This project was undertaken to evaluate the efficacy and safety of BTK inhibitor Zanubrutinib for the secondary treatment of adults with primary immune thrombocytopenia (ITP).

The investigators are undertaking a prospective trial of 10 adults with ITP in China. Zanubrutinib is administered as 80 mg po. qd for 6 weeks. Platelet count, bleeding and other symptoms were evaluated before and after treatment. Adverse events are also recorded throughout the study.

Inclusion Criteria:

• Confirmed primary refractory ITP
• Platelet counts <30×10^9/L or with bleeding symptoms
• Willing and able to sign written informed consent

Exclusion Criteria:

• Secondary thrombocytopenia
• Received chemotherapy or anticoagulants or other drugs affecting the platelet counts within 6 months before the screening visit
• HIV infection or hepatitis B virus or hepatitis C virus infections
• Malignancy
• Severe medical condition (e.g., unstable angina, congestive heart failure, uncontrolled hypertension or cardiac arrhythmia)
• Nursing or pregnant patients
• Patients who are deemed unsuitable for the study by the investigator