Optimization of a Human Anti-polio Monoclonal Antibody as a Potential Therapeutic Modality

Vaccines have been an essential tool in bringing the world close to polio eradication, with over 99.9% of the global population free of poliovirus. No antiviral drugs or monoclonal antibody products, however, are currently licensed for treatment of polio. We previously isolated a human monoclonal antibody (9H2) with potent neutralizing activity against all three poliovirus serotypes. To advance 9H2 as a therapeutic candidate, we optimized its sequence to extend serum half-life and improve manufacturability.

Methods

A Multi-Attribute Method under stress conditions identified post-translational modification sites, and Abacus™ ranked sequence liabilities. Six amino acid substitutions were introduced into the variable regions, generating 23 combinatorial variants. Codon-optimized genes were synthesized and engineered into a human immunoglobulin G1 backbone containing crystallizable fragment (Fc) mutations (M428L/N434S) to extend serum half-life. Constructs were transfected into CHO-K1 cells to generate stable pools in 24-well plates. Protein A–purified antibodies were characterized using biophysical assays and an in vitro poliovirus neutralization assay.

Results

All variants retained high in vitro neutralizing activity against poliovirus. A lead candidate was selected based on integrated assessment of biophysical properties across eight assays and expression yield.

Conclusions

Structure-guided engineering and experimental evaluation enabled optimization of the 9H2 antibody sequence and identification of a lead candidate suitable for clinical manufacturing as a potential anti-poliovirus immunotherapeutic agent.