If there are several antiviral drugs against Covid-19, one of them gives rise to particular hope: paxlovid, developed by the American laboratory Pfizer, already authorized in the United States, Israel and South Korea. This treatment takes the form of a pill and presents, according to the manufacturer’s data, very encouraging results, even if it cannot replace the vaccine: it would reduce to 89% the risk of hospitalization, death and contracting a disease. severe form of the virus. But certain inherent weaknesses in the drug leave skeptics about its real impact on the pandemic.
Which countries have authorized the Pfizer pill?
South Korea is the latest country to authorize paxlovid “urgently” on Monday. The day before, the Israeli health system had approved the use of paxlovid and molnupiravir (developed by Merck), before ordering several thousand tablets of molnupiravir, which should arrive within two weeks. In the United States, the United States Medicines Agency (FDA) urgently authorized Pfizer’s pill on December 22 for people with mild and moderate symptoms, who could then become seriously ill. “This authorization provides a new tool to fight Covid-19 at a crucial moment in the pandemic, where new variants are emerging”, said Patrizia Cavazzoni, an official of the FDA. On the European side, the European Medicines Agency (EMA) approved its use in an emergency, in a press release published on December 16: “The medicine, which is not yet authorized in the EU, can be used to treat adults with Covid-19 who do not need supplemental oxygen and who are at increased risk of developing a severe form of the disease. sickness.” The EMA opinion aims to “Support the national authorities who can decide on a possible early use of the drug” before the marketing authorization.
What is it about ?
Paxlovid is an ‘antiviral medicine’, which means that it works by reducing the ability of the virus to reproduce, and thus significantly slows down the disease. The Pfizer pill attacks in particular the protease enzyme, which is crucial in the virus replication process. The laboratory assures that the drug is effective against the omicron variant.
According to clinical trials conducted by Pfizer, and whose data have only been published in the form of a press release, paxlovid is 89% effective in preventing hospitalizations, severe forms and death in high-risk patients, when treatment is started within five days of symptom onset. Reviews by Pfizer show that 1% of patients who took paxlovid within five days were hospitalized within 28 days of starting treatment, compared to 6.7% of patients who took placebo. The drug would be inoculated to anyone over the age of 12, suffering from comorbidities such as diabetes or obesity, who would be at risk of developing a severe form of Covid.
How it works ?
The main advantage of paxlovid is its ease of use, since it is taken at home in pill form. However, the treatment remains rather cumbersome: it is necessary to ingest the two active substances of the drug, PF-07321332 and ritonavir, available as separate tablets. This represents three tablets to be taken twice a day for five days. That is a total of thirty pills.
The effectiveness of treatment depends mainly on when it is given: paxlovid reduces the risks if it is given a few days after the onset of symptoms, a maximum of five. The treatment would be even more effective if it is given within 72 hours. It therefore requires an extremely rapid response from all actors in the diagnostic and treatment chain.
What are the limits of this treatment?
How do you convince patients to take treatment when their symptoms are still in their infancy and appear to be mild? People at risk often already take fairly heavy drug treatments, to which should be added the daily intake of six to eight additional pills (eight for the Merck pill). A public awareness campaign is needed.
Especially since, as the EMA emphasizes, paxlovid is contraindicated with the taking of certain drugs, either because it “May cause a harmful increase in blood levels”, either because “Some medicines can reduce the activity of paxlovid itself”. At this time, Pfizer treatment is not recommended for pregnant women, as it could have an impact on the growth of the fetus, as well as in people with impaired kidney or liver function.
Side effects reported up to 34 days after the last paxlovid pill swallowed are taste change (dysgeusia), diarrhea and vomiting.