Biologic
RCSB PDB 5UDC
Nirsevimab
Beyfortus
- Mechanism of action
- RSV prefusion F protein antagonist (mAb)
- In plain language
- A lab-made antibody that locks onto RSV's surface protein before it can change shape to infect cells, protecting infants from severe RSV illness for months after a single dose.
- How it works
- Nirsevimab-alip is a recombinant human IgG1-kappa monoclonal antibody that binds a conserved epitope in antigenic site zero on the prefusion conformation of the RSV fusion (F) glycoprotein, with dissociation constants of 0.12 nM for RSV subtype A and 1.22 nM for subtype B. By locking onto the prefusion form specifically, it neutralizes the virus by blocking the conformational change the F protein must undergo to fuse the viral and host cell membranes, preventing viral entry. Its Fc region carries a triple amino-acid substitution (YTE) that increases binding to the neonatal Fc receptor, extending serum half-life to roughly 71 days — long enough that a single dose provides protection through an entire RSV season, unlike older RSV antibodies requiring monthly dosing.
- Therapeutic applications
- Indicated for the prevention of RSV lower respiratory tract disease in neonates and infants born during or entering their first RSV season, and in children up to 24 months of age who remain vulnerable to severe RSV disease through their second RSV season.
- Class
- Monoclonal antibody
- Therapeutic area
- Infectious Disease
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