THE UK APPROVES A PILL TO TREAT COVID-19, BUT HOW DOES IT WORK?
▶ Molnupiravir, which prevents severe illness in the vulnerable if taken at the onset of infection, is in the vanguard of oral treatment, writes Daniel Bardsley
Efforts to combat the coronavirus took another step forward with the UK’s announcement that it has approved the first pill to treat patients with Covid-19. Molnupiravir is an antiviral drug that can be taken twice a day for five days at the onset of infection by people who are vulnerable to developing severe disease, perhaps because of age or underlying health conditions.
Authorisation for the drug, which is produced by Merck, the US pharmaceutical company, and Ridgeback Biotherapeutics, was granted by the UK’s Medicines and Healthcare products Regulatory Agency this month.
Here, The National explains molnupiravir’s significance in the context of other treatments.
Q How effective is molnupiravir?
A
Trials found that molnupiravir cut the risk of illness requiring hospital admission by half, and the hope was that by preventing more people from becoming seriously ill, the drug will ease pressure on hard-pressed health systems.
It may also reduce transmission of the coronavirus, researchers said.
“There are not so many [drugs] that have been approved as direct antivirals – that’s the significance of this,” said Ian Jones, professor of virology at the University of Reading in England.
“The clinical trial data seemed to show a clear usefulness. But there’s one big caveat – it must be given early in the infection. It’s not going to do much good if you’re already in hospital.”
This means that the people who are likely to be taking molnupiravir are those with “mild to moderate” symptoms and who are vulnerable to Covid-19 because of their age or underlying health conditions.
Trials in India involving people with more severe illness indicated that the drug was ineffective at that stage, emphasising the need to take it early.
“We can use it early and stop [the virus] doing harm [before] the disease becomes fully developed,” said David Taylor, professor emeritus of pharmaceutical and public health policy at University College London.
“There’s every reason to suppose it has an important [contribution] alongside vaccination and the late-stage drug treatments we already have.”
How does it work?
Molnupiravir disrupts the replication of the virus’s genetic material (ribonucleic acid or RNA) and in doing so, it can stop the pathogen multiplying.
It incorporates itself into the strands of RNA the virus is producing, creating mutations that eventually cause the number of virus particles in an infected person to fall. It has been described as a means of causing the virus to mutate itself to death.
“This is a drug which attacks the replication of the virus, the ability of the virus to make more of itself,” Prof Jones said.
Its mode of action has raised concerns, however, that the drug may cause mutations in human genetic material, potentially leading to tumours.
Merck said that trial data showed that the drug was safe.
Molnupiravir was originally tested as a treatment for a disease in horses before interest turned to its potential effects against influenza in people.
After the coronavirus emerged, Ridgeback Therapeutics secured a licence for the drug, leading to its approval for use against the virus.
How does it compare with other treatments?
Other drug treatments are given intravenously or by injection, making them difficult to administer unless a person is in hospital, which is a drawback for drugs that should be taken early on in infection.
Molnupiravir stands out for being taken as a pill.
Other drug companies are working on their own pill treatments for the condition.
Among the treatments already available is one from Regeneron Pharmaceuticals and Roche that is made up of two monoclonal antibodies (identical antibodies produced artificially in large numbers).
Given early on, this treatment can prevent the coronavirus from attaching itself to cells in the respiratory system.
Some other monoclonal antibodies have similar effects, among them sotrovimab, which is used in the UAE.
The US Food and Drug Administration gave emergency approval for sotrovimab in May, saying the drug was suitable for people at risk of serious illness, such as those aged 65 and above or with certain medical conditions.
Further monoclonal antibodies work in a different way and are given later on during serious infections to stop the cytokine storm in which the immune system overreacts to coronavirus infection, releasing excessive amounts of chemicals called cytokines.
This can result in organ failure and death.
A corticosteroid called dexamethasone is another later-stage treatment given to seriously ill patients to curtail the cytokine storm.
The newly approved pill is not cheap, but Merck has licensed companies in India to produce generic versions
Where will molnupiravir be used?
As well as the UK, which has ordered 480,000 doses, several nations, including Australia, Singapore, South Korea and the US, have struck advance purchase agreements for molnupiravir.
One place where the drug may prove particularly useful is in care homes, as it could be given to residents in the event of an outbreak of the coronavirus.
The US is paying about $1.2 billion for 1.7 million five-day courses of treatment, which works out at about $700 a patient.
At this price, the drug is likely to be too expensive for many lower-income nations.
But Merck has licensed several Indian manufacturers to produce generic versions of the drug.
This is likely to lead to the treatment being available for a far lower price than many developed nations are paying for it.
Reports indicate these cheaper generic versions could be distributed in about 100 low and middle-income countries.