Allogeneic iNKT Cell Therapy (agenT-797) After SCT

The goal of this clinical trial is to learn if agenT-797 is safe to use on people undergoing allogenic hematological stem cell transplantation (SCT). The main questions it aims to answer are: * Is agenT-797 safe to use? * What medical problems do participants have when taking agenT-797? Participants will receive an infusion of agenT-797 about 7 days after their allogenic SCT.

Inclusion Criteria: * Age ≥18 years at the time of consent * Adult patients anticipated to get an allogeneic hematopoietic cell transplantation (allo-SCT) * All donor types are accepted (MMUD \[mismatched unrelated donor\], MUD \[matched unrelated donor\], MSD \[matched sibling donor\], haploidentical) * All conditioning regimens will be accepted (MAC \[myeloablative conditioning\], RIC \[reduced-intensity conditioning\], NMAC \[non-myeloablative conditioning\]) * Karnofsky Performance Scale (KPS) \> 70 * Eligible Diagnoses: * Acute myeloid leukemia (AML) with intermediate/high-risk features or relapsed disease * Chronic myeloid leukemia (CML) in accelerated or blast phases * Myelodysplastic syndrome (MDS) with intermediate/high-risk features * Acute lymphoblastic leukemia (ALL) with high-risk features or relapsed disease * or any patients undergoing allogeneic stem cell transplant (allo-SCT) as standard of care could be eligible Exclusion Criteria: * Excluded Diagnoses: Primary Myelofibrosis in the dose escalation phase and could be included in the dose-expansion phase