The antiviral pill that reduces the risk of dying from Covid by 30 per cent will work against future variants and may also be able to treat flu, according to the drug’s creators.

Dr Dilruwan Chaminda Herath is the UK medical director at Merck Sharp & Dohme (MSD), the company behind molnupiravir, and is a trained infectious diseases physician who worked on HIV for several years before joining MSD in November 2019.

In an exclusive interview with The Telegraph, he said: “We have the laboratory data that suggests molnupiravir is effective against the variants, including omicron… and we envisage that it would remain active against all variants.

“Variants are essentially changing one area on the structure of the virus, on the spike protein.

“Therefore, because molnupiravir doesn’t target the spike protein, what we see in the lab is that the effectiveness doesn’t seem to decrease with different variants so they’re all comparable. We are optimistic that it will continue to work against variants going forward.”

Britain became the first country in the world to authorise the use of the drug to treat Covid on November 4, with Health Secretary Sajid Javid calling it a “game changer”.

Viral Trojan horse

Molnupiravir, also known as Lagevrio, was first developed to fight the Venezuelan equine encephalitis virus (VEEV), and scientists discovered it is the viral equivalent of the Trojan horse.

The drug mimics two of the building blocks that make up viral RNA so when the virus is in the process of replicating it tries to use the drug to make new genetic code.

But while they are similar enough to be incorporated into the virus, they are sufficiently different to derail the entire process, weaving gibberish into the virus’s genes.

This process, called lethal mutagenesis, is an insurmountable obstacle for the virus which curtails its spread.

Similar drugs have been found before, but molnupiravir is unique in that its ‘wolf in sheep’s clothing’ act is effective against a wide range of viruses.

And while MSD is currently focused on using molnupiravir to fight Covid, Dr Herath acknowledged its potential as a multi-virus weapon.

“Looking ahead to the future, we have laboratory data that suggests molnupiravir is effective against a multitude of RNA viruses, including influenza, and we are looking at how we approach those development programmes,” Dr Herath said.

“It’s an interesting drug from that perspective because in the laboratory it doesn’t seem to be particularly wedded to one particular virus that it acts against.”

But despite molnupiravir reducing a sick and vulnerable person’s chance of death by almost a third, Dr Herath believes its biggest benefit may be not as a treatment, but as a way to suppress transmission.

“Molnupiravir has a second utility, which is about onward transmission, which is probably more important,” Dr Herath said.

Data on this is currently being gathered and should be published later this year.

Concerns over data

He added: “Whilst it’s obviously very important to prevent individuals progressing, the population impact of an antiviral is really important. Even with the current rollout plans there should be some beneficial effects on onward transmission.”

On December 22, the UK Government ordered 1.75 million courses of molnupiravir from MSD, taking Britain’s stockpile to more than 2.2 million.

But there have been some concerns about the drug from a pocket of scientists, primarily surrounding the data proving its effectiveness and its safety profile.

In October, MSD published preliminary data indicating the drug, given as two 800mg tablets a day for five days, halved a person’s risk of death. Seven per cent of the 385 people who were given the drug were hospitalised or died, but in the placebo group, this figure was 14 per cent.

This 50 per cent reduction in hospitalisation and death from Covid made global headlines, and molnupiravir was approved by the MHRA for use in people with mild to moderate Covid-19 and at least one risk factor for developing severe illness, such as obesity, diabetes or being over 60.

But on November 26, MSD, which is known as Merck in the US, published the full results which showed that molnupiravir was just as effective as the interim data had shown, with just seven per cent of patients on the drug becoming severely ill.

However, in the placebo arm, just one in ten people in the study were hospitalised or died, compared to 14 per cent in the interim analysis. As a result, the relative reduction in death and hospitalisation from molnupiravir was 30 per cent, not 50.

The MHRA reviewed the new figures, and stuck with its original decision.

The cause of the reduction in relative effectiveness is under review, Dr Herath said, and may be due to discrepancies in how some countries involved in the trial reported their findings.

Risk of mutations ‘very low’

As for molnupiravir’s safety, concerns had been raised that due to how it works it may cause mutations in humans, much like it does in the virus’s RNA.

“What we see in our studies in the laboratory is that we don’t see the same effect in humans,” Dr Herath said.

“It’s very particular to virus RNA, but not human RNA. So realistically, from our data set, the risk to humans of mutations is very, very low.”