Iscartrelvir Hydrochloride Tablets （trade name: Mprosevir）is a Class 1 innovative drug jointly developed by Westlake University, Westlake  Laboratory, and Westlake Pharmaceuticals for the treatment of adults with mild to moderate COVID-19. On July 29, 2026, it was conditionally approved for marketing by the National Medical Products Administration (NMPA).

Mprosevir® is an independently developed small-molecule oral drug with a novel core scaffold. It is the world’s first successful example of an original drug derived from DEL (DNA-encoded library) technology.

Mprosevir® is an inhibitor of 3CLpro, the main protease of SARS-CoV-2. 3CLpro is indispensable for the self-replication and assembly of the virus. By competitively binding to the substrate-binding pocket of 3CLpro, Mprosevir® prevents cleavage of the polyprotein precursor, thereby inhibiting SARS-CoV-2 replication.

As Mprosevir® binds to its target non-covalently, it is associated with a low risk of off-target effects and a favorable safety profile. In preclinical and clinical studies, Mprosevir® has demonstrated significant efficacy and good safety. In addition, Mprosevir® is used as a monotherapy and does not require co-administration with ritonavir, offering a new treatment option for patients with underlying medical conditions.