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Neonatal Fc receptor (FcRn) blocker Pregnancy: SPC section 4.6: Pregnancy - There is no available data on the use of efgartigimod alfa during pregnancy. Antibodies including therapeutic monoclonal antibodies are known to be actively transported across the placenta (after 30 weeks of gestation) by binding to the FcRn. Efgartigimod alfa may be transmitted from the mother to the developing foetus. As efgartigimod alfa is expected to reduce maternal antibody levels, and is also expected to inhibit the transfer of maternal antibodies to the foetus, reduction in passive protection to the newborn is anticipated. Therefore, risks and benefits of administering live / live-attenuated vaccines to infants exposed to efgartigimod alfa in utero should be considered. Treatment of pregnant women with Vyvgart should only be considered if the clinical benefit outweighs the risks. Breast-feeding - There is no information regarding the presence of efgartigimod alfa in human milk, the effects on the breastfed child or the effects on milk production. Animal studies on the transfer of efgartigimod alfa into milk have not been conducted, and therefore, excretion into maternal milk cannot be excluded. Maternal IgG is known to be present in human milk. Treatment of lactating women with efgartigimod alfa should only be considered if the clinical benefit outweighs the risks. Fertility - There is no available data on the effect of efgartigimod alfa on fertility in humans. Animal studies showed no impact of efgartigimod alfa on male and female fertility parameters.

Efgartigimod alfa

Brand names: Vyvgart

Efgartigimod alfa is a neonatal Fc receptor (FcRn) blocker used to treat generalised myasthenia gravis in adults who are anti-acetylcholine receptor antibody positive.

Adult dose

Dose: Generalised myasthenia gravis (adults who are anti-acetylcholine receptor (AChR) antibody positive; add-on to standard therapy): 10 mg/kg per infusion as a 1-hour intravenous infusion, given once weekly for 4 weeks (one treatment cycle). In patients weighing 120 kg or more, the recommended dose is 1,200 mg (3 vials) per infusion. Subsequent treatment cycles are given according to clinical evaluation.
Route: Intravenous infusion over 1 hour, after dilution with sodium chloride 9 mg/ml (0.9%) (total 125 ml of diluted medicinal product through a 0.2 micrometre filter, flushing the line afterwards). Not as an intravenous push or bolus injection. Given by a healthcare professional under the supervision of a physician experienced in neuromuscular disorders.
Frequency: Once weekly for 4 weeks per treatment cycle. The frequency of treatment cycles may vary by patient; in the clinical development programme the earliest time to start a subsequent cycle was 7 weeks from the initial infusion of the previous cycle.
Strength of the SPC pinned for this card: Vyvgart 20 mg/ml concentrate for solution for infusion, 400 mg per 20 ml vial (SPC section 2). The 10 mg/kg figure is per infusion (a per-dose, weight-based dose), not a daily total. SCOPE: this card covers the INTRAVENOUS presentation only. The SPC section 4.1 indication is gMG in anti-AChR antibody positive adults, as an add-on to standard therapy. Any other efgartigimod alfa formulation (for example a subcutaneous injection) has a different dose and route and is not covered here. No maximum dose is printed other than the fixed 1,200 mg (3 vials) per infusion recommended for patients weighing 120 kg or more. Missed dose: treatment may be given up to 3 days before or after the scheduled time point, after which the original schedule is resumed until the cycle is completed; a dose that would be delayed for more than 3 days should not be given, so that two consecutive doses are at least 3 days apart. Elderly: no dose adjustment required at 65 years and older. Infusion reactions: administer at a slower rate, interrupt or discontinue. Diluted solution should be administered immediately and the infusion completed within 4 hours of dilution. Appropriate treatment for infusion and hypersensitivity-related reactions should be readily available before administration. Paediatric: safety and efficacy not established; no data.

Dose adjustments

Renal

SPC section 4.2: limited safety and efficacy data in mild renal impairment - no dose adjustment is required for mild renal impairment; there is very limited safety and efficacy data in moderate or severe renal impairment (no recommendation is printed).

Hepatic

SPC section 4.2: no data in patients with hepatic impairment are available; no dose adjustment is required in hepatic impairment.

Dose independently re-sourced from UK Summary of Product Characteristics (SPC) via MHRA Products — clinician-reviewed. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

  • Hypersensitivity to the active substance or to any of the excipients listed in section 6.1 (section 4.3)

Side effects

  • Upper respiratory tract infections (very common, 10.7%) and urinary tract infections (common, 9.5%) were the most frequently observed adverse reactions; bronchitis (common) (section 4.8)
  • Common: nausea, myalgia, procedural headache (headache temporally related to the intravenous infusion, 4.8% vs 1.2% on placebo) (section 4.8)
  • Anaphylactic reaction, frequency not known (post-marketing reports) (sections 4.4, 4.8)
  • Infusion reactions such as rash or pruritus may occur; in the clinical trial they were mild to moderate (section 4.4)
  • Transient reduction in IgG levels - the risk of infections may increase (sections 4.4, 4.8)
  • Immunogenicity: treatment-induced antibodies to efgartigimod alfa in 17/83 (21%) patients; neutralising antibodies in 6/83 (7%); no apparent impact on efficacy or safety (section 4.4)
  • Note: the retrieved section 4.8 was truncated at the source-fetch limit (it breaks off at the adverse-reaction reporting statement)

Interactions

  • No interaction studies have been performed (section 4.5)
  • Products that bind the neonatal Fc receptor (immunoglobulin products, monoclonal antibodies or antibody derivatives containing the human IgG Fc domain): concentrations may be decreased - if possible postpone starting them until 2 weeks after the last dose of a Vyvgart cycle, and monitor the intended response closely if given together (section 4.5)
  • Plasma exchange, immunoadsorption and plasmapheresis may reduce circulating levels of efgartigimod alfa (section 4.5)
  • Live or live-attenuated vaccines: generally not recommended; if required, give at least 4 weeks before treatment and at least 2 weeks after the last dose; other vaccines may be given at any time (sections 4.4, 4.5)
  • When non-steroidal immunosuppressants, corticosteroids and anticholinesterase therapies are decreased or discontinued, monitor closely for signs of disease exacerbation (section 4.4)

Monitoring

  • Monitor for clinical signs and symptoms of infection during treatment; in active infection weigh the benefit-risk of continuing or withholding treatment, and consider delaying treatment in serious infection until it has resolved (section 4.4)
  • Monitor patients during administration and for 1 hour afterwards for signs and symptoms of infusion reactions (section 4.4)
  • Record the name and batch number of the administered product for traceability (section 4.4)
  • Treatment in MGFA Class V patients (myasthenic crisis) has not been studied (section 4.4)
  • Monitor closely for exacerbation when immunosuppressants, corticosteroids or anticholinesterases are reduced or stopped (section 4.4)

Clinical monograph

How it works

It is an engineered antibody fragment that binds FcRn, blocking the recycling of immunoglobulin G and thereby lowering circulating IgG, including pathogenic autoantibodies.

Prescribing in practice

  • Lowering of IgG may increase susceptibility to infection, so monitor for and manage infections during treatment.
  • It is administered in treatment cycles guided by clinical response rather than continuously.
  • Ensure infections are appropriately managed and immunisation status is considered before starting.

Monitoring

Monitor for signs of infection and assess myasthenia gravis clinical scores to guide the timing of subsequent treatment cycles.

Counselling the patient

  • Report symptoms of infection such as fever, cough or urinary symptoms promptly.
  • Treatment is given in cycles; the team will determine when the next cycle is needed.
  • Keep vaccinations up to date as advised before treatment.

Evidence & guidelines

Efficacy in anti-acetylcholine receptor antibody positive generalised myasthenia gravis was demonstrated in the randomised placebo-controlled ADAPT trial.

Reference: NICE TA935; ABN MG guidance; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Related

Curated clinical cross-links plus same-class fallbacks.

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