Antibodies are proteins the body produces when an infection occurs. They attach to a virus and help eliminate it. Antibodies can be monoclonal or polyclonal. A monoclonal antibody is an antibody produced by cloning a particular white blood cell. It is derived from a one cell clone (a single B cell clone). All subsequent derived antibodies are traced back to a distinctive parent cell in this way. Therefore, a single, pure form of antibody is a monoclonal antibody. Monoclonal antibodies are concentrated forms of specific antibodies that function against coronavirus.

It is complex and costly to produce monoclonal antibodies. In the laboratory, monoclonal antibodies can be produced at high, standardized doses. As therapeutic agents, monoclonal antibodies are being widely used. Monoclonal antibodies can have monovalent affinity, bound only to the same epitope. Monoclonal antibody therapy is effective in reducing the levels of the virus that causes Covid-19 and helps to prevent patients from going to the emergency room or hospital. 

This entire method of making monoclonal antibodies takes a long period of time and uses expensive materials. Some estimate that the cost of manufacturing one gram of marketed monoclonal antibodies is between $95 and $200. This does not include the cost of research, production, or packaging & distribution.

Researchers are hopeful that monoclonal antibodies might help to prevent and treat early Covid-19 infections. Since they originate in the blood of people who have recovered from Covid-19, they can directly target the SARS-CoV-2 virus. When administered, they will provide fast protection against infection, as monoclonal antibodies enter the bloodstream immediately. Researchers are hopeful that, in helping to control the pandemic, monoclonal antibodies will complement vaccines. They can treat all people, including the elderly and young children, and immunocompromised persons.

Polyclonal antibodies are heterogeneous mixtures that are produced naturally by different B cell clones in the body. In monoclonal antibodies, there is monovalent affinity, bound only to the same epitope (the antibody-recognized part of the antigen). By contrast, polyclonal antibodies bind to many epitopes.

Monoclonal and polyclonal antibodies have many benefits. Viral levels and the resulting damage to the lungs are minimized by monoclonal antibodies. Monoclonal antibodies improved symptoms in non-hospitalized covid-19 patients and allowed non-hospitalized patients to recover more rapidly. Treatment is only carried out in people who did not have antibodies to SARS-CoV-2. It also performed better in people who had higher levels of the virus.

There are two or more lab-engineered antibodies used in the polyclonal antibody cocktail therapy. The monoclonal antibody that attacks the spike protein used by the virus to drill into healthy cells and another antibody that attacks another component of the coronavirus. The drug’s purpose is to stop the replication of the virus. The purpose of multiple antibodies being combined is to prevent mutations seen with individual antibodies from escaping.

Two pharmaceutical companies are currently making monoclonal antibodies. They are Regeneron Pharmaceuticals Inc. and Eli Lilly. The polyclonal antibody cocktail from Regeneron is a two-antibody combo drug. The experimental drugs are concentrated forms of antibodies that have performed best in the laboratory against coronavirus. In principle, they start helping right away. The one-time treatment is given through an IV infusion. The usual dose is 2.4-gram infusion.  President of United States received an 8-gram infusion of the treatment.

Molecular Model of Regeneron REGEN-COV-2

 Molecular model of REGN-COV2, consisting of REGN10933 and REGN10987 binding to the spike RBD of SARS-CoV-2. This binding prevents binding to the ACE2 receptor on human cells. Source: REGN presentation of REGN-COV2 results.

REGN-COV2 is a cocktail of two antibodies. Both antibodies, REGN10933 and REGN10987, bind to the receptor binding domain (RBD) of the SARS-CoV-2 spike protein (Figure). Targeting two separate parts of the spike protein makes it harder for a mutation to render the cocktail ineffective. For example, a mutation found on one virion (the complete, infective form of a virus) might lead to REGN10933 being no longer effective at binding to that virion. Elsewhere, another virion might have a mutation that leads to REGN10987 no longer being effective. The chances of a virion having both mutations, however, are slim, meaning that the odds of resistance developing to REGN-COV2 are much smaller than would be achieved with one antibody alone.

Eli Lilly and Regeneron Pharmaceuticals Inc. are urging the U.S. government to allow emergency use of their antibody drugs, to help the immune system eliminate the virus.