Anti-CD38 Antibody Treating Pediatric Primary Immune Thrombocytopenia (ITP)

Inclusion Criteria: * Age 6 years and above, male or female * Conform to the diagnostic criteria of immune Thrombocytopenia (ITP) * Diagnosis of ITP ≥3 months, and with a platelet count of \<30 X 10\^9/L measured within 2 days prior to inclusion * Failure to achieve response or relapse after corticosteroid therapy, and at least one second-line therapy including rituximab or TPORAs. * The previous emergency treatment of ITP (e.g. methylprednisolone, platelet transfusion, IVIG transfusion) must be completed at least 2 weeks before the first administration * Signed and dated written informed consent * With normal hepatic and renal functions * ECOG physical state score ≤ 2 points * Cardiac function of the New York Society of Cardiac Function ≤ 2 * Patients receiving maintenance treatment (including corticosteroids (less than or equal to 0.5mg/kg prednisone), TPO receptor agonists, etc.) must have a stable dose at least 4 weeks before the first administration, and azathioprine, danazol, cyclosporin A, tacrolimus, sirolimus, etc. must be stopped at least 4 weeks before the first administration; The end of rituximab treatment was\>3 months；More than 6 months after splenectomy. March 26,2024 After approval by the Ethics Committee，age of subjects has been modified to 6 years and above upon enrollment. Approval Number: IIT2023072-EC-2. Exclusion Criteria: * Allergy to daratumumab or its excipients, or prior treatment with daratumumab that was refractory or achieved a response lasting \<6 months； * 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; * Patients 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.