What's happening with antiviral drugs to treat COVID-19?

Pfizer Canada has submitted its experimental antiviral medication to treat early COVID-19 to Health Canada. 

The submission, received on Dec. 1,  is now "under review," according to Health Canada's COVID-19 drug and vaccine applications database.  

The move comes almost a month after Pfizer announced that its antiviral drug looked so promising that independent experts recommended stopping clinical trials.

Another antiviral pill for the treatment of COVID-19, manufactured by Merck, was submitted to Health Canada on August 13. It is still listed as "under review."  

Experts emphasize that vaccination is still the primary and most effective defence against COVID, but welcome the possibility of an oral medication to save lives and prevent hospitalization among people who become infected. Here's what we know about COVID-19 antivirals so far. 

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Merck's pill, called molnupiravir, passed an initial phase of the approval process on Nov. 30, when an expert advisory panel to the U.S. Food and Drug Administration (FDA) recommended the agency approve the drug. But both the FDA and the Centers for Disease Control and Prevention (CDC) still need to officially approve it. 

Pfizer submitted its drug, called Paxlovid, to the FDA on Nov. 16. 

Both the Merck and Pfizer medications are for adults who are in the early stages of COVID-19 with mild to moderate symptoms and at risk of deteriorating into severe illness and requiring hospitalization. Those at risk could include people who are older or who have underlying conditions, such as obesity, diabetes or heart disease.  

Patients in the clinical trials were unvaccinated. More research is needed, experts say, to find out if the antivirals could help people who are vaccinated but get a breakthrough infection. 

Pfizer's preliminary results of its clinical trial showed a reduction between 85 and 89 per cent in the combined rate of hospitalization and death among those who got the drug, compared to those who got a placebo pill.  

For patients who started taking the drug within three days of the onset of symptoms, the hospitalization rate was 89 per cent lower. The reduction in hospitalization or death was slightly less (85 per cent) among those who took the pills a day or two later (within five days of symptoms developing).

No one who took the Pfizer antiviral drug died, the company said. 

WATCH | Dr. Zain Chagla says antiviral drugs for COVID-19 look promising: