NEW YORK, Oct 1 — A pill developed by US drugmaker Merck could half the chances of dying or being hospitalised for those most at risk of contracting severe Covid-19, with experts hailing it as a potential breakthrough in how the virus is treated.

If it gets authorisation, molnupiravir, which is designed to introduce errors into the genetic code of the virus, would be the first oral antiviral medication for Covid-19.

Merck and its partner Ridgeback Biotherapeutics plan to seek US emergency use authorisation for the pill as soon as possible and to make regulatory applications worldwide.

"This is going to change the dialogue around how to manage Covid-19,” Merck Chief Executive Robert Davis told Reuters.

Current treatment options include Gilead Sciences Inc’s antiviral remdesivir and generic steroid dexamethasone, although both are generally only given once a patient has already been hospitalised.

"An oral antiviral that can impact hospitalisation risk to such a degree would be game changing,” Amesh Adalja, senior scholar at the Johns Hopkins Centre for Health Security, said.

Existing treatments are "cumbersome and logistically challenging to administer. A simple oral pill would be the opposite of that,” Adalja added.

Due to the positive results, which sent Merck’s shares up more than 9 per cent in early New York trading, the Phase 3 trial is being stopped early at the recommendation of outside monitors.

Shares of Covid-19 vaccine manufacturers Pfizer and Moderna dropped by nearly 3 per cent and 10 per cent respectively, moves Michael Yee, a biotechnology analyst at Jefferies, said indicated investors believe "people will be less afraid of Covid and less inclined to get vaccines if there is a simple pill that can treat Covid”.

Pfizer and Swiss pharmaceuticals group Roche are racing to develop an easy-to-administer antiviral pill, but so far only antibody cocktails which have to be given intravenously are approved for non-hospitalised patients.

A planned interim analysis of 775 patients in Merck’s study looked at hospitalisations or deaths. It found that 7.3 per cent of those given molnupiravir were hospitalised and none had died by 29 days after treatment, compared with 14.1 per cent of placebo patients. There were eight deaths among placebo patients.

"Antiviral treatments that can be taken at home to keep people with Covid-19 out of the hospital are critically needed,” Wendy Holman, Ridgeback’s CEO, said in a statement.

‘Work with alacrity’

Scientists welcomed the potential new treatment to help prevent serious illness from the virus, which has killed almost 5 million people around the world.

"The availability of a well-tolerated, effective oral antiviral will be particularly useful in supplementing vaccination as a means to reduce the proportion of patients needing hospital care,” Penny Ward, visiting professor in pharmaceutical medicine at King’s College London, said.

In the trial, which enrolled patients around the world, molnupiravir was taken every 12 hours for five days.

The study enrolled patients with laboratory-confirmed mild-to-moderate Covid-19, who had symptoms for no more than five days. All patients had at least one risk factor associated with poor disease outcome, such as obesity or older age.

Merck said viral sequencing done so far shows molnupiravir is effective against all variants of the coronavirus, including highly transmissible Delta.

It said rates of adverse events were similar for both molnupiravir and placebo patients, but did not give details.

Merck has said data shows molnupiravir is not capable of inducing genetic changes in human cells, but men enrolled in its trials have to abstain from heterosexual intercourse or agree to use contraception. Women of child-bearing age cannot be pregnant and also have to use birth control.

Merck said it expects to produce 10 million courses of the treatment by the end of 2021, with more coming next year.

The company has a US government contract to supply 1.7 million courses of molnupiravir at a price of US$700 (RM2,927) per course.

Davis said Merck has similar agreements with other governments, and is in talks with more. Merck said it plans a tiered pricing approach based on country income criteria.

Merck has also agreed to license the drug to several India-based generic drugmakers, which would be able to supply the treatment to low- and middle-income countries.

Molnupiravir is also being studied in a Phase 3 trial for preventing coronavirus infection in people exposed to the virus.

Merck officials said it is unclear how long the FDA review will take, although Dean Li, head of Merck’s research labs, said "They are going to try to work with alacrity on this”. — Reuters