Coronavirus cure: When will we have a drug to treat it?
More than 350,000 people have died with Covid-19, but there are still no drugs proven to help doctors treat the disease.
So how far are we from these life-saving medicines?
What work is being done to find treatments?
More than 150 different drugs are being researched around the world. Most are existing drugs that are being trialled against the virus.
- The World Health Organization (WHO) has launched the Solidarity trial aimed at assessing the most promising treatments
- The UK says its Recovery trial is the the world's biggest, with more than 5,000 patients already taking part
- And multiple research centres around the world are attempting to use survivors' blood as a treatment
What types of drugs might work?
There are three broad approaches being investigated:
- Antiviral drugs that directly affect the coronavirus's ability to thrive inside the body
- Drugs that can calm the immune system - patients become seriously ill when their immune system overreacts and starts causing collateral damage to the body
- Antibodies, either from survivors' blood or made in a lab, that can attack the virus
What is the most promising coronavirus drug?
The latest clinical trials of remdesivir, an antiviral drug originally developed to treat Ebola, have been encouraging.
The US National Institute of Allergy and Infectious Diseases (NIAID) found that remdesivir cut the duration of symptoms from 15 days down to 11. The trials involved 1,063 people at hospitals around the world. Some were given the drug and others were given a placebo (dummy) treatment.
Dr Anthony Fauci, who runs NIAID, said: "We now have solid data showing that remdesivir diminishes to a modest degree the time to recovery for people hospitalised with COVID-19."
However, although remdesivir may aid recovery - and possibly stop people having to be treated in intensive care - the trials did not give any clear indication whether it can prevent deaths from coronavirus.
It is thought that antivirals may be more effective in the early stages, and immune drugs later in the disease.
The UK government has made the drug available on the NHS, with Health Secretary Matt Hancock saying it was the biggest step forward in terms of treatment since the pandemic began.
UK regulators say there is enough evidence to approve its use.
It is one of the four drugs in the WHO Solidarity trial and its manufacturer, Gilead, is also organising trials.
The US data on remdesivir was published at the same time as a trial of the same drug in China, reported in the Lancet medical journal, showed it was ineffective.
However, that trial was incomplete because the success of lockdown in Wuhan meant doctors ran out of patients.
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Can HIV drugs treat coronavirus?
There has been much talk, but little evidence, that a pair of HIV drugs - lopinavir and ritonavir - would be effective at treating coronavirus.
There has been some evidence they can work in the laboratory, but studies in people have been disappointing.
The combination did not improve recovery, reduce deaths or lower levels of the virus in patients with serious Covid-19.
However, as the trial was conducted with extremely sick patients (nearly a quarter died) it may have been too late in the infection for the drugs to work.
Can malaria drugs stop coronavirus?
Malaria drugs are part of both the Solidarity and Recovery trials.
Chloroquine, and a related derivative, hydroxychloroquine, may have antiviral and immune-calming properties.
The drugs have been thrust into the spotlight as potential coronavirus therapies, largely because of claims made by President Trump, but there is still scant evidence on their effectiveness.
Hydroxychloroquine is also used as a treatment for rheumatoid arthritis, because it can help regulate the immune system.
Early laboratory tests have shown it can inhibit the coronavirus, but there are growing concerns about its use against the disease.
The WHO recently suspended its global trials of hydroxychloroquine following a large-scale study in the Lancet. That found the drug's use can cause heart problems, and actually increased the likelihood of death.
The WHO says there is no definitive evidence of its effectiveness.
What about immune drugs?
If the immune system overreacts to the virus then it can cause inflammation throughout the body. This is helpful for rallying the immune system to fight the infection, but too much can cause collateral damage to the body and can be fatal.
The Solidarity trial is investigating interferon beta, which is used to treat multiple sclerosis, and lowers inflammation. Interferons are a group of chemicals released by the body when under attack by a virus.
The UK's Recovery trial is investigating dexamethasone - a type of steroid used to reduce inflammation.
Can survivors' blood treat coronavirus?
People who survive an infection should have antibodies in their blood that can attack the virus.
The idea is you take the blood plasma (the part which contains the antibodies) and give that to a sick patient as a therapy.
The US has already treated 500 patients with what's known as "convalescent plasma", and other countries are getting involved too.
How long until we have a cure?
It is too soon to know when we might have a drug that can treat the coronavirus.
However, we should start to get the results of trials in the next few months. This is much earlier than we will know if a vaccine (which protects against infection rather than treat it) is effective.
This is because doctors are testing drugs that have already been developed and are known to be safe enough to use, whereas vaccines researchers are starting from scratch.
Some completely new, experimental, coronavirus drugs are also being tested in the laboratory but are not yet ready for human tests .
Why do we need a treatment?
The most obvious reason for wanting a treatment is it will save lives, but it could also allow some lockdown measures to be lifted.
Having an effective treatment would, in essence, make coronavirus a milder disease.
If it stopped people who were admitted to hospital from needing ventilation, then there would be less risk of intensive care units being overwhelmed, so controls on people's lives may not need to be as strict.
So how are doctors treating patients now?
If you are infected by coronavirus, then for most people it would be mild and can be treated at home with bed-rest, paracetamol and plenty of fluids.
But some people need more intensive hospital treatment, which involves oxygen support such as ventilation.
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