The company's filing comes as new infections are rising once again, driven mainly by hot spots in states where colder weather is driving more Americans indoors.
It is one of a handful of pills that have recently been shown to significantly cut hospitalizations and deaths among people infected with COVID-19. If authorized by the Food and Drug Administration it could be a major step toward managing the pandemic and returning to normal, offering an easy, effective way for patients people to treat themselves at home.
"We are moving as quickly as possible in our effort to get this potential treatment into the hands of patients, and we look forward to working with the U.S. FDA on its review of our application," said Albert Bourla, Pfizer's CEO, in a statement.
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All FDA authorized treatments against COVID-19 require an IV or injection given by a health professional at a hospital or clinic.
FDA regulators will scrutinize company data on the safety and effectiveness of the drug, which will be sold as Paxlovid, before making a decision.
The FDA is holding a public meeting later this month where outside experts will scrutinize a competing drug from Merck, before voting on whether to recommend approval. The FDA isn't required to convene such meetings and it's not yet known whether Pfizer's drug will undergo a similar public review.
Some experts predict various COVID-19 therapies eventually will be prescribed in combination to better protect against the worst effects of the virus.
Several smaller drugmakers are also expected to seek authorization for their own antiviral pills in coming months.
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Pfizer reported earlier this month that its pill cut hospitalizations and deaths by 89% among high-risk adults who had early symptoms of COVID-19. The company studied its pill in people who were unvaccinated and faced the worst risks from the virus due to age or health problems, such as obesity. If authorized, the FDA will have to weigh making the pill available for vaccinated people dealing with breakthrough infections.
For best results, patients need to start taking the pills within three days of symptoms, underscoring the need for speedy testing and diagnosis. That could be a challenge if another COVID-19 surge leads to testing delays and shortages seen last winter.
Pfizer's drug is part of a decades-old family of antiviral drugs known as protease inhibitors, which revolutionized the treatment of HIV and hepatitis C. The drugs block a key enzyme which viruses need to multiply in the human body. That's different than the Merck pill, which causes tiny mutations in the coronavirus until the point that it can't reproduce itself.
On Tuesday, Pfizer signed a deal a with U.N.-backed group to allow generic drugmakers to produce low-cost versions of the drug for use in 95 countries, a move that could make the treatment available in more than half of the world's population.
The U.S. has approved one other antiviral drug for COVID-19, remdesivir, and authorized three antibody therapies that help the immune system fight the virus. But they usually have to be given via time-consuming infusions at hospitals or clinics, and limited supplies were strained by the last surge of the delta variant.