As Covid vaccines are rolled out across the world, a number of drugs are being tested as treatments for people who already have the disease.
Many of these are existing drugs that are being trialled against the virus.
What work is being done to find treatments?
- The UK is running the the world's largest clinical trial, called Recovery, involving more than 12,000 patients. It is one of the few trials to have given a definitive view on which drugs do and do not work
- The World Health Organization (WHO) is running the the Solidarity trial to assess promising treatments in countries around the world
- The University of Oxford's Principle trial is looking for medicines which could help people recover from Covid symptoms at home
- Multiple pharmaceutical companies are also running trials of their own drugs
There are three broad approaches being investigated:
- Antiviral drugs that directly affect the coronavirus's ability to thrive inside the body
- Drugs that calm the immune system (severe Covid-19 is caused by patients' immune systems overreacting and damaging the body)
- Antibodies that can target the virus, taken from either survivors' blood plasma or made in a lab
It is possible that different drugs will work better at different stages - such as antivirals at the beginning and immune drugs in late-stage diseases. Combinations of therapies will also be investigated.
The steroid dexamethasone has been shown to cut the risk of death by a third for patients on ventilators and by a fifth for those on oxygen.
Further data suggests another steroid, hydrocortisone, is equally effective too.
Both calm down inflammation (part of the immune response) in the body, which can become damaging in severe cases.
Crucially, dexamethasone is also cheap which means it could be used all around the world.
However, the drug does not work on people with milder symptoms.
A steroid drug commonly used to treat asthma called budesonide has been shown to help vulnerable people with early Covid symptoms recover more quickly at home.
After encouraging early trial results, the NHS says it can now by prescribed by GPs as an inhaler.
The company Regeneron has developed a potent intravenous infusion of two types of antibody cloned in the lab which is designed to bind to the Covid virus and stop it infecting cells and replicating.
The monoclonal antibody treatment is designed for patients who have failed to make their own natural antibodies to fight the virus, and who often experience the most severe symptoms.
After a trial of nearly 10,000 patients, the researchers calculated that it could help one in three severe Covid sufferers, and potentially save the lives of six out of every 100 people who qualify to receive it.
The treatment is given alongside dexamethasone.
Tocilizumab and sarilumab
Researchers have reported encouraging results from two anti-inflammatory medications, tocilizumab and sarilumab.
In a trial carried out in six different countries, including the UK, with about 800 intensive care patients, the drugs reduced the number of deaths from 36% to 27%.
The UK's Recovery study also found tocilizumab added to the life-saving effects of dexamethasone.
Tocilizumab and sarilumab dampen down inflammation, which can go into overdrive in Covid patients, damaging the lungs and other organs.
Doctors could give them to a Covid patient who, despite receiving dexamethasone, is still deteriorating and needs intensive care.
The research findings have not yet been peer-reviewed or published in a medical journal.
Interferon beta, a protein which the body produces when it gets a viral infection, is at the centre of a large trial in the UK.
It's being given to hospitalised Covid patients in the form of a spray which is inhaled. It's hoped this will stimulate the immune system, priming cells to be ready to fight off viruses.
Early findings suggest the drug, which is normally used for treating multiple sclerosis, could cut the odds of a Covid patient in hospital developing severe disease - such as requiring ventilation - by almost 80%.
What other drugs have been trialled?
Remdesivir is an antiviral drug - originally developed to treat Ebola - that showed promising early results.
However, in October 2020, the World Health Organization advised that it "appeared to have little or no effect on hospitalised Covid," in terms of death rates, length of stay in hospital, or seriousness of illness.
Another drug being assessed by the Principle trial is Ivermectin, which is commonly used to treat a wide range of parasitic diseases such river blindness.
It has controversially been promoted for use across Latin America and in South Africa, despite little hard evidence so far that it works.
What do I need to know about the coronavirus?
Can malaria drugs stop coronavirus?
Chloroquine, and the related drug, hydroxychloroquine, may have antiviral and immune-calming properties.
The drugs were thrust into the spotlight as potential coronavirus therapies, largely because of claims made by President Trump, and because early laboratory tests showed they could inhibit the coronavirus.
However, the UK's Recovery trial found that hydroxychloroquine does not work as a treatment for Covid-19 and the WHO has stopped trialling the drug.
Can survivors' blood treat coronavirus?
People who survive an infection should have antibodies in their blood that can attack the virus.
Blood plasma (the part which contains the antibodies) can be extracted from those who have recovered and then given to sick patients as "convalescent plasma".
It was hoped transfusing seriously-ill patients with the plasma could give struggling immune systems a helping hand.
But a trial in hospital patients found using blood plasma does not reduce deaths or improve outcomes for those in intensive care.
However, international trials are continuing to examine if plasma might help much earlier in the disease, before people get to hospital. Blood plasma is still being collected in the UK.
The US Food and Drug Administration (FDA) has given emergency authorisation for the use of plasma to treat coronavirus patients based on promising results from early trials - although some experts say it's too soon to know how effective the treatment is.
Why do we need treatments as well as vaccines?
While vaccines can stop people from contracting Covid and becoming seriously ill, treatments will still be needed for those who already have it.
Having an effective treatment would, in essence, make coronavirus a milder disease.
If it stopped people from needing hospital treatment or stopped those admitted to hospital from needing ventilation, then there would be less risk of hospitals and intensive care units being overwhelmed.
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