The aim of this trial is to evaluate the efficacy of GVH prophylaxis reinforced by low-dose Thymoglobulin administered at the end of aplasia after haploidentical allogeneic transplantation.

Patients will receive a single infusion of Thymoglobulin at a dose of 1 mg/kg between 48h and 72h after emergence from aplasia, and will be followed for 12 months.

Inclusion Criteria:

• Adults aged ≥ 60 or aged 50 to 59 with comorbidities (HCT-CI10 score ≥ 3),

• Hematological malignancies except myeloproliferative syndrome and myelodysplastic syndrome,

• Patient having received an allograft within ≤ 35 days, performed with the following modalities:

  • First allogeneic transplant,
  • Haploidentical donor,
  • Peripheral stem cell transplant,
  • Non-myeloablative "Baltimore"-type conditioning, delivered as standard in routine care, as reported in the literature (fludarabine, cyclophosphamide, total body irradiation),
  • Standard GVHD prophylaxis in the context of haploidentical transplants (post-transplant cyclophosphamide, ciclosporin A and mycophenolate mofetil).

• Patient discharged from aplasia within ≤ 35 days,

• Signed informed consent form,

• Affiliation with a social security.

Exclusion Criteria:

• Previous allogeneic or organ transplant,
• Presence of signs of GVHD,
• Contraindications to treatment with Thymoglobuline®,
• Hypersensitivity to rabbit proteins or to any of the excipients listed in the "Composition" section of the summary of product characteristics,
• Pregnant women or may become pregnant (without effective contraception) or breast-feeding,
• Persons in emergency situations or unable to give informed consent form,
• Adult with a legal protection measure (adult under guardianship, curatorship or safeguard of justice),
• Unable to comply with medical follow-up for geographical, social or psychological reasons.