The project was undertaking by Qilu Hospital of Shandong University and other well-known hospitals in China. Aims at evaluating effectiveness and safety of avatrombopag in the treatment of primary immune thrombocytopenia.

The investigators are undertakingSingle-arm, multi-Centre, Observational study of 400 Patients with primary immune thrombocytopenia (ITP) from Qilu Hospital of Shandong University and other well-known hospitals in China. ITP patients will be given one tablet (20 mg) of avatrombopag daily.If the platelet count is higher than 150×10^9/L, the dose should be reduced. Prolonged dosing intervals or a combination of reduced daily dose are preferred.If the drug was taken for ≥1 week and the platelet count was still less than 30×10^9/L, the dosage should be increased. The maximum dose is 40 mg daily. Aplatelet count,AE, laboratory parameters, ECG, vital signs and other symptoms will be evaluated before and after treatment. Adverse events will be recorded throughout the study.

Inclusion Criteria:

1. Aged 18+ years, male or female;

2. Ever been diagnosed as ITP patients. The diagnostic criteria comply with the "Chinese Guidelines for the Diagnosis and Treatment of Adult Primary Immune Thrombocytopenia (2020 Edition)"

   1. At least 2 consecutive blood tests showed a decrease in platelet count; no obvious abnormality in the morphology of blood cells by peripheral blood smear microscopy.
   2. Spleen is generally not enlarged.
   3. Bone marrow examination: the morphological characteristics of bone marrow cells in ITP patients were increased or normal megakaryocytes with maturation disorders.
   4. Other secondary thrombocytopenia must be excluded: autoimmune diseases, thyroid disease, lymphoproliferative disorders, myelodysplastic syndrome (MDS), aplastic anemia (AA), various malignant hematologic diseases, tumor infiltration, Chronic liver disease, hypersplenism, common variant immunodeficiency disease (CVID), infection, vaccination causing secondary thrombocytopenia; Thrombocytopenia due to depletion; Drug induced thrombocytopenia; Alloimmune thrombocytopenia; Thrombocytopenia during pregnancy; Congenital thrombocytopenia and pseudo-thrombocytopenia;

3. ECOG general status score ≤ 2;

4. Platelet count < 30×10^9/L；platelet count ≥< 30×10^9/L accompanied by active bleeding; If the platelet count is around 30×10^9/L and no active bleeding, a second examination must be performed to further confirm the platelet count.

5. Voluntarily signed the informed consent.

6. Any other circumstances that the investigator considers appropriate for the patient to participate in the study.

Exclusion Criteria:

1. Patients with secondary thrombocytopenia.
2. Currently receiving other TPO-RAs, rhIL-11 and rhTPO treatment, and subjects are unwilling to switch to avatrombopag treatment.
3. Patients with severe insufficiency of heart, lung, liver and kidney.
4. Pregnant or breast-feeding, or contraceptive measures cannot be taken during the trial.
5. Subjects participated in clinical studies of other investigational drugs or devices within 30 days prior to screening.
6. Having a history of psychotropic drug abuse and unable to quit or having mental disorders.
7. Having significant factors that affect the absorption of oral drugs, such as inability to swallow, chronic diarrhea and intestinal obstruction, etc.
8. Subject is allergic to avatrombopag or any of its excipients;
9. Any other circumstances that the investigator considers inappropriate for the patient to participate in the study.

1. Aged 18+ years, male or female;
2. Ever been diagnosed as ITP patients. The diagnostic criteria comply with the "Chinese Guidelines for the Diagnosis and Treatment of Adult Primary Immune Thrombocytopenia (2020 Edition)"