The latest scientific knowledge about Covid-19 symptoms and the global search for treatments

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Remdesivir

This broad-spectrum antiviral was originally developed by Gilead Sciences to combat Ebola, but it showed no effect during a trial in the Democratic Republic of Congo last year.

However in 2017, researchers in the US showed remdesivir inhibited the coronaviruses that cause Sars and Mers in test tube and animal studies and it has been tipped as one of the most promising options in the current crisis. The Solidarity and Discovery trials will both test its efficacy. 

The drug works by disrupting the virus’ ability to replicate and it attacks a key viral enzyme, not the human cell, so has a targeted effect. 

“Remdesivir really does inhibit the virus’ replication – so the ability of the virus to grow in the cell,” said Dr Cammack. “The big challenge with remdesivir is it’s intravenous, so you’ve got to be in hospital – you can’t be handing this out over the counter in Boots.”

Experts hope that within the next month it will become apparent whether or not the drug works.

Chloroquine and hydroxychloroquine

These malaria treatments were originally tested during the Second World War and, unlike remdesivir, would be used for patients in the very early stages of a coronavirus infection. 

“Viruses come in through the nose and travel through the upper respiratory tract first,” said Dr Cammack. “It’s thought that these drugs, in the early stages, stop the virus from entering the cell in the first place.” 

The treatment was used to treat patients during the Sars outbreak in 2002 to 2003. It is also cheap and easy to manufacture so could be widely distributed, even in weaker health systems. 

The US Food and Drug Administration approved the use of the antimalarial drugs for emergency use to treat Covid-19 last weekend. Small studies in France and China reported that patients who did not have severe symptoms recovered more quickly when given hydroxychloroquine. 

The drugs are included in all three large-scale trials. Wellcome are also working with the Bill and Melinda Gates Foundation to identify whether it could be given to healthy people at risk of exposure, for instance health workers or contacts of confirmed cases, to offer some protection ahead of picking up an infection – a bit like a vaccine. 

Dr Cammack said it would be roughly six months before we see conclusive results.

Ritonavir and lopinavir

This is a combination drug used to treat HIV patients. It works by inhibiting the enzymes required for the virus to replicate, and experts hope it might have a similar effect on SARS-CoV-2. 

“The best place for this is when someone is already sick, either at home or in the hospital,” said Dr Cammack. “There are some side effects, for instance diarrhea, so you wouldn’t want to give it to otherwise healthy people as a preventative drug.” 

Early in the outbreak, doctors in Thailand reported success in treating patients using a combination of HIV drugs alongside oseltamivir, a drug sold under the brand name Tamiflu to treat influenza. 

But a study in China of 199 patients found that “no benefit was observed with lopinavir–ritonavir treatment beyond standard care.”

However the drug is still included in the Solidary, Discovery and Recovery trials – Dr Cammack said previous studies were too small to provide definitive results. 

Anti-inflammatories

In the late stages of a coronavirus infection patients can experience massive inflammation, known as a cytokine storm, as their body goes into overdrive in an attempt to fight the infection. This is often deadly. 

Included in the large studies are therapies, including dexamethasone and interferon-beta, which may help reduce inflammation in severely ill patients and could be used in combination with other drugs to treat the coronavirus. 

“This needs to be done very carefully in controlled conditions,” said Dr Cammack. “There’s always a risk that you could target the wrong part of the inflammation and make the situation worse.” 

Monoclonal antibodies are also being trialed to try and stop the body’s immune system going into overdrive. 

These are synthetic antibodies that produced in the laboratory which mimic the body’s immune response and are used to treat auto-immune disorders and certain types of cancer. One such treatment being trialled on coronavirus patients is tocilizumab, used for rheumatoid arthritis, which works by dampening the immune response.

Convalescent plasma therapy

Public Health England and the US authorities have given approval for this therapy which involves giving patients a transfusion containing the plasma of people who have recovered from Covid-19. 

The theory is that plasma from patients who have recovered contains antibodies to the disease that may be effective against the infection. 

Convalescent plasma has been used to treat both Mers and Sars and was also used as far back as the 1918-1920 Spanish flu pandemic.

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