Shares of Merck (MRK) are falling after the company provided an update on molnupiravir, its investigational oral antiviral medicine for Covid-19. Data are now available from all of the enrolled 1433 participants. In this study population, molnupiravir reduced the risk of hospitalization or death from 9.7% in the placebo group to 6.8% in the molnupiravir group, for an absolute risk reduction of 3.0% and a relative risk reduction of 30%. Nine deaths were reported in the placebo group, and one in the molnupiravir group. The adverse event profile for molnupiravir remained consistent with the profile reported at the planned interim analysis, Merck and partner Ridgeback Biotherapeutics said in a statement. The relative risk reduction of 30% is down from the 48% the companies reported previously for molnupiravir. Shares of Merck are down 4% to $78.73 in premarket trading following the data while Pfizer, which is also developing a Covid antiviral treatment, is up 6% to $54.10.