Vyvgart / Vyvgart Hytrulo (Efgartigimod)
Indications
| Indication | Approved Population | Therapy Type | Status |
|---|---|---|---|
| Generalized myasthenia gravis (gMG) — Vyvgart IV | Adults who are anti-acetylcholine receptor (AChR) antibody positive | Add-on to standard background therapy (acetylcholinesterase inhibitors, corticosteroids, and/or non-steroidal immunosuppressants) | FDA Approved (Dec 2021) |
| Generalized myasthenia gravis (gMG) — Vyvgart Hytrulo SC | Adults who are anti-AChR antibody positive | Add-on to standard background therapy; same indication as Vyvgart IV with subcutaneous administration | FDA Approved (Jun 2023) |
| Chronic inflammatory demyelinating polyneuropathy (CIDP) — Vyvgart Hytrulo SC | Adults with definite or probable CIDP (EFNS/PNS criteria); progressing or relapsing forms | Maintenance therapy as continuous once-weekly subcutaneous injections (no cycling) | FDA Approved (Jun 2024) |
Efgartigimod is the first commercially available agent that selectively blocks the neonatal Fc receptor (FcRn). FcRn is expressed on endothelial cells, monocytes, and other antigen-presenting cells, where it normally rescues internalised IgG molecules from lysosomal degradation and recycles them back into the circulation. By occupying FcRn with an engineered, high-affinity IgG1 Fc fragment, efgartigimod accelerates the catabolism of all IgG subclasses — including pathogenic autoantibodies — without depleting B cells, complement components, IgM, IgA, IgE, or albumin. The clinical effect is a rapid, reversible, dose-related reduction in total IgG (and consequently autoantibody) levels that begins within days, peaks around weeks 3–4 of a treatment cycle, and recovers over the following weeks. Vyvgart (intravenous) was the first FcRn antagonist approved in the United States (December 2021) for adults with anti-AChR-positive generalized myasthenia gravis. Vyvgart Hytrulo (June 2023) is a subcutaneous co-formulation with recombinant human hyaluronidase that allows the same efgartigimod alfa molecule to be delivered by a brief subcutaneous injection rather than a one-hour intravenous infusion. In June 2024 the SC formulation also became the first FcRn antagonist approved for CIDP, based on the ADHERE trial.
Generalized MG: Efgartigimod is positioned as add-on therapy for adults with anti-AChR-antibody-positive disease who remain symptomatic despite standard care (pyridostigmine, corticosteroids, and/or steroid-sparing immunosuppressants). It is given in cycles of four weekly doses, with subsequent cycles individualised to clinical response — distinct from the chronic continuous dosing of complement inhibitors (eculizumab, ravulizumab, zilucoplan) and the FcRn-pathway alternative rozanolixizumab.
CIDP: Efgartigimod (SC only) is given as continuous once-weekly maintenance therapy for adults with definite or probable CIDP, joining intravenous immunoglobulin (IVIG), subcutaneous immunoglobulin (SCIG), corticosteroids, and plasma exchange in the available chronic-care options.
Efgartigimod is being studied across a range of IgG-mediated autoimmune disorders — including pemphigus vulgaris, primary immune thrombocytopenia (ITP), idiopathic inflammatory myopathy, bullous pemphigoid, post-COVID and idiopathic autoimmune encephalitides, lupus nephritis, and Sjögren disease — but at the time of this monograph, only the gMG and CIDP indications listed above are FDA-approved. Off-label use should be approached with the same caution that applies to all biologics: with documented patient consent, specialist supervision, and recognition that the efficacy and safety profile in non-approved indications has not been characterised in registrational trials. Evidence quality outside approved indications: low to moderate (mainly phase 2 / early-phase data).
Dosing
Dosing depends on both the formulation (Vyvgart IV or Vyvgart Hytrulo SC) and the indication (gMG vs CIDP). For gMG, both formulations are given in cycles of four weekly doses, with subsequent cycles initiated based on clinical response. For CIDP, only the SC formulation is approved, and it is given as continuous once-weekly maintenance dosing without a planned cycle break. Verify the product, indication, and dosing schedule on every order. Live vaccines should be given before, not during, treatment.
Vyvgart (Intravenous) — Generalized Myasthenia Gravis
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Adult, anti-AChR-positive gMG, < 120 kg | 10 mg/kg IV over 1 hour | 10 mg/kg IV once weekly × 4 weeks per cycle | Capped at 1,200 mg per infusion | Dilute the calculated dose in 0.9% sodium chloride to a total volume of 125 mL; infuse via 0.2-micron in-line filter; flush line with 0.9% NaCl after infusion Each vial = 400 mg / 20 mL (20 mg/mL); use aseptic technique; single-dose vial |
| Adult, anti-AChR-positive gMG, ≥ 120 kg | 1,200 mg IV over 1 hour | 1,200 mg IV once weekly × 4 weeks per cycle | 1,200 mg per infusion (3 vials) | Fixed dose for patients ≥ 120 kg replaces the per-kg calculation Three 400 mg vials per infusion |
| Subsequent treatment cycles | Same dose as cycle 1 | Cycle of 4 weekly doses | — | Time subsequent cycles by clinical evaluation. Per the FDA prescribing information, the safety of initiating a new cycle sooner than 50 days from the start of the previous cycle has not been established. In ADAPT, the median time to second cycle in efgartigimod-treated patients was 72 days from cycle 1 Reassess MG-ADL / QMG at the end of each cycle to plan timing of the next |
| Missed dose | — | Administer up to 3 days late, then resume original schedule | — | Do not double up; if delay exceeds 3 days, contact the prescribing centre to plan whether to reset the cycle |
Vyvgart Hytrulo (Subcutaneous) — Generalized Myasthenia Gravis
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Dose | Notes |
|---|---|---|---|---|
| Adult, anti-AChR-positive gMG (any body weight) | 1,008 mg / 11,200 U SC | 1,008 mg / 11,200 U SC once weekly × 4 weeks per cycle | Fixed dose; no per-kg adjustment | Inject over 30–90 seconds via a 25G winged infusion set (12-inch tubing, max prime 0.4 mL); abdominal injection ≥ 2–3 inches from the navel; rotate sites; do not dilute Co-formulated with recombinant human hyaluronidase (PH20) — transiently increases SC tissue permeability for ~24–48 h |
| Subsequent treatment cycles | — | Cycle of 4 weekly SC injections | — | As with Vyvgart IV, safety of initiating a new cycle sooner than 50 days from the start of the previous cycle has not been established |
Vyvgart Hytrulo (Subcutaneous) — Chronic Inflammatory Demyelinating Polyneuropathy
| Clinical Scenario | Starting Dose | Maintenance Dose | Maximum Duration | Notes |
|---|---|---|---|---|
| Adult with definite or probable CIDP | 1,008 mg / 11,200 U SC once weekly | 1,008 mg / 11,200 U SC continuous once-weekly dosing | No defined maximum; reassess response periodically | CIDP dosing is continuous — there is no 4-week cycle and no 50-day cycle restriction. In the ADHERE trial, mean treatment duration in stage B was 25 weeks, with placebo-controlled follow-up extending up to 48 weeks Reassess CIDP disability (e.g., aINCAT, I-RODS) at periodic intervals; consider tapering only if sustained remission is documented |
| Missed dose (gMG or CIDP) | — | Administer up to 3 days late, then resume schedule | — | Do not double up |
Population-Specific Considerations
| Population | Adjustment | Rationale |
|---|---|---|
| Mild renal impairment (eGFR 60–89 mL/min/1.73 m²) | No dose adjustment | Population PK analyses showed a 22% increase in IV exposure and an 11–20% increase in SC exposure relative to normal renal function; not considered clinically significant |
| Moderate (eGFR 30–59) or severe (eGFR < 30 mL/min/1.73 m²) renal impairment | Insufficient data — use with caution | No dedicated PK study; safety not established |
| Hepatic impairment | No dedicated guidance | Hepatic impairment is not expected to affect pharmacokinetics — efgartigimod is catabolised proteolytically rather than by the liver |
| Geriatric (≥ 65 years) | No specific adjustment | Clinical studies did not enrol sufficient older patients to determine differential response, but population PK suggests no clinically meaningful effect of age |
| Pediatric (< 18 years) | Not established | Safety and effectiveness in pediatric patients have not been established for any indication |
| Pregnancy | Individualised — enrol in pregnancy registry | No human data; transplacental IgG transfer increases through pregnancy and reduction in maternal IgG is expected to reduce passive immunity to the newborn — defer live or live-attenuated vaccines in exposed infants until safe |
In gMG, efgartigimod is given as cycles of four weekly doses, after which the patient is observed for clinical and serological response. The next cycle is timed by symptom recurrence — typically 4 to 12+ weeks later — but cannot start sooner than 50 days from the start of the previous cycle (FDA PI). Many patients re-treat at intervals approximating their individual IgG re-accumulation time; the median time to a second cycle in ADAPT was 72 days. In contrast, CIDP dosing is continuous once-weekly with no cycle break — interruption risks relapse, as demonstrated by the ADHERE stage B placebo-withdrawal data (hazard ratio for clinical deterioration 0.394 favouring efgartigimod). Confirm the indication on every order before scheduling subsequent doses.
Vyvgart (efgartigimod alfa-fcab) is a 10 mg/kg intravenous dose (or 1,200 mg fixed dose at ≥ 120 kg) delivered over one hour. Vyvgart Hytrulo (efgartigimod alfa and hyaluronidase-qvfc) is a fixed 1,008 mg / 11,200 U subcutaneous dose delivered over 30–90 seconds; it contains co-formulated recombinant human hyaluronidase that the IV product does not. Patients with a history of serious hypersensitivity to hyaluronidase cannot receive Vyvgart Hytrulo even if they previously tolerated Vyvgart IV. Verify product, route, and indication on every order; use distinct order sets if your institution allows both formulations.
Pharmacology
Mechanism of Action
Efgartigimod alfa is an Fc fragment derived from human IgG1 (the za allotype) and engineered for high-affinity, pH-dependent binding to the neonatal Fc receptor (FcRn). FcRn does not recognise IgG at neutral plasma pH, but in the acidic environment of endosomes inside endothelial and antigen-presenting cells it captures internalised IgG and recycles it back to the cell surface, releasing it into the circulation. This recycling mechanism is the reason endogenous IgG has an unusually long half-life of approximately three weeks. By saturating FcRn with a competitive Fc fragment that does not have an antigen-binding (Fab) region, efgartigimod prevents this recycling: internalised endogenous IgG, including pathogenic autoantibodies against the acetylcholine receptor (in gMG) or against peripheral nerve antigens (in CIDP), is shunted to the lysosome and degraded. The result is a rapid, reversible, dose-dependent reduction in total IgG of approximately 60–70% by week 4 of a treatment cycle, with proportional reductions in IgG-subtype autoantibodies. Importantly, efgartigimod does not bind antigen, does not deplete B cells or plasma cells, and does not reduce IgM, IgA, IgE, complement components, or albumin — distinguishing it pharmacologically from broad immunosuppressants and from complement inhibitors. The hyaluronidase component of Vyvgart Hytrulo is unrelated to the IgG-lowering effect: it transiently depolymerises hyaluronan in the subcutaneous interstitium to permit dispersion of the larger SC injection volume; the effect resolves within 24–48 hours.
ADME Profile
| Parameter | Value | Clinical Implication |
|---|---|---|
| Absorption | IV: 100% bioavailable (intravenous administration). SC: bioavailability not separately reported in the FDA PI; pharmacodynamic noninferiority to IV demonstrated in ADAPT-SC (mean total IgG reduction at day 29: 66.4% SC vs 62.2% IV) | Both formulations achieve clinically equivalent IgG-lowering at the recommended doses; SC offers reduced chair time and the option of administration outside a dedicated infusion suite |
| Distribution | Volume of distribution 15–20 L; consistent with predominantly vascular and interstitial-fluid distribution typical of a 54 kDa Fc fragment; no information on placental or breast-milk transfer in humans, but transplacental IgG transfer increases through pregnancy | Reduction in maternal IgG during pregnancy is expected to reduce passive immunity to the newborn — defer live or live-attenuated vaccines in exposed infants and individualise risk-benefit |
| Metabolism | Catabolism by widespread proteolytic enzymes to small peptides and amino acids; not metabolised by cytochrome P450 enzymes | Negligible CYP-mediated drug interactions; no specific hepatic-impairment dose adjustment |
| Elimination | Terminal half-life 80–120 hours (3–5 days); < 0.1% of an IV dose recovered in urine; PK is approximately linear up to 50 mg/kg IV (5× the recommended dose) and up to 1,750 mg SC (1.75× the recommended dose) | The relatively short half-life (compared with intact IgG, which is ~ 21 days) is intentional: it mediates rapid IgG turnover during dosing, then rapid recovery between cycles, allowing intermittent re-treatment in gMG. Renal impairment has minimal effect; hepatic impairment is not expected to be relevant |
Efgartigimod is mechanistically distinct from the other targeted therapies approved for AChR-positive gMG. Complement inhibitors (eculizumab, ravulizumab, zilucoplan) block terminal complement activity at C5, preventing membrane attack complex formation at the neuromuscular junction. FcRn antagonists (efgartigimod, rozanolixizumab) lower circulating IgG, reducing the supply of pathogenic AChR autoantibodies. The two strategies have complementary biology, different infection-risk profiles (meningococcal precautions are essential for complement inhibitors but not FcRn antagonists), and different administration logistics (continuous chronic dosing for complement inhibitors vs cyclical or weekly dosing for FcRn antagonists).
Side Effects
The overall safety profile of efgartigimod has been characterised primarily in three pivotal trials: ADAPT (Vyvgart IV in gMG, n = 84 vs 83 placebo), ADAPT-SC (Vyvgart Hytrulo SC vs Vyvgart IV in gMG, n = 55 vs 55), and ADHERE stage B (Vyvgart Hytrulo SC vs placebo in CIDP, n = 111 vs 110). Most adverse reactions are mild to moderate, related either to the route of administration (infusion-related reactions for IV; injection site reactions for SC) or to the predictable consequences of lowering total IgG (mild increase in infections, especially upper respiratory and urinary tract). Serious infections, hypersensitivity reactions, and infusion-related reactions are uncommon but clinically important and are highlighted in the FDA prescribing information.
| Adverse Effect | Vyvgart IV (n = 84) | Placebo (n = 83) | Clinical Note |
|---|---|---|---|
| Respiratory tract infection | 33% | 29% | Includes upper and lower RTI; majority mild to moderate |
| Headache (incl. migraine, procedural headache) | 32% | 29% | Not consistently dose-related; usually responsive to standard analgesia |
| Urinary tract infection | 10% | 5% | Approximately twice the placebo rate; counsel patients on prompt reporting of urinary symptoms |
| Adverse Effect | Vyvgart IV | Placebo | Clinical Note |
|---|---|---|---|
| Paraesthesia (incl. oral hypoaesthesia, hypoaesthesia, hyperaesthesia) | 7% | 5% | Mostly mild and transient |
| Myalgia | 6% | 1% | Important to distinguish from MG-related muscle weakness or worsening |
| Adverse Effect | Estimated Frequency | Typical Onset | Required Action |
|---|---|---|---|
| Anaphylaxis / serious hypersensitivity reactions | Postmarketing reports — frequency not quantified | During administration or within 1 hour; some hypersensitivity (rash, angioedema, dyspnoea) reported up to 3 weeks post-dose | Discontinue the infusion/injection; institute appropriate supportive measures; consider permanent discontinuation if severe; future doses are contraindicated after a serious hypersensitivity reaction |
| Hypotension leading to syncope | Postmarketing reports — frequency not quantified | During or within 1 hour of administration | Discontinue the dose; supportive care including IV fluids and supine positioning; contraindicated for further use after a serious episode |
| Infusion-related reactions (Vyvgart IV) — hypertension, chills, shivering, thoracic / abdominal / back pain | Postmarketing reports — frequency not quantified | During or within 1 hour of infusion | Severe: discontinue; weigh risks/benefits of re-administration. Mild–moderate: rechallenge with close clinical observation, slower infusion rate, and pre-medications |
| Serious infection | Uncommon at recommended dosing; frequency not separately quantified in PI | Any time during therapy | Delay efgartigimod administration if active infection; treat infection appropriately; consider withholding until resolved |
| Below-normal hematology values (WBC, lymphocyte, neutrophil counts) | In Study 1: WBC < LLN 12% (vs 5% placebo); lymphocyte < LLN 28% (vs 19%); neutrophil < LLN 13% (vs 6%) | During cycles | Most are mild to moderate; periodic CBC monitoring is reasonable, particularly in patients on concomitant immunosuppression |
| Reduced response to vaccinations / loss of passive immunity in pregnancy | Expected pharmacological consequence of IgG reduction | During treatment cycles; for neonates of treated mothers, throughout exposure period | Update age-appropriate vaccinations before each treatment cycle; do not give live vaccines during therapy; defer live or live-attenuated vaccines in infants exposed in utero until safe |
| Reason for Treatment Modification | Frequency / Context | Action |
|---|---|---|
| Active infection | Per protocol | Delay administration until the infection has resolved; treat appropriately; consider withholding subsequent doses for serious infection |
| Serious hypersensitivity reaction (anaphylaxis, hypotensive syncope) | Per FDA PI | Permanent discontinuation; future use of efgartigimod alfa products (and, for Vyvgart Hytrulo, hyaluronidase products) is contraindicated |
| Severe infusion-related reaction (Vyvgart IV) | Per FDA PI | Discontinue the infusion; consider risks and benefits of readministration. Mild-moderate reactions may be rechallenged with slower rate and pre-medication |
| Loss of clinical response in gMG | Per clinical evaluation | Reassess timing of next cycle; consider switching mechanism (e.g., complement inhibitor) if multi-cycle response wanes |
| Loss of efficacy or relapse in CIDP | Per clinical evaluation | Confirm the diagnosis (consider chronic immune-mediated alternatives); review whether dose interruptions occurred; coordinate with neuromuscular specialist for next-line therapy (IVIG, SCIG, corticosteroids, or plasma exchange) |
Because efgartigimod transiently lowers total IgG (including vaccine-specific antibodies), vaccination should be planned before, not during, treatment cycles. The FDA prescribing information directs clinicians to evaluate the need for age-appropriate vaccines according to immunization guidelines before initiating each new cycle, and explicitly recommends against live-attenuated vaccines during therapy. Practical strategy: at the time of gMG diagnosis or before the first cycle, update inactivated vaccines (annual influenza, COVID-19 boosters, pneumococcal series, recombinant zoster, hepatitis B if applicable) and bring live vaccines (MMR, varicella, yellow fever) up to date if needed. For CIDP — where dosing is continuous — vaccinations should be updated before initiation; live vaccines are generally avoided thereafter, with timing of any necessary live vaccine considered in collaboration with infectious-disease and neurology teams.
Drug Interactions
Efgartigimod has a relatively narrow drug-interaction profile: it is not metabolised by cytochrome P450 enzymes, no clinical drug-interaction studies have been conducted, and standard small-molecule pharmacokinetic interactions are not expected. The clinically meaningful interactions are pharmacodynamic and arise from two mechanisms — (1) competition with co-administered IgG-based or IgG-Fc-containing therapies for FcRn binding, and (2) the immune effects of lowering circulating IgG. The interactions below are drawn from the FDA prescribing information (Section 7) and from the established pharmacology of FcRn antagonism.
Monitoring
Monitoring of efgartigimod therapy is largely clinical — symptom response, infection surveillance, and watchfulness for infusion-related and hypersensitivity reactions. Routine measurement of total IgG levels is not required by the FDA prescribing information for clinical decision-making, although some specialty centres track total IgG to characterise pharmacodynamic response or to time subsequent gMG cycles. The most consistent monitoring requirement is a structured pre-cycle vaccination check.
-
Vaccination Status
Before initiation; before each new gMG cycle
Routine Per FDA PI: evaluate need to administer age-appropriate vaccines according to immunization guidelines before initiation of a new treatment cycle. Do not give live vaccines during therapy. Coordinate with primary care to update inactivated vaccines (influenza, COVID-19, pneumococcal, zoster, hepatitis B as indicated). -
Active Infection Screen
Before each dose
Routine Ask specifically about urinary, respiratory, and skin/soft-tissue symptoms. Defer the dose if active infection is present; treat first and reassess. -
Symptom Response (gMG)
End of each cycle and 4 weeks later
Routine Use a structured tool — MG-ADL is the validated instrument from the ADAPT trial (≥ 2-point reduction at 4+ consecutive weeks defined a responder). QMG is the secondary assessment. The pattern of response and recurrence informs the timing of the next cycle. -
Symptom Response (CIDP)
Periodic during continuous weekly therapy
Routine Use aINCAT (adjusted Inflammatory Neuropathy Cause and Treatment disability score), I-RODS, and grip strength as in the ADHERE trial. A ≥ 1-point increase in aINCAT (with confirmation) defined clinical deterioration. -
Infusion-Related / Hypersensitivity Surveillance
During and after each dose
Routine For Vyvgart IV: monitor during infusion and for 1 hour thereafter for signs and symptoms of hypersensitivity. For Vyvgart Hytrulo SC: monitor for at least 30 minutes after administration. Train staff to recognise anaphylaxis, angioedema, hypotension, dyspnoea, and severe infusion-related reactions. -
Complete Blood Count
Before initiation; periodically during therapy
Trigger-based Below-normal WBC, lymphocyte, and neutrophil counts are more common with efgartigimod than placebo (12% vs 5%, 28% vs 19%, 13% vs 6%, respectively, in Study 1). Most are mild to moderate, but periodic CBC is reasonable in patients on concomitant immunosuppression or those with recurrent infections. -
Total IgG (Optional)
Per institutional protocol
Trigger-based Not required by the FDA PI. Some centres measure total IgG at baseline and at end of cycle to characterise individual response or to inform cycle timing in gMG. Mean reduction at week 4 was approximately 60–70% in pivotal trials. -
Pregnancy and Breastfeeding
At initiation; if pregnancy planned/discovered
Trigger-based Discuss the pregnancy registry (1-855-272-6524 / Vyvgartpregnancy.com). Plan delivery and neonatal care with an awareness that maternal IgG reduction may reduce passive immunity and that live vaccines should be deferred in exposed infants.
Contraindications & Cautions
Absolute Contraindications
- Vyvgart IV: Serious hypersensitivity to efgartigimod alfa products or to any of the excipients of Vyvgart. Reactions in the FDA PI include anaphylaxis and hypotension leading to syncope.
- Vyvgart Hytrulo SC: Serious hypersensitivity to efgartigimod alfa products, to hyaluronidase, or to any of the excipients of Vyvgart Hytrulo. The hyaluronidase contraindication applies even if the patient previously tolerated Vyvgart IV.
Relative Contraindications (Specialist Input Recommended)
- Active serious infection — defer initiation or subsequent doses until the infection is resolved (FDA PI Section 5.1).
- Recent live or live-attenuated vaccine — schedule live vaccines before initiation where feasible; live vaccines are not recommended during therapy.
- Concomitant chronic IVIG, SCIG, or other Fc-containing biologic therapy — efficacy of either agent may be reduced. If both are clinically needed, consider an alternative for one, with neuromuscular-specialist input.
- Hypogammaglobulinaemia at baseline — although the PI does not specify a contraindication, profound baseline IgG depletion (e.g., from prior rituximab plus IVIG) may amplify infection risk; specialist immunology input is appropriate.
Use with Caution
- Pregnancy — no human data; maternal IgG reduction reduces passive immunity to the newborn. Enrol in the pregnancy registry; defer live vaccines in exposed infants until safe (FDA PI Section 8.1).
- Lactation — no data on breast-milk presence; weigh maternal need against potential infant exposure (FDA PI Section 8.2).
- Pediatric patients — safety and effectiveness not established (FDA PI Section 8.4).
- Geriatric patients (≥ 65 years) — clinical trials enrolled limited numbers; population PK suggests no clinically meaningful effect of age, but individual evaluation is appropriate.
- Moderate (eGFR 30–59) or severe (eGFR < 30 mL/min/1.73 m²) renal impairment — insufficient data; use with caution.
- History of recurrent UTI or other infections — UTI was approximately twice as common in efgartigimod-treated patients as placebo in Study 1; counsel patients to report symptoms early.
At the time of this monograph, neither Vyvgart nor Vyvgart Hytrulo carries an FDA boxed warning. The FDA prescribing information’s most prominent safety messages are the warnings and precautions for infections, hypersensitivity reactions (including postmarketing anaphylaxis and hypotension), and infusion-related reactions, plus the recommendation to optimise vaccination status before each new cycle.
Patient Counselling
Purpose of Therapy
Explain in plain language that efgartigimod works by lowering the level of certain antibodies (called immunoglobulin G, or IgG) in the blood. In myasthenia gravis and CIDP, some of these antibodies attack the body’s own nerves and muscles; lowering them improves nerve-to-muscle communication (in MG) or nerve function (in CIDP). The medicine is not a cure, but it can substantially reduce symptoms while it is being given. The effect builds up over the four weekly doses of a cycle and then gradually wears off — which is why the next gMG cycle is timed by the return of symptoms, and why CIDP treatment is continued every week without breaks.
How to Take
Vyvgart (the IV form) is given as a one-hour infusion in an infusion clinic; expect to stay for an additional hour of monitoring afterwards. Vyvgart Hytrulo (the SC form) is given as a brief injection (30–90 seconds) into the abdominal skin by a healthcare professional, with at least 30 minutes of post-injection monitoring. Plan to remain reachable for the day after each dose so that any delayed reactions can be reported. Mark the date of every dose on a calendar, and bring an updated medication and vaccine list to every clinic visit.
Sources
- VYVGART® (efgartigimod alfa-fcab) injection, for intravenous use, and VYVGART® HYTRULO (efgartigimod alfa and hyaluronidase-qvfc) injection, for subcutaneous use — Combined US Prescribing Information. argenx US, Inc. Revised August 2024 (Reference ID 5427102). accessdata.fda.gov Primary FDA label combining both formulations and all approved indications (gMG for IV and SC; CIDP for SC only). Source for all dosing, contraindications, warnings, adverse-event frequencies, pharmacokinetics, immunogenicity figures, and clinical-trial summaries cited in this monograph.
- FDA News Release: FDA Approves New Treatment for Myasthenia Gravis. U.S. Food and Drug Administration. December 17, 2021. fda.gov FDA announcement of the initial approval of Vyvgart (efgartigimod alfa-fcab) — the first FcRn antagonist for any disease and the first new gMG mechanism since the approval of complement inhibition.
- Howard JF Jr, Bril V, Vu 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 Jul;20(7):526-536. doi: 10.1016/S1474-4422(21)00159-9. PMID: 34146511. pubmed.ncbi.nlm.nih.gov/34146511 Pivotal phase 3 ADAPT trial that established the efficacy of intravenous efgartigimod in adults with gMG. Source for the MG-ADL responder rate (67.7% vs 29.7% placebo) and QMG responder rate (63.1% vs 14.1% placebo) in the AChR-Ab-positive subgroup that supported FDA approval.
- Howard JF Jr, Vu T, Li G, 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 Sep 2;e00378. doi: 10.1016/j.neurot.2024.e00378. PMID: 39227284. pubmed.ncbi.nlm.nih.gov/39227284 Pharmacodynamic noninferiority study comparing the SC and IV formulations in gMG; supported the 2023 FDA approval of Vyvgart Hytrulo. Source for the day-29 IgG reduction comparison (66.4% SC vs 62.2% IV) and the SC immunogenicity figures.
- Allen JA, Lin J, Basta I, 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. doi: 10.1016/S1474-4422(24)00309-0. PMID: 39304241. pubmed.ncbi.nlm.nih.gov/39304241 Pivotal ADHERE trial that supported the June 2024 FDA approval of Vyvgart Hytrulo for CIDP. Source for the stage-A response rate, the stage-B hazard ratio for clinical deterioration (HR 0.394, 95% CI 0.253-0.614, p < 0.0001), and the CIDP-specific safety profile.
- Howard JF Jr, Bril V, Burns TM, et al; Efgartigimod MG Study Group. Randomized phase 2 study of FcRn antagonist efgartigimod in generalized myasthenia gravis. Neurology. 2019 Jun 4;92(23):e2661-e2673. doi: 10.1212/WNL.0000000000007600. PMID: 31118245. pubmed.ncbi.nlm.nih.gov/31118245 Foundational phase 2 study that established proof of concept for FcRn antagonism in autoimmune disease and provided the rationale for the ADAPT trial design.
- Narayanaswami P, Sanders DB, Wolfe G, et al. International Consensus Guidance for Management of Myasthenia Gravis: 2020 Update. Neurology. 2021 Jan 19;96(3):114-122. doi: 10.1212/WNL.0000000000011124. PMID: 33144515. doi.org/10.1212/WNL.0000000000011124 International consensus guidance for the management of myasthenia gravis. Verify the current edition at time of publication — the consensus is updated periodically and a new revision may incorporate FcRn antagonists more explicitly.
- Van den Bergh PYK, van Doorn PA, Hadden RDM, et al. European Academy of Neurology/Peripheral Nerve Society Guideline on diagnosis and treatment of chronic inflammatory demyelinating polyradiculoneuropathy: Report of a joint Task Force — Second revision. J Peripher Nerv Syst. 2021 Sep;26(3):242-268. doi: 10.1111/jns.12455. PMID: 34085743. doi.org/10.1111/jns.12455 EAN/PNS 2021 second-revision guideline on the diagnosis and management of CIDP — provides the EFNS/PNS diagnostic criteria used to enrol the ADHERE trial. Verify the most recent version at time of publication.
- Roopenian DC, Akilesh S. FcRn: the neonatal Fc receptor comes of age. Nat Rev Immunol. 2007 Sep;7(9):715-725. doi: 10.1038/nri2155. PMID: 17703228. pubmed.ncbi.nlm.nih.gov/17703228 Foundational review of neonatal Fc receptor biology that underpins the rationale for FcRn antagonism as a therapeutic strategy in IgG-mediated autoimmune disease.
- Ulrichts P, Guglietta A, Dreier T, et al. Neonatal Fc receptor antagonist efgartigimod safely and sustainably reduces IgGs in humans. J Clin Invest. 2018 Oct 1;128(10):4372-4386. doi: 10.1172/JCI97911. PMID: 30040076. pubmed.ncbi.nlm.nih.gov/30040076 First-in-human study characterising the IgG-lowering pharmacodynamics of efgartigimod, including dose-response, selectivity for IgG over other immunoglobulin classes, and tolerability — the basis for the dose selection used in the phase 2 and phase 3 programmes.
- VYVGART / VYVGART HYTRULO Section 12.3 — Pharmacokinetics. argenx US, Inc. Revised August 2024 (Reference ID 5427102). accessdata.fda.gov Primary source for the volume of distribution (15–20 L), terminal half-life (80–120 h), linear PK boundaries, urinary recovery (< 0.1%), absence of CYP metabolism, and renal-impairment population PK figures (mild renal impairment increases exposure ~ 11–22%).
- Heo YA. Efgartigimod: First Approval. Drugs. 2022 Mar;82(3):341-348. doi: 10.1007/s40265-022-01678-3. PMID: 35179720. pubmed.ncbi.nlm.nih.gov/35179720 Approval-summary review of efgartigimod’s pharmacology, clinical development, and place in therapy at the time of initial FDA approval — a useful single-source summary of the early evidence package.