US federal health regulators say an experimental Covid-19 pill from Merck is effective but will seek input from outside experts on risks of birth defects and other problems during pregnancy. The Food and Drug Administration (FDA) posted its analysis of the pill before a public meeting next week where academic and other experts will weigh in. The agency isn’t required to follow the group’s advice. FDA scientists said their review had identified potential risks including possible toxicity and birth defects. Given those risks, the FDA will ask advisers if the drug should never be given during pregnancy or could be made available in some cases. Under that scenario, the FDA said, the drug would carry warnings about risks during pregnancy but doctors would still have the option to prescribe it if benefits could outweigh risks. The FDA said Merck agreed the drug would not be used in children. Additionally, the FDA flagged a concern that Merck’s drug led to small changes in the coronavirus’ signature spike protein, which it uses to penetrate human cells. Theoretically, the FDA cautioned, those changes could lead to dangerous new variants. Regulators also noted that Merck collected far less safety data than was gathered for other Covid-19 therapies. The FDA will ask its independent advisers to discuss all those issues and then vote on whether the drug’s overall benefits outweigh its risks. All Covid-19 drugs authorised by the FDA require an injection or IV and can only be given by health professionals. If authorized, Merck’s drug would be the first US patients could take at home. It is authorized for emergency use in the UK. The FDA meeting will be the first time US regulators have publicly reviewed a new drug for Covid-19, reflecting intense interest in a pill that could be used by millions. The drug, molnupiravir, has been shown to significantly cut hospitalizations and deaths among people with mild to moderate coronavirus infections. Merck’s drug uses a novel approach, inserting tiny mutations into the coronavirus’s genetic code to the point it can’t reproduce. That has raised concerns that in rare cases the drug could cause birth defects or tumors. Pregnant women were excluded from Merck’s study. Women and men in the study were instructed to use contraception or abstain from sex. Merck says results from two studies in rodents show “molnupiravir does not cause mutations or damage to DNA in these animal models”. The company said rodents received higher doses for longer periods of time than humans who will take the drug. FDA reviewers also confirmed previously reported interim results from Merck that the pill cut hospitalization and death by about half among patients with early symptoms of Covid-19 who faced increased risk due to health problems. However, on Friday Merck announced updated results from the same study that showed a smaller benefit from the drug. Among more than 1,400 adults in a company study, molnupiravir reduced the combined risk of hospitalization and death by 30%, less than the 50% initially reported from incomplete results. Nearly 7% of patients who received Merck’s drug within five days of Covid-19 symptoms ended up in the hospital. One died. That compared to 10% of patients hospitalized who took a placebo and nine deaths.