Select Inclusion Criteria:

          1. Subject is ≥18 years of age on the day Informed Consent is signed and dated.

          2. Subject must have received only one allogeneic HSCT from a related or unrelated donor
             prior to administration of Mana 312.

          3. Subject has a donor who has agreed to donate leukocytes for manufacture of Mana 312
             and who is the same donor who provided cells for the subject's current HSCT.

          4. a. Prior to HSCT, for Escalation Cohort 1, subject has AML/MDS b. Prior to HSCT, for
             Escalation Cohorts after Cohort 1 and for the Expansion Cohort, a subject must have
             high risk of relapse AML/MDS

          5. Mana 312 product is available

             The following Inclusion Criteria apply only during the Pre-Infusion Screening Phase,
             prior to the time of the planned first infusion of Mana 312.

          6. Subject has Eastern Cooperative Oncology Group (ECOG) performance status ≤ 3 or
             Karnofsky/Lansky score of ≥ 50.

          7. Subjects in the Expansion Cohort must have a relapse of AML/MDS (MRD+ or morphologic
             relapse)

          8. Subject has adequate organ function

        Select Exclusion Criteria:

          1. Subject has received antibody that affects T-cell number or function

          2. Subject has received a donor lymphocyte infusion (DLI) for the current HSCT.

          3. Evidence of GVHD ≥ Grade 2 in any organ system, or active bronchiolitis obliterans
             syndrome, sclerotic GVHD, or symptomatic serositis.

          4. Subject has undergone major surgery (excluding minor procedures, eg, placement of
             vascular access, gastrointestinal/biliary stent, apheresis, or biopsy) < 21 days prior
             to the first planned infusion of Mana 312.

          5. Subject has an active and clinically relevant infection

          6. Subject has symptomatic or uncontrolled brain metastases, leptomeningeal disease, or
             spinal cord compression (radiation therapy to local site for disease control is
             allowed if ≥ 14 days prior to Screening and all AE from radiation therapy have
             resolved to ≤ Grade 1 prior to the planned first Mana 312 infusion).

          7. Subject has any other medical condition not listed above or social condition that, in
             the opinion of the Investigator, might place the subject at increased risk, adversely
             affect compliance, or confound safety or other clinical study data interpretation.