The United Kingdom on Thursday became the first country in the world to approve an orally ingested COVID-19 antiviral pill, developed by Merck and Ridgeback Biotherapeutics.
On Friday, COVID-19 vaccine maker Pfizer unveiled promising results on their experimental pill, claiming that it could cut rates of hospitalization and death from the virus by nearly 90 per cent.
Public health experts have described the implementation of the anti-viral pills as potentially game-changing in the fight against the pandemic, citing both their effectiveness in preventing severe disease and death as well as their low cost to produce.
Here’s what you need to know about the anti-viral COVID-19 pills.
How does it work?
The antiviral drugs have intrigued health experts and epidemiologists in how they specifically target parts of the virus’ genetic code.
In the case of Merck’s molnupiravir, the drug, once ingested, targets an enzyme used by the coronavirus to reproduce itself.
When the coronavirus’ RNA begins to replicate within a cell, it would mistakenly pick up the drug and incorporate it into the RNA chain.
The drug would then insert errors into the virus’ genetic code — slowing its ability to spread and take over human cells.
“So basically, if the virus is trying to replicate more and more copies of itself, one of the things it needs is to put that intact viral RNA into that new virus particle that’s going to be shed from the cell, and this drug basically really screws that whole process up,” explained Dr. Gerald Evans, chair of Infectious Diseases at Queen’s University.
“It creates like a faulty template to be able to undergo further replication.”
While Merck’s pill acts as a nucleoside analog that tries to introduce errors into the virus’ genetic code, Pfizer’s differs as an inhibitor that looks to block an enzyme the coronavirus needs in order to multiply.
Pfizer said its pill targets the part of the virus essential to viral replication, essentially meaning that it cannot become resistant to the drug itself.
Both antiviral remedies would need to be taken over a period of five days, though the number of pills taken would differ between the brands.
Pfizer’s anti-viral concoction would need to be taken six times a day, with three tablets in the morning and another three at night. Merck’s treatment on the other hand needs eight pills in total, with four in the morning and four in the evening.
How effective are the pills?
In early October, Merck revealed that its pill cut the chances of COVID-19 hospitalization or death by 50 per cent in at-risk patients if its pill was given within five days of the disease’ onset.
The company said then that viral sequencing so far showed that its drug would be effective against all variants of COVID-19 — including the much more deadly Delta.
On Friday, Pfizer said that its pill could reduce the chances of hospitalization or death by nearly 90 per cent should patients be treated within three days of the onset of symptoms, and 85 per cent within five days of onset.
Of the 1,219 patients in Pfizer’s study, 0.8 per cent were hospitalized and none died within 28 days after treatment compared to the seven per cent hospitalization rate and seven deaths in the placebo group who were not administered the drug.
Another two trials including people without underlying risks factors and people who were exposed to the virus but were not yet infected are still underway, the company said.
Are there side effects?
While both Pfizer and Merck’s drugs showed promising results, none were free from potential side effects.
Pfizer’s drug would have to be taken alongside an older antiviral called ritonavir, which works to boost the activity of inhibitors but could potentially cause gastrointestinal side effects and interfere with other medicines.
Similar drugs in the same class as Merck’s have also been linked to birth defects in some animal studies, though the company said that studies of its drug currently don’t show signs of it causing any birth defects or cancer.
Both of the companies expressed confidence in their drug’s safety, despite having released only limited data on the treatments.
According to Pfizer, about 20 per cent of patients having taken the drug or a placebo experienced mostly mild adverse events, and that serious side effects were found in 1.7 per cent of those who took the drug.
In Merck’s case, 12 per cent of patients who took the drug and 11 per cent who took a placebo experienced an adverse event. But the company’s pill targets the genetic code of the virus, leading to some experts questioning whether the drug could cause mutations like birth defects or tumours.
The U.K.’s regulatory agency said however that the pill’s ability to interact with DNA has been studied “extensively” and that it wouldn’t pose a risk to humans.
How could it change the fight against COVID-19?
While the U.K. remains the first and only country to have approved Merck’s antiviral pill, others aren’t too far behind.
U.S. advisers are set to meet later in November to vote on whether the drug should be authorized while Health Canada said it was still reviewing data from the pharmaceutical company before making its decision.
Merck has already etched out deals to sell more than 3 million courses of its drug so far, while the U.S. has already secured “millions of pill doses” of Pfizer’s antiviral pill according to President Joe Biden on Friday.
Dr. Sumon Chakrabarti told The Canadian Press that the “slow burn” of hospitalizations may have added more urgency to the U.K.’s authorization of the drug — a sentiment Evans also echoed.
And while there seems to be an urgency for its approval in other countries struggling from virus hospitalizations like Britain, both experts said that Canada’s health regulator would be sure to look to at it from a more domestic context.
Evans said that the vast majority of the Canadian population has already been vaccinated and protected against COVID-19 — essentially placing the antiviral drugs in a “niche” spot.
The drug wouldn’t specifically protect a person from contracting the virus, but would protect them from severe outcomes should they get it, according to Evans.
“So this would be a drug, which is if you want to think about it, it’s in a kind of niche, and the niche is an unvaccinated person where you don’t have that enormous protective effect of vaccines,” he said.
However, the the medication could potentially push undecided people from getting the vaccine, warned Evans.
“If this drug proves to be useful, it’s going to make people who otherwise should go for the vaccine … say ‘well, no, no we got an antiviral here, so I think I will not bother to get the vaccine,’ and that’s one of the only drawbacks to it right?”
—With files from The Canadian Press, the Associated Press and Reuters