Pharmaceutical giant Pfizer announced Friday the results from a clinical trial of a new coronavirus drug, aimed at preventing serious cases of the virus among high-risk groups – particularly those unable to receive the COVID vaccine.

According to a press release by Pfizer Friday afternoon, the experimental pill demonstrated up to 89% effectiveness in curbing hospitalizations or death among high-risk patients.

The new antiviral pill was combined with low doses of an HIV drug called ritonavir, producing an effect that Pfizer CEO Albert Bourla called a “game-changer”.

“These data suggest that our oral antiviral candidate, if approved 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 hospitalizations.”

The pill, a protease inhibitor, prevents the COVID virus from multiplying in the human body by blocking an enzyme used by COVID to multiply.

During the experimental trials, subjects took three pills twice a day for five days, with ritonavir taken in addition to prolong the pill’s effects.

Pfizer did not release the full results of the trial Friday.

The interim data comes from trials on 1,219 high-risk patients who were infected with COVID, comparing rates of hospitalization between those given a placebo versus the protease inhibitor.

Seven percent of those in the placebo group were hospitalized during the trials, compared to 0.8% of those given the protease inhibitor.

Seven patients in the placebo group died during the trials, while none died in the group which received the new pill.