Patients who have a gastrointestinal acute Graft versus host disease (GVHD) received a first-line standard treatment of corticosteroids. For patients who do not respond or progress after an initial response have a high mortality. There is an interest in identifying effective second line therapy for these patients corticosteroid-resistant acute GVHD. Fecal microbiota transfer might be a beneficial treatment in this clinical situation with a poor prognosis and limited therapeutic options.

Inclusion Criteria:

• Patients who develop a first episode of Stage 2 to 4 Gastro-intestinal Acute Graft-versus-Host (GI-aGVHD) with gut predominance (Przepiorka D, 1995), resistant to a first line therapy with steroids (lack of improvement after 5 days or progression after 3 days of treatment with corticosteroids at 2 mg/Kg methylprednisolone equivalent dose) (SR GI-aGVHD)
• Age ≥ 18 years old
• Allogeneic Hematopoietic stem cell transplantation (Allo-HSCT) with any type of donor, stem cell source, GVHD prophylaxis or conditioning regimen
• Patients able to have a minimum of 12 hours discontinuation of systemic antibiotics in order to perform the allogeneic FMT
• Signature of informed and written consent by the subject or by the subject's legally acceptable representative

Exclusion Criteria:

• Grade IV hyper-acute GVHD
• Overlap chronic GVHD
• Acute GVHD after donor lymphocytes infusion
• Relapsed/persistent malignancy requiring rapid immune suppression withdrawal
• Active uncontrolled infection according to the attending physician
• Other systemic drugs than corticosteroids for GVHD treatment (including extra-corporeal photopheresis). Drugs already being used for GVHD prevention (eg. calcineurin inhibitors) are allowed.
• Absolute neutrophil count < 0.5 x 10^9 /L
• Absolute platelet count < 10 000
• Patient Epstein-Barr Virus (EBV) negative
• Evidence of toxic megacolon or gastrointestinal perforation on abdominal X-ray
• Known allergy or intolerance to trehalose or maltodextrin
• Pregnancy: positive urinary or blood test in female of childbearing potential; lactation; absence of effective contraceptive method for female of childbearing potential
• Other ongoing interventional protocol that might interfere with the current study primary endpoint.