A patent review of Mpro protease inhibitors for the treatment of COVID-19 infections (2020 – present)

INTRODUCTION: The SARS-CoV-2 main protease (Mpro, also known as 3CLpro or nsp5) is essential for viral replication. As there are no close human homologs, it represents an attractive and specific target for antiviral therapy against COVID-19. Its well-defined active site and conserved substrate specificity have enabled structure-guided drug design with high precision. AREAS COVERED: This review examines the patent landscape for small-molecule inhibitors of SARS-CoV-2 Mpro published between 2020 and early 2025. Compounds were grouped by scaffold type and mechanism of action, covering covalent and non-covalent inhibitors, orthosteric and allosteric binders and unique modalities such as PROTACs. Clinically advanced agents including nirmatrelvir, ensitrelvir, simnotrelvir, zevotrelvir and leritrelvir are highlighted alongside structurally novel leads and broad-spectrum candidates. EXPERT OPINION: A number of Mpro inhibitors have progressed into preclinical and clinical stages, underscoring the rapid advancement in this field. The accumulation of structural knowledge, chemical diversity and mechanistic insight has laid a robust foundation for future antiviral development and may further enhance the utility of Mpro inhibitors against evolving coronaviruses.