Advances in Ex Vivo T Cell Depletion - Where Do We Stand?

Area of Science:

• Hematology
• Immunology
• Transplantation Medicine

Background:

• Graft-versus-host disease (GVHD) is a significant complication following allogeneic hematopoietic cell transplantation (HCT), contributing to patient morbidity and mortality.
• Donor T cells are primary mediators of GVHD, leading to strategies focused on their depletion from the graft.

Purpose of the Study:

• To review the methods and outcomes of ex vivo T cell depleted (TCD) HCT, specifically focusing on CD34+ cell selection.
• To evaluate the efficacy of CD34+ selected HCT in preventing acute and chronic GVHD.

Main Methods:

• Review of existing literature and clinical data on T cell depleted HCT using CD34+ selection.
• Comparison of outcomes, including GVHD rates, relapse, survival, and GVHD-free relapse-free survival (GRFS), with conventional HCT platforms.

Main Results:

• CD34+ selected T cell depleted HCT is effective in preventing acute and chronic GVHD across various hematologic malignancies.
• This approach generally does not lead to adverse relapse or survival outcomes, except possibly in chronic myeloid leukemia.
• Retrospective analyses show higher GRFS rates for CD34+ selected HCT compared to conventional HCT.
• While requiring myeloablative conditioning and antithyrimocyte globulin, the reduced need for calcineurin inhibitors and methotrexate may lower toxicity, enabling use in older or comorbid patients.

Conclusions:

• CD34+ selected T cell depleted HCT presents a promising platform for GVHD prevention.
• An ongoing randomized trial (BMT CTN 1301) comparing CD34+ selected HCT with conventional HCT may establish it as a new standard of care.