Autoimmune Cytopenias

At the 63rd annual meeting of the American Society of Hematology, a multicenter team of investigators from China presented results of a phase 1b efficacy and safety study (abstract 16) of HMPL-523, a novel and highly potent spleen tyrosine kinase (Syk) inhibitor, in patients with immune thrombocytopenia (ITP). This randomized, double-blind, placebo-controlled, dose-finding study enrolled patients with relapsed/refractory ITP and platelet counts below 30×109/L. The study had dose expansion (DES) and dose escalation (DEX) stages. A total of 33 patients were enrolled in the DES portion of the study at 100 to 400 mg; 300-mg daily was identified as the recommended phase 2 dose. An additional 12 patients were enrolled in the DEX stage at 300 mg QD. During an 8-week double-blind treatment (8w-DB) period, the overall response rate (ORR) was 3 (50.0%), 2 (33.3%), 11 (68.8%) and 2 (33.3%) in the 100- to 400-mg dose cohorts, respectively, compared with 1 (9.1%) in the placebo group. The durable response rate (DRR) at 300 mg was 5 (31.3%), compared with 1 (9.1%) in the placebo group. For all patients enrolled in the 300-mg cohort who received at least 1 dose of HMPL-523 (n=20), including in both the 8w-DB period and the 16-week open-label treatment period that followed, the ORR was 80%; the DRR was 27.8% among evaluable patients (those who received HMPL-523 treatment and completed 6 or more scheduled visits or discontinued during HMPL-523 treatment; n=18). The authors noted that efficacy of HMPL-523 in primary ITP will be evaluated further in a randomized phase 3 study.