The purpose of the study is to evaluate the efficacy and safety of avatrombopag for the promotion of platelet engraftment after Allo-HSCT.

Patients with thrombocytopenia (PLT<20×10^9/L) after allogenic hematopoietic stem cell transplantation (Allo-HSCT) who meet Eligibility Criteria were assigned into the avatrombopag group for 4 weeks' treatment.

Inclusion Criteria:

• Male or female, aged between 18-60 years;
• PLT<20×10^9/L after 14 days of allo-HSCT;
• Expected survival time > 3 months;
• ECOG performance status 0-2;
• Agree to receive the treatment of avatrombopag after Allo-HSCT and must sign the informed consent form.

Exclusion Criteria:

• Pregnant or lactating;
• With severe and uncontrollable infection;
• With graft-versus-host disease (GVHD) with steroid resistance;
• With thrombotic microangiopathy; With active thromboembolism requiring anticoagulation
• With detected disease recurrence due to chimerism by flow cytometry;
• With chronic active hepatitis B and C virus infection;
• With secondary or multiple transplantation, or multiple organ transplantation;
• With severe heart disease, lung disease, diabetes and metabolic diseases;
• HIV positive;
• With a history of PLT dysfunction or bleeding disorders
• With the active hepatic venous occlusion disease, or a history of clinically significant hepatic venous occlusion disease (The disease was defined as the abnormal condition of painful hepatomegaly after transplantation with bilirubin ≥ 6.0 mg/dL);
• With progressive solid tumor;
• With severe bleeding requiring transfusion of more than 2 units of red blood cells, or sudden drop of blood cell volume ≥10% within 7 days prior to screening;
• With any other clinical trial of investigational product or device within 30 days prior to the baseline visit, except for observational study;
• With treatment of thrombopoietin receptor agonist (TPO-RA) one month before enrollment;
• Deemed unsuitable for enrollment by the investigator.