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As countries continue to struggle with rising numbers of Covid-19 cases despite high vaccination rates, new fronts are opening up in the battle to combat the pandemic.
The pharmaceutical giant Pfizer is conducting trials of an anti-viral drug that could be administered to people in the early stages of infection.
Named PF-07321332, the drug is described as the first oral anti-viral targeting the coronavirus to reach late-stage trials.
Here we look at Pfizer’s drug and consider other efforts to combat Covid-19 through prophylactic or preventative drugs.
What do Pfizer’s trials involve?
At the beginning of this month Pfizer announced that it had begun trials of its drug in people infected with Sars-CoV-2 who are not at increased risk of severe illness.
The company previously started a similar trial of the drug in individuals who are at greater risk of serious illness, and results are expected before the end of this year.
Some participants, all of whom have a coronavirus infection, will take the drug (plus a second drug aimed at increasing its effectiveness) every 12 hours for five days, while others will receive a placebo.
PF-07321332 is a protease inhibitor, meaning that it inhibits the action of enzymes – substances that speed up biochemical reactions – called proteases.
Proteases break the bonds between long strings of protein sub-units and are used by the coronavirus to make the proteins it needs to replicate within human cells. Without them, the virus cannot multiply.
As reported recently in The National, in a separate project, researchers at NYU Abu Dhabi are trying to identify protease inhibitors that could combat Covid-19.
Why could these drugs be significant?
Vaccines offer protection, but they are not completely effective at preventing serious disease or stopping the spread of the virus, especially when it comes to emerging variants.
Drug treatments for people seriously ill and in hospital have significantly improved since the pandemic started, with steroids, for example, helping to improve survival rates.
However, Pfizer’s protease inhibitor may prevent people from reaching the stage where they have to go into hospital in the first place.
“If we can find a small molecule for [use as an] early-stage antiviral, that’s the way out of the pandemic, obviously complementing in this case vaccines,” said David Taylor, professor emeritus of pharmaceutical and public health policy at University College London.
“We’ve got some late-stage treatments. It’s the early-stage this drug [targets] … they can stop the disease becoming late stage and so really dangerous.”
Prof Taylor said such early-stage drugs, if shown to be effective, could be used in areas that are experiencing significant outbreaks of Covid-19.
What other treatments are emerging?
While Pfizer trials its protease inhibitor, the American pharmaceutical giant Merck and an American company, Ridgeback Biotherapeutics, this month also announced advanced trials of a drug to combat Covid-19 early on.
The companies will be looking at whether their drug, molnupiravir, can stop the spread of the disease within households.
Molnupiravir works in a different way to the Pfizer drug, but the aim is the same – to stop the coronavirus from replicating and so prevent Covid-19.
In June results from earlier trials were announced and these indicated that the drug helped people to clear the virus from their system.
Participants in the latest trials, which will span several countries, must be living in the same household as someone with the disease.
They will take molnupiravir or a placebo orally every 12 hours for five days, and will be monitored for two weeks to see if they fall ill with Covid-19 or remain well.