Where do you get the antibodies from?
You could theoretically use donor blood from infected patients, but apparently it is still unclear if the transmission of those antibodies is safe. Also, those patients who generate the antibodies for everyone else couldn’t benefit from the treatment. And you‘d always need some who develop their own immune response. This is like a pyramid scheme, only the other way around.
You could use monoclonal antibodies but the production cost is really expensive (as in a single dose costs > 50k$ for any type of antibody), and this is due to the complex production. Once patents expire, the cost for generics is expected to fall only by 20% (compared to 80% for non-mAb medication) (sorry for the pay-wall).
To my knowledge, we do not have other viable options at the moment to produce antibodies in a large fashion.
Antibodies are limited in usage. They only work against the specific antigen. Many antibiotics and antivirals work at least against a class of pathogens, if not more. They usually target vital intracellular enzymes or factors (gyrase inhibitors block the gyrase enzyme, vital for procaryontic cell replication as an example). Intracellular antibodies do exist, but they are usually expressed in transgenic animals for research purposes (included into the genome), and research for human cytosolic antibodies humans is still basic. You are effectively limited to membrane proteins and glycosides of the outer cell membrane as possible targets, which are not as universally conserved as the replication machinery.
Monoclonal antibodies have been testet for Ebola, but the first trial concluded with only 72 patients because the pandemic was waning.
This paper highlights some limitation of mAbs:
Second, for fatal diseases, such as rabies, where highly effective polyclonal antibodies are available, but short in supply, conducting randomized controlled trials present ethical and logistical challenges. Therefore, researchers need alternative study designs to evaluate mAbs against such diseases. Furthermore, polyclonal antibodies are conceived to neutralize more virus strains than mAbs. [...]
Fourth, high costs may limit access, especially to those in low-resource settings. Although the production costs of mAbs have been reduced over the last decade, the cost is still high (about 100 United States dollars per gram), especially if several grams are needed for treatment. [...]
Fifth, for several disease targets, investors and people working with product development need clarity on whether public health agencies will procure and use the new therapeutics or postexposure prophylactics. Without a known market, biotechnology companies are hesitant to invest in mAb research and development. [...]
Finally, the use of approved mAbs products for persistent infections and/or mutating pathogens is of concern. As with other drugs, antimicrobial resistance to mAbs is a potential threat. However, this threat may be overcome by targeting highly conserved epitopes or by using antibody cocktails containing more than one mAb. [..]
Sparrow, Erin et al. “Therapeutic antibodies for infectious diseases.” Bulletin of the World Health Organization vol. 95,3 (2017): 235-237. doi:10.2471/BLT.16.178061
This is the conclusion of a nature paper on the issue:
A third key challenge is the complexity of pathology, epidemiology, and immunology that can be associated with infection. The way kinetics of infection informs therapeutic strategy, for instance, explains why no dengue mAbs are in clinical trials and why vaccination is the preferred method to control influenza. For dengue and influenza A, symptoms often appear after the peak of viremia; an antibody applied for passive immunotherapy would have to be used before the onset of symptoms to be early enough to avoid viremia. One potential solution is matching a therapeutic antibody with a rapid, point of care diagnostic test. The diagnostic could be used to identify patients with infection and susceptibility to severe disease who would benefit from passive immunotherapy with the therapeutic antibody. Finally, viruses can have complexity that prevents development of a single lasting treatment, for instance multiple strains, rapid evolution, and obscure mechanisms of infection and neutralization escape.
Salazar, G., Zhang, N., Fu, T. et al. Antibody therapies for the prevention and treatment of viral infections. npj Vaccines 2, 19 (2017). https://doi.org/10.1038/s41541-017-0019-3
However, recently there has been an increased effort to create antibody treatment for COVID-19 and first trials are on the way.
No one has yet completed a large, randomized study of an antibody therapy against COVID-19, but results from such trials are expected in the coming months. Lundgren’s trial, announced on 4 August, aims to enrol 1,000 people with COVID-19. Another large trial, sponsored by the NIH and Regeneron, a biotechnology company in Tarrytown, New York, launched on 6 July and will test a cocktail of two antibodies against SARS-CoV-2. Results are expected in late September.
Ledford, H. (2020). Antibody therapies could be a bridge to a coronavirus vaccine — but will the world benefit? Nature, 584(7821), 333-334. doi:10.1038/d41586-020-02360-y
The ACTIV-3 study will begin by studying the investigational monoclonal antibody LY-CoV555, which was identified in a blood sample from a recovered COVID-19 patient. Antibodies are infection-fighting proteins made by the immune system that can bind to the surface of viruses and prevent them from infecting cells. Synthetic versions of antibodies can be reproduced in a laboratory. These manufactured antibodies are known as monoclonal antibodies. The LY-CoV555 antibody was discovered by Abcellera Biologics (Vancouver, British Columbia) in collaboration with NIAID’s Vaccine Research Center. Subsequently, it was developed and manufactured by Lilly Research Laboratories, Eli Lilly and Company (Indianapolis, Indiana), in partnership with AbCellera. The investigational product also is being tested in another ongoing NIAID study, ACTIV-2, which is studying its safety and efficacy in people with mild to moderate symptoms of COVID-19 who have not been hospitalized. Safety data and other findings will be shared across the ACTIV-2 and ACTIV-3 studies through the DSMB.
Elizabeth Deatrick. (2020) NIH launches clinical trial to test antibody treatment in hospitalized COVID-19 patients. NIH.gov
It will be interesting to see if they are efficient and effective at treating COVID-19. However, they will not be able to prevent infections or prevent transmission. To control the pandemic, it makes sense to also focus on vaccines at the same time.
Prevention is much better! Think about it, rather than investing money for novel antibody therapies, you could invest the money to develop vaccines and prevent people from getting infected in the first place.
This means you‘d have lower health care cost because patients wouldn’t need to be treated, and for the patient it is also better because they won’t suffer from the infectious disease (even if there is a therapy, it’s still unpleasant and dangerous to become ill).