Safety and Early Efficacy Study of TBX-2400 in Patients With AML or Myelofibrosis

Inclusion Criteria: 1. For crAML: AML with ≥5% blasts (either by morphology or by multi-parameter flow cytometry \[MFC\]) in a marrow aspirate obtained within 21 days of enrollment in the trial, and following the administration of at least two prior courses of chemotherapy; 2. For MF: primary MF or MF that has progressed from a myeloproliferative disease. Dynamic International Prognostic Scoring System (DIPSS)-plus to be utilized to support the inclusion of MF subjects at screening; 3. Subject undergoing allogeneic stem cell transplantation on the decision of transplanting physician; 4. Signed informed consent of donor and recipient; 5. Subjects of ≥ 18 years of age (no upper age limit); 6. Donor agrees to donate bone marrow-derived or mobilized peripheral blood stem cells; 7. Subjects with Eastern Cooperative Oncology Group (ECOG) Performance Status 0 to 2; 8. Adequate pulmonary function with Diffusing Capacity for Carbon Monoxide (DLCO) \> 50; 9. Women of childbearing potential (WOCBP) must agree to follow instructions for method(s) of contraception (e.g. sterilization, hormone implants, hormone injections, intrauterine devices, or vasectomized partner with combined use of condom and/or birth control pills) from screening until 6 months after TBX-2400 transplantation; 10. Able to adhere to all trial treatments and procedures. Exclusion Criteria: 1. Previous stem cell transplantation; 2. For MF: Blasts \> 10% in a marrow aspirate obtained within 30 days of screening; 3. Renal function: serum creatinine \> 1.5 x Upper Limit of Normal (ULN); 4. Hepatic function: impaired synthetic function as indicated by a serum fibrinogen below the normal limit. Aspartate transaminase/alanine transaminase (AST/ALT) \> 3.0 x ULN. Bilirubin, \> 1.5 x ULN; 5. Cardiac function: ejection fraction \< 45% as determined by echocardiography; 6. Prior malignancy active within previous three years - except for locally curable cancers such as cutaneous basal or squamous cell cancer, superficial bladder cancer, carcinoma in situ of cervix or breast, or carcinoma in situ of the prostate; 7. Positive pregnancy test or breastfeeding for women of childbearing age; 8. Serologic evidence of chronic Hepatitis B virus infection or Hepatitis C exposure; 9. Known history of positive test for Human Immunodeficiency Virus (HIV) or known Acquired Immunodeficiency Syndrome (AIDS); 10. Hypersensitivity to any trial medication (including the preparative regimen, TBX-2400 treatment and any prophylaxis or other medication planned); 11. Presence of a serious or uncontrolled medical disorder that, in the opinion of the Investigator, may increase the risk associated with trial participation or trial drug administration, impair the ability of the participant to receive protocol therapy, or interfere with interpretation of trial results.