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

The European Medicines Agency has approved the use of a drug to treat COVID-19 antibodies. It’s a preparation from the US biotech company Regeneron. How do these treatments work and when are they helpful? We answer the most important questions.

The antibody drugs against Covid-19 will initially be used in university hospitals. According to the evaluation of the Medicines Authority, it is suitable for treating Corona patients who do not yet need a supply of oxygen, but are at high risk of seriously deteriorating their condition. By 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 boxes of antibody money for € 400 million in January. According to the Federal Ministry of Health, in addition to the drug Regeneron REGN-COV2, this also includes the agent Bamlavinimab. Both agents have already received emergency approval in the United States.

What are antibodies

Antibodies are proteins – that is, proteins – that are created as part of the body’s immune response. In other words, if you are infected with a pathogen – for example a virus – the body’s defense system becomes active and produces defensive molecules directed against the characteristic structures of that pathogen: antibodies. It is produced in large quantities in the context of infection and is able to restrict the pathogen, neutralize it and make it harmless. After infection, the body “remembers” what the pathogen looks like so that it can respond faster in the event of a second infection.

If infected with Sars-CoV-2, antibodies can be detected about two weeks after infection, and in disease, about a week after symptoms appear. Another type of antibody, according to the new findings, has been published in the journal Science, It can still be detected in the blood of those who have recovered for 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 types of immune system cells are involved.

What are monoclonal antibodies?

The word “monoclonal” means that all antibodies originate from a cell clone, that is, they are the same. It is manufactured in the laboratory and is directed very specifically against the hallmark of a pathogen, such as the portion of the “spike” protein that Sars-CoV-2 uses to penetrate specific cells of the body. In contrast, recovering COVID-19 patients have a combination of different antibodies against parts of the virus in their blood. One speaks of a polyclonal antibody. Each type of antibody is directed against a specific property of the virus, so it can bind to different places.

How are antibodies used as medicine against Covid-19?

The principle is to give the body a head start: By giving the antibody, one skips the stage of the immune response in which the body is busy identifying the distinctive structures of the virus and producing the appropriate antibodies themselves. Regarding the Corona epidemic, there are two known preparations from the United States, namely from Regeneron and Eli Lilly.

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

What are the side effects?

In general, antibody treatments have been well researched because they are also used to treat other diseases such as cancer and rheumatism. In a clinical study There was no increase in severe side effects in the subjects treated with Regeneron compared to the control group. With Eli Lilly he was there According to the U.S. Food and Drug Administration Serious side effects in 2 of the 850 cases examined. The following applies to both formulations: There is a risk of hypersensitivity reactions. In addition, there is not enough data yet to be able to make a final statement on this issue. Some of the side effects may not be known yet.

Antibodies and virus mutations

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

If the virus encounters only one very specific “weapon” such as a type of monoclonal antibody, then mutations that are not recognized by that antibody will prevail. One talks about selection pressure. Mixing different antibodies will reduce the chances of this happening.

Why aren’t antibodies used as standard treatment against Covid-19?

Antibody therapy isn’t always helpful. Due to the mode of its action, such treatment yields the best results, especially at the beginning of the disease. Then it can prevent the development of a dangerous disease. The study data available so far shows that those who received the drug in the first ten days after infection benefited the most from the treatment.

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

Another problem: Antibodies are foreign proteins – and what the body doesn’t know is that it breaks down: so the agent will have limited potency – unlike vaccination, for example – it doesn’t protect against future infections.

A special case of convalescent plasma

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

(Holder 26.02.2021)

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