Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Symptoms typically include fever, cough, headache, fatigue, difficulty breathing, and loss of smell and taste. SARS-CoV-2 is airborne, mainly from person to person through close contact and exhaled aerosols and respiratory droplets when speaking, breathing, or otherwise exhaling, and droplets from coughing and sneezing. It enters human cells by binding to angiotensin-converting enzyme 2 (ACE2), a membrane protein that regulates the renin-angiotensin system, a host factor targeted by the SARS-CoV-2 virus causing COVID-19. In addition, the virus can lead to leukocyte infiltration and increased vascular permeability. It also increased alveolar wall permeability and reduced pulmonary surfactant secretion through its effect on the ACE2 cell surface, which in turn causes most respiratory symptoms and eventually systemic inflammatory response syndrome.
Molnupiravir has antiviral activity against the influenza virus and multiple coronaviruses.
Molnupiravir, also known as EIDD-2801, is an orally bioavailable prodrug of the ribonucleoside analog EIDD-1931. It has broad-spectrum antiviral activity against the influenza virus and multiple coronaviruses, such as SARS-CoV-2, MERS-CoV, and SARS-CoV. It has the potential for research on COVID-19, and seasonal and pandemic influenza. In C57BL/6 mice infected with the SARS-CoV model, Molnupiravir (50-500 mg/kg; p.o.; every 12 hours for 3 days) is robustly antiviral and able to prevent SARS-CoV replication and disease. Moreover, it shows that significantly reduced or prevented weight loss. Besides, Molnupiravir (7 mg/kg; p.o.; twice daily for 3.5 days) significantly reduces shed virus load and duration of fever in Ca/09-infected female ferrets. And it shows that the Shed virus load and duration of fever were significantly reduced.
In conclusion, Molnupiravir, a prodrug of a synthetic nucleoside derivative N 4 -hydroxycytidine, exerts its antiviral effects by introducing replication errors during viral RNA replication.
 Mart Toots, et al. Sci Transl Med. 2019 Oct 23;11(515):eaax5866.
 Timothy P Sheahan, et al. Sci Transl Med. 2020 Apr 29;12(541):eabb5883.