Paxlovid is a combination of two pills taken over five days that was shown in a clinical trial of 2,200 people to be safe and reduced the risk of hospitalisations and deaths among at-risk people by 88% when taken within five days of symptom onset.
“Today’s authorization introduces the first treatment for COVID-19 that is in the form of a pill that is taken orally - a major step forward in the fight against this global pandemic,” said FDA scientist Patrizia Cavazzoni in a statement.
“This breakthrough therapy, which has been shown to significantly reduce hospitalisations and deaths and can be taken at home, will change the way we treat COVID-19, and hopefully help reduce some of the significant pressures facing our healthcare and hospital systems,” added Pfizer CEO Albert Bourla in a statement.
The FDA stressed it should complement rather than replace vaccines, which remain the frontline tool against the coronavirus.
But pills that are available at pharmacies should be much easier to access than synthetic antibody treatments, which require infusions administered by drip at hospitals or specialised centres.
In an unusual move, the FDA did not convene its customary panel of independent experts to review the in-depth data surrounding Pfizer’s pill ahead of authorisation.
The European Union’s drug regulator last week allowed member states to use Pfizer’s COVID treatment ahead of formal approval, as an emergency measure to curb an Omicron-fueled wave.
The US has agreed to pay US$5.3 billion (B178bn) for 10 million courses, with delivery starting this year and concluding next, according to Pfizer.
The authorisation comes as cases are surging across the United States, driven by Omicron, the most infectious variant seen to date.
The highly-mutated variant is better able to bypass prior immunity, and health authorities are urging the public to get boosted with mRNA vaccines in order to restore a higher degree of protection.
Unlike vaccines, the COVID pill does not target the ever-evolving spike protein of the coronavirus, which it uses to invade cells. It should in theory be more variant proof, and Pfizer has said preliminary lab studies have backed up that hypothesis.
Paxlovid is a combination of a new molecule, nirmatrelvir, and HIV antiviral ritonavir, that are taken as separate tablets.
Nirmatrelvir blocks the action of an enzyme the virus needs to replicate, while ritonavir slows down nirmatrelvir’s breakdown so it remains in the body for longer and at higher levels.
Possible side effects include impaired sense of taste, diarrhea, high blood pressure and muscle aches, the FDA said.
There are also potential harmful interactions for people using other drugs, and using Paxlovid in people with uncontrolled or undiagnosed HIV-1 infection may lead to HIV-1 drug resistance, the agency added.
Authorisation is still awaited for another COVID pill, developed by Merck, which is also taken over five days and has been shown to reduce hospitalizations and deaths by 30% among high-risk people.
Independent experts voted in favor of that treatment by a narrow margin, but expressed concerns surrounding its safety, such as potential harm to fetuses and possible damage to DNA.
The two treatments work in different ways inside the body, and Pfizer’s pill is not thought to carry the same level of concerns. Merck’s treatment has been greenlit by Britain and Denmark.