Novel Automatic Application for Enrichment of CD34+ Hematopoietic Stem and Progenitor Cells from Apheresis Products
Authors: Dzionek Julia , Soltenborn Stephanie , Olevska Valeriya , Oberbörsch Svenja , Bosbach Christin Laura , Hebbeker Felix , Kauling Burgund , Raasch Juliane , Wenzel Carina , Lahnor Heike , Meissner Rene , Krämer Katharina , Papanikolaou Eleni , Bosio Andreas 
Published: December 2024

Enrichment of CD34+ cells from leukaphereses has been used for decades as a curative treatment for hematologic malignant diseases in the context of allogeneic hematopoietic stem cell transplantation (HSCT) as a measure to mitigate graft vs host disease (GVHD). With the advent of genetic therapies for rare diseases of the blood, CD34+ enrichment was one of those conditions, which without, gene therapies would not have been possible to realize. In addition, the so called “stem cell boost” has also emerged as a potent treatment modality not only in the classic HSCT field but in the context of CAR-T cell therapy as well, as a measure to manage cytopenias .Therefore, new, more robust and more user friendly processes need to be established to facilitate administration of CD34+ in the different therapeutic scenarios without compromising the number of the transplantable CD34+ cells as well as the purity of the graft(s).

Based on MACS Technology the CliniMACS Prodigy HSC Enrichment System enables automatic production of an injectable CD34 enriched cell population which is simultaneously passively depleted by allogeneic reactive T cells. Central components of the new application, which utilizes tubing set TS 320, include a newly developed platelet removal step, a white blood cell (WBC)-adjusted separation and the possibility of product release at a requested timepoint because the process allows storage of the labeled cells for up to 16h. The process is sufficient for the enrichment of 1.2x10 CD34+ cells from up to 120x10 total WBC. Finally, a new fluorescent flow analysis protocol suitable to analyze very low percentage of remaining T cells in the final product and a low percentage of CD34+ cells in the starting material was developed.

Inhouse evaluation runs (n=22) using mobilized leukapheresis products resulted in a mean depletion of 4.5 log (range 3.8 - 4.9) for T cells, a mean platelet depletion of 2.8 (range 2.2 - 3.7), a mean B cell depletion of 3.2 (range 2.1 - 3.5), and a mean purity of 91.2% (range 81.1 - 96.1) in the CD34 enriched product. Viability of CD34+ cells in the target product was above 99%, mean yield was 65% and mean WBC recovery 82%. The process duration is approximately within 3.2 - 5.5 hours, depending on the cell numbers, excluding the optional in-process storage. The comparability to the existing CliniMACS plus system was also assessed in comparison runs and we additionally evaluated the impact of utilization of intravenous immunoglobulin (IVIG) during the process in terms of performance.

Conclusively, the novel application is a fully automated process in a closed fluidic system which is able to deliver ready to use stem cell grafts by giving a flexible process end time with minimal user interaction. As the aim is to receive both CE and GMP labels for the system, the important next steps will be to submit the relevant documentation to a European notified body.