This is a randomized, double blinded, placebo-controlled phase Ib clinical trial in adult patients with immune thrombocytopenia. Cross-over treatment will be allowed during the study.

Approximate 51 to 60 patients will be enrolled in dose escalation (3 cohorts, 8-20 subjects each with the ratio of 3:1 vs Placebo) .

Inclusion Criteria:

1. Signed informed consent form

2. 18~75 years old male of female

3. Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1

4. Diagnosed immune thrombocytopenia before randomization with platelet decrease for more than 6 months.

5. Patients with refractory or relapsed ITP who have been treated with 1st line anti-ITP regimen or have experienced splenectomy.

6. Relative stable disease with World Health Organization (WHO) bleeding score of 0-1 and no rescue treatment needed within 2 weeks based on investigator's judgment.

7. Laboratory tests meet the following conditions：

   • During screening stage, twice PLT<30x10^9/L(exceed 24 hours)
   • Hb≥90g/L(if iron-deficiency anemia,Hb>80g/L),WBC>2.5x10^9/L, NEU>1.8x10^9/L
   • Crea≤1.5xULN and CCR≥50mL/min
   • TBIL、ALT、AST≤1.5xULN
   • Amylase、lipase\