MYZILRA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MYZILRA (MYZILRA).
MYZILRA is a monoclonal antibody that binds to the neonatal Fc receptor (FcRn), reducing IgG recycling and lowering circulating IgG levels, including pathogenic autoantibodies.
| Metabolism | MYZILRA is degraded into small peptides and amino acids via general protein catabolism; no specific metabolic enzymes identified. |
| Excretion | Renal elimination of unchanged drug accounts for 70% of clearance; biliary/fecal excretion accounts for 25%; 5% metabolized. |
| Half-life | Terminal elimination half-life is 22 hours; permits once-daily dosing in most patients. |
| Protein binding | 95% bound to albumin. |
| Volume of Distribution | 0.8 L/kg; indicates extensive tissue distribution. |
| Bioavailability | Oral: 60% due to first-pass metabolism; intravenous: 100%. |
| Onset of Action | Oral: 1-2 hours; intravenous: within 5 minutes. |
| Duration of Action | 24 hours; supports once-daily dosing for chronic therapy. |
10 mg intravenously once daily for 12 weeks, followed by 10 mg subcutaneously every 8 weeks for maintenance.
| Dosage form | TABLET |
| Renal impairment | No dose adjustment required for mild to moderate renal impairment (GFR ≥ 30 mL/min). Not recommended for severe renal impairment (GFR < 30 mL/min) or end-stage renal disease. |
| Liver impairment | No dose adjustment required for mild hepatic impairment (Child-Pugh A). Use with caution in moderate impairment (Child-Pugh B); dose reduction to 5 mg intravenously once daily for 12 weeks then 5 mg subcutaneously every 8 weeks. Avoid in severe impairment (Child-Pugh C). |
| Pediatric use | Not approved for pediatric patients under 18 years of age. |
| Geriatric use | No specific dose adjustment required in elderly patients (≥65 years), but consider age-related renal function decline and monitor closely. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MYZILRA (MYZILRA).
| Breastfeeding | MYZILRA is excreted into human breast milk with a milk-to-plasma ratio of 0.8. Due to potential for serious adverse reactions in the breastfed infant, including immune suppression and growth impairment, breastfeeding is not recommended during treatment and for at least 7 days after the last dose. |
| Teratogenic Risk | MYZILRA is classified as Pregnancy Category X based on human data demonstrating teratogenicity. First trimester exposure is associated with a high risk of major congenital malformations including neural tube defects, cleft palate, and cardiac anomalies. Second and third trimester exposure may cause fetal growth restriction and oligohydramnios. Contraindicated in pregnancy. |
■ FDA Black Box Warning
No black box warning.
| Serious Effects |
Active severe infection, known hypersensitivity to MYZILRA or any excipient.
| Precautions | Risk of infection (may increase susceptibility to infections due to IgG reduction), infusion-related reactions (hypersensitivity, anaphylaxis), and potential for immunization with live or attenuated vaccines (avoid live vaccines during treatment). |
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| Fetal Monitoring | Monitor maternal liver function tests, renal function, and complete blood count monthly. Perform fetal ultrasound for growth and amniotic fluid index every 4 weeks. After 24 weeks, perform non-stress testing weekly. Assess for signs of teratogenicity with level II ultrasound if exposure occurs. |
| Fertility Effects | MYZILRA may impair female fertility based on animal studies showing disrupted estrous cycles and decreased ovarian follicle count. Human data are limited. Reversibility after discontinuation is unknown. Male fertility may be affected with reduced sperm count and motility reported in animal studies. |