Merck's latest trial data show its Covid pill is less effective

Merck & Co. said updated results showed its Covid-19 pill reduced the risk of hospitalization or death among adults with mild to moderate disease by 30%, less than a previous estimate and well below a rival treatment from Pfizer Inc. 

Shares of Merck slid 3.4% to $79.46 in pre-market trading, reversing earlier gains, while Pfizer rose 5.9%. 

Merck’s latest trial analysis includes data from all enrolled participants, the drugmaker said in a statement Friday. Nine deaths were reported in the placebo group, and one in the group receiving the treatment, called molnupiravir. 

The data will be at the center of a Tuesday panel discussion by U.S. Food and Drug Administration advisers regarding its use to treat Covid in high-risk patients. 

Merck sought U.S. authorization for molnupiravir, also called Lagevrio, in October after a late-stage study showed it cut the risk of hospitalization or death by around 50% in high-risk patients. Another drug, Pfizer’s Paxlovid, has been submitted for review for use in the same population after showing an 89% reduction. 

If authorized by regulators, the pills from Merck and Pfizer are likely to overtake infused drugs monoclonal antibodies from Regeneron Pharmaceuticals Inc. and Eli Lilly & Co. that are more expensive and harder to use.