On Oct. 11, 2021, scientists at Washington University School of Medicine in St. Louis announced they had developed a chemical compound that interferes with a key feature of many viruses that allows the viruses to invade human cells. The compound, called MM3122, was studied in cells and mice and holds promise as a new way to prevent infection or reduce the severity of COVID-19 if given early in the course of an infection, according to the researchers. The study was published in the Proceedings of the National Academy of Sciences.

The study was published in the Proceedings of the National Academy of Sciences.

The new drug compound potently blocks TMPRSS2 and another related protein called matriptase, which are found on the surface of the lung and other cells. Many viruses — including SARS-CoV-2, which causes COVID-19, as well as other coronaviruses and influenza — depend on these proteins to infect cells and spread throughout the lung. After the virus latches onto a cell in the airway epithelia, the human protein TMPRSS2 cuts the virus’s spike protein, activating the spike protein to mediate fusion of the viral and cellular membranes, initiating the process of infection. MM3122 is blocking the enzymatic activity of human protein TMPRSS2. When the enzyme is blocked, it perturbs the activation of the spike protein and suppresses membrane fusion.

Studying cells growing in the lab that were infected with SARS-CoV-2, MM3122 protected the cells from viral damage much better than remdesivir, a treatment already approved by the Food and Drug Administration for patients with COVID-19. An acute safety test in mice showed that large doses of the compound given for seven days did not cause any noticeable problems. The researchers also showed that the compound was as effective against the original Severe Acute Respiratory Syndrome coronavirus (SARS-CoV) and Middle Eastern Respiratory Syndrome coronavirus (MERS-CoV).