Thrombopoietin receptor agonists (TPO-RAs) represent a highly effective and well-tolerated second-line ITP treatment that provides excellent responses.If there is cross-resistance between 2 drugs for the treatment of adult ITP is still unkonwn.The purpose of this study is to investigate the efficacy and safety of switching avatrombopag and rh-TPO in adults with ITP.

Thrombopoietin Receptor Agonists (TPO-RAs) are novel treatments for patients with chronic Primary Immune Thrombocytopenia (ITP). According to the findings of mechanism-based studies, rhTPO competes with endogenous TPO for binding to TPO-R while avatrombopag has an additive effect with endogenous TPO, indicating that the treatment mechanism and side-effect profiles could be somewhat different between these drugs. If there is cross-resistance between 2 drugs for the treatment of adult ITP is still no answer. The purpose of this study is to investigate the efficacy and safety of switching avatrombopag and rh-TPO in adults with ITP.This is a non-interventional study. Patients who fail previous steroids and receive rh-TPO and then switch to avatrombopag or vice versa will be enrolled. The reason for switch will be recorded. The efficacy, safety, and patient/physician preference will be assessed and compared between the two agents.

Inclusion Criteria:

1.18 years or older 2.Primary ITP 3.Failed initial glucocorticosteroid treatment, 4.Applying rhTPO or Eltrombopag as subsequent treatment 5.Switch from rh-TPO to eltrombopag or vice versa 6.Normal neutrophils 7.Available follow-up at least 6 weeks after switching

Exclusion Criteria:

1. HIV positive status, or active infection of HBV or HCV
2. Suffering from a serious or progressive disease, which, in the investigator's judgment, put the subject at undue risk for participation in this study (i.e. cancer or pre-cancer, immunocompromised, uncontrolled diabetes, epilepsy, severe cardio-cerebrovascular disease(s) (i.e. stroke, idiopathic aortic stenosis, aneurysm, hypertrophic obstructive cardiomyopathy, ischaemic heart disease, tachyarrhythmias, severe heart failure [classified as NYHA III-IV], severe lung dysfunctions, etc))
3. History of thrombosis plus two or more risk factors as defined in Caprini thrombosis risk assessment model
4. Lactating or pregnant women, or WOCBP who are unwilling to use highly effective contraceptive measures during the study period
5. Abnormal liver and renal functions: AST or ALT or total bilirubin ≥1.5 × ULN, and/or creatinine ≥176.8 μmol/L
6. Women of childbearing potential (WOCBP) that are pregnant or wish to become pregnant during the prospective phase of the study.
7. Other conditions which the investigator considers inappropriate for enrollment

adult ITP patients