Extension Study of Herombopag for Pediatric Patients With Chronic Immune Thrombocytopenia

Inclusion Criteria: 1. Subjects who have completed PartB of HR-TPO-ITP-III-PED clinical trial and have achieved platelet response. 2. Subjects who have signed the informed consent for the extended study. 3. Subjects with potential fertility（e.g. women who have menarche or men who have sperm loss) should agree to use effective contraception during their participation in the extended study and within 28 days after their last dose. 4. Subjects who have completed end-of-treatment visits in the original study. Exclusion Criteria: 1. Any unstable condition or condition that may compromise the safety of the subject. 2. Patients with new myelofibrosis were examined in the original clinical trial exit group. 3. The original clinical trial cohort examined evidence of new cataract or existing cataract progression, and the study considered it unsuitable to enroll in this extension. 4. Patients with uncontrolled bleeding after standard treatment. 5. Any previous occurrence of arterial or venous thrombosis (transient ischemic attack,myocardial infarction ,deep venous thrombus, or pulmonary embolism ),or clinical symptoms and history suggest thrombus susceptibility. 6. Any other circumstances that the investigator considers likely to cause the subject to be unable to complete the study or to present a significant risk to the subject.