Phase III Study Comparing GVHD Prophylaxis With ATG-thymoglobulin to ATLG-grafalon in Elderly Patients With Acute Myeloid Leukemia or Myelodysplasic Syndrome and Receiving an Allogeneic Hematopoietic Stem Cell Transplantation With a 10/10 HLA Matched Unrelated Donor

Inclusion criteria

• Age ≥ 50 and ≤ 70 years
• Patient between 50 and 55 years should be unfit for a myeloblative conditioning (SORROR score ≥2)
• AML requiring allogeneic stem cell transplantation (intermediate or high-risk AML) in complete cytologic response (CR1 or above) or MDS requiring allogeneic stem cell transplantation (IPSS≥ 1.5 or IPSS-R > 4.5 or IPSS-R > 3-4.5 with risk features [rapide blast increase, life-threatening neutropenia (<0.3 G/L) or thrombopenia (<30G/L) or high transfusion needs (>2/month for 6 months)]
• Without an HLA matched related donor
• Having an identified matched HLA 10/10 unrelated donor
• With usual criteria for HSCT:

• ECOG performans status ≤ 2
• No severe and uncontrolled infection
• Cardiac left ventricular ejection fraction ≥50%
• Lung DLCO > 40%
• Adequate organ function: ASAT and ALAT ≤ 3N, total bilirubin ≤ 2N, creatinine clearance ≥ 50 mL/min (except if those abnormalities are linked to the hematological disease)
• With health insurance coverage
• Having signed a written informed consent
• Contraception methods must be prescribed during all the duration of the research

NB: The authorized contraceptive methods are:

• For women of childbearing age and in absence of permanent sterilization: oral, intravaginal or transdermal combined hormonal contraception, oral, injectable or transdermal progestogen-only hormonal contraception, intrauterine hormonal releasing system (IUS), sexual abstinence (only if this the preferred and usual lifestyle of the participants).
• For man in absence of permanent sterilization: sexual abstinence, condoms

Exclusion criteria

• Cancer in the last 5 years (except basal cell carcinoma of the skin or "in situ" carcinoma of the cervix)
• Uncontrolled infection
• Seropositivity for HIV or HTLV-1 or active hepatitis B or C
• Yellow fever vaccine and all others live virus vaccines within 2 months before transplantation
• Heart failure according to NYHA (II or more) or Left ventricular ejection fraction < 50%.
• Lung DLCO ≤ 40%
• Preexisting acute hemorrhagic cystitis
• Renal failure with creatinine clearance < 50ml / min
• Pregnancy (β-HCG positive) or breast-feeding
• Patients with any debilitating medical or psychiatric illness, which would preclude the realization of the SCT or the understanding of the protocol
• Patient under state medical aid
• Patient under legal protection (protection of the court, or in curatorship or guardianship).
• For Grafalon: Hypersensitivity to the active substance or to any of the excipients
• For Thymoglobulin: Hypersensitivity to rabbit proteins or to any of the excipients
• Participation in other interventional clinical trials
• Any contraindication mentioned in the SmPC of all auxiliary medicinal products planned to be used in the trial: cyclosporine, mycophenolate mofetil, fludarabine, treosulfan