Manufacturing A Donor Lymphocyte Product Depleted Of TCR-αβ T Cells And CD19+ B Cells For Prophylactic Infusion Following Allogeneic Stem Cell Transplantation

Abstract

Background & Aim Background In allogeneic stem cell transplantation (HSCT), relapse of hematologic malignancies is a leading cause of post-transplant morbidity. In the early post-transplant period, when immune reconstitution is pending, residual leukemic clones can proliferate, resulting in disease relapse with bleak prognosis and limited treatment options. Donor lymphocyte infusions (DLI) are often used as treatment of post-transplant leukemia relapse but this practice is limited by graft versus host disease (GVHD) as a complication. Adoptive transfer of selected lymphocyte subsets that effect tumor cytotoxicity without inducing GVHD, such as natural killer (NK) cells and TCRγδ T cells, may provide early donor-derived surveillance for residual or early relapse disease after HSCT. With this background, a Phase I clinical trial (CASE1Z19) was designed to explore the prophylactic administration of donor lymphocytes depleted of TCR-αβ T cells and CD19+ B cells early in the post-transplant course. A maximum threshold of Methods, Results & Conclusion Methods Three qualification runs were conducted using the Miltenyi CliniMACS Plus system to deplete TCR-αβ T and CD19+ B cells from non-mobilized, peripheral blood mononuclear cells (PBMC) in leukapheresis products sourced by a commercial vendor. Each product was analyzed for lymphocyte subset composition and stability post-processing. Results The mean starting total white blood cell count was 6.4 × 109 cells from which TCR-αβ T cells and CD19+ B cells were maximally depleted by >99.8% with mean Log10 reductions of 3.10 and 3.06 respectively (Table1). The TCR-αβ T cell content in products generated from each run were 0.2-0.5 × 105/kg, based on an average 60kg adult. The yield of NK cells and TCRγδ T cells from each manufacturing ranged from 50-97% and 86-100% respectively. All products were stable post-processing, at room temperature for up to 6 hours, with a mean cell viability of 95.1%. Conclusion A donor lymphocyte product sufficiently purified of TCRαβ T and CD19+ B cells with subsequent enrichment of NK cells and TCR-γδ T cells can consistently be generated for prophylactic adoptive transfer in the post-transplant setting. Additional analysis characterizing NK and TCR-γδ T cell subsets for function and activation is underway.