By Sandra Rose  | 

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Pfizer says its new Covid-19 pill will cut the risk of hospitalization or death by 89% when taken with a widely used HIV drug.

Pfizer's antiviral pill is second behind Merck Pharmaceutical, which submitted data for its anti-Covid pill to the FDA last month.

Pfizer's new pill, when taken with the HIV drug, showed strong effectiveness for treating Covid-19 at the first sign of illness in high-risk adults.

Pfizer's pill is part of a class of medicines called protease inhibitors that work by inhibiting an enzyme the virus needs to multiply inside human cells.

The coronavirus enter host cells by binding to ACE2 receptor enzymes in cells. People with higher levels of ACE2 (morbidly obese and HIV patients) are at higher risk for sickness and death.

The HIV drug slows the breakdown of Pfizer's pill so it will remain active in the body for long periods at higher concentrations.

"I think this medicine will change the way things are happening right now that will save millions and millions of lives, it has the potential to do it," Pfizer CEO Albert Bourla -- a veterinarian -- told CNBC's "Squawk Box."

Pfizer will submit data to the Food and Drug Administration (FDA) later this month.