Inclusion Criteria:

• Diagnosed with primary acquired aplastic anemia according to the 2024 British Society for Haematology guideline, Guidelines for the Diagnosis and Management of Adult Aplastic Anaemia, and the Chinese Guideline for the Diagnosis and Treatment of Aplastic Anemia (2022 edition) issued by the Hematology Branch of the Chinese Medical Association.
• Previously diagnosed with severe aplastic anemia (SAA) or very severe aplastic anemia (VSAA), with no response or relapse after receiving anti-thymocyte/anti-lymphocyte globulin (ATG/ALG) in combination with standard-dose cyclosporine for at least 6 months, and standard-dose thrombopoietin receptor agonist (TPO-RA) therapy for at least 4 months.
• Hemoglobin <90 g/L or platelet count <30×10^9/L
• Unsuitable for or unwilling to undergo hematopoietic stem cell transplantation, with no better available treatment options.
• Age ≥18 years, regardless of gender.
• Eastern Cooperative Oncology Group (ECOG) performance status score ≤2
• Willing and able to comply with the requirements for this study and written informed consent.

Exclusion Criteria:

• Diagnosed with congenital bone marrow failure syndromes
• Bone marrow reticulin fibrosis grade ≥2
• Subjects with a paroxysmal nocturnal hemoglobinuria (PNH) clone ≥50% or active hemolysis
• Subjects with clonal cytogenetic abnormalities characteristic of myelodysplastic syndromes, except +8, del(20q), and -Y
• Active bacterial, viral, or fungal infection within 2 weeks before the first dose of the investigational drug, excluding common cold and onychomycosis, or any other serious infection. Any anti-infective treatment course for infection must have been completed at least 2 weeks before the first dose. Subjects with a history of HIV infection or positive HIV antibody during screening; positive Treponema pallidum antibody during screening; active tuberculosis, defined as chest imaging or other relevant examinations within 3 months before the first dose of the investigational drug or during screening suggesting active tuberculosis infection; or active hepatitis during screening, defined as hepatitis B surface antigen (HBsAg) positivity, or hepatitis B core antibody (HBcAb) positivity with hepatitis B virus (HBV) DNA ≥30 IU/mL, or hepatitis C virus (HCV) antibody positivity with HCV RNA positivity
• Active bleeding in the gastrointestinal tract, respiratory tract, central nervous system, or other sites
• A history of any clinically significant disease that, in the investigator's opinion, would pose a safety risk to the subject if participating in the study, or would affect the evaluation of efficacy or safety if the disease/condition worsens during the study, including but not limited to: a. cardiovascular diseases, such as a history of acute myocardial infarction or unstable angina within the past year, severe arrhythmia such as frequent multifocal premature ventricular contractions, ventricular tachycardia, or ventricular fibrillation, congestive heart failure, arterial or venous thrombosis, or New York Heart Association (NYHA) class III-IV cardiac function; b. a history of psychiatric disorders, severe cerebrovascular disease, or cognitive sequelae
• Use of agents targeting B cells or plasma cells within 3 months before the first dose of the investigational drug or anticipated use during the clinical trial
• Treatment with anti-lymphocyte globulin or anti-thymocyte globulin within 6 months before the first dose of the investigational drug
• Treatment with tacrolimus, sirolimus, cyclophosphamide, anti-CD52 monoclonal antibody, or similar therapies within 4 weeks or 5 half-lives, whichever is shorter, before the first dose of the investigational drug
• Planned participation in another clinical trial, or prior exposure to another investigational product before the first dose, with an interval of less than 4 weeks or 5 half-lives of the drug, whichever is shorter
• Receipt of a live attenuated vaccine within 4 weeks before the first dose of the investigational drug or planned receipt during the study, or receipt of a COVID-19 vaccine within 7 days before dosing
• Prior treatment targeting CD38
• Women who are pregnant or breastfeeding, or who plan to become pregnant or breastfeed during the study
• Patients considered to be ineligible for the study by the investigator for reasons other than the above