Safety, Pharmacokinetics and Preliminary Efficacy of HMPL-523 in Adult Patients with Primary Immune Thrombocytopenia: A Randomized, Double-Blind and Placebo-Controlled Phase 1b Study

Background: Primary immune thrombocytopenia (ITP) is characterized by increased platelet destruction and impaired platelet production, resulting in decreased platelet counts and increased bleeding risk. Spleen Tyrosine Kinase (Syk) plays a pivotal role in the regulation of downstream signals in immune receptors, including B cell receptors (BCRs) and has been implicated in autoantibody production. On the other hand, all activating Fc receptors signal via Syk, which has roles in cellular proliferation, differentiation, survival, immune regulation, and cytoskeletal rearrangements during phagocytosis. This randomized, double-blind, placebo-controlled phase 1b study (NCT03951623) aimed to assess the safety, pharmacokinetics (PK), determine the recommended phase 2 dose (RP2D) and evaluate preliminary efficacy of HMPL-523, a novel, potent and highly selective Syk inhibitor, in patients with ITP.