Beyfortus Nirsevimab Injection

1. Indications and Usage
BEYFORTUS is indicated for the prevention of lower respiratory tract disease caused by respiratory syncytial virus (RSV) in:
Newborns and infants born during or entering their first RSV season.
Children up to 24 months of age who remain vulnerable to severe RSV disease during their second RSV season.
2. Dosage and Administration
Route: Intramuscular (IM) injection only.
Recommended Dose:
First RSV Season: Based on weight at the time of administration.
< 5 kg: 50 mg.
≥ 5 kg: 100 mg.
Second RSV Season:
If entering second season within 90 days of first dose: 200 mg.
If entering second season more than 90 days after first dose: 100 mg.
Administration: Administered by a healthcare professional. The preferred site is the anterolateral aspect of the thigh. Do not administer into the gluteal muscle.
Concomitant Use: BEYFORTUS can be administered concurrently with routine childhood vaccines using separate syringes and different injection sites. Do not mix with other vaccines.
3. Mechanism of Action
Nirsevimab is a recombinant human immunoglobulin G 1 (IgG1) monoclonal antibody that binds to the fusion (F) protein of RSV. This binding inhibits the fusion of the viral envelope with the host cell membrane, thereby neutralizing the virus and preventing infection. The Fc region contains a triple amino acid substitution (YTE) that extends the serum half-life, providing protection for approximately 5 months with a single dose.
4. Safety and Warnings
Hypersensitivity: Serious allergic reactions, including anaphylaxis, have been reported. Discontinue immediately if a severe allergic reaction occurs.
Injection Site Reactions: Local reactions (e.g., erythema, swelling, induration) may occur.
Risk Evaluation: Assessment of the risk-benefit profile is recommended for infants with conditions that may affect the immune response or coagulation status (e.g., hemophilia, congenital heart disease).
5. Adverse Reactions and Clinical Research
Common Adverse Reactions: The most common adverse reactions (incidence ≥5%) include injection site reactions (erythema, swelling, induration), rash, pyrexia, and irritability.
Clinical Research: Efficacy and safety were established in the Phase 3 MEDLEY trial (high-risk infants) and the Phase 3 HARMONY trial (preterm and healthy term infants). Nirsevimab demonstrated a significant reduction in hospitalizations due to RSV-associated lower respiratory tract disease compared to placebo.
6. Drug Interactions
Vaccines: No formal interaction studies. Nirsevimab is not expected to interfere with the immune response to concurrent vaccination.
Immunoglobulins: Palivizumab should not be used in infants who have received BEYFORTUS in the same season. There is no data on substituting BEYFORTUS for palivizumab.
7. Pharmaceutical Information
Active Ingredient: Nirsevimab-alip.
Strength: 50 mg/0.5 mL or 100 mg/mL (single-dose prefilled syringe).
Description: Clear to slightly opalescent, colorless to pale yellow solution.
Storage: Store in a refrigerator at 2°C to 8°C (36°F to 46°F). Do not freeze or shake.