On Tuesday, the US pharmaceutical company Pfizer confirmed the effectiveness of Paxlovid, its new drug against severe forms of COVID-19, announcing that it has obtained very promising results and in line with those communicated last month. The pills produced by Pfizer could be the first truly effective treatment for the disease caused by the coronavirus, along with molnupiravir – a drug developed by the pharmaceutical company MSD (Merck) – but recently found less encouraging results than those reported in a first phase of experimentation.
Vaccines continue to be the most important tool to keep the effects of the pandemic under control: so far they have proved essential to reduce severe cases of COVID-19, and consequently hospital admissions and deaths.
However, drugs against the disease could prove useful in treating people who are still ill and who are more at risk of developing severe symptoms, against which there are currently not many specific and effective treatments. COVID-19 pills could also prove useful in poorer countries, with very low vaccination rates and the prospect of long lead times to improve vaccination coverage.
Paxlovid
According to Pfizer data, if taken within three days of the onset of symptoms, Paxlovid reduces the risk of hospitalization and death by 89 percent ( compared to those who do not take it and develop severe forms of the disease). If given five days after the first symptoms, the risk reduction is more or less similar, equal to 88 percent.
The results are based on a trial that involved 2,246 unvaccinated volunteers with characteristics such as to be at high risk of developing severe forms of COVID-19. Also according to data released by Pfizer, 0.7 percent of the participants who received Paxlovid were hospitalized four weeks after the start of the trial, while no deaths were recorded. In the group of volunteers who did not receive the drug, but a substance that does nothing (placebo), the percentage was 6.5 percent.
Things to know about the coronavirus The Coronavirus Post newsletter catch up on the latest news: it's free and arrives every Thursday at 6pm. To receive it, write your email address here and press the button below. Having read the information, I agree to send the Newsletter Paxlovid is an antiviral that interferes with the mechanisms used by the coronavirus to replicate within the cells of infected people. The treatment consists of taking 30 tablets over five days between Paxlovid and ritonavir, another antiviral drug developed long ago against HIV. Taking this second medicine allows Paxlovid to stay active longer in the body, leading to better results.
In addition to high-risk patients, Pfizer is testing individuals with lower risk factors related to COVID-19. Preliminary data communicated so far by the company indicate that the use of Paxlovid reduced the risk of hospitalization and death by 70 percent compared to the control group.
Clinical tests involved people who had mostly contracted the delta variant of the coronavirus, the most widespread since the summer in much of the world. Pfizer however anticipated that in some laboratory tests the new drug has shown that it can also counteract the forms of COVID-19 caused by the omicron variant.
Last month Pfizer had already applied to the Food and Drug Administration (FDA), the US federal agency that deals with drugs, the authorization for Paxlovid thanks to a first series of preliminary data on its efficacy and safety. The new trial results will be added to the application and could speed up the authorization process, making the drug available within a few weeks in the United States.
Molnupiravir
The news was positively received by numerous observers, after the recent disappointment deriving from the not very comforting data on the efficacy of molnupiravir, the pill developed and produced by MSD. Last October the company announced that the drug reduced the risk of hospitalization and death due to severe forms of COVID-19 by half, if taken within five days of the onset of symptoms.
MSD then continued testing and experimentation, obtaining more disappointing data from their final analysis. The efficacy of molnupiravir was in fact around 30 percent and some doubts about its safety subsequently emerged, to the point of complicating the authorization process of the pill at the FDA. However, a commission from the US agency had voted in favor of molnupiravir at the end of November, but the FDA has not yet decided on its authorization.
Molnupiravir is an oral pill, taken twice a day for five days. It has the ability to interfere with the processes that viruses use to replicate within cells. One of the targets is a particular enzyme (polymerase) involved in the transcription of the viral genetic material, that is, the instructions that the cell needs to make new copies of the virus. The drug causes the polymerase to incorrectly transcribe instructions, making it impossible for the virus to replicate.
The drug has been authorized in the United Kingdom, while the drug control authorities in France have decided to reject the authorization request presented by MSD, considering the relationship between the risks and benefits that its use would bring is unsatisfactory.
