19 – How does an antibody drug work and when is it useful?


The European Medicines Agency has approved the use of a drug for antibody therapy against Covid-19. It is a preparation from the US biotech company Regeneron. How do such remedies work and when are they useful? We answer the most important questions.

Antibody drugs against Covid-19 will initially be used in university hospitals. According to the assessment of the drug authority, they are suitable for the treatment of corona patients who do not yet need oxygen supply, but have a high risk of their condition seriously deteriorating. With the decision of the authority, the preparation can be used in the European Union even before it is officially approved for the market.

The federal government had already bought 200,000 cans of antibody funds for 400 million euros in January. According to the Federal Ministry of Health, in addition to the Regeneron drug REGN-COV2, the drug Bamlavinimab is also involved. Both agents had already received emergency approval in the USA.

What are antibodies

Antibodies are proteins – that is, proteins – that arise as part of the body’s immune response. In other words: If you become infected with a pathogen – for example a virus – the body’s defense system becomes active and produces defense molecules that are directed against the characteristic structures of this pathogen: the antibodies. These are produced in large quantities in the course of the infection and are able to bind the pathogen, neutralize it and render it harmless. After the infection, the body “remembers” what the pathogen looks like so that it can react more quickly in the event of a second infection.

In the case of an infection with Sars-CoV-2, antibodies can be detected about two weeks after the infection, in the case of illness, about one week after the onset of symptoms. According to new findings, published in the specialist journal Science, another type of antibody can be detected in the blood of those who have recovered for another six to eight months. In addition to the formation of antibodies, there are other parts of the immune response that help fight the pathogen. Other cell types of the immune system are involved in this.

What are monoclonal antibodies?

“Monoclonal” means that the antibodies all arise from a cell clone, that is, they are the same. They are manufactured in the laboratory and are directed highly specifically against a characteristic feature of the pathogen, such as part of the “spike” protein that Sars-CoV-2 uses to penetrate certain body cells. In contrast, recovered Covid-19 patients have a mixture of different antibodies against parts of the virus in the blood; one speaks of polyclonal antibodies. Each type of antibody is directed against a certain characteristic of the virus, so it can bind to different places.

How are antibodies used as a drug against Covid-19?

The principle is to give the body a head start on time: by giving antibodies, one skips the phase of the immune response in which the body is busy recognizing characteristic virus structures and producing suitable antibodies itself. In connection with the corona pandemic, two preparations from the USA are known, namely those from Regeneron and Eli Lilly.

The main difference: Eli Lilly’s drug contains a type of monoclonal antibody, while Regeneron’s drug contains a mixture of two monoclonal antibodies. The advantage of a mixture is that the additional points of attack increase the likelihood of effectiveness. Former US President Trump was treated, among other things, with the Regeneron preparation, which was not yet approved in the USA at the time.

What are the side effects?

In general, therapies with antibodies are well researched because they are also used to treat other diseases such as cancer and rheumatism. In a clinical study, people treated with the Regeneron drug did not experience increased severe side effects compared to the control group. According to the US Food and Drug Administration (FDA), Eli Lilly’s drug had serious side effects in two of 850 cases examined. The following applies to both preparations: There is a risk of hypersensitivity reactions. In addition, there is not enough data yet to be able to make a definitive statement on this issue. Some side effects may not yet be known.

Antibodies and Virus Mutations

Preparations containing a mixture of different monoclonal antibodies can help prevent mutations from taking hold. If the virus multiplies, such variants arise – most of them are of no advantage or even harmful to the pathogen and disappear again. In rare cases, a mutation or a combination of different mutations can have advantages for the virus, for example because it can spread faster, as is the case with the virus variants first detected in Great Britain and South Africa.

If the virus is only confronted with a single, very specific “weapon” such as a type of monoclonal antibody, mutants that this antibody does not recognize will prevail. One speaks of selection pressure. Mixing different antibodies will reduce the chances of this happening.

Why not use antibodies as a standard therapy against Covid-19?

Antibody therapy is not always useful. Because of its mode of action, such a treatment achieves the best results, especially at the beginning of an illness. Then it can prevent serious disease progression. The study data available so far show that those who received the drug in the first ten days after infection benefited most from the treatment.

Patients who already have severe Covid 19 symptoms – for example, are in hospital and are receiving oxygen – are not allowed to receive such a drug. One possible explanation for this is that severe symptoms of a second phase of Covid-19 are caused by the reaction of the immune system. An active ingredient against the virus would simply come too late here. In addition, such a drug must be administered by infusion, which in this case takes about an hour and can only be done in clinics. In addition, the production of antibodies is complex and therefore expensive. The cost is estimated at around 2,400 euros per dose.

Another problem: Antibodies are foreign proteins – and what the body does not know it breaks down: The agent would therefore have a limited effectiveness and – unlike a vaccination, for example – does not protect against future infections.

Special case of convalescent plasma

Convalescent plasma is blood plasma from recovered patients. It contains – often depending on the severity of the illness – antibodies that the immune system has produced itself, i.e. a mixture of polyclonal antibodies. If it is available, it can be given to newly infected people to protect them from illness or a severe course of the disease. In this case one speaks of passive immunization. This type of therapy has already been used several times in epidemics, such as the 2014 Ebola outbreak in West Africa. The Paul Ehrlich Institute considers such a treatment to be a possible therapy option for Covid-19. A first study on this has been running in Germany since last summer.

(Stand 26.02.2021)

Further articles on the coronavirus

We have created a news blog. In view of the large amount of information, this provides an overview of the most important current developments.

+ Covid-19: Current figures on the coronavirus in Germany (as of March 30)
+ Holidays: What will happen to the Easter holiday? (As of March 23)

Test and protection

+ Protection: The vaccination ordinance: who will be vaccinated first, who will be vaccinated later? (As of March 4th)
+ Vaccination appointment: how can I get vaccinated when and where? (As of March 4th)
+ Vaccines: When children could also be vaccinated (as of March 26)
+ Vaccinations: What is known about the side effects of vaccines (as of March 19)
+ Sick people: New findings in the search for drugs (as of March 8th)
Treatment: How does an antibody drug work and when does it make sense? (As of February 26th)

Contagion and Transmission

+ Virus variants: how dangerous are the new mutations of the coronavirus? (Status: 13.03.)
+ Opponents of infection protection measures: What AfD and lateral thinkers have to do with the spread of the coronavirus in Germany (as of 02/09)
+ Transfer: What role aerosols play (as of January 22)
+ Excess mortality: how deadly is the coronavirus really? (Status: 13.03.)
+ Travel warning: The current list of risk areas (as of March 27)

You can also find the Dlf news on Twitter at: @DLFNews.

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