Explainer

What drugs are working as treatments for Covid-19?

From existing antivirals to new antibody therapies – researchers are working at incredible speed to find the best drugs to treat Covid-19.

A recovered Covid-19 patient donates blood plasma for research into Covid-19 antibodies at the medical researcher of the German Center for Immunity Therapy.
Hospitals around the world are using convalescent plasma to treat COVID-19 patients, but these efforts are necessarily local and small-scale.
Credit: Alexander Hassenstein / Getty Images

So far, only two drugs have proved effective against Covid-19: dexamethasone and tocilizumab. Even though vaccination has started in a growing number of countries, Covid-19 continues to spread, and so the search for safe and effective treatments must continue. Teams of scientists are looking into more than 300 potential treatment options(opens in a new tab), running thousands of studies(opens in a new tab) around the world.

What are the main approaches for Covid-19 treatments?  

We still know too little about the coronavirus that causes Covid-19, including how new variants might affect people differently. So researchers are taking a wide range of approaches to find effective and safe treatments.

The three main approaches are: antivirals, anti-inflammatory drugs and antibody treatments. 

Antivirals 

Antiviral drugs work by preventing a virus from developing inside the human body.  

Every virus is different and attacks cells in specific ways, and the antiviral drugs that fight them off are specific too. Very rarely does an antiviral built for one virus also work for different ones. But it can happen: for example, some HIV drugs have also proved effective in fighting off hepatitis B.  

It would be great to have an antiviral specific to Covid-19, but that could take years to discover. In the meantime, researchers are hopeful that some existing antivirals, whether already on the market or experimental, could have some useful effect against the novel coronavirus.

So far none of the existing antivirals under research have proved to work. It's really important to know this, so researchers and clinicians can look at other potential treatments. Examples include:

  • Remdesivir, an antiviral tested as an Ebola treatment. Although it has been authorised for emergency use in some countries, the WHO Solidarity Trial(opens in a new tab) showed that remdesivir does not reduce the risk of dying of Covid-19 or the length of time patients need to stay in hospital. 
  • Hydroxychloroquine, a drug used to treat malaria and rheumatology conditions. After receiving high-profile attention in the media, the large-scale RECOVERY Trial (opens in a new tab)showed that hydroxychloroquine has no benefit for hospitalised patients with Covid-19.
  • Lopinavir-ritonavir, a combination of antivirals used to treat HIV. The RECOVERY Trial showed(opens in a new tab) it had no clinical benefit for Covid-19 patients.

Another drug that has been gaining visibility for its potential to treat Covid-19 is ivermectin – not an antiviral, but an anti-parasitic drug used to treat diseases caused by parasitic worms. The World Health Organization (WHO) recommends that ivermectin should not be used to treat Covid-19 outside of clinical trials, because there isn’t enough evidence about its benefits. 

Graphic showing how antivirals, anti-inflamatories and anibodies could work against the coronavirus.
Credit:

Wellcome

    Anti-inflammatories 

    Anti-inflammatory drugs work by calming the immune system. In people with severe Covid-19, the body’s violent reaction in trying to fight off the virus can cause serious harm and even death. Anti-inflammatories can reduce this response. Researchers have found both positive and negative results. They have looked at:

    • Dexamethasone, a type of steroid used to reduce inflammation in a range of conditions, including sore throats. This was the first drug to be shown to be effective in reducing death rates – by up to one third in hospitalised patients with severe respiratory complications of Covid-19, according to the RECOVERY Trial(opens in a new tab).
    • Tocilizumab, an intravenous drug used to treat rheumatoid arthritis. The RECOVERY Trial showed(opens in a new tab) it reduces the risk of death when given to hospitalised patients with severe Covid-19, and it shortens the time they spend in the hospital. 
    • Interferon beta-1a, used to treat multiple sclerosis by stopping the immune system from damaging the coatings of nerve cells. Interferons have previously been found to show some effects against MERS-CoV and SARS, which are also caused by coronaviruses, but the WHO Solidarity Trial(opens in a new tab) showed that it had little or no effect on Covid-19 patients. 

    Antibody treatments 

    Antibodies attack the virus directly. Unlike antivirals and anti-inflammatory drugs, antibodies are produced naturally by people who have had an infection and recovered. When given to patients who are fighting off an infection, antibodies can boost their immune response and stop the virus from causing further harm.  

    There are two ways that antibodies can be used: 

    • Convalescent plasma can be extracted from the blood of Covid-19 survivors and injected into patients who are fighting the disease. This has been widely used as a treatment for patients with Covid-19 in hospitals around the world, but the RECOVERY Trial(opens in a new tab) found no convincing evidence of its effect. 
    • Monoclonal antibodies are antibodies specific to Covid-19. While they also originate in the blood of people who have recovered, that is only the starting point. Scientists select the relevant antibodies, extract and expand them, and then manufacture them in large quantities. Recent clinical trials have showed that this class of treatments can be used to both prevent and treat Covid-19. Despite this excellent progress, early lab data suggests that the new variants – especially those first identified in South Africa and Brazil – may not respond to the first generation of Covid-19 monoclonal antibodies. While this would be a disappointing setback, this class of treatments still holds great promise for Covid-19 and work is already underway to develop combination and second-generation antibody treatments. However, monoclonal antibodies are traditionally very expensive and not widely available across the world. Covid-19 could be the catalyst to change that, so these treatments become more affordable and accessible to people in rich and poor countries alike.

    How do we find out whether treatments work?  

    Potential new drugs have to go through years of laboratory work, animal testing and human clinical trials before they’re proved to be safe and effective against a specific disease. So developing a new antiviral against the novel coronavirus is not the best hope for containing the ongoing pandemic.  

    This is why researchers have been looking into existing drugs, some experimental and some already licensed, that were developed for other infections, such as Ebola and malaria. These drugs have a head start and we can establish more quickly whether they are useful against Covid-19. 

    Experimental drugs, such as remdesivir, may have already been tested in animals for safety. But they usually have to go through safety trials in humans, to assess what the safe dose is, before moving into clinical trials to assess how effective they are.  

    Existing antivirals have already been proved to be safe for humans, at a specific dose, so what needs to be done now is test whether they work in people with Covid-19. Although there are many small studies investigating the effectiveness of many different antivirals, these can only give indications, not results that are conclusive enough to justify their approval. What we need are large randomised controlled trials, with hundreds or thousands of people enrolled across the world, to tell us whether existing antivirals bring benefits to people with Covid-19.  

    Graphic showing the different stages of research needed to see if different types of treatment work.
    Credit:

    Wellcome

    Existing anti-inflammatory drugs are also already known to be safe if used in certain ways. But because of the way these drugs interact with the immune system, we need more data to understand whether they are safe in the context of a Covid-19 infection. This can be done through small studies first, to assess what the right dose is, before moving into large randomised controlled studies to test their effectiveness. 

    Monoclonal antibodies are a new potential treatment, so they also have to go through safety trials in humans. But because these are natural antibodies originating in human bodies, not synthetic compounds, safety trials will take less time to conduct. After that, effectiveness studies can get going.  

    Large randomised clinical trials – such as the World Health Organization’s Solidarity clinical trial(opens in a new tab) and the UK’s RECOVERY Trial(opens in a new tab) – are essential for getting robust data about which treatments work against Covid-19. These studies are designed to be adaptable ongoing platforms, so they can quickly stop testing drugs that prove not to be working, and add new ones as they develop.  

    How do we make Covid-19 treatments accessible to all?  

    Covid-19 has reached every corner of the world, and it will keep spreading unless it is controlled everywhere. To stop the pandemic, to get societies back to normal, and to get economies moving again, any treatments and vaccines must be made accessible to everyone who needs them, everywhere in the world, regardless of their ability to pay.   

    For that to happen: 

    • governments, industry and philanthropy must pool resources to pay for the risk, the research, manufacturing and distribution to ensure everyone has access to treatments  

    • clinical trials need to take place across the world, to make sure treatments work for everyone 

    • national governments must work together to ensure that coronavirus treatments can be manufactured in as many countries as possible and distributed globally to everyone who needs them. 

    More funding is needed to support urgent research. And global collaboration is paramount for ensuring global access to treatments. To promote this, the ACT-Accelerator(opens in a new tab) was launched. Through this collaboration, the World Health Organization, governments and international health bodies have pledged to make sure that any tools developed to fight the current pandemic – vaccines, diagnostics and treatments – will be distributed equitably to everyone who needs them.  

    This explainer was originally published in May 2020 and updated in April 2021.

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