Avatrombopag Combined With IST as First-line Treatment for SAA

Inclusion Criteria: 1. Patients with newly diagnosed severe aplastic anemia. 2. Men and women aged between 12 and 60. 3. Subjects must complete all screening assessments as outlined in the test protocol. 4. Able to swallow or administer orally. 5. Before the start of the research procedure, the patient or guardian should fully understand the research procedure and purpose and sign the informed consent form. If the patient's signature is not conducive to the treatment of the disease, the patient's immediate family should sign the informed consent form. Exclusion Criteria: 1. Congenital bone marrow failure (eg. Fanconi anemia). 2. Accompanied by cytogenetic cloning changes (chromosomal karyotype and FISH detection found somatic cloning abnormalities; Simple -Y abnormality can be included in this study;) . 3. ATG or middle/high-dose cyclophosphamide was used in the past. 4. Previous treatment with cyclosporine or tacrolimus \> 6 months. 5. The total course of treatment with TPO receptor agonists (including thrombopoietin, eltrombopag,hetrombopag and avatrombopag) was more than 1 month. 6. Serious infectious diseases (tuberculosis without effective control, pulmonary aspergillosis, viral infections). 7. AIDS patients. 8. Pregnant or breastfeeding, fertile but unwilling to take effective contraceptive measures. 9. Patients with malignant tumors who are not suitable for ATG treatment. 10. A newly diagnosed history of cardio/cerebral vascular thrombosis within 12 months. 11. Those who are assessed as unsuitable for inclusion by the investigator.