On 29 July 2026, the Class 1 innovative drug iscartrelvir hydrochloride tablets (trade name: Mprosevir®), jointly developed by Westlake University, Westlake Laboratory and Westlake Pharmaceuticals, was approved by the National Medical Products Administration for marketing. Mprosevir® is indicated for adults with mild to moderate COVID-19. It is a self-developed oral small molecule with an entirely new scaffold, offering patients a treatment with a novel mechanism and giving the global response to major public-health challenges a new option developed in China.
Mprosevir® is an inhibitor of the SARS-CoV-2 main protease, 3CLpro, which is indispensable for viral replication and assembly. By binding competitively to the substrate pocket of 3CLpro, Mprosevir® prevents cleavage of the polyprotein precursor and thereby blocks replication. Binding to the target is non-covalent, which keeps the risk of off-target effects low and the safety margin wide. In preclinical and clinical studies Mprosevir® showed pronounced efficacy and good safety, and it is a single agent that does not require ritonavir boosting — an advantage for patients with underlying conditions.
The approval rests mainly on a multicentre, randomised, double-blind, placebo-controlled Phase 3 study of efficacy and safety in patients with mild to moderate COVID-19. Twenty-eight hospitals across China took part and 1,350 participants were enrolled. The primary efficacy endpoint was the time from first dose to sustained clinical recovery within 28 days of treatment.
The study was conducted during the routine-management phase of the pandemic and used a positive antigen test as the inclusion criterion, which is closer to real-world diagnosis. Most participants had been infected two or more times, so their natural recovery time was relatively short. Even under these more demanding conditions the data confirmed a significant effect, and the Phase 3 safety analysis showed adverse-event rates broadly comparable with placebo, with good safety and tolerability.
The novel molecular scaffold of Mprosevir® came from DNA-encoded library (DEL) screening at the source. Mprosevir® is the first original small molecule anywhere to originate from DEL technology and reach the market, demonstrating that combining AI with high-throughput DEL screening is an efficient and feasible discovery strategy. With differentiation in molecular design, clinical efficacy and safety, Mprosevir® offers a new treatment option for patients with COVID-19, particularly those at high risk.
Hongtao Yu, co-founder of Westlake Pharmaceuticals, said: “As a technology transfer company of Westlake University, Westlake Pharmaceuticals has always been dedicated to discovering original medicines for major human diseases. Mprosevir® is the result of combining frontier technologies from several fields into genuine original innovation. Its approval gives patients a new treatment option, and gives us a strategic reserve for responding to major public-health challenges. My sincere thanks go to the governments and regulators who guided us, to our partners for their support, and to the team for their persistence. We will keep working on original drug discovery so that innovation reaches patients sooner.”