The goal of this clinical trial is to demonstrate the safety of the neonatal thymus transplant in an adult patient. The main questions it aims to answer are:

• Is the neonatal thymus transplant a safe procedure?
• What is the adverse event profile of the neonatal thymus transplant?

This is a single-subject study; thus, there will not be comparison groups. The participant will receive multidisciplinary supportive care before, during, and after the procedure.

Inadequate thymopoiesis is probably related to autoimmunity, immunodeficiency, and immunosenescence. Enhancing thymopoiesis may be attractive for managing or studying such immunologic phenomena. Thymopoiesis is supported by the adult thymus transplant, as demonstrated in different animal models. Several approaches to enhance thymopoiesis in humans have been reported, which include in-vitro and in-vivo regeneration of the thymus and avascular grafting of allogeneic processed thymic tissue, among others.

Although a supermicrosurgical technique for neonatal thymus transplantation was recently described in rabbits, it has never been described in humans. This technique can be used to perform a neonatal thymus transplantation in humans. If this technique demonstrates to be safe, future studies will follow to investigate its effect on thymopoiesis and its efficacy on different health conditions.

This single-subject, first-in-humans clinical trial aims to demonstrate the safety and investigate the adverse effect profile of the neonatal thymus transplant in an adult with acute myeloid leukemia who is not candidate for bone marrow transplant, nor intensive chemotherapy. This human model not only allows to study the safety of the neonatal thymus transplant, it will also allow to investigate the effect of the procedure on thymopoiesis.

Inclusion Criteria:

• Diagnosis of acute leukemia in palliative care, either myeloid (AML) or lymphocytic (ALL).
• Not candidate for bone marrow transplant.
• Not candidate for intensive chemotherapy.

Exclusion Criteria:

• Past medical history of bone marrow transplant.
• Past medical history of severe cognitive decline or dementia.
• Past medical history of severe liver failure.
• Past medical history of chronic kidney disease (CKD) stage 4-5.
• Past medical history of acute coronary syndrome within the past 90 days.
• Past medical history of acute ischemic stroke within the past 90 days.
• Past medical history of decompensated congestive heart failure (CHF) within the past 90 days.