HUTCHMED (China) Limited announced that it has initiated a Phase III trial in China of HMPL-523, a novel, investigational spleen tyrosine kinase (?Syk?) inhibitor, in adult patients with primary immune thrombocytopenia (?ITP?), an autoimmune disorder that can lead to increased risk of bleeding. The first patient received their first dose on October 27, 2021. The study is a randomized, double blinded, placebo-controlled Phase III clinical trial evaluating the efficacy and safety of HMPL-523 in treating adult patients with ITP. The primary endpoint of the study is the durable response rate. Secondary and exploratory endpoints include overall response rate (ORR), incidence of treatment emergent adverse events, and patient quality of life improvement. Approximately 180 patients are expected to be enrolled. Additional details may be found at clinicaltrials.gov, using identifier NCT05029635. The rationale for this Phase III study is based on encouraging data from the Phase Ib study of HMPL-523 in adult patients with ITP. The safety, pharmacokinetics and preliminary efficacy data for the Phase Ib study are expected to be presented at the 63rdAmerican Society of Hematology (ASH) Annual Meeting in December 2021. About HMPL-523: HMPL-523 is a novel, investigational, selective small molecule inhibitor for oral administration targeting spleen tyrosine kinase, also known as Syk. Syk is a major component in B-cell receptor signaling and is an established target for the treatment of multiple subtypes of B-cell lymphomas and autoimmune disorders. HUTCHMED currently retains all rights to HMPL-523 worldwide. In addition to ITP, HMPL-523 is also being studied in indolent non-Hodgkin?s lymphoma and multiple subtypes of B-cell malignancies in China, the U.S. and Europe (NCT02857998; NCT03779113). A trial to study HMPL-523 in patients with warm autoimmune hemolytic anemia (wAIHA), another autoimmune disorder, is also planned.