A panel of health experts appointed by the US government was meeting Tuesday to decide whether to endorse Merck’s pill to treat Covid-19, potentially paving the way for the medicine to be available within weeks.
Molnupiravir, already authorized in Great Britain, has been shown to reduce the rate of hospitalizations and deaths among high-risk Covid patients when taken soon after infection.
Accordingly, Merck — known as MSD outside the US and Canada — is seeking an emergency use authorization (EUA) for non-hospitalized, high-risk people with mild to moderate Covid cases, taken within five days of symptom onset.
But the Food and Drug Administration (FDA), which convened Tuesday’s meeting and will have the final say after the committee takes a non-binding vote, has raised some cautionary notes.
Among these are the potential harmful effects on fetal development, which were seen in studies on rats and rabbits.
“We are not recommending use during pregnancy,” said Merck scientist Kerry Blanchard.
The company is not seeking authorization for children, and the FDA doesn’t plan to carry out pediatric trials until safety is established in juvenile rats, with concerns about the impact on bone formation.
The meeting is taking place after Merck significantly downgraded the pill’s efficacy results in preventing severe Covid-19 in at-risk people from 50 percent to 30 percent.
The new figure, released last week, was based on an analysis of more than 1,400 patients, while the earlier, interim statistic was based on results from around half that number. The factors behind the drop aren’t fully clear.
Monoclonal antibody treatments, which are given by infusion, have been shown to reduce the risk of severe Covid-19 in high-risk patients by up to 70 percent. But uptake is expected to be higher with oral antivirals once they become readily available in pharmacies to patients with prescriptions.
– More variant-proof –
Merck’s pill is taken as four capsules, twice a day, over five days — for a total of 40 pills.
It was found to be safe in its clinical trial, with non-serious adverse events such as diarrhea and dizziness occurring roughly equally between placebo group and drug group.
Molnupiravir, which was developed in partnership with Ridgeback Biotherapeutics, works by introducing mutations into the genetic material of the coronavirus, inhibiting its ability to replicate.
It is thought likely to be more variant-proof than monoclonal antibodies or vaccines, because unlike them, it does not target the ever-mutating spike proteins that dot the surface of the virus.
But this mechanism also comes with certain concerns. Because it causes mutations, some experts have said it could harm mammal DNA. But in its presentation, the FDA said rat studies showed the effect was negligible.
Another worry is whether the mutations the pill introduces might lead to dangerous evolution of the virus itself.
This is “currently a theoretical concern,” the FDA said in its slides, with no worrying mutations seen so far.
Pfizer’s Covid-19 pill, which cut hospitalizations and deaths by nearly 90 percent, works differently: instead of causing mutations, it blocks an enzyme needed for viral replication.
The US government has committed to buying 3.1 million courses of molnupiravir for approximately $2.2 billion, with the option to purchase more.
