A drug given to dogs to treat their cancer could be used to thwart Covid, scientists say.
Masitinib has been used on canines for over a decade — but is not yet approved for humans.
Academics already believe it may have potential in treating skin cancer, Alzheimer’s, asthma and multiple sclerosis.
But now University of Chicago researchers hope it could also offer hope in the fight against the coronavirus pandemic.
Laboratory trials of masitinib — which costs just £2 a pill — found it stopped the virus replicating, which is how it ends up causing disease.
Studies showed it worked just as well against variants, and other similar viruses that can make humans ill.
The trial is not yet at the stage of giving the drug to Covid patients, but the smallest dose of the drug that is given to dogs costs just £2
Drugs proven to work in the fight against Covid
Budesonide is a drug most commonly taken through an inhaler to treat asthma or chronic obstructive pulmonary disease.
A study by the University of Oxford found in April that in two weeks, 32 per cent of people recovered from Covid when taking the drug through an inhaler, compared to 22 per cent without it.
Budesonide is a corticosteroid, which means it reduces swelling inside the body and helps control immune reactions.
In the lungs, swelling can make it difficult to breathe and cause coughing. Budesonide can open up the airways to relieve these symptoms.
It costs around £15 for one inhaler and is available on the NHS.
Dexamethasone was the first medicine identified as reducing the death rate among patients hospitalised with Covid.
A trial by the RECOVERY group found that the cheap steroid dexamethasone can prevent death in one in eight ventilated coronavirus patients and one in 25 on breathing support.
The steroid prevents substances in the body from being released that cause inflammation, which makes breathing difficult in Covid patients.
The drug is usually used to treat ulcerative colitis, arthritis and some types of cancer.
It is given as either an injection or a daily tablet and costs £5 per patient, and is available on the NHS.
A RECOVERY trial found that arthritis drug tocilizumab cut the risk of death by an extra four per cent, on top of the 20 to 35 per cent reduction given by dexamethasone.
A study by the University of Oxford and the NHS found that arthritis drug tocilizumab cuts the risk of dying from Covid by up to half when taken with dexamethasone.
This means one extra life could be saved for every 25 people given the drug.
It was also found to cut the time spent in hospital by five days.
The anti inflammatory drug is usually used to treat rheumatoid arthritis and similar conditions.
In Covid patients, it prevents a reaction in the lungs and airways that leads to respiratory issues.
It is given to patients through an injection into the veins and lasts four weeks at a time.
A typical 480mg dose costs £614.40, and it is available on the NHS.
But the trials were not carried out on humans, with the claims based solely on tests of the drug on mice and cell cultures.
The team are now planning human trials, in the hope it will be proven to work — and they are confident it will.
Professor Savas Tay, who led the research, said: ‘Inhibitors of the main protease of SARS-CoV-2, like masitinib, could be a new potential way to treat Covid patients, especially in early stages of the disease
‘Covid will likely be with us for many years, and novel coronaviruses will continue to arise.
‘Finding existing drugs that have antiviral properties can be an essential part of treating these diseases.’
Dr Nir Drayman, who co-wrote the paper, said: ‘Masitinib has the potential to be an effective antiviral now, especially when someone is first infected and the antiviral properties of the drug will have the biggest effect.
‘This isn’t the first novel coronavirus outbreak, and it’s not going to be the last. In addition to vaccines, we need to have new treatments available to help those who have been infected.’
Clinical trials for other illnesses have shown drug, branded as Masivet and made by French firm AB Sciences, is safe in humans.
But it can cause side effects like diarrhoea, vomiting, swollen ankles, feet and legs, and increase the risk of heart disease.
The smallest dose of the drug that is given to dogs costs around £2. It is not clear how much humans would need, if it was proven to work.
Experts at the University of Chicago searched through a list of nearly 2,000 drugs known to be safe in humans.
All of the drugs they investigated can stop cells becoming infected with a separate coronavirus called OC43, which causes a common cold.
They trialled the drugs against SARS-CoV-2 to determine it it could work against the virus behind the pandemic.
Masitinib was found to be the most potent, according to results of the study published yesterday in the journal Science.
Further tests found it reduced the viral load — the amount of virus that an infected individual has — in mice by 99 per cent.
Experts said the drug worked equally well on the Kent ‘Alpha’, South African ‘Beta’ and Brazil ‘Gamma’ variants.
Researchers said it could also be effective against different types of coronaviruses and picornaviruses, including Hepatitis A, polio, and viruses that cause the common cold.
It works by binding to an enzyme found in coronaviruses called 3CL and stopping it from working. The enzyme lets them replicate inside cells.
Since the beginning of the Covid pandemic, scientists have been scrambling to find effective treatments.
So far, the steroid dexamethasone and arthritis drug tocilizumab have been proven to work.
Dexamethasone is available on prescription from the NHS, and costs £6 for 28 500g tablets. Tocilizumab can also be prescribed on the NHS in certain cases, and costs £913 per 1ml injection.