FDA authorizes second COVID antiviral pill, from Merck, if no alternatives available
The Food and Drug Administration announced Thursday it had authorized molnupiravir, a drug produced by Merck and Ridgeback Biotherapeutics, to treat some American adults with COVID-19 who are at risk of severe disease when no other options are available. The pills are meant to be started within five days of developing the first symptoms.
"Molnupiravir is limited to situations where other FDA-authorized treatments for COVID-19 are inaccessible or are not clinically appropriate and will be a useful treatment option for some patients with COVID-19 at high risk of hospitalization or death," said the FDA's Dr. Patrizia Cavazzoni.
The agency's move marks the second emergency authorization for an antiviral pill to treat COVID-19 in as many days, after the FDA greenlighted Pfizer's Paxlovid on Wednesday.
It comes ahead of a feared surge that could overwhelm hospitals as the Omicron variant rapidly spreads, with doctors facing a shortage of effective drugs to treat Omicron cases this winter. Cavazzoni said that the FDA believes both antiviral pills will work against Omicron.
Molnupiravir's authorization comes close to a month after the FDA's outside advisers had wrestled with the pill's additional risks and smaller efficacy in a narrow vote.
Merck and Ridgeback initially said an interim analysis of their trial showed antiviral could cut the risk of hospitalization or death by 50% compared to placebo. The drugmakers' final analysis showed a smaller relative risk reduction of 30%.
For Paxlovid, Pfizer has touted an efficacy of 89% among high-risk adults with COVID-19, and says their pill does not carry the same theoretical risks as Merck's drug of driving worrying mutations or potentially damaging the DNA of recipients.
The two medications work differently. Paxlovid works by trying to block the ability of the virus to make copies of itself in the body. Molnupiravir tries to drive a random cascade of errors in the replication process, aiming to stunt its spread.
FDA officials acknowledged the concern voiced by some of their advisers last month that molnupiravir might lead to the spread of an "escape mutant." However, they said the "hypothetical risk" would be mitigated by instructions for people to isolate while taking molnupiravir, which in trials dramatically reduced the amount of virus in the body over the five day course of treatment.
The agency's advisers were not asked to weigh in on the pill from Pfizer, which announced final trial results last week.
"We felt that we needed to proceed expeditiously with the authorization and we did not have pressing scientific questions that would benefit from advisory committee discussion," the FDA's Dr. John Farley told reporters on Thursday.
In its authorization of the Merck pill, the FDA said it would ban children from taking the drug over concerns it could affect the development of bones and cartilage. Women are also discouraged from taking the drug if they are pregnant, and are recommended to take steps to avoid becoming pregnant while receiving molnupiravir.
"I think that, if an alternative agent comes along with better efficacy and fewer safety concerns, that this EUA should be immediately reconsidered," said Dr. Richard Murphy, a Veterans Affairs physician on the committee last month.
However, White House officials say some 3 million courses of molnupiravir will be available by the end of next month from Merck and Ridgeback Biotherapeutics — compared to only 265,000 expected to be shipped by Pfizer of Paxlovid next month.
Less than 65,000 courses will be available of Paxlovid starting the first week of January, the U.S. Department of Health and Human Services disclosed Wednesday.
"According to Pfizer, the complex chemistry involved in creating the active ingredient in the pill means production takes about six to eight months. So, supply of this product will ramp up over the next several months," Jeffrey Zients, the White House's top COVID-19 official, told reporters on Wednesday.
Merck's treatment will arrive ahead of a feared wave over the next month of hospitalizations and deaths caused by the fast-spreading Omicron variant, which has rendered most available monoclonal antibody drugs ineffective.
Federal officials announced Thursday they would halt distribution of monoclonal antibody drugs from Eli Lilly and Regeneron, after the Centers for Disease Control and Prevention estimated Omicron had become the predominant variant nationwide.
Jurisdictions and providers are currently rationing out an "extremely limited" supply of sotrovimab, the antibody drug from GlaxoSmithKline and Vir Biotechnology
Though some studies now suggest Omicron may lead to a smaller risk of hospitalization, scientists and health authorities warn that the variant could still be severe enough to inflict a massive toll given its rapid spread.
"Regardless of where the relative severity of Omicron falls, the sheer number of cases projected means that even a relatively mild severity of the Omicron variant will severely stress, if not overwhelm, already strained health care systems across the country," a consortium of disease forecasters said in a joint statement on Wednesday.
A panel of experts convened by the National Institutes of Health is expected to issue guidelines soon on how to triage limited supplies of the two antiviral pills, as well as the monoclonal antibody treatments and remdesivir, an antiviral that is administered intravenously.
The group previously recommended rationing limited supplies of monoclonal antibodies among high risk patients for treating those who are unvaccinated or otherwise unprotected by the vaccines, like those who are immunocompromised.
"We've asked the NIH Guidelines Committee to put together a recommendation of when someone comes in with an acute infection and is in a risk group, which is what you want this to be for since we have a limited supply, that we would have a prioritization of what the best approach would be," Dr. Anthony Fauci, the president's chief medical adviser, told reporters on Wednesday.