FDA Says No to Merck's COVID-19 Pill in Pregnant Women

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Molnupiravir, the main component in Merck Pharmaceuticals' and Ridgeback Therapeutics’ COVID-19 oral pill, might not be safe for use in pregnant women, according to the U.S. Food and Drug Administration. 

In a briefing on the merits of the drug, the FDA said that it is not authorizing molnupiravir's use during pregnancy as there are hardly any clinical scenarios where the benefits appear to outweigh the risks. The regulator also noted that although prescribers can issue the drug at their discretion, prescriptions should come with a warning and precaution notice to clarify the risks involved.  

The FDA briefing also mentioned results from a three-month clinical study on animal models, where researchers found that molnupiravir causes cartilage and abnormal bone formation during the embryo-fetal development stage. The fetuses of rats and rabbits reportedly experienced incomplete and delayed ossification. 

Molnupiravir was given orally to pregnant rats at different dosage quantities from gestation days six to 17 and found skeletal malformations at the dose of 1000 mg/kg/day. When the drug was given to pregnant rabbits, incomplete bone development was observed at the doses of 400 mg/kg and 700 mg/kg.

"Due to the embryo-fetal toxicity and bone and cartilage development findings in vivo, the lower exposures tested in the PPND study, and the lack of a completed juvenile toxicology study, there are both known and possibly unknown risks for use of MOV in pregnant or lactating individuals and pediatric patients," said the FDA. 

In addition, the latest findings on the oral Merck pill showed a lower efficacy rate than previously reported. Back in October, the company said that the drug was able to reduce hospitalizations by 50% compared to a placebo. However, the latest data demonstrate only a 30% ability. 

Molnupirvair works by interfering with the SARS-CoV-2 virus' ability to self-replicate and can function as an oral therapy. Current treatments for COVID-19 involve the use of injected or infused monoclonal antibodies, which are costly to produce and acquire. An oral drug would have been the cost-effective answer to getting protection from the virus. 

Still, the FDA's Antimicrobial Drugs Advisory Committee voted 13-0 to recommend Merck's COVID-19 drug for an Emergency Use Authorization, noting that while the rate of protection from severe disease or death was lower than previously expected, 30% is still a significant figure — at least for those who are not pregnant. The oral capsule is recommended to be taken by sets of four, two times a day for five days from the start of symptoms.