The Safety, Tolerability, Pharmacokinetics, and Preliminary Efficacy of HMPL-523 in Adult Subjects With Immune Thrombocytopenia (ITP)

This study is a Phase 1b, open-label, multicenter, single-arm study to evaluate the safety, tolerability, and preliminary efficacy of HMPL-523 in adult subjects with primary ITP diagnosed at least 3 months prior to enrollment or randomization. In the dose escalation stage (Part 1), subjects will receive one of 3 dose levels of HMPL-523 to determine the recommended dose of HMPL-523 for the randomized dose optimization- stage (Part 2). At the end of Part 1, 2 dose levels will be selected to be used in the dose-optimization stage (Part 2) of the study. In Part 2 of the study, subjects will be randomized in a 1:1 ratio between the 2 dose levels to better understand the exposure/efficacy/toxicity relationship. At the end of Part 2, the Recommended Phase 3 dose (RP3D) of HMPL-523 will be determined based on the safety, efficacy and PK data.