Inclusion Criteria:
* Age ≥18 years, male or female.
* Before enrollment, the subjects have been clinically diagnosed with primary immune thrombocytopenia for no less than three months according to the American Society of Hematology guidelines 2011 Evidence-Based Practice Guideline (Neunert et al. 2011) or the International Consensus Report for the Investigation and Management of Primary Immune Thrombocytopenia (Provan et al. 2010), as applicable locally.
* Subjects with a platelet count of \<30×10\^9/L within the 48 hours prior to the first dose of the study drug;The platelet count of at least two separate assessments (at least 1 week apart) \<30×10\^9/L during the screening visit.
* Patients have failed glucocorticoid therapy (either due to inefficacy, efficacy could not be maintained, or relapse).
* Previous emergency treatment for ITP (e.g., methylprednisolone, platelet, gamma globulin infusion) must have been completed at least 2 weeks before the first dose.
* Hepatic and renal function (e.g., alanine aminotransferase, aspartate aminotransferase, total bilirubin, serum creatinine) \<1.5 times the upper limit of normal (ULN).
* ECOG performance status score of ≤2.
* Cardiac function: New York Heart Association (NYHA) class ≤2.
* Enrollment of subjects receiving maintenance therapy is permitted, including glucocorticoids (≤0.5 mg/kg of prednisone or equivalent) or TPO receptor agonists, but the concomitant medication must have been stable for a minimum of 4 weeks prior to the initial infusion of the study drug; Azathioprine, danazol, cyclosporine A, tacrolimus, sirolimus, etc. must be stopped at least 4 weeks before the first dose; CD20 monoclonal antibody such as rituximab must have been stopped for more than 6 months; the interval between splenectomy and first administration need to be more than 6 months.
* For fertile female patients, a negative pregnancy test result is required. Fertile female and male patients must use effective contraception separately during the study and for 90 days after the cessation of study drug treatment.
* Subjects comprehensively understand and can adhere to the study protocol requirements and willingly signed the informed consent form.
Exclusion Criteria:
* Uncontrollable primary diseases of important organs, such as malignant tumors, liver failure, heart failure, renal failure and other diseases.
* HIV positive.
* Accompanied by uncontrollable active infection, including hepatitis B, hepatitis C, cytomegalovirus, EB virus and syphilis positive.
* Accompanied by extensive and severe bleeding, such as hemoptysis, upper gastrointestinal hemorrhage, intracranial hemorrhage, etc..
* At present, there are heart diseases, arrhythmias that need treatment or hypertension that researchers judge is poorly controlled.
* Patients with thrombotic diseases such as pulmonary embolism, thrombosis and atherosclerosis.
* Those who have received allogeneic stem cell transplantation or organ transplantation in the past.
* atients with mental disorders who cannot normally obtain informed consent and conduct trials and follow-up.
* Patients whose toxic symptoms caused by pre-trial treatment have not disappeared.
* Other serious diseases that may limit the subject's participation in this test (such as diabetes; Severe cardiac insufficiency; Myocardial obstruction or unstable arrhythmia or unstable angina pectoris in recent 6 months; Gastric ulcer, etc.).
* Patients with septicemia or other irregular severe bleeding.
* Patients taking antiplatelet drugs at the same time.
* Pregnant women, suspected pregnancies (positive pregnancy test for human chorionic gonadotropin in urine at screening) and lactating patients.
* Subjects with a known allergy to medications were used in the trial or excipients.
* Any other conditions unsuitable for participation in this study, as assessed by the investigator.
