Britain approves Pfizer's antiviral Covid-19 pill Paxlovid

Britain's Medicines and Healthcare products Regulatory Agency (MHRA) said on Friday that it has approved Pfizer's Oral Covid-19 antiviral medicine, Paxlovid, for people with mild to moderate Covid-19 who are at high risk of developing severe cases.

Paxlovid is an antiviral medicine with a combination of active ingredients, PF-07321332 and Ritonavir that works by inhibiting a protease required for virus replication. The drug has been authorized for use in people aged 18 and older who have mild to moderate Covid-19 infections and at least one risk factor for developing severe illness.

Such risk factors include obesity, older age (60 years or older), diabetes mellitus, or heart disease.

The two active substances of Paxlovid come as separate tablets that are packaged together and taken together, twice a day orally for five days.

PF-07321332 is a new antiviral, meaning that it has not been approved for use before. However, Ritonavir has been used alongside some HIV medicines for many years to 'boost' their activity, which is similar to what it is doing for PF-07321332, the MHRA said in a statement.

In a clinical trial, a five-day treatment course of Paxlovid reduced the risk of Covid-19 related hospitalization and death within 28 days by 89 per cent when compared to a placebo group when treatment was started within three days of the onset of Covid-19 symptoms.

Hospitalizations, deaths

The number of hospitalizations and deaths were 0.8 per cent in the Paxlovid group, compared with 7 per cent in the placebo group.

Based on the clinical trial data, Paxlovid is most effective when taken during the early stages of infection, and so the MHRA recommends its use as soon as possible and within five days of the start of symptoms.

The MHRA said that it is too early to know whether the Omicron variant has any impact on Paxlovid's effectiveness, but the MHRA is proactively working with the company to establish this.