BTK participates in a variety of signal transduction of innate and adaptive immunity, and has an important role in cell proliferation, differentiation and apoptosis. The impact of BTK inhibitors on hematological malignancies and autoimmune diseases has been well studied. This project was undertaking by Qilu Hospital of Shandong University in China. In order to report the efficacy and safety of the selective BTK inhibitor Orelabrutinib in the management of refractory ITP.

The investigators are undertaking a prospective, open-lable, multicentre trial of 40 refractory ITP adult patients in China. Eligible participants will receive Orelabrutinib in 50 mg po. qd, every 4 weeks for one cycle and it will be given 3 cycles. For non-responders who were well tolerated at 12 weeks of follow-up, the treatment could be extended to 6 cycles. The treatment will be discontinued after 6 months without blood index reaction. In order to report the efficacy and safety of Orelabrutinib in the management of refractory ITP, platelet count, bleeding and other symptoms will be evaluated before and after treatments. Adverse events are also recorded throughout the study.

Inclusion Criteria:

• Meet the diagnostic criteria for primary immune thrombocytopenia
• To show a platelet count < 30 * 10^9/L, or with bleeding manifestations, or both
• Willing and able to sign written informed consent
• Meet the diagnostic criteria of refractory ITP according to Chinese guidelines

Exclusion Criteria:

• Secondary thrombocytopenia
• severe immune-deficiency or history of primary immunodeficiency
• active or previous malignancy
• HIV virus infection, tuberculosis, or other active infection (sepsis, pneumonia, or abscess)
• pregnancy or lactation
• diabetes
• hypertension
• cardiovascular diseases
• severe liver or kidney function impairment
• psychosis
• osteoporosis
• inflammatory bowel disease or gastric disease
• arterial or venous thromboembolism within the 6 months before screening or patients who required anticoagulant treatment
• an organ or haematopoietic stem-cell transplantation
• neutrophil count of less than 1500 cells per mm³; glycosylated haemoglobin less than 8%; partial thromboplastin time 1∙5 times or less the upper limit of normal (ULN)
• clinical electrocardiogram changes
• neoplastic disease within the past 5 years
• corrected QT interval greater than 450 ms for men and greater than 470 ms for women;
• substance misuse within the previous 12 months; and those who could not adhere to the protocol or were planning to have a surgical procedure in 6 months.