Development of Non-Animal Antitoxins

Antitoxins Are Essential Medicines in Need of Modernisation

Antitoxins are life-saving drugs, but the way they are manufactured has not changed in more than 100 years. Almost all commercial antitoxins have been manufactured using serum from equines who have been hyperimmunised by repeated toxin injections. Large volumes of blood are then drawn from them – up to 15% of their total blood volume at a time – as often as every four weeks.1 The animals are subjected to this process of repeated injections and blood draws for years or even for their entire lives.

In humans, antitoxins made from the blood of horses and other animals may cause hypersensitivity and serum sickness, and they also present the risk of transmitting viruses and other sources of disease between species – an important consideration in light of the cross-species origin of COVID-19.2-4  Even in ideal circumstances, equine-derived antitoxins – like all blood products – expire quickly and must be continuously harvested from live animals. In many instances, this short shelf life has led to massive global shortages of antitoxins that are not available when they are needed the most.5

As with all antibodies and affinity reagents, antitoxins can be manufactured using a number of non-animal approaches,6-9 including antibody phage display. Using human antibody gene libraries and cell cultures in place of horses’ immune systems, antibody phage display yields diverse sets of toxin-neutralizing antibody fragments that can be optimised for their binding affinity and stability. Non-animal production platforms eliminate many of the practical drawbacks of equine-derived antitoxins, including avoiding the possibility of serum sickness or zoonotic disease transmission. Unlike antitoxins isolated from horse blood, non-animal antitoxins can be optimised to have a significantly longer shelf life that is more amenable to producing long-lasting stockpiles.

Starting Points: Diphtheria Antitoxin and Black Widow Spider Antivenom

With this in mind, PETA Science Consortium International e.V. funded the creation of fully human recombinant monoclonal antibodies capable of neutralising diphtheria toxin (see the publication here). The work was conducted at the Institute for Biochemistry, Biotechnology, and Bioinformatics at the Technische Universität (TU) Braunschweig in Germany. Working with our project partners, the Science Consortium is in discussions with regulatory authorities, pharmaceutical companies, and global health organisations to develop the antibodies into a therapeutic diphtheria antitoxin product that can replace the use of horses and other equines.

Based on the success of this project and the continued need for non-animal replacements for animal serum–derived therapeutic drugs, the Science Consortium has been joined by the Center for Contemporary Equine Studies in co-funding the development of fully human recombinant monoclonal antibodies capable of neutralising black widow spider venom. This work is also being carried out at the Institute for Biochemistry, Biotechnology, and Bioinformatics at TU Braunschweig as well as at the Ensenada Center for Scientific Research and Higher Education in Mexico.

 

Antibody Phage Display: A Superior Platform for Antitoxin Development

In 2015, inspections of equine-serum production facilities in India found substandard living conditions, a lack of sufficient veterinary care, and routine violations of basic animal welfare laws. In addition to painful complications caused by being repeatedly injected with toxins and then bled, the animals showed signs of lameness, diseased hooves, eye abnormalities, and malnutrition. Sick or elderly equines were not separated from healthy ones, and the staff often lacked the training and medication necessary to provide basic medical care. These facilities did not provide animals who were too debilitated to recover from advanced illness or injury with humane euthanasia.

Read more about this issue in a Reuters Health article here and in Science here.

Note: The following video contains footage that may be disturbing to some viewers.

 

References

1Committee for the Purpose of Control and Supervision of Experiments on Animals. Government of India. Care and management of equines used in the production of biologicals. 2001.

2Both L, Banyard AC, van Dolleweerd C, Wright E, Ma JK, Fooks AR. Monoclonal antibodies for prophylactic and therapeutic use against viral infections. Vaccine. 2013;31(12):1553-1559.

3Both L, White J, Mandal S, Efstratiou A. Access to diphtheria antitoxin for therapy and diagnostics. Euro Surveill. 2014;19(24):1-6.

4Wenzel EV, Bosnak M, Tierney R, et al. Human antibodies neutralizing diphtheria toxin in vitro and in vivo. Sci Rep. 2020;10(571).

5Both, et al. Access to diphtheria antitoxin for therapy and diagnostics.

6Bradbury ARM, Sidhu S, Dübel S, McCafferty J. Beyond natural antibodies: the power of in vitro display technologies. Nat Biotechnol. 2011;29:245-254.

7Frenzel A, Schirrmann T, Hust M. Phage display-derived human antibodies in clinical development and therapy. MAbs. 2016;8(7):1177-1194.

8Gray AC, Sidhu SS, Chandrasekera PC, Hendriksen CFM, Borrebaeck CAK. Animal-friendly affinity reagents: replacing the needless in the haystack. Trends Biotechnol. 2016;34(12):960-969.

9Groff K, Brown J, Clippinger AJ. Modern affinity reagents: recombinant antibodies and aptamers. Biotechnol Adv. 2015;33(8):1787-1798.