A single tri-epitopic antibody virtually recapitulates the potency of a combination of three monoclonal antibodies in neutralization of Botulinum Neurotoxin Serotype A

Authors: LOU, JIANLONG - University Of California; WEN, WEIHUA - University Of California; CONRAD, FRASER - University Of California; MENG, QI - University Of California; DONG, JIANBO - University Of California; SUN, ZHENGDA - University Of California; GARCIA-RODRIGUEZ, CONSUELO - University Of California; FARR-JONES, SHAUNA - University Of California; Cheng, Luisa; Henderson, Thomas; BROWN, JENNIFER - Us Army Research; SMITH, THERESA - Us Army Research; SMITH, LEONARD - Us Army Research; CORMIER, ANTHONY - University Of California; MARKS, JAMES - University Of California

Submitted to: Toxins
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2018
Publication Date: 2/15/2018
Citation: Lou, J., Wen, W., Conrad, F., Meng, Q., Dong, J., Sun, Z., Garcia-Rodriguez, C., Farr-Jones, S., Cheng, L.W., Henderson Ii, T.D., Brown, J., Smith, T.J., Smith, L.A., Cormier, A., Marks, J.D. 2018. A single tri-epitopic antibody virtually recapitulates the potency of a combination of three monoclonal antibodies in neutralization of Botulinum Neurotoxin Serotype A. Toxins. 10(2):84. doi: 10.3390/toxins10020084.
DOI: https://doi.org/10.3390/toxins10020084

Interpretive Summary: Botulinum neurotoxins (BoNT) are some of the most lethal natural toxins. Equine antitoxin and a human botulism immune globulin are currently the only therapeutics available to treat adult and infant botulism, respectively. The equine antitoxins have side effects of serum sickness and anaphylactic shock, while the human antitoxins are made from the blood of BoNT immunized donors and is in short supply. Humanized serotype-specific monoclonal antibody (mAb) based antitoxin consisting or a combination of three different antibodies have been shown, in clinical trials, to be effective against BoNT intoxication with no serious reported adverse events. However, the use of multiple antibodies per serotype of toxin presents a manufacturing and quality control challenge. In this study, a single antibody that can recognize three different toxin regions that can effectively neutralize BoNT serotype A was developed. This new type of antibody would be easier and cheaper to produce and have similar toxin neutralization potential as a combination of antibodies, thus making it a potential better alternative to current therapeutic options.

Technical Abstract: Botulinum neurotoxins (BoNTs) are one of the six highest-risk threat agents for bioterrorism, due to their extreme potency and lethality, ease of production, and need for prolonged intensive care of intoxicated patients. The current standard of treatment, equine antitoxin, has a high incidence of allergic reactions, a short serum half-life leading to reintoxication, and it cannot be used prophylactically. Previous studies have shown that no single monoclonal antibody (mAb) neutralizes BoNT with the requisite potency, however, combining mAbs binding non-overlapping epitopes leads to highly potent BoNT neutralization, with rapid clearance of BoNT from the circulation. The three-mAb combination for BoNT/A (XOMA 3AB) caused no serious adverse events in a Phase I clinical trial. While highly potent in animal models, the three-mAb combination poses unique development and manufacturing challenges. Thus, to streamline development and production of antitoxin for all seven serotypes of BoNT in more cost effective ways, we sought to achieve the potency of multiple mAb combinations in a single IgG-based molecule that has a long serum half-life and potency comparable to the parental three-antibody combinations. Here we present the design and in vivo protection by a single tri-epitopic IgG1-based mAb (TeAb) incorporating the binding sites of each of the three parental mAbs in the antitoxin cocktail for BoNT/A. The murine pharmacokinetics and potency of this single molecular TeAb is similar to that of the three parental mAbs against BoNT/A. The approach taken here could be applied to the design and creation of other antibody drugs for any other multi- epitope targets, including other BoNT serotypes. .