Sponsor decision

This is an open-label, multicenter study to evaluate the safety, tolerability, and efficacy of HMPL-523 in adult subjects with 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.

Inclusion Criteria:

Subjects may be enrolled in this study only if they satisfy all the following criteria:

1. Adult male or female subjects ≥18 years of age
2. Diagnosis of ITP, with a duration of disease of at least 3 months prior to randomization or enrollment
3. Intolerance or insufficient response or recurrence after at least 1 prior ITP treatment (excluding splenectomy)
4. Response (defined as achieved a platelet count ≥50 × 109/L) to at least 1 prior ITP therapy (including splenectomy)
5. Adequate hematologic, hepatic and renal function

Exclusion Criteria:

Subjects are not eligible for enrollment into this study if any one of the following criteria are met:

1. Evidence of the presence of secondary causes of ITP
2. Clinically serious hemorrhage requiring immediate adjustment of platelets
3. Known history of vital organ transplantation or hematopoietic stem-cell transplantation or chimeric antigen receptor T-cells (CAR-T) therapy
4. Splenectomy within 12 weeks prior to enrollment
5. Presence of active malignancy unless deemed cured by adequate treatment.
6. History of serious cardiovascular disease corrected QT interval (QTcF) ≥450 ms
7. Uncontrolled hypertension
8. Being unsuitable to participate in this study as considered by investigators