The main purpose of this extended study is to enable subjects who are currently receiving the PartB experimental drug in the HR-TPO-ITP-III-PED clinical trial .To continue receiving the experimental drug after the completion of the clinical trial if they benefit from the treatment at the end of the clinical trial.Until the study physician determines that the subject has failed treatment or that the subject can no longer benefit from treatment or extends the study treatment for 6 months.In addition, the secondary purpose of this extended study was to observe the long-term efficacy and safety of tripodal in children and adolescents.

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.