The US pharmaceutical company Pfizer announced on Friday that its novel antiviral treatment reduced the risk of hospitalisation and death in Covid-19 patients by 89 per cent when started soon after the onset of symptoms in a global clinical trial with sites in Calcutta and other parts of India.

The trial observed no deaths in patients who received the treatment but 10 deaths in patients who received a placebo, the company said. An independent expert panel monitoring the trial, noting the overwhelming efficacy, recommended the trial be stopped to speed up the drug’s journey into the clinic.

“(This) is a real game-changer in the global efforts to halt the devastation of this pandemic,” Pfizer’s chief executive officer Albert Bourla said in a statement. “These data suggest that our oral antiviral candidate, if approved by regulatory authorities, has the potential to save patients’ lives, reduce the severity of Covid-19 infections, and eliminate up to nine out of 10 hospitalisations.”

The treatment involves a novel antiviral drug named Paxlovid, specially designed to block a key enzyme that SARS-CoV-2, the virus that causes Covid-19, needs to replicate. Paxlovid has to be co-administered with a low dose of another antiviral, called ritonavir.

This is the second oral antiviral treatment to show promise after the US company Merck reported earlier this year that a drug named molnupiravir reduces the risk of hospitalisation or death among Covid-19 patients by 50 per cent.

The UK on Thursday became the world’s first country to authorise the use of molnupiravir in the treatment of mild-to-moderate Covid-19 in adults who have at least one risk factor for developing severe illness.

The results announced by Pfizer place the efficacy at a higher level — 89 per cent — than that reported for molnupiravir.

When the Paxlovid treatment was started within five days of the onset of symptoms, the trial observed that six of 607 patients (1 per cent) were hospitalised, compared to 41 of 612 patients (6.7 per cent) who received the placebo. In the overall study population, there were no deaths in the treatment group, and 10 in the group that received the placebo.

Pfizer said if the treatment was approved by regulatory authorities, it could be prescribed as an at-home treatment to be started early after symptoms to help reduce illness severity, hospitalisation and deaths.

The company said it would offer the treatment through a tiered pricing strategy based on the income level of each country. “High and upper middle income countries will pay more than lower income countries,” the company said in a statement.

Pfizer said it had entered into advance purchase agreements with multiple countries and was in negotiations with several others.

The interim data analysis was based on 1,219 adults enrolled in the trial by September 29, 2021, from clinical trial sites across North and South America, Europe, Africa and Asia.

According to the clinical trial documents, hospitals in Calcutta, Ajmer, Bangalore, Kochi, Mumbai, Pune and Raipur were enrolling patients for the trial. A query to Pfizer sent by this newspaper asking for the count of patients enrolled from India has remained unanswered.

The safety data review included a larger group of 1,881 patients. Adverse events were comparable between Paxlovid (19 per cent) and placebo (21 per cent), most of which were mild. The trial randomised each patient to receive either Paxlovid or placebo every 12 hours for five days.

Pfizer said it was currently expecting to produce more than 180,000 packs by the end of 2021 and at least 50 million packs by the end of 2022, of which 21 million would be produced in the first half, Reuters reported.

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, the Reuters report added.