. Azar AE, Sleasman JW, Steeland S, Verhamme FM, Winthrop KL. Humoral immune response to polyvalent pneumococcal vaccine in healthy participants receiving efgartigimod: a randomized, open-label, placebo-controlled, parallel-group phase 1 trial. Front Immunol. 2026;17:1799480. PubMed PMID: 42183242
  23. Gilhus NE. Treatment considerations in myasthenia gravis for the pregnant patient. Expert Rev Neurother. 2023;23(2):169-177. PubMed PMID: 36786092
  24. Bril V, Drużdż A, Grosskreutz J, Habib AA, Mantegazza R, Sacconi S, et al. Safety and efficacy of rozanolixizumab in patients with generalised myasthenia gravis (MycarinG): a randomised, double-blind, placebo-controlled, adaptive phase 3 study. Lancet Neurol. 2023;22(5):383-394. PubMed PMID: 37059507
  25. Antozzi C, Vu T, Ramchandren S, Nowak RJ, Farmakidis C, Bril V, et al. Safety and efficacy of nipocalimab in adults with generalised myasthenia gravis (Vivacity-MG3): a phase 3, randomised, double-blind, placebo-controlled study. Lancet Neurol. 2025;24(2):105-116. PubMed PMID: 39862879
  26. Moise KJ Jr, Ling LE, Oepkes D, Tiblad E, Verweij EJTJ, Lopriore E, et al. Nipocalimab in Early-Onset Severe Hemolytic Disease of the Fetus and Newborn. N Engl J Med. 2024;391(6):526-537. PubMed PMID: 39115062
  27. Nowak RJ, Breiner A, Bril V, Allen JA, Khan S, Levine T, et al. Subcutaneous batoclimab in generalized myasthenia gravis: Results from a Phase 2a trial with an open-label extension. Ann Clin Transl Neurol. 2024;11(1):194-206. PubMed PMID: 38062618

Regulatory sources: the FDA announcement of 17 December 2021; the FDA Drugs@FDA records for the two biologics licences; the current United States prescribing information for both forms; and the EMA European public assessment report page for efgartigimod alfa.

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