The purpose of this study is to evaluate the efficacy and safety of rhTPO in the maintenance treatment of ITP, to explore the appropriate dosing interval of the maintenance treatment of rhTPO .

The eligible subjects with ITP firstly will receive a pre-treatment of rhTPO 300 IU/Kg once daily up to 14 days. The subjects with two consecutive platelet counts above 50×10^9/L in the pre-treatment period will begin to receive maintenance treatment of rhTPO 300 IU/Kg for 12 weeks. In the period of maintenance treatment, starting dosing interval of rhTPO is every other day followed by the interval adjustments for keeping platelet counts between 30 ×10^9/L～100 ×10^9/L. Subsequently, subjects will stop treatment of rhTPO and be followed up for 4 weeks after maintenance treatment.

Platelet count, bleeding and other symptoms will be evaluated before and after treatment.

Platelet transfusion will be administered to subjects with active bleeding symptoms.

Toxicity will be monitored continuously during the entire study. Safety will be assessed by adverse events and laboratory tests.

Inclusion Criteria:

• Meeting the diagnostic criteria for immune thrombocytopenia (idiopathic thrombocytopenic purpura).
• Subject with resistance to or relapse after glucocorticoid in the treatment of ITP, not accepts splenectomy, or subject with ineffective or relapse after surgical splenectomy.
• Two consecutive platelet counts (not in the same day) < 30×10^9/L.
• Subject is willing and able to provide written informed consent.

Exclusion Criteria:

• Pregnancy or breast feeding.

• Having a medical history of thrombosis.

• Significant abnormal cardio-pulmonary function.

• Abnormal liver and kidney function:

  • a serum creatinine concentration≥ 176.8µmol/l (1.5mg/dl);
  • a serum aminotransferase concentration: more than 2.0 times the upper limit of the normal range.
  • a serum bilirubin concentration: more than 2.0 times the upper limit of the normal range.

• Synchronous tumor.

• Cannot adopt adequate contraceptive precautions during the course of the study.

• Any other treatment drugs for ITP are being taken (except the duration of reducing glucocorticoid dosage as ineffective treatment ).

• Any other situation that is not suitable for participating in the trial according to the judgment of the investigator .