Human Safety, Tolerability, and Pharmacokinetics of Molnupiravir, a Novel Broad-Spectrum Oral Antiviral Agent with Activity against SARS-CoV-2

Molnupiravir (EIDD-2801/MK-4482), the prodrug of the active antiviral ribonucleoside analog beta-D-N4-hydroxycytidine (NHC; EIDD-1931), has activity against a number of RNA viruses, including severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), and seasonal and pandemic influenza viruses. Single and multiple doses of molnupiravir were evaluated in this first-inhuman, phase 1, randomized, double-blind, placebo-controlled study in healthy volunteers, which included evaluation of the effect of food on pharmacokinetics. EIDD-1931 appeared rapidly in plasma, with a median time of maximum observed concentration of 1.00 to 1.75 h, and declined with a geometric half-life of approximately 1 h, with a slower elimination phase apparent following multiple doses or higher single doses (7.1 h at the highest dose tested). Mean maximum observed concentration (C-max) and area under the plasma concentration versus time curve (AUC) increased in a dose-proportional manner, and there was no accumulation following multiple doses. When administered in a fed state, there was a decrease in the rate of absorption, but no decrease in overall exposure. Molnupiravir was well tolerated. Fewer than half of the subjects reported an adverse event, the incidence of adverse events was higher following administration of placebo, and 93.3% of adverse events were mild. One subject discontinued early due to rash. There were no serious adverse events, and there were no clinically significant findings in clinical laboratory, vital signs, or electrocardiography. Plasma exposures exceeded expected efficacious doses based on scaling from animal models; therefore, dose escalations were discontinued before a maximum tolerated dose was reached.