Safety and Efficacy of ATIR101 as Adjunctive Treatment to Blood Stem Cell Transplantation From a Haploidentical Family Donor Compared to Post-transplant Cyclophosphamide in Patients With Blood Cancer

Inclusion Criteria: * Any of the following hematologic malignancies: * Acute myeloid leukemia (AML) in first cytomorphological remission (with \< 5% blasts in the bone marrow) with Disease Risk Index (DRI) intermediate or above, or in second or higher cytomorphological remission (with \< 5% blasts in the bone marrow) * Acute lymphoblastic leukemia (ALL) in first or higher remission (with \< 5% blasts in the bone marrow) * Myelodysplastic syndrome (MDS): transfusion-dependent (requiring at least one transfusion per month), or intermediate or higher Revised International Prognostic Scoring System (IPSS-R) risk group * Clinical justification of allogeneic stem cell transplantation where a suitable HLA matched sibling or unrelated donor is unavailable in a timely manner * Availability of a related haploidentical donor with one fully shared haplotype and 2 to 4 mismatches at the HLA-A, -B, -C, and -DRB1 loci of the unshared haplotype, as determined by high resolution human leukocyte antigen (HLA)-typing * Karnofsky Performance Status (KPS) ≥ 70% * Male or female, age ≥ 18 years and ≤ 70 years. Patients aged ≥ 65 years must have a Sorror score ≤ 3 * Patient weight ≥ 25 kg and ≤ 130 kg * Availability of a donor aged ≥ 16 years and ≤ 75 years who is eligible according to local requirements and regulations. Donors aged \< 16 years are allowed if they are the only option for an HSCT, if they are permitted by local regulations, and if the IRB/IEC approves participation in the study. * For females of childbearing potential who are sexually active and males who have sexual contact with a female of childbearing potential: willingness to use of reliable methods of contraception (oral contraceptives, intrauterine device, hormone implants, contraceptive injection or abstinence) during study participation * Given written informed consent (patient and donor) Exclusion Criteria: * Diagnosis of chronic myelomonocytic leukemia (CMML) * Availability of a suitable HLA-matched sibling or unrelated donor in a donor search * Prior allogeneic hematopoietic stem cell transplantation * Diffusing capacity for carbon monoxide (hemoglobin corrected DLCO) \< 50% predicted * Left ventricular ejection fraction \< 45% (evaluated by echocardiogram or MUGA scan) * Aspartate aminotransferase (AST) and/or alanine aminotransferase (ALT) \> 2.5 × upper limit of normal (CTCAE grade 2) * Creatinine clearance \< 50 ml/min (calculated or measured) * Positive pregnancy test or breastfeeding of patient or donor (women of childbearing age only) * Estimated probability of surviving less than 3 months * Known allergy to any of the components of ATIR101 (e.g., dimethyl sulfoxide) * Known hypersensitivity to cyclophosphamide or any of its metabolites * Any contraindication for GVHD prophylaxis with mycophenolate mofetil, cyclosporine A, or tacrolimus * Known presence of HLA antibodies against the non-shared donor haplotype * Positive viral test of the patient or donor for human immunodeficiency virus (HIV)-1, HIV-2, hepatitis B virus (HBV), hepatitis C virus (HCV), Treponema pallidum, human T-lymphotropic virus (HTLV)-1 (if tested), HTLV-2 (if tested), West Nile virus (WNV; if tested), or Zika virus (if tested) * Any other condition that, in the opinion of the investigator, makes the patient or donor ineligible for the study