Merck Slumps on Covid Pill’s Lower Efficacy, FDA Scrutiny (1)

Merck & Co. shares sank after new data showed its Covid-19 pill was less effective than previously reported and U.S. regulators raised concerns about its safety and long-term effectiveness.

Merck’s latest trial results, reported Friday from a larger population than its initial study, show that its pill reduced the risk of hospitalization or death among adults with mild to moderate disease by 30%. That was less than a previous estimate of 48%.

Staff at the Food and Drug Administration, meanwhile, called the pill, molnupiravir, effective for individuals at increased risk for severe disease. But they raised questions about whether ...