Pfizer begins testing of a COVID-19 pill

US drugmaker Pfizer said Monday it began mid- and late-stage clinical trials of a pill to prevent COVID-19 in people exposed to the virus.

Several companies are working on possible oral antivirals, which would mimic what the drug Tamiflu does against influenza and prevent the disease from progressing to a severe state.

“We believe that fighting the virus will require effective treatments for people who contract the virus or have been exposed to it, complementing the impact that vaccines have had”said Mikael Dolsten, the company’s head of scientific research.

Pfizer began developing this drug, dubbed PF-07321332, in March 2020 and is evaluating it in combination with ritonavir, which is already used against the AIDS virus.

The clinical trial will involve 2,600 adults who will take part in the trial as soon as they have signs of COVID-19 infection or as soon as they know they were exposed to the virus.

They will randomly receive a combination of PF-07321332 and ritonavir, or a placebo, twice a day for five to ten days.

The purpose of the test is to determine the safety and efficacy of the drugs in preventing an infection of SARS-CoV-2 -the virus that causes COVID-19- and the development of symptoms by day 14.

The pill is known as a “protease inhibitor” and in laboratory tests it has been shown to stop the replicating effect of the virus.

If it works in real life, it may only be effective in the early stages of infection.

By the time COVID-19 progresses to a severe state, the virus has basically stopped replicating and patients suffer from an overactive immune response.