Allogeneic hematopoietic cell transplantation (allo-HCT) is the only potential cure for Myelodysplastic syndrome (MDS). Currently, the conditioning regimen for MDS allogeneic transplantation still follows AML, and there are fewer explorations in this field. In a large-scale retrospective analysis with 532 MDS undergoing allo-HCT, reduced intensity conditioning is resulted in improved overall survival (OS), reduced non-relapse mortality (NRM) , while sparing relapse.

Therefore, the investigators conduct a prospective, single-arm, multicentre study to evaluate the efficacy and safety of Fludarabine-Melphalan-Busulfan reduced-intensity conditioning in MDS patients.

This study is a prospective, multicenterstudy designed to evaluate the efficacy and safety of evaluate the efficacy and safety of Fludarabine-Melphalan-Busulfan intermediate-intensity transplantation conditioning regimen for the treatment of MDS. . Patients with MDS who are eligible for enrolment were pretreated with a Fludarabine-Melphalan-Busulfan regimen (Fludarabine 30mg/m2d-6 to -2; melphalan 70mg/m2d-6; busulfan 3.2mg/kg d-4 to -3). The primary endpoint is 2-year relapse-free survival (RFS) after transplantation. Secondary endpoints includes 2-year post-transplant survival (OS) and cumulative recurrence rate at 2 years post-transplant.

Inclusion Criteria:

• Age 14-70 (including boundaries) and gender;
• Diagnosis of MDS is confirmed on the basis of bone marrow cytomorphology, immunophenotyping and chromosomal and molecular biology tests;
• IPSS-R intermediate-risk or higher-risk or IPSS-M intermediate-risk or higher-risk MDS; transfusion-dependent MDS;
• ECOG score≤ 3 points;
• Have appropriate organ function, and laboratory results within 7 days prior to the start of trial treatment need to meet the following criteria:
• Aspartate aminotransferase (AST) ≤ 3 times ULN (upper limit of normal, ULN);
• Alanine aminotransferase (ALT) ≤ 3x ULN;
• Total serum bilirubin ≤ 1.5 times the upper limit of normal ULN unless the patient has documented Gilbert syndrome; patients with Gilbert-Meulengracht syndrome with bilirubin ≤ 3.0 times the upper limit of normal and direct bilirubin ≤ 1.5 times the upper limit of normal may be included;
• Serum creatinine ≤ 1.5 times ULN or creatinine clearance ≥ 60 mL/min;
• Coagulation function: International Normalised Ratio (INR) ≤ 1.5 x ULN, Activated Partial Thromboplastin Time (APTT) ≤ 1.5 x ULN;
• Left ventricular ejection fraction (LVEF) ≥50%;
• Voluntarily signing the informed consent, understanding and complying with the requirements of the study, good compliance, and cooperating with the follow-up visits.

Exclusion Criteria:

• Allergies or contraindications to any of the drugs in the protocol;
• Currently have clinically significant active cardiovascular disease such as uncontrolled arrhythmias, uncontrolled hypertension, congestive heart failure, any grade 3 or 4 heart disease as determined by the New York Heart Association (NYHA) functional class, or a history of myocardial infarction within the 6 months prior to screening;
• Serious medical conditions that may limit the patient's participation in this trial (e.g., progressive infection, uncontrolled diabetes);
• Active autoimmune diseases such as SLE, rheumatoid arthritis, etc;
• Patients with neurological or psychiatric disorders;
• The patient is pregnant or breastfeeding;
• Those who are unable to understand or comply with the study protocol or are unable to sign the informed consent form.
• Other conditions that, in the opinion of the investigator, make the patient otherwise unsuitable for participation in this study;