Clesrovimab: First Approval

Area of Science:

• Immunology
• Virology
• Pharmacology

Background:

• Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract infections in infants.
• Current prevention strategies for RSV are limited, necessitating new therapeutic options.

Purpose of the Study:

• To summarize the development and milestones leading to the US approval of Clesrovimab for RSV disease prevention in infants.
• To highlight the scientific advancements enabling a long-acting, single-dose monoclonal antibody for infant RSV prophylaxis.

Main Methods:

• Development of Clesrovimab, a monoclonal antibody targeting a conserved epitope on the RSV fusion protein.
• Incorporation of YTE triple amino acid substitution in the Fc region to enhance neonatal Fc receptor binding and prolong serum half-life.
• Clinical evaluation of Clesrovimab for safety and efficacy in preventing RSV disease.

Main Results:

• Clesrovimab effectively blocks RSV viral entry into host cells, providing passive immunity.
• The YTE modification resulted in an extended serum half-life, allowing for a single, weight-independent dose.
• Clesrovimab received US approval on June 9, 2025, for preventing RSV lower respiratory tract disease in neonates and infants.

Conclusions:

• Clesrovimab represents a significant advancement in the prevention of RSV disease in vulnerable infant populations.
• The successful development and approval of Clesrovimab offer a new, convenient prophylactic option for protecting infants during their first RSV season.