TORONTO -- Pfizer has submitted clinical data to Health Canada regarding an oral medication it is hoping can be used to treat mild to moderate cases of COVID-19 in adults.

Its antiviral pill is called PAXLOVID, and is intended to be given to adults aged 18 and over who have a confirmed case of COVID-19 and are at an increased risk of developing severe illness.

The drug maker said in a press release that the pill is designed to block the activity of an enzyme in SARS-CoV-2 that is essential for the virus to replicate itself, and also help to slow the breakdown of the pill’s ingredients in order to help combat the virus for longer. Part of the pill uses ritonavir, an existing drug that has been used in combination with other antiviral medications before.

This comes two months after Health Canada began reviewing an experimental pill from drugmaker Merck, called molnupiravir, as a potential treatment for COVID-19.

Merck’s pill is still under review in Canada, but has been approved in the U.K. and the U.S.

The U.S. Food and Drug Administration voted Tuesday to approve Merck’s pill as the first medication that Americans could take at home to treat COVID-19.

Since the beginning of the pandemic, the question of treatments that patients could take at home to help themselves and ease the burden on the health care system has loomed large — but not many candidates have shown promise until now.

The benefit of a pill that could be prescribed and taken as soon as symptoms start is that it could prevent people from progressing to the stage of life-threatening or life-altering disease.

At the start of November, Pfizer released the results of their Phase 2/3 trials for PAXLOVID, stating that they had found the pill to significantly reduce hospitalization and death in COVID-19 patients.

The drug is what is called a “protease inhibitor antiviral therapy”, a type of medication that has largely been used before to treat HIV/AIDS and hepatitis C.

Pfizer said that in a randomized, double-blind study of more than 380 patients, there was an 89 per cent reduction in the risk of being hospitalized or dying of COVID-19 in patients that received Pfizer’s pill within three days of displaying COVID-19 symptoms, compared to the study group that received a placebo.

Three people in the group who received PAXLOVID were hospitalized, with zero deaths in that group, while 27 people in the placebo group were hospitalized, with seven later dying.

Patients that were treated with PAXLOVID within five days of their first sign of symptoms also showed a reduction in hospitalizations and deaths compared to the placebo group, Pfizer said, with six people hospitalized compared to 41 people hospitalized in the placebo group.

There were zero deaths among the group that received Pfizer’s antiviral pill, while 10 people died in the placebo group during the study period.

In Pfizer’s announcement in mid-November that they were applying for emergency use authorization for PAXLOVID, they stated that they had submitted to other regulatory health agencies, including those in Australia, New Zealand and South Korea.

Both Merck and Pfizer have agreed to allow other countries to manufacture their antiviral medications, although Pfizer’s has yet to be approved anywhere.

This move has been lauded as a positive step forward, as it will open doors for poorer countries to manufacture their own versions of these experimental treatments. However, Pfizer’s agreement only covers 95 countries which make up around 53 per cent of the global population, meaning some are still left out.

It’s unclear how long it could be before Health Canada passes judgement on whether or not Pfizer’s pill meets their standards or not.