The UK medicines regulator will assess Pfizer’s novel antiviral Covid treatment, after clinical trials showed it to be 89% effective at reducing hospitalisation of high-risk patients.
The UK has procured 250,000 doses of the treatment, which is an at-home oral antiviral cocktail to be taken three times daily.
The treatment, to be marketed at as Paxlovid, is a combination of existing antiviral drug ritonavir – currently used to treat HIV/AIDS – and a novel antiviral agent named PF-07321332.
The phase 2/3 trial showed that upon starting treatment within 3-5 days of developing symptoms, 28 days in there were no deaths among the trial group, while 10 deaths occurred among those receiving a placebo.
Pfizer said it would now ‘cease further enrolment into the study due to the overwhelming efficacy demonstrated in these results’ and is planning to submit data for emergency authorisation from regulators ‘as soon as possible’.
The news comes as the UK Medicines and Healthcare Regulatory Agency (MHRA) became the first drugs regulator in the world to approve Merck’s novel at-home antiviral drug, molnupiravir (brand name Lagevrio) this week.
Merck’s drug was found to be effective in reducing the risk of hospitalisation or death for at-risk non-hospitalised adults with mild to moderate Covid-19 by 50% in clinical trials, and the UK has procured 480,000 doses.
Health and Social care secretary Sajid Javid said: ‘Incredible results from Pfizer showing their antiviral medicine cuts the risk of hospitalisation or death from Covid-19 by almost 90%.
‘We have procured 250,000 doses of this promising treatment on behalf of the whole UK and our independent medicines regulator, the MHRA, will now assess its safety, quality and effectiveness.
‘If approved, this could be another significant weapon in our armoury to fight the virus alongside our vaccines and other treatments, including molnupiravir, which the UK was the first country in the world to approve this week.’
There is as yet no information on how at-home antiviral treatments will be deployed to patients but details will follow in due course, the Department of Health and Social Care has said.
Mr Javid said last month that the Government was ‘working to get in place plans for deployment of the at-home antiviral treatments, including the delivery of a national study, to collect further data on who would most benefit’.
The Government had set a target of having at-home antiviral treatments approved by this autumn.
Health officials have said the most vulnerable would be eligible first including the elderly and those with weakened immune systems.
However, Pfizer said in future its ‘protease inhibitor’ treatment, which is the ‘first oral antiviral of its kind’, could also be used to ‘reduce the probability of infection following exposure’.
‘It has demonstrated potent antiviral in vitro activity against circulating variants of concern, as well as other known coronaviruses, suggesting its potential as a therapeutic for multiple types of coronavirus infections,’ the company statement added.
It follows the UK regulatory approval in August of monoclonal Covid antibody treatment Ronapreve which is now being used to treat hospitalised patients.
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How Pfizer’s oral Covid antiviral works
- Paxlovid is an investigational SARS-CoV-2 protease inhibitor antiviral therapy, specifically designed to be administered orally so that it can be prescribed at the first sign of infection or at first awareness of an exposure, potentially helping patients avoid severe illness which can lead to hospitalisation and death.
- PF-07321332 is designed to block the activity of the SARS-CoV-2-3CL protease, an enzyme that the coronavirus needs to replicate. Co-administration with a low dose of ritonavir helps slow the metabolism, or breakdown, of PF-07321332 in order for it to remain active in the body for longer periods of time at higher concentrations to help combat the virus.
- PF-07321332 inhibits viral replication at a stage known as proteolysis, which occurs before viral RNA replication. In preclinical studies, PF-07321332 did not demonstrate evidence of mutagenic DNA interactions.