Development of Motavizumab, an Ultra-potent Antibody for the Prevention of Respiratory Syncytial Virus Infection in the Upper and Lower Respiratory Tract

• Published in: Journal of molecular biology 2007-05, Vol.368 (3), p.652-665
• Main Authors: Wu, Herren, Pfarr, David S., Johnson, Syd, Brewah, Yambasu A., Woods, Robert M., Patel, Nita K., White, Wendy I., Young, James F., Kiener, Peter A.
• Format: Article
• Language: English
• Subjects: affinity maturation; Amino Acid Sequence; Animals; Antibodies, Monoclonal - genetics; Antibodies, Monoclonal - pharmacokinetics; Antibodies, Monoclonal - therapeutic use; Antibodies, Monoclonal, Humanized; antibody engineering; Antiviral Agents - pharmacokinetics; Antiviral Agents - therapeutic use; Cell Line; Cross Reactions; Female; Humans; Lung - metabolism; Macaca fascicularis; Molecular Sequence Data; motavizumab; Mutation; Neutralization Tests; Palivizumab; Pan troglodytes; Respiratory syncytial virus; Respiratory Syncytial Virus Infections - prevention & control; Respiratory Syncytial Viruses - drug effects; Respiratory Syncytial Viruses - physiology; Respiratory System - drug effects; Respiratory System - immunology; Respiratory System - virology; Sigmodontinae; Tissue Distribution; Virus Replication - drug effects
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2007.02.024

Respiratory syncytial virus (RSV) is the leading cause of viral bronchiolitis and pneumonia in infants and children. Currently, palivizumab is the only approved monoclonal antibody (mAb) for prophylaxis of RSV. However, a small percentage of patients are not protected by palivizumab; in addition, palivizumab does not inhibit RSV replication effectively in the upper respiratory tract. We report here the development and characterization of motavizumab, an ultra-potent, affinity-matured, humanized mAb derived from palivizumab. Several palivizumab variants that enhanced the neutralization of RSV in vitro by up to 44-fold were generated; however, in vivo prophylaxis of cotton rats with these antibodies conferred only about a twofold improvement in potency over palivizumab. This unexpected small increase of in vivo potency was caused by poor serum pharmacokinetics and lung bio-availability that resulted from unexpectedly broad tissue binding. Subsequent analyses revealed that changes at three amino acids arising from the affinity maturation markedly increased the non-specific binding to various tissues. Our results suggested that kon-driven mutations are more likely to initiate non-specific binding events than koff-driven mutations. Reversion of these three residues to the original sequences greatly diminished the tissue binding. The resulting mAb, motavizumab, binds to RSV F protein 70-fold better than palivizumab, and exhibits about a 20-fold improvement in neutralization of RSV in vitro. In cotton rats, at equivalent concentrations, motavizumab reduced pulmonary RSV titers to up to 100-fold lower levels than did palivizumab and, unlike palivizumab, motavizumab very potently inhibited viral replication in the upper respiratory tract. This affinity-enhanced mAb is being investigated in pivotal clinical trials. Importantly, our engineering process offers precious insights into the improvement of other therapeutic mAbs.