Pfizer’s Covid-19 oral antiviral drug cut the risk of hospitalisation or death by 89 per cent in a late-stage trial, creating a potential new tool in treating patients and combating the pandemic.

The US pharmaceutical company said on Friday that it was stopping the trial due to the “overwhelming efficacy” and will add the data for the drug known as Paxlovid to its rolling submission to the US Food and Drug Administration for an emergency use authorisation as soon as possible.

The results of the study suggest the drug is even more effective than the antiviral developed by Merck, the company known as MSD outside the US, which cut the risk of hospitalisation or death in half, although the trial results may not be directly comparable. Merck’s drug received its first approval, in the UK, on Thursday.

Pfizer’s chief executive Albert Bourla said the results were “a real game-changer in the global efforts to halt the devastation of this pandemic”.

“These data suggest that our oral antiviral candidate, if approved or authorised by regulatory authorities, has the potential to save patients’ lives, reduce the severity of Covid-19 infections, and eliminate up to nine out of ten hospitalisations,” he said.

The US drugmaker is rapidly gaining market share with its Covid vaccine, developed with Germany’s BioNTech, which it said earlier this week was due to generate $36bn in sales this year.

The company is already signing government contracts for the antiviral, agreeing to sell 500,000 doses to Australia, 250,000 to the UK and 70,000 to South Korea. Pfizer has said it will offer cheaper prices to developing countries.

The trial focused on high-risk patients who were not yet hospitalised, with the interim analysis based on the 1,219 patients enrolled by late September in sites across the world.

The data showed only 0.8 per cent of trial participants who took the antiviral drug within three days of getting symptoms were hospitalised, compared with 7 per cent who received a placebo. The results were similar to those treated within five days. None of the patients taking the drug died, compared with 1.6 per cent who received a placebo.

As an oral drug, the antiviral could be prescribed as an at-home treatment to cut the severity of the disease and reduce the impact of the pandemic on healthcare systems. The drug is far more simple to administer than antibody treatments or Gilead Sciences’ antiviral remdesivir, which is an infusion.

The antiviral is designed to block an enzyme that the virus needs to replicate. It is given with a medication usually used to treat HIV to ensure it remains active in the body for a longer period of time.

Pfizer is also conducting studies to see how effective the drug is in standard risk populations and for people who have had household contacts with infected patients. The company added that it has shown “potent” activity against circulating variants of concern and even other known coronaviruses.