Development of Peptidomimetic PROTACs as Potential Degraders of 3-Chymotrypsin-like Protease of SARS-CoV-2

3CL protease (3CL^pro), a key enzyme of SARS-CoV-2 replication, is one of the most selective targets of antivirals, as no homologous protease has been recognized in the human body. As proteolysis-targeting chimeras (PROTACs) are superior to traditional inhibitors, based on the reported cereblon (CRBN) ligands thalidomide and lenalidomide, 3CL^pro ligands of peptidomimetic inhibitors, and suitable linkers, we aimed to develop novel PROTACs that may trigger efficient intracellular 3CL^pro degradation through a balance of hydrophilicity and lipophilicity. In brief, we designed and synthesized 5 PROTAC molecules. The 3CL^pro degradation efficiency of the PROTACs was assayed in stable SARS-CoV-2 3CL^pro expression HEK293 cell models and evaluated by Western blot. All compounds showed prominent 3CL^pro degradation activity with tolerable HEK293 cytotoxicity. The most prominent PROTAC compounds, <b>15</b> and <b>16</b>, have DC₅₀ values of approximately 1 µM, and D_max of 89.3% and 75% respectively, indicating good potential for further application.