Potential Antiviral Agents for Coronaviruses: Compounds, Herbal Products, and Drug Targets

Coronaviruses (CoVs) may lead to lethal infections, but currently no effective antiviral therapeutics or vaccines are available. The pandemic of the deadly COVID-19 is a reminder that such coronaviruses can emerge at any time. Novel human coronaviruses (HCoVs) may lead to Acute Respiratory Distress Syndrome (ARDS) and renal failure. They are highly transmissible and can spread from person-to-person through close contact. Broad-spectrum antiviral drugs may lower the vulnerability of public health systems to the coronavirus pandemic. Experiences from SARS and MERS outbreaks have revealed the demands for drugs with pan-coronavirus antiviral activities. The potential antiviral agents include neutralizing antibodies and drugs targeting the coronaviral envelope protein. Vaccine platforms can be used to transport antigens and immunostimulatory cytokines to enable protective immunity. Some compounds have been found to inhibit the replication of SARS and Ebola viruses. These compounds may be useful for the development of broad-spectrum drugs against viruses. Medicinal herbs and extracts have potential anti-CoV effects. The herbal extracts may inhibit viral replication and suppress SARS-CoV protease activity. The antiviral effects of regular household products have been evaluated against SARS-CoV. Studies of SARS-CoV have focused on the accessory proteins, host cell entry, nucleocapsid protein, spike protein, and viral proteases. The SARS-CoV and MERS-CoV have altered signaling pathways for evading early innate immune responses. Understanding of these mechanisms is critical for finding drugs for the treatment of COVID-19, SARS, MERS, and other coronavirus diseases.