UPDATED: Merck's oral COVID-19 antiviral slashes hospitalizations, prevents deaths in phase 3, sparking race to file with FDA

The wait for an oral antiviral against COVID-19 may almost be over. Friday, Merck reported its prospect halved the risk of hospitalization and death in phase 3, spurring an early end to the study and a race to get emergency use authorization.

An effective oral treatment for mild to moderate COVID-19 is one of the big remaining gaps in the pandemic drug arsenal. Vaccines are stopping many people from developing symptomatic disease altogether, and treatment of severe COVID-19 has improved throughout the pandemic. But options for recently infected, high-risk people are limited to relatively expensive and logistically challenging anti-SARS-CoV-2 antibodies. 

Molnupiravir could be a cheaper, oral way to stop people developing severe COVID-19. Merck, which is developing the drug with Ridgeback Biotherapeutics, has interim data from 762 mild to moderate patients who had at least one risk factor associated with poor disease outcomes.

In the molnupiravir cohort, 7.3% of participants were hospitalized or died through Day 29, compared to 14.1% of people who received placebo. There were eight deaths in the placebo group. None of the 385 recipients of molnupiravir died. Delta, gamma and mu variants accounted for almost 80% of the cases.

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The strength of the efficacy data led the independent monitoring committee to recommend the trial be stopped early. Merck, in consultation with the FDA, has stopped enrollment in the trial. While the interim analysis took place halfway to the original recruitment target, the study was around 90% enrolled when Merck pulled the plug.

Merck is now racing to get the clinical data ready for submission to the FDA to support emergency use authorization. In parallel, the company is continuing to make molnupiravir with a view to being able to ship 10 million courses of treatment this year. The U.S. government has already placed an order for 1.7 million courses.

With the top-line safety data coming in clean, Merck looks well set to bring molnupiravir to market but is yet to share a detailed look at the results. The safety of molnupiravir will likely be scrutinized as it works differently from established antivirals, and the limited contribution of U.S. sites may be a point of discussion. Ex-U.S. countries accounted for 93% of participants, despite more than 30 of the 167 sites being located in the U.S. 

Merck climbs

Even so, the news sent Merck's shares skyward by nearly 10% to $82.43 around 10:22 a.m. ET on Oct. 1. Big Pharma shares tend to remain pretty stable, so a jump like this is notable. 

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Merck's "impressive molnupiravir data could help alter the course of the pandemic," RBC Capital Markets analyst Brian Abrahams said. 

"We believe that the availability of an effective oral drug that can be given in the outpatient setting can blunt the risks associated with breakthrough infections, and reduce mortality in the unvaccinated, which can begin to move the nation out of the pandemic and hasten reopening," Abrahams said. 

Merck is also working on a trial of molnupiravir as a preventative medicine with a read out sometime in the first half of 2022. This trial could help reduce the risk of exposure to COVID-19, especially for those who are immuno-compromised or healthcare workers, Abrahams noted. 

Jefferies pointed out that Merck's results compare to existing antibodies, which achieve about a 70% reduction in hospitalization but are much more onerous to administer. 

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Merck's results are also a good read through for Pfizer and Roche, which have oral COVID-19 treatments in the works, Jefferies added. Data is due for Pfizer's candidate by the end of the year while Roche is expected to drop data in the first half of 2022. 

One odd side effect of an effective treatment for COVID-19 is that people could be less likely to get first vaccines or boosters, both Jefferies and RBC said. This could have a small effect down the road for Moderna. 

Editor's note: This story was updated at 10:45 a.m. ET on Oct. 1 to include analyst commentary.