VYVGART HYTRULO
Clinical safety rating: caution
Comprehensive clinical and safety monograph for VYVGART HYTRULO (VYVGART HYTRULO).
VYVGART HYTRULO (efgartigimod alfa and hyaluronidase) is a combination of efgartigimod alfa, a neonatal Fc receptor (FcRn) blocker, and hyaluronidase, an endoglycosidase that enhances subcutaneous fluid dispersion. Efgartigimod alfa binds to FcRn, reducing recycling of IgG and lowering plasma IgG levels, including pathogenic autoantibodies.
| Metabolism | Efgartigimod alfa is expected to be degraded into small peptides and amino acids via general protein catabolism; hyaluronidase is metabolized locally. |
| Excretion | Efgartigimod alfa, the active component, is a human IgG1 antibody fragment; it is expected to be degraded into small peptides and amino acids via general protein catabolism. No specific renal or biliary excretion studies are available; as an antibody fragment, it is not excreted renally intact. Hyaluronidase (recombinant human) is locally degraded and does not contribute to systemic excretion. |
| Half-life | The terminal elimination half-life of efgartigimod alfa is approximately 14 days (range 12-18 days) following subcutaneous administration. This supports a dosing interval of once weekly for the initial cycle and every 2-4 weeks for maintenance. |
| Protein binding | Efgartigimod alfa is a monoclonal antibody fragment; serum protein binding is negligible (<5%). No specific binding proteins identified. |
| Volume of Distribution | Vd is approximately 150 mL/kg (0.15 L/kg), consistent with limited extravascular distribution, primarily confined to plasma and interstitial space. |
| Bioavailability | Following subcutaneous administration of VYVGART HYTRULO, the absolute bioavailability of efgartigimod alfa is approximately 70% (range 55-85%) compared to intravenous administration. |
| Onset of Action | Subcutaneous injection: Reduction in immunoglobulin G (IgG) levels is observed within 1 week; clinical improvement in myasthenia gravis symptoms may be seen as early as 1 week after the first dose, with maximal effect by week 4. |
| Duration of Action | The pharmacodynamic effect (IgG reduction) persists for approximately 6-8 weeks after the last dose. Clinical duration varies; in clinical trials, the median time to first deterioration after completing a treatment cycle was approximately 8-12 weeks. Repeat dosing is required to maintain response. |
| Molecular Weight | 54100 |
VYVGART HYTRULO (efgartigimod alfa and hyaluronidase) subcutaneous injection: For adult patients with generalized myasthenia gravis (gMG) who are anti-AChR antibody positive, the recommended dosage is 1,008 mg efgartigimod alfa and 12,000 units hyaluronidase administered subcutaneously once weekly for 4 weeks. Subsequent cycles may be initiated based on clinical response, with at least one week between cycles; the safety and efficacy of initiating subsequent cycles more frequently than every 6 weeks have not been established.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment is recommended for patients with mild to moderate renal impairment (estimated GFR ≥30 mL/min/1.73 m²). The effect of severe renal impairment (GFR <30 mL/min/1.73 m²) on the pharmacokinetics of efgartigimod alfa is unknown; use in such patients is not recommended. |
| Liver impairment | No formal studies have been conducted in patients with hepatic impairment. Efgartigimod alfa is degraded into small peptides and amino acids, and hepatic impairment is not expected to significantly affect its clearance. No dose adjustment is recommended for patients with mild to moderate hepatic impairment (Child-Pugh class A or B). Use in severe hepatic impairment (Child-Pugh class C) has not been studied. |
| Pediatric use | Safety and effectiveness in pediatric patients have not been established. VYVGART HYTRULO is not approved for use in pediatric patients. |
| 1st trimester | Limited human data; animal studies show no evidence of teratogenicity but potential for pharmacodynamic effects due to FcRn inhibition. Use only if clearly needed. |
| 2nd trimester | May cross placenta in increasing amounts; theoretical risk of maternal IgG reduction affecting fetal immunity. Avoid unless benefit outweighs risk. |
| 3rd trimester | Likely crosses placenta; may reduce maternal IgG transfer to fetus, potentially increasing infection risk in neonate. Avoid in third trimester unless essential. |
Clinical note
Comprehensive clinical and safety monograph for VYVGART HYTRULO (VYVGART HYTRULO).
| Placental transfer | Efgartigimod alfa is a humanized IgG1 Fc fragment; likely crosses placenta via FcRn-mediated transport, increasing in second and third trimesters. |
| Breastfeeding | Not known if excreted in human milk; due to high molecular weight, excretion is likely minimal but theoretical risk of immunosuppression in infant. Consider benefit of breastfeeding versus risk. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to efgartigimod alfa or hyaluronidase (recombinant human) or any excipient
| Precautions | Infections: May increase risk of serious infections due to IgG reduction, Hypersensitivity reactions: Including anaphylaxis and angioedema, Vaccinations: Avoid live or live-attenuated vaccines during treatment, Laboratory monitoring: Monitor renal function and serum immunoglobulins |
| Food/Dietary | No specific food interactions have been identified with efgartigimod alfa and hyaluronidase. Avoid alcohol consumption due to potential exacerbation of myasthenia gravis symptoms. Maintain adequate hydration. No grapefruit juice interaction known. |
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| Geriatric use |
| No dose adjustment is required in geriatric patients (≥65 years of age). Clinical studies included a limited number of patients aged 65 and older; no overall differences in safety or efficacy were observed between elderly and younger adult patients. |
| Lactation Rating | L4 (Possibly Hazardous) |
| Teratogenic Risk | VYVGART HYTRULO (efgartigimod alfa and hyaluronidase) is a neonatal Fc receptor antagonist. There are no adequate human data on use in pregnant women to inform a drug-associated risk of major birth defects or miscarriage. In animal reproduction studies, no adverse developmental outcomes were observed with subcutaneous administration of efgartigimod alfa during organogenesis in rabbits at doses up to 5 times the maximum recommended human dose (MRHD) based on AUC. However, hyaluronidase has been shown to cause fetal skeletal malformations in mice at high doses. Based on mechanism of action, efgartigimod alfa may reduce maternal IgG levels and potentially impair maternal immunity to infections. During the second and third trimesters, IgG is actively transferred across the placenta, and efgartigimod alfa may reduce this transfer, potentially affecting fetal/infant immune defense. The drug should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus. |
| Fetal Monitoring | Monitor maternal IgG levels periodically during treatment, especially if considering live vaccine administration to the infant; neonatal IgG levels may be reduced. Monitor for increased risk of infections in the mother and neonate due to reduced IgG. Assess neonatal immune status if maternal treatment occurred late in pregnancy; consider deferring live vaccines (e.g., rotavirus, BCG) until neonatal IgG levels are adequate. No specific fetal heart rate or ultrasound monitoring required beyond routine prenatal care. |
| Fertility Effects | Animal studies have not been conducted to evaluate the effects of VYVGART HYTRULO on fertility. No human data are available. Based on mechanism of action (IgG reduction), there is no anticipated direct effect on male or female fertility. However, hyaluronidase can temporarily alter the extracellular matrix; significance in reproductive tissues is unknown. No impact on fertility is expected at therapeutic doses. |
| Clinical Pearls |
| VYVGART HYTRULO (efgartigimod alfa and hyaluronidase) is a neonatal Fc receptor (FcRn) blocker indicated for generalized myasthenia gravis (gMG) in AChR antibody-positive adults. Administer as subcutaneous injection over 30-90 seconds in the abdomen (avoid 2-inch area around navel). Rotate injection sites. Premedication not required but monitor for hypersensitivity reactions. Contraindicated in patients with active hepatitis B infection due to potential reactivation. Monitor for infections; do not administer live vaccines during treatment. Assess baseline hepatitis B and tuberculosis screening before initiation. |
| Patient Advice | Wash hands before and after injection. Rotate injection sites on the abdomen (avoid navel area). · Report signs of infection (fever, chills, cough) or hypersensitivity (rash, itching, swelling) promptly. · Do not receive live vaccines (e.g., MMR, yellow fever, varicella) during treatment. · Inform your doctor if you have hepatitis B or tuberculosis, or if you are pregnant, breastfeeding, or planning to become pregnant. · Store the autoinjector or syringe in the refrigerator at 2°C to 8°C (36°F to 46°F); do not freeze. Bring to room temperature before injection (15-25 minutes). |