Dual-target defense: bispecific antibodies revolutionize pertussis toxin neutralization

Bispecific antibodies target two epitopes on the pertussis toxin protein, enhancing toxin neutralization. Engineered using “knobs-into-holes” technology, they form stable heterodimers, offering similar efficacy to antibody mixtures but with streamlined manufacturing and regulatory benefits.

Background

Pertussis, or whooping cough, caused by Bordetella pertussis, remains a significant health threat, particularly for infants and young children. Despite widespread vaccination efforts, pertussis incidence has resurged in many regions, attributed to limitations in the current acellular vaccines, which do not provide long-lasting immunity. Antibiotic treatments, while effective at eliminating the bacteria, do not neutralize the pertussis toxin (PT), a primary virulence factor responsible for severe symptoms such as leukocytosis and immunosuppression.

Existing monoclonal antibodies targeting PT have shown promise, but their clinical application is hindered by the complexity and cost of manufacturing antibody cocktails. These cocktails also require extensive safety and efficacy evaluations for each component and the mixture, complicating regulatory approval. There is a need for more efficient and cost-effective therapeutic solutions that can provide comprehensive neutralization of PT and mitigate the effects of pertussis.

Technology Description

Bispecific antibodies target two distinct epitopes on the pertussis toxin protein, one on the S1 subunit and another on the homologous S2 and S3 subunits. The bispecific antibody is engineered using "knobs-into-holes" technology, where specific mutations (T366Y on the 1B7 antibody and Y407T on the 11E6 antibody) facilitate the formation of a stable heterodimer. This bispecific antibody exhibits similar binding affinity and in vitro toxin neutralization as the binary mixture of the two parent antibodies.

In vivo studies using a mouse model of PT-induced leukocytosis demonstrate that the bispecific antibody retains the synergistic effect observed with the antibody mixture, significantly reducing white blood cell counts and neutralizing the toxin.

This approach not only maintains high efficacy but also enhances stability and circulating half-life due to the human IgG1 framework, making it a more efficient and potentially more effective therapeutic option for treating pertussis. This bispecific format also offers streamlined manufacturing and regulatory benefits compared to the antibody cocktail, while maintaining therapeutic efficacy.

Benefits

Simultaneous targeting of two distinct epitopes on pertussis toxin enhances neutralization efficacy.
Retains synergistic effect of parent antibodies in vivo, reducing white blood cell counts and neutralizing toxin
Improved stability and extended in vivo half-life due to FcRn binding
Potential for lower dosages and less frequent dosing due to high binding affinity
Streamlined manufacturing process compared to antibody cocktails, reducing regulatory complexity and costs
Reduced risk of pathogen escape variants by targeting multiple epitopes
Enhanced therapeutic potential for treating infectious diseases, especially in high-risk populations