The therapies – called monoclonal antibodies – are the first treatments to be specifically designed for the coronavirus and can be given to patients at an early stage of the disease.
Two US pharma firms, Eli Lilly and Regeneron, both launched the first safety studies of monoclonal antibodies therapies in humans earlier this month.
Eli Lilly is expected to get the first results by the end of this month and, if successful, the company will launch trials to test their efficacy with results known as soon as autumn.
Eli Lilly and Regeneron’s therapies are based on antibodies of patients who have recovered from Covid-19 but one San Francisco-based biotech, Vir Biotechnology, is looking at antibodies isolated from the blood of people who recovered from Sars, which swept around the world in 2003 to 2004 and is a close cousin of Covid-19.
One of the original Sars antibodies used in a “cocktail” with antibodies from recovered Covid-19 patients neutralised the Covid-19 virus in the laboratory, researchers reported in the journal Nature. These antibodies are not yet being tested on humans.
Unlike drugs such as the steroid dexamethasone – which UK scientists found reduced death rates in patients on ventilators by a third earlier this month – monoclonal antibodies have been specifically designed to attack the virus and can be given to patients much earlier in the course of the disease.
Dr Nick Cammack, who is leading the global search for coronavirus therapeutics at UK biomedical research charity Wellcome, said there was a lot of excitement at the prospect of monoclonal antibodies.
“These are the first absolutely specific treatments for Covid-19. We’re excited about them and we think they will work but there’s no data yet,” he said.
To make the treatment antibodies are taken from patients who have recovered from the disease and then grown into cells in the laboratory. They work by sticking to the virus and stopping it entering into the lungs.
Dr Cammack said they “fast forward” the body’s immune response to the disease and prevent it from going into the immune system overdrive that can kill patients.
Antibodies only have to be harvested from a recovered patient once as the cells can be grown an infinite number of times, in a process Dr Cammack compared to a sourdough bread starter.
The treatment is administered as an injection under the skin and may be used as both a prophylactic and a therapy, said Dr Cammack.
“One of the big benefits of antibodies is that they will last at least two weeks. You can imagine that if there’s an outbreak in your hometown you could go to the health centre and get an injection, like you would with a flu shot. In the absence of a vaccine the therapy would be of great benefit,” said Dr Cammack.
But he said the treatment would be expensive.
"The challenge with antibodies is that they are not cheap like dexamethasone. One of the things we are doing is to ensure that when they are produced for low and middle income countries they are at affordable price. There's no point having a great drug that people cannot afford," he said.
Dr Cammack is therapeutics lead for the Access to Covid-19 Tools Accelerator, a global partnership led by the World Health Organization to develop diagnostics, treatments and vaccines for low and middle income countries.
The partnership aims to have two billion doses of vaccine by the end of 2021, half of which will go to the poorest countries. It also hopes to send send 500 million diagnostic tests and 245 million courses of treatment to lower and middle income countries by the same time.
To achieve these plans WHO said it needed $31.3bn, of which just $3.4bn has been pledged. The organisation acknowledged the cost was high but “it pales in significance when compared to the cost of Covid-19".
Dr Cammack said that treatments alone would not defeat the virus.
“We need treatments, vaccines and diagnostics to really fight the disease,” he said.
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