FDA panel narrowly endorses Merck pill, despite reduced efficacy

A Food and Drug Administration advisory panel on Tuesday narrowly endorsed the uPse of Merck and Ridgeback Biotherapeutics’ oral Covid treatment pill, despite questions about the drug’s effectiveness, safety and whether it would help the virus mutate into even more dangerous variants.

The FDA’s Antimicrobial Drugs Advisory Committee voted 13 to 10 to recommend emergency authorization of molnupiravir, an oral antiviral drug initially hailed as a potential game changer in the battle against Covid since it can be taken at home instead of at a hospital like other treatments. It’s designed to treat adults with mild to moderate symptoms of Covid-19 who are at high risk of severe disease. The 800 milligram pill is taken every 12 hours for five days after symptom onset.

The drug needs final authorization from the FDA and Centers for Disease Control and Prevention before it’s available to the public on an emergency basis. The FDA doesn’t have to take the panel’s advice, but it often does.

Many members of the advisory committee described the vote as a difficult one, in which they had to carefully weight the risks and benefits of a drug that raised unanswered questions, but could help adults at risk of severe Covid.

Merck originally said the drug was more than 50% effective in preventing hospitalizations and death, but a more full set of data presented to the FDA on Tuesday noted the drug is just 30% effective.

The FDA and Merck both recommended against using the drug in kids and pregnant women. Molnupiravir was found to be lethal to embryos in pregnant rats, also causing birth defects and reducing fetal body weight. It also caused other defects that interfered with bone growth in young pups, along with other abnormalities, the data shows.

Molnupiravir works by prompting the virus that causes Covid to mutate and produce errors inhibiting its ability to replicate and spread. However, some doctors and scientists worried that it could also enable the virus to mutate in a way that makes vaccines and treatments less effective.

“Even if the probability is very low, 1 in 10,000 or 100,000, that this drug would induce an escape mutant from which the vaccines we have do not cover, that could be catastrophic for the whole world actually,” Dr. James Hildreth, CEO of Meharry Medical College in Nashville, Tenn., told the panel.

Nicholas Kartsonis, Merck’s senior vice president of clinical research, said the company does not have data on the chances such a mutation could evolve. However, Kartsonis noted that Merck has not seen an increased rate of unusual changes to the spike protein, which the virus uses to attach to human cells, compared with a placebo group in clinical trials. Hildreth told Kartsonis that it is incumbent on Merck to estimate the likelihood of escape mutants.

“We are exploring the feasibility of using currently available public SARS CoV-2 to sequence databases to monitor for the emergence of these novel variants in the replicase complex as well as the spike…