Evaluate the Efficacy and Safety of Orelabrutinib in Adult Patients With Chronic Primary Immune Thrombocytopenia

Inclusion Criteria: 1. Subjects have had a detailed understanding of the nature, significance, possible benefits, possible inconveniences, and potential risks of the trial, understood the study procedures, and voluntarily signed a written ICF before the study. 2. Males or females aged from 18 to 80 years (including the marginal values). 3. With a body weight of ≥ 35 kg at screening. 4. In accordance with the diagnosis of chronic (≥ 12 months) ITP 5. Patients who have previously received at least one anti-ITP first-line standard treatment (glucocorticoids and/or intravenous immunoglobulin) cannot maintain efficacy, or relapse, or cannot tolerate standard treatment, or have insufficient response. 6. Females of childbearing potential must use an effective method of contraception during the screening period, throughout the entire trial, and for 90 days after the last administration of the investigational medicinal product (IMP). Exclusion Criteria: 1. Severe hemorrhage occurred within 4 weeks prior to screening. 2. Subjects suffered from severe ITP at screening and were not eligible for participation in this study as judged by the investigator. 3. Subjects had autoimmune systemic diseases other than ITP unless they would not affect the evaluation of the study results in the judgment of the investigator and sponsor medical monitor. 4. Subjects had multiple immune hemocytopenia. 5. Subjects had inherited thrombocytopenia or secondary ITP. 6. Subjects had a history of arterial or venous thromboembolism within 6 months prior to screening. 7. Received prohibited medications within protocol-specified period before the first dose. 8. Received blood transfusion (including platelet transfusion) within 2 weeks prior to the first dose of the investigational drug. 9. Participated in another study of the investigational drug (and/or investigational device) within 30 days or within 5 half-lives prior to screening (whichever is longer), or is currently participating in another study of the investigational drug (and /or investigational device). 10. The last administration of strong CYP3A inhibitors or strong CYP3A inducers (include food, western medicine, traditional Chinese medicine) is within 14 days (or 5 half-lives, whichever is longer) prior to the first dose, or planned to take a drug or food with a strong inhibition or induction of CYP3A during the study period. 11. Received a major surgery (including splenectomy) or trauma (except biopsy) within 28 days prior to the first dose of the investigational drug, or expected to receive a major surgery during the study treatment period. 12. Received splenectomy and had a prior history of overwhelming post-splenectomy infection (OPSI). 13. Had a history of alcohol or drug abuse currently or within the past 1 year, excepting nicotine and caffeine. 14. Received a COVID-19 vaccine, live vaccine, or live-attenuated vaccine within 1 month prior to screening or during the screening period. 15. Previous exposure to BTK inhibitors. 16. Laboratory results did not meet protocol requirements. 17. Pregnant or lactating women. 18. Subjects whose blood cannot be collected, or who had contraindications for blood collection. 19. Other conditions that were not appropriate for participation in the trial as considered by the investigators.