Inclusion Criteria:

   1. Patients aged ≥18 years

   2. Patients must have CD33+ AML in relapse or refractory after alloHCT

   3. Patients must be a recipient of an 8/8 (A, B, C, DRB1) HLA-matched related or
   unrelated donor alloHCT. Patients previously transplanted with VOR33 in the VBP101
   study who have R/R AML may also be considered.

   4. Disease status at the time of enrollment:

      1. Arm A/Morphologic disease: Defined as ≥ 5% blasts (bone marrow) post-HCT

      2. Arm B/MRD positive: < 5% blasts (bone marrow) with minimal residual disease of at
      least 0.1% CD33+ leukemia cells by flow cytometry

   5. Performance status: ECOG 0 or 1

   6. Patient must have adequate organ function as defined by:

      1. Cardiac: Left ventricular ejection fraction (LVEF) ≥ 45% or fractional shortening
      ≥ 28%

      2. Pulmonary: Baseline oxygen saturation > 92% on room air at rest

      3. Hepatic: Total bilirubin < 3x institutional upper limit of normal (ULN) (except
      in case of patients with documented Gilbert's disease < 5x ULN) and aspartate
      aminotransferase (AST/SGOT)/alanine aminotransferase (ALT/SGPT) < 5x
      institutional ULN

      4. Renal: Serum creatinine must be ≤ 1.2x institutional ULN or creatinine clearance
      ≥ 60 mL/min for patients with creatinine levels above institutional normal

   7. Original alloHCT donor is available and willing to undergo apheresis

Exclusion Criteria:

   1. Patients who have undergone more than one alloHCT

   2. Patients who have undergone alloHCT with a mismatched unrelated donor, haploidentical
   donor, or with umbilical cord blood as the stem cell source

   3. Patients who will be less than 100 days post-alloHCT at the time of VCAR33 infusion.

   4. Patients with any history of Grade III or IV acute GVHD or severe chronic GVHD unless
   approved by the Sponsor Medical Monitor

   5. Patients with evidence of ongoing active acute or chronic GVHD and are taking systemic
   immunosuppressive agents (> 10 mg daily of prednisone equivalent or other
   GVHD-directed treatment, including extracorporeal photopheresis). Patients with Grade
   1 acute GVHD limited to the skin or mild chronic GVHD limited to the eyes, mouth, or
   skin controlled with only topical therapy are eligible.

   6. Patients with active CNS disease. A lumbar puncture is not required to exclude CNS
   disease in the absence of clinical signs or symptoms suggesting CNS disease.

   7. Patients with the following prior therapy:

      1. DLI within 28 days prior to enrollment

      2. Prior treatment with any CAR T cell therapy product

   8. Patients with active or uncontrolled viral, bacterial, or fungal infection

   9. Patients with a history of a human immunodeficiency virus (HIV) infection or acute or
   chronic active hepatitis B or C infection

10. Patients with a history of malignancy other than nonmelanoma skin cancer or carcinoma
   in situ (e.g., cervix, bladder, or breast) unless disease free for at least 3 years
   after the last definitive therapy

11. Female patients of childbearing potential who are pregnant or breastfeeding