Arsenic Trioxide to Prevent Relapse in Patients Undergoing Allogeneic Stem Cell Transplantation for Acute Myeloid Leukemia or Myelodysplastic Syndrome

Inclusion Criteria: * AML or MDS patients eligible to receive first allogeneic HCT. Eligibility inclusion for HCT is defined as per University of Michigan bone marrow transplant (BMT) standard of care criteria * Presence of high-risk AML/MDS with probable biallelic TP53 deletion or mutation status, defined by one of the following in prior blood or bone marrow assessments: * TP53 loss by karyotype (chromosome 17 or 17p deletion) or single nucleotide polymorphism (SNP) (Cancer Microarray) AND ≥ one clonal TP53 mutation by next generation sequencing (NGS) (VAF \> 10%). * ≥ one TP53 mutation by NGS testing (with VAF \> 40%) * ≥ two distinct TP53 mutation(s) by NGS (VAF \>10%) * Evidence that at least one TP53 allele harbors a structural TP53 missense mutation. In cases where the mutation type is unclassified, molecular pathology assessment is required to determine if one of the lesions is a missense mutation (as described in NGS report) * Patients may be enrolled with either active disease or in morphological remission, provided the bone marrow blast count on the pre-HCT assessment does not exceed 30% * Age \> 21 years at enrollment and receiving allogeneic HCT in the adult transplant program * Karnofsky performance score (KPS) ≥ 70% * Documentation of adequate pulmonary function by forced expiratory volume and 1 second (FEV1) ≥ 50% of predicted, forced vital capacity (FVC) ≥ 50% of predicted and DLCO (corrected for hemoglobin) ≥ 50% of predicted (must meet all criteria a…