This is a Phase 1, open label, dose-escalation study to evaluate the safety, expansion, persistence, and preliminary clinical activity of lentivirally transduced autologous T cells expressing anti-CD64 chimeric antigen receptors (CAR) expressing tandem CD3ζ and 4-1BB (CD3ζ/4-1BB) costimulatory domains in subjects with refractory or relapsed (R/R) acute myeloid leukemia (AML). This CAR T cell product will be referred to as "CD64 CAR T" which is CD64 directed, autologous, genetically modified CAR T cells. The primary objective of the study is to identify the safety profile and maximum tolerated dose (MTD) of CD64 CAR T in subjects with R/R AML as determined by the defined DLTs using a standard Bayesian Optimal Interval (BOIN) design.

Inclusion Criteria:

1. ≥ 18 years of age.

2. Subjects must have one of the following diagnoses per the International Consensus Classification (ICC) 2022 criteria:

   a. Acute Myeloid Leukemia (AML).

3. Refractory OR relapsed AML:

   a. Refractory disease i. ≥5% blasts in the bone marrow or peripheral blood by morphology, flow cytometry, or immunohistochemistry after a minimum of 1 cycle of a hypomethylating agent (HMA) and venetoclax (Ven) combination (Ven/HMA) b. Relapsed disease i. Recurrence of ≥ 5% blasts in the bone marrow or peripheral blood by morphology, flow cytometry or immunohistochemistry.

4. Subjects must have received at least one prior line of therapy, including at least one line of therapy containing Ven.

5. Documentation of CD64 expression on ≥70% of myeloid blasts by flow cytometry after the most recent relapse, as determined by standardized and validated multiparameter flow cytometry assay (Hematologics, Inc., Seattle, WA).

6. Total white blood cell (WBC) count ≤ 25 x 10(to the 9th)/L prior to apheresis. Hydroxyurea is permitted to achieve this

7. Absolute lymphocyte count (ALC) ≥ 200/µL prior to apheresis OR ALC < 200 µL with concurrent lymphocyte subset analysis (CD3, CD4, and CD8 counts) confirming an absolute CD3 count ≥ 150/µL.

8. Confirmed availability of cells for a rescue stem cell transplant AND subject must be deemed an appropriate candidate for such therapy per institutional standards.

9. Subjects who have undergone prior allogeneic stem cell transplant must be ≥ 6 months out from transplant and be off systemic immunosuppression for at least 1 month at the time of enrollment with no evidence of active graft versus host disease.

10. Adequate organ function, defined as:

    1. Creatinine clearance ≥ 30 mL/min, based on the CKD-EPI Creatinine Equation (2021).
    2. AST/ALT ≤ 5x upper limit of the normal range, unless considered to be due to leukemic involvement.
    3. Bilirubin ≤ 3x upper limit of the normal range, unless the subject has Gilbert's Syndrome or considered to be due to leukemic involvement.
    4. Must have a minimum level of pulmonary reserve defined as ≤ Grade 1 dyspnea and pulse oxygen > 92% on room air, unless considered to be due to leukemic involvement.
    5. Left Ventricle Ejection Fraction (LVEF) ≥ 40% confirmed by ECHO/MUGA.

11. ECOG performance status 0, 1, or 2.

12. Signed informed consent form.

13. Subjects of reproductive potential must agree to use acceptable birth control methods, as described in the protocol main text.

14. Willing to participate in the long-term follow-up protocol that is required if CAR T cell therapy is administered.

Exclusion Criteria:

1. Subjects with Acute Promyelocytic Leukemia (APL) with t(15;17)

2. Receipt of previous chemotherapy for AML, as follows:

   a. Prior to apheresis, the following washout periods apply: i. Hydroxyurea: 1 day ii. Hypomethylating agent and/or venetoclax: 7 days iii. Small molecule targeted therapy (including tyrosine kinase inhibitors): 3 half-lives or 7 days, whichever is shorter.

   iv. Immune checkpoint inhibitors or other immunological agents: 5 half-lives or 28 days, whichever is shorter.

   v. Investigational products: 5 half-lives or 28 days, whichever is shorter. vi. Any other systemic chemotherapy: 14 days vii. Allogeneic stem cell transplantation: 180 days viii. Donor lymphocyte infusion (DLI): 60 days ix. Craniospinal or total body radiation: 42 days b. After apheresis and prior to lymphodepletion, no treatment for AML is permitted, with the exception of bridging hydroxyurea with a washout period of 1 day prior to the start of the lymphodepletion regimen.

3. Concurrent use of systemic steroids or immunosuppressant medications. Recent or current use of inhaled steroids or physiologic replacement with hydrocortisone is not exclusionary.

4. Previous treatment with investigational gene or cell therapy (including CAR therapy).

5. Signs or symptoms indicative of CNS leukemia involvement. A CNS evaluation should be performed if CNS involvement is suspected to rule out CNS leukemia involvement.

6. Pregnant or lactating (nursing) women.

7. Known HIV infection or active Hepatitis B or Hepatitis C infection.

8. Known history of allergy or hypersensitivity to study product excipients (human serum albumin, DMSO, and Dextran 40).

9. Class III/IV cardiovascular disability according to the New York Heart Association Classification.

10. Subjects with a known history or prior diagnosis of optic neuritis or other immunologic or inflammatory disease affecting the central nervous system, and unrelated to leukemia or previous leukemia treatment.

11. Subjects with cardiac arrhythmia, or arrhythmias that are not stable with medical management, within 2 weeks of the Screening/Enrollment visit.

12. Any uncontrolled active medical disorder that would preclude participation as outlined.

13. Evidence of another uncontrolled malignancy.

Apheresis Eligibility To proceed with apheresis, enrolled participants must continue to meet all inclusion criteria within no more than 21 days prior to apheresis, unless otherwise specified.

Note: Disease evaluation (bone marrow aspirate and biopsy) to meet inclusion criteria must be completed within 30 days prior to enrollment.

Lymphodepleting Chemotherapy Eligibility To proceed with lymphodepleting chemotherapy, enrolled participants must have specific assessments completed and continue to meet all inclusion criteria within 72 hours of initiation of lymphodepletion

CD64 CAR T Infusion Eligibility

Participants must meet the following criteria in order for cells to be infused (based on labs obtained within 24 hours of cell infusion):

• CD64 CAR T must have met manufacturing criteria (unless prospectively approved by IND Sponsor, Gates Institute Medical Lead, and FDA)
• Confirmation that the site has Anakinra and Ruxolitinib in stock and available (should IEC-HS treatment be required).
• Performance status determination (ECOG must be 0, 1 or 2).
• Participant remains clinically stable without evidence of vital sign instability including the lack of supportive vasoactive drugs or intensive care support.
• Must not have ALT/SGPT and AST/SGOT > 10x the ULN or total bilirubin > 3x the ULN, (unless the subject has Gilbert's Syndrome or considered to be due to leukemic involvement)
• Adequate renal function, as defined in the Inclusion Criteria.
• No evidence of uncontrolled infection within 48 hours prior to cell infusion as determined by the PI or sub-investigator.