Mechanism of action for Beyfortus® (nirsevimab-alip) 50mg and 100mg Injection
A monoclonal antibody injection for prevention of RSV disease
Beyfortus was approved to prevent RSV lower respiratory tract disease by the FDA in July of 2023¹˒²:
Beyfortus® (nirsevimab) is a recombinant human immunoglobulin G1 kappa (IgG1κ) monoclonal antibody (mAb) designed to prevent respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants.¹
Unlike infection or vaccination, RSV antibody therapy does not stimulate the immune system. Instead, mAbs provide direct protection against disease, representing a form of passive immunization against RSV disease.² Protection is typically at its peak in the weeks following administration of Beyfortus® but diminishes gradually over time.²
- Neonates and infants born during or entering their first RSV season
- Children up to 24 months who remain vulnerable to severe RSV disease through their second RSV season
Beyfortus® (nirsevimab) is a recombinant human immunoglobulin G1 kappa (IgG1κ) monoclonal antibody (mAb) designed to prevent respiratory syncytial virus (RSV) lower respiratory tract disease in neonates and infants.¹
Unlike infection or vaccination, RSV antibody therapy does not stimulate the immune system. Instead, mAbs provide direct protection against disease, representing a form of passive immunization against RSV disease.² Protection is typically at its peak in the weeks following administration of Beyfortus® but diminishes gradually over time.²
How Beyfortus® protects against RSV disease by preventing membrane fusion
Beyfortus® is a protein-directed fusion inhibitor that provides long-acting passive immunity to RSV disease by binding to a conserved epitope on the RSV prefusion F protein, interfering with cellular membrane fusion, thus preventing viral entry into cells.¹
The mechanism of action of RSV prophylaxis and antibody therapy Beyfortus® is explained in the video below.
The mechanism of action of RSV prophylaxis and antibody therapy Beyfortus® is explained in the video below.
The role of glycoproteins in RSV
RSV is coated with two types of glycoproteins, the attachment glycoprotein (G protein) and the fusion glycoprotein (F protein).³ Only the F protein is essential for RSV entry into cells lining the respiratory tract.³
The RSV F protein structure exists as a type I viral fusion glycoprotein that forms a trimeric complex and mediates viral entry. ⁴,⁵
The RSV F protein structure exists as a type I viral fusion glycoprotein that forms a trimeric complex and mediates viral entry. ⁴,⁵
Blocking viral attachment and entry into bronchial epithelial cells
Upon infection, the RSV F protein, typically responsible for facilitating pH-independent viral membrane fusion with the host-cell plasma membrane, triggers the merging of adjacent cells when expressed on the cell surface.³
This membrane fusion process results in the formation of syncytia, large multinucleated structures that can induce epithelial lesions in the upper respiratory tract.³,⁶ Formation of syncytia (cell-cell fusion) is what gives RSV its characteristic name.³,⁶
This membrane fusion process results in the formation of syncytia, large multinucleated structures that can induce epithelial lesions in the upper respiratory tract.³,⁶ Formation of syncytia (cell-cell fusion) is what gives RSV its characteristic name.³,⁶
YTE substitution prolongs the half-life of Beyfortus® RSV antibody therapy
Beyfortus® RSV antibody therapy is long-acting due to a specially designed triple amino acid substitution (YTE) in its fragment crystallizable (Fc) region, increasing its affinity to the neonatal Fc receptor.⁸
This YTE substitution in the Fc segment of Beyfortus® prolongs its serum half-life, and is designed to provide season-long protection that extends through 5 months after injection with a single intramuscular dose. ¹,⁸
Specifically, the YTE modification results in a long anti-RSV antibody half-life extension from 21–28 days to 87–117 days.¹
This YTE substitution in the Fc segment of Beyfortus® prolongs its serum half-life, and is designed to provide season-long protection that extends through 5 months after injection with a single intramuscular dose. ¹,⁸
Specifically, the YTE modification results in a long anti-RSV antibody half-life extension from 21–28 days to 87–117 days.¹
Discover more about Beyfortus®
Dosing and Administration
