The catastrophic SARS-CoV-2 outbreak of 2019 has resulted in 235 million confirmed cases of COVID-19 causing >5.2 million deaths globally as of December 2021. SARS-CoV-2 is a highly infectious, RNA beta-coronavirus that can cause life-threatening viral pneumonia in the most serious cases^[1]. Although effective COVID-19 vaccines have been developed within unprecedented timelines, a large number of people are either unable due to preexisting medical conditions or unwilling to be vaccinated, and global access challenges remain. Oral SARS-CoV-2-specific therapeutics are urgently needed to prevent more severe disease, hospitalization, and death. In December 2021, Pfrizer's COVID-19 new drug Paxlovid and Merck's COVID-19 new drug Molnupiravir were received emergency authorization from U.S. FDA for use in high-risk patients. And in January 2022, SHIONOGI's 3CLpro inhibitor S-217622 was disclosed with its structure and positive clinical results^[2-7].

A series of building blocks will be used as molecular fragments
in the design of COVID-19 new drugs