A trial of Pfizer’s experimental antiviral pill for COVID-19 has been stopped early after the drug was shown to cut by 89 per cent the chances of hospitalisation or death for adults at risk of severe disease, the company says.
The results appear to surpass those seen with Merck & Co’s pill molnupiravir, which was shown last month to halve the likelihood of dying or being hospitalised for COVID-19 patients also at high risk of serious illness.
Full trial data is not yet available from either company.
Pfizer said it plans to submit interim trial results for its pill, which is given in combination with an older antiviral called ritonavir, to the US Food and Drug Administration as part of the emergency use application it opened in October.
The combination treatment, which will have the brand name Paxlovid, consists of three pills given twice daily.
The planned analysis of 1219 patients in Pfizer’s study looked at hospitalisations or deaths among people diagnosed with mild to moderate COVID-19 with at least one risk factor for developing severe disease, such as obesity or older age.
It found that 0.8 per cent of those given Pfizer’s drug within three days of symptom onset were hospitalised and none had died by 28 days after treatment.
That compared with a hospitalisation rate of seven per cent for placebo patients. There were also seven deaths in the placebo group.
Rates were similar for patients treated within five days of symptoms.
Antivirals need to be given as early as possible, before an infection takes hold, in order to be most effective. Merck tested its drug within five days of symptom onset.
Pfizer’s drug, part of a class known as protease inhibitors, is designed to block an enzyme the coronavirus needs in order to multiply.
Pfizer is also studying whether its pill could be used by people without risk factors for serious COVID-19 as well as to prevent coronavirus infection in people exposed to the virus.