The Study of Different Cycles of High-dose Dexamethasone in the Treatment of ITP

Inclusion Criteria: * Participant must be at least 18 years of age at the time of the screening. * Participant may be male or female. * Participant has a confirmed diagnosis of newly diagnosed ITP according to the 2019 International Working Group assessment at screening, and has a baseline platelet count of less than 30 × 10\^9 cells per L or had bleeding manifestations, or both. Exclusion Criteria: * Participant has evidence of a secondary cause of immune thrombocytopenia (e.g. leukemia, lymphoma, common variable immune- deficiency, systemic lupus erythematosus, autoimmune thyroid disease, past medical history of untreated H. pylori infection) or to drug treatments (e.g. heparin, quinine, antimicrobials, anticonvulsants) or participant has a multiple immune cytopenia, e.g. Evan's syndrome. * Participant has clinically life-threatening bleeding (e.g. central nervous system bleeding, menorrhagia with significant drop in hemoglobin). * Participant has a history of coagulopathy disorders other than ITP. * Participant has a history of arterial or venous thromboembolism (e.g. stroke, transient ischemic attach, myocardial infarction, deep vein thrombosis or pulmonary embolism) within the 6 months prior to randomization or requires anticoagulant treatment. * Participant has 12-lead ECG with changes considered to be clinically significant upon medical review at baseline. * Participant has severe renal impairment (glomerular filtration rate less than 45ml/min/1.73 m2). * Participant has 3 × upper limit of normal of any of the following: alanine aminotransferase, aspartate aminotransferase, or alkaline phosphatase. * Participant with any of the following conditions: severe immunodeficiency, active or previous malignancy, human immunodeficiency virus (HIV), hepatitis B or C virus infection, pregnancy or lactation.